Function in Germ Cells of c-kit Encoded at the W Locus of Mice

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The genes at the W and S1 loci encode a tyrosine kinase receptor and its ligand, respectively. W and S1 mutations cause defects in development of primordial germ cells and later germ cells, as well as of hematopoietic cells and melanocytes. Dr. Bachvarova has shown that c-kit (encoded at the W locus) is expressed on the surface of oocytes from the stage of stored primordial oocytes through oocyte growth, meiotic maturation, and in development to the 2-cell stage. The principal aim here is to elucidate the role of c-kit in oocyte growth, survival, development and/or adhesion. Expression of ligand in the ovary will be examined by in situ hybridization, immunocytochemistry and functional assays. These results may elucidate what function is involved. She will determine whether functional c-kit is present on oocytes using an immunoprecipitation and autophosphorylation assay. Using in vitro culture systems, she will test whether addition of the ligand promotes aspects of oocyte development. The effect of adding KL to oocytes cultured under suboptimal conditions will be tested, as well as the effect of culture on cell lines expressing transfected or genetically mutated forms of KL. Effects on oocytes growth, survival, and time to undergo meiotic maturation will be examined. She will also determine whether added KL can induce the initiation of oocyte growth in vitro. Finally, she will determine whether blocking antibodies directed against either ligand or receptor can inhibit these processes.