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Current papers in developmental biology and gene function
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What's hot today
June 2025 May 2025 April 2025 March 2025 February 2025 January 2025 December 2024 November 2024 October 2024 September 2024 August 2024 July 2024 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 December 2022 December 2021 December 2020 December 2019 December 2018 | Lockyer, J. L., Reading, A., Vicenzi, S., Zbela, A., Viswanathan, S., Delandre, C., Newland, J. W., McMullen, J. P. D., Marshall, O. J., Gasperini, R., Foa, L., Lin, J. Y. (2024). Selective optogenetic inhibition of Gα(q) or Gα(i) signaling by minimal RGS domains disrupts circuit functionality and circuit formation. Proc Natl Acad Sci U S A, 121(36):e2411846121 PubMed ID: 39190348
Summary: Optogenetic techniques provide genetically targeted, spatially and temporally precise approaches to correlate cellular activities and physiological outcomes. In the nervous system, G protein-coupled receptors (GPCRs) have essential neuromodulatory functions through binding extracellular ligands to induce intracellular signaling cascades. This work developed and validated an optogenetic tool that disrupts Gα(q) signaling through membrane recruitment of a minimal regulator of G protein signaling (RGS) domain. This approach, Photo-induced Gα Modulator-Inhibition of Gα(q) (PiGM-Iq), exhibited potent and selective inhibition of Gα(q) signaling. Using PiGM-Iq the behavior of Caenorhabditis elegans and Drosophila was altered with outcomes consistent with GPCR-Gα(q) disruption. PiGM-Iq changes axon guidance in cultured dorsal root ganglia neurons in response to serotonin. PiGM-Iq activation leads to developmental deficits in zebrafish embryos and larvae resulting in altered neuronal wiring and behavior. Furthermore, by altering the minimal RGS domain, this study showed that this approach is amenable to Gα(i) signaling. This unique and robust optogenetic Gα inhibiting approaches complement existing neurobiological tools and can be used to investigate the functional effects neuromodulators that signal through GPCR and trimeric G proteins. | Luo, F., Zhang, C., Shi, Z., Mao, T., Jin, L. H. (2024). Notch signaling promotes differentiation, cell death and autophagy in Drosophila hematopoietic system.Insect biochemistry and molecular biology, 173:104176 PubMed ID: 39168254
Summary: Notch signaling is a highly conserved pathway between mammals and Drosophila and plays a key role in various biological processes. Drosophila has emerged as a powerful model for studying hematopoiesis and leukemia. In exception to crystal cells, the strength of Notch signaling in Drosophila lymph gland cortical zone (CZ)/intermediate zone (IZ) cells is weak. However, the influence of Notch activation in the lymph gland CZ/IZ cells and circulating hemocytes on hematopoietic homeostasis maintenance is unclear. In this study Notch activation in lymph gland CZ/IZ cells induced overdifferentiation of progenitors. Moreover, Notch activation promoted lamellocyte generation via NFκB/Toll signaling activation and increased reactive oxygen species (ROS). In addition, this study found that Notch activation in lymph gland CZ/IZ cells and circulating hemocytes caused caspase-independent and nonautophagic cell death. However, crystal cell autophagy was activated by upregulation of the expression of the target gene of the Hippo/Yki pathway Diap1. Moreover, t Notch activation could alleviate cytokine storms and improve the survival of Rasv12 leukemia model flies. This study revealed the various mechanisms of hematopoietic dysregulation induced by Notch activation in healthy flies and the therapeutic effect of Notch activation on leukemia model flies. |
| Akai, N., Yagi, Y., Igaki, T., Ohsawa, S. (2025). JNK signaling coordinates epithelial cell turnover through exocytosis in Drosophila ribosomal protein mutants. iScience, 28(6):112587 PubMed ID: 40510121
Summary: Robust tissue growth is orchestrated by the precise coordination of cell death and cell proliferation. In the developing wing pouches of Drosophila Minute/+ animals, both cell death and compensatory cell proliferation are increased, thereby contributing to robust growth of mutant tissue. This study shows that JNK-mediated elevation of exocytosis in dying cells is crucial for triggering cell turnover in M/+ wing morphogenesis. Mechanistically, elevated JNK signaling in dying cells upregulates exocytosis-related genes and Wingless (Wg), leading to enhanced Wg secretion. Notably, increased exocytosis promotes caspase activation via an exocytosisgs-Dronc amplification loop, sustaining apoptotic signaling while reinforcing Wg secretion through Dronc activation. Furthermore, this exocytosis-mediated Wg secretion and apoptotic feedback loop universally occurs downstream of JNK signaling, regardless of the genetic background. Overall, these findings provide mechanistic insights into robust tissue growth through the orchestration of cell turnover, primarily via JNK-mediated exocytosis during Drosophila Minute/+ wing morphogenesis. | Hertzler, J. i., Teng, J., Bernard, A. R., Stone, M. C., Kline, H. L., Mahata, G., Kumar, N., Rolls, M. M. (2024). Voltage-gated calcium channels act upstream of adenylyl cyclase Ac78C to promote timely initiation of dendrite regeneration. PLoS Genet, 20(8):e1011388 PubMed iD: 39186815
Summary: Most neurons are not replaced after injury and thus possess robust intrinsic mechanisms for repair after damage. Axon injury triggers a calcium wave, and calcium and cAMP can augment axon regeneration. in comparison to axon regeneration, dendrite regeneration is poorly understood. To test whether calcium and cAMP might also be involved in dendrite injury signaling, the responses of Drosophila dendritic arborization neurons to laser severing of axons and dendrites was tracted. Calcium and subsequently cAMP accumulate in the cell body after both dendrite and axon injury. Two voltage-gated calcium channels (VGCCs), L-Type and T-Type, are required for the calcium influx in response to dendrite injury and play a role in rapid initiation of dendrite regeneration. The AC8 family adenylyl cyclase, Ac78C, is required for cAMP production after dendrite injury and timely initiation of regeneration. Injury-induced cAMP production is sensitive to VGCC reduction, placing calcium upstream of cAMP generation. This study proposes that two VGCCs initiate global calcium influx in response to dendrite injury followed by production of cAMP by Ac78C. This signaling pathway promotes timely initiation of dendrite regrowth several hours after dendrite damage. |
| Choi, B. J., Chen, Y. C., Desplan, C. (2025). Retinal Calcium Waves Coordinate Uniform Tissue Patterning of the Drosophila Eye. bioRxiv, PubMed ID: 40501815
Summary: Optimal neural processing relies on precise tissue patterning across diverse cell types. This study shows that spontaneous calcium waves arise among non-neuronal support cells in the developing Drosophila eye to drive retinal morphogenesis. Waves are initiated by Cad96Ca receptor tyrosine kinase signaling, triggering PLCγ-mediated calcium release from the endoplasmic reticulum. A cell-type-specific 'Innexin-code' coordinates wave propagation through a defined gap junction network among non-neuronal retinal cells, excluding photoreceptors. Wave intensity scales with ommatidial size, triggering stronger Myosin II-driven apical contractions at interommatidial boundaries in larger ommatidia. This size-dependent mechanism compensates for early boundary irregularities, ensuring uniform ommatidial packing critical for precise optical architecture. These findings reveal how synchronized calcium signaling among non-neuronal cells orchestrates tissue patterning in the developing nervous system. | Yang, L., Zhu, A., Aman, J. M., Denberg, D., Kilwein, M. D., Marmion, R. A., Johnson, A. N. T., Veraksa, A., Singh, M., Wuhr, M., Shvartsman, S. Y. (2024). ERK synchronizes embryonic cleavages in Drosophila. Dev Cell, PubMed ID: 39208802
Summary: Extracellular-signal-regulated kinase (ERK) signaling controls development and homeostasis and is genetically deregulated in human diseases, including neurocognitive disorders and cancers. Although the list of ERK functions is vast and steadily growing, the full spectrum of processes controlled by any specific ERK activation event remains unknown. This study show howed ERK functions can be systematically identified using targeted perturbations and global readouts of ERK activation. In Drosophila embryos, where ERK signaling at the embryonic poles has thus far only been associated with the transcriptional patterning of the future larva. Through a combination of live imaging and phosphoproteomics, this study demonstrated that ERK activation at the poles is also critical for maintaining the speed and synchrony of embryonic cleavages. The presented approach to interrogating phosphorylation networks identifies a hidden function of a well-studied signaling event and sets the stage for similar studies in other organisms. |
Thursday July 26th - Disease Models |
| Favaro, M., Mauri, S., Bernardo, G., Zordan, M. A., Mazzotta, G. M., Ziviani, E. (2024). Usp14 down-regulation corrects sleep and circadian dysfunction of a Drosophila model of Parkinson's disease. Frontiers in neuroscience, 18:1410139 PubMed iD: 39161651
Summary: Parkinson's disease is a complex, multifactorial neurodegenerative disease, which occurs sporadically in aged population, with some genetically linked cases. Patients develop a very obvious locomotor phenotype, with symptoms such as bradykinesia, resting tremor, muscular rigidity, and postural instability. At the cellular level, PD pathology is characterized by the presence of intracytoplasmic neurotoxic aggregates of misfolded proteins and dysfunctional organelles, resulting from failure in mechanisms of proteostasis. Nonmotor symptoms, such as constipation and olfactory deficits, are also very common in PD. They include alteration in the circadian clock, and defects in the sleep-wake cycle, which is controlled by the clock. These non-motor symptoms precede the onset of the motor symptoms by many years, offering a window of therapeutic intervention that could delay-or even prevent-the progression of the disease. The mechanistic link between aberrant circadian rhythms and neurodegeneration in PD is not fully understood, although proposed underlying mechanisms include alterations in protein homeostasis (proteostasis), which can impact protein levels of core components of the clock. Loss of proteostasis depends on the progressive pathological decline in the proteolytic activity of two major degradative systems, the ubiquitin-proteasome and the lysosome-autophagy systems, which is exacerbated in age-dependent neurodegenerative conditions like PD. Accordingly, it is known that promoting proteasome or autophagy activity increases lifespan, and rescues the pathological phenotype of animal models of neurodegeneration, presumably by enhancing the degradation of misfolded proteins and dysfunctional organelles, which are known to accumulate in these models, and to induce intracellular damage. Proteostasis can be enhanced by pharmacologically inhibiting or down-regulating , a proteasome-associated deubiquitinating enzyme (DUB). in a previous work, it was shown that inhibition of Usp14 enhances the activity of the ubiquitin-proteasome system (UPS), autophagy and mitophagy, and abolishes motor symptoms of two well-established fly models of PD that accumulate dysfunctional mitochondria. This work extended the evidence on the protective effect of Usp14 down-regulation, and investigated the beneficial effect of down-regulating Usp14 in a Pink1 Drosophila model of PD that develop circadian and sleep dysfunction. Down-regulation of Usp14 ameliorates sleep disturbances and circadian defects that are associated to Pink1 KO flies. | Suarez, G. O., Kumar, D. S., Brunner, H., Emel, J., Teel, J., Knauss, A., Botero, V., Broyles, C. N., Stahl, A., Bidaye, S. S., Tomchik, S. M. (2024). Neurofibromin deficiency alters the patterning and prioritization of motor behaviors in a state-dependent manner. bioRxiv, PubMed ID: 39149363
Summary: Genetic disorders such as neurofibromatosis type 1 increase vulnerability to cognitive and behavioral disorders, such as autism spectrum disorder and attention-deficit/hyperactivity disorder. Neurofibromatosis type 1 results from loss-of-function mutations in the neurofibromin gene and subsequent reduction in the neurofibromin protein (Nf1). While the mechanisms have yet to be fully elucidated, loss of Nf1 may alter neuronal circuit activity leading to changes in behavior and susceptibility to cognitive and behavioral comorbidities. This study shows that mutations decreasing Nf1 expression alter motor behaviors, impacting the patterning, prioritization, and behavioral state dependence in a Drosophila model of neurofibromatosis type 1. Loss of Nf1 increases spontaneous grooming in a nonlinear spatial and temporal pattern, differentially increasing grooming of certain body parts, including the abdomen, head, and wings. This increase in grooming could be overridden by hunger in food-deprived foraging animals, demonstrating that the Nf1 effect is plastic and internal state-dependent. Stimulus-evoked grooming patterns were altered as well, with nf1 mutants exhibiting reductions in wing grooming when coated with dust, suggesting that hierarchical recruitment of grooming command circuits was altered. Yet loss of Nf1 in sensory neurons and/or grooming command neurons did not alter grooming frequency, suggesting that Nf1 affects grooming via higher-order circuit alterations. Changes in grooming coincided with alterations in walking. Flies lacking Nf1 walked with increased forward velocity on a spherical treadmill, yet there was no detectable change in leg kinematics or gait. Thus, loss of Nf1 alters motor function without affecting overall motor coordination, in contrast to other genetic disorders that impair coordination. Overall, these results demonstrate that loss of Nf1 alters the patterning and prioritization of repetitive behaviors, in a state-dependent manner, without affecting motor coordination. |
| Woodling, N. (2024). Sex- and strain-dependent effects of ageing on sleep and activity patterns in Drosophila. PLoS One, 19(8):e0308652 PubMed ID: 39150918
Summary: The fruit fly Drosophila is a major discovery platform in the biology of ageing due to its balance of relatively short lifespan and relatively complex physiology and behaviour. Previous studies have suggested that some important phenotypes of ageing, for instance increasingly fragmented sleep, are shared from humans to Drosophila and can be useful measures of behavioural change with age: these phenotypes therefore hold potential as readouts of healthy ageing for genetic or pharmacological interventions aimed at the underpinning biology of ageing. However, some age-related phenotypes in Drosophila show differing results among studies, leading to questions regarding the source of discrepancies among experiments. This study tested females and males from three common laboratory strains of Drosophila to determine the extent to which sex and background strain influence age-related behavioural changes in sleep and activity patterns. Surprisingly, some phenotypes, including age-related changes in total activity, total sleep, and sleep fragmentation, were found to depend strongly on sex and strain, to the extent that some phenotypes show opposing age-related changes in different sexes or strains. Conversely, other phenotypes were identified, including age-related decreases in morning and evening anticipation, that are more uniform across sexes and strains. These results reinforce the importance of controlling for background strain in both behavioural and ageing experiments, and they imply that caution should be used when drawing conclusions from studies on a single sex or strain of Drosophila. At the same time, these findings also offer suggestions for behavioural measures that merit further investigation as potentially more consistent phenotypes of ageing. | Ortiz-Vega, N., Lobato, A. G., Canic, T., Zhu, Y., Lazopulo, S., Syed, S., Zhai, R. G. (2024). Regulation of proteostasis by sleep through autophagy in Drosophila models of Alzheimer's disease. Life science alliance, 7(11) PubMed ID: 39237365
Summary: Sleep and circadian rhythm dysfunctions are common clinical features of Alzheimer's disease (AD). Increasing evidence suggests that in addition to being a symptom, sleep disturbances can also drive the progression of neurodegeneration. Protein aggregation is a pathological hallmark of AD; however, the molecular pathways behind how sleep affects protein homeostasis remain elusive. This study demonstrates that sleep modulation influences proteostasis and the progression of neurodegeneration in Drosophila models of tauopathy. This study shows that sleep deprivation enhanced Tau aggregational toxicity resulting in exacerbated synaptic degeneration. In contrast, sleep induction using gaboxadol led to reduced toxic Tau accumulation in neurons as a result of modulated autophagic flux and enhanced clearance of ubiquitinated Tau, suggesting altered protein processing and clearance that resulted in improved synaptic integrity and function. These findings highlight the complex relationship between sleep and regulation of protein homeostasis and the neuroprotective potential of sleep-enhancing therapeutics to slow the progression or delay the onset of neurodegeneration. |
| Ibrahim, R., Bahilo Martinez, M., Dobson, A. J. (2024). Rapamycin's lifespan effect is modulated by mito-nuclear epistasis in Drosophila. Aging Cell. 23(12):e14328. PubMed iD: 39225061
Summary: The macrolide drug rapamycin is a benchmark anti-ageing drug, which robustly extends lifespan of diverse organisms. For any health intervention, it is paramount to establish whether benefits are distributed equitably among individuals and populations, and ideally to match intervention to recipients' needs. However, how responses to rapamycin vary is surprisingly understudied. This study investigated how among-population variation in both mitochondrial and nuclear genetics shapes rapamycin's effects on lifespan. Epistatic "mito-nuclear" interactions, between mitochondria and nuclei, is shown to modulate the response to rapamycin treatment. Differences manifest as differential demographic effects of rapamycin, with altered age-specific mortality rate. However, a fitness cost of rapamycin early in life does not show a correlated response, suggesting that mito-nuclear epistasis can decouple costs and benefits of treatment. These findings suggest that a deeper understanding of how variation in mitochondrial and nuclear genomes shapes physiology may facilitate tailoring of anti-ageing therapy to individual need. | Deo, A., Ghosh, R., Ahire, S., Marathe, S., Majumdar, A., Bose, T. (2024). Two novel DnaJ chaperone proteins CG5001 and P58iPK regulate the pathogenicity of Huntington's disease related aggregates. Sci Rep, 14(1):20867 PubMed iD: 39242711
Summary: Huntington's disease (HD) is a rare neurodegenerative disease caused due to aggregation of Huntingtin (HTT) protein. This study involves the cloning of 40 http://flybase.org/reports/FBgg0000504">DnaJ chaperones from Drosophila, and overexpressing them in yeasts and fly models of HD. Accordingly, DnaJ chaperones were catalogued as enhancers or suppressors based on their growth phenotypes and aggregation properties. Two of the chaperones that came up as targets were CG5001 and P58iPK. Protein aggregation and slow growth phenotype was rescued in yeasts, S2 cells, and Drosophila transgenic lines of HTT103Q with these overexpressed chaperones. Since DnaJ chaperones have protein sequence similarity across species, they can be used as possible tools to combat the effects of neurodegenerative diseases. |
Thursday July 16th - Evolution |
| Guo, D., Xu, W., Cui, T., Rong, Q., Wu, Q. (2024). Protein-coding circular RNA enhances antiviral immunity via JAK/STAT pathway in Drosophila. mBio:e0146924 PubMed ID: 39158293
Summary: RNA interference (RNAi) drives powerful antiviral immunity in plants and animals so that many viruses must express viral suppressor of RNAi (VSR) to establish virulent infection. However, little is known about the immune responses conferring resistance against viruses that have evolved the counter-defensive strategy to suppress antiviral RNAi. This study discover that Drosophila cells infected with Drosophila C virus (DCV), a natural viral pathogen of Drosophila known to harbor a potent VSR, exhibit heightened expression of circular RNA circZfh1. circZfh1 confers virus resistance in the presence of viral suppression of antiviral RNAi. Furthermore, This study validate that circZfh1 encodes a 274-amino acid protein, CRAV, essential for its antiviral activity. Notably, CRAV differs from its parental Zfh1 gene in a different reading frame, with the C-terminal 69 amino acids unique to CRAV. This analysis also reveals the presence of CRAV in species within the melanogaster subgroup, with the C-terminal unique fragment undergoing accelerated evolution. Expression of CRAV upregulates the expression of the cytokine Upd3, which binds to its receptor, stimulating the JAK-STAT pathway and enhancing the immune response to DCV infection. Notably, CRISPR/Cas9 knockout of circZfh1 significantly enhances DCV replication in vitro and in vivo, with circZfh1-knockout adult flies displaying heightened disease susceptibility to DCV. In summary, these findings unveil a Drosophila protein-coding circular RNA that activates an innate immune signaling pathway crucial for virus resistance following the suppression of antiviral RNAi by viruses, thereby elucidating a novel counter-defensive strategy. | Lin, L., Huang, Y., McIntyre, J., Chang, C. H., Colmenares, S., Lee, Y. C. G. (2024). Prevalent fast evolution of genes involved in heterochromatin functions. Mol Biol Evol, PubMed ID: 39189646
Summary: Heterochromatin is a gene-poor and repeat-rich genomic compartment universally found in eukaryotes. Despite its low transcriptional activity, heterochromatin plays important roles in maintaining genome stability, organizing chromosomes, and suppressing transposable elements (TEs). Given the importance of these functions, it is expected that the genes involved in heterochromatin regulation would be highly conserved. Yet, a handful of these genes were found to evolve rapidly. To investigate whether these previous findings are anecdotal or general to genes modulating heterochromatin, an exhaustive list was compiled of 106 candidate genes involved in heterochromatin functions, and their evolution over short and long evolutionary time scales was investigate in Drosophila. Tmese analyses find that these genes exhibit significantly more frequent evolutionary changes, both in the forms of amino acid substitutions and gene copy number change, when compared to genes involved in Polycomb-based repressive chromatin. While positive selection drives amino acid changes within both structured domains with diverse functions and intrinsically disordered regions (IDRs), purifying selection may have maintained the proportions of IDRs of these proteins. Together with the observed negative associations between evolutionary rates of these genes and genomic TE abundance, an evolutionary model is proposed where the fast evolution of genes involved in heterochromatin functions is an inevitable outcome of the unique functional roles of heterochromatin, while the rapid evolution of TEs may be an effect rather than cause. This study provides an important global view of the evolution of genes involved in this critical cellular domain and provides insights into the factors driving the distinctive evolution of heterochromatin. |
| Berardi, S., Rhodes, J. A., Berner, M. C., Greenblum, S. I., Bitter, M. C., Behrman, E. L., βncourt, N. J., Bergland, A. O., Petrov, D. A., Rajpurohit, S., Schmidt, P. (2024). Drosophila melanogaster pigmentation demonstrates adaptive phenotypic parallelism but genomic unpredictability over multiple timescales. bioRxiv, PubMed ID: 39211235
Summary: Populations are capable of responding to environmental change over ecological timescales via adaptive tracking. However, the translation from patterns of allele frequency change to rapid adaptation of complex traits remains unresolved. This study used abdominal pigmentation in Drosophila melanogaster as a model phenotype to address the nature, genetic architecture, and repeatability of rapid adaptation in the field. D. melanogaster pigmentation was shown to evolve as a highly parallel and deterministic response to shared environmental gradients across latitude and season in natural North American populations. Then, experimentally evolved replicate, genetically diverse fly populations in field mesocosms were used to remove any confounding effects of demography and/or cryptic structure that may drive patterns in wild populations; this study showed that pigmentation rapidly responds, in parallel, in fewer than ten generations. Thus, pigmentation evolves concordantly in response to spatial and temporal climatic gradients. Next, whether phenotypic differentiation was associated with allele frequency change at loci with established links to genetic variance in pigmentation was examined in natural populations. Across all spatial and temporal scales, phenotypic patterns were associated with variation at pigmentation-related loci, and the sets of genes identified in each context were largely nonoverlapping. Therefore, these findings suggest that parallel phenotypic evolution is associated with an unpredictable genomic response, with distinct components of the polygenic architecture shifting across each environmental gradient to produce redundant adaptive patterns. | Kristensen, T. N., Schonherz, A. A., Rohde, P. D., Sorensen, J. G., Loeschcke, V. (2024). Selection for stress tolerance and longevity in Drosophila melanogaster have strong impacts on microbiome profiles. Sci Rep, 14(1):17789 PubMed ID: 39090347
Summary: There is experimental evidence that microbiomes have a strong influence on a range of host traits. Understanding the basis and importance of symbiosis between host and associated microorganisms is a rapidly developing research field, and there is still a lack of mechanistic understanding of ecological and genetic pressures affecting host-microbiome associations. In this study Drosophila melanogaster lines from a large-scale artificial selection experiment were used to investigate whether the microbiota differ in lines selected for different stress resistance traits and longevity. Following multiple generations of artificial selection all selection regimes and corresponding controls had their microbiomes assessed. The microbiome was interrogated based on 16S rRNA sequencing. The microbiome of flies from the different selection regimes differed markedly from that of the unselected control regime, and microbial diversity was consistently higher in selected relative to control regimes. Several common Drosophila bacterial species showed differentially abundance in the different selection regimes despite flies being exposed to similar environmental conditions for two generations prior to assessment. These findings provide strong evidence for symbiosis between host and microbiomes, but this study cannot reveal whether the interactions are adaptive, nor whether they are caused by genetic or ecological factors. |
| Li, X. C., Srinivasan, V., Laiker, I., Misunou, N., Frankel, N., Pallares, L. F., Crocker, J. (2024). TTF-High-Evolutionary: In Vivo Mutagenesis of Gene Regulatory Networks for the Study of the Genetics and Evolution of the Drosophila Regulatory Genome. Mol Biol Evol, 41(8) PubMed ID: 39117360
Summary: Understanding the evolutionary potential of mutations in gene regulatory networks is essential to furthering the study of evolution and development. However, in multicellular systems, genetic manipulation of regulatory networks in a targeted and high-throughput way remains challenging. In this study, TF-High-Evolutionary (HighEvo), a transcription factor (TF) fused with a base editor (activation-induced deaminase), was designed to continuously induce germline mutations at TF-binding sites across regulatory networks in Drosophila. Populations of flies expressing TF-HighEvo in their germlines accumulated mutations at rates an order of magnitude higher than natural populations. Importantly, these mutations accumulated around the targeted TF-binding sites across the genome, leading to distinct morphological phenotypes consistent with the developmental roles of the tagged TFs. As such, this TF-HighEvo method allows the interrogation of the mutational space of gene regulatory networks at scale and can serve as a powerful reagent for experimental evolution and genetic screens focused on the regulatory genome. | Bladen, J., Nam, H. J., Phadnis, N. (2024). Transformation of meiotic drive into hybrid sterility in Drosophila. Genetics, PubMed iD: 39196789
Summary: Hybrid male sterility is one of the fastest evolving intrinsic reproductive barriers between recently isolated populations. A leading explanation for the evolution of hybrid male sterility involves genomic conflicts with meiotic drivers in the male germline. There are, however, few examples directly linking meiotic drive to hybrid sterility. This study reports that the Sex-Ratio chromosome of Drosophila pseudoobscura, which causes X-chromosome drive within the USA subspecies, causes near-complete male sterility when it is moved into the genetic background of the Bogota subspecies. in addition, this new form of sterility was shown to be genetically distinct from the sterility of F1 hybrid males in crosses between USA males and Bogota females. These observations provide a tractable study system where noncryptic drive within species is transformed into strong hybrid sterility between very young subspecies. |
Thursday July 17th - Vesicles and Cytoskeleton |
| Zhang, X., Avellaneda, J., Spletter, M. L., Lemke, S. B., Mangeol, P., Habermann, B. H., Schnorrer, F. (2024). Mechanoresponsive regulation of myogenesis by the force-sensing transcriptional regulator Tono. Curr Biol, PubMed ID: 39163855
Summary: Muscle morphogenesis is a multi-step program, starting with myoblast fusion, followed by myotube-tendon attachment and sarcomere assembly, with subsequent sarcomere maturation, mitochondrial amplification, and specialization. The correct chronological order of these steps requires precise control of the transcriptional regulators and their effectors. How this regulation is achieved during muscle development is not well understood. In a genome-wide RNAi screen in Drosophila, this study identified the BTB-zinc-finger protein Tono (CG32121) as a muscle-specific transcriptional regulator. tono mutant flight muscles display severe deficits in mitochondria and sarcomere maturation, resulting in uncontrolled contractile forces causing muscle rupture and degeneration during development. Tono protein is expressed during sarcomere maturation and localizes in distinct condensates in flight muscle nuclei. Interestingly, internal pressure exerted by the maturing sarcomeres deforms the muscle nuclei into elongated shapes and changes the Tono condensates, suggesting that Tono senses the mechanical status of the muscle cells. Indeed, external mechanical pressure on the muscles triggers rapid liquid-liquid phase separation of Tono utilizing its BTB domain. Thus, it is proposed that Tono senses high mechanical pressure to adapt muscle transcription, specifically at the sarcomere maturation stages. Consistently, tono mutant muscles display specific defects in a transcriptional switch that represses early muscle differentiation genes and boosts late ones. It is hypothesized that a similar mechano-responsive regulation mechanism may control the activity of related BTB-zinc-finger proteins that, if mutated, can result in uncontrolled force production in human muscle. | Kos, P., Baumann, O. (2024). Spatial arrangement, polarity, and posttranslational modifications of the microtubule system in the Drosophila eye. Cell and tissue research, PubMed ID: 39152365 PMID
Summary: This study examined the organization of the microtubule system in photoreceptor cells and pigment cells within the adult Drosophila compound eye. Immunofluorescence localization of tubulin and of Short stop, a spectraplakin that has been reported to be involved in the anchorage of microtubule minus ends at the membrane, suggests the presence of non-centrosomal microtubule-organizing centers at the distal tip of the visual cells. Ultrastructural analyses confirm that microtubules emanate from membrane-associated plaques at the site of contact with cone cells and that all microtubules are aligned in distal-proximal direction within the photoreceptor cells. Determination of microtubule polarities demonstrated that about 95% of the microtubules in photoreceptor cells are oriented with their plus end in the direction of the synapse. Pigment cells in the eye contain only microtubules aligned in distal-proximal direction, with their plus end pointing towards the retinal floor. There, two populations of microtubules can be distinguished, single microtubules and bundled microtubules, the latter associated with actin filaments. Whereas microtubules in both photoreceptor cells and pigment cells are acetylated and mono/bi-glutamylated on α-tubulin, bundled microtubules in pigment cells are apparently also mono/bi-glutamylated on &β;-tubulin, providing the possibility of binding different microtubule-associated proteins. |
| Niwa, S., Watanabe, T., Chiba, K. (2024). The FHA domain is essential for the autoinhibition of KIF1A/UNC-104. J Cell Sci, PubMed ID: 39239883
Summary: KIF1A/UNC-104, a member of the kinesin superfamily motor proteins, plays a pivotal role in the axonal transport of synaptic vesicles and their precursors. Drosophila melanogaster UNC-104 (DmUNC-104) is a relatively recently discovered Drosophila kinesin. Although some point mutations that disrupt synapse formation have been identified, the biochemical properties of DmUNC-104 protein have not been investigated. Recombinant full-length DmUNC-104 protein was prepared and its biochemical features were determined. The effect was anayzed of a previously identified missense mutation in the forkhead-associated (FHA) domain, called bristly (bris). The bris mutation strongly promoted the dimerization of DmUNC-104 protein, whereas wild-type DmUNC-104 was a mixture of monomers and dimers. The G618R mutation near the FHA domain which was previously shown to disrupt the autoinhibition of C. elegans UNC-104. The biochemical properties of the G618R mutant recapitulated those of the bris mutant. Finally, this study found that disease-associated mutations also promote the dimerization of DmUNC-104. Collectively, this results suggest that the FHA domain is essential for the autoinhibition of KIF1A/UNC-104, and that abnormal dimerization of KIF1A is linked to human diseases. | Zein-Sabatto, H., Brockett, J. S., Jin, L., Husbands, C. A., Lee, J., Fang, J., Buehler, J., Bullock, S. L., Lerit, D. A. (2024). Centrocortin potentiates co-translational localization of its mRNA to the centrosome via dynein. bioRxiv, PubMed ID: 39149256
Summary: Centrosomes rely upon proteins within the pericentriolar material to nucleate and organize microtubules. Several mRNAs also reside at centrosomes, although less is known about how and why they accumulate there. Previous studies showed that local Centrocortin (Cen) mRNA supports centrosome separation, microtubule organization, and viability in Drosophila embryos. Using Cen mRNA as a model, this study examined mechanisms of centrosomal mRNA localization. While the Cen N'-terminus is sufficient for protein enrichment at centrosomes, multiple domains cooperate to concentrate Cen mRNA at this location. This study further identified an N'-terminal motif within Cen that is conserved among dynein cargo adaptor proteins, and its contribution to RNA localization was assessed. These results support a model whereby Cen protein enables the accumulation of its own mRNA to centrosomes through a mechanism requiring active translation, microtubules, and the dynein motor complex. Taken together, these data uncover the basis of translation-dependent localization of a centrosomal RNA required for mitotic integrity. |
| Voelzmann, A., Nuhu-Soso, L., Roof, A., Patel, S., Bennett, H., Adamson, A., Bentley, M., Evans, G. J. O., Hahn, I. (2025). GSK-3β coordinates axonal microtubule organisation through Shot and Tau. bioRxiv, PubMed ID: 40654684
Summary: Glycogen Synthase Kinase 3β (GSK-3β) is a key coordinator of neuronal development and maintenance; hyperactive GSK-3β is linked to neurodevelopmental and -degenerative diseases and therefore a promising therapeutic target. In neurons, GSK-3β coordinates the cytoskeleton by phosphorylating microtubule-binding proteins. This study found that tight regulation of GSK-3β kinase activity is required for the maintenance of parallel microtubule bundles in Drosophila and rat axons. Up- or down-regulation of GSK-3β led to axons forming pathological swellings in which microtubule bundles disintegrated into disorganised, curled microtubules. The microtubule bundling proteins Shot and Tau were identified as key GSK-3β targets, and GSK-3β was found to exert its regulatory effect on microtubule bundling through them. GSK-3β regulates the ability of Shot and Tau to attach to microtubules and/or the plus-end protein Eb1. Mis-regulation of GSK-3β leads to the loss of Eb1-Shot-mediated guidance of polymerising microtubules into parallel bundles, thus causing disorganisation. Microtubule disorganisation is proposed as a new explanation for how GSK-3β hyperactivity leads to neurodegeneration and why global inhibition of GSK-3β has not been successful in clinical trials for neuronal disorders. | Delaney, M., Zhao, Y., van de Leemput, J., Lee, H., Han, Z. (2024). Actin Cytoskeleton and Integrin Components Are Interdependent for Slit Diaphragm Maintenance in Drosophila Nephrocytes. Cells, 13(16) PubMed ID: 39195240
Summary: In nephrotic syndrome, the podocyte filtration structures are damaged in a process called foot process effacement. This is mediated by the actin cytoskeleton; however, which actins are involved and how they interact with other filtration components, like the basement membrane, remains poorly understood. This study used the well-established Drosophila pericardial nephrocyte-the equivalent of podocytes in flies-knockdown models (RNAi) to study the interplay of the actin cytoskeleton (Act5C, Act57B, Act42A, and Act87E), alpha- and β-integrin (basement membrane), and the slit diaphragm (Sns and Pyd). Knockdown of an actin gene led to variations of formation of actin stress fibers, the internalization of Sns, and a disrupted slit diaphragm cortical pattern. Notably, deficiency of Act5C, which resulted in complete absence of nephrocytes, could be partially mitigated by overexpressing Act42A or Act87E, suggesting at least partial functional redundancy. Integrin localized near the actin cytoskeleton as well as slit diaphragm components, but when the nephrocyte cytoskeleton or slit diaphragm was disrupted, this switched to colocalization, both at the surface and internalized in aggregates. Altogether, the data show that the interdependence of the slit diaphragm, actin cytoskeleton, and integrins is key to the structure and function of the Drosophila nephrocyte. |
Tuesday July 15th - Stress |
| Herranz, H., Ye, Z., Olsen, J. V., Li, Y., Nygaard, M., Christensen, K., Tong, X., Bohr, V. A., Rasmussen, L. J., Dai, F. (2024). FOXO-regulated OSER1 reduces oxidative stress and extends lifespan in multiple species.. Nat Commun, 15(1):7144 PubMed ID: 39164296
Summary: FOXO transcription factors modulate aging-related pathways and influence longevity in multiple species, but the transcriptional targets that mediate these effects remain largely unknown. This study identified an evolutionarily conserved FOXO target gene, Oxidative stress-responsive serine-rich protein 1 (OSER1), whose overexpression extends lifespan in silkworms, nematodes, and flies, while its depletion correspondingly shortens lifespan. In flies, overexpression of OSER1 increases resistance to oxidative stress, starvation, and heat shock, while OSER1-depleted flies are more vulnerable to these stressors. In silkworms, hydrogen peroxide both induces and is scavenged by OSER1 in vitro and in vivo. Knockdown of OSER1 in Caenorhabditis elegans leads to increased ROS production and shorter lifespan, mitochondrial fragmentation, decreased ATP production, and altered transcription of mitochondrial genes. Human proteomic analysis suggests that OSER1 plays roles in oxidative stress response, cellular senescence, and reproduction, which is consistent with the data and suggests that OSER1 could play a role in fertility in silkworms and nematodes. Human studies demonstrate that polymorphic variants in OSER1 are associated with human longevity. In summary, OSER1 is an evolutionarily conserved FOXO-regulated protein that improves resistance to oxidative stress, maintains mitochondrial functional integrity, and increases lifespan in multiple species. Additional studies will clarify the role of OSER1 as a critical effector of healthy aging. | Fulton, T. L., Johnstone, J. N., Tan, J. J., Balagopal, K., Dedman, A., Chan, A. Y., Johnson, T. K., Mirth, C. K., Piper, M. D. W. (2024). Transiently restricting individual amino acids protects Drosophila melanogaster against multiple stressors. Open biology, 14(8):240093 PubMed ID: 39106944
Summary: Nutrition and resilience are linked, though it is not yet clear how diet confers stress resistance or the breadth of stressors that it can protect against. Previous WORK shoD that transiently restricting an essential amino acid can protect Drosophila melanogaster against nicotine poisoning. This study sought to characterize the nature of this dietary-mediated protection and determine whether it was sex, amino acid and/or nicotine specific. When between sexes were compared, isoleucine deprivation was found to increases female, but not male, nicotine resistance. Surprirsingly, it was found that this protection afforded to females was not replicated by dietary protein restriction and was instead specific to individual amino acid restriction. To understand whether these beneficial effects of diet were specific to nicotine or were generalizable across stressors, flies were pre-treated with amino acid restriction diets and then exposed to other types of stress. Some of ome of the diets protected against nicotine also protected against oxidative and starvation stress, and improved survival following cold shock. Interestingly, it was found that a diet lacking isoleucine was the only diet to protect against all these stressors. These data point to isoleucine as a critical determinant of robustness in the face of environmental challenges. |
| Glineburg, M. R., Yildirim, E., Gomez, N., Rodriguez, G., Pak, J., Li, X., Altheim, C., Waksmacki, J., McInerney, G. M., Barmada, S. J., Todd, P. K. (2024). Stress granule formation helps to mitigate neurodegeneration. Nucleic Acids Res, PubMed ID: 39106168
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 6G3BP 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. | Esteban-Collado, J., Fernandez-Manas, M., Fernandez-Moreno, M., Maeso, I., Corominas, M., Serras, F. (2024). Reactive oxygen species activate the Drosophila TNF receptor Wengen for damage-induced regeneration. The EMBO journal, 43(17):3604-3626 PubMed ID: 39020149
Summary: Tumor necrosis factor receptors (TNFRs) control pleiotropic pro-inflammatory functions that range from apoptosis to cell survival. The ability to trigger a particular function will depend on the upstream cues, association with regulatory complexes, and downstream pathways. In Drosophila melanogaster, two TNFRs have been identified, Wengen (Wgn) and Grindelwald (Grnd). Although several reports associate these receptors with JNK-dependent apoptosis, it has recently been found that Wgn activates a variety of other functions. This study demonstrates that Wgn is required for survival by protecting cells from apoptosis. This is mediated by dTRAF1 and results in the activation of p38 MAP kinase. Remarkably, Wgn is required for apoptosis-induced regeneration and is activated by the reactive oxygen species (ROS) produced following apoptosis. This ROS activation is exclusive for Wgn, but not for Grnd, and can occur after knocking down Eiger/TNFα. The extracellular cysteine-rich domain of Grnd is much more divergent than that of Wgn, which is more similar to TNFRs from other animals, including humans. These results show a novel TNFR function that responds to stressors by ensuring p38-dependent regeneration. |
| Sun, X., Zhou, D., Sun, Y., Zhao, Y., Deng, Y., Pang, X., Liu, Q., Zhou, Z. (2024). Oxidative stress reprograms the transcriptional coactivator Yki to suppress cell proliferation. Cell Rep, 43(8):114584 PubMed ID: 39106181
Summary: The transcriptional coactivator Yorkie (Yki) regulates organ size by promoting cell proliferation. It is unclear how cells control Yki activity when exposed to harmful stimuli such as oxidative stress. This study shows that oxidative stress inhibits the binding of Yki to Scalloped (Sd) but promotes the interaction of Yki with another transcription factor, forkhead box O (Foxo), ultimately leading to a halt in cell proliferation. Mechanistically, Foxo normally exhibits a low binding affinity for Yki, allowing Yki to form a complex with Sd and activate proliferative genes. Under oxidative stress, Usp7 deubiquitinates Foxo to promote its interaction with Yki, thereby activating the expression of proliferation suppressors. Finally, Yki was shown to be essential for Drosophila survival under oxidative stress. In summary, these findings suggest that oxidative stress reprograms Yki from a proliferation-promoting factor to a proliferation suppressor, forming a self-protective mechanism. | Camilleri-Robles, C., Climent-Canto, P., Llorens-Giralt, P., Klein, C. C., Serras, F., Corominas, M. (2024). A shift in chromatin binding of phosphorylated p38 precedes transcriptional changes upon oxidative stress. FEBS letters, PubMed ID: 39218622
Summary: P38 mitogen-activated protein kinases are key in the regulation of the cellular response to stressors. P38 is known to regulate transcription, mRNA processing, stability, and translation. The transcriptional changes mediated by phosphorylated p38 (P-p38) in response to extracellular stimuli have been thoroughly analyzed in many tissues and organisms. However, the genomic localization of chromatin-associated P-p38 remains poorly understood. This study analyzed the chromatin binding of activated P-p38 and its role in the response to reactive oxygen species (ROS) in Drosophila S2 cells. P-p38 was found to be already bound to chromatin in basal conditions. After ROS exposure, chromatin-associated P-p38 relocates towards genes involved in the recovery process. These findings highlight the role of P-p38 dynamic chromatin binding in orchestrating gene expression responses to oxidative stress. |
Friday July 11th - Gonads |
| Fang, Y., Zhang, F., Zhao, F., Wang, J., Cheng, X., Ye, F., He, J., Zhao, L., Su, Y. (2024). RpL38 modulates germ cell differentiation by controlling Bam expression in Drosophila testis. Science China Life sciences, PubMed ID: 39187660
Summary: Switching from mitotic spermatogonia to meiotic spermatocytes is critical to producing haploid sperms during male germ cell differentiation. However, the underlying mechanisms of this switch remain largely unexplored. In Drosophila melanogaster, the gene RpL38 encodes the ribosomal protein L38, one component of the 60S subunit of ribosomes. Its depletion in spermatogonia was found to severely diminished the production of mature sperms and thus led to the infertility of male flies. By examining the germ cell differentiation in testes, RpL38-knockdown was found to block the transition from spermatogonia to spermatocytes and accumulated spermatogonia in the testis. To understand the intrinsic reason for this blockage, proteomic analysis was conducted for these spermatogonia populations. Differing from the control spermatogonia, the accumulated spermatogonia in RpL38-knockdown testes already expressed many spermatocyte markers but lacked many meiosis-related proteins, suggesting that spermatogonia need to prepare some important proteins for meiosis to complete their switch into spermatocytes. Mechanistically, the expression of bag of marbles (bam), a crucial determinant in the transition from spermatogonia to spermatocytes, was found to be inhibited at both the mRNA and protein levels upon RpL38 depletion. The bam loss phenocopied RpL38 RNAi in the testis phenotype and transcriptomic profiling. Strikingly, overexpressing bam was able to fully rescue the testis abnormality and infertility of RpL38-knockdown flies, indicating that bam is the key effector downstream of RpL38 to regulate spermatogonia differentiation. Overall, these data suggested that germ cells start to prepare meiosis-related proteins as early as the spermatogonial stage, and RpL38 in spermatogonia is required to regulate their transition toward spermatocytes in a bam-dependent manner, providing new knowledge for understanding of the transition process from spermatogonia to spermatocytes in Drosophila spermatogenesis. | Mahmoudzadeh, N. H., Heidarian, Y., Tourigny, J. P., Fitt, A. J., Beebe, K., Li, H., Luhur, A., Buddika, K., Mungcal, L., Kundu, A., Policastro, R. A., Brinkley, G. J., Zentner, G. E., Nemkov, T., Pepin, R., Chawla, G., Sudarshan, S., Rodan, A. R., D'Alessandro, A., Tennessen, J. M. (2024). Renal L-2-hydroxyglutarate dehydrogenase activity promotes hypoxia tolerance and mitochondrial metabolism in Drosophila melanogaster. Molecular metabolism, 89:102013 PubMed ID: 39182840
Summary: The mitochondrial enzyme L-2-hydroxyglutarate dehydrogenase (L2HGDH) regulates the abundance of L-2-hydroxyglutarate (L-2HG), a potent signaling metabolite capable of influencing chromatin architecture, mitochondrial metabolism, and cell fate decisions. Loss of L2hgdh activity in humans induces ectopic L-2HG accumulation, resulting in neurodevelopmental defects, altered immune cell function, and enhanced growth of clear cell renal cell carcinomas. To better understand the molecular mechanisms that underlie these disease pathologies, the fruit fly Drosophila melanogaster was used to investigate the endogenous functions of L2hgdh. L2hgdh mutant adult male flies were analyzed under normoxic and hypoxic conditions using a combination of semi-targeted metabolomics and RNA-seq. These multi-omic analyses were complemented by tissue-specific genetic studies that examined the effects of L2hgdh mutations on the Drosophila renal system (Malpighian tubules; MTs). These studies revealed that while L2hgdh is not essential for growth or viability under standard culture conditions, LL2hgdhmutants are hypersensitive to hypoxia and expire during the reoxygenation phase with severe disruptions of mitochondrial metabolism. Moreover, this study found that the fly renal system is a key site of L2hgdh activity, as L2hgdh mutants that express a rescuing transgene within the MTs survive hypoxia treatment and exhibit normal levels of mitochondrial metabolites. Even under normoxic conditions, L2hgdh mutant MTs experience significant metabolic stress and are sensitized to aberrant growth upon Egfr activation. CONCLUSIONS: These findings present a model in which renal L2hgdh activity limits systemic L-2HG accumulation, thus indirectly regulating the balance between glycolytic and mitochondrial metabolism, enabling successful recovery from hypoxia exposure, and ensuring renal tissue integrity. |
| Buglak, D. B., Holmes, K. H. M., Galletta, B. J., Rusan, N. M. (2024). The proximal centriole-like structure maintains nucleus-centriole architecture in sperm. J Cell Sci, 137(17) PubMed ID: 39166297
Summary: Proper connection between the sperm head and tail is critical for sperm motility and fertilization. Head-tail linkage is mediated by the head-tail coupling apparatus (HTCA), which secures the axoneme (tail) to the nucleus (head). However, the molecular architecture of the HTCA is poorly understood. This study used Drosophila to investigate formation and remodeling of the HTCA throughout spermiogenesis by visualizing key components of this complex. Using structured illumination microscopy, Key HTCA proteins Spag4 and Yuri were shown to form a 'centriole cap' that surrounds the centriole (or basal body) as it invaginates into the surface of the nucleus. As development progresses, the centriole is laterally displaced to the side of the nucleus while the HTCA expands under the nucleus, forming what was termed the 'nuclear shelf'. The proximal centriole-like (PCL) structure is positioned under the nuclear shelf, functioning as a crucial stabilizer of centriole-nucleus attachment. Together, these data indicate that the HTCA is a complex, multi-point attachment site that simultaneously engages the PCL, the centriole and the nucleus to ensure proper head-tail connection during late-stage spermiogenesis. | Zhang, L., Ten Hagen, K. G. (2024). O-Glycosylation of a male seminal fluid protein influences sperm binding and female postmating behavior. PNAS nexus, 3(8):pgae322 PubMed ID: 39189023
Summary: Glycoproteins are abundant within the human reproductive system and alterations in glycosylation lead to reproductive disorders, suggesting that glycans play an important role in reproductive function. In this study, the Drosophila reproductive system was used as a model to investigate the biological functions of O-glycosylation. O-glycosylation in the male accessory glands, an organ responsible for secreting seminal fluid proteins, plays important roles in female postmating behavior. The loss of one O-glycosyltransferase, PGANT9, in the male reproductive system resulted in decreased egg production in mated females. One substrate of PGANT9 was detected, lectin-46Ca (CG1656), which is known to affect female postmating responses. Loss of lectin-46Ca O-glycosylation affects its ability to associate with sperm tails, resulting in reduced transfer within the female reproductive system. These results provide the first example that O-glycosylation of a seminal fluid protein affects its ability to associate with sperm in vivo. These studies may shed light on the biological function of O-glycans in mammalian reproduction. |
| Guay, S. Y., Patel, P. H., Thomalla, J. M., McDermott, K. L., O'Toole, J. M., Arnold, S. E., Obrycki, S. J., Wolfner, M. F., Findlay, G. D. (2024). A newly evolved gene is essential for efficient sperm entry into eggs in Drosophila melanogaster.bioRxiv, PubMed ID: 39149251
Summary: New genes arise through a variety of evolutionary processes and provide raw material for adaptation in the face of both natural and sexual selection. De novo evolved genes emerge from previously non-protein-coding DNA sequences, and many such genes are expressed in male reproductive structures. In Drosophila melanogaster, several putative de novo genes have evolved essential roles in spermatogenesis, but whether such genes can also impact sperm function beyond the male has not been investigated. This study identified a putative de novo gene, katherine johnson (kj; CG43167), that is required for high levels of male fertility. Males that do not express kj produce and transfer sperm that are stored normally in females, but sperm from these males enter eggs with severely reduced efficiency. Using a tagged transgenic rescue construct, KJ protein was observed to localize to the nuclear periphery in various stages of spermatogenesis, but is not detectable in mature sperm. These data suggest that kj exerts an effect on sperm development, the loss of which results in reduced fertilization ability. While previous bioinformatic analyses suggested the kj gene was restricted to the melanogaster group of Drosophila,putative orthologs with conserved synteny, male-biased expression, and predicted protein features were observed across the genus, as well as instances of gene loss in some lineages. Thus, kj potentially arose in the Drosophila common ancestor and subsequently evolved an essential role in D. melanogaster. These results demonstrate a new aspect of male reproduction that has been shaped by new gene evolution and provide a molecular foothold for further investigating the mechanism of sperm entry into eggs in Drosophila. | Kagemann, C. H., Colocho, G. M., Aquadro, C. F. (2024). Non-ovarian Wolbachia pipientis titer correlates with fertility rescue of a Drosophila melanogaster bag of marbles hypomorph. microPublication biology, 2024 PubMed ID: 39157806
Summary: Bag of marbles (bam<) is an essential gene that regulates germline stem cell maintenance and germline stem cell daughter cell differentiation in Drosophila melanogaster . When bam is partially functional (hypomorphic), the introduction of Wolbachia pipientis rescues the mutant fertility phenotype that would otherwise result in partial sterility. Infection by different W. pipientis variants results in differential rescue of the bam hypomorph fertility phenotype. The varying degrees of rescue exhibited in the bam hypomorph when exposed to different W. pipientis variants was intreguing, prompting an investigation into whether this phenomenon is attributable to variations in the titers of W. pipientis variants. No significant difference in ovarian titer was found between two W. pipientis variant groups, w Mel-like (low bam hypomorph fertility rescue) and w MelCS-like variants (higher bam hypomorph fertility rescue), at bam hypomorph peak fertility. However, carcass (whole flies without the ovaries) titer between w Mel-like and w MelCS-like infected bam hypomorph differed during peak fertility rescue. A positive correlation emerged between the combined titers of ovarian and carcass infections and fertility, implying a more extensive influence that extends beyond ovarian infection alone. |
Thursday July 10th - Enhancers and Transcriptional Regulation |
| Ke, W., Fujioka, M., Schedl, P., Jaynes, J. B. (2024). Stem-loop and circle-loop TADs generated by directional pairing of boundary elements have distinct physical and regulatory properties. Elife, 13 PubMed ID: 39110491
Summary: The chromosomes in multicellular eukaryotes are organized into a series of topologically independent loops called TADs. In flies, TADs are formed by physical interactions between neighboring boundaries. Fly boundaries exhibit distinct partner preferences, and pairing interactions between boundaries are typically orientation-dependent. Pairing can be head-to-tail or head-to-head. The former generates a stem-loop TAD, while the latter gives a circle-loop TAD. The TAD that encompasses the Drosophila even skipped (eve) gene is formed by the head-to-tail pairing of the nhomie and homie boundaries. To explore the relationship between loop topology and the physical and regulatory landscape, the nhomie boundary region was flanked with two attP sites. The attP sites were then used to generate four boundary replacements: λ DNA, nhomie forward (WT orientation), nhomie reverse (opposite of WT orientation), and homie forward (same orientation as WT homie). The nhomie forward replacement restores the WT physical and regulatory landscape: in MicroC experiments, the eve TAD is a 'volcano' triangle topped by a plume, and the eve gene and its regulatory elements are sequestered from interactions with neighbors. The λ DNA replacement lacks boundary function: the endpoint of the 'new' eve TAD on the nhomie side is ill-defined, and eve stripe enhancers activate a nearby gene, eIF3j. While nhomie reverse and homie forward restore the eve TAD, the topology is a circle-loop, and this changes the local physical and regulatory landscape. In MicroC experiments, the eve TAD interacts with its neighbors, and the plume at the top of the eve triangle peak is converted to a pair of 'clouds' of contacts with the next-door TADs. Consistent with the loss of isolation afforded by the stem-loop topology, the eve enhancers weakly activate genes in the neighboring TADs. Conversely, eve function is partially disrupted. | Glaser-Schmitt, A., Lemoine, M., Kaltenpoth, M., Parsch, J. (2024). Pervasive tissue-, genetic background-, and allele-specific gene expression effects in Drosophila melanogaster. PLoS Genet, 20(8):e1011257 PubMed ID: 39178312
Summary: The pervasiveness of gene expression variation and its contribution to phenotypic variation and evolution is well known. This gene expression variation is context dependent, with differences in regulatory architecture often associated with intrinsic and environmental factors, and is modulated by regulatory elements that can act in cis (linked) or in trans (unlinked) relative to the genes they affect. So far, little is known about how this genetic variation affects the evolution of regulatory architecture among closely related tissues during population divergence. To address this question, gene expression was analyzed in the midgut, hindgut, and Malpighian tubule as well as microbiome composition in the two gut tissues in four Drosophila melanogaster strains and their F1 hybrids from two divergent populations: one from the derived, European range and one from the ancestral, African range. In both the transcriptome and microbiome data, extensive tissue- and genetic background-specific effects were detected, including effects of genetic background on overall tissue specificity. Tissue-specific effects were typically stronger than genetic background-specific effects, although the two gut tissues were not more similar to each other than to the Malpighian tubules. An examination of allele specific expression revealed that, while both cis and trans effects were more tissue-specific in genes expressed differentially between populations than genes with conserved expression, trans effects were more tissue-specific than cis effects. Despite there being highly variable regulatory architecture, this observation was robust across tissues and genetic backgrounds, suggesting that the expression of trans variation can be spatially fine-tuned as well as or better than cis variation during population divergence and yielding new insights into cis and trans regulatory evolution. |
| Monastirioti, M., Koltsaki, I., Pitsidianaki, I., Skafida, E., Batsiotos, N., Delidakis, C. (2024). Notch-Dependent Expression of the Drosophila Hey Gene Is Supported by a Pair of Enhancers with Overlapping Activities. Genes, 15(8) PubMed ID: 39202431
Summary: Drosophila Hey is a basic helix-loop-helix-orange (bHLH-O) protein with an important role in the establishment of distinct identities of postmitotic cells. Previously Hey was identified as a transcriptional target and effector of Notch signalling during the asymmetric division of neuronal progenitors, generating neurons of two types, and Notch-dependent expression of Hey also marks a subpopulation of the newborn enteroendocrine (EE) cells in the midgut primordium of the embryo. This study investigated the transcriptional regulation of Hey in neuronal and intestinal tissues. Two genomic regions upstream of the promoter (HeyUP) and in the second intron (HeyIN2) of the Hey gene were isolated based on the presence of binding motifs for Su(H), the transcription factor that mediates Notch activity. Both regions can direct the overlapping expression patterns of reporter transgenes recapitulating endogenous Hey expression. Moreover, while HeyIN2 represents a Notch-dependent enhancer, HeyUP confers both Notch-dependent and independent transcriptional regulation. Mutations were induced that removed the Su(H) binding motifs in either region, and then the the enhancer functionality was studied in the respective Hey mutant lines. The results provide direct evidence that although both enhancers support Notch-dependent regulation of the Hey gene, their role is redundant, as a Hey loss-of-function lethal phenotype is observed only after deletion of all their Su(H) binding motifs by CRISPR/Cas9. | Villarreal-Puente, A., Altamirano-Torres, C., Jimenez-Mejia, G., Hernandez-Bautista, C., Montalvo-Mendez, R., Vazquez, M., Zurita, M., Resendez-Perez, D. (2024). Novel Antennapedia and Ultrabithorax trimeric complexes with TBP and Exd regulate transcription. Hereditas, 161(1):25 PubMed ID: 39080786
Summary: Hox proteins interact with DNA and many other proteins, co-factors, transcriptional factors, chromatin remodeling components, non-coding RNAs and even the extracellular matrix that assembles the Hox complexes. The number of interacting partners continues to grow with diverse components and more transcriptional factors than initially thought. Hox complexes present many activities, but their molecular mechanisms to modulate their target genes remain unsolved. This study showed the protein-protein interaction of Antp with Ubx through the homeodomain using BiFC in Drosophila. Analysis of Antp-deletional mutants showed that AntpHD helixes 1 and 2 are required for the interaction with Ubx. Also, a novel interaction of Ubx with TBP was found, in which the PolyQ domain of TBP is required for the interaction. Moreover, the formation of two new trimeric complexes of Antp with Ubx, TBP and Exd was found using BiFC-FRET; these proteins, however, do not form a trimeric interaction with BIP2 or TFIIEβ. The novel trimeric complexes reduced Antp transcriptional activity, indicating that they could confer specificity for repression. These results increase the number of transcriptional factors in the Antp and Ubx interactomes that form two novel trimeric complexes with TBP and Exd. A new Ubx interaction with TBP was also found. These novel interactions provide important clues of the dynamics of Hox-interacting complexes involved in transcriptional regulation, contributing to better understand Hox function. |
| Zhang, L., Hodgins, L., Sakib, S., Verbeem, A., Mahmood, A., Perez-Romero, C., Marmion, R. A., Dostatni, N., Fradin, C. (2024)s. Both the transcriptional activator, Bcd, and repressor, Cic, form small mobile oligomeric clusters. Biophys J, PubMed ID: 39164967
Summary: Transcription factors play an essential role in pattern formation during early embryo development, generating a strikingly fast and precise transcriptional response that results in sharp gene expression boundaries. To characterize the steps leading up to transcription, a side-by-side comparison was performed of the nuclear dynamics of two morphogens, a transcriptional activator, Bicoid (Bcd), and a transcriptional repressor, Capicua (Cic), both involved in body patterning along the anterior-posterior axis of the early Drosophila embryo. A combination of fluorescence recovery after photobleaching, fluorescence correlation spectroscopy, and single particle tracking was used to access a wide range of dynamical timescales. Despite their opposite effects on gene transcription, Bcd and Cic have very similar nuclear dynamics, characterized by the co-existence of a freely diffusing monomer population with a number of oligomeric clusters, which range from low stoichiometry and high mobility clusters to larger, DNA-bound hubs. These observations are consistent with the inclusion of both Bcd and Cic into transcriptional hubs or condensates, while putting constraints on the mechanism by which these form. These results fit in with the recent proposal that many transcription factors might share a common search strategy for target genes regulatory regions that makes use of their large unstructured regions, and may eventually help explain how the transcriptional response they elicit can be at the same time so fast and so precise. | Jalal, M. S., Duttaroy, A. (2024). Maternal Spargel/dPGC-1 is critical for embryonic development and influences chorion gene amplification via Cyclin E activity. Dev Biol, 516:158-166 PubMed ID: 39173813
Summary: The function of spargel/dPGC-1 in Drosophila oogenesis has been unequivocally established. This study sought to assess whether Spargel protein or RNA is essential for developmentally competent eggs. The trans-heterozygotic combination of two spargel mutant alleles allowed a decrease Spargel expression to very low levels. Using this model, this study demonstrated the requirement for Spargel in eggshell patterning and embryonic development, which led to the finding that spargel is a maternal effect gene. Further examination of Spargel's potential mechanism of action in eggshell biogenesis revealed that low levels of Spargel in the adult ovary cause diminished Cyclin E activity, resulting in reduced chorion gene amplification levels, leading to eggshell biogenesis defects. Thus, another novel role for Cyclin E/dPGC-1 is established whereby, through Cyclin E activity, this conserved transcriptional coactivator regulates the chorion gene amplification process. |
Wednesday July 9th - Adult Physiology and Metabolism |
| Chattopadhyay, D., Philip, S. M., Prabhakar, G., Machamada Bheemaiah, M. (2024). Influence of α-lipoic acid on longevity and stress resistance in Drosophila melanogaster fed with a high-fat diet. Biogerontology, PubMed ID: 39046586
Summary: Consumption of a high-fat diet is accompanied by the risks of obesity and early onset of age-associated complications for which dietary interventions are imperative to combat. α-lipoic acid has been shown to hinder diet-induced obesity and induce lifespan-extending efficacy in model organisms. In this study, α-lipoic acid was investigated for its efficacy in improving lifespan and stress resistance in the Canton-S strain of Drosophila melanogaster fed with a high-fat diet. Furthermore, as mating status significantly impacts survival in fruit flies, flies were reared in two experimental groups-group one, in which males and females were bred together, and group two, in which males and females were bred separately. In group one, α-lipoic acid improved the mean lifespan, reduced the fecundity of females, and reduced the mean body weight of flies at a dose range of 2-2.5 mM, respectively. In group two, α-lipoic acid improved the mean lifespan, reduced the fecundity of females, and reduced the mean body weight of flies at a dose range of 1-2.5 mM, respectively. Improved climbing efficiency was observed with α-lipoic acid at the dose range of 1.5-2.5 mM in flies of group one and 1-2.5 mM in flies of group two, respectively. Administration of α-lipoic acid improved resistance to oxidative stress in only female flies of group one at 2.5 mM, whereas in group two, both male and female flies exhibited enhanced resistance to oxidative stress with α-lipoic acid at a dose range of 2-2.5 mM, respectively. Male and female flies of only group one showed improved resistance to heat shock stress with α-lipoic acid at a dose range of 2-2.5 mM. Only female flies of group two exhibited a slight improvement in recovery time following cold shock with α-lipoic acid only at 2.5 mM. No significant change in resistance to starvation stress was observed with any dose of α-lipoic acid in either group of flies. To summarize, data from this study suggested a probable dose and gender-dependent efficacy of α-lipoic acid in flies fed with a high-fat diet, which was significantly influenced by the mating status of flies due to varied rearing conditions. | Nicol, A., Ahmed, M., Fischer, C., Garces, J. G., Magnus, S., Maung, N., Molisani, N., Petrov, S., Palu, R. A. S. (2024). Larval density can be used to predict genetic modifiers of glucagon signaling in Drosophila melanogaster. PLoS One, 19(8):e0302565 PubMed ID: 39196987
Summary: Obesity is a growing concern. 42.3% of people in the U.S were considered obese between 2017-2018. Much is still unknown about the genetic components that contribute to weight gain. In humans, the hormone glucagon is a major contributor to the body's energy regulation as it signals for the breakdown of lipids. Treatments targeting the glucagon pathway have helped patients with both weight loss and appetite suppression. Understanding the genetic modifiers of glucagon signaling and its downstream pathways could enable the development of a wider variety of effective therapeutics. This study blocked the glucagon pathway in Drosophila melanogaster by reducing the expression of the fly ortholog of the glucagon receptor (AKHR). This model was then crossed to the Drosophila Genetic Reference Panel (DGRP) and looked for natural variation in fat content. Variation in larval density was used to identify candidate modifier genes through a genome-wide association study. These modifier genes were then tested by increasing or decreasing their expression in the AKHR model. These candidates were initially screened with the same density assay used in the original study to narrow down to four candidate genes that substantially impacted the density of the larvae: THADA, AmyD, GluRIIC, and CG9826. These candidates were further characterized using biochemical assays to analyze stored metabolites such as triglycerides, glucose, glycogen, and protein under control, high sugar, and high fat conditions to see if the larvae are resistant to environmental changes. These results indicate consistency between the results of the density assay and direct measurement of metabolite levels. In particular, THADA and AmyD are highlighted as interesting genes for additional study. This study should to improve understanding of the glucagon signaling pathway, obesity, and lipid metabolism. This study also aimed to provide candidate genes that can be regarded as future therapeutic targets. |
| Kauffman, M. R., DiAngelo, J. R. (2024). Glut1 Functions in Insulin-Producing Neurons to Regulate Lipid and Carbohydrate Storage in Drosophila. Biomolecules, 14(8) PubMed ID: 39199423
Summary: Obesity remains one of the largest health problems in the world, arising from the excess storage of triglycerides (TAGs). However, the full complement of genes that are important for regulating TAG storage is not known. The Glut1 gene encodes a Drosophila glucose transporter that has been identified as a potential obesity gene through genetic screening. Yet, the tissue-specific metabolic functions of Glut1 are not fully understood. This study characterized the role of Glut1 in the fly brain by decreasing neuronal Glut1 levels with RNAi and measuring glycogen and TAGs. Glut1RNAi flies had decreased TAG and glycogen levels, suggesting a nonautonomous role of Glut1 in the fly brain to regulate nutrient storage. A group of hormones that regulate metabolism and are expressed in the fly brain are Drosophila insulin-like peptides (Ilps) 2, 3, and 5. Interestingly, this study observed blunted Ilp3 and Ilp5 expression in neuronal Glut1RNAi flies, suggesting Glut1 functions in insulin-producing neurons (IPCs) to regulate whole-organism TAG and glycogen storage. Consistent with this hypothesis, fewer TAGs and glycogens was seen and decreased expression was seen ot of Ilp3 and Ilp5 in flies with IPC-specific Glut1RNAi. Together, these data suggest Glut1 functions as a nutrient sensor in IPCs, controlling TAG and glycogen storage and regulating systemic energy homeostasis. | Vonolfen, M. C., Meyer Zu Altenschildesche, F. L., Nam, H. J., Brodesser, S., Gyenis, A., Buellesbach, J., Lam, G., Thummel, C. S., Storelli, G. (2024). Drosophila HNF4 acts in distinct tissues to direct a switch between lipid storage and export in the gut. Cell Rep, 43(9):114693 PubMed ID: 39235946
Summary: Nutrient digestion, absorption, and export must be coordinated in the gut to meet the nutritional needs of the organism. This study used the Drosophila intestine to characterize the mechanisms that coordinate the fate of dietary lipids. Enterocytes specialized in absorbing and exporting lipids to peripheral organs. Distinct hepatocyte-like cells, called oenocytes, communicate with these enterocytes to adjust intestinal lipid storage and export. A single transcription factor, Drosophila hepatocyte nuclear factor 4 (dHNF4), supports this gut-liver axis. In enterocytes, dHNF4 maximizes dietary lipid export by preventing their sequestration in cytoplasmic lipid droplets. In oenocytes, dHNF4 promotes the expression of the insulin antagonist ImpL2 to activate Foxo and suppress lipid retention in enterocytes. Disruption of this switch between lipid storage and export is associated with intestinal inflammation, suggesting a lipidic origin for inflammatory bowel diseases. These studies establish dHNF4 as a central regulator of intestinal metabolism and inter-organ lipid trafficking. |
| Wu, G., Ma, T., Hancock, C. E., Gonzalez, S., Aryal, B., Vaz, S., Chan, G., Palarca-Wong, M., Allen, N., Chung, C. I., Shu, X., Liu, Q. (2024). Opposing GPCR signaling programs protein intake setpoint in Drosophila. Cell, PubMed ID: 39197448
Summary: Animals defend a target level for their fundamental needs, including food, water, and sleep. Deviation from the target range, or "setpoint," triggers motivated behaviors to eliminate that difference. Whether and how the setpoint itself is encoded remains enigmatic for all motivated behaviors. Employing a high-throughput feeding assay in Drosophila, this study demonstrate dthat the protein intake setpoint is set to different values in male, virgin female, and mated female flies to meet their varying protein demands. Leveraging this setpoint variability, this study found, remarkably, that the information on the intake setpoint is stored within the protein hunger neurons as the resting membrane potential. Two RFamide G protein-coupled receptor (GPCR) pathways, by tuning the resting membrane potential in opposite directions, coordinately program and adjust the protein intake setpoint. The FMRFa-FMRFaR-PKC pathway was found to signal to lower the protein intake setpoint, and the Myosuppressin-MSR2-PKA pathway signals were found to raise the protein intake setpoint. Together, these studies map the protein intake setpoint to a single trackable physiological parameter and elucidate the cellular and molecular mechanisms underlying setpoint determination and modulation. | Kosakamoto, H., Sakuma, C., Okada, R., Miura, M., Obata, F. (2024). Context-dependent impact of the dietary non-essential amino acid tyrosine on Drosophila physiology and longevity.. Sci Adv, 10(35):eadn7167 PubMed ID: 39213345
Summary: Dietary protein intake modulates growth, reproduction, and longevity by stimulating amino acid (AA)-sensing pathways. Essential AAs are often considered as limiting nutrients during protein scarcity, and the role of dietary non-essential AAs (NEAAs) is less explored. Although tyrosine has been reported to be crucial for sensing protein restriction in Drosophila larvae, its effect on adult physiology and longevity remains unclear. Using a synthetic diet, a systematic investigation was performed of the effect of single NEAA deprivation on nutrient-sensing pathways, reproductive ability, starvation resistance, feeding behavior, and life span in adult female flies. Specifically, dietary tyrosine deprivation decreases internal tyrosine levels and fecundity, influences AA-sensing machineries, and extends life span. These nutritional responses are not observed under higher total AA intake or in infertile female flies, suggesting a context-dependent influence of dietary tyrosine. These findings highlight the unique role of tyrosine as a potentially limiting nutrient, underscoring its value for dietary interventions aimed at enhancing health span. |
Monday July 7th - Disease Models |
| Landaverde, S., Sleep, M., Lacoste, A., Tan, S., Schuback, R., Reiter, L. T., Iyengar, A. (2024). Glial expression of Drosophila UBE3A causes spontaneous seizures that can be modulated by 5-HT signaling. Neurobiol Dis, 200:106651 PubMed ID: 39197537
Summary: Misexpression of the E3 ubiquitin ligase gene UBE3A is thought to contribute to a range of neurological disorders. In the context of Dup15q syndrome, additional genomic copies of UBE3A give rise to the autism, muscle hypotonia and spontaneous seizures characteristics of the disorder. In a Drosophila model of Dup 15q syndrome, it was recently shown that glial-driven expression of the UBE3A ortholog dube3a led to a "bang-sensitive" phenotype, where mechanical shock triggers convulsions, suggesting glial dube3a expression contributes to hyperexcitability in flies. This study directly compare the consequences of glial- and neuronal-driven dube3a expression on motor coordination and seizure susceptibility in Drosophila. To quantify seizure-related behavioral events, a hidden Markov model was developed and trained: driven dube3a expression led to clear motor phenotypes. However, only glial-driven dube3a expression displayed spontaneous seizure-associated immobilization events, that were clearly observed at high-temperature (38 °C). Using a tethered fly preparation amenable to electrophysiological monitoring of seizure activity, this study found glial-driven dube3a flies display aberrant spontaneous spike discharges which are bilaterally synchronized. Neither neuronal-dube3a overexpressing flies, nor control flies displayed these firing patterns. A previous drug screen was performed for FDA approved compounds that can suppress bang-sensitivity in glial-driven dube3a expressing flies; certain 5-HT modulators were identified as strong seizure suppressors. Glial-driven dube3a flies fed the serotonin reuptake inhibitor vortioxetine and the 5-HT(2A) antagonist ketanserin displayed reduced immobilization and spike bursting, consistent with the previous study. Together these findings highlight the potential for glial pathophysiology to drive Dup15q syndrome-related seizure activity. | Bitar, S., Baumann, T., Weber, C., Abusaada, M., Rojas-Charry, L., Ziegler, P., Schettgen, T., Randerath, I. E., Venkataramani, V., Michalke, B., Hanschmann, E. M., Arena, G., Krueger, R., Zhang, L., Methner, A. (2024). Iron-sulfur cluster loss in mitochondrial CISD1 mediates PINK1 loss-of-function phenotypes. Elife, 13 PubMed ID: 39159312
Summary: Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra of the midbrain. Familial cases of PD are often caused by mutations of PTEN-induced kinase 1 (PINK1) and the ubiquitin ligase Parkin, both pivotal in maintaining mitochondrial quality control. CISD1, a homodimeric mitochondrial iron-sulfur-binding protein, is a major target of Parkin-mediated ubiquitination. This study discovered a heightened propensity of CISD1 to form dimers in Pink1 mutant flies and in dopaminergic neurons from PINK1 mutation patients. The dimer consists of two monomers that are covalently linked by a disulfide bridge. In this conformation CISD1 cannot coordinate the iron-sulfur cofactor. Overexpressing Cisd, the Drosophila orthologue of CISD1, and a mutant Cisd incapable of binding the iron-sulfur cluster in Drosophila reduced climbing ability and lifespan. This was more pronounced with mutant Cisd and aggravated in Pink1 mutant flies. Complete loss of Cisd, in contrast, rescued all detrimental effects of Pink1 mutation on climbing ability, wing posture, dopamine levels, lifespan, and mitochondrial ultrastructure. These results suggest that Cisd, probably iron-depleted Cisd, operates downstream of Pink1 shedding light on PD pathophysiology and implicating CISD1 as a potential therapeutic target. |
| Nitta, Y., Osaka, J., Maki, R., Hakeda-Suzuki, S., Suzuki, E., Ueki, S., Suzuki, T., Sugie, A. (2024). Drosophila model to clarify the pathological significance of OPA1 in autosomal dominant optic atrophy. Elife, 12 PubMed ID: 39177028
Summary: Autosomal dominant optic atrophy (DOA) is a progressive form of blindness caused by degeneration of retinal ganglion cells and their axons, mainly caused by mutations in the OPA1 mitochondrial dynamin like GTPase (OPA1) gene. OPA1 encodes a dynamin-like GTPase present in the mitochondrial inner membrane. When associated with OPA1 mutations, DOA can present not only ocular symptoms but also multi-organ symptoms (DOA plus). DOA plus often results from point mutations in the GTPase domain, which are assumed to have dominant-negative effects. However, the presence of mutations in the GTPase domain does not always result in DOA plus. Therefore, an experimental system to distinguish between DOA and DOA plus is needed. This study found that loss-of-function mutations of the dOPA1 gene in Drosophila can imitate the pathology of optic nerve degeneration observed in DOA. This degeneration was successfully rescued by expressing the human OPA1 (hOPA1) gene, indicating that hOPA1 is functionally interchangeable with dOPA1 in the fly system. However, mutations previously identified did not ameliorate the dOPA1 deficiency phenotype. By expressing both WT and DOA plus mutant hOPA1 forms in the optic nerve of dOPA1 mutants, DOA plus mutations suppressed the rescue, facilitating the distinction between loss-of-function and dominant-negative mutations in hOPA1. This fly model aids in distinguishing DOA from DOA plus and guides initial hOPA1 mutation treatment strategies. | Layalle, S., Aimond, F., Brugioti, V., Guissart, C., Raoul, C., Soustelle, L. (2024). The ALS-associated KIF5A P986L variant is not pathogenic for Drosophila motoneurons. Sci Rep, 14(1):19540 PubMed ID: 39174694
Summary: Amyotrophic lateral sclerosis (ALS) is a devastating paralytic disorder caused by the death of motoneurons. Several mutations in the KIF5A gene have been identified in patients with ALS. Some mutations affect the splicing sites of exon 27 leading to its deletion (Δ27 mutation). KIF5A Δ27 is aggregation-prone and pathogenic for motoneurons due to a toxic gain of function. Another mutation found to be enriched in ALS patients is a proline/leucine substitution at position 986 (P986L mutation). Bioinformatic analyses strongly suggest that this variant is benign. This study aimed to conduct functional studies in Drosophila to classify the KIF5A P986L variant. When expressed in motoneurons, KIF5A P986L does not modify the morphology of larval NMJ or the synaptic transmission. In addition, KIF5A P986L is uniformly distributed in axons and does not disturb mitochondria distribution. Locomotion at larval and adult stages is not affected by KIF5A P986L. Finally, both KIF5A WT and P986L expression in adult motoneurons extend median lifespan compared to control flies. Altogether, these data show that the KIF5A P986L variant is not pathogenic for motoneurons and may represent a hypomorphic allele, although it is not causative for ALS. |
| Oka, M., Nakajima, S., Suzuki, E., Yamamoto, S., Ando, K. (2024). Glucose uptake in pigment glia suppresses tau-induced inflammation and photoreceptor degeneration in Drosophila. bioRxiv, PubMed ID: 39229232
Summary: Brain inflammation contributes to the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD). Glucose hypometabolism and glial activation are pathological features seen in AD brains; however, the connection between the two is not fully understood. Using a Drosophila model of AD, this study identified that glucose metabolism in glia plays a critical role in neuroinflammation under disease conditions. Expression of human tau in the retinal cells, including photoreceptor neurons and pigment glia, causes photoreceptor degeneration accompanied by inclusion formation and swelling of lamina glial cells. Inclusions were found to be formed by glial phagocytosis, and swelling of the laminal cortex correlates with the expression of antimicrobial peptides (AMPs). Co-expression of human glucose transporter 3 (GLUT3) with tau in the retina does not affect tau levels but suppresses these inflammatory responses and photoreceptor degeneration. This study also found that expression of GLUT3, specifically in the pigment glia, is sufficient to suppress inflammatory phenotypes and mitigate photoreceptor degeneration in the /tau-expressing retina. These results suggest that glial glucose metabolism contributes to inflammatory responses and neurodegeneration in tauopathy. | Chechenova, M., McLendon, L., Dallas, B., Stratton, H., Kiani, K., Gerberich, E., Alekseyenko, A., Tamba, N., An, S., Castillo, L., Czajkowski, E., Talley, C., Brown, A., Bryantsev, A. L. (2024). Muscle degeneration in aging Drosophila flies: the role of mechanical stress. Skeletal muscle, 14(1):20 PubMed ID: 39164781
Summary: Muscle wasting is a universal hallmark of aging which is displayed by a wide range of organisms, although the causes and mechanisms of this phenomenon are not fully understood. This study used Drosophila to characterize the phenomenon of spontaneous muscle fiber degeneration (SMFD) during aging. SMFD occurs across diverse types of somatic muscles, progresses with chronological age, and positively correlates with functional muscle decline. Data from vital dyes and morphological markers imply that degenerative fibers most likely die by necrosis. Mechanistically, SMFD is driven by the damage resulting from muscle contractions, and the nervous system may play a significant role in this process. This quantitative model of SMFD assessment can be useful in identifying and validating novel genetic factors that influence aging-related muscle wasting. |
Wednesday July 2nd - Larval and Adult Neural Development, Structure and Function |
| Prelic, S., Keesey, I. W., Lavista-Llanos, S., Hansson, B. S., Wicher, D. (2024). Innexin expression and localization in the Drosophila antenna indicate gap junction or hemichannel involvement in antennal chemosensory sensilla. Cell and tissue research, PubMed ID: 39174822
Summary: Odor detection in insects is largely mediated by structures on antennae called sensilla, which feature a strongly conserved architecture and repertoire of olfactory sensory neurons (OSNs) and various support cell types. In Drosophila, OSNs are tightly apposed to supporting cells, whose connection with neurons and functional roles in odor detection remain unclear. Coupling mechanisms between these neuronal and non-neuronal cell types have been suggested based on morphological observations, concomitant physiological activity during odor stimulation, and known interactions that occur in other chemosensory systems. For instance, it is not known whether cell-cell coupling via gap junctions between OSNs and neighboring cells exists, or whether hemichannels interconnect cellular and extracellular sensillum compartments. This study showed that innexins, which form hemichannels and gap junctions in invertebrates, are abundantly expressed in adult drosophilid antennae. By surveying antennal transcriptomes and performing various immunohistochemical stainings in antennal tissues, innexin-specific patterns of expression and localization were discovered, with a majority of innexins strongly localizing to glial and non-neuronal cells, likely support and epithelial cells. Finally, by injecting gap junction-permeable dye into a pre-identified sensillum, no dye coupling was discovered between neuronal and non-neuronal cells. Together with evidence of non-neuronal innexin localization, it is concluded that innexins likely do not conjoin neurons to support cells, but that junctions and hemichannels may instead couple support cells among each other or to their shared sensillum lymph to achieve synchronous activity. How coupling of sensillum microenvironments or compartments may potentially contribute to facilitate chemosensory functions of odor sensing and sensillum homeostasis is discussed. | Rohrbach, E. W., Asuncion, J. D., Meera, P., Kralovec, M., Deshpande, S. A., Schweizer, F. E., Krantz, D. E. (2024). Heterogeneity in the projections and excitability of tyraminergic/octopaminergic neurons that innervate the Drosophila reproductive tract. Frontiers in molecular neuroscience, 17:1374896 PubMed ID: 39156129
Summary: Aminergic nuclei in mammals are generally composed of relatively small numbers of cells with broad projection patterns. Despite the gross similarity of many individual neurons, recent transcriptomic, anatomic and behavioral studies suggest previously unsuspected diversity. Smaller clusters of aminergic neurons in the model organism Drosophila melanogaster provide an opportunity to explore the ramifications of neuronal diversity at the level of individual cells. A group of approximately 10 tyraminergic/octopaminergic neurons innervates the female reproductive tract in flies and has been proposed to regulate multiple activities required for fertility. The projection patterns of individual neurons within the cluster are not known and it remains unclear whether they are functionally heterogenous. Using a single cell labeling technique, this study showed that each region of the reproductive tract is innervated by a distinct subset of tyraminergic/octopaminergic cells. Optogenetic activation of one subset stimulates oviduct contractions, indicating that the cluster as a whole is not required for this activity, and underscoring the potential for functional diversity across individual cells. Using whole cell patch clamp, two adjacent and morphologically similar cells were shown to be tonically inhibited, but each responds differently to injection of current or activation of the inhibitory GluCl receptor. GluCl appears to be expressed at relatively low levels in tyraminergic/octopaminergic neurons within the cluster, suggesting that it may regulate their excitability via indirect pathways. Together, these data indicate that specific tyraminergic/octopaminergic cells within a relatively homogenous cluster have heterogenous properties and provide a platform for further studies to determine the function of each cell. |
| Peng, L., Wang, T. (2024). Histamine synthesis and transport are coupled in axon terminals via a dual quality control system. The EMBO journal, PubMed ID: 39242788
Summary: Monoamine neurotransmitters generated by de novo synthesis are rapidly transported and stored into synaptic vesicles at axon terminals. This transport is essential both for sustaining synaptic transmission and for limiting the toxic effects of monoamines. In this study, synthesis of the monoamine histamine by histidine decarboxylase (HDC) and subsequent loading of histamine into synaptic vesicles are shown to be physically and functionally coupled within Drosophila photoreceptor terminals. This process requires HDC anchoring to synaptic vesicles via interactions with N-ethylmaleimide-sensitive fusion protein 1 (NSF1). Disassociating HDC from synaptic vesicles disrupts visual synaptic transmission and causes somatic accumulation of histamine, which leads to retinal degeneration. A proteasome degradation system was also found to be mediated by the E3 ubiquitin ligase, purity of essence (POE), which clears mislocalized HDC from the soma, thus eliminating the cytotoxic effects of histamine. Taken together, these results reveal a dual mechanism for translocation and degradation of HDC that ensures restriction of histamine synthesis to axonal terminals and at the same time rapid loading into synaptic vesicles. This is crucial for sustaining neurotransmission and protecting against cytotoxic monoamines. | Sung, H. H., Li, H., Huang, Y. C., Ai, C. L., Hsieh, M. Y., Jan, H. M., Peng, Y. J., Lin, H. Y., Yeh, C. H., Lin, S. Y., Yeh, C. Y., Cheng, Y. J., Khoo, K. H., Lin, C. H., Chien, C. T. (2024). Galectins induced from hemocytes bridge phosphatidylserine and N-glycosylated Drpr/CED-1 receptor during dendrite pruning. Nat Commun, 15(1):7402 PubMed ID: 39191750
Summary: During neuronal pruning, phagocytes engulf shed cellular debris to avoid inflammation and maintain tissue homeostasis. How phagocytic receptors recognize degenerating neurites had been unclear. This study identified two glucosyltransferases Alg8 and Alg10 of the N-glycosylation pathway required for dendrite fragmentation and clearance through genetic screen. The scavenger receptor Draper (Drpr) is N-glycosylated with complex- or hybrid-type N-glycans that interact specifically with galectins. The galectins Crouching tiger (Ctg) and Hidden dragon (Hdg) were identified, which interact with N-glycosylated Drpr and function in dendrite pruning via the Drpr pathway. Ctg and Hdg are required in hemocytes for expression and function, and are induced during dendrite injury to localize to injured dendrites through specific interaction with exposed phosphatidylserine (PS) on the surface membrane of injured dendrites. Thus, the galectins Ctg and Hdg bridge the interaction between PS and N-glycosylated Drpr, leading to the activation of phagocytosis. |
| Warren, B., Gopfert, M. C. (2024). Mechanically-evoked spike responses of pentascolopidial chordotonal organs of Drosophila larvae. The Journal of experimental biology, PubMed ID: 39206682
Summary: Mechano-sensitive ensembles of neurons in insects, known as Chordotonal organs (COs), function in proprioception, the detection of sound and substrate vibrations. This study characterized the mechanical sensitivity of the lateral pentascolopidial CO (lch5) of Drosophila larvae to establish its postulated role in proprioception. A physiologically realistic method was developed to replicate proprioceptive input to lch5 by pulling the apodeme (tendon) to which the tips of the neurons attach. Lch5 sensory neurons were found to respond transiently with a short latency to the velocity-component of stretch displacements and the release of stretch (relaxation). In the mechanosensory mutant inactive, lch5 has a decreased response to mechanical stimuli and a lower overall spontaneous spike rate. Finally, the input that lch5 receives was stimulated during crawling; spike rate was found to change of peristaltic body contraction. This study provides a characterization of proprioceptive feedback in Drosophila larvae and firmly establish the proprioceptive function of lch5 in larval locomotion. | Delescluse, J., Simonnet, M. M., Ziegler, A. B., Piffaretti, K., Alves, G., Grosjean, Y., Maniere, G. (2024). A LAT1-Like Amino Acid Transporter Regulates Neuronal Activity in the Drosophila Mushroom Bodies. Cells, 13(16) PubMed ID: 39195231
Summary: The proper functioning of neural circuits that integrate sensory signals is essential for individual adaptation to an ever-changing environment. Many molecules can modulate neuronal activity, including neurotransmitters, receptors, and even amino acids. This study asked whether amino acid transporters expressed by neurons can influence neuronal activity. minidiscs (mnd), which encodes a light chain of a heterodimeric amino acid transporter, was found to be expressed in different cell types of the adult Drosophila brain: in mushroom body neurons (MBs) and in glial cells. Using live calcium imaging, MND was found to be expressed in α/β MB neurons and is essential for sensitivity to the L-amino acids: Leu, Ile, Asp, Glu, Lys, Thr, and Arg. Target Of Rapamycin (TOR) pathway but not the Glutamate Dehydrogenase (GDH) pathway was also found to be involved in the Leucine-dependent response of α/β MB neurons. This study strongly supports the key role of MND in regulating MB activity in response to amino acids. ' |
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