Stem cell autotomy and niche interaction in different systems

Figure 11 Organization of the mammalian testicular germline stem cell niche (adapted from Yoshida[131]). The seminiferous tubules exist of large sertoli cells (SC) and spermatocytes (SPC). The putative germline stem cell (GSC) is located at the basement membrane (BM) at an interstitium. It is in close vicinity of a blood vessel (BV) and leydig cells (LC). Myoid cells (MC) that line the BM are thought to be “specialized” MC (sMC) below the GSC. The basal part of the SC that surrounds the GSC presumably performs a specialized “domain” acting as (the main) part of the complex niche. The niche allegedly consists of several additional entities besides the specialized SC domain: the BM, the sMC, the BV, the LC and probably others (see text). Tight junctions (arrow) between SCs establish a blood-testis barrier: GSCs and spermatogonia are exposed to the vascular system, whereas primary spermatocytes (SPC) and the following stages of Spermatogenesis proceed behind the barrier. dSPT: Differentiating spermatid; SP: Spermatozoon; N: Nucleus of SC; Red: GSC; Light green: SC; Dark green: sSC domain surrounding the GSC; Purple: Spermatogonia and different stages of spermatogenesis; Dark blue: sMC; Light blue: MC; Light red: BV; Orange: LC; Grey: BM.