Members of the large SOX family of transcription factors are widely conserved and at least 20 are found in mammals. Structurally SOX proteins exhibit a high mobility group (HMG) motif that binds the DNA minor groove. SOX family members are often found in multiprotein complexes that regulate their ability to affect transcription. SOX proteins play important roles in early development and are often used as markers to assess the differentiation of specific cell lineages.
SOX3 is expressed in the central nervous system from the earliest stages of development. It is one of the earliest neural markers in vertebrates and plays a role in specifying neuronal fate. The SOX3 gene is localized on the X chromosome and is expressed in the brain and gonads. It has been suggested that SOX3 plays a role in brain formation and function. Human and mouse SOX3 share 92% amino acid sequence identity.