TFAP2B and obesity due to melanocortin 4 receptor deficiency: As we mentioned previously, AP-2β represses the expression of 5-HTT [19, 20, 101] and 5-HTT gene promotor methylation is associated with reward and eating behaviour as well as human obesity [147] and suppression of 5-HTT, by hypermethylation, in humans is associated with a high prevalence of obesity [148].