GENETIC INTERACTIONS WITH RAP1 AND RAS1 REVEAL A 2ND FUNCTION FOR THEFAT FACETS DEUBIQUITINATING ENZYME IN DROSOPHILA EYE DEVELOPMENT

The Drosophila fat facets gene encodes a deubiquitinating enzyme that regulates a cell communication pathway essential very early in eye dev elopment, prior to facet assembly, to limit the number of photorecepto r cells in each facet of the compound eye to eight. The Fat facets pro tein facilitates the production of a signal in cells outside the devel oping facets that inhibits neural development of particular facet prec ursor cells. Novel gain-of-function mutations in the Drosophila Rap1 a nd Ras1 genes are described herein that interact genetically with fat facets mutations. Analysis of these genetic interactions reveals that Fat facets has an additional function later in eye development involvi ng Rap1 and Ras1 proteins. Moreover, the results suggest that undiffer entiated cells outside the facet continue to influence facet assembly later in eye development.