RB1 and obesity due to melanocortin 4 receptor deficiency: Fifteen positional candidate genes were associated with adipose tissue development, energy and lipid metabolism: SLC41A2, SLC37A3, SLC25A6, SLC29A1, SLC1A6, SLC35B1, AKR1D1, ANGPTL4 [58], RB1 [59, 60], CHST11 [61], PMCH [62], NR4A2 [63], HTR2A [64], KCNJ5 and KCNJ1. It is important to highlight that SLC41A2, SLC37A3, SLC25A6, SLC29A1, SLC1A6 and SLC35B1 belong to the solute carrier family already known to be associated with energy metabolism [36, 65–67] and obesity in humans [68, 69].