SOX2, also known as ANOP3, 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 ZFP26. SOX2 is critical for early embryogenesis and for embryonic stem cell pluripotency. It keeps neural cells undifferentiated by counteracting the activity of proneural proteins and suppresses neuronal differentiation. Defects in SOX2 can cause microphthalmia, syndromic, 3. A disease characterized by the rare association of malformations including uni- or bilateral anophthalmia or microphthalmia, and esophageal atresia with trachoesophageal fistula.