extra macrochaetae

DEVELOPMENTAL BIOLOGY

Embryonic

EMC is supplied maternally and produced at all stages in embryos as well (Ellis 1980 and Garrell, 1990). emc is expressed in complex patterns in the three embryonic layers. Expression of emc often precedes and accompanies morphogenic movements involved in gastrulation. Examples are the cephalic and ventral furrows, amnioproctodeal invagination, anterior midgut primordium, dorsal folds, invaginating stomodeum, tracheal pits and the intersegmental grooves. Paradoxically, the mRNA is virtually absent from the ectodermal layer from which neuroblasts segregate. Other regions of abundant emc expression are the mesodermal layer, visceral mesoderm and rudiments of Malpighian tubules and muscle attachment sites (Cubas 1994 and Ellis 1994).

Larval

Both hairy and emc negatively regulate morphogenetic furrow progression in the developing eye. Both are expressed ahead of the morphogenetic furrow (Brown 1995).

The bristle patterning genes hairy and extramacrochaetae regulate the development of structures required for flight in Diptera

The distribution of sensory bristles on the thorax of Diptera (true flies) provides a useful model for the study of the evolution of spatial patterns. Large bristles called macrochaetes are arranged into species-specific stereotypical patterns determined via spatially discrete expression of the proneural genes achaete-scute (ac-sc). In Drosophila ac-sc expression is regulated by transcriptional activation at sites where bristle precursors develop and by repression outside of these sites. Three genes, extramacrochaetae (emc), hairy (h) and stripe (sr), involved in repression have been documented. This study demonstrates that in Drosophila, the repressor genes emc and h, like sr, play an essential role in the development of structures forming part of the flight apparatus. It was found that, in Calliphora vicina a species diverged from D. melanogaster by about 100Myr, spatial expression of emc, h and sr is conserved at the location of development of those structures. Based on these findings it is argued, first, that the role emc, h and sr in development of the flight apparatus preceded their activities for macrochaete patterning; second, that species-specific variation in activation and repression of ac-sc expression is evolving in parallel to establish a unique distribution of macrochaetes in each species (Costa, 2013).

Adult

The pattern of adult sensilla is promoted by achaete-scute complex and daughterless, and is suppressed by emc and hairy (Moscoso del Prada 1984).

Effects of Mutation or Deletion

emc mutant embryos do not hatch and their cuticle displays multiple alterations. emc is required for proper formation of intersegmental grooves, apparently due to defects in muscle development. With emc mutation, accumulation of Fasciclin III is reduced.

Just before the start of germ band retraction [Image], spatial distribution of neuroblasts and their descendants (the ganglion mother cells) are found to be more disorganized than in wild type; later axonal patterns are anomolous (Cubas, 1994). Malpighian tubules are rudimentary and some muscles are missing or disrupted. emc controls and limits cell proliferation within the inter-vein region of the wing, with similar effects on haltere and leg (de Celis, 1994).

A genetic and phenotypic analysis of the gene pannier is described. Animals mutant for strong alleles die as embryos in which the cells of the amnioserosa are prematurely lost. This leads to a dorsal cuticular hole. The dorsal-most cells of the imagos are also affected: viable mutants exhibit a cleft along the dorsal midline. Pannier mRNA accumulates specifically in the dorsal-most regions of the embryo and the imaginal discs. Viable mutants and mutant combinations also affect the thoracic and head bristle patterns in a complex fashion. Only those bristles within the area of expression of pannier are affected. A large number of alleles have been studied; they reveal that pannier may have opposing effects on the expression of achaete and scute leading to a loss or a gain of bristles. Certain alleles of pannier are sensitive to the dose of extra-machrochaetae. In those parts of the epithelium where both are present, it is possible that pnr and emc function together in the same ac-sc repression pathway (Heitzler, 1996).

emc is required during wing cell proliferation and vein differentiation. Mosaic analysis of hypomorphic emc reveals the tendency of mutant cells to proliferate along veins as long stripes. Large clones abuting two adjacent veins obliterate the corresponding inter-vein, affecting the size and shape of the whole wing. Thus, the emc gene participates in the control of cell proliferation within inter-vein regions in the wing. Similar effects are found in the haltere and the leg. The behavior of emc cells in genetic mosaics indicates that (1) proliferation is locally controlled within inter-vein sectors, (2) cells proliferate according to their genetic activity along preferential positions in the wing morphogenetic landscape, and (3) cell proliferation in the wing is integrated by 'accommodation' between mutant and wild type cells (de Celis, 1995).

How do veins on the dorsal and ventral surfaces of a fly's wing line up in exact opposition to one another? The adult Drosophila wing consists of two wing surfaces, apposed by their basal membranes, which first come into contact at metamorphosis, following wing disc eversion. Contact is crucial. Veins normally appear in these surfaces in a dorsal-ventral symmetric pattern, but when contact between the two surfaces is prevented, the dorsal-ventral pattern of venation takes on a 'corrugated,' asymmetric appearance (vein cells are more compacted and more pigmented). Dorsal-ventral contact apposition was prevented during wing imaginal disc morphogenesis by implanting fragments of discs into metamorphosing hosts. In these implants, longitudinal veins differentiate in both surfaces, but exhibit wider than normal corrugation. These results and those of genetic mosaics for mutants that remove veins or cause ectopic veins, reveal mutual dorso-ventral induction/inhibition at work to modulate the final vein differentiation pattern and/or corrugation. While clones of mutants causing a lack of veins (the single mutant rhomboid, the double mutant rhomboid vein, and the triple mutant extramachrochaetaeAch rhomboid vein) are autonomous in both wing surfaces, the vein phenotype is partially rescued by wild type cells from the opposite surface. When apposed to a lack of vein differentiation in the dorsal surface, vein differentiation fails in distal vein territories, preferentially in the ventral surface. Conversely, extra differentiation as in plexus, extramachrochaetae, HS-rhomboid 27B, Notch and Delta mutants, causes extra veins in clones, not only in the wing surface of the clone, but also in the opposite wing surface. Non-autonomous effects are observed in the same wing surface, a phenomenon called 'connectivity'. Genetic mosiacs of plexus72 and emc HS-rho27B cause neighboring non-mutant cells on the same surface to differentiate extra veins, connecting them. Cis (planar) and trans (vertical) effects may be operationally related, inducing contacting cells to differentiate vein histotypes. Vein cells induce vein differentiation in neighbouring cells, either on the same surface by planar cell-cell communication, or on the opposite surface through signals along the basal membrane of the apposing epithelium. Thus, although the vein pattern is surface-autonomously generated, inhibitory (negative) and inductive (positive) signals take place between both dorsal and ventral wing surfaces in order to refine the final vein pattern with the corresponding dorso-ventral wing surfaces (Milan, 1997).

Wingless and Decapentaplegic cell signaling pathways act synergistically in their contribution to macrochaete (sense organ) patterning on the notum of Drosophila. The analysis of the origin of sense organ precursor prepatterning has focussed on the specification and positioning of the anterior and posterior dorsocentral macrochaetes (aDC, pDC) two large mechanosensory organs located in precise positions relative to surrounding rows of microchaetes. The aDC and pDC SOPs form sequentially on the proximal edge of a single DC proneural cluster where Achaete and Scute expression depends on a cis-activating enhancer sequence, the DC enhancer. Ac expression in the DC proneural cluster requires the activity of wingless. The DC SOPs form adjacent to the stripe of cells expressing wg in the presumptive notum during the third larval instar. To probe the nature of gene interaction required for macrochaetae formation, the Wingless-signaling pathway was ectopically activated by removing Shaggy activity (the homolog of vertebrate glycogen synthase kinase 3) in mosaics. Proneural activity is asymmetric within the Shaggy-deficient clone of cells and shows a fixed polarity with respect to body axis, independent of the precise location of the clone. This asymmetric response indicates the existence in the epithelium of a second signal, possibly Decapentaplegic. Ectopic expression of Decapentaplegic induces extra macrochaetes only in cells that also receive the Wingless signal. Outside the Wg-activated domain, in the medial scutum and prescutum, clones that ectopically express Dpp make only microchaetes. In the Wg-activated domain, within and lateral to the DC meridian, clones of cells ectopically expressing dpp are associated with many extra macrochaetes, which are formed both within and around the Dpp-expressing clones. It is concluded that in areas of the notum where the WG transduction pathway is inactive, Dpp alone is insufficient for macrochaete formation. Activation of Hedgehog signaling generates a long-range signal (Dpp) that can promote macrochaete formation in the Wingless activity domain. This signal depends on decapentaplegic function. Autonomous activation of the Wingless signal response in cells causes them to attenuate or sequester this signal. Extramacrochaetae (a proneural antagonist) is required to limit the anterior/posterior extent of this cluster. If the level of emc is reduced, extra macrochaetes form primarily anterior but also posterior to the normal DCs along the proximal edge of the wg stripe. Further reduction of emc results in additional extra macrochaetes along the dorsal edge of the stripe. These results suggest a novel patterning mechanism that determines sense organ positioning in Drosophila (Phillips, 1999).

A role for extra macrochaetae downstream of Notch in follicle cell differentiation

The Drosophila ovary provides a model system for studying the mechanisms that regulate the differentiation of somatic stem cells into specific cell types. Ovarian somatic stem cells produce follicle cells, which undergo a binary choice during early differentiation. They can become either epithelial cells that surround the germline to form an egg chamber ('main body cells') or a specialized cell lineage found at the poles of egg chambers. This lineage goes on to make two cell types: polar cells and stalk cells. To better understand how this choice is made, a screen was carried out for genes that affect follicle cell fate specification or differentiation. extra macrochaetae (emc), which encodes a helix-loop-helix protein, was identified as a downstream effector of Notch signaling in the ovary. Emc is expressed in proliferating cells in the germarium, as well as in the main body follicle cells. Emc expression in the main body cells is Notch dependent, and emc mutant cells located on the main body fail to differentiate. Emc expression is reduced in the precursors of the polar and stalk cells, and overexpression of Emc caused dramatic egg chamber fusions, indicating that Emc is a negative regulator of polar and/or stalk cells. Emc and Notch are both required in the main body cells for expression of Eyes Absent (Eya), a negative regulator of polar and stalk cell fate. It is proposed that Emc functions downstream of Notch and upstream of Eya to regulate main body cell fate specification and differentiation (Adam, 2004).

EMC has a complex pattern of expression. emc^P5C-lacZ is expressed in the terminal filament and inner sheath cells of the germarium, and in the main body follicle cells of egg chambers, but not in the early follicle cells or in polar or stalk cells. An anti-Emc antibody revealed additional features of Emc expression: Emc is expressed in the undifferentiated follicle cells of the germarium. Its expression is reduced in follicle cells in the intercyst regions between region 2 and region 3 cysts. It is maintained in main body cells but further reduced in stalk and polar cells of stage-1-4 egg chambers. Its expression in stalk cells remains low, but, in polar cells after stage 4, returns to a level indistinguishable from that exhibited by their neighbors. The overall level of expression is somewhat reduced from stage 6 to stage 8, and at stage 9 expression in the oocyte-associated follicle cells is further reduced, although still detectable (Adam, 2004).

There are number of similarities in the phenotypic effects of Notch and Emc in egg chamber development; it is concluded that Emc is a downstream effector of Notch in the differentiation of follicle cells. In other tissues, genes of the Enhancer of split complex are major downstream effectors of Notch signaling, but they do not appear to be required for differentiation of the follicle cells. By contrast, Emc is expressed in most somatic cells of the ovariole and has a loss-of-function phenotype similar to that of Notch. Like Notch, Emc is required for the formation of polar cells, and egg chambers lacking polar cells are observed at one end when emc clones are generated. emc mutant cells also fail to downregulate Fas3 expression at stage 6, and the cells fail to enter endoreplication at the proper time, indicating that emc is required for follicle cell differentiation. In addition, Emc expression in the main body follicle cells is dependent on Notch and can be induced by forced expression of activated Notch. Taken together, this leads to the proposal that Emc is an effector of Notch activity in follicle cells (Adam, 2004).

Notch and Emc are both involved in separation of adjacent egg chambers. Follicles mutant for Notch or emc include egg chambers containing multiple germline cysts and lacking intervening polar and stalk cells. Recent work has shown that Notch signaling is not required for early packaging (enveloping of the cyst by follicle cells), but its role in specifying polar/stalk precursors, which might occur subsequent to packaging, has not been addressed specifically. However, Notch is required autonomously for polar cell differentiation, and at least one pair of differentiated polar cells is required to induce a stalk. Therefore, the packaging defects observed in Notch mutants may be due solely to either the failure of polar cells to differentiate or to a particular role in specifying polar/stalk precursors. The fused egg chambers observed in emc mutants could also be due to a role in one or both processes. If emc were involved separately in both processes, then a dramatic increase would be expected in the frequency of fused egg chambers when clones were generated in the germarium, where precursors are formed. Since no such increase was seen, a role for emc in polar/stalk precursor formation is not posited; however, without a better understanding of polar/stalk precursors, this cannot be confirmed (Adam, 2004).

emc is probably not the only effector downstream of Notch in the ovariole, since emc mutant clones exhibit some differences from Notch mutant clones. In general the effects of emc are less penetrant than those of Notch. For example, emc mutant cells, like Notch mutant cells, exhibit persistent Phosphohistone H3 and Cyclin B labeling but at low frequency and at low levels. In addition, although emc is involved in polar cell specification or differentiation, it is only partially required for this, since normal polar cells could be observed even in clones of a null emc allele. Thus, there are likely to be additional downstream effectors of Notch in the ovary (Adam, 2004).

Molecular epistasis indicates that Notch signals through Emc to induce or maintain Eya expression in the main body follicle cells. Eya expression is lost in large Notch mutant follicle cell clones and can be induced by forced expression of activated Notch in the follicle cells. Eya is involved in inhibiting polar and stalk cell fate, so one might expect that Notch or emc loss-of-function mutants would make extra polar cells. This is not the case, however; it seems likely that the reason Notch and emc mutant cells do not become polar cells is that they fail to differentiate. Eya does not appear to be required for differentiation, but rather for main body cell fate, since eya mutant cells differentiate into polar cells. Thus, the Notch pathway must branch downstream of Emc, with one pathway leading to Eya expression and repression of polar cell fate, and a separate pathway leading to differentiation (Adam, 2004).

Emc can have both positive and negative effects on the number of polar cells. Although this might initially seem mysterious, it can be explained by the dynamic expression of Emc in ovaries. Emc is expressed in the germarium, but it is reduced in polar/stalk precursors. Its expression remains low in stalk cells but, in polar cells, returns to the same level as that of their neighbors around the time of differentiation. Temperature-shift experiments show that forced expression of Emc in immature polar cells can lead to expression of Eya, which is the presumed cause of loss of polar cells. By contrast, forced expression of Emc in maturing polar cells appears to lead to potentiation of polar cell number, i.e., polar cell number per group is not reduced from four to two, as in wild-type, but remains at four polar cells per group. This is probably due to a role for Emc in polar cell differentiation, because loss-of-function emc clones can result in loss of polar cells (Adam, 2004).

Three lines of evidence suggest that Emc may be a key regulator of Eya expression. (1) Emc and Eya expression are similar in multiple respects. Both are upregulated in follicle cells in region 2B of the germarium, and in main body follicle cells from stages 2 through 6. Both are downregulated in the polar/stalk lineage from the germarium through stage 3, and in the oocyte-associated follicle cells at stages 7 through 9. (2) Emc is required for Eya expression in the main body. (3) Emc and Eya produce similar overexpression phenotypes, including fused egg chambers and the loss of polar cells, and, when Emc is overexpressed in the polar cells, Eya expression is induced. Taken together, these data suggest that the expression of Eya in the follicle cells is largely regulated by Emc. Emc is a helix-loop-helix protein that lacks the basic DNA-binding domain of the bHLH transcription factors. It normally opposes the activity of bHLH transcription factors by sequestering them in non-productive complexes. Thus, the dependence of Eya on Emc is likely to be indirect. Presumably, Emc inhibits a bHLH protein that inhibits expression of Eya. The identity of this protein remains an interesting subject for further study (Adam, 2004).

The role of the bHLH protein hairy in morphogenetic furrow progression in the developing Drosophila eye

In Drosophila eye development, a wave of differentiation follows a morphogenetic furrow progressing across the eye imaginal disc. This is subject to negative regulation attributed to the HLH repressor proteins Hairy and Extramacrochaete. Recent studies identify negative feedback on the bHLH gene daughterless as one of the main functions of extramacrochaete. This study assessed the role of hairy in relation to daughterless and other HLH genes. Hairy was not found to regulate the expression of Daughterless, Extramacrochaete or Atonal, and Hairy expression was largely unregulated by these other genes. Null alleles of hairy did not alter the rate or pattern of differentiation, either alone or in the absence of Extramacrochaete. These findings question whether hairy is an important regulator of the progression of retinal differentiation in Drosophila, alone or redundantly with extramacrochaete (Bhattacharya, 2012).

The morphogenetic furrow moves anteriorly across the eye disc under the positive influence of Hh and Dpp. The forward progression of differentiation is a consequence of the positive activation of Ato expression as well as the parallel repression of Emc, which results in elevated levels of the heterodimer partner of Ato, Da. Hh and Dpp also affect the cell cycle, the shapes of cells in the morphogenetic furrow, the expression of retinal determination genes, and the sizes of nucleoli, although it remains to be determined whether these other processes contribute directly to neural differentiation (Bhattacharya, 2012).

This paper addresses hairy, a potential barrier to morphogenetic furrow movement. Hairy protein is expressed through much of the eye disc anterior to the morphogenetic furrow, and is downregulated sharply at the time that Atonal becomes active. Although clones of hairy null mutations do not affect eye differentiation, it has been thought that hairy acts along with emc. so that emc hypomorphs that have no effect on the morphogenetic furrow progression alone do speed up the furrow in combination with hairy null mutations. It has been proposed that Hairy is a marker of a 'preproneural state', in which the presence of Hairy helps restrain incipient neurogenesis (Bhattacharya, 2012).

If hairy acts redundantly with emc, this might be explained by convergence on common targets, since both encode transcriptional repressors. This study found, however, no noticeable effect of hairy null alleles on Da expression, Emc expression, or Ato expression. In addition, h emc double mutant clones appeared to have no additional effect on Da expression from that seen in emc clones. Since no obvious role for hairy in the expression of these genes was detected, the progression of the morphogenetic furrow was measured directly. Although differentiation progresses faster through cells null for emc than through wild type cells, removing hairy had no further effect on morphogenetic furrow progression. These findings provide no evidence that hairy acted redundantly with emc, since it did not regulate morphogenetic furrow progression or target gene expression when emc function was removed, implying that hairy function was not sufficient to compensate even partially for the absence of emc. In fact, a hairy null mutation has no discernible effect on the morphogenetic furrow in either the presence or absence of emc. There may be a small role for emc in regulating Hairy expression, such that Hairy is repressed slightly faster in the absence of emc, but even the complete absence of hairy has no effect on furrow progression, either in the presence or absence of emc. In conjunction with experiments in which Hairy did not affect morphogenetic furrow progression when over-expressed, these findings challenge the model that Hairy regulates morphogenetic furrow progression (Bhattacharya, 2012).

The role for hairy in regulating morphogenetic furrow progression was suggested because hairy antagonizes neurogenesis in other imaginal discs, and because hairy mutations enhanced the phenotype of the emc¹ mutant allele. In addition, failure to downregulate Hairy at the morphogenetic furrow correlates with reduced differentiation in a number of mutant genotypes. The neurogenic phenotype of hairy in other imaginal discs depends on Hairy binding to the enhancer of achaetae. Since achaetae is not expressed or functional during morphogenetic furrow progression, these data offer no basis for predicting hairy function in the eye (Bhattacharya, 2012).

Enhancement of the emc¹ allele, but not the emc^AP6 null allele, could be explained if hairy contributed to emc function in some way, so that hairy function can mitigate partial loss of emc function by increasing the effectiveness of the remaining Emc protein, but would not affect the emc null phenotype. The emc¹mutant allele encodes a Val-to-Glu substitution in the HLH domain, which would be expected to interfere with heterodimer formation by Emc¹ protein, consistent with a hypomorphic phenotype. No evidence was found that hairy contributed to the expression of Emc or to Emc function as a negative regulator of da. Another possibility is that Hairy protein might act through distinct mechanisms in addition to binding to specific DNA sequences. The E(spl) proteins, which contain similar domains to Hairy, can also repress gene expression when targeted to particular genes by protein-protein interactions. It has not been tested whether Hairy might exhibit similar protein-protein interactions. It is also reported that the Chicken Id protein, a homolog of Emc, interacts directly with Hes1, a homolog of Hairy. Thus far, however, Drosophila Hairy is not known to heterodimerize with Emc or any of its proneural gene targets. It is possible that Hairy might regulate da transcription in a subtle way only revealed in the emc¹ backgrounds. For example, Hairy repression of da transcription might be redundant in the presence of wild type emc, and not sufficient to impact da autoregulation in the complete absence of Emc. Detailed information concerning the thresholds of da transcription under different conditions would be required to assess this model (Bhattacharya, 2012).

The Hairy expression ahead of the morphogenetic furrow certainly seems to provide a marker of an early stage of eye development. Consistent with this, retention of Hairy expression in mutant genotypes correlates with diminished retinal differentiation. The findings of this study indicate that, contrary to previous models, any contribution of Hairy to morphogenetic furrow progression is quite limited, and there is little evidence to connect it with emc. The possibility remains that hairy may function in a subtle way, perhaps redundantly with other genes, or affect processes other than furrow progression, particularly since many questions remain to be resolved concerning the transcriptional regulation of eye development, such as how ato expression is initiated as the furrow progresses, or all the mechanisms by which the retinal determination genes contribute to eye development. It is also possible that laboratory conditions conceal the contribution of the hairy gene in eye development, as has been suggested for regulatory pathways that are thought to contribute temperature stability in variable environments (Bhattacharya, 2012).

Abdelkhalek, H. B., et al. (2004). The mouse homeobox gene Not is required for caudal notochord development and affected by the truncate mutation. Genes Dev. 18: 1725-1736. PubMed ID: 15231714

Adam, J. C. and Montell, D. J. (2004). A role for extra macrochaetae downstream of Notch in follicle cell differentiation. Development 131: 5971-5980. PubMed ID: 15539491

Anand, G., et al. (1997). Novel regulation of the helix-loop-helix protein Id1 by S5a, a subunit of the 26 S proteasome. J. Biol. Chem. 272(31): 19140-19151. PubMed ID: 9235903

Bhattacharya, A. and Baker, N. E. (2012). The role of the bHLH protein hairy in morphogenetic furrow progression in the developing Drosophila eye. PLoS One 7: e47503. PubMed ID: 23118874

Bai, G., et al. (2007). Id sustains Hes1 expression to inhibit precocious neurogenesis by releasing negative autoregulation of Hes1. Dev Cell. 13(2): 283-97. PubMed ID: 17681138

Bain, G., et al. (1997). E2A deficiency leads to abnormalities in alphabeta T-cell development and to rapid development of T-cell lymphomas. Mol. Cell. Biol. 17(8): 4782-4791. PubMed ID: 9234734

Baonza, A. and Garcia-Bellido, A. (1999). Dual role of extramacrochaetae in cell proliferation and cell differentiation during wing morphogenesis in Drosophila. Mech. Dev. 80(2): 133-46. PubMed ID: 10072780

Baonza, A., de Celis, J. F. and Garcia-Bellido, A. (2000). Relationships between extramacrochaetae and Notch signaling in Drosophila wing development. Development 127: 2383-2393. PubMed ID: 10804180

Baonza, A. and Freeman, M. (2001). Notch signaling and the initiation of neural development in the Drosophila eye. Development 128: 3889-3898. PubMed ID: 11641214

Blom, B., et al. (1999). Disruption of alphabeta but not of gammadelta T cell development by overexpression of the helix-loop-helix protein Id3 in committed T cell progenitors. EMBO J. 18(10): 2793-2802. PubMed ID: 10329625

Brown, N.L., Sattler, C.A., Paddock, S.W., and Carroll, S.B. (1995). hairy and emc negatively regulate morphogenetic furrow progression in the Drosophila eye. Cell 80(6): 879-87. PubMed ID: 7697718

Cabrera, C.V., Alonso, M.C., and Huikeshoven, H. (1994). Regulation of scute function by extramacrochaete in vitro and in vivo. Development 120(12): 3595-603. PubMed ID: 7821225

Costa, M., Calleja, M., Alonso, C. R. and Simpson, P. (2013). The bristle patterning genes hairy and extramacrochaetae regulate the development of structures required for flight in Diptera. Dev Biol. [Epub ahead of print] PubMed ID: 24384389

Crozatier, M., Glise B. and Vincent, A. (2002). Connecting Hh, Dpp and EGF signalling in patterning of the Drosophila wing; the pivotal role of collier/knot in the AP organiser. Development 129: 4261-4269. PubMed ID: 12183378

Cubas, P., Modolell, J., and Ruiz-Gomez, M. (1994). The helix-loop-helix extramacrochaetae protein is required for proper specification of many cell types in the Drosophila embryo. Development 120(9): 2555-66. PubMed ID: 7956831

de Celis, J.F. and Garcia-Bellido, A. (1994). Roles of the Notch gene in Drosophila wing morphogenesis. Mech. Dev. 46: 109-122. PubMed ID: 7918096

de Celis, J. F., Baonza, A. and Garcia-Bellido, A. (1995). Behavior of extramacrochaetae mutant cells in the morphogenesis of the Drosophila wing. Mech. Dev. 53: 209-221. PubMed ID: 8562423

Deed, R. W., et al. (1997). Regulation of Id3 cell cycle function by Cdk-2-dependent phosphorylation. Mol. Cell. Biol. 17(12): 6815-6821. PubMed ID: 9372912

Deisseroth, K., et al. (2004). Excitation-neurogenesis coupling in adult neural stem/progenitor cells. Neuron 42: 535-552. PubMed ID: 15157417

Derobert, Y., et al. (2002). Structure and expression of three Emx genes in the dogfish Scyliorhinus canicula: Functional and evolutionary implications. Dev. Bio. 247: 390-404. PubMed ID: 12086474

Duffield, G. E., et al. (2009). A role for Id2 in regulating photic entrainment of the mammalian circadian system. Curr Biol. 19(4): 297-304. PubMed ID: 19217292

Ellis, H.M., Spann, D.R. and Posakony, J.W. (1990). extramacrochaetae, a negative regulator of sensory organ development in Drosophila, defines a new class of helix-loop-helix proteins. Cell 61: 27-38. PubMed ID: 1690604

Ellis, H.M. (1994). Embryonic expression and function of the Drosophila helix-loop-helix gene, extramacrochaetae. Mech. Dev. 47(1): 65-72. PubMed ID: 7947322

Ellmeier, W. and Weith, A. (1995). Expression of the helix-loop-helix gene Id3 during murine embryonic development. Dev Dyn 203: 163-173. PubMed ID: 7655079

Florio, M., et al. (1998). Id2 promotes apoptosis by a novel mechanism independent of dimerization to basic helix-loop-helix factors. Mol. Cell. Biol. 18(9): 5435-44. PubMed ID: 9710627

Foronda, D., Martín, P., Sánnchez-Herrero, E. (2012). Drosophila Hox and sex-determination genes control segment elimination through EGFR and extramacrochetae activity. PLoS Genet. 8(8): e1002874. PubMed ID: 22912593

Garcia-Campmany, L. and Marti, E. (2007). The TGFbeta intracellular effector Smad3 regulates neuronal differentiation and cell fate specification in the developing spinal cord. Development 134(1): 65-75. PubMed ID: 17138664

Garrell, J. and Modolell, J. (1990). The Drosophila extramacrochaetae locus, an antagonist of proneural genes that, like these genes, encodes a helix-loop-helix protein. Cell 61: 39-48. PubMed ID: 1690605

Hara, E., Hall, M. and Peters, G. (1997). Cdk2-dependent phosphorylation of Id2 modulates activity of E2A-related transcription factors. EMBO J. 16: 332-342. PubMed ID: 9029153

Heitzler, P., et al. (1996). A genetic analysis of pannier, a gene necessary for viability of dorsal tissues and bristle positioning in Drosophila. Genetics 143(3): 1271-1286. PubMed ID: 8807299

Hong. S. H., Lee. J. H., Lee. J. B., Ji, J. and Bhatia, M. (2011). ID1 and ID3 represent conserved negative regulators of human embryonic and induced pluripotent stem cell hematopoiesis. J. Cell Sci. 124(Pt 9): 1445-52. PubMed ID: 21486943

Hoshijima, K., et al. (1995). Transcriptional regulation of the Sex-lethal gene by helix-loop-helix proteins. Nucleic Acids Res 23: 3441-3448. PubMed ID: 7567454

Janatpour, M. J., et al. (2000). Id-2 regulates critical aspects of human cytotrophoblast differentiation, invasion and migration. Development 127: 549-558. PubMed ID: 10631176

Jeon, H. M., et al. (2008). Inhibitor of differentiation 4 drives brain tumor-initiating cell genesis through cyclin E and notch signaling. Genes Dev. 22(15): 2028-33. PubMed ID: 18676808

Jin, X., Jeon, H. M., Jin, X., Kim, E. J., Yin, J., Jeon, H. Y., Sohn, Y. W., Oh, S. Y., Kim, J. K., Kim, S. H., Jung, J. E., Kwak, S., Tang, K. F., Xu, Y., Rich, J. N. and Kim, H. (2016). The ID1-CULLIN3 axis regulates intracellular SHH and WNT signaling in glioblastoma stem cells. Cell Rep. PubMed ID: 27477274

Kee, Y. and Bronner-Fraser, M. (2005). To proliferate or to die: role of Id3 in cell cycle progression and survival of neural crest progenitors. Genes Dev. 19: 744-755. PubMed ID: 15769946

King, P.H., et al. (1994). Mammalian homologs of Drosophila elav localized to a neuronal subset can bind in vitro to the 3'UTR of mRNA, encoding the Id transcriptional repressor. J. Neurosci. 14: 1943-52. PubMed ID: 8158249

Ko, H.R., Kwon, I.S., Hwang, I., Jin, E.J., Shin, J.H., Brennan-Minnella, A.M., Swanson, R., Cho, S.W., Lee, K.H. and Ahn, J.Y. (2016). Akt1-Inhibitor of DNA binding2 is essential for growth cone formation and axon growth and promotes central nervous system axon regeneration. Elife 5. PubMed ID: 27938661

Kondo, T., and Raff, M. (2000). The Id4 HLH protein and the timing of oligodendrocyte differentiation. EMBO J. 19: 1998-2007. PubMed ID: 10790366

Lai, E. and Posakony, J. (1997). The Bearded box, a novel 3' UTR sequence motif, mediates negative post-transcriptional regulation of Bearded and Enhancer of split Complex gene expression. Development 124(23): 4847-4856. PubMed ID: 9428421

Lai, E. C. and Posakony, J. W. (1998). Regulation of Drosophila neurogenesis byRNA:RNA duplexes? Cell 93: 1103-1104. PubMed ID: 9657143

Langlands, K., et al. (1997). Differential interactions of Id proteins with basic-helix-loop-helix transcription factors. J. Biol. Chem. 272(32): 19785-19793. PubMed ID: 9242638

Lasorella, A., et al. (2000). Id2 is a retinoblastoma protein target and mediates signaling by Myc oncoproteins. Nature 407: 592-598. PubMed ID: 11034201

Light, W., Vernon, A. E., Lasorella, A., Iavarone, A. and Labonne, C. (2005). Xenopus Id3 is required downstream of Myc for the formation of multipotent neural crest progenitor cells. Development 132(8): 1831-1841. PubMed ID: 15772131

Martinsen, B. J. and Bronner-Fraser, M. (1998). Neural crest specification regulated by the helix-loop-helix repressor Id2. Science 282(5379): 988-991. PubMed ID: 9703514

McWhirter, J. R., et al. (1997). A novel fibroblast growth factor gene expressed in the developing nervous system is a downstream target of the chimeric homeodomain oncoprotein E2A-Pbx1. Development 124(17): 3221-3232. PubMed ID: 9310317

Milan, M., Baonza, A. and Garcia-Bellido, A. (1997). Wing surface interactions in venation patterning in Drosophila. Mech. Dev. 67(2): 203-213. PubMed ID: 9392517

Mori, S., Nishikawa, S.-I. and Yokota, Y. (2000). Lactation defect in mice lacking the helix-loop-helix inhibitor Id2. EMBO J. 19: 5772-5781. PubMed ID: 11060028

Moscoso del Prado, J. and Garcia-Bellido, A. (1984). Genetic regulation of the achaete-scute complex of Drosophila melanogaster. Roux's Arch. Dev. Biol. 193: 242-245. PubMed ID:

Norton, J. D. and Atherton, G. T. (1998). Coupling of cell growth control and apoptosis functions of Id proteins. Mol. Cell. Biol. 18(4): 2371-2381. PubMed ID: 9528806

Pagliuca, A., Cannada-Bartoli, P. and Lania, L. (1998). A role for Sp and helix-loop-helix transcription factors in the regulation of the human Id4 gene promoter activity. J. Biol. Chem. 273(13): 7668-7674. PubMed ID: 9516472

Phillips, R. G., Warner, N. L. and Whittle, J. R. (1999). Wingless signaling leads to an asymmetric response to Decapentaplegic-dependent signaling during sense organ patterning on the notum of Drosophila melanogaster. Dev. Biol. 207(1): 150-162. PubMed ID: 10049571

Prabhu, S., et al. (1997). Regulation of the expression of cyclin-dependent kinase inhibitor p21 by E2A and Id proteins. Mol. Cell. Biol. 17(10): 5888-5896. PubMed ID: 9315646

Samanta, J. and Kessler, J. A. (2004). Interactions between ID and OLIG proteins mediate the inhibitory effects of BMP4 on oligodendroglial differentiation. Development 131: 4131-4142. PubMed ID: 15280210

Sawai, S. and Campos-Ortega, J. A. (1997). A zebrafish Id homologue and its pattern of expression during embryogenesis. Mech. Dev. 65(1-2): 175-185. PubMed ID: 9256354

Stankic, M., Pavlovic, S., Chin, Y., Brogi, E., Padua, D., Norton, L., Massague, J. and Benezra, R. (2013). TGF-beta-Id1 signaling opposes Twist1 and promotes metastatic colonization via a mesenchymal-to-epithelial transition. Cell Rep 5: 1228-1242. PubMed ID: 24332369

Sugimori, M., et al. (2007). Combinatorial actions of patterning and HLH transcription factors in the spatiotemporal control of neurogenesis and gliogenesis in the developing spinal cord. Development 134(8): 1617-29. PubMed ID: 17344230

Takahisa, M., et al. (1996). The Drosophila tamou gene, a component of the activating pathway of extramacrochaetae expression, encodes a protein homologous to mammalian cell-cell junction-associated protein ZO-1. Genes Dev. 10:1783-95. PubMed ID: 8698238

Tapanes-Castillo, A. and Baylies, M. K. (2004). Notch signaling patterns Drosophila mesodermal segments by regulating the bHLH transcription factor Twist. Development 131: 2359-2372. PubMed ID: 15128668

Tournay, O. and Benezra, R. (1997). Transcription of the dominant-negative helix-loop-helix protein Id1 is regulated by a protein complex containing the immediate-early response gene Egr-1. Mol. Cell. Biol. 16(5): 2418-2430. PubMed ID: 8628310

Troost, T., Schneider, M. and Klein, T. (2015). A re-examination of the selection of the sensory organ precursor of the bristle sensilla of Drosophila melanogaster. PLoS Genet 11: e1004911. PubMed ID: 25569355

Van Doren, M., Ellis, H.M. and Posakony, J.M. (1991). The Drosophila extramachrochaete protein antagonizes sequence-specific DNA binding by daughterless/achaete-scute protein complees. Development 113: 245-255. PubMed ID: 1764999

Wang, L.H. and Baker, N.E. (2015). Salvador-Warts-Hippo pathway in a developmental checkpoint monitoring Helix-Loop-Helix proteins. Dev Cell 32(2):191-202. PubMed ID: 25579975

Wang, S., et al. (2001). A role for the helix-loop-helix protein Id2 in the control of oligodendrocyte development. Neuron 29: 603-614. PubMed ID: 11301021

Wartiovaara, K., et al. (2002). N-myc promotes survival and induces S-phase entry of postmitotic sympathetic neurons. J. Neurosci. 22(3): 815-824. PubMed ID: 11826111

Yan, W., et al. (1997). High incidence of T-cell tumors in E2A-null mice and E2A/Id1 double-knockout mice. Mol. Cell. Biol. 17(12): 7317-7327. PubMed ID: 9372963

Yashiro-Ohtani, Y., et al. (2009). Pre-TCR signaling inactivates Notch1 transcription by antagonizing E2A. Genes Dev. 23(14): 1665-76 PubMed ID: 19605688

Ying, Q. L., Nichols, J., Chambers, I. and Smith, A. (2003). BMP induction of Id proteins suppresses differentiation and sustains embryonic stem cell self-renewal in collaboration with STAT3. Cell 115: 281-292. PubMed ID: 14636556

Yokota, Y., et al. (1999). Development of peripheral lymphoid organs and natural killer cells depends on the helix-loop-helix inhibitor Id2. Nature 397(6721): 702-6. PubMed ID: 10067894

Yun, K., Mantani, A., Garel, S., Rubenstein, J. and Israel, M. A. (2004). Id4 regulates neural progenitor proliferation and differentiation in vivo. Development 131(21): 5441-8. PubMed ID: 15469968

Zhang, J. M., et al. (1999). Evolutionary conservation of MyoD function and differential utilization of E proteins. Dev. Biol. 208(2): 465-472. PubMed ID: 10191059

date revised: 5 August 2023

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