MECP2 and atypical Rett syndrome: A recent functional study using ASD brain samples demonstrated that GABRB3 is subject to epigenetic dysregulation: the product of the MECP2 gene, which when mutated can cause Rett syndrome, binds to methylated CpG sites within GABRB3 and acts as a chromatin organizer for optimal expression of both alleles of GABRB3 in neurons [35].