SOX2 is a transcription factor that forms a trimeric complex with OCT4 on DNA and controls the expression of a number of genes involved in embryonic development such as YES1, FGF4, UTF1 and ZFP206. SOX-2 is critical for early embryogenesis and for embryonic stem cell pluripotency. SOX 2, also known as SRY related HMG BOX gene 2, belongs to the the SOX (SRY-box containing gene) gene family which encodes a group of transcription factors defined by the conserved high motility group (HMG) DNA-binding domain. All SOX proteins have a single HMG box and bind linear DNA in a sequence-specific manner, resulting in the bending of DNA through large angles. Bending causes the DNA helix to open for some distance, which may affect binding and interactions of other transcription factors. SOX1, SOX2 and SOX3 show the closest homology to SRY. These SOX proteins share maximum homology within the HMG domain and are expressed mainly in the developing nervous system of the mouse. These genes share significant homology outside the HMG box also and are highly conserved throughout their evolution.