Cep68 and Cep215 (Cdk5rap2) are required for centrosome cohesion

The centrosome duplicates during the cell cycle but functions as a single microtubule-organising centre until shortly before mitosis. This raises the question of how centrosome cohesion is maintained throughout interphase. One dynamic model proposes that parental centrioles are held together through centriole-associated, entangling filaments. Central to this model are C-Nap1, a putative centriolar docking protein and rootletin, a fibrous component. Here we identify two novel proteins, Cep68 and Cep215, as required for centrosome cohesion. Similar to rootletin, Cep68 decorates fibres emanating from the proximal ends of centrioles and dissociates from centrosomes during mitosis. Furthermore, Cep68 and rootletin depend both on each other and on C-Nap1 for centriole association. Unlike rootletin, overexpression of Cep68 does not induce extensive fibre formation, but Cep68 is readily recruited to ectopic rootletin fibres. These data suggest that Cep68 cooperates with rootletin and C-Nap1 in centrosome cohesion. By contrast, Cep215 associates with centrosomes throughout the cell cycle and does not appear to interact with Cep68, rootletin or C-Nap1. Instead, our data suggest that Cep215 functionally interacts with pericentrin, suggesting that both proteins influence centrosome cohesion through an indirect mechanism related to cytoskeletal dynamics.