MECP2 and Rett syndrome: The discovery of mutations in MECP2 (Amir et al., 1999) as the genetic abnormality associated with most cases of RTT, has led to the generation of mutant mouse models that replicate many features of the disorder (Chen et al., 2001; Guy et al., 2001; Nguyen et al., 2013; Ross et al., 2016).