The AGTR2 gene, located at Xq22-23, contains 3 exons and encodes for the angiotensin II type 2 (AT2) receptor. However, its physiological function remains unclear, and emerging data suggest that the AT2 receptor may play a role in human cognitive function. Mutations in the AGTR2 gene have been reported in patients with moderate to severe mental retardation accompanied by additional clinical findings, such as seizures and autistic behavior (Vervoort V et al. Science 2002;296:2401-2403).