SOHLH1 is a basic helix-loop-helix (bHLH) transcription factor that is invovled in spermatogenesis and oogenesis [, ]. The transcription of the Sohlh1 gene is regulated by the SOHLH2/SOHLH1/SP1 complex [].The bHLH (basic Helix-Loop-Helix) proteins contain the bHLH domain that is approximately 60 amino acids long and consists of a DNA-binding basic region followed by two a-helices separated by a variable loop region (HLH). The HLH domain promotes dimerisation, allowing the formation of homo- or heterodimeric complexes between different family members. Many bHLH proteins have been shown to act as transcriptional regulators [].