NRXN3 and obesity due to melanocortin 4 receptor deficiency: Several of the likely causal obesity genes identified through GWAS studies (FTO, MC4R, POMC, SH2B1, BDNF, NPC1, NRXN3 and NEGR1) are highly expressed or known to act in the central nervous system, indicating a key role for central regulation of food intake in obesity susceptibility in line with monogenic forms of human obesity [64, 104].