The objective of the proposed research is to understand, at the molecular level, the mechanisms underlying the early phases of retinal morphogenesis in Drosophila. This is a complex process by which a simple unpatterned epithelium begins to differentiate into a highly organized retina. The precision with which this developmental process is carried out is critical for achieving a fully functional visual system. Some of the molecules known to be involved in the process have homologues that are likely to execute similar functions during vertebrate retinal development. We will approach this objective by identifying novel genes, by means of a genetic screen, that carry out the various steps required for proper retinal morphogenesis. These genes should include those involved in the adoption and restriction of neural fate, in the appropriate patterning of photoreceptor precursors, and in the propagation of this pattern across the differentiating retinal epithelium. We will characterize these genes and study the phenotypic consequences of their loss and gain of function. This will be carried out by a combination of genetic, molecular, histochemical and, eventually, biochemical methods. This analysis should establish precisely what the roles of the genes are during eye development. Ultimately, these genes will provide useful tools for the process of integration, the goal of which is to establish how the various isolated components work in concert to give rise to the adult retina. Because of the emerging parallels between Drosophila and vertebrate eye development, we believe that the knowledge gained from this and similar studies will be applicable to the normal development of vertebrate retinae as well as to situations of genetic or environmental injury.