Targeted disruption of the Brd2 gene, which is present in the class II major histocompatibility complex (MHC) nearer to Tnf, results in extreme obesity with hyperinsulinemia, as well as hypoglycemia, hyperadiponectinemia, and improved glucose tolerance, which is quite different from other animal models of obesity [24,25]. Here, BRD2 is linked to obesity due to melanocortin 4 receptor deficiency.