The ternary complex CEP90, FOPNL and OFD1 specifies the future location of centriolar distal appendages, and promotes their assembly

Cilia assembly starts with centriole to basal body maturation, migration to the cell surface and docking to the plasma membrane. The basal body docking process involves the interaction of both the distal end of the basal body and the transition fibers (or mature distal appendages), with the plasma membrane. During this process, the transition zone assembles and forms the structural junction between the basal body and the nascent cilium. Mutations in numerous genes involved in basal body docking and transition zone assembly are associated with the most severe ciliopathies, highlighting the importance of these events in cilium biogenesis. The conservation of this sequence of events across phyla is paralleled by a high conservation of the proteins involved. We identified CEP90 by BioID using FOPNL as a bait. Ultrastructure expansion microscopy showed that CEP90, FOPNL and OFD1 localized at the distal end of both centrioles/basal bodies in Paramecium and mammalian cells. These proteins are recruited early after duplication on the procentriole. Finally, functional analysis performed both in Paramecium and mammalian cells demonstrate the requirement of this complex for distal appendage assembly and basal body docking. Altogether, we propose that this ternary complex is required to determine the future position of distal appendages. ### Competing Interest Statement The authors have declared no competing interest.