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, ECO:0000269|PubMed:20506135}. This is the function of SOHLH1 (spermatogenesis and oogenesis specific basic helix-loop-helix 1, Ensembl gene identifier ENSG00000165643).