MECP2 and obesity due to melanocortin 4 receptor deficiency: Obesity-induced changes in the epigenetic marks of the CNS were investigated in a study by Vuceti et al., (2011) who correlated a decrease in μ-opioid receptor gene expression in reward circuitry of the ventral tegmental area (VTA), NAc and PFC with epigenetic repressive marks such as increased DNA methylation in the promoter and binding sequence of methyl CpG binding protein 2 (MeCP2), increased H3K9 methylation and decreased H3 acetylation in obese mice compared to lean controls.