User:SWhittley96/sandbox

Spermatogonial Stem Cell Self-Renewal
Peritubular myoid cells play a crucial role in the self-renewal and maintenance of the spermatogonial stem cell (SSC) population. For undifferentiated SSCs destined to further develop and form progenitor A1 spermatogonia (and hence spermatozoa), this is initiated at a defined stage during the spermatogenic cycle. The precise location of SSCs throughout various staged cohorts of the seminiferous tubule determines their renewal function, to continuously produce progeny. During stages II and IV of spermatogenesis, GDNF is secreted by peritubular myoid cells upon testosterone binding the androgen receptor (in contrast to GDNF secretion by the Sertoli cells during stages IX and I). Following this, GDNF binds GFRA1 on spermatogonial stem cells, and RET co-receptor (a transmembrane tyrosine kinase) is consequently signalled throughout all undifferentiated spermatogonia. Thus, SFK signalling is upregulated and genes encoding key transcription factors (bcl6b, brachyury, Id4, Lhx1) become activated. The histochemical marker, alkaline phosphatase (stimulated by testosterone and retinol) has been useful for investigating peritubular myoid cell function and differentiation, as it has been shown to have activity in the peritubular myoid cell of the rat.

This is my sandbox.