Mechanism of spermatogonial stem cell regulation by ETV2.

摘要

Spermatogenesis is the process through which male germ cells give rise to spermatozoa. Spermatogenesis is initiated from spermatogonial stem cells (SSCs) which self-renew or differentiate to give rise to differentiated progenies of germ cells. Hence understanding of SSC biology is essential to comprehend the complex process of spermatogenesis and has implications in stem cell therapeutics, male infertility and the development of a male contraceptive. Various factors essential for SSC regulation have been recognized. In this thesis we explore the mechanism of SSC loss and consequent infertility of ets variant gene 5 (Etv5) null mice. We show that neonatal expression of ETV5 in testis is essential for SSC maintenance and Etv5 -/- mice lose 80% of SSCs by 3 weeks of age. Etv5 -/- spermatogonial stem/progenitor cells have a decreased proliferation rate, decreased number of type A spermatogonia and decreased daily sperm production which is results in a quantitatively deficient first wave of spermatogenesis. Through real-time PCR of mRNA extracted from whole testes, laser capture microdissected spermatogonial cells, and immunohistochemistry, we show that Etv5-/- spermatogonia have decreased RET expression which could lead to disruption of GDNF/RET/GFRA1 signaling pathway, known to be essential for SSC self-renewal. By using a spermatogonial cell line we investigated the factors that regulate Etv5 in germ cells and found FGF-2 and EGF up-regulate Etv5 mRNA and that FGF-2 mediated up-regulation occurs via the MAPK signaling pathway.