MC4R and obesity due to melanocortin 4 receptor deficiency: How primary cilia on these neurons regulate food intake is poorly understood, but several G-protein coupled receptors (GPCRs) have been found to preferentially localize to primary cilia, including melanin concentrating hormone receptor 1 (Mchr1) and melanocortin receptor 4 (Mc4r), both of which are expressed in the hypothalamus along with their ligands, MCH and alpha-melanocyte stimulating hormone (α-MSH), respectively, and have established roles in feeding behavior and obesity (Desy and Pelletier, 1978; Bittencourt et al., 1992; Berbari et al., 2008a; Siljee et al., 2018).