MECP2 and Rett syndrome: RTT iPSC-derived neurons exhibit maturation and electrophysiological defects reminiscent of those seen in RTT patients and mouse models (Cheung et al., 2012; Farra et al., 2012) and are amenable to rescue by introduction of exogenous MECP2 or drugs such as IGF1 (Li et al., 2013; Marchetto et al., 2010).