PATTERN FORMATION IN THE DROSOPHILA EYE DISC

果蝇眼睛的发育是一个遗传上可适应的过程，与脊椎动物的眼睛发育共享保守的机制。除了具有许多其他发育功能外，Hedgehog （Hh）信号通路在果蝇和脊椎动物的早期眼睛发育中起着至关重要的作用。使用镶嵌方法筛选影响果蝇眼盘早期模式形成的突变，以分离具有额外胚胎功能的基因。在这个筛选中分离的两个基因，失明（sit）和增生性椎间盘（hyd），似乎对Hh信号有相反的影响。目前的建议旨在表征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，并使用遗传学方法确定其在Hh通路中的位置。从这些研究中预测的Sit蛋白功能的生化机制将进行测试。hyd编码HECT家族E3泛素连接酶，这是防止周围野生型细胞过早的光受体分化、hh表达和过度生长所必需的。遗传学和生物化学方法的结合将用于测试Hyd的正常功能是否阻断Hh表达或信号传导，并识别被Hyd泛素化的蛋白。hyd在其他组织发育中的作用也将被确定。最后，马赛克基因筛选将扩大到另外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，放入互补组并绘制。新基因的表型将被表征，最有趣的候选基因将被选择进行分子分析。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理解，也揭示了在高等生物中促进发育和疾病失调的机制和分子。

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.