Animal models for the methyl-CpG-binding-protein 2 (MeCP2) disorders Rett syndrome (MeCP2 loss-of-function) and MECP2-duplication syndrome (MeCP2 gain-of-function) in particular have led to a wealth of findings on the molecular biological and neural circuit underpinnings of ASD (Collins et al., 2004; Jiang et al., 2013; Lyst and Bird, 2015; Lu et al., 2016; Sztainberg and Zoghbi, 2016) and identified potential avenues for treatment (Na et al., 2014; Hao et al., 2015; Sztainberg et al., 2015; Achilly et al., 2021). This evidence concerns the gene MECP2 and atypical Rett syndrome.