THE PAX GENE EGL-38 MEDIATES DEVELOPMENTAL PATTERNING IN CAENORHABDITIS-ELEGANS

Mutations in the C. elegans gene egl-38 result in a discrete set of de fects in developmental pattern formation, In the developing egg-laying system of egl-38 mutant hermaphrodites, the identity of four uterine cells is disrupted and they adopt the fate of their neighbor cells, Li kewise, the identity of two rectal epithelial cells in the male tail i s disrupted and one of these cells adopts the fate of its neighbor cel l, Genetic analysis suggests that the egl-38 functions in the tail and the egg-laying system are partially separable, as different egl-38 mu tations can preferentially disrupt the different functions, We have cl oned egl-38 and shown that it is a member of the PAX family of genes, which encode transcription factors implicated in a variety of developm ental patterning events, The predicted EGL-38 protein is most similar to the mammalian class of proteins that includes PAX2, PAX5 and PAX8, The sequence of egl-38 mutant DNA indicates that the tissue-preferenti al defects of egl-38 mutations result from substitutions in the DNA-bi nding paired domain of the EGL-38 protein, egl-38 thus provides the fi rst molecular genetic insight into two specific patterning events that occur during C. elegans development and also provides the opportunity to investigate the in vivo functions of this class of PAX proteins wi th single cell resolution.