MECP2 and atypical Rett syndrome: Mice lacking Mecp2 can reproduce various Rett syndrome (RTT) phenotypes, including motor dysfunction, anxiety behavior, abnormal social behavior as well as impaired learning and memory (Shahbazian et al., 2002; Gemelli et al., 2006; Adachi et al., 2009; Ito-Ishida et al., 2015; Chao et al., 2010; Fyffe et al., 2008; Chen et al., 2001; Guy et al., 2001; Moretti et al., 2006).