MECP2 and Rett syndrome: MeCP2 arginine R106 was detected as methylated in our proteomic screen (Figure 1B) and is found mutated to tryptophan (R106W) or glutamine (R106Q), with very low frequency also to glycine (R106G) and leucine (R106L) in Rett syndrome patients (online RettBASE, (Krishnaraj et al., 2017)).