MECP2 and atypical Rett syndrome: Mecp2-null mice, an animal model for Rett syndrome, recapitulate most symptomatic traits of Rett syndrome such as respiratory dysfunction, forelimb and hindlimb clasping stereotypy, motor dysfunction, tremor, hypoactivity, anxiety, cognitive impairments, and altered sociability (Table 4) (Shahbazian et al., 2002; Moretti et al., 2005).