Figure 7.

Schematic representation of factors affecting self-renewal and differentiation of spermatogonia in mice. Spermatogonia are classified as Asingle (As), Apaired (Apr), and Aaligned (Aal) according to the number of cells contained in a syncytium. In steady-state, a subset of Gfrα1/Nanos2 expressing cells function as stem cells with the ability to self-renew their population. Gfrα1⁺ spermatogonia have the ability to generate cells that lose the expression of Gfrα1 and become Ngn3⁺/Rarγ⁺/Miwi2⁺, which can retain the stem cell potential but mostly become Kit⁺ cells, and therefore are committed to terminal differentiation. In regenerative contexts, Ngn3⁺/Rarγ⁺/Miwi2⁺ can regain Gfrα1 expression contributing to the self-renewing pool.