Candidate gene for the Cat Eye Syndrome (CES), a developmental disorder associated with the duplication of a 2 Mb region of 22q11.2. Duplication usually takes in the form of a surpernumerary bisatellited isodicentric chromosome, resulting in four copies of the region (represents an inv dup22(q11)). CES is characterized clinically by the combination of coloboma of the iris and anal atresia with fistula, downslanting palpebral fissures, preauricular tags and/or pits, frequent occurrence of heart and renal malformations, and normal or near-normal mental development.