POMC and obesity due to melanocortin 4 receptor deficiency: In subjects with obesity of all ages, reprogramming of DNA methylation in PPARGC1A (the gene encoding PGC1, a master regulator of biogenesis and mitochondrial function) as well as hypermethylation of the proopiomelanocortin (POMC) promoter of intron 2/exon 3 in the melanocortin system have also been observed.