Sox-30 encodes a member of the Sox (SRY-related HMG-box) family of transcription factors involved in the regulation of embryonic development and in the determination of the cell fate. Sox-30 is expressed in testis and may act as a transcriptional regulator after forming a protein complex with other proteins. Sox-30 may be involved in the differentiation of developing male germ cells. Two transcript variants encoding distinct isoforms have been identified for the human Sox-30 gene. Sox family transcription factors influence cell differentiation, development and sex determination. Sox-30 contains a unique DNA binding domain, known as the high mobility group (HMG) box, that is related to that of the testis determining gene, SRY. The highly complex group of Sox genes cluster at a minimum of 40 different loci that rapidly diverged in various animal lineages. Several Sox genes have been identified, and members of this family have been shown to be conserved during evolution and to play key roles during animal development.