CCDC41 is required for ciliary vesicle docking to the mother centriole.

The initiation of primary cilium assembly entails the docking of ciliary vesicles presumably derived from the Golgi complex to the distal end of the mother centriole. Distal appendages, which anchor the mother centriole to the plasma membrane, are thought to be involved in the docking process. However, little is known about the molecular players and mechanisms that mediate the vesicle-centriole association. Here we report that coiled-coil domain containing 41 (CCDC41) is required for the docking of ciliary vesicles. CCDC41 specifically localizes to the distal end of the mother centriole and interacts with centrosomal protein 164 (Cep164), a distal appendage component. In addition, a pool of CCDC41 colocalizes with intraflagellar transport protein 20 (IFT20) subunit of the intraflagellar transport particle at the Golgi complex. Remarkably, knockdown of CCDC41 inhibits the recruitment of IFT20 to the centrosome. Moreover, depletion of CCDC41 or IFT20 inhibits ciliogenesis at the ciliary vesicle docking step, whereas intraflagellar transport protein 88 (IFT88) depletion interferes with later cilium elongation steps. Our results suggest that CCDC41 collaborates with IFT20 to support the vesicle-centriole association at the onset of ciliogenesis.