MECP2 and Rett syndrome: Loss of function of the only known ‘reader’ of mCH in the mammalian brain, Methyl-CpG-binding protein 2 (MeCP2) (Gabel et al., 2015; Guo et al., 2014; Chen et al., 2015), has long been associated with Rett syndrome (RTT) (Amir et al., 1999).