Negative control of photoreceptor development in Drosophila by the product of the yan gene, an ETS domain protein

Loss-of-function mutations in the yan gene result in the differentiation of supernumerary photoreceptors in the Drosophila eye. The yan gene encodes a protein with an ETS DNA-binding domain that accumulates in the nuclei of undifferentiated cells during the early stages of eye development. Our data suggest that yan functions as a cell-autonomous negative regulator of photoreceptor development; in the presumptive R7 and cone cells, yan appears to act antagonistically to the proneural signal mediated by sevenless and Ras1.