Methyl-CpG-binding protein 2 (MeCP2), which is mutated in Rett Syndrome—one of the most common causes of severe intellectual disability with autistic features in girls (but rarely in boys)—has a high affinity for binding at methylated DNA at CG islands and recruiting transcriptional repressors for gene silencing in the brain [56, 57]. This evidence concerns the gene MECP2 and Intellectual disability.