MECP2 and atypical Rett syndrome: Rett syndrome, an X-linked neurological disease characterized clinically by distinctive hand movements, seizures, delayed brain and head growth, autism, and mental retardation (Weng et al., 2011), is caused by mutations in a transcription factor, methyl-CpG-binding protein 2 (MeCP2; Samaco and Neul, 2011).