Feedback regulation is central to Delta-Notch signalling required for Drosophila wing vein morphogenesis.
ABSTRACT Delta and Notch are required for partitioning of vein and intervein cell fates within the provein during Drosophila metamorphosis. We find that partitioning of these fates is dependent on Delta-mediated signalling from 22 to 30 hours after puparium formation at 25 degrees C. Within the provein, Delta is expressed more highly in central provein cells (presumptive vein cells) and Notch is expressed more highly in lateral provein cells (presumptive intervein cells). Accumulation of Notch in presumptive intervein cells is dependent on Delta signalling activity in presumptive vein cells and constitutive Notch receptor activity represses Delta accumulation in presumptive vein cells. When Delta protein expression is elevated ectopically in presumptive intervein cells, complementary Delta and Notch expression patterns in provein cells are reversed, and vein loss occurs because central provein cells are unable to stably adopt the vein cell fate. Our findings imply that Delta-Notch signalling exerts feedback regulation on Delta and Notch expression during metamorphic wing vein development, and that the resultant asymmetries in Delta and Notch expression underlie the proper specification of vein and intervein cell fates within the provein.
Full-textDOI: · Available from: Stacey S Huppert, May 29, 2015
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ABSTRACT: Enhancer-of-split (E(spl)) was genetically characterized in Drosophila as a dominant mutation that interacts with an allele of Notch, the receptor in a multipurpose signaling pathway throughout development. Although dominant mutations are often not informative of the normal gene function, E(spl) turned out to encode a family of seven paralogous basic helix-loop-helix proteins of utmost importance in the implementation of the Notch signal in the receiving cell. They are transcriptionally induced by Notch in almost every instance where the signal is deployed, and they participate in numerous feedback circuits, where they interface with a panoply of additional more tissue-specific Notch targets to ensure the proper signaling outcome. Besides the bHLH domain, E(spl) contain a characteristic Orange domain and are classified in the Hes (hairy and enhancer-of-split) branch of the bHLH-Orange proteins. They act as DNA-binding repressors in close collaboration with the corepressor Groucho. In this review, we will focus on the regulation of E(spl) expression and on the function of E(spl) proteins. In the latter section, we will present some of the best-studied developmental events where E(spl) function has been analysed as well as the molecular mechanism of E(spl) activity that has transpired. Finally, we will review the evolution of this protein family, which, albeit of relatively recent origin, present only in insects and crustaceans, has undergone extensive diversification, including gene loss and duplication. Importantly, many of the characteristics of E(spl) proteins are more deeply rooted in the very ancient larger bHLH-O family, which seems to have forged a connection with the Notch pathway from the very beginning of multicellular animal life.Current Topics in Developmental Biology 01/2014; 110C:217-262. DOI:10.1016/B978-0-12-405943-6.00006-3 · 4.21 Impact Factor
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ABSTRACT: Although fluctuating asymmetry has become popular as a measure of developmental instability, few studies have examined its developmental basis. We propose an approach to investigate the role of development for morphological asymmetry by means of morphometric methods. Our approach combines geometric morphometrics with the two-way ANOVA customary for conventional analyses of fluctuating asymmetry and can discover localized features of shape variation by examining the patterns of covariance among landmarks. This approach extends the notion of form used in studies of fluctuating asymmetry from collections of distances between morphological landmarks to an explicitly geometric concept of shape characterized by the configuration of landmarks. We demonstrate this approach with a study of asymmetry in the wings of tsetse flies (Glossina palpalis gambiensis). The analysis revealed significant fluctuating and directional asymmetry for shape as well as ample shape variation among individuals and between the offspring of young and old females. The morphological landmarks differed markedly in their degree of variability, but multivariate patterns of landmark covariation identified by principal component analysis were generally similar between fluctuating asymmetry (within-individual variability) and variation among individuals. Therefore, there is no evidence that special developmental processes control fluctuating asymmetry. We relate some of the morphometric patterns to processes known to be involved in the development of fly wings.Evolution 10/1998; 52(5):1363. DOI:10.2307/2411306 · 4.66 Impact Factor
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ABSTRACT: Background: Endothelial or epithelial cellular branching is vital in development and cancer progression; however, the molecular mechanisms of these processes are not clear. In Drosophila, the terminal cell at the end of some tracheal tube ramifies numerous fine branches on the internal organs to supply oxygen. To discover more genes involved in terminal branching, we searched for mutants with very few terminal branches using the Kiss enhancer-trap line collection. Results: In this analysis, we identified cropped (crp), encoding the Drosophila homolog of the transcription activator protein AP-4. Overexpressing the wild-type crp gene or a mutant that lacks the DNA-binding region in either the tracheal tissues or terminal cells led to a loss-of-function phenotype, implying that crp can affect terminal branching. Unexpectedly, the ectopic expression of cropped also led to enlarged organs, and cell-counting experiments on the salivary glands suggest that elevated levels of AP-4 increase cell size and organ size. Like its mammalian counterpart, cropped is controlled by dMyc, as ectopic expression of dMyc in the terminal cells increased cellular branching and the Cropped protein levels in vivo. Conclusions: We find that the branching morphogenesis of the terminal cells of the tracheal tubes in Drosophila requires the dMyc-dependent activation of Cropped/AP-4 protein to increase the cell growth of the terminal cells.BMC Developmental Biology 12/2015; 15(1). DOI:10.1186/s12861-015-0069-6 · 2.75 Impact Factor