Central scaffolding component of the centrioles ensuring their 9-fold symmetry (PubMed:17412918, PubMed:17463247, PubMed:30013109). Required for centrosome biogenesis and duplication (PubMed:17412918, PubMed:17463247, PubMed:30013109, PubMed:33704067). In ciliated neurons, required for centriole assembly but not necessary for cilium basal body and cilia function (PubMed:30013109). Required for sperm cilium basal body elongation together with Cep135 and Ana2 (PubMed:30013109). Nine homodimers form a cartwheel structure with an internal diameter of 23 nM and radial spokes connecting to the microtubule triplets (By similarity). Homodimer (PubMed:33704067). Interacts with Gorab (via C-terminus); binds as a homodimer to a Gorab monomer (PubMed:29892014, PubMed:33704067). Component of the centrosome. Expressed in spermatocyte and speratids (at protein level). After pupae formation, expressed during centriole-to-cilium basal body conversion and in the early phase of ciliogenesis in neurons, then disappears (at protein level). The 35 nM long coiled-coil domain mediates homodimerization while the globular N-terminus links the dimers at an angle of 40 degrees to form the inner ring. Results in lack of centrioles and cilium formation, defects in coordination and reduced fertility (PubMed:30013109, PubMed:33704067). In neurons, RNAi-mediated knockdown after centriole assembly does not affect neuronal cilium basal body, cilia formation or movement coordination (PubMed:30013109). In spermatocytes, RNAi-mediated knockdown before centriole biogenesis results in reduced centriole numbers and fertility (PubMed:30013109). On the contrary RNAi-mediated knockdown after centriole biogenesis does not affect the number of centrioles, but affects maturation of a full-length cilium basal body and reduces fertility (PubMed:30013109).