PATTERN FORMATION IN THE DROSOPHILA EYE DISC

果蝇眼睛的发育是一个遗传顺从的过程，与脊椎动物的眼睛发育具有相同的保守机制。Hedgehog(HH)信号通路在果蝇和脊椎动物的早期眼睛发育中起着关键作用，此外它还具有许多其他发育功能。使用镶嵌方法对影响果蝇眼盘早期图案形成的突变进行了筛选，以允许分离具有额外胚胎功能的基因。在这个屏幕上分离的两个基因，失明(SIT)和增生性视盘(HYD)，似乎对HH信号有相反的影响。目前的提案旨在描述这些基因的分子功能及其在眼睛发育中的作用。SIT是HH激活其在眼盘和翼盘中的靶基因所必需的，但不影响HH本身的表达。将对SIT基因进行分子分析，以期揭示其可能的功能，并将使用遗传学方法来确定其在HH途径中的位置。然后将检验从这些研究中预测的SIT蛋白功能的生化机制。Hyd编码一个Hect家族E3泛素连接酶，它是防止光感受器过早分化、HH表达和周围野生型细胞过度生长所必需的。将结合遗传和生化方法来测试Hyd的正常功能是否是阻断HH的表达或信号，并鉴定由Hyd泛素化的蛋白质。Hyd在其他组织发育中的作用也将被确定。最后，马赛克基因屏幕将扩大到覆盖另外20%的基因组。眼盘细胞分化为视网膜组织所需的突变将被分离，放入互补小组并绘制地图。将对新基因的表型进行表征，并选择最感兴趣的候选基因进行分子分析。这项研究的结果可能既提供了对果蝇眼睛发育过程的更完整的了解，也可能揭示了高等生物体中促进发育和在疾病中受到错误调控的机制和分子。

Development of the Drosophila eye is a genetically amenable process that shares conserved mechanisms with vertebrate eye development. The Hedgehog (Hh) signaling pathway plays a critical role in early eye development in both Drosophila and vertebrates, in addition to its many other developmental functions. A screen for mutations affecting early pattern formation in the Drosophila eye disc has been carried out using a mosaic approach to allow the isolation of genes with additional embryonic functions. Two of the genes isolated in this screen, sightless (sit) and hyperplastic discs (hyd), appear to have opposite effects on Hh signaling. The current proposal aims to characterize the molecular functions of these genes and their role in eye development. sit is required for Hh to activate its target genes in both the eye disc and the wing disc, but does not affect the expression of hh itself. A molecular analysis of the sit gene will be undertaken in the hope of revealing its likely function, and genetic methods will be used to determine its position in the Hh pathway. The biochemical mechanism of Sit protein function predicted from these investigations will then be tested. hyd encodes a HECT family E3 ubiquitin ligase that is required to prevent premature photoreceptor differentiation, hh expression, and overgrowth of surrounding wildtype cells. A combination of genetic and biochemical approaches will be used to test whether the normal function of Hyd is to block Hh expression or signaling, and to identify proteins ubiquitinated by Hyd. The function of hyd in the development of other tissues will also be determined. Finally, the mosaic genetic screen will be expanded to cover another 20 percent of the genome. Mutations required for cells in the eye disc to differentiate as retinal tissue will be isolated, placed into complementation groups and mapped. The phenotypes of the novel genes will be characterized and the most interesting candidates will be selected for molecular analysis. The results of this study are likely both to provide a more complete understanding of the process of eye development in Drosophila, and to uncover mechanisms and molecules that contribute to development and are misregulated in disease in higher organisms.