Molecular adapter that recruits protein complexes required for cilium assembly and function to the cilium basal body. At the exit of mitosis, localizes to the basal body and ciliary base of the forming primary cilium where it recruits and activates RAB8A to direct vesicle-mediated transport of proteins to the cilium. Also recruits the BBSome, a complex involved in cilium biogenesis, by bridging it to PCM1 at the centriolar satellites of the cilium. It is also required for the recruitment to the cilium basal body of the intraflagellar transport (IFT) machinery as well as the ciliary appendage proteins CEP164 and NINEIN. Functions as a regulator of Hedgehog signaling both through its role in cilium assembly but also probably through its ability to retain GLI3 within the cytoplasm. It is involved in spermatogenesis through its role in organization of the basal body and assembly of the sperm flagellum. Also indirectly involved in heart development through its function in ciliogenesis.