Mutations of MECP2 (methyl-CpG binding protein 2) cause Rett syndrome (RTT). Mouse genetics studies have demonstrated that the lack of functional MeCP2 in the central nervous system leads to RTT-like symptoms, which could be reversed upon MeCP2 restoration. MeCP2 recognizes methylated CpG dinucleotides and may interact with other chromatin remodeling proteins. Although traditionally thought to be a transcription repressor, MeCP2 may also be involved in transcription activation. With the development of new technologies, deciphering the role of MeCP2 on a genome-wide scale is important for understanding of the RTT disease mechanisms.