MeCP2 is a chromosomal protein with abundant binding sites in the chromatin. It belongs to the family of methyl CpG binding proteins which also comprises MBD1, MBD2, MBD3 and MBD4. MeCP2 can bind specifically to methylated promoters, thereby repressing transcription. This transcriptional repression is mediated through interaction with histone deacetylase and the corepressor SIN3A. MeCP2 also is essential for development. Mutations in MeCP2 are the cause of several types of mental retardation including Rett syndrome, a progressive neurological disorder that causes mental retardation in females and mental retardation syndromic X-linked type 13, and may also be involved in Angelman syndrome and susceptibility to some types of autism.