The application of next generation sequencing in a sample of 134 children with autism and developmental regression highlights the roles of single gene variants in MECP2, CDKL5, GRIN2A, SCN1A, PCDH19, UBE3A, and SLC9A6, as well as oligogenic events (variants in EHMT1 and SCL9A6, EHMT1 and MFSD8) that may disrupt multiple biological processes. The gene discussed is MECP2; the disease is autism.