Spermatogonial stem cell self-renewal in the mouse

In males, germ cell homeostasis is maintained by self-renewal and differentiation of a robust stem cell population. However, it is unknown how mammalian spermatogonia accomplish this task. It has been assumed that germline stem cells divide symmetrically, whereby As spermatogonia give rise to As cells with similar stem cell potential or a pair of cells connected by cytoplasmic bridges (Apr) that undergo differentiation. The Braun lab has identified a T-box transcription factor EOMES and cell cycle marker Ki67 that localizes asymmetrically in clones of GFRA 1 + cells. Immunohistochemical analysis using GFRA 1 antibody on wholemount seminiferous tubules suggests that there is symmetrical and asymmetrical localization of EOMEStdTOMATo in Apr cells in the steady-state. Prel iminary data suggests that symmetrical localization of EOMEStdTOMATo in the GFRA 1 paired population increases during regeneration. Despite the increase in GFRA 1 cycl ing population during regeneration, there was no significant change in the frequency of asynchronous and synchronous in GFRA 1 + clones. To further test the hypothesis if selfrenewal is asymmetrical, we would trace the progeny of EOMES+ cells with the tamoxifen-inducible Eomes knockin mouse line crossed to a dual reporter, which would allow us to observe if there is a correlation between asynchrony and asymmetrical localization of EOMES and other proteins important for maintaining stem cell fate