MECP2 and atypical Rett syndrome: Rett syndrome is known to be a disorder of neuronal plasticity (Dani et al., 2005; Zhang et al., 2008; Maliszewska-Cyna et al., 2010) where aberrant expression of receptors and neurotransmitters suggest that MeCP2 is required to maintain synaptic excitation and inhibition that are fundamental to normal circuitry function (Blackman et al., 2012).