Stem cell autotomy and niche interaction in different systems

Figure 12 Short range signalling between germline stem cell and its niche. GDNF is the most important signal produced by the “specialized” basal compartment of SC. Its receptor - c-RET (transmembrane tyrosine kinase receptor) and co-receptor GFRα1, which functions as a glycosylphosphatidylinositol-anchored docking receptor that is needed for GDNF to bind with c-RET - is expressed in GSC, and SFK and Akt pathway are initiated. They control self-renewal and maintenance of GSCs. GSCs also express CSF1R (colony stimulating factor 1 receptor). Its ligand CSF1 is synthesized in “specialized” MCs (sMC) and in leydig cells (LC). Thus, CSF1 may cooperate with GDNF in supporting self-maintenance. Integrins attach the GSCs to the BM and may also contribute to signalling. Red: GSC; Light green: SC; Dark green: sSC domain surrounding the GSC; Purple: Spermatogonium (SG); Dark blue: sMC; Light blue: MC; Light red: BV; Orange: LC; Grey: BM.