Sohlh2 is a germ cell-specific bHLH transcription factor.

Germ cell-specific transcriptional regulation is essential to understand pathways that confer germ cells their unique biology. Germ cell-specific transcription factors such as Figla and Nobox are critical in oogenesis, while Zfp148 and Taf4b are also critical in spermatogenesis. Identification and characterization of the full complement of germ cell-specific transcription factors is necessary to understand germ cell-specific regulatory networks. Here, we describe a discovery of a novel spermatogenesis- and oogenesis-specific basic helix-loop-helix (bHLH) transcription factor, Sohlh2. Sohlh2 is expressed both in the male and female germline. In females, Sohlh2 transcripts are detectable in the female embryonic gonad but confined to oocytes of small follicles in the immature ovary. In adult ovaries, SOHLH2 protein is present in primordial follicles but not detected in growing oocytes. SOHLH2 expression in testes is confined to spermatogonia. The expression pattern of SOHLH2 suggests that it may be a critical regulator of early germ cell development.