A better understanding of cilia and their roles in obesity comes from mouse models of BBS and ALMS, as well as by mice carrying mutations in specific GPCRs known to localize to cilia and regulate energy homeostasis, such as melanin-concentrating hormone receptor 1 (MCHR1) and neuropeptide-Y 2 receptor (NPY2R). The gene discussed is MCHR1; the disease is obesity due to melanocortin 4 receptor deficiency.