BBS1 and obesity due to melanocortin 4 receptor deficiency: Interestingly, the sex difference in the development of obesity observed previously in global knockout and knockin mice [15,18–21] was recapitulated in mice lacking the Bbs1 gene throughout the nervous system, but not when the gene deletion was restricted to the LRb cells suggesting the contribution of cell types other than those expressing the LRb to the sexual dimorphism of obesity in BBS.