MECP2 and Rett syndrome: Yet, despite the functional relevance to RTT attributed to the MeCP2 NID (Tillotson et al., 2017), and despite the main functional role of MeCP2 in the brain being to recruit the NCoR1/2 co-repressor complex to methylated DNA sites in this tissue (Tillotson and Bird, 2019), mutations within this region correspond to some of the clinically milder RTT forms reported (Schanen et al., 2004; Cuddapah et al., 2014; Neul et al., 2014).