BBIP1 (BBSome interacting protein 1) is a core component of the BBSome, a protein coat complex essential for primary cilia assembly and ciliary protein trafficking 1. BBIP1 serves as a structural linker within the BBSome, connecting BBS4 and BBS8 subunits and stabilizing the complex 2. The BBSome associates with RAB3IP/Rabin8 at the basal body, facilitating Rab8-GTP activation and subsequent docking of carrier vesicles at the ciliary membrane base 3. BBIP1 also regulates cytoplasmic microtubule stability and acetylation. Loss-of-function mutations in BBIP1 cause Bardet-Biedl syndrome 18 (BBS18), a rare autosomal recessive ciliopathy characterized by retinitis pigmentosa, obesity, kidney dysfunction, postaxial polydactyly, and hypogonadism 1. Multiple pathogenic variants including nonsense mutations (p.Leu58*, p.Lys54Ter) have been identified in BBS patients 14. Unlike primary cilia, photoreceptor cilia can permit partially assembled BBSome complexes lacking BBIP1-dependent components 5, indicating cell-type-specific ciliary trafficking mechanisms. BBIP1's role in BBSome assembly is fundamental to understanding ciliopathy pathogenesis.