MECP2 and Rett syndrome: Numerous studies in animal models of RTT indicate that MeCP2 contributes to the formation and maintenance of neuronal connectivity; MeCP2 deficiency affects neuronal maturation (Matarazzo et al., 2004; Palmer et al., 2008), axonal and dendritic morphology (Belichenko et al., 2008; Chapleau et al., 2009), axonal guidance events (Degano et al., 2009), regulates synapse formation and function, as well as synaptic plasticity (Asaka et al., 2006).