NPBWR1 and obesity due to melanocortin 4 receptor deficiency: Furthermore, ob/ob;NPBWR1−/− and Ay/a;NPBWR1−/− double mutant male mice had an increased body weight compared with normal ob/ob or Ay/a male mice, suggesting that the obesity of NPBWR1−/− mice is independent of leptin and melanocortin signaling.