The monogenic character of RTT, mainly caused by mutations in the MECP2 gene has prompted several RTT animal, and development of cellular (Rastegar et al., 2009; Marchetto et al., 2010; Yazdani et al., 2012; Ezeonwuka and Rastegar, 2014) model systems to study disease mechanism. The gene discussed is MECP2; the disease is Rett syndrome.