TAF4b is required for mouse spermatogonial stem cell development

Long-term mammalian spermatogenesis requires proper development of spermatogonial stem cells (SSCs) that replenish the testis with germ cell progenitors during adult life. TAF4b is a gonadal-enriched component of the general transcription factor complex, TFIID, which is required for the maintenance of spermatogenesis in the mouse. Successful germ cell transplantation assays into adult TAF4b-deficient host testes suggested that TAF4b performs an essential germ cell autonomous function in SSC establishment and/or maintenance. To elucidate the SSC function of TAF4b, we characterized the initial gonocyte pool and rounds of spermatogenic differentiation in the context of the Taf4b-deficient mouse testis. Here, we demonstrate a significant reduction in the late embryonic gonocyte pool and a deficient expansion of this pool soon after birth. Resulting from this reduction of germ cell progenitors is a developmental delay in meiosis initiation, as compared to age-matched controls. While GFRα1+ spermatogonia are appropriately present as Asingle and Apaired in wild-type testes, TAF4b-deficient testes display an increased proportion of long and clustered chains of GFRα1+ cells. In the absence of TAF4b, seminiferous tubules in the adult testis either lack germ cells altogether or are found to have missing generations of spermatogenic progenitor cells. Together these data indicate that TAF4b-deficient spermatogenic progenitor cells display a tendency for differentiation at the expense of self-renewal and a renewing pool of SSCs fail to establish during the critical window of SSC development.