BBS4 is a core component of the BBSome, a protein complex essential for primary ciliary biogenesis and cargo trafficking 1. BBS4 nucleates pre-BBSome assembly at pericentriolar satellites, with BBS1 subsequently mediating translocation to the ciliary base 2. The BBSome associates with RAB3IP/Rabin8, a guanine exchange factor for Rab8, promoting Rab8-GTP localization to the cilium and enabling docking of carrier vesicles at the ciliary base [UniProt]. BBS4 also regulates sonic hedgehog pathway signaling through SMO ciliary trafficking [UniProt]. Mutations in BBS4 cause Bardet-Biedl syndrome (BBS), an autosomal recessive ciliopathy characterized by retinal dystrophy, obesity, polydactyly, renal dysfunction, and hypogonadism 13. BBS4 represents the third most common genetic cause of BBS after BBS1 and BBS10 3. Beyond ciliary functions, BBS4 exhibits extraciliary roles, regulating expression and secretion of FSTL1, a protein involved in adipogenesis and ciliogenesis, suggesting a regulatory loop relevant to BBS-associated obesity 4. Loss of Bbs4 impairs brown adipocyte thermogenesis and lipid metabolism, demonstrating BBS4's importance in energy homeostasis 5. Human BBS4 successfully rescues all BBS phenotypes in Bbs4 null mice, supporting potential gene therapy approaches for BBS and related ciliopathies 3.