Component of the centrioles that acts as a positive regulator of centriole elongation (PubMed:24997988). Promotes assembly of centriolar distal appendage, a structure at the distal end of the mother centriole that acts as an anchor of the cilium, and is required for recruitment of centriolar distal appendages proteins CEP83, SCLT1, CEP89, FBF1 and CEP164. Not required for centriolar satellite integrity or RAB8 activation (PubMed:24469809). Required for primary cilium formation. Required for sonic hedgehog/SHH signaling and for proteolytic processing of GLI3 (PubMed:19004860). Interacts with OFD1; OFD1 may act as a negative regulator of C2CD3. Associates with the BBSome complex (By similarity). Interacts with IFT88, BBS4 and PCM1. Localizes to centrioles and procentrioles both in interphase and mitosis. Localizes to centriolar satellites, localization is dependent on PCM1 and dynein-mediated retrograde transport. Also localizes to the distal ends of the mother and daughter centrioles (PubMed:24469809). Ubiquitously expressed in embryos between 8.5 dpc and 10.5 dpc. Embryonic lethality between 11 dpc and 13 dpc. Embryos show multiple defects including neural tube defects, abnormal dorsal-ventral patterning of the spinal cord, a defect in left-right axis determination and severe polydactyly (extra digits). Truncated N-terminus.