Transcription regulator of both male and female germline differentiation. Suppresses genes involved in spermatogonial stem cells maintenance, and induces genes important for spermatogonial differentiation. Coordinates oocyte differentiation without affecting meiosis I (By similarity). {ECO:0000250|UniProtKB:Q6IUP1, ECO:0000250|UniProtKB:Q9D489}. This is the function of ENSG00000120669 (SOHLH2, spermatogenesis and oogenesis specific basic helix-loop-helix 2).