MECP2 and atypical Rett syndrome: In studies using MeCP2 null mutant mice as a model of Rett syndrome (Chen et al., 2001), conditional MeCP2 expression in postnatal neurons partly reversed behavioral abnormalities (Giacometti et al., 2007; Guy et al., 2007), indicating involvement of reduced neural MeCP2 in pathogenesis of the model.