Expression of mouse VASA-homologue protein in testicular germ cells

In mammals, the expression of the VASA homologue protein becomes obvious in primordial germ cells (PGCs) at the late migrating stage. During the process of spermatogenesis, the intracellular localization of VASA protein is closely related with the chromatoid body. To understand the expression of germ cell markers, we have analyzed VASA protein in the testis section and testicular culture. The immunohistochemical analyses demonstrated that VASA protein was exclusively expressed in the seminiferous tubules of the testis. The germ stem cell (GSCs) colonies were established after digestion of the testis and characterized by electron microscope analyses (EM). EM made evident that GSCs colonies showed a high nucleus/cytoplasm ratio. The immunohistochemical analysis confirmed that VASA protein was localized in the cytoplasm of GSCs. The results of Fluidigm RT-PCR revealed a high expression of the germ cell gene VASA in GSCs and a low expression in testicular stroma cell (TSC) feeders and mouse embryonic stem cells (ESCs). The VASA gene is thus a highly specific marker of testicular germ cells and should be beneficial for studies of germ cell determination and function.