lin-31, a Caenorhabditis elegans HNF-3/fork head transcription factor homolog, specifies three alternative cell fates in vulval development.

Cell-cell signaling controls the specification of vulval cell fates in Caenorhabditis elegans. Although previous studies have identified genes that function at early steps in the signaling pathway, the late steps are not well understood. Here, we begin to characterize those late events by showing that the lin-31 gene acts near the end of the vulval signaling pathway. We show that lin-31 acts downstream of the ras homolog let-60 and that lin-31 encodes a member of the HNF-3/fork head family of DNA-binding transcription factors. lin-31 regulates how vulval precursor cells choose their fate; in lin-31 mutants, these cells do not properly choose which fate to express and therefore adopt any one of the three possible vulval cell fates in a deregulated fashion. This interesting mutant phenotype suggests mechanisms for how vulval cell fates become determined.