Regulation of GSCs by their local microenvironments. (A) Diagram of a female GSC in the niche microenvironment represented by a cap cell and an escort cell. (B) Diagram of a male GSC attached to the hub. GSCs are attached to cap cells (A) or the hub (B) via E-cadherin-mediated adhesion, and receive local signals from the niche that control their fate. See text for additional details. BMP, bone morphogenetic protein; GSC, germline stem cell; JAK, Janus kinase; STAT, signal transducer and activator of transcription.