BBS2 and obesity due to melanocortin 4 receptor deficiency: At around 4 months, Bbs1M390R knock-in, Bbs2 −/−, Bbs4 −/−, Bbs6 −/−, and Bbs7 −/− mice developed obesity characterized by hyperphagia (Nishimura et al., 2004; Eichers et al., 2006; Davis et al., 2007; Zhang et al., 2013).