Ras proteins in developmental pattern formation in Caenorhabditis elegans and Drosophila.
Recent studies of genetically isolated mutants in Caenorhabditis elegans and Drosophila have revealed ras functions in developmental pattern formation. The ras proteins act as genetic switches to determine cell fates between two alternative choices during C elegans vulval development (vulval versus hypodermal cells) and during Drosophila eye development (R7 versus cone cell). In both cases, ras proteins act downstream of a receptor tyrosine kinase in a signal transduction pathway that mediates cell-cell interactions. These genetic systems may allow the further elucidation of ras-mediated developmental regulatory pathways.