Stem cell factor and c-kit in the mammalian testis: Lessons originating from Mother Nature's gene knockouts

Analysis of mice with naturally occurring mutations in the genes encoding the tyrosine kinase receptor protein, c-kit, and its ligand, stem cell factor (SCF), has implicated these proteins in testicular development and function because of the phenotype of these mice of reduced or absent fertility. Descriptive and functional studies have highlighted the involvement of these proteins in primordial germ cell migration and survival, and in spermatogonial proliferation, survival and adhesion. This review summarises the current knowledge regarding functions of c-kit and SCF in the testis and discusses the implications of information gleaned from other biological systems.