The importance of the identity of NMDAR subtypes (GluN2A versus GluN2B) in humans is illustrated by the phenotypes of patients with mutations in the genes that encode them (GRIN2A and GRIN2B), which include intellectual disability, autism, epilepsy, and schizophrenia (Burnashev and Szepetowski, 2015, Hardingham and Do, 2016). The gene discussed is GRIN2B; the disease is autism.