MECP2 and atypical Rett syndrome: Rett syndrome is induced by loss-of-function mutations in the transcriptional regulator gene MECP2. MECP2 is an activity-dependent transcriptional repressor protein that acts by binding to methylated CpG dinucleotides and induces remodeling of the chromatin structure (Nan et al., 1997; Amir et al., 1999; Cohen et al., 2011).