The Sex Determining Protein Phosphatase of Caenorhabditis elegans Fem-2.

Checkland, T., Stothard, P., and Pilgrim D.

Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.

We have been examining the protein phosphatase FEM-2, which is involved in sex determination in the nematode C.elegans. We have recently focused on three aspects of FEM-2 biology. First, does the sex determining protein FEM-2 have an accelerated rate of evolution? Second, does the expression pattern of the protein match the mutant phenotype and third, what do the mutant alleles tell us about the function of the protein? To assess whether different selective pressures act on sex-determining proteins we characterised the orthologs of three C.elegans genes from the related nematode C.remanei. All three are predicted to encode proteins that belong to the protein phosphatase 2C superfamily. One gene encodes FEM-2 while the others have no known sex-determining role. Comparison of the C.remanei sequences with their C.elegans orthologs indicates that the FEM-2 PP2C domain is much more divergent than the same domain in the other proteins. PP2C sequences from the zebrafish, Danio rerio, were compared to their mouse orthologs. The zebrafish/mouse PP2C domains are more conserved than the FEM-2 PP2C domain, but less conserved than the other Caenorhabditis PP2Cs. Experiments using transgenes suggest that C.remanei and C.briggsae fem-2 are able to promote male somatic but not germline development in C.elegans. To better understand how fem-2 regulates sexual development we have raised antisera against the FEM-2 protein. The antisera can specifically detect FEM-2 on Western blots, and it stains sexually dimorphic structures in whole animals. We are currently looking for differences in staining between wild-type animals and animals mutant for other sex determining genes. Finally, function studies of two temperature sensitive missense alleles are underway. These two alleles are being characterised in vivo as well as through in vitro protein studies.