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| ARCHIVE | Friday, July 26th - Adult Physiology and Metabolism |
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June 2024
May 2024 April 2024 March 2024 February 2024 January 2024 December 2023 November 2023 October 2023 September 2023 August 2023 July 2023 June 2023 May 2023 April 2023 March 2023 February 2023 January 2023 December 2022 November 2022 October 2022 September 2022 August 2022 December 2021 December 2020 December 2019 December 2018 | Evans, A., Ferrer, A. J., Fradkov, E., Shomar, J. W., Forer, J., Klein, M. (2023). Temperature sensitivity and temperature response across development in the Drosophila larva. Frontiers in molecular neuroscience. 16:1275469 PubMed ID: 37965044
Summary: The surrounding thermal environment is highly important for the survival and fitness of animals, and as a result most exhibit behavioral and neural responses to temperature changes. Signals generated by thermosensory neurons were studied in Drosophila larvae, and also the physical and sensory effects of temperature variation on locomotion and navigation were studied. In particular how sensory neuronal and behavioral responses to temperature variation both change across the development of the larva were characterized. Looking at a wide range of non-nociceptive isotropic thermal environments, this study characterize the dependence of speed, turning rate, and other behavioral components on temperature, distinguishing the physical effects of temperature from behavior changes based on sensory processing. The strategies larvae use to modulate individual behavioral components to produce directed navigation along thermal gradients, and how these strategies change during physical development were characterized. Simulations based on modified random walks show where thermotaxis in each developmental stage fits into the larger context of possible navigation strategies. Cool sensing neurons were studied in the larva's dorsal organ ganglion, characterizing neural response to sine-wave modulation of temperature while performing single-cell-resolution 3D imaging. The sensitivity of these neurons, which produce signals in response to extremely small temperature changes, was characterized. Combining thermotaxis results with neurophysiology data across development, sensitivity to temperature change was observed as low as a few thousandths of a °C per second, or a few hundredths of a °C in absolute temperature change. | Kim, N., Ahn, Y., Ko, K., Kim, B., Han, K., Suh, H. J., Jung, J., Hong, K. B. (2023). Yeast Hydrolysate Inhibits Lipid Accumulation via Regulation of Lipid Accumulation-Related Genes in a Drosophila Model of High-Sugar Diet-Induced Obesity. Int J Mol Sci, 24(22) PubMed ID: 38003491
Summary: The increasing frequency of processed food consumption has led to the higher ingestion of sugar, increasing the risk of chronic diseases, such as obesity. Yeast hydrolysates (YHs) inhibit body fat accumulation. However, the action mechanism of YH in relation to high-sugar diet-induced obesity is still unclear. Therefore, this study aimed to evaluate the biological effects of YH on lipid accumulation and verify behavioral changes and carbohydrate metabolic gene regulation in high-sugar diet-fed fruit flies. Adult male flies (Drosophila melanogaster; 2-5 days old) were exposed to 20% sucrose for obesity induction. In high-sugar-fed Drosophila, the effect of YH was compared with that of yeast extract. The effects of YH on body conditions and lipid droplet size were quantified and analyzed. Behavioral factors were evaluated by analyzing circadian rhythm patterns and neurotransmitter content, and a molecular approach was used to analyze the expression of metabolism-related genes. Dietary supplementation with YH did not reduce total sugar content, but significantly decreased the triglyceride (TG) levels in Drosophila. A behavioral analysis showed that the total number of night-time activities increased significantly with YH treatment in a dose-dependent manner. In addition, YH effectively regulated the gene expression of insulin-like peptides related to carbohydrate metabolism as well as genes related to lipogenesis. The TG content was significantly reduced at a YH concentration of 0.5%, confirming that the active compound in YH effectively suppresses fat accumulation. These findings support that YH is a potential anti-obesity food material via regulating carbohydrate metabolism in Drosophila. |
| Ghosn, Z. A., Sparks, K. M., Spaulding, J. L., Vutukuri, S., Ahmed, M. J. J., VanBerkum, M. F. A. (2024). Divalent metal content in diet affects severity of manganese toxicity in Drosophila. Biol Open, 13(1) PubMed ID: 38117005
Summary: Dysregulation of manganese (Mn) homeostasis is a contributing factor in many neuro-degenerative diseases. Adult Drosophila are sensitive to excessive levels of dietary Mn, dying relatively early, and exhibiting biochemical and mobility changes reminiscent of Parkinsonian conditions. To further study Mn homeostasis in Drosophila, this study sought to test lower levels of dietary Mn (5 mM), and a striking difference in Canton-S adult survivorship on different food was noted. On a cornmeal diet, Mn-treated flies live only about half as long as untreated siblings. Yet, with the same Mn concentration in a molasses diet, adults survive about 80% as long as untreated siblings, and adults raised on a sucrose-yeast diet are completely insensitive to this low dose of dietary Mn. By manipulating metal ion content in the cornmeal diet, and measuring the metal content in each diet, the difference in lifespan were traced to the levels of calcium and magnesium in the food, suggesting that these ions are involved in Mn uptake and/or use. Based on these findings, it is recommended that the total dietary load of metal ions be considered when assessing Mn toxicity. | Bordet, G., Bamgbose, G., Tulin, A. V. (2023). Poly(ADP-ribosyl)ating enzymes coordinate changes in the expression of metabolic genes with developmental progression. Sci Rep, 13(1):20320 PubMed ID: 37985852
Summary: Metabolism, known to be temporally regulated to meet evolving energy demands, plays a crucial role in shaping developmental pace. Recent studies have demonstrated that two key proteins PARP1 and PARG play a regulatory role in the transcription of both morphogenic and metabolic genes. Intriguingly, in Drosophila, the depletion of PARP1 or PARG proteins causes a developmental arrest before pupation, resulting in individuals unable to complete their development. This phenotype highlights the critical involvement of poly(ADP-ribosyl)ating enzymes in regulating the metamorphic process. This study provides compelling evidence that these enzymes intricately coordinate transcriptional changes in both developmental and metabolic pathways during metamorphosis. Specifically, they promote the expression of genes crucial for pupation, while simultaneously negatively regulating the expression of metabolic genes before the transition to the pupal stage. Additionally, these enzymes suppress the expression of genes that are no longer required during this transformative period. These findings shed light on the intricate interplay between poly(ADP-ribosyl)ating enzymes, developmental processes, and metabolic regulation before metamorphosis and highlight a new role of poly(ADP-ribosyl)ating enzymes in the global regulation of transcription. |
| Colombo, M., Grauso, L., Lanzotti, V., Incerti, G., Adamo, A., Storlazzi, A., Gigliotti, S., Mazzoleni, S. (2023). Self-DNA Inhibition in Drosophila melanogaster Development: Metabolomic Evidence of the Molecular Determinants. Biology, 12(11) PubMed ID: 37997977
Summary: This study investigated the effects of dietary delivered self-DNA in the model insect Drosophila melanogaster. Self-DNA administration resulted in low but significant lethality in Drosophila larvae and considerably extended the fly developmental time. This was characterized by the abnormal persistence of the larvae in the L2 and L3 stages, which largely accounted for the average 72 h delay observed in pupariation, as compared to controls. In addition, self-DNA exposure affected adult reproduction by markedly reducing both female fecundity and fertility, further demonstrating its impact on Drosophila developmental processes. The effects on the metabolites of D. melanogaster larvae after exposure to self-DNA were studied by NMR, LC-MS, and molecular networking. The results showed that self-DNA feeding reduces the amounts of all metabolites, particularly amino acids and N-acyl amino acids, which are known to act as lipid signal mediators. An increasing amount of phloroglucinol was found after self-DNA exposure and correlated to developmental delay and egg-laying suppression. Pidolate, a known intermediate in the γ-glutamyl cycle, also increased after exposure to self-DNA and correlated to the block of insect oogenesis. | Xu, B., Hwangbo, D. S., Saurabh, S., Rosensweig, C., Allada, R., Kath, W. L., Braun, R. (2023). Temperature-driven coordination of circadian transcriptome regulation. bioRxiv, PubMed ID: 37961403
Summary: The circadian rhythm is an evolutionarily-conserved molecular oscillator that enables species to anticipate rhythmic changes in their environment. At a molecular level, the core clock genes induce a circadian oscillation in thousands of genes in a tissue-specific manner, orchestrating myriad biological processes. While studies have investigated how the core clock circuit responds to environmental perturbations such as temperature, the downstream effects of such perturbations on circadian regulation remain poorly understood. By analyzing bulk-RNA sequencing of Drosophila fat bodies harvested from flies subjected to different environmental conditions, a highly condition-specific circadian transcriptome was characterized. Further employing a reference-based gene regulatory network (Reactome), evidence was found of increased gene-gene coordination at low temperatures and synchronization of rhythmic genes that are network neighbors. The results point to the mechanisms by which the circadian clock mediates the fly's response to seasonal changes in temperature. |
Thursday, July 25th - Chromatin |
| Chavan, A., Isenhart, R., Nguyen, S. C., Kotb, N., Harke, J., Sintsova, A., Ulukaya, G., Uliana, F., Ashiono, C., Kutay, U., Pegoraro, G., Rangan, P., Joyce, E. F., Jagannathan, M. (2023). A nuclear architecture screen in Drosophila identifies Stonewall as a link between chromatin position at the nuclear periphery and germline stem cell fate. bioRxiv, PubMed ID: 38014085
Summary: The association of genomic loci to the nuclear periphery is proposed to facilitate cell-type specific gene repression and influence cell fate decisions. However, the interplay between gene position and expression remains incompletely understood, in part because the proteins that position genomic loci at the nuclear periphery remain unidentified. This study used an Oligopaint-based HiDRO screen targeting ~1000 genes to discover novel regulators of nuclear architecture in Drosophila cells. The heterochromatin-associated protein, Stonewall (Stwl), was identified as a factor promoting perinuclear chromatin positioning. In female germline stem cells (GSCs), Stwl binds and positions chromatin loci, including GSC differentiation genes, at the nuclear periphery. Strikingly, Stwl-dependent perinuclear positioning is associated with transcriptional repression, highlighting a likely mechanism for Stwl's known role in GSC maintenance and ovary homeostasis. Thus, this study identifies perinuclear anchors in Drosophila and demonstrates the importance of gene repression at the nuclear periphery for cell fate. | Niederhuber, M. J., Leatham-Jensen, M., McKay, D. J. (2023). The SWI/SNF nucleosome remodeler constrains enhancer activity during Drosophila wing development. Genetics, PubMed ID: 37949841
Summary: It is currently unclear how the short stretches of DNA that are individually unmask by transcription factor binding yield the kilobase-sized accessible regions characteristic of active enhancers. A genetic screen was performed to investigate the role of nucleosome remodelers in control of dynamic enhancer activity. The Drosophila SWI/SNF complex, BAP, was shown to be required for repression of a temporally dynamic enhancer, brdisc. Contrary to expectations, it was found that the BAP-specific subunit Osa is dispensable for mediating changes in chromatin accessibility between early and late stages of wing development. Instead, it was found that Osa is required to constrain the levels of brdisc activity when the enhancer is normally active. Genome-wide profiling reveals that Osa directly binds brdisc as well as thousands of other developmentally dynamic regulatory sites. Transgenic reporter analyses demonstrate that Osa is required for activation and for constraint of different sets of target enhancers in the same cells. Moreover, Osa loss results in hyperactivation of the Notch ligand Delta and development of ectopic sensory structures patterned by Notch signaling early in development. Together, these findings indicate that proper constraint of enhancer activity is necessary for regulation of dose-dependent developmental events. |
| Zhao, X., Yang, X., Lv, P., Xu, Y., Wang, X., Zhao, Z., Du, J. (2024). Polycomb regulates circadian rhythms in Drosophila in clock neurons. Life science alliance, 7(1) PubMed ID: 37914396
Summary: Circadian rhythms are essential physiological feature for most living organisms. Previous studies have shown that epigenetic regulation plays a crucial role. There is a knowledge gap in the chromatin state of some key clock neuron clusters. This study shows that circadian rhythm is affected by the epigenetic regulator Polycomb (Pc) within the Drosophila clock neurons. To investigate the molecular mechanisms underlying the roles of Pc in these clock neuron clusters, targeted DamID (TaDa) was used to identify genes significantly bound by Pc in the neurons marked by C929-Gal4 (including l-LNvs cluster), R6-Gal4 (including s-LNvs cluster), R18H11-Gal4 (including DN1 cluster), and DVpdf-Gal4, pdf-Gal80 (including LNds cluster). It shows that Pc binds to the genes involved in the circadian rhythm pathways, arguing a direct role for Pc in regulating circadian rhythms through specific clock genes. This study shows the identification of Pc targets in the clock neuron clusters, providing potential resource for understanding the regulatory mechanisms of circadian rhythms by the PcG complex. Thus, this study provided an example for epigenetic regulation of adult behavior. | Josserand, M., Rubanova, N., Stefanutti, M., Roumeliotis, S., Espenel, M., Marshall, O. J., Servant, N., Gervais, L., Bardin, A. J. (2023). Chromatin state transitions in the Drosophila intestinal lineage identify principles of cell-type specification. Dev Cell, 58(24):3048-3063. PubMed ID: 38056452
Summary: Tissue homeostasis relies on rewiring of stem cell transcriptional programs into those of differentiated cells. This study investigated changes in chromatin occurring in a bipotent adult stem cells. Combining mapping of chromatin-associated factors with statistical modeling, genome-wide transitions during differentiation were identified in the adult Drosophila intestinal stem cell (ISC) lineage. Active, stem-cell-enriched genes transition to a repressive heterochromatin protein-1-enriched state more prominently in enteroendocrine cells (EEs) than in enterocytes (ECs), in which the histone H1-enriched Black state is preeminent. In contrast, terminal differentiation genes associated with metabolic functions follow a common path from a repressive, primed, histone H1-enriched Black state in ISCs to active chromatin states in EE and EC cells. Furthermore, it was found that lineage priming has an important function in adult ISCs, and histone H1 was identfied as a mediator of this process. These data define underlying principles of chromatin changes during adult multipotent stem cell differentiation. |
| Zhimulev, I. F., Vatolina, T. Y., Pokholkova, G. V., Antonenko, O. V., Maltseva, M. V. (2023). Different Protein Groups Involved in Transcription Regulation in Development and Housekeeping Genes in Drosophila. Doklady Biochemistry and biophysics, 512(1):261-265 PubMed ID: 38093127
Summary: Antibodies to histone modifications and an insulator protein involved in the processes of transcription initiation and elongation are mapped in Drosophila polytene chromosomes. The CHRIZ protein (chromatin insulator) and H3K36me3 histone modification (RNA elongation) are detected only in the localization of housekeeping genes (interbands and gray bands of polytene chromosomes) and never in the regions of developmental genes (black bands and large puffs arising from them). Antibodies to H3S10P histone modification, which is associated with the initial elongation of the RNA strand during transcription, are found exclusively in small puffs, but not in housekeeping gene localization sites or large ecdysone-induced puffs, where housekeeping genes are localized. Antibodies to H4R3me2 histone modification (a co-repressor of the ecdysone receptor) are detected only in large ecdysone-induced puffs. | Lundkvist, M. J., Lizana, L., Schwartz, Y. B. (2023). Forecasting histone methylation by Polycomb complexes with minute-scale precision. Sci Adv, 9(51):eadj8198 PubMed ID: 38134278
Summary: Animals use the Polycomb system to epigenetically repress developmental genes. The repression requires trimethylation of lysine 27 of histone H3 (H3K27me3) by Polycomb Repressive Complex 2 (PRC2), but the dynamics of this process is poorly understood. To bridge the gap, a computational model was developed that forecasts H3K27 methylation in Drosophila with high temporal resolution and spatial accuracy of contemporary experimental techniques. Using this model, it was shown that pools of methylated H3K27 in dividing cells are defined by the effective concentration of PRC2 and the replication frequency. The allosteric stimulation by preexisting H3K27me3 makes PRC2 better in methylating developmental genes as opposed to indiscriminate methylation throughout the genome. Applied to Drosophila development, this model argues that, in this organism, the intergenerationally inherited H3K27me3 does not "survive" rapid cycles of embryonic chromatin replication and is unlikely to transmit the memory of epigenetic repression to the offspring. This model is adaptable to other organisms, including mice and humans. |
Wednesday, July 24th - RNAs and Transposons |
| Khanal, S., de Cruz, M., Strickland, B., Mansfield, K., Lai, E. C., Flynt, A. (2023). A tailed mirtron promotes longevity in Drosophila. Nucleic Acids Res, PubMed ID: 38048325
Summary: Thousands of atypical microRNAs (miRNAs) have been described in the genomes of animals; however, it is unclear if many of these non-canonical miRNAs can measurably influence phenotypes. Mirtrons are the largest class of non-canonical miRNAs that are produced from hairpins excised by splicing, which after debranching become substrates for Dicer and load into RISC. Most mirtrons require additional processing after splicing to remove 'tail' residues interposed between one of the host intron splice sites and base of the hairpin precursor structure. Despite most mirtrons requiring tail removal no function has been elucidated for a tailed species, indeed for all mirtrons identified function has only been assigned to a single species. This study examined miR-1017, a mirtron with a 3' tail, which is well expressed and conserved in Drosophila species. miR-1017 can extend lifespan when ectopically expressed in the neurons, which seems partly due to this miRNA targeting its host transcript, acetylcholine receptor Dα2. Unexpectedly it was found that not only did miR-1017 function in trans but also in cis by affecting splicing of Dα2. This suggests a mechanism for mirtron evolution where initial roles of structural elements in splicing lead to secondary acquisition of trans-regulatory function. | Shi, J., Xu, J., Ma, J., He, F. (2023). tRNA-derived small RNAs are embedded in the gene regulatory program instructing Drosophila metamorphosis. Genome research, 33(12):2119-2132 PubMed ID: 37973194
Summary: A class of noncoding RNAs, referred to as tsRNAs, is emerging with a potential to exert a new layer in gene regulation. These RNAs are breakdown products of tRNAs, either through active processing or passive cleavage or both. Since tRNAs are part of the general machinery for translation, their expression levels and activities are tightly controlled, raising the possibility that their breakdown products, tsRNAs, may provide a link between the overall translational status of a cell to specific changes in gene regulatory network. It was hypothesized that Drosophila pupation, being a special developmental stage during which there is a global limitation of nutrients, represents a system in which such a link may readily reveal itself. This study shows that specific tsRNAs indeed exhibit a dynamic accumulation upon entering the pupal stage. Experiments are described to characterize the mode of tsRNA action and, through the use of such gained knowledge, conduct a genome-wide analysis to assess the functions of dynamically expressed tsRNAs. The results show that the predicted target genes are highly enriched in biological processes specific to this stage of development including metamorphosis. It is further shown that tsRNA action is required for successful pupation, providing direct support to the hypothesis that tsRNAs accumulated during this stage are critical to the gene expression program at this stage of development. |
| Wharton, T. H., Marhabaie, M., Wharton, R. P. (2023). Significant roles in RNA-binding for the amino-terminal domains of Drosophila Pumilio and Nanos. bioRxiv, PubMed ID: 37961211
Summary: The Drosophila Pumilio (Pum) and Nanos (Nos) RNA-binding proteins govern abdominal segmentation in the early embryo, as well as a variety of other events during development. They bind together to a compound Nanos Response Element (NRE) present in thousands of maternal mRNAs in the ovary and embryo, including hunchback (hb) mRNA, thereby regulating poly-adenylation, translation, and stability. Many studies support a model in which mRNA recognition and effector recruitment are achieved by distinct regions of each protein. The well-ordered Pum and Nos RNA-binding domains (RBDs) are sufficient to specifically recognize NREs; the relatively larger low-complexity N-terminal domains (NTDs) of each protein have been thought to act by recruiting mRNA regulators. This study used yeast interaction assays to show that the NTDs also play a significant role in recognition of the NRE, acting via two mechanisms. First, the Pum and Nos NTDs interact in trans to promote assembly of the Pum/Nos/NRE ternary complex. Second, the Pum NTD acts via an unknown mechanism in cis, modifying base recognition by its RBD. These activities of the Pum NTD are important for its regulation of maternal hb mRNA in vivo. | Zhang, S., Wang, R., Zhu, X., Zhang, L., Liu, X., Sun, L. (2023). Characteristics and expression of lncRNA and transposable elements in Drosophila aneuploidy. iScience, 26(12):108494 PubMed ID: 38125016
Summary: Aneuploidy can globally affect the expression of the whole genome, which is detrimental to organisms. Dosage-sensitive regulators usually have multiple intermolecular interactions, and changes in their stoichiometry are responsible for the dysregulation of the regulatory network. Currently, studies on noncoding genes in aneuploidy are relatively rare. This study examined the characteristics and expression profiles of long noncoding RNAs (lncRNAs) and transposable elements (TEs) in aneuploid Drosophila. It was found that lncRNAs and TEs are affected by genomic imbalance and appear to be more sensitive to an inverse dosage effect than mRNAs. Several dosage-sensitive lncRNAs and TEs were detected for their expression patterns during embryogenesis, and their biological functions in the ovary and testes were investigated using tissue-specific RNAi. This study advances understanding of the noncoding sequences in imbalanced genomes and provides a novel perspective for the study of aneuploidy-related human diseases such as cancer. |
| Jagtap, P. K. A., Muller, M., Kiss, A. E., Thomae, A. W., Lapouge, K., Beck, M., Becker, P. B., Hennig, J. (2023). Structural basis of RNA-induced autoregulation of the DExH-type RNA helicase maleless. Mol Cell, 83(23):4318-4333.e4310 PubMed ID: 37989319
Summary: RNA unwinding by DExH-type helicases underlies most RNA metabolism and function. It remains unresolved if and how the basic unwinding reaction of helicases is regulated by auxiliary domains. This study explored the interplay between the RecA and auxiliary domains of the RNA helicase maleless (MLE) from Drosophila using structural and functional studies. MLE was shown to exist in a dsRNA-bound open conformation and that the auxiliary dsRBD2 domain aligns the substrate RNA with the accessible helicase tunnel. In an ATP-dependent manner, dsRBD2 associates with the helicase module, leading to tunnel closure around ssRNA. Furthermore, these structures provide a rationale for blunt-ended dsRNA unwinding and 3'-5' translocation by MLE. Structure-based MLE mutations confirm the functional relevance of this model for RNA unwinding. These findings contribute to understanding of the fundamental mechanics of auxiliary domains in DExH helicase MLE, which serves as a model for its human ortholog and potential therapeutic target, DHX9/RHA. | Crane, A. B., Jetti, S. K., Littleton, J. T. (2024). A stochastic RNA editing process targets a limited number of sites in individual Drosophila glutamatergic motoneurons. bioRxiv, PubMed ID: 38798345
Summary: RNA editing is a post-transcriptional source of protein diversity and occurs across the animal kingdom. Given the complete profile of mRNA targets and their editing rate in individual cells is unclear, this study analyzed single cell RNA transcriptomes from Drosophila larval tonic and phasic glutamatergic motoneuron subtypes to determine the most highly edited targets and identify cell-type specific editing. From approximately 15,000 genes encoded in the genome, 316 high confidence A-to-I canonical RNA edit sites were identified, with 102 causing missense amino acid changes in proteins regulating membrane excitability, synaptic transmission, and cellular function. Some sites showed 100% editing in single neurons as observed with mRNAs encoding mammalian AMPA receptors. However, most sites were edited at lower levels and generated variable expression of edited and unedited mRNAs within individual neurons. Together, these data provide insights into how the RNA editing landscape alters protein function to modulate the properties of two well-characterized neuronal populations in Drosophila . |
Tuesday, July 23rd - Synapse and Vesicles |
| Zhang, Y., Wang, T., Cai, Y., Cui, T., Kuah, M., Vicini, S., Wang, T. (2023). Role of alpha2delta-3 in regulating calcium channel localization at presynaptic active zones during homeostatic plasticity. Frontiers in molecular neuroscience, 16:1253669 PubMed ID: 38025261
Summary: The homeostatic modulation of synaptic transmission is an evolutionarily conserved mechanism that is critical for stabilizing the nervous system. At the Drosophila neuromuscular junction (NMJ), presynaptic homeostatic potentiation (PHP) compensates for impairments in postsynaptic glutamate receptors due to pharmacological blockade or genetic deletion. During PHP, there is an increase in presynaptic neurotransmitter release, counteracting postsynaptic changes and restoring excitation to baseline levels. Previous studies have shown that α2δ-3 (straightjacket), an auxiliary subunit of voltage-gated calcium channels (VGCCs), is essential for both the rapid induction and sustained expression of PHP at the Drosophila NMJ. However, the molecular mechanisms by which α2δ-3 regulates neurotransmitter release during PHP remain to be elucidated. This study utilized electrophysiological, confocal imaging, and super-resolution imaging approaches to explore how α2δ-3 regulates synaptic transmission during PHP. Our findings suggest that α2δ-3 governs PHP by controlling the localization of the calcium channel pore-forming α1 subunit at presynaptic release sites, or active zones. Moreover, the role of two structural domains within α2δ-3 in regulating neurotransmitter release and calcium channel localization was examined. The results highlight that these domains in α2δ-3 serve distinct functions in controlling synaptic transmission and presynaptic calcium channel abundance, at baseline in the absence of perturbations and during PHP. In summary, this research offers compelling evidence that α2δ-3 is an indispensable signaling component for controlling calcium channel trafficking and stabilization in homeostatic plasticity. | Kang, C. J., Guzmán-Clavel, L. E., Lei, K., Koo, M., To, S., Roche, J. P. (2023). The exocyst subunit Sec15 is critical for proper synaptic development and function at the Drosophila NMJ. Molecular and cellular neurosciences, 128:103914 PubMed ID: 38086519
Summary: The exocyst protein complex is important for targeted vesicle fusion in a variety of cell types, however, its function in neurons is still not entirely known. This study found that presynaptic knockdown (KD) of the exocyst component sec15 by transgenic RNAi expression caused a number of unexpected morphological and physiological defects in the synapse. These include the development of active zones (AZ) devoid of essential presynaptic proteins, an increase in the branching of the presynaptic arbor, the appearance of satellite boutons, and a decrease in the amplitude of stimulated postsynaptic currents as well as a decrease in the frequency of spontaneous synaptic vesicle release. The release of extracellular vesicles from the presynaptic neuron was greatly diminished in the Sec15 KDs. These effects were mimicked by presynaptic knockdown of Rab11, a protein known to interact with the exocyst. sec15 RNAi expression caused an increase in phosphorylated Mothers against decapentaplegic (pMad) in the presynaptic terminal, an indication of enhanced bone morphogenic protein (BMP) signaling. Some morphological phenotypes caused by Sec15 knockdown were reduced by attenuation of BMP signaling through knockdown of wishful thinking (Wit), while other phenotypes were unaffected. Individual knockdown of multiple proteins of the exocyst complex also displayed a morphological phenotype similar to Sec15 KD. It is concluded that Sec15, functioning as part of the exocyst complex, is critically important for proper formation and function of neuronal synapses. A model is proposed in which Sec15 is involved in the trafficking of vesicles from the recycling endosome to the cell membrane as well as possibly trafficking extracellular vesicles for presynaptic release and these processes are necessary for the correct structure and function of the synapse. |
| DePew, A. T., Bruckner, J. J., O'Connor-Giles, K. M., Mosca, T. J. (2023). Neuronal LRP4 directs the development, maturation, and cytoskeletal organization of peripheral synapses. bioRxiv, PubMed ID: 37961323
Summary: Synapse development requires multiple signaling pathways to accomplish the myriad of steps needed to ensure a successful connection. Transmembrane receptors on the cell surface are optimally positioned to facilitate communication between the synapse and the rest of the neuron and often function as synaptic organizers to synchronize downstream signaling events. One such organizer, the LDL receptor-related protein LRP4, is a cell surface receptor most well-studied postsynaptically at mammalian neuromuscular junctions. Recent work, however, has identified emerging roles for LRP4 as a presynaptic molecule, but how LRP4 acts as a presynaptic organizer, what roles LRP4 plays in organizing presynaptic biology, and the downstream mechanisms of LRP4 are not well understood. This study shows that LRP4 functions presynaptically at Drosophila neuromuscular synapses, acting in motor neurons to instruct multiple aspects of pre- and postsynaptic development. Loss of presynaptic LRP4 results in a range of developmental defects, impairing active zone organization, synapse growth, physiological function, microtubule organization, synaptic ultrastructure, and synapse maturation. It was further demonstrated that LRP4 promotes most aspects of presynaptic development via a downstream SR-protein kinase, SRPK79D. SRPK79D overexpression suppresses synaptic defects associated with loss of lrp4. These data demonstrate a function for LRP4 as a peripheral synaptic organizer acting presynaptically, highlight a downstream mechanism conserved with its CNS function, and indicate previously unappreciated roles for LRP4 in cytoskeletal organization, synapse maturation, and active zone organization, underscoring its developmental importance. | Waller, T. J., Collins, C. A. (2023). Opposing roles of Fos, Raw, and SARM1 in the regulation of axonal degeneration and synaptic structure. Frontiers in cellular neuroscience, 17:1283995 PubMed ID: 38099151
Summary: The degeneration of injured axons is driven by conserved molecules, including the sterile armadillo TIR domain-containing protein SARM1, the cJun N-terminal kinase JNK, and regulators of these proteins. These molecules are also implicated in the regulation of synapse development though the mechanistic relationship of their functions in degeneration vs. development is poorly understood. This study uncovered disparate functional relationships between SARM1 and the transmembrane protein Raw in the regulation of Wallerian degeneration and synaptic growth in motoneurons of Drosophila melanogaster. Genetic data suggest that Raw antagonizes the downstream output MAP kinase signaling mediated by Drosophila SARM1 (dSarm). This relationship is revealed by dramatic synaptic overgrowth phenotypes at the larval neuromuscular junction when motoneurons are depleted for Raw or overexpress dSarm. While Raw antagonizes the downstream output of dSarm to regulate synaptic growth, it shows an opposite functional relationship with dSarm for axonal degeneration. Loss of Raw leads to decreased levels of dSarm in axons and delayed axonal degeneration that is rescued by overexpression of dSarm, supporting a model that Raw promotes the activation of dSarm in axons. However, inhibiting Fos also decreases dSarm levels in axons but has the opposite outcome of enabling Wallerian degeneration. The combined genetic data suggest that Raw, dSarm, and Fos influence each other's functions through multiple points of regulation to control the structure of synaptic terminals and the resilience of axons to degeneration. |
| Ermanoska, B., Rodal, A. A. (2023). Non-muscle myosin II regulates presynaptic actin assemblies and neuronal mechanobiology. bioRxiv, PubMed ID: 38014140
Summary: Neuromuscular junctions (NMJs) are evolutionarily ancient, specialized contacts between neurons and muscles. Axons and NMJs must endure mechanical strain through a lifetime of muscle contraction, making them vulnerable to aging and neurodegenerative conditions. However, cellular strategies for mitigating this mechanical stress remain unknown. In this study, Drosophila larval NMJs were used to investigate the role of actin and myosin (actomyosin)-mediated contractility in generating and responding to cellular forces at the neuron-muscle interface. A new long-lived, low-turnover presynaptic actin core traversing the NMJ, which partly co-localizes with non-muscle myosin II (NMII). Neuronal RNAi of NMII induced disorganization of this core, suggesting that this structure might have contractile properties. Interestingly, neuronal RNAi of NMII also decreased NMII levels in the postsynaptic muscle proximal to neurons, suggesting that neuronal actomyosin rearrangements propagate their effects transsynaptically. Reduced Integrin levels were observed upon NMII knockdown, indicating that neuronal actomyosin disruption triggers rearrangements of Integrin-mediated connections between neurons and surrounding muscle tissue. In summary, this study identifies a previously uncharacterized presynaptic actomyosin subpopulation that upholds the neuronal mechanical continuum, transmits signals to adjacent muscle tissue, and collaborates with Integrin receptors to govern the mechanobiology of the neuromuscular junction. | Tsarouhas, V., Liu, D., Tsikala, G., Engstrom, Y., Strigini, M., Samakovlis, C. (2023). A surfactant lipid layer of endosomal membranes facilitates airway gas filling in Drosophila.. Curr Biol, 33(23):5132-5146. PubMed ID: 37992718
Summary: The mechanisms underlying the construction of an air-liquid interface in respiratory organs remain elusive. This study used live imaging and genetic analysis to describe the morphogenetic events generating an extracellular lipid lining of the Drosophila airways required for their gas filing and animal survival. Sequential Rab39/Syx1A/Syt1-mediated secretion of lysosomal acid sphingomyelinase (Drosophila ASM [dASM]) and Rab11/Rab35/Syx1A/Rop-dependent exosomal secretion provides distinct components for lipid film assembly. Tracheal inactivation of Rab11 or Rab35 or loss of Rop results in intracellular accumulation of exosomal, multi-vesicular body (MVB)-derived vesicles. On the other hand, loss of dASM or Rab39 causes luminal bubble-like accumulations of exosomal membranes and liquid retention in the airways. Inactivation of the exosomal secretion in dASM mutants counteracts this phenotype, arguing that the exosomal secretion provides the lipid vesicles and that secreted lysosomal dASM organizes them into a continuous film. These results reveal the coordinated functions of extracellular vesicle and lysosomal secretions in generating a lipid layer crucial for airway gas filling and survival. |
Friday, July 19th - Larval and Adult Neural Structure, Development and Function |
| Ahmed, O. M., Crocker, A., Murthy, M. (2023). Transcriptional profiling of Drosophila male-specific P1 (pC1) neurons. bioRxiv, PubMed ID: 37986870
Summary: In Drosophila melanogaster, the P1 (pC1) cluster of male-specific neurons, consisting of 20 interneurons per hemibrain, both integrates sensory cues and drives or modulates behavioral programs such as courtship, in addition to contributing to a social arousal state. The behavioral function of these neurons is linked to the genes they express, which underpin their capacity for synaptic signaling, neuromodulation, and physiology. Yet, P1 (pC1) neurons have not been fully characterized at the transcriptome level. Moreover, it is unknown how the molecular landscape of P1 (pC1) neurons acutely changes after flies engage in social behaviors, where baseline P1 (pC1) neural activity is expected to increase. To address these two gaps, single cell-type RNA sequencing was used to profile and compare the transcriptomes of P1 (pC1) neurons harvested from socially paired versus solitary male flies. Compared to control transcriptome datasets, it was found that P1 (pC1) neurons are enriched in 2,665 genes, including those encoding receptors, neuropeptides, and cell-adhesion molecules (dprs/DIPs). Furthermore, courtship is characterized by changes in ~300 genes, including those previously implicated in regulating behavior (e.g. DopEcR, Octβ3R, Fife, kairos, radish). Finally, a suite of genes was identified that link conspecific courtship with the innate immune system. Together, these data serve as a molecular map for future studies of an important set of higher-order and sexually-dimorphic neurons. | Xiao, N., Xu, S., Li, Z. K., Tang, M., Mao, R., Yang, T., Ma, S. X., Wang, P. H., Li, M. T., Sunilkumar, A., Rouyer, F., Cao, L. H., Luo, D. G. (2023). A single photoreceptor splits perception and entrainment by cotransmission. Nature, 623(7987):562-570 PubMed ID: 37880372
Summary: Vision enables both image-forming perception, driven by a contrast-based pathway, and unconscious non-image-forming circadian photoentrainment, driven by an irradiance-based pathway. Although two distinct photoreceptor populations are specialized for each visual task, image-forming photoreceptors can additionally contribute to photoentrainment of the circadian clock in different species. However, it is unknown how the image-forming photoreceptor pathway can functionally implement the segregation of irradiance signals required for circadian photoentrainment from contrast signals required for image perception. This study reports that the Drosophila R8 photoreceptor separates image-forming and irradiance signals by co-transmitting two neurotransmitters, histamine and acetylcholine. This segregation is further established postsynaptically by histamine-receptor-expressing unicolumnar retinotopic neurons and acetylcholine-receptor-expressing multicolumnar integration neurons. The acetylcholine transmission from R8 photoreceptors is sustained by an autocrine negative feedback of the cotransmitted histamine during the light phase of light-dark cycles. At the behavioural level, elimination of histamine and acetylcholine transmission impairs R8-driven motion detection and circadian photoentrainment, respectively. Thus, a single type of photoreceptor can achieve the dichotomy of visual perception and circadian photoentrainment as early as the first visual synapses, revealing a simple yet robust mechanism to segregate and translate distinct sensory features into different animal behaviours. |
| Dillon, N. R., Manning, L., Hirono, K., Doe, C. Q. (2023). Seven-up acts in neuroblasts to specify adult central complex neuron identity and initiate neuroblast decommissioning. bioRxiv, PubMed ID: 37961302
Summary: An open question in neurobiology is how diverse neuron cell types are generated from a small number of neural stem cells. In the Drosophila larval central brain, there are eight bilateral Type 2 neuroblast (T2NB) lineages that express a suite of early temporal factors followed by a different set of late temporal factors and generate the majority of the central complex (CX) neurons. The early-to-late switch is triggered by the orphan nuclear hormone receptor Seven-up (Svp), yet little is known about this Svp-dependent switch in specifying CX neuron identities. This study shows (i) birthdate the CX neurons P-EN and P-FN (early and late, respectively); (ii) show that Svp is transiently expressed in all early T2NBs; and (iii) show that loss of Svp expands the population of early born P-EN neurons at the expense of late born P-FN neurons. Furthermore, in the absence of Svp, T2NBs fail decommissioning and abnormally extend their lineage into week-old adults. It is concludes that Svp is required to specify CX neuron identity, as well as to initiate T2NB decommissioning. | Dallmann, C. J., Agrawal, S., Cook, A., Brunton, B. W., Tuthill, J. C. (2023). Presynaptic inhibition selectively suppresses leg proprioception in behaving Drosophila. bioRxiv, PubMed ID: 37961558
Summary: The sense of proprioception is mediated by internal mechanosensory neurons that detect joint position and movement. To support a diverse range of functions, from stabilizing posture to coordinating movements, proprioceptive feedback to limb motor control circuits must be tuned in a context-dependent manner. How proprioceptive feedback signals are tuned to match behavioral demands remains poorly understood. Using calcium imaging in behaving Drosophila, this study found that the axons of position-encoding leg proprioceptors are active across behaviors, whereas the axons of movement-encoding leg proprioceptors are suppressed during walking and grooming. Using connectomics, a specific class of interneurons was identified that provide GABAergic presynaptic inhibition to the axons of movement-encoding proprioceptors. These interneurons are active during self-generated but not passive leg movements and receive input from descending neurons, suggesting they are driven by predictions of leg movement originating in the brain. Predictively suppressing expected proprioceptive feedback provides a mechanism to attenuate reflexes that would otherwise interfere with voluntary movement. |
| Tao, L., Wechsler, S. P., Bhandawat, V. (2023). Sensorimotor transformation underlying odor-modulated locomotion in walking Drosophila. Nat Commun, 14(1):6818 PubMed ID: 37884581
Summary: Most real-world behaviors - such as odor-guided locomotion - are performed with incomplete information. Activity in olfactory receptor neuron (ORN) classes provides information about odor identity but not the location of its source. This study investigated the sensorimotor transformation that relates ORN activation to locomotion changes in Drosophila by optogenetically activating different combinations of ORN classes and measuring the resulting changes in locomotion. Three features describe this sensorimotor transformation: First, locomotion depends on both the instantaneous firing frequency (f) and its change (df); the two together serve as a short-term memory that allows the fly to adapt its motor program to sensory context automatically. Second, the mapping between (f, df) and locomotor parameters such as speed or curvature is distinct for each pattern of activated ORNs. Finally, the sensorimotor mapping changes with time after odor exposure, allowing information integration over a longer timescale. | Sang, J., Dhakal, S., Shrestha, B., Nath, D. K., Kim, Y., Ganguly, A., Montell, C., Lee, Y. (2023). A single pair of pharyngeal neurons functions as a commander to reject high salt in Drosophila melanogaster. bioRxiv, PubMed ID: 37904986
Summary: Salt is a crucial for survival, while excessive NaCl can be detrimental. In the fruit fly, Drosophila melanogaster, an internal taste organ, the pharynx, is a critical gatekeeper impacting the decision to accept or reject a food. Currently, understanding of the mechanism through which pharyngeal gustatory receptor neurons (GRNs) sense high salt are rudimentary. This study found that a member of the ionotropic receptor family, IR60b, is exclusively expressed in a pair of GRNs activated by high salt. Using a two-way choice assay (DrosoX) to measure ingestion, it was demonstrated that IR60b and two coreceptors IR25a and IR76b, are required to prevent high salt consumption. Mutants lacking external taste organs but retaining the pharynx exhibit much higher salt avoidance than flies with all taste organs but missing the three IRs. These findings highlight the critical role for IRs in a pair of pharyngeal GRNs to control ingestion of high salt. |
Thursday, July 18th - Stress |
| Santos, M. A., Antunes, M. A., Grandela, A., Carromeu-Santos, A., Quina, A. S., Santos, M., Matos, M., Simoes, P. (2023). Heat-induced female biased sex ratio during development is not mitigated after prolonged thermal selection. BMC ecology and evolution, 23(1):64 PubMed ID: 37919666
Summary: The negative impacts of climate change on biodiversity are consistently increasing. Developmental stages are particularly sensitive in many ectotherms. Moreover, sex-specific differences in how organisms cope with thermal stress can produce biased sex ratios upon emergence, with potentially major impacts on population persistence. This is an issue that needs investigation, particularly testing whether thermal selection can alleviate sex ratio distortions in the long-term is a critical but neglected issue. This study reports an experiment analyzing the sex ratio patterns at different developmental temperatures in Drosophila subobscura populations subjected to long-term experimental evolution (~ 30 generations) under a warming environment. Exposure to high developmental temperatures consistently promotes sex ratio imbalance upon emergence, with a higher number of female than male offspring. Furthermore, it was found that thermal selection resulting from evolution in a warming environment did not alleviate such sex ratio distortions generated by heat stress. This study has demonstrated that heat stress during development can lead to clear sex ratio deviations upon emergence likely because of differential survival between sexes. In face of these findings, it is likely that sex ratio deviations of this sort occur in natural populations when facing environmental perturbation. The inability of many insects to avoid thermal shifts during their (more) sessile developmental stages makes this finding particularly troublesome for population subsistence in face of climate warming events. | Olufs, Z. P. G., Wassarman, D. A., Perouansky, M. (2023). Stress pathways induced by volatile anesthetics and failure of preconditioning in a mitochondrial Complex I mutant. Anesthesiology, PubMed ID: 38118175
Summary: Carriers of mutations in the mitochondrial electron transport chain (mETC) are at increased risk of anesthetic-induced neurotoxicity. To investigate the neurotoxicity mechanism, a Drosophila model of Leigh syndrome was used. Model flies carried a mutation in ND23 that encodes an mETC Complex I subunit. Why ND2360114 mutants become susceptible to lethal, oxygen-modulated neurotoxicity within 24 h of exposure to isoflurane but not sevoflurane was investigated. Transcriptomics and qRT-PCR were used to identify genes that are differentially expressed in mutants but not wild type fly heads at 30 min after exposure to high versus low toxicity conditions. The mutation had a greater effect on isoflurane- than sevoflurane-mediated changes in gene expression. Isoflurane and sevoflurane did not affect expression of heat shock protein (Hsp) genes (Hsp22, Hsp27, and Hsp68) in wild type flies, but isoflurane substantially increased expression of these genes in mutant flies. Furthermore, isoflurane and sevoflurane induced expression of oxidative (GstD1and GstD2) and xenobiotic (Cyp6a8 and Cyp6a14) stress genes to a similar extent in wild type flies, but the effect of isoflurane was largely reduced in ND2360114 flies. It is concluded that mutation of an mETC Complex I subunit generates differential effects of isoflurane and sevoflurane on gene expression that may underlie their differential effects on neurotoxicity. Additionally, the mutation produces resistance to preconditioning by stresses that protect the brain in other contexts. Therefore, Complex I activity modifies molecular and physiological effects of anesthetics in an anesthetic-specific manner. |
| Aguilera, J., Duan, J., Lee, S. M., Ray, M., Larschan, E. (2023). The CLAMP GA-binding transcription factor regulates heat stress-induced transcriptional repression by associating with 3D loop anchors. bioRxiv, PubMed ID: 37873306
Summary: In order to survive when exposed to heat heat stress (HS), organisms activate stress response genes and repress constitutive gene expression to prevent the accumulation of potentially toxic RNA and protein products. Although many studies have elucidated the mechanisms that drive HS-induced activation of stress response genes across species, little is known about repression mechanisms or how genes are targeted for activation versus repression context-specifically. The mechanisms of heat stress-regulated activation have been well-studied in Drosophila, in which the GA-binding transcription factor GAF is important for activating genes upon heat stress. A functionally distinct GA-binding transcription factor (TF) protein, CLAMP (Chromatin-linked adaptor for MSL complex proteins), is essential for repressing constitutive genes upon heat stress but not activation of the canonical heat stress pathway. HS induces loss of CLAMP-associated 3D chromatin loop anchors associated with different combinations of GA-binding TFs prior to HS if a gene becomes repressed versus activated. Overall, this study demonstrates that CLAMP promotes repression of constitutive genes upon HS, and repression and activation are associated with the loss of CLAMP-associated 3D chromatin loops bound by different combinations of GA-binding TFs. | Juul-Kristensen, T., Keller, J. G., Borg, K. N., Hansen, N. Y., Foldager, A., Ladegaard, R., Ho, Y. P., Loeschcke, V., Knudsen, B. R. (2023). Topoisomerase 1 Activity Is Reduced in Response to Thermal Stress in Fruit Flies and in Human HeLa Cells. Biosensors, 13(11) PubMed ID: 37998125
Summary: In the modern world with climate changes and increasing pollution, different types of stress are becoming an increasing challenge. Hence, the identification of reliable biomarkers of stress and accessible sensors to measure such biomarkers are attracting increasing attention. This study demonstrated that the activity, but not the expression, of the ubiquitous enzyme topoisomerase 1 (TOP1), as measured in crude cell extracts by the REEAD sensor system, is markedly reduced in response to thermal stress in both fruit flies (Drosophila melanogaster) and cultivated human cells. This effect was observed in response to both mild-to-moderate long-term heat stress and more severe short-term heat stress in D. melanogaster. In cultivated HeLa cells a reduced TOP1 activity was observed in response to both cold and heat stress. The reduced TOP1 activity appeared dependent on one or more cellular pathways since the activity of purified TOP1 was unaffected by the utilized stress temperatures. Successful quantitative measurement of TOP1 activity was demonstrated using an easily accessible chemiluminescence readout for REEAD pointing towards a sensor system suitable for point-of-care assessment of stress responses based on TOP1 as a biomarker. |
| Torre, M., Bukhari, H., Nithianandam, V., Zanella, C. A., Mata, D. A., Feany, M. B. (2023). A Drosophila model relevant to chemotherapy-related cognitive impairment. Sci Rep, 13(1):19290 PubMed ID: 37935827
Summary: Chemotherapy-related cognitive impairment (CRCI) is a common adverse effect of treatment and is characterized by deficits involving multiple cognitive domains including memory. Despite the significant morbidity of CRCI and the expected increase in cancer survivors over the coming decades, the pathophysiology of CRCI remains incompletely understood, highlighting the need for new model systems to study CRCI. Given the powerful array of genetic approaches and facile high throughput screening ability in Drosophila, the goal of this study was to validate a Drosophila model relevant to CRCI. The chemotherapeutic agents cisplatin, cyclophosphamide, and doxorubicin were administered to adult Drosophila. Neurologic deficits were observed with all tested chemotherapies, with doxorubicin and in particular cisplatin also resulting in memory deficits. Then histologic and immunohistochemical analysis of cisplatin-treated Drosophila tissue was performed, demonstrating neuropathologic evidence of increased neurodegeneration, DNA damage, and oxidative stress. Thus, the Drosophila model relevant to CRCI recapitulates clinical, radiologic, and histologic alterations reported in chemotherapy patients. The new Drosophila model can be used for mechanistic dissection of pathways contributing to CRCI (and chemotherapy-induced neurotoxicity more generally) and pharmacologic screens to identify disease-modifying therapies. | Glineburg, M. R., Yildirim, E., Gomez, N., Li, X., Pak, J., Altheim, C., Waksmacki, J., McInerney, G., Barmada, S. J., Todd, P. K. (2023). Stress granule formation helps to mitigate neurodegeneration. bioRxiv. PubMed ID: 37986813
Summary: Cellular stress pathways that inhibit translation initiation lead to transient formation of cytoplasmic RNA/protein complexes known as stress granules. Many of the proteins found within stress granules and the dynamics of stress granule formation and dissolution are implicated in neurodegenerative disease. Whether stress granule formation is protective or harmful in neurodegenerative conditions is not known. To address this, advantage was taken of the alphavirus protein nsP3, which selectively binds dimers of the central stress granule nucleator protein G3BP (rin in Drosophila) and markedly reduces stress granule formation without directly impacting the protein translational inhibitory pathways that trigger stress granule formation. In Drosophila and rodent neurons, reducing stress granule formation with nsP3 had modest impacts on lifespan even in the setting of serial stress pathway induction. In contrast, reducing stress granule formation in models of ataxia, amyotrophic lateral sclerosis and frontotemporal dementia largely exacerbated disease phenotypes. These data support a model whereby stress granules mitigate, rather than promote, neurodegenerative cascades. |
Wednesday, July 17th - RNA and Transposons |
| Huang, Y., Pang, Y., Xu, Y., Liu, L., Zhou, H. (2024). The identification of regulatory ceRNA network involved in Drosophila Toll immune responses. Dev Comp Immunol, 151:105105 PubMed ID: 38013113
Summary: Non-coding RNAs play important roles in the innate immunity of Drosophila, with various lncRNAs and miRNAs identified to maintain Drosophila innate immune homeostasis by regulating protein functions. However, it remains unclear whether interactions between lncRNAs and miRNAs give rise to a competing endogenous RNAs (ceRNA) network. In a previous study, it was observed the highest differential expression levels of lncRNA-CR11538, lncRNA-CR33942, and lncRNA-CR46018 in wild-type flies after Gram-positive bacterial infection, prompting an investigation of their role in the regulation of Drosophila Toll immune response through RNA-seq analysis. A comprehensive bioinformatics analysis revealed that lncRNA-CR11538, lncRNA-CR33942, and lncRNA-CR46018 are involved in defense mechanisms and stimulus response. Moreover, lncRNA-CR11538 and lncRNA-CR46018 can also participate in the metabolic recovery processes following Gram-positive bacterial infection. Subsequently, GSEA screening and RT-qPCR were employed to identify seven miRNAs (miR-957, miR-1015, miR-982, miR-993, miR-1007, miR-193, and miR-978) that may be regulated by these three lncRNAs. Furthermore, the potential target genes are predicted in the Toll signaling pathway for these miRNAs and their interaction with the three lncRNAs using TargetScan and miRanda software and preliminary verification. As a result, a potential ceRNA regulatory network was established for Toll immune responses in Drosophila, comprising three lncRNAs and seven miRNAs. This study provides evidence of a ceRNA regulatory network in Drosophila Toll immune responses and offers novel insights into understanding the regulatory networks involved in the innate immunity of other animals. | Palumbo, R. J., Yang, Y., Feigon, J., Hanes, S. D. (2024). Catalytic activity of the Bin3/MePCE methyltransferase domain is dispensable for 7SK snRNP function in Drosophila melanogaster. Genetics, 226(1) PubMed ID: 37982586
Summary: Methylphosphate Capping Enzyme (MePCE) monomethylates the gamma phosphate at the 5' end of the 7SK noncoding RNA, a modification thought to protect 7SK from degradation. 7SK serves as a scaffold for assembly of a snRNP complex that inhibits transcription by sequestering the positive elongation factor P-TEFb. While much is known about the biochemical activity of MePCE in vitro, little is known about its functions in vivo, or what roles-if any-there are for regions outside the conserved methyltransferase domain. This study investigated the role of Bin3, the Drosophila ortholog of MePCE, and its conserved functional domains in Drosophila development. bin3 mutant females had strongly reduced rates of egg-laying, which was rescued by genetic reduction of P-TEFb activity, suggesting that Bin3 promotes fecundity by repressing P-TEFb. bin3 mutants also exhibited neuromuscular defects, analogous to a patient with MePCE haploinsufficiency. These defects were also rescued by genetic reduction of P-TEFb activity, suggesting that Bin3 and MePCE have conserved roles in promoting neuromuscular function by repressing P-TEFb. Unexpectedly, it was found that a Bin3 catalytic mutant (Bin3Y795A) could still bind and stabilize 7SK and rescue all bin3 mutant phenotypes, indicating that Bin3 catalytic activity is dispensable for 7SK stability and snRNP function in vivo. Finally, a metazoan-specific motif (MSM) was found outside of the methyltransferase domain, and mutant flies were generated lacking this motif (Bin3ΔMSM). Bin3ΔMSM mutant flies exhibited some-but not all-bin3 mutant phenotypes, suggesting that the MSM is required for a 7SK-independent, tissue-specific function of Bin3. |
| Milyaeva, P. A., Kukushkina, I. V., Kim, A. I., Nefedova, L. N. (2023). Stress Induced Activation of LTR Retrotransposons in the Drosophila melanogaster. Genome. Life (Basel, Switzerland), 13(12) PubMed ID: 38137873
Summary: Retrotransposons with long terminal repeats (LTR retrotransposons) are widespread in all groups of eukaryotes and are often both the cause of new mutations and the source of new sequences. Apart from their high activity in generative and differentiation-stage tissues, LTR retrotransposons also become more active in response to different stressors. The precise causes of LTR retrotransposons' activation in response to stress, however, have not yet been thoroughly investigated. This study used RT-PCR to investigate the transcriptional profile of LTR retrotransposons and piRNA clusters in response to oxidative and chronic heat stresses. Oxford Nanopore sequencing was used to investigate the genomic environment of new insertions of the retrotransposons. Bioinformatics methods were used to find the stress-induced transcription factor binding sites in LTR retrotransposons. The transposition activity and transcription level of LTR retrotransposons in response to oxidative and chronic heat stress was studied and the contribution of various factors that can affect the increase in their expression under stress conditions was assessed: the state of the piRNA-interference system, the influence of the genomic environment on individual copies, and the presence of the stress-induced transcription factor binding sites in retrotransposon sequences. The main reason for the activation of LTR retrotransposons under stress conditions is the presence of transcription factor binding sites in their regulatory sequences, which are triggered in response to stress and are necessary for tissue regeneration processes. Stress-induced transposable element activation can function as a trigger mechanism, triggering multiple signal pathways and resulting in a polyvariant cell response. | Zhang, T., Xue, Y., Su, S., Altouma, V., Ho, K., Martindale, J. L., Lee, S. K., Shen, W., Park, A., Zhang, Y., De, S., Gorospe, M., Wang, W. (2023). RNA-binding protein Nocte regulates Drosophila development by promoting translation reinitiation on mRNAs with long upstream open reading frames. Nucleic Acids Res, PubMed ID: 38000373
Summary: RNA-binding proteins (RBPs) with intrinsically disordered regions (IDRs) are linked to multiple human disorders, but their mechanisms of action remain unclear. This study reports that one such protein, Nocte, is essential for Drosophila eye development by regulating a critical gene expression cascade at translational level. Knockout of nocte in flies leads to lethality, and its eye-specific depletion impairs eye size and morphology. Nocte preferentially enhances translation of mRNAs with long upstream open reading frames (uORFs). One of the key Nocte targets, glass mRNA, encodes a transcription factor critical for differentiation of photoreceptor neurons and accessory cells, and re-expression of Glass largely rescued the eye defects caused by Nocte depletion. Mechanistically, Nocte counteracts long uORF-mediated translational suppression by promoting translation reinitiation downstream of the uORF. Nocte interacts with translation factors eIF3 and Rack1 through its BAT2 domain, and a Nocte mutant lacking this domain fails to promote translation of glass mRNA. Notably, de novo mutations of human orthologs of Nocte have been detected in schizophrenia patients. These data suggest that Nocte family of proteins can promote translation reinitiation to overcome long uORFs-mediated translational suppression, and disruption of this function can lead to developmental defects and neurological disorders. |
| Hernandez, G., Garcia, A., Weingarten-Gabbay, S., Mishra, R. K., Hussain, T., Amiri, M., Moreno-Hagelsieb, G., Montiel-Davalos, A., Lasko, P., Sonenberg, N. (2023). Functional analysis of the AUG initiator codon context reveals novel conserved sequences that disfavor mRNA translation in eukaryotes. Nucleic Acids Res, PubMed ID: 38038264
Summary: mRNA translation is a fundamental process for life. Selection of the translation initiation site (TIS) is crucial, as it establishes the correct open reading frame for mRNA decoding. Studies in vertebrate mRNAs discovered that a purine at -3 and a G at +4 (where A of the AUG initiator codon is numbered + 1), promote TIS recognition. However, the TIS context in other eukaryotes has been poorly experimentally analyzed. This study analyzed in vitro the influence of the -3, -2, -1 and + 4 positions of the TIS context in rabbit, Drosophila, wheat, and yeast. It was observed that -3A conferred the best translational efficiency across these species. However, variability was found at the + 4 position for optimal translation. In addition, the Kozak motif that was defined from mammalian cells was only weakly predictive for wheat and essentially non-predictive for yeast. Eight conserved sequences were discovered that significantly disfavored translation. Due to the big differences in translational efficiency observed among weak TIS context sequences, a novel category was defined that was termed 'barren AUG context sequences (BACS)', which represent sequences disfavoring translation. Analysis of mRNA-ribosomal complexes structures provided insights into the function of BACS. The gene ontology of the BACS-containing mRNAs is presented. | van Lopik, J., Alizada, A., Trapotsi, M. A., Hannon, G. J., Bornelov, S., Nicholson, B.C. (2023). Unistrand piRNA clusters are an evolutionarily conserved mechanism to suppress endogenous retroviruses across the Drosophila genus. Nat Commun, 14(1):7337 PubMed ID: 37957172
Summary: The PIWI-interacting RNA (piRNA) pathway prevents endogenous genomic parasites, i.e. transposable elements, from damaging the genetic material of animal gonadal cells. Specific regions in the genome, called piRNA clusters, are thought to define each species' piRNA repertoire and therefore its capacity to recognize and silence specific transposon families. The unistrand cluster flamenco (flam) is essential in the somatic compartment of the Drosophila ovary to restrict Gypsy-family transposons from infecting the neighbouring germ cells. Disruption of flam results in transposon de-repression and sterility, yet it remains unknown whether this silencing mechanism is present more widely. This study systematically characterised 119 Drosophila species and identified five additional flam-like clusters separated by up to 45 million years of evolution. Small RNA-sequencing validated these as bona-fide unistrand piRNA clusters expressed in somatic cells of the ovary, where they selectively target transposons of the Gypsy family. Together, this study provides compelling evidence of a widely conserved transposon silencing mechanism that co-evolved with virus-like Gypsy-family transposons. |
Tuesday, July 16th - Stem Cells |
| Khanbabei, A., Segura, L., Petrossian, C., Lemus, A., Cano, I., Frazier, C., Halajyan, A., Ca, D., Loza-Coll, M. (2024). Experimental validation and characterization of putative targets of Escargot and STAT, two master regulators of the intestinal stem cells in Drosophila melanogaster. Dev Biol, 505:148-163 PubMed ID: 37952851
Summary: Many organs contain adult stem cells (ASCs) to replace cells due to damage, disease, or normal tissue turnover. ASCs can divide asymmetrically, giving rise to a new copy of themselves (self-renewal) and a sister that commits to a specific cell type (differentiation). Decades of research have led to the identification of pleiotropic genes whose loss or gain of function affect diverse aspects of normal ASC biology. Genome-wide screens of these so-called genetic "master regulator" (MR) genes, have pointed to hundreds of putative targets that could serve as their downstream effectors. This study experimentally validate and characterize the regulation of several putative targets of Escargot (Esg) and the Signal Transducer and Activator of Transcription (Stat92E, a.k.a. STAT), two known MRs in Drosophila intestinal stem cells (ISCs). The results indicate that regardless of bioinformatic predictions, most experimentally validated targets show a profile of gene expression that is consistent with co-regulation by both Esg and STAT, fitting a rather limited set of co-regulatory modalities. A bioinformatic analysis of proximal regulatory sequences in specific subsets of co-regulated targets identified additional transcription factors that might cooperate with Esg and STAT in modulating their transcription. Lastly, in vivo manipulations of validated targets rarely phenocopied the effects of manipulating Esg and STAT, suggesting the existence of complex genetic interactions among downstream targets of these two MR genes during ISC homeostasis. | Banach-Latapy, A., Rincheval, V., Briand, D., Guenal, I., Speder, P. (2023). Differential adhesion during development establishes individual neural stem cell niches and shapes adult behaviour in Drosophila. PLoS Biol, 21(11):e3002352 PubMed ID: 37943883
Summary: Neural stem cells (NSCs) reside in a defined cellular microenvironment, the niche, which supports the generation and integration of newborn neurons. The mechanisms building a sophisticated niche structure around NSCs and their functional relevance for neurogenesis are yet to be understood. In the Drosophila larval brain, the cortex glia (CG) encase individual NSC lineages in membranous chambers, organising the stem cell population and newborn neurons into a stereotypic structure. It was first found that CG wrap around lineage-related cells regardless of their identity, showing that lineage information builds CG architecture. It was then discovered that a mechanism of temporally controlled differential adhesion using conserved complexes supports the individual encasing of NSC lineages. An intralineage adhesion through homophilic Neurexin-IV and Wrapper exists between NSC lineages and CG. Loss of Neuroglian results in NSC lineages clumped together and in an altered CG network, while loss of Neurexin-IV/Wrapper generates larger yet defined CG chamber grouping several lineages together. Axonal projections of newborn neurons are also altered in these conditions. Further, the loss of these 2 adhesion complexes specifically during development were linked to locomotor hyperactivity in the resulting adults. Altogether, these findings identify a belt of adhesions building a neurogenic niche at the scale of individual stem cell and provide the proof of concept that niche properties during development shape adult behaviour. |
| Russell, S. L., Castillo, J. R., Sullivan, W. T. (2023). Wolbachia endosymbionts manipulate the self-renewal and differentiation of germline stem cells to reinforce fertility of their fruit fly host. PLoS Biol, 21(10):e3002335 PubMed ID: 37874788
Summary: The alphaproteobacterium Wolbachia pipientis infects arthropod and nematode species worldwide, making it a key target for host biological control. Wolbachia-driven host reproductive manipulations, such as cytoplasmic incompatibility (CI), are credited for catapulting these intracellular bacteria to high frequencies in host populations. Positive, perhaps mutualistic, reproductive manipulations also increase infection frequencies, but are not well understood. This study identified molecular and cellular mechanisms by which Wolbachia influences the molecularly distinct processes of germline stem cell (GSC) self-renewal and differentiation. wMel infection rescues the fertility of flies lacking the translational regulator mei-P26 and is sufficient to sustain infertile homozygous mei-P26-knockdown stocks indefinitely. Cytology revealed that wMel mitigates the impact of mei-P26 loss through restoring proper pMad, Bam, Sxl, and Orb expression. In Oregon R files with wild-type fertility, wMel infection elevates lifetime egg hatch rates. Exploring these phenotypes through dual-RNAseq quantification of eukaryotic and bacterial transcripts revealed that wMel infection rescues and offsets many gene expression changes induced by mei-P26 loss at the mRNA level. Overall, this study shows that wMel infection beneficially reinforces host fertility at mRNA, protein, and phenotypic levels, and these mechanisms may promote the emergence of mutualism and the breakdown of host reproductive manipulations. | Nelson, J. O., Kumon, T., Yamashita, Y. M. (2023). rDNA magnification is a unique feature of germline stem cells. Proc Natl Acad Sci U S A, 120(47):e2314440120 PubMed ID: 37967216
Summary: Ribosomal DNA (rDNA) encodes ribosomal RNA and exists as tandem repeats of hundreds of copies in the eukaryotic genome to meet the high demand of ribosome biogenesis. Tandemly repeated DNA elements are inherently unstable; thus, mechanisms must exist to maintain rDNA copy number (CN), in particular in the germline that continues through generations. A phenomenon called rDNA magnification was discovered over 50 y ago in Drosophila as a process that recovers the rDNA CN on chromosomes that harbor minimal CN. Recent studies indicated that rDNA magnification is the mechanism to maintain rDNA CN under physiological conditions to counteract spontaneous CN loss that occurs during aging. A previous study that explored the mechanism of rDNA magnification implied that asymmetric division of germline stem cells (GSCs) may be particularly suited to achieve rDNA magnification. However, it remains elusive whether GSCs are the unique cell type that undergoes rDNA magnification or differentiating germ cells are also capable of magnification. This study provides empirical evidence that suggests that rDNA magnification operates uniquely in GSCs, but not in differentiating germ cells. Computer simulation is provided that suggests that rDNA magnification is only achievable through asymmetric GSC divisions. Despite known plasticity and transcriptomic similarity between GSCs and differentiating germ cells, GSCs' unique ability to divide asymmetrically serves a critical role of maintaining rDNA CN through generations, supporting germline immortality. |
| Pang, L. Y., DeLuca, S., Zhu, H., Urban, J. M., Spradling, A. C. (2023). Chromatin and gene expression changes during female Drosophila germline stem cell development illuminate the biology of highly potent stem cells. Elife, 12 PubMed ID: 37831064
Summary: Highly potent animal stem cells either self transposons renew or launch complex differentiation programs, using mechanisms that are only partly understood. Drosophila female germline stem cells (GSCs) perpetuate without change over evolutionary time and generate cystoblast daughters that develop into nurse cells and oocytes. Cystoblasts initiate differentiation by generating a transient syncytial state, the germline cyst, and by increasing pericentromeric H3K9me3 modification, actions likely to suppress transposable element activity. Relatively open GSC chromatin is further restricted by Polycomb repression of testis or somatic cell-expressed genes briefly active in early female germ cells. Subsequently, Neijre/CBP and Myc help upregulate growth and reprogram GSC metabolism by altering mitochondrial transmembrane transport, gluconeogenesis, and other processes. In all these respects GSC differentiation resembles development of the totipotent zygote. It is proposed that the totipotent stem cell state was shaped by the need to resist transposon activity over evolutionary timescales. | Ho, K. Y. L., An, K., Carr, R. L., Dvoskin, A. D., Ou, A. Y. J., Vogl, W., Tanentzapf, G. (2023). Maintenance of hematopoietic stem cell niche homeostasis requires gap junction-mediated calcium signaling. Proc Natl Acad Sci U S A, 120(45):e2303018120 PubMed ID: 37903259
Summary: Regulation of stem cells requires coordination of the cells that make up the stem cell niche. This study describes a mechanism that allows communication between niche cells to coordinate their activity and shape the signaling environment surrounding resident stem cells. Using the Drosophila hematopoietic organ, the lymph gland, this study showed that cells of the hematopoietic niche, the posterior signaling center (PSC), communicate using gap junctions (GJs) and form a signaling network. This network allows PSC cells to exchange Ca(2+) signals repetitively which regulate the hematopoietic niche. Disruption of Ca(2+) signaling in the PSC or the GJ-mediated network connecting niche cells causes dysregulation of the PSC and blood progenitor differentiation. Analysis of PSC-derived cell signaling shows that the Hedgehog pathway acts downstream of GJ-mediated Ca(2+) signaling to modulate the niche microenvironment. These data show that GJ-mediated communication between hematopoietic niche cells maintains their homeostasis and consequently controls blood progenitor behavior. |
Monday July 15th - Signaling |
| Troost, T., Seib, E., Airich, A., Vullings, N., Necakov, A., De Renzis, S., Klein, T. (2023). The meaning of ubiquitylation of the DSL ligand Delta for the development of Drosophila. BMC Biol, 21(1):260 PubMed ID: 37974242
Summary: Ubiquitylation (ubi) of the intracellular domain of the Notch ligand Delta (Dl) by the E3 ligases Neuralized (Neur) and Mindbomb1 (Mib1) on lysines (Ks) is thought to be essential for the its signalling activity. Nevertheless, it has been previously shown that DlK2R-HA, a Dl variant where all Ks in its intracellular domain (ICD) are replaced by the structurally similar arginine (R), still possess weak activity if over-expressed. This suggests that ubi is not absolutely required for Dl signalling. However, it is not known whether the residual activity of DlK2R-HA is an effect of over-expression and, if not, whether DlK2R can provide sufficient activity for the whole development of Drosophila. To clarify these issues, this study generated and analysed Dl(attP)-DlK2R-HA, a knock-in allele into the Dl locus. This allele reveals that the sole presence of one copy of Dl(attP)-DlK2R-HA can provide sufficient activity for completion of development. It further indicates that while ubi is required for the full activity of Dl in Mib1-dependent processes, it is not essential for Neur-controlled neural development. Three modes of Dl signalling were identified that are either dependent or independent of ubi. Importantly, all modes depend on the presence of the endocytic adapter Epsin. During activation of Dl, direct binding of Epsin appears not to be an essential requirement. In addition, this analysis further reveals that the Ks are required to tune down the cis-inhibitory interaction of Dl with Notch. These results indicate that Dl can activate the Notch pathway without ubi of its ICD. It signals via three modes. Ubi is specifically required for the Mib1-dependent processes and the adjustment of cis-inhibition. In contrast to Mib1, Neur can efficiently activate Dl without ubi. Neur probably acts as an endocytic co-adapter in addition to its role as E3 ligase. Endocytosis, regulated in a ubi-dependent or ubi-independent manner is required for signalling and also suppression of cis-inhibition. The findings clarify the role of ubi of the ligands during Notch signalling. | Gutorov, R., Katz, B., Peters, M., Minke, B. (2023). Membrane lipid modulations by methyl-β-cyclodextrin uncouple the Drosophila light-activated phospholipase C from TRP and TRPL channel gating. J Biol Chem, 300(1):105484 PubMed ID: 37992804
Summary: Sterols are hydrophobic molecules, known to cluster signaling membrane-proteins in lipid rafts, while methyl-β-cyclodextrin (MβCD) has been a major tool for modulating membrane-sterol content for studying its effect on membrane proteins, including the transient receptor potential (TRP) channels. The Drosophila light-sensitive TRP channels are activated downstream of a G-protein-coupled phospholipase Cβ (PLC) cascade. In phototransduction, PLC is an enzyme that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) generating diacylglycerol, inositol-tris-phosphate, and protons, leading to TRP and TRP-like (TRPL) channel openings. This study examined the effects of MβCD on Drosophila phototransduction using electrophysiology while fluorescently monitoring PIP2 hydrolysis, aiming to examine the effects of sterol modulation on PIP2 hydrolysis and the ensuing light-response in the native system. Incubation of photoreceptor cells with MβCD dramatically reduced the amplitude and kinetics of the TRP/TRPL-mediated light response. MβCD also suppressed PLC-dependent TRP/TRPL constitutive channel activity in the dark induced by mitochondrial uncouplers, but PLC-independent activation of the channels by linoleic acid was not affected. Furthermore, MβCD suppressed a constitutively active TRP mutant-channel, trpP365, suggesting that TRP channel activity is a target of MβCD action. Importantly, whole-cell voltage-clamp measurements from photoreceptors and simultaneously monitored PIP2-hydrolysis by translocation of fluorescently tagged Tubby protein domain, from the plasma membrane to the cytosol, revealed that MβCD virtually abolished the light response when having little effect on the light-activated PLC. Together, MβCD uncoupled TRP/TRPL channel gating from light-activated PLC and PIP2-hydrolysis suggesting the involvement of distinct nanoscopic lipid domains such as lipid rafts and PIP2 clusters in TRP/TRPL channel gating. |
| Strutt, H., Warrington, S., Madathil, A. C. K., Langenhan, T., Strutt, D. (2023). Molecular symmetry breaking in the Frizzled-dependent planar polarity pathway. Curr Biol, 33(24):5340-5354.e5346 PubMed ID: 37995695
Summary: The core planar polarity pathway consists of six proteins that form asymmetric intercellular complexes that segregate to opposite cell ends in developing tissues and specify polarized cell structures or behaviors. Within these complexes, the atypical cadherin Flamingo localizes on both sides of intercellular junctions, where it interacts homophilically in trans via its cadherin repeats, whereas the transmembrane proteins Frizzled and Strabismus localize to the opposite sides of apposing junctions. However, the molecular mechanisms underlying the formation of such asymmetric complexes are poorly understood. Using a novel tissue culture system, the minimum requirements were determined for asymmetric complex assembly in the absence of confounding feedback mechanisms. Complexes were shown to be intrinsically asymmetric and that an interaction of Frizzled and Flamingo in one cell with Flamingo in the neighboring cell is the key symmetry-breaking step. In contrast, Strabismus is unable to promote homophilic Flamingo trans binding and is only recruited into complexes once Frizzled has entered on the opposite side. This interaction with Strabismus requires intact intracellular loops of the seven-pass transmembrane domain of Flamingo. Once recruited, Strabismus stabilizes the intercellular complexes together with the three cytoplasmic core proteins. A model is proposed whereby Flamingo exists in a closed conformation and binding of Frizzled in one cell results in a conformational change that allows its cadherin repeats to interact with a Flamingo molecule in the neighboring cell. Flamingo in the adjacent cell then undergoes a further change in the seven-pass transmembrane region that promotes the recruitment of Strabismus. | Song, S., Cho, B., Weiner, A. T., Nissen, S. B., Ojeda Naharros, I., Sanchez Bosch, P., Suyama, K., Hu, Y., He, L., Svinkina, T., Udeshi, N. D., Carr, S. A., Perrimon, N., Axelrod, J. D. (2023). Protein phosphatase 1 regulates core PCP signaling. EMBO reports, 24(12):e56997 PubMed ID: 37975164
Summary: Planar cell polarity (PCP) signaling polarizes epithelial cells within the plane of an epithelium. Core PCP signaling components adopt asymmetric subcellular localizations within cells to both polarize and coordinate polarity between cells. Achieving subcellular asymmetry requires additional effectors, including some mediating post-translational modifications of core components. Identification of such proteins is challenging due to pleiotropy. This study used mass spectrometry-based proximity labeling proteomics to identify such regulators in the Drosophila wing. The catalytic subunit of protein phosphatase1, Pp1-87B, was identified, and it was shown to regulate core protein polarization. Pp1-87B interacts with the core protein Van Gogh and at least one serine/threonine kinase, Dco/CKIε, that is known to regulate PCP. Pp1-87B modulates Van Gogh subcellular localization and directs its dephosphorylation in vivo. PNUTS, a Pp1 regulatory subunit, also modulates PCP. While the direct substrate(s) of Pp1-87B in control of PCP is not known, these data support the model that cycling between phosphorylated and unphosphorylated forms of one or more core PCP components may regulate acquisition of asymmetry. Finally, this screen serves as a resource for identifying additional regulators of PCP signaling. |
| Wani, A. R., Chowdhury, B., Luong, J., Chaya, G. M., Patel, K., Isaacman-Beck, J., Shafer, O., Kayser, M. S., Syed, M. H. (2023). Stem cell-specific ecdysone signaling regulates the development and function of a Drosophila sleep homeostat. bioRxiv, PubMed ID: 37873323
Summary: Complex behaviors arise from neural circuits that are assembled from diverse cell types. Sleep is a conserved and essential behavior, yet little is known regarding how the nervous system generates neuron types of the sleep-wake circuit. This study focused on the specification of Drosophila sleep-promoting neurons-long-field tangential input neurons that project to the dorsal layers of the fan-shaped body neuropil in the central complex (CX). Lineage analysis and genetic birth dating were used to identify two bilateral Type II neural stem cells that generate these dorsal fan-shaped body (dFB) neurons. Adult dFB neurons express Ecdysone-induced protein E93, and loss of Ecdysone signaling or E93 in Type II NSCs results in the misspecification of the adult dFB neurons. Finally, it was shown that E93 knockdown in Type II NSCs affects adult sleep behavior. These results provide insight into how extrinsic hormonal signaling acts on NSCs to generate neuronal diversity required for adult sleep behavior. These findings suggest that some adult sleep disorders might derive from defects in stem cell-specific temporal neurodevelopmental programs. | Sanchez-Martinez, A., Martinez, A. and Whitworth, A. J. (2023). FBXO7/ntc and USP30 antagonistically set the ubiquitination threshold for basal mitophagy and provide a target for Pink1 phosphorylation in vivo. PLoS Biol 21(8): e3002244. PubMed ID: 37535686
Summary: Functional analyses of genes linked to heritable forms of Parkinson's disease (PD) have revealed fundamental insights into the biological processes underpinning pathogenic mechanisms. Mutations in PARK15/FBXO7 cause autosomal recessive PD and FBXO7 has been shown to regulate mitochondrial homeostasis. This study investigated the extent to which FBXO7 and its Drosophila orthologue, ntc, share functional homology and explored its role in mitophagy in vivo. ntc mutants partially phenocopy Pink1 and parkin mutants and ntc overexpression supresses parkin phenotypes. Furthermore, ntc can modulate basal mitophagy in a Pink1- and parkin-independent manner by promoting the ubiquitination of mitochondrial proteins, a mechanism that is opposed by the deubiquitinase USP30. This basal ubiquitination serves as the substrate for Pink1-mediated phosphorylation that triggers stress-induced mitophagy. It is proposed that FBXO7/ntc works in equilibrium with USP30 to provide a checkpoint for mitochondrial quality control in basal conditions in vivo and presents a new avenue for therapeutic approaches. |
Friday July 12th - Adult Physiology and Metabolism |
| Arch, M., Vidal, M., Fuentes, E., Abat, A. S., Cardona, P. J. (2023). The reproductive status determines tolerance and resistance to Mycobacterium marinum in Drosophila melanogaster. Evolution, medicine, and public health, 11(1):332-347 PubMed ID: 37868078
Summary: Sex and reproductive status of the host have a major impact on the immune response against infection. The aim of this study was to understand their impact on host tolerance or resistance in the systemic Mycobacterium marinum infection of Drosophila melanogaster.Host survival and bacillary load were measured at time of death, as well as expression by quantitative real-time polymerase chain reaction of immune genes (diptericin and drosomycin). This study also assessed the impact of metabolic and hormonal regulation in the protection against infection by measuring expression of upd3, impl2 and ecR. The data showed increased resistance in actively mating flies and in mated females, while reducing their tolerance to infection. Data suggests that Toll and immune deficiency (Imd) pathways determine tolerance and resistance, respectively, while higher basal levels of ecR favours the stimulation of the Imd pathway. A dual role has been found for upd3 expression, linked to increased/decreased mycobacterial load at the beginning and later in infection, respectively. Finally, impl2 expression has been related to increased resistance in non-actively mating males. These results allow further assessment on the differences between sexes and highlights the role of the reproductive status in D. melanogaster to face infections, demonstrating their importance to determine resistance and tolerance against M. marinum infection. | Hou, W. Q., Wen, D. T., Zhong, Q., Mo, L., Wang, S., Yin, X. Y., Ma, X. F. (2023). Physical exercise ameliorates age-related deterioration of skeletal muscle and mortality by activating Pten-related pathways in Drosophila on a high-salt diet. Faseb j, 37(12):e23304 PubMed ID: 37971426
Summary: The phosphatase and tensin congeners (Pten) gene affects cell growth, cell proliferation, and rearrangement of connections, and it is closely related to cellular senescence, but it remains unclear the role of muscle-Pten gene in exercise against age-related deterioration in skeletal muscle and mortality induced by a high-salt diet (HSD). In here, overexpression and knockdown of muscle Pten gene were constructed by building Mhc(GAL4) /Pten(UAS-overexpression) and Mhc(GAL4) /Pten(UAS-RNAi) system in flies, and flies were given exercise training and a HSD for 2 weeks. The results showed that muscle Pten knockdown significantly reduced the climbing speed, climbing endurance, GP(X) activity, and the expression of Pten, Sirt1, PGC-1α genes, and it significantly increased the expression of Akt and ROS level, and impaired myofibril and mitochondria of aged skeletal muscle. Pten knockdown prevented exercise from countering the HSD-induced age-related deterioration of skeletal muscle. Pten overexpression has the opposite effect on skeletal muscle aging when compared to it knockdown, and it promoted exercise against HSD-induced age-related deterioration of skeletal muscle. Pten overexpression significantly increased lifespan, but its knockdown significantly decreased lifespan of flies. Thus, current results confirmed that differential expression of muscle Pten gene played an important role in regulating skeletal muscle aging and lifespan, and it also affected the adaptability of aging skeletal muscle to physical exercise since it determined the activity of muscle Pten/Akt pathway and Pten/Sirt1/PGC-1α pathway. |
| Yan, H., Ding, M., Peng, T., Zhang, P., Tian, R., Zheng, L. (2023). Regular Exercise Modulates the dfoxo/dsrebp Pathway to Alleviate High-Fat-Diet-Induced Obesity and Cardiac Dysfunction in Drosophila. Int J Mol Sci, 24(21) PubMed ID: 37958546
Summary: Obesity is a prevalent metabolic disorder associated with various diseases, including cardiovascular conditions. While exercise is recognized as an effective approach for preventing and treating obesity, its underlying molecular mechanisms remain unclear. This study aimed to explore the impact of regular exercise on high-fat-diet-induced obesity and cardiac dysfunction in Drosophila, shedding light on its molecular mechanisms by identifying its regulation of the dfoxo and dsrebp signaling pathways. The findings demonstrated that a high-fat diet leads to weight gain, fat accumulation, reduced climbing performance, and elevated triglyceride levels in Drosophila. Additionally, cardiac microfilaments in these flies exhibited irregularities, breakages, and shortening. M-mode analysis revealed that high-fat-diet-fed Drosophila displayed increased heart rates, shortened cardiac cycles, decreased systolic intervals, heightened arrhythmia indices, reduced diastolic diameters, and diminished fractional shortening. Remarkably, regular exercise effectively ameliorated these adverse outcomes. Further analysis showed that regular exercise reduced fat synthesis, promoted lipolysis, and mitigated high-fat-diet-induced cardiac dysfunction in Drosophila. These results suggest that regular exercise may mitigate high-fat-diet-induced obesity and cardiac dysfunction in Drosophila by regulating the dfoxo and dsrebp signaling pathways, offering valuable insights into the mechanisms underlying the beneficial effects of exercise on obesity and cardiac dysfunction induced by a high-fat diet. | Bamgbose, G., Tulin, A. (2024). PARP-1 is a transcriptional rheostat of metabolic and bivalent genes during development. Life science alliance, 7(2) PubMed ID: 38012002
Summary: PARP-1 participates in various cellular processes, including gene regulation. In Drosophila, PARP-1 mutants undergo developmental arrest during larval-to-pupal transition. This study investigated PARP-1 binding and its transcriptional regulatory role at this stage. The findings revealed that PARP-1 binds and represses active metabolic genes, including glycolytic genes, whereas activating low-expression developmental genes, including a subset of "bivalent" genes in third-instar larvae. These bivalent promoters, characterized by dual enrichment of low H3K4me3 and high H3K27me3, a unimodal H3K4me1 enrichment at the transcription start site (conserved in C. elegans and zebrafish), H2Av depletion, and high accessibility, may persist throughout development. In PARP-1 mutant third-instar larvae, metabolic genes typically down-regulated during the larval-to-pupal transition in response to reduced energy needs were repressed by PARP-1. Simultaneously, developmental and bivalent genes typically active at this stage were activated by PARP-1. In addition, glucose and ATP levels were significantly reduced in PARP-1 mutants, suggesting an imbalance in metabolic regulation. It is proposed that PARP-1 is essential for maintaining the delicate balance between metabolic and developmental gene expression programs to ensure proper developmental progression. |
| Kang, P., Liu, P., Kim, J., Bolton, M., Kumar, A., Miao, T., Shimell, M., O'Connor, M. B., Powell-Coffman, J., Bai, H. (2023). Ptth regulates lifespan through innate immunity pathway in Drosophila. bioRxiv, PubMed ID: 37873203
Summary: The prothoracicotropic hormone (Ptth) is well-known for its important role in controlling insect developmental timing and body size by promoting the biosynthesis and release of ecdysone. However, the role of Ptth in adult physiology is largely unexplored. Thia study showws that Ptth null mutants (both males and females) show extended lifespan and healthspan, and exhibit increased resistance to oxidative stress. Transcriptomic analysis reveals that age-dependent upregulation of innate immunity pathway is attenuated by Ptth mutants. Intriguingly, it was found that Ptth regulates the innate immunity pathway, specifically in fly oenocytes, the homology of mammalian hepatocytes. It was further shown that oenocyte-specific overexpression of Relish shortens the lifespan, while oenocyte-specific downregulation of ecdysone signaling extends lifespan. Consistently, knocking down torso, the receptor of Ptth in the prothoracic gland also promotes longevity of the flies. Thus, these data reveal a novel function of the insect hormone Ptth in longevity regulation and innate immunity in adult Drosophila. | Yu, G., Liu, S., Yang, K., Wu, Q. (2023). Reproductive-dependent effects of B vitamin deficiency on lifespan and physiology. Frontiers in nutrition,. 10:1277715 PubMed ID: 37941770
Summary: B vitamins constitute essential micronutrients in animal organisms, executing crucial roles in numerous biological processes. B vitamin deficiency can result in severe health consequences, including the impairment of reproductive functions and increased susceptibility to age-related diseases. However, the understanding of how reproduction alters the requirements of each individual B vitamins for healthy aging and lifespan remains limited. In this study, utilizing Drosophila as a model organism, the substantial impacts of deficiencies in specific B vitamins on lifespan and diverse physiological functions were revealed, with the effects being significantly shaped by reproductive status. Notably, the dietary absence of VB(1), VB(3), VB(5), VB(6), or VB(7) significantly decreased the lifespan of wild-type females, yet demonstrated relatively little effect on ovoD1 infertile mutant females' lifespan. B vitamin deficiencies also resulted in distinct impacts on the reproduction, starvation tolerance and fat metabolism of wild-type females, though no apparent effects were observed in the infertile mutant females. Moreover, a deficiency in VB(1) reshaped the impacts of macronutrient intervention on the physiology and lifespan of fertile females in a reproductive-dependent manner. Overall, this study unravels that the reproductive status of females serves as a critical modulator of the lifespan and physiological alterations elicited by B-vitamin deficiencies. |
Thursday July 11th - Genes, Enzymes and Protein Expression. Evolution, Structure and Function |
| Varland, S., Silva, R. D., Kjosas, I., Faustino, A., Bogaert, A., Billmann, M., Boukhatmi, H., Kellen, B., Costanzo, M., Drazic, A., Osberg, C., Chan, K., Zhang, X., Tong, A. H. Y., Andreazza, S., Lee, J. J., Nedyalkova, L., Usaj, M., Whitworth, A. J., Andrews, B. J., Moffat, J., Myers, C. L., Gevaert, K., Boone, C., Martinho, R. G., Arnesen, T. (2023). N-terminal acetylation shields proteins from degradation and promotes age-dependent motility and longevity. Nat Commun, 14(1):6774 PubMed ID: 37891180
Summary: Most eukaryotic proteins are N-terminally acetylated, but the functional impact on a global scale has remained obscure. Using genome-wide CRISPR knockout screens in human cells, this study revealed a strong genetic dependency between a major N-terminal acetyltransferase and specific ubiquitin ligases. Biochemical analyses uncover that both the ubiquitin ligase complex UBR4-KCMF1 and the acetyltransferase NatC recognize proteins bearing an unacetylated N-terminal methionine followed by a hydrophobic residue. NatC KO-induced protein degradation and phenotypes are reversed by UBR knockdown, demonstrating the central cellular role of this interplay. Loss of Drosophila NatC is associated with male sterility, reduced longevity, and age-dependent loss of motility due to developmental muscle defects. Remarkably, muscle-specific overexpression of UbcE2M, one of the proteins targeted for NatC KO-mediated degradation, suppresses defects of NatC deletion. In conclusion, NatC-mediated N-terminal acetylation acts as a protective mechanism against protein degradation, which is relevant for increased longevity and motility. | Peebles, K. E., LaFever, K. S., Page-McCaw, P. S., Colon, S., Wang, D., Stricker, A. M., Ferrell, N., Bhave, G., Page-McCaw, A. (2023). Peroxidasin is required for full viability in development and for maintenance of tissue mechanics in adults. Matrix biology : journal of the International Society for Matrix Biology, PubMed ID: 38000777
Summary: Basement membranes are thin strong sheets of extracellular matrix. They provide mechanical and biochemical support to epithelia, muscles, nerves, and blood vessels, among other tissues. The mechanical properties of basement membranes are conferred in part by Collagen IV (Col4), an abundant protein of basement membranes that forms an extensive two-dimensional network through head-to-head and tail-to-tail interactions. After the Col4 network is assembled into a basement membrane, it is crosslinked by the matrix-resident enzyme Peroxidasin to form a large covalent polymer. Peroxidasin and Col4 crosslinking are highly conserved throughout the animal kingdom, indicating they are important, but homozygous mutant mice have mild phenotypes. To explore the role of Peroxidasin, mutants in Drosophila, including a new CRISPR-generated catalytic null were analyzed, and homozygotes were found to be mostly lethal with 13% viable escapers. Mouse mutants also show semi-lethality, with Mendelian analysis demonstrating ∼50% lethality and ∼50% escapers. Despite the strong mutations, the homozygous fly and mouse escapers had low but detectable levels of Col4 crosslinking, indicating the existence of inefficient alternative crosslinking mechanisms, probably responsible for the viable escapers. Fly mutant phenotypes are consistent with decreased basement membrane stiffness. Interestingly, it was found that even after basement membranes are assembled and crosslinked in wild-type animals, continuing Peroxidasin activity is required in adults to maintain tissue stiffness over time. These results suggest that Peroxidasin crosslinking may be more important than previously appreciated. |
| Markus, D., Pelletier, A., Boube, M., Port, F., Boutros, M., Payre, F., Obermayer, B., Zanet, J. (2023). The pleiotropic functions of Pri smORF peptides synchronize leg development regulators. PLoS Genet, 19(10):e1011004 PubMed ID: 37903161
Summary: The last decade witnesses the emergence of the abundant family of smORF peptides, encoded by small ORF (<100 codons), whose biological functions remain largely unexplored. Bioinformatic analyses here identify hundreds of putative smORF peptides expressed in Drosophila imaginal leg discs. Thanks to a functional screen in leg, smORF peptides involved in morphogenesis were found, including the pioneer smORF peptides Pri. Since its target Ubr3 was identified in the epidermis and pri was known to control leg development through poorly understood mechanisms, the role of Ubr3 in mediating pri function in leg was examined. pri was found to play several roles during leg development both in patterning and in cell survival. During larval stage, pri activates independently of Ubr3 tarsal transcriptional programs and Notch and EGFR signaling pathways, whereas at larval pupal transition, Pri peptides cooperate with Ubr3 to insure cell survival and leg morphogenesis. These results highlight Ubr3 dependent and independent functions of Pri peptides and their pleiotropy. Moreover, it was revealed that the smORF peptide family is a reservoir of overlooked developmental regulators, displaying distinct molecular functions and orchestrating leg development. | Bosch, J. A., Keith, N., Escobedo, F., Fisher, W. W., LaGraff, J. T., Rabasco, J., Wan, K. H., Weiszmann, R., Hu, Y., Kondo, S., Brown, J. B., Perrimon, N., Celniker, S. E. (2023). Molecular and functional characterization of the Drosophila melanogaster conserved smORFome. Cell Rep, 42(11):113311 PubMed ID: 37889754
Summary: Short polypeptides encoded by small open reading frames (smORFs) are ubiquitously found in eukaryotic genomes and are important regulators of physiology, development, and mitochondrial processes. This study focused on a subset of 298 smORFs that are evolutionarily conserved between Drosophila melanogaster and humans. Many of these smORFs are conserved broadly in the bilaterian lineage, and ∼182 are conserved in plants. This study observe remarkably heterogeneous spatial and temporal expression patterns of smORF transcripts-indicating wide-spread tissue-specific and stage-specific mitochondrial architectures. In addition, an analysis of annotated functional domains reveals a predicted enrichment of smORF polypeptides localizing to mitochondria. An embryonic ribosome profiling experiment was conducted and support was found for translation of 137 of these smORFs during embryogenesis. This study further embarked on functional characterization using CRISPR knockout/activation, RNAi knockdown, and cDNA overexpression, revealing diverse phenotypes. This study underscores the importance of identifying smORF function in disease and phenotypic diversity. |
| Guntur, A. R., Smith, J. E., Brahmandam, A., DeBauche, P., Cronmiller, C., Lundell, M. J. (2023). ZFH-2 is required for Drosophila ovarian follicle development and is expressed at the band/interband boundaries of polytene chromosomes. Dev Biol, 504:1-11 PubMed ID: 37666353
Summary: The transcription factor ZFH-2 has well-documented roles in Drosophila neurogenesis and other developmental processes. This study provides the first evidence that ZFH-2 has a role in oogenesis. ZFH-2 is expressed in the wild-type ovary and a loss of zfh-2 function produces a mutant ovary phenotype where egg chambers are reduced in number and fused. This study also showed that a loss of zfh-2 function can suppress a daughterless loss-of-function ovary phenotype suggesting a possible genetic relationship between these two genes in the ovary. It was also shown that ZFH-2 is located at the boundary between bands and interbands on polytene chromosomes and that at a subset of these sites ZFH-2 colocalizes with the insulator/promoter cofactor CP190. | Zhang, Q., Deng, K., Liu, M., Yang, S., Xu, W., Feng, T., Jie, M., Liu, Z., Sheng, X., Chen, H., Jiang, H. (2023). Phase separation of BuGZ regulates gut regeneration and aging through interaction with m(6)A regulators. Nat Commun, 14(1):6700 PubMed ID: 37872148
Summary: Exploring the role of phase separation in intracellular compartment formation is an active area of research. However, the associations of phase separation with intestinal stem cell (ISC)-dependent regeneration and aging remain unclear. This study demonstrates that BuGZ, a coacervating mitotic effector, shows age- and injury-associated condensation in Drosophila ISC nuclei during interphase. BuGZ condensation promotes ISC proliferation, affecting Drosophila gut repair and longevity. Moreover, m(6)A reader YT521-B acts as the transcriptional and functional downstream of BuGZ. The binding of YT521-B promotor or m(6)A writer Ime4/ Mettl14 to BuGZ controls its coacervation, indicating that the promotor may accelerate the phase transition of its binding transcription factor. Hence, it is proposed that phase separation and m(6)A regulators may be critical for ameliorating ISC-dependent gut regeneration and aging and requires further study. Summary: |
Wednesday, July 10th - Gonads |
| Burghardt, E., Rakijas, J., Tyagi, A., Majumder, P., Olson, B., McDonald, J. A. (2023). Transcriptome analysis reveals temporally regulated genetic networks during Drosophila border cell collective migration. BMC Genomics, 24(1):728 PubMed ID: 38041052
Summary: Collective cell migration underlies many essential processes, including sculpting organs during embryogenesis, wound healing in the adult, and metastasis of cancer cells. At mid-oogenesis, Drosophila border cells undergo collective migration. Border cells round up into a small group at the pre-migration stage, detach from the epithelium and undergo a dynamic and highly regulated migration at the mid-migration stage, and stop at the oocyte, their final destination, at the post-migration stage. While specific genes that promote cell signaling, polarization of the cluster, formation of protrusions, and cell-cell adhesion are known to regulate border cell migration, there may be additional genes that promote these distinct active phases of border cell migration. Therefore, this study sought to identify genes whose expression patterns changed during border cell migration. RNA-sequencing was performed on border cells isolated at pre-, mid-, and post-migration stages. It is reported that 1,729 transcripts, in nine co-expression gene clusters, are temporally and differentially expressed across the three migration stages. Gene ontology analyses and constructed protein-protein interaction networks identified genes expected to function in collective migration, such as regulators of the cytoskeleton, adhesion, and tissue morphogenesis, but also uncovered a notable enrichment of genes involved in immune signaling, ribosome biogenesis, and stress responses. Finally, the in vivo expression and function of a subset of identified genes in border cells was validated. Overall, these results identified differentially and temporally expressed genetic networks that may facilitate the efficient development and migration of border cells. The genes identified in this study represent a wealth of new candidates to investigate the molecular nature of dynamic collective cell migrations in developing tissues. | Chen, X., Qi, Y., Huang, Q., Sun, C., Zheng, Y., Ji, L., Shi, Y., Cheng, X., Li, Z., Zheng, S., Cao, Y., Gu, Z., Yu, J. (2023). Single-cell transcriptome characteristics of testicular terminal epithelium lineages during aging in the Drosophila. Aging Cell:e14057 PubMed ID: 38044573
Summary: Aging is a complex biological process leading to impaired functions, with a variety of hallmarks. In the testis of Drosophila, the terminal epithelium region is involved in spermatid release and maturation, while its functional diversity and regulatory mechanism remain poorly understood. Single-cell RNA-sequencing analysis (scRNA-seq) was performed to characterize the transcriptomes of terminal epithelium in Drosophila testes at 2-, 10 and 40-Days. Terminal epithelium populations were defined with Metallothionein A (MtnA) and subdivided into six novel sub-cell clusters (EP0-EP5), and a series of marker genes were identified based on their expressions. The data revealed the functional characteristics of terminal epithelium populations, such as tight junction, focal adhesion, bacterial invasion, oxidative stress, mitochondrial function, proteasome, apoptosis and metabolism. Interestingly, it was also found that disrupting genes for several relevant pathways in terminal epithelium led to male fertility disorders. Moreover, a series of age-biased genes and pseudotime trajectory mediated state-biased genes were also discovered during terminal epithelium aging. Differentially expressed genes during terminal epithelium aging were mainly participated in the regulation of several common signatures, e.g. mitochondria-related events, protein synthesis and degradation, and metabolic processes. The Drosophila divergence and selection in the functional constraints of age-biased genes during aging was also explored, revealing that age-biased genes in epithelial cells of 2 Days group evolved rapidly and were endowed with greater evolutionary advantages. scRNA-seq analysis revealed the diversity of testicular terminal epithelium populations, providing a gene target resource for further systematic research of their functions during aging. |
| He, Z., Fang, Y., Zhang, F., Liu, Y., Cheng, X., Wang, J., Li, D., Chen, D., Wu, F. (2023). Adenine nucleotide translocase 2 (Ant2) is required for individualization of spermatogenesis of Drosophila melanogaster. Insect Sci, PubMed ID: 38112480
Summary: Successful completion of spermatogenesis is crucial for the perpetuation of the species. In Drosophila, spermatid individualization, a process involving changes in mitochondrial structure and function is critical to produce functional mature sperm. Ant2, encoding a mitochondrial adenine nucleotide translocase, is highly expressed in male testes and plays a role in energy metabolism in the mitochondria. However, its molecular function remains unclear. This study identified an important role of Ant2 in spermatid individualization. In Ant2 knockdown testes, spermatid individualization complexes composed of F-actin cones exhibited a diffuse distribution, and mature sperms were absent in the seminal vesicle, thus leading to male sterility. The most striking effects in Ant2-knockdown spermatids were decrease in tubulin polyglycylation and disruption of proper mitochondria derivatives function. Excessive apoptotic cells were also observed in Ant2-knockdown testes. To further investigate the phenotype of Ant2 knockdown in testes at the molecular level, complementary transcriptome and proteome analyses were performed. At the mRNA level, 868 differentially expressed genes were identified, of which 229 genes were upregulated and 639 were downregulated induced via Ant2 knockdown. iTRAQ-labeling proteome analysis revealed 350 differentially expressed proteins, of which 117 proteins were upregulated and 233 were downregulated. The expression of glutathione transferase (GstD5, GstE5, GstE8, and GstD3), proteins involved in reproduction were significantly regulated at both the mRNA and protein levels. These results indicate that Ant2 is crucial for spermatid maturation by affecting mitochondrial morphogenesis. | Herriage, H. C., Calvi, B. R. (2024). Premature endocycling of Drosophila follicle cells causes pleiotropic defects in oogenesis. bioRxiv, PubMed ID: 37873193
Summary: Endocycling cells grow and repeatedly duplicate their genome without dividing. Cells switch from mitotic cycles to endocycles in response to developmental signals during the growth of specific tissues in a wide range of organisms. The purpose of switching to endocycles, however, remains unclear in many tissues. Additionally, cells can switch to endocycles in response to conditional signals, which can have beneficial or pathological effects on tissues. However, the impact of these unscheduled endocycles on development is underexplored. This study uses Drosophila ovarian somatic follicle cells as a model to examine the impact of unscheduled endocycles on tissue growth and function. Follicle cells normally switch to endocycles at mid-oogenesis. Inducing follicle cells to prematurely switch to endocycles resulted in lethality of the resulting embryos. Analysis of ovaries with premature follicle cell endocycles revealed aberrant follicular epithelial structure and pleiotropic defects in oocyte growth, developmental gene amplification, and the migration of a special set of follicle cells known as border cells. Overall, these findings reveal how unscheduled endocycles can disrupt tissue growth and function to cause aberrant development. A premature switch to polyploid endocycles in Drosophila ovarian follicle cells caused pleiotropic defects in oogenesis and compromised female fertility, revealing new ways in which unscheduled endocycles cause developmental defects. |
| Kotb, N. M., Ulukaya, G., Chavan, A., Nguyen, S. C., Proskauer, L., Joyce, E., Hasson, D., Jagannathan, M., Rangan, P. (2023). Genome organization regulates nuclear pore complex formation and promotes differentiation during Drosophila oogenesis. bioRxiv, PubMed ID: 38014330
Summary: Genome organization can regulate gene expression and promote cell fate transitions. The differentiation of germline stem cells (GSCs) to oocytes in Drosophila involves changes in genome organization mediated by heterochromatin and the nuclear pore complex (NPC). Heterochromatin represses germ-cell genes during differentiation and NPCs anchor these silenced genes to the nuclear periphery, maintaining silencing to allow for oocyte development. Surprisingly, this study found that genome organization also contributes to NPC formation, mediated by the transcription factor Stonewall (Stwl). As GSCs differentiate, Stwl accumulates at boundaries between silenced and active gene compartments. Stwl at these boundaries plays a pivotal role in transitioning germ-cell genes into a silenced state and activating a group of oocyte genes and Nucleoporins (Nups). The upregulation of these Nups during differentiation is crucial for NPC formation and further genome organization. Thus, crosstalk between genome architecture and NPCs is essential for successful cell fate transitions. | Wenzel, M., Aquadro, C. F. (2023). Wolbachia infection at least partially rescues the fertility and ovary defects of several new Drosophila melanogaster bag of marbles protein-coding mutants. bioRxiv, PubMed ID: 37645949
Summary: The D. melanogaster protein coding gene bag of marbles (bam) plays a key role in early male and female reproduction by forming complexes with partner proteins to promote differentiation in gametogenesis. Like another germline gene, Sex lethal, bam genetically interacts with the endosymbiont Wolbachia, as Wolbachia rescues the reduced fertility of a bam hypomorphic mutant. This study explored the specificity of the bam-Wolbachia interaction by generating 22 new bam mutants, with ten mutants displaying fertility defects. Nine of these mutants trend towards rescue by the w Mel Wolbachia variant, with eight statistically significant at the fertility and/or cytological level. In some cases, fertility was increased a striking 20-fold. There is no specificity between the rescue and the known binding regions of bam, suggesting w Mel does not interact with one singular bam partner to rescue the reproductive phenotype. Whether w Mel interacts with bam in a non-specific way was tested by increasing bam transcript levels or acting upstream in germline stem cells. A fertility assessment of a bam RNAi knockdown mutant reveals that w Mel rescue is specific to functionally mutant bam alleles and no obvious evidence was found of w Mel interaction with germline stem cells in bam mutants. |
Tuesday, July 9th - Behavior |
| Abhilash, L., Shafer, O. T. (2023). A two-process model of Drosophila sleep reveals an inter-dependence between circadian clock speed and the rate of sleep pressure decay. Sleep, PubMed ID: 37930351
Summary: Sleep is controlled by two processes - a circadian clock that regulates its timing and a homeostat that regulates the drive to sleep. Drosophila has been an insightful model for understanding both processes. For four decades, Borbely and Daan's two-process model has provided a powerful framework for understanding sleep regulation. However, the field of fly sleep has not employed such a model as a framework for the investigation of sleep. To this end, this study has adapted the two-process model to the fly and establish its utility by showing that it can provide empirically testable predictions regarding the circadian and homeostatic control of fly sleep. The ultradian rhythms previously reported for loss-of-function clock mutants in the fly are shown to be robustly detectable and a predictable consequence of a functional sleep homeostat in the absence of a functioning circadian system. It was founnd that a model in which the circadian clock speed and homeostatic rates act without influencing each other provides imprecise predictions regarding how clock speed influences the strength of sleep rhythms and the amount of daily sleep. This study also found that quantitatively good fits between empirical values and model predictions were achieved only when clock speeds were positively correlated with rates of decay of sleep pressure. The results indicate that longer sleep bouts better reflect the homeostatic process than the current definition of sleep as any inactivity lasting five minutes or more. This two-process model represents a powerful framework for work on the molecular and physiological regulation of fly sleep. | O'Hara, M. K., Saul, C., Handa, A., Sehgal, A., Williams, J. A. (2023). The NFkappaB Dif is required for behavioral and molecular correlates of sleep homeostasis in Drosophila. bioRxiv, PubMed ID: 37905096
Summary: The nuclear factor binding the κ light chain in B-cells (NFκB) is involved in a wide range of cellular processes including development, growth, innate immunity, and sleep. However, efforts have been limited toward understanding how specific NFκB transcription factors function in sleep. Drosophila fruit flies carry three genes encoding NFκB transcription factors, Dorsal, Dorsal Immunity Factor (Dif), and Relish. Previous work found that loss of the Relish gene from fat body suppressed daily nighttime sleep, and abolished infection-induced sleep. This study shows that Dif regulates daily sleep and recovery sleep following prolonged wakefulness. Mutants of Dif showed reduced daily sleep and suppressed recovery in response to sleep deprivation. Pan-neuronal knockdown of Dif strongly suppressed daily sleep, indicating that in contrast to Relish, Dif functions from the central nervous system to regulate sleep. Based on the distribution of a Dif-associated GAL4 driver, it was hypothesized that its effects on sleep were mediated by the pars intercerebralis (PI). While RNAi knock-down of Dif in the PI reduced daily sleep, it had no effect on the recovery response to sleep deprivation. However, recovery sleep was suppressed when RNAi knock-down of Dif was distributed across a wider range of neurons. Induction of the nemuri (nur) antimicrobial peptide by sleep deprivation was suppressed in Dif mutants and pan-neuronal over-expression of nur also suppressed the Dif mutant phenotype. Together, these findings indicate that Dif functions from brain to target nemuri and to promote sleep. |
| Sten, T. H., Li, R., Hollunder, F., Eleazer, S., Ruta, V. (2023). Male-male interactions shape mate selection in Drosophila. bioRxiv, PubMed ID: 37961193
Summary: Males of many species have evolved behavioral traits to both attract females and repel rivals. This study explored mate selection in Drosophila from both the male and female perspective to shed light on how these key components of sexual selection - female choice and male-male competition - work in concert to guide reproductive strategies. Male flies were found to fend off competing suitors by interleaving their courtship of a female with aggressive wing flicks, which both repel competitors and generate a 'song' that obscures the female's auditory perception of other potential mates. Two higher-order circuit nodes - P1a and pC1x neurons - are coordinately recruited to allow males to flexibly interleave these agonistic actions with courtship displays, assuring they persistently pursue females until their rival falters. Together, these results suggest that female mating decisions are shaped by male-male interactions, underscoring how a male's ability to subvert his rivals is central to his reproductive success. | Safdar, M., Wessells, R. J. (2023). Octopamine Rescues Endurance and Climbing Speed in Drosophila Clk(out) Mutants with Circadian Rhythm Disruption. Cells, 12(21) PubMed ID: 37947593
Summary: Circadian rhythm disturbances are associated with various negative health outcomes, including an increasing incidence of chronic diseases with high societal costs. While exercise can protect against the negative effects of rhythm disruption, it is not available to all those impacted by sleep disruptions, in part because sleep disruption itself reduces exercise capacity. Thus, there is a need for therapeutics that bring the benefits of exercise to this population. This study investigated the relationship between exercise and circadian disturbances using a well-established Drosophila model of circadian rhythm loss, the Clkout mutant. Clkout was found to cause reduced exercise capacity, measured as post-training endurance, flight performance, and climbing speed, and these phenotypes are not rescued by chronic exercise training. However, exogenous administration of a molecule known to mediate the effects of chronic exercise, octopamine (OA), was able to effectively rescue mutant exercise performance, including the upregulation of other known exercise-mediating transcripts, without restoring the circadian rhythms of mutants. This work points the way toward the discovery of novel therapeutics that can restore exercise capacity in patients with rhythm disruption. |
| Gornostaev, N. G., Ruchin, A. B., Esin, M. N., Lazebny, O. E., Kulikov, A. M. (2023). Vertical Distribution of Fruit Flies (Diptera: Drosophilidae) in Deciduous Forests in the Center of European Russia. Insects, 14(10) PubMed ID: 37887834
Summary: Research of Diptera in temperate forests has demonstrated uneven vertical distributions of insects. In this study, the vertical distribution, seasonal fluctuations, and species diversity of Drosophilidae species in the Mordovia State Reserve were studied. This research marks the first exploration of drosophilid vertical stratification in the European part of Russia. Using traps, flies were collected in four deciduous forest sites between early June and mid-September in 2020. A total of 27,151 individuals from 10 genera and 34 drosophilid species were identified, with 6 species from 4 genera being new to the Republic of Mordovia. Drosophila obscura Fll. and Scaptodrosophila rufifrons Lw. were the most abundant species in traps. The total highest number of drosophilid flies (10,429 individuals) was captured at a height of 1.5 m, while the lowest number (5086 individuals) was recorded at 12 m. The average number of flies was 6240 and 5387 individuals at heights of 7.5 m and 3.5 m, respectively. However, the prevalence of drosophilid numbers at the 1.5-m height was not constant during the season. It was found that in the second part of July the total fly counts at heights of 7.5 m and 12 m exceeded those at 1.5 m. This study has described five different types of vertical distribution of drosophilids throughout the season, which differs markedly in mycetobionts and xylosaprobionts ecological groups. Species diversity demonstrated variations across different sites and tiers during the season, with peak diversity observed in June and September. | Yoshikawa, S., Tang, P., Simpson, J. H. (2023). Mechanosensory and command contributions to the Drosophila grooming sequence. bioRxiv, PubMed ID: 38045358
Summary: Flies groom in response to competing mechanosensory cues in an anterior to posterior order using specific legs. From behavior screens, this study identified a pair of cholinergic command-like neurons, Mago-no-Te (MGT), whose optogenetic activation elicits thoracic grooming by hind legs. Thoracic grooming is typically composed of body sweeps and leg rubs in alternation, but clonal analysis coupled with amputation experiments revealed that MGT activation only commands the body sweeps: initiation of leg rubbing requires contact between leg and thorax. With new electron microscopy (EM) connectome data for the ventral nerve cord (VNC), a circuit-based explanation was uncovered for why stimulation of posterior thoracic mechanosensory bristles initiates cleaning by the hind legs. Previous work showed that flies weigh mechanosensory inputs across the body to select which part to groom, but it was not known why the thorax was always cleaned last. The connectome for the VNC enabled identification if a pair of GABAergic inhibitory neurons, UMGT1, that receive diverse sensory inputs and synapse onto both MGT and components of its downstream pre-motor circuits. Optogenetic activation of UMGT1 suppresses thoracic cleaning, representing a mechanism by which mechanosensory stimuli on other body parts could take precedence in the grooming hierarchy. The pre-motor circuit downstream of MGT was mapped, including inhibitory feedback connections that may enable rhythmicity and coordination of limb movement during thoracic grooming. |
Monday, July 8th - Cancer, Tumors, and Growth |
| Martinez-Abarca Millan, A., Martin-Bermudo, M. D. (2023). Integrins Can Act as Suppressors of Ras-Mediated Oncogenesis in the Drosophila Wing Disc Epithelium. Cancers, 15(22) PubMed ID: 38001693
Summary: Cancer is the second leading cause of death worldwide. Key to cancer initiation and progression is the crosstalk between cancer cells and their microenvironment. The extracellular matrix (ECM) is a major component of the tumour microenvironment and integrins, main cell-ECM adhesion receptors, are involved in every step of cancer progression. However, accumulating evidence has shown that integrins can act as tumour promoters but also as tumour suppressor factors, revealing that the biological roles of integrins in cancer are complex. This incites a better understating of integrin function in cancer progression. To achieve this goal, simple model organisms, such as Drosophila, offer great potential to unravel underlying conceptual principles. This study found that in the Drosophila wing disc epithelium the βPS integrins act as suppressors of tumours induced by a gain of function of the oncogenic form of Ras, Ras(V)(12). βPS integrin depletion enhances the growth, delamination and invasive behaviour of Ras(V)(12) tumour cells, as well as their ability to affect the tumour microenvironment. These results strongly suggest that integrin function as tumour suppressors might be evolutionarily conserved. Drosophila can be used to understand the complex tumour modulating activities conferred by integrins, thus facilitating drug development. | Sanz, F. J., Martinez-Carrion, G., Solana-Manrique, C. and Paricio, N. (2023). Evaluation of type 1 diabetes mellitus as a risk factor of Parkinson's disease in a Drosophila model. J Exp Zool A Ecol Integr Physiol. PubMed ID: 37381093
Summary: Diabetes mellitus (DM) is a chronic metabolic disease characterized by high blood glucose levels, resulting from insulin dysregulation. Parkinson's disease (PD) is the most common neurodegenerative motor disorder caused by the selective loss of dopaminergic (DA) neurons in the substantia nigra pars compacta. DM and PD are both age-associated diseases that are turning into epidemics worldwide. Previous studies have indicated that type 2 DM might be a risk factor of developing PD. However, scarce information about the link between type 1 DM (T1DM) and PD does exist. This study generated a Drosophila model of T1DM based on insulin deficiency to evaluate if T1DM could be a risk factor to trigger PD onset. As expected, model flies exhibited T1DM-related phenotypes such as insulin deficiency, increased content of carbohydrates and glycogen, and reduced activity of insulin signaling. Interestingly, the results also demonstrated that T1DM model flies presented locomotor defects as well as reduced levels of tyrosine hydroxylase (a marker of DA neurons) in brains, which are typical PD-related phenotypes. In addition, T1DM model flies showed elevated oxidative stress levels, which could be causative of DA neurodegeneration. Therefore, these results indicate that T1DM might be a risk factor of developing PD, and encourage further studies to shed light into the exact link between both diseases. |
| Guo, T., Miao, C., Liu, Z., Duan, J., Ma, Y., Zhang, X., Yang, W., Xue, M., Deng, Q., Guo, P., Xi, Y., Yang, X., Huang, X., Ge, W. (2023). Impaired dNKAP function drives genome instability and tumorigenic growth in Drosophila epithelia. J Mol Cell Biol, PubMed ID: 38059855
Summary: Mutations or dysregulated expression of NF-kappaB activating protein (NKAP) family genes have been found in human cancers. How NKAP family gene mutations promote tumor initiation and progression remains to be determined. This study characterized dNKAP, the Drosophila homolog of NKAP, and showed that impaired dNKAP function causes genome instability and tumorigenic growth in a Drosophila epithelial tumor model. dNKAP-knockdown wing imaginal discs exhibit tumorigenic characteristics, including tissue overgrowth, cell invasive behavior, abnormal cell polarity, and cell adhesion defects. dNKAP knockdown causes both R-loop accumulation and DNA damage, indicating the disruption of genome integrity. Further analysis showed that dNKAP knockdown induces c-Jun N-terminal kinase (JNK)-dependent apoptosis and causes changes in cell proliferation in distinct cell populations. Activation of the Notch and JAK/STAT signaling pathways contributes to the tumorigenic growth of dNKAP-knockdown tissues. Furthermore, JNK signaling is essential for dNKAP depletion-mediated cell invasion. Transcriptome analysis of dNKAP-knockdown tissues confirmed the misregulation of signaling pathways involved in promoting tumorigenesis and revealed abnormal regulation of metabolic pathways. dNKAP knockdown and oncogenic Ras, Notch, or Yki mutations show synergies in driving tumorigenesis, further supporting the tumor-suppressive role of dNKAP. In summary, this study demonstrates that dNKAP plays a tumor-suppressive role by preventing genome instability in Drosophila epithelia and thus provides novel insights into the roles of human NKAP family genes in tumor initiation and progression. | Pfefferkorn, R. M., Mortzfeld, B. M., Fink, C., Frieling, J. V., Bossen, J., Esser, D., Kaleta, C., Rosenstiel, P., Heine, H., Roeder, T. (2024). Recurrent Phases of Strict Protein Limitation Inhibit Tumor Growth and Restore Lifespan in A Drosophila Intestinal Cancer Model. Aging and disease, 15(1):226-244 PubMed ID: 37962464
Summary: Diets that restrict caloric or protein intake offer a variety of benefits, including decreasing the incidence of cancer. However, whether such diets pose a substantial therapeutic benefit as auxiliary cancer treatments remains unclear. This study determined the effects of severe protein depletion on tumorigenesis in a Drosophila melanogaster intestinal tumor model, using a human RAF gain-of-function allele. Severe and continuous protein restriction significantly reduced tumor growth but resulted in premature death. Therefore, a diet was developed in which short periods of severe protein restriction alternated cyclically with periods of complete feeding. This nutritional regime reduced tumor mass, restored gut functionality, and rescued the lifespan of oncogene-expressing flies to the levels observed in healthy flies on a continuous, fully nutritious diet. Furthermore, this diet reduced the chemotherapy-induced stem cell activity associated with tumor recurrence. Transcriptome analysis revealed long-lasting changes in the expression of key genes involved in multiple major developmental signaling pathways. Overall, the data suggest that recurrent severe protein depletion effectively mimics the health benefits of continuous protein restriction, without undesired nutritional shortcomings. This provides seminal insights into the mechanisms of the memory effect required to maintain the positive effects of protein restriction throughout the phases of a full diet. Finally, the repetitive form of strict protein restriction is an ideal strategy for adjuvant cancer therapy that is useful in many tumor contexts. Summary: |
| Li, Y., Pan, L., Li, P., Gao, F., Wang, L., Chen, J., Li, Z., Gao, Y., Gong, Y., Jin, F. (2023). Isolation of Enterococcus faecium and determination of its mechanism for promoting the growth and development of Drosophila. Sci Rep, 13(1):18726 PubMed ID: 37907538
Summary: Intestinal symbiotic microorganisms have a strong capacity to regulate the physiological functions of their host, and Drosophila serves as a useful model. Enterococcus faecium (E. faecium) is a member of the normal intestinal flora of animals. Lactic acid bacteria (LAB) such as E. faecium can promote the growth and development of Drosophila, but the mechanism of regulation of Drosophila is poorly understood. This study found that E. faecium used a carbon source to produce probiotic acids. E. faecium is a symbiotic bacterium for Drosophila, and adult flies passed on parental flora to offspring. E. faecium promoted the growth and development of Drosophila, especially under poor nutritional conditions. E. faecium shortened the developmental process for Drosophila and accelerated the transformation from larva to pupa. Finally, E. faecium promoted the growth and development of Drosophila through TOR and insulin signalling pathways. | Hofstetter, J., Ogunleye, A., Kutschke, A., Buchholz, L. M., Wolf, E., Raabe, T., Gallant, P. (2024). Spt5 interacts genetically with Myc and is limiting for brain tumor growth in Drosophila. Life science alliance, 7(1) PubMed ID: 37935464
Summary: The transcription factor SPT5 physically interacts with MYC oncoproteins and is essential for efficient transcriptional activation of MYC targets in cultured cells. This study used Drosophila to address the relevance of this interaction in a living organism. Spt5 displays moderate synergy with Myc in fast proliferating young imaginal disc cells. During later development, Spt5-knockdown has no detectable consequences on its own, but strongly enhances eye defects caused by Myc overexpression. Similarly, Spt5-knockdown in larval type 2 neuroblasts has only mild effects on brain development and survival of control flies, but dramatically shrinks the volumes of experimentally induced neuroblast tumors and significantly extends the lifespan of tumor-bearing animals. This beneficial effect is still observed when Spt5 is knocked down systemically and after tumor initiation, highlighting SPT5 as a potential drug target in human oncology. |
Friday, July 5th - Disease Models |
| Escobedo, S. E., McGovern, S. E., Jauregui-Lozano, J. P., Stanhope, S. C., Anik, P., Singhal, K., DeBernardis, R., Weake, V. M. (2023). Targeted RNAi screen identifies transcriptional mechanisms that prevent premature degeneration of adult photoreceptors. Frontiers in epigenetics and epigenomics, 1 PubMed ID: 37901602
Summary: Aging is associated with a decline in visual function and increased prevalence of ocular disease, correlating with changes in the transcriptome and epigenome of cells in the eye. This study sought to identify the transcriptional mechanisms that are necessary to maintain photoreceptor viability and function during aging. To do this, A targeted photoreceptor-specific RNAi screen was performed in Drosophila to identify transcriptional regulators whose knockdown results in premature, age-dependent retinal degeneration. From an initial set of 155 RNAi lines each targeting a unique gene and spanning a diverse set of transcription factors, chromatin remodelers, and histone modifiers, 18 high-confidence target genes were identified whose decreased expression in adult photoreceptors leads to premature and progressive retinal degeneration. These 18 target genes were enriched for factors involved in the regulation of transcription initiation, pausing, and elongation, suggesting that these processes are essential for maintaining the health of aging photoreceptors. To identify the genes regulated by these factors, the photoreceptor transcriptome was profiled in a subset of lines. Strikingly, two of the 18 target genes, Spt5 and domino, show similar changes in gene expression to those observed in photoreceptors with advanced age. Together, these data suggest that dysregulation of factors involved in transcription initiation and elongation plays a key role in shaping the transcriptome of aging photoreceptors. Further, these findings indicate that the age-dependent changes in gene expression not only correlate but might also contribute to an increased risk of retinal degeneration | Dondi, C., Vogler, G., Gupta, A., Walls, S. M., Kervadec, A., Romero, M. R., Diop, S. B., Goode, J., Thomas, J. B., Colas, A. R., Bodmer, R., Montminy, M., Ocorr, K. (2023). The nutrient sensor CRTC & Sarcalumenin / Thinman represent a new pathway in cardiac hypertrophy. bioRxiv, PubMed ID: 37873259
Summary: Obesity and type 2 diabetes are at epidemic levels and a significant proportion of these patients are diagnosed with left ventricular hypertrophy. CREB R egulated T ranscription C o-activator (CRTC) is a key regulator of metabolism in mammalian hepatocytes, where it is activated by calcineurin (CaN) to increase expression of gluconeogenic genes. CaN is known its role in pathological cardiac hypertrophy, however, a role for CRTC in the heart has not been identified. In Drosophila, CRTC null mutants have little body fat and exhibit severe cardiac restriction, myofibrillar disorganization, cardiac fibrosis and tachycardia, all hallmarks of heart disease. Cardiac-specific knockdown of CRTC, or its coactivator CREBb, mimicked the reduced body fat and heart defects of CRTC null mutants. Comparative gene expression in CRTC loss- or gain-of-function fly hearts revealed contra-regulation of genes involved in glucose, fatty acid, and amino acid metabolism, suggesting that CRTC also acts as a metabolic switch in the heart. Among the contra-regulated genes with conserved CREB binding sites, the fly ortholog of Sarcalumenin, which is a Ca (2+) -binding protein in the sarcoplasmic reticulum, was identified. Cardiac knockdown recapitulated the loss of CRTC cardiac restriction and fibrotic phenotypes, suggesting it is a downstream effector of CRTC, that was named thinman (tmn). Importantly, cardiac overexpression of either CaN or CRTC in flies caused hypertrophy that was reversed in a CRTC mutant background, suggesting CRTC mediates hypertrophy downstream of CaN, perhaps as an alternative to NFAT. CRTC novel role in the heart is likely conserved in vertebrates as knockdown in zebrafish also caused cardiac restriction, as in flies. These data suggest that CRTC is involved in myocardial cell maintenance and that CaN-CRTC- Sarcalumenin/ tmn signaling represents a novel and conserved pathway underlying cardiac hypertrophy. |
| Buck, S. A., Rubin, S. A., Kunkhyen, T., Treiber, C. D., Xue, X., Fenno, L. E., Mabry, S. J., Sundar, V. R., Yang, Z., Shah, D., S., Awatramani, R., Watson, A. M., Waddell, S., Cheetham, C. E. J., Logan, R. W., Freyberg, Z. (2023). Sexually dimorphic mechanisms of VGLUT-mediated protection from dopaminergic neurodegeneration. bioRxiv, PubMed ID: 37873436
Summary: Parkinson's disease (PD) targets some dopamine (DA) neurons more than others. Sex differences offer insights, with females more protected from DA neurodegeneration. The mammalian vesicular glutamate transporter VGLUT2 and Drosophila ortholog dVGLUT have been implicated as modulators of DA neuron resilience. However, the mechanisms by which VGLUT2/dVGLUT protects DA neurons remain unknown. This study discovered DA neuron dVGLUT knockdown increased mitochondrial reactive oxygen species in a sexually dimorphic manner in response to depolarization or paraquat-induced stress, males being especially affected. DA neuron dVGLUT also reduced ATP biosynthetic burden during depolarization. RNA sequencing of VGLUT(+) DA neurons in mice and flies identified candidate genes that were functionally screened to further dissect VGLUT-mediated DA neuron resilience across PD models. Transcription factors modulating dVGLUT-dependent DA neuroprotection were discovered and dj-1β was identified as a regulator of sex-specific DA neuron dVGLUT expression. Overall, VGLUT protects DA neurons from PD-associated degeneration by maintaining mitochondrial health. | Cuddapah, V. A., Hsu, C. T., Li, Y., Shah, H. M., Saul, C., Killiany, S., Shon, J., Yue, Z., Gionet, G., Putt, M. E., Sehgal, A. (2023). Sleepiness, not total sleep amount, increases seizure risk. bioRxiv. PubMed ID: 37873373
Summary: Sleep loss has been associated with increased seizure risk since antiquity. Despite this observation standing the test of time, how poor sleep drives susceptibility to seizures remains unclear. To identify underlying mechanisms, sleep was restricted in Drosophila epilepsy models and a method was developed to identify spontaneous seizures using quantitative video tracking. This study found that sleep loss exacerbates seizures but only when flies experience increased sleep need, or sleepiness, and not necessarily with reduced sleep quantity. This is supported by the paradoxical finding that acute activation of sleep-promoting circuits worsens seizures, because it increases sleep need without changing sleep amount. Sleep-promoting circuits become hyperactive after sleep loss and are associated with increased whole-brain activity. During sleep restriction, optogenetic inhibition of sleep-promoting circuits to reduce sleepiness protects against seizures. Downregulation of the 5HT1A serotonin receptor in sleep-promoting cells mediates the effect of sleep need on seizures, and an FDA-approved 5HT1A agonist was identified to mitigate seizures. These findings demonstrate that while homeostatic sleep is needed to recoup lost sleep, it comes at the cost of increasing seizure susceptibility. This study provides an unexpected perspective on interactions between sleep and seizures, and surprisingly implicate sleep- promoting circuits as a therapeutic target for seizure control. |
| Ahn, J. S., Mahbub, N. U., Kim, S., Kim, H. B., Choi, J. S., Chung, H. J., Hong, S. T. (2023). Nectandrin B significantly increases the lifespan of Drosophila - Nectandrin B for longevity. Aging, 15(22):12749-12762 PubMed ID: 37983180
Summary: Phytochemicals are increasingly recognized in the field of healthy aging as potential therapeutics against various aging-related diseases. Nutmeg, derived from the Myristica fragrans tree, is an example. Nutmeg has been extensively studied and proven to possess antioxidant properties that protect against aging and alleviate serious diseases such as cancer, heart disease, and liver disease. However, the specific active ingredient in nutmeg responsible for these health benefits has not been identified thus far. In this study presents evidence that Nectandrin B (NecB), a bioactive lignan compound isolated from nutmeg, significantly extended the lifespan of the fruit fly Drosophila melanogaster by as much as 42.6% compared to the control group. NecB also improved age-related symptoms including locomotive deterioration, body weight gain, eye degeneration, and neurodegeneration in aging D. melanogaster. This result represents the most substantial improvement in lifespan observed in animal experiments to date, suggesting that NecB may hold promise as a potential therapeutic agent for promoting longevity and addressing age-related degeneration. | Lenzi, C., Piat, A., Schlich, P., Ducau, J., Bregliano, J. C., Aguilaniu, H., Laurencon, A. (2023). Parental age effect on the longevity and healthspan in Drosophila melanogaster and Caenorhabditis elegans. Aging, 15(21):11720-11739 PubMed ID: 37917003
Summary: Several studies have investigated the effect of parental age on biological parameters such as reproduction, lifespan, and health; however, the results have been inconclusive, largely due to inter-species variation and/or modest effect sizes. This studsy examined the effect of parental age on the lifespan, reproductive capacity, and locomotor activity of genetic isogenic lines of the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. The progeny of successive generations of old parents had significantly shorter lifespans than the progeny of young parents in both species. Moreover, this study investigated the fertility, fecundity, and locomotor activity of C. elegans. Interestingly, both the shorter lifespan and deteriorated healthspan of the progeny were significantly improved by switching to only one generation of younger parents. Collectively, these data demonstrate that the detrimental effect of older parental age on the longevity of the progeny can be reversed, suggesting the existence of a beneficial non-genetic mechanism. |
Wednesday, July 3rd - Adult Neural Structure, Development, and Function |
| Martin, M., Gutierrez-Avino, F., Shaikh, M. N., Tejedor, F. J. (2023). A novel proneural function of Asense is integrated with the sequential actions of Delta-Notch, L'sc and Su(H) to promote the neuroepithelial to neuroblast transition. PLoS Genet, 19(10):e1010991 PubMed ID: 37871020
Summary: In order for neural progenitors (NPs) to generate distinct populations of neurons at the right time and place during CNS development, they must switch from undergoing purely proliferative, self-renewing divisions to neurogenic, asymmetric divisions in a tightly regulated manner. In the developing Drosophila optic lobe, neuroepithelial (NE) cells of the outer proliferation center (OPC) are progressively transformed into neurogenic NPs called neuroblasts (NBs) in a medial to lateral proneural wave. The cells undergoing this transition express Lethal of Scute (L'sc), a proneural transcription factor (TF) of the Acheate Scute Complex (AS-C). There is also a peak of expression of Asense (Ase), another AS-C TF, in the cells neighboring those with transient L'sc expression. These peak of Ase cells help to identify a new transitional stage as they have lost NE markers and L'sc, they receive a strong Notch signal and barely exhibit NB markers. This expression of Ase is necessary and sufficient to promote the NE to NB transition in a more robust and rapid manner than that of l'sc gain of function or Notch loss of function. Thus, these data provide the first direct evidence of a proneural role for Ase in CNS neurogenesis. Strikingly, it was found that strong Delta-Notch signaling at the lateral border of the NE triggers l'sc expression, which in turn induces ase expression in the adjacent cells through the activation of Delta-Notch signaling. These results reveal two novel non-conventional actions of Notch signaling in driving the expression of proneural factors, in contrast to the repression that Notch signaling exerts on them during classical lateral inhibition. Finally, Suppressor of Hairless (Su(H)), which seems to be upregulated late in the transitioning cells and in NBs, represses l'sc and ase, ensuring their expression is transient. Thus, these data identify a key proneural role of Ase that is integrated with the sequential activities of Delta-Notch signaling, L'sc, and Su(H), driving the progressive transformation of NE cells into NBs. | Peng, Y. X., Liu, Z. Y., Lin, P. X., Su, S. C., Gao, C. F., Wu, S. F. (2023). Reverse genetic study reveals the molecular targets of chordotonal organ TRPV channel modulators. Pesticide biochemistry and physiology, 196:105584 PubMed ID: 37945222
Summary: Insecticides have been widely used for the control of insect pests that have a significant impact on agriculture and human health. A better understanding of insecticide targets is needed for effective insecticide design and resistance management. Pymetrozine, afidopyropen and flonicamid are reported to target on proteins that located on insect chordotonal organs, resulting in the disruption of insect coordination and the inhibition of feeding. This study systematically examined the susceptibility of six Drosophila melanogaster mutants (five transient receptor potential channels and one mechanoreceptor) to three commercially used insecticides, in order to identify the receptor subunits critical to the insect's response to insecticides. The results showed that iav1, nan36a and wtrw1/i< mutants exhibited significantly reduced susceptibility to pymetrozine and afidopyropen, but not to flonicamid. The number of eggs produced by the three mutant females were significantly less than that of the w(1118) strain. Meanwhile, the longevity of all male mutants and females of nan36a and wtrw1 mutants was significantly shorter than that of the w(1118) strain as the control. However, no gravitaxis defects were observed in wtrw1 mutants and the anti-gravitaxis ofwtrw1 mutants was abolished by pymetrozine. Behavioral assays using thermogenetic tools further confirmed the bioassay results and supported the idea that Nan as a TRPV subfamily member located in Drosophila chordotonal neurons, acting as a target of pymetrozine, which interferes with Drosophila and causes motor deficits with gravitaxis defects. Taken together, this study elucidates the interactions of pymetrozine and afidopyropen with TRPV channels, Nan and Iav, and TRPA channel, Wtrw. This research provides another evidence that pymetrozine and afidopyropen might target on nan, iav and wtrw channels and provides insights into the development of sustainable pest management strategies. |
| Gonzalez, Y. R., Kamkar, F., Jafar-Nejad, P., Wang, S., Qu, D., Alvarez, L. S., Hawari, D., Sonnenfeld, M., Slack, R. S., Albert, P. R., Park, D. S., Joselin, A. (2023). PFTK1 kinase regulates axogenesis during development via RhoA activation. BMC Biol, 21(1):240 PubMed ID: 37907898
Summary: BAPFTK1/Eip63E is a member of the cyclin-dependent kinases (CDKs) family and plays an important role in normal cell cycle progression. Eip63E expresses primarily in postnatal and adult nervous system in Drosophila melanogaster but its role in CNS development remains unknown. This study sought to understand the function of Eip63E in the CNS by studying the fly ventral nerve cord during development. The results demonstrate that Eip63E regulates axogenesis in neurons and its deficiency leads to neuronal defects. Functional interaction studies performed using the same system identify an interaction between Eip63E and the small GTPase Rho1. Furthermore, deficiency of Eip63E homolog in mice, PFTK1, in a newly generated PFTK1 knockout mice results in increased axonal outgrowth confirming that the developmental defects observed in the fly model are due to defects in axogenesis. Importantly, RhoA phosphorylation and activity are affected by PFTK1 in primary neuronal cultures. GDP-bound inactive RhoA is a substrate of PFTK1 and PFTK1 phosphorylation is required for RhoA activity. In conclusion, this work establishes an unreported neuronal role of PFTK1 in axon development mediated by phosphorylation and activation of GDP-bound RhoA. The results presented add to understanding of the role of Cdks in the maintenance of RhoA-mediated axon growth and its impact on CNS development and axonal regeneration. | Ahn, J. E., Amrein, H. (2023). Opposing chemosensory functions of closely related gustatory receptors. bioRxiv, PubMed ID: 37905057
Summary: Most animals have functionally distinct populations of taste cells, expressing receptors that are tuned to compounds of different valence. In D. melanogaster, primary sensory neurons express taste receptors that are tuned to distinct groups of chemicals, thereby activating neural ensembles that elicit either feeding or avoidance behavior. Members of a family of ligand gated receptor channels, the Gustatory receptors (Grs), play a central role in these behaviors. In general, closely related, evolutionarily conserved Gr proteins are co-expressed in the same type of taste neurons, tuned to chemically related compounds, and therefore triggering the same behavioral response. This study reports that members of the Gr28 subfamily are expressed in largely non-overlapping sets of taste neurons in Drosophila larvae, detect chemicals of different valence and trigger opposing feeding behaviors. The intrinsic properties of Gr28 neurons by were determined by expressing the mammalian Vanilloid Receptor (VR1), which is activated by capsaicin, a chemical to which wildtype Drosophila larvae do not respond. When VR1 is expressed in Gr28a neurons, larvae become attracted to capsaicin, consistent with reports showing that Gr28a itself encodes a receptor for nutritious RNA. In contrast, expression of VR1 in two pairs of Gr28b.c neurons triggers avoidance to capsaicin. Moreover, neuronal inactivation experiments show that the Gr28b.c neurons are necessary for avoidance of several bitter compounds. Lastly, behavioral experiments of Gr28 deficient larvae and live Ca (2+) imaging studies of Gr28b.c neurons revealed that denatonium benzoate, a synthetic bitter compound that shares structural similarities with natural bitter chemicals, is a ligand for a receptor complex containing a Gr28b.c or Gr28b.a subunit. Thus, the Gr28 proteins, which have been evolutionarily conserved over 260 million years in insects, represent the first taste receptor subfamily in which specific members mediate behavior with opposite valence. |
| Dweck, H. K. M., Carlson, J. R. (2023). Diverse mechanisms of taste coding in Drosophila. Sci Adv, 9(46):eadj7032 PubMed ID: 37976361
Summary: Taste systems encode chemical cues that drive vital behaviors. This study has elucidated noncanonical features of taste coding using an unconventional kind of electrophysiological analysis. Taste neurons of Drosophila are much more sensitive than previously thought. They have a low spontaneous firing frequency that depends on taste receptors. Taste neurons have a dual function as olfactory neurons: They are activated by most tested odorants, including N,N-diethyl-meta-toluamide (DEET), at a distance. DEET can also inhibit certain taste neurons, revealing that there are two modes of taste response: activation and inhibition. Electrophysiological OFF responses were characterized and it was found that the tastants that elicit them are related in structure. OFF responses link tastant identity to behavior: the magnitude of the OFF response elicited by a tastant correlated with the egg laying behavior it elicited. In summary, the sensitivity and coding capacity of the taste system are much greater than previously known. | Jouandet, G. C., Alpert, M. H., Simoes, J. M., Suhendra, R., Frank, D. D., Levy, J. I., Para, A., Kath, W. L., Gallio, M. (2023). Rapid threat assessment in the Drosophila thermosensory system. Nat Commun, 14(1):7067 PubMed ID: 37923719
Summary: Neurons that participate in sensory processing often display "ON" responses, i.e., fire transiently at the onset of a stimulus. ON transients are widespread, perhaps universal to sensory coding, yet their function is not always well-understood. This study shows that ON responses in the Drosophila thermosensory system extrapolate the trajectory of temperature change, priming escape behavior if unsafe thermal conditions are imminent. First, it was shown that second-order thermosensory projection neurons (TPN-IIIs) and their Lateral Horn targets (TLHONs), display ON responses to thermal stimuli, independent of direction of change (heating or cooling) and of absolute temperature. Instead, they track the rate of temperature change, with TLHONs firing exclusively to rapid changes (>0.2 °C/s). Next, connectomics were used to track TLHONs' output to descending neurons that control walking and escape, and modeling and genetic silencing to demonstrate how ON transients can flexibly amplify aversive responses to small thermal change. These results suggest that, across sensory systems, ON transients may represent a general mechanism to systematically anticipate and respond to salient or dangerous conditions. |
Tuesday, July 2nd - Adult Physiology and Metabolism |
| Malik, D. M., Sengupta, A., Sehgal, A., Weljie, A. M. (2023). Altered Metabolism During the Dark Period in Drosophila Short Sleep Mutants. bioRxiv, PubMed ID: 37961245
Summary: Sleep is an almost universally required state in biology. Disrupted sleep has been associated with adverse health risks including metabolic perturbations. Sleep is in part regulated via circadian mechanisms, however, metabolic dysfunction at different times of day arising from sleep disruption is unclear. This study used targeted liquid chromatography-mass spectrometry to probe metabolic alterations using high-resolution temporal sampling of two Drosophila short sleep mutants, fumin and sleepless, across a circadian day. Discriminant analyses revealed overall distinct metabolic profiles for mutants when compared to a wild type dataset. Altered levels of metabolites involved in nicotinate/nicotinamide, alanine, aspartate, and glutamate, glyoxylate and dicarboxylate metabolism, and the TCA cycle were observed in mutants suggesting increased energetic demands. Furthermore, rhythmicity analyses revealed fewer 24 hr rhythmic metabolites in both mutants. Interestingly, mutants displayed two major peaks in phases while wild type displayed phases that were less concerted. In contrast to 24 hr rhythmic metabolites, an increase in the number of 12 hr rhythmic metabolites was observed in fumin while sleepless displayed a decrease. These results support that decreased sleep alters the overall metabolic profile with short sleep mutants displaying altered metabolite levels associated with a number of pathways in addition to altered neurotransmitter levels. | Tang, C., Li, Q., Wang, X., Yu, Z., Ping, X., Qin, Y., Liu, Y., Zheng, L. (2024). Cardiac Timeless Trans-Organically Regulated by miR-276 in Adipose Tissue Modulates Cardiac Function. Function (Oxford, England), 5(1):zqad064 PubMed ID: 38058384
Summary: The interconnection between cardiac function and circadian rhythms is of great importance. While the role of the biological clock gene Timeless (Tim) in circadian rhythm has been extensively studied, its impact on cardiac function remains largely been unexplored. Previous research has provided experimental evidence for the regulation of the heart by adipose tissue and the targeting of miR-276a/b on Timeless. However, the extent to which adipose tissue regulates cardiac Timeless genes trans-organically through miR-276a/b, and subsequently affects cardiac function, remains uncertain. Therefore, the objective of this study was to investigate the potential trans-organ modulation of the Timeless gene in the heart by adipose tissue through miR-276a/b. Cardiac-specific Timeless knockdown and overexpression was shown to result in a significant increase in heart rate (HR) and a significant decrease in Heart period (HP), diastolic intervals (DI), systolic intervals (SI), diastolic diameter (DD), and systolic diameter (SD). miR-276b systemic knockdown resulted in a significant increase in DI, arrhythmia index (AI), and fractional shortening (FS) significantly increased and SI, DD and SD significantly decreased. Adipose tissue-specific miR-276a/b knockdown and miR-276a overexpression resulted in a significant increase in HR and a significant decrease in DI and SI, which were improved by exercise intervention. This study presents a novel finding that highlights the significance of the heart circadian clock gene Timeless in heart function. Additionally, it demonstrates that adipose tissue exerts trans-organ modulation on the expression of the heart Timeless gene via miR-276a/b. |
| Li, X., Karpac, J. (2023). A distinct Acyl-CoA binding protein (ACBP6) shapes tissue plasticity during nutrient adaptation in Drosophila. Nat Commun, 14(1):7599 PubMed ID: 37989752
Summary: Nutrient availability is a major selective force in the evolution of metazoa, and thus plasticity in tissue function and morphology is shaped by adaptive responses to nutrient changes. Utilizing Drosophila, this study revealed that distinct calibration of acyl-CoA metabolism, mediated by Acbp6 (Acyl-CoA binding-protein 6), is critical for nutrient-dependent tissue plasticity. Drosophila Acbp6, which arose by evolutionary duplication and binds acyl-CoA to tune acetyl-CoA metabolism, is required for intestinal resizing after nutrient deprivation through activating intestinal stem cell proliferation from quiescence. Disruption of acyl-CoA metabolism by Acbp6 attenuation drives aberrant 'switching' of metabolic networks in intestinal enterocytes during nutrient adaptation, impairing acetyl-CoA metabolism and acetylation amid intestinal resizing. STAT92e, whose function is influenced by acetyl-CoA levels, was also identified as a key regulator of acyl-CoA and nutrient-dependent changes in stem cell activation. These findings define a regulatory mechanism, shaped by acyl-CoA metabolism, that adjusts proliferative homeostasis to coordinately regulate tissue plasticity during nutrient adaptation. | Mappin, F., Bellantuono, A. J., Ebrahimi, B., DeGennaro, M. (2023). Odor-evoked transcriptomics of Aedes aegypti mosquitoes. PLoS One, 18(10):e0293018 PubMed ID: 37874813
Summary: Modulation of odorant receptors mRNA induced by prolonged odor exposure is highly correlated with ligand-receptor interactions in Drosophila as well as mammals of the Muridae family. If this response feature is conserved in other organisms, this presents an intriguing initial screening tool when searching for novel receptor-ligand interactions in species with predominantly orphan olfactory receptors. This study demonstrates that mRNA modulation in response to 1-octen-3-ol odor exposure occurs in a time- and concentration-dependent manner in Aedes aegypti mosquitoes. To investigate gene expression patterns at a global level, an odor-evoked transcriptome was generated associated with 1-octen-3-ol odor exposure. Transcriptomic data revealed that ORs and OBPs were transcriptionally responsive whereas other chemosensory gene families showed little to no differential expression. Alongside chemosensory gene expression changes, transcriptomic analysis found that prolonged exposure to 1-octen-3-ol modulated xenobiotic response genes, primarily members of the cytochrome P450, insect cuticle proteins, and glucuronosyltransferases families. Together, these findings suggest that mRNA transcriptional modulation of olfactory receptors caused by prolonged odor exposure is pervasive across taxa and can be accompanied by the activation of xenobiotic responses. |
| Malik, D. M., Rhoades, S. D., Zhang, S. L., Sengupta, A., Barber, A., Haynes, P., Arnadottir, E. S., Pack, A., Kibbey, R. G., Sehgal, A., Weljie, A. M. (2023). Glucose Challenge Uncovers Temporal Fungibility of Metabolic Homeostasis Throughout the Day. bioRxiv, PubMed ID: 37961230
Summary: Rhythmicity is a central feature of behavioral and biological processes including metabolism, however, the mechanisms of metabolite cycling are poorly understood. A robust oscillation in a network of key metabolite pathways downstream of glucose is described in humans, then these pathways mechanistically probed through purpose-built (13)C(6)-glucose isotope tracing in Drosophila every 4h. A temporal peak in biosynthesis was noted by broad labelling of pathways downstream of glucose in wild-type flies shortly following lights on. Krebs cycle labelling was generally increased in a hyperactive mutant (fumin) along with glycolysis labelling primarily observed at dawn. Surprisingly, neither underlying feeding rhythms nor the presence of food explains the rhythmicity of glucose processing across genotypes. These results are consistent with clinical data demonstrating detrimental effects of mis-timed energy intake. This approach provides a window into the dynamic range of metabolic processing ability through the day and mechanistic basis for exploring circadian metabolic homeostasis in disease states. | Qiao, S., Bernasek, S., Gallagher, K. D., Yamada, S., Bagheri, N., Amaral, L. A. N., Carthew, R. W. (2023). Energy metabolism modulates the regulatory impact of activators on gene expression. bioRxiv, PubMed ID: 37961620
Summary: Gene expression is a regulated process fueled by ATP consumption. Therefore, regulation must be coupled to constraints imposed by the level of energy metabolism. This study explored this relationship both theoretically and experimentally. A stylized mathematical model predicts that activators of gene expression have variable impact depending on metabolic rate. Activators become less essential when metabolic rate is reduced and more essential when metabolic rate is enhanced. In the Drosophila eye, expression dynamics of the yan gene are less affected by loss of EGFR-mediated activation when metabolism is reduced, and the opposite effect is seen when metabolism is enhanced. The effects are also seen at the level of pattern regularity in the adult eye, where loss of EGFR-mediated activation is mitigated by lower metabolism. It is proposed that gene activation is tuned by energy metabolism to allow for faithful expression dynamics in the face of variable metabolic conditions. |
Monday, July 1st - Monday - Chromatin, DNA, and Chromosome Dynamics |
| Gemeinhardt, T. M., Regy, R. M., Mendiola, A. J., Ledterman, H. J., Henrickson, A., Phan, T. M., Kim, Y. C., Demeler, B., Kim, C. A., Mittal, J., Francis, N. J. (2023). How a disordered linker in the Polycomb protein Polyhomeotic tunes phase separation and oligomerization. bioRxiv, PubMed ID: 37961422
Summary: The Polycomb Group (PcG) complex PRC1 represses transcription, forms condensates in cells, and modifies chromatin architecture. These processes are connected through the essential, polymerizing Sterile Alpha Motif (SAM) present in the PRC1 subunit Polyhomeotic (Ph). In vitro, Ph SAM drives formation of short oligomers and phase separation with DNA or chromatin in the context of a Ph truncation ("mini-Ph"). Oligomer length is controlled by the long disordered linker (L) that connects the SAM to the rest of Ph--replacing Drosophila Ph linker (PhL) with the evolutionarily diverged human PHC3L strongly increases oligomerization. How the linker controls SAM polymerization, and how polymerization and the linker affect condensate formation are not know. This analyzed PhL and PHC3L using biochemical assays and molecular dynamics (MD) simulations. PHC3L promotes mini-Ph phase separation and makes it relatively independent of DNA. In MD simulations, basic amino acids in PHC3L form contacts with acidic amino acids in the SAM. Engineering the SAM to make analogous charge-based contacts with PhL increased polymerization and phase separation, partially recapitulating the effects of the PHC3L. Ph to PHC3 linker swaps and SAM surface mutations alter Ph condensate formation in cells, and Ph function in Drosophila imaginal discs. Thus, SAM-driven phase separation and polymerization are conserved between flies and mammals, but the underlying mechanisms have diverged through changes to the disordered linker. | Shaukat, A., Bakhtiari, M. H., Chaudhry, D. S., Khan, M. H. F., Akhtar, J., Abro, A. H., Haseeb, M. A., Sarwar, A., Mazhar, K., Umer, Z., Tariq, M. (2024). Mask exhibits trxG-like behavior and associates with H3K27ac marked chromatin. Dev Biol, 505:130-140 PubMed ID: 37981061
Summary: The Trithorax group (trxG) proteins counteract the repressive effect of Polycomb group (PcG) complexes and maintain transcriptional memory of active states of key developmental genes. Although chromatin structure and modifications appear to play a fundamental role in this process, it is not clear how trxG prevents PcG-silencing and heritably maintains an active gene expression state. This study reports a hitherto unknown role of Drosophila Multiple ankyrin repeats single KH domain (Mask), which emerged as one of the candidate trxG genes in our reverse genetic screen. The genome-wide binding profile of Mask correlates with known trxG binding sites across the Drosophila genome. In particular, the association of Mask at chromatin overlaps with CBP and H3K27ac, which are known hallmarks of actively transcribed genes by trxG. Importantly, Mask predominantly associates with actively transcribed genes in Drosophila. Depletion of Mask not only results in the downregulation of trxG targets but also correlates with diminished levels of H3K27ac. The fact that Mask positively regulates H3K27ac levels in flies was also found to be conserved in human cells. Strong suppression of Pc mutant phenotype by mutation in mask provides physiological relevance that Mask contributes to the anti-silencing effect of trxG, maintaining expression of key developmental genes. Since Mask is a downstream effector of multiple cell signaling pathways, it is proposed that Mask may connect cell signaling with chromatin mediated epigenetic cell memory governed by trxG. |
| Godneeva, B., Fejes Toth, K., Quan, B., Chou, T. F., Aravin, A. A. (2023). Impact of Germline Depletion of Bonus on Chromatin State in Drosophila Ovaries. Cells, 12(22) PubMed ID: 37998364
Summary: Gene expression is controlled via complex regulatory mechanisms involving transcription factors, chromatin modifications, and chromatin regulatory factors. Histone modifications, such as H3K27me3, H3K9ac, and H3K27ac, play an important role in controlling chromatin accessibility and transcriptional output. In vertebrates, the Transcriptional Intermediary Factor 1 (TIF1) family of proteins play essential roles in transcription, cell differentiation, DNA repair, and mitosis. This study focused on Bonus, the sole member of the TIF1 family in Drosophila, to investigate its role in organizing epigenetic modifications. The findings demonstrated that depleting Bonus in ovaries leads to a mild reduction in the H3K27me3 level over transposon regions and alters the distribution of active H3K9ac marks on specific protein-coding genes. Additionally, through mass spectrometry analysis, novel interacting partners of Bonus in ovaries were identifed, such as PolQ, providing a comprehensive understanding of the associated molecular pathways. Furthermore, this research revealed Bonus's interactions with the Polycomb Repressive Complex 2 and its co-purification with select histone acetyltransferases, shedding light on the underlying mechanisms behind these changes in chromatin modifications. | Golovnin, A., Melnikova, L., Babosha, V., Pokholkova, G. V., Slovohotov, I., Umnova, A., Maksimenko, O., Zhimulev, I. F., Georgiev, P. (2023). The N-Terminal Part of Drosophila CP190 Is a Platform for Interaction with Multiple Architectural Proteins. Int J Mol Sci, 24(21) PubMed ID: 37958900
Summary: CP190 is a co-factor in many Drosophila architectural proteins, being involved in the formation of active promoters and insulators. CP190 contains the N-terminal BTB/POZ (Broad-Complex, Tramtrack and Bric a brac/POxvirus and Zinc finger) domain and adjacent conserved regions involved in protein interactions. This study examined the functional roles of these domains of CP190 in vivo. The best-characterized architectural proteins with insulator functions, Pita, Su(Hw), and M1BP, Opbp, and ZIPIC, interacted with one or both of the highly conserved regions in the N-terminal part of CP190. Transgenic lines of D. melanogaster expressing CP190 mutants with a deletion of each of these domains were obtained. The results showed that these mutant proteins only partially compensated for the functions of CP190, weakly binding to selective chromatin sites. Further analysis confirmed the essential role of these domains in recruitment to regulatory regions associated with architectural proteins. The N-terminal of CP190 was found to be sufficient for recruiting Z4 and Chromator proteins and successfully achieving chromatin opening. Taken together, our results and the results of previous studies showed that the N-terminal region of CP190 is a platform for simultaneous interaction with various DNA-binding architectural proteins and transcription complexes. |
| Al Zouabi, L., Stefanutti, M., Roumeliotis, S., Le Meur, G., Boumard, B., Riddiford, N., Rubanova, N., Bohec, M., Gervais, L., Servant, N., Bardin, A. J. (2023). Chromatin state transitions in the Drosophila intestinal lineage identify principles of cell-type specification. Dev Cell, 58(24):3048-3063 PubMed ID: 38056452
Summary: Tissue homeostasis relies on rewiring of stem cell transcriptional programs into those of differentiated cells. This study investigate changes in chromatin occurring in a bipotent adult stem cells. Combining mapping of chromatin-associated factors with statistical modeling, genome-wide transitions during differentiation were identified in the adult Drosophila intestinal stem cell (ISC) lineage. Active, stem-cell-enriched genes transition to a repressive heterochromatin protein-1-enriched state more prominently in enteroendocrine cells (EEs) than in enterocytes (ECs), in which the histone H1-enriched Black state is preeminent. In contrast, terminal differentiation genes associated with metabolic functions follow a common path from a repressive, primed, histone H1-enriched Black state in ISCs to active chromatin states in EE and EC cells. Furthermore, Lineage priming was found to have an important function in adult ISCs, and histone H1 as a mediator of this process. These data define underlying principles of chromatin changes during adult multipotent stem cell differentiation. | Al Zouabi, L., Stefanutti, M., Roumeliotis, S., Le Meur, G., Boumard, B., Riddiford, N., Rubanova, N., Bohec, M., Gervais, L., Servant, N., Bardin, A. J. (2023). Molecular underpinnings and environmental drivers of loss of heterozygosity in Drosophila intestinal stem cells . Cell Rep 38032794
Summary: During development and aging, genome mutation leading to loss of heterozygosity (LOH) can uncover recessive phenotypes within tissue compartments. This phenomenon occurs in normal human tissues and is prevalent in pathological genetic conditions and cancers. While studies in yeast have defined DNA repair mechanisms that can promote LOH, the predominant pathways and environmental triggers in somatic tissues of multicellular organisms are not well understood. This study investigated mechanisms underlying LOH in intestinal stem cell in Drosophila. Infection with the pathogenic bacteria, Erwinia carotovora carotovora 15, but not Pseudomonas entomophila, increases LOH frequency. Using whole genome sequencing of somatic LOH events, it was demonstrated that they arise primarily via mitotic recombination. Molecular features and genetic evidence argue against a break-induced replication mechanism and instead support cross-over via double Holliday junction-based repair. This study provides a mechanistic understanding of mitotic recombination, an important mediator of LOH, and its effects on stem cells in vivo. |
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