EurekAlert -- The Centre for Addiction and Mental Health (CAMH) has discovered a new form of intellectual disability involving mental retardation (MR) along with the eye defect retinitis pigmentosa (RP). CAMH also discovered the previously unidentified gene that causes this disorder, CC2D2A. This scientific advance will help understand the developmental and biological processes involved in brain development, and may help identify ways to diagnose and treat intellectual disabilities. Under the direction of Dr. John Vincent, scientist at CAMH, the team identified a mutation in CC2D2A that causes the production of a shortened protein missing the C2, or calcium-binding, domain. This protein mutation results in faulty cell function, which leads to MR with RP.