Abnormal BCPs or BCP-containing complexes in the nervous system have been shown to cause neurodevelopmental disorders, including neural tube defects (for example, GCN5 or BRD2), mental retardation (for example, BRWD3), Williams syndrome (WS; for example, BAZ1B), Rett syndrome (for example, SWI/SNF), Rett syndrome and Rubinstein-Taybi syndrome (RTS; for example, CBP/p300), and Fragile X syndrome (FRX; for example, CBP/p300). The gene discussed is CREBBP; the disease is atypical Rett syndrome.