摘要
The continuation of the spermatogenic process through-out life relies on a proper regulation of self-renewal and differentiation ofgermline testis stem cells, the spermatogonial stem cells. These are single cells situated on the basal membrane of the seminiferous epithelium. Only 0.03% of all germ cells are spermatogonial stem cells （SSCs） [1-3]. To maintain spermatogenesis, the processes of self-renewal and differentiation of S SCs must be precisely regulated by intrinsic gene expression in the stem cells and extrinsic signals, including soluble factors or adhesion molecules from the surrounding microenvironment, the stem cell niche.
