Plays a role in the formation of the central complex of ciliary and flagellar axonemes. Homodimer (By similarity). Interacts with SUN5 (PubMed:29298896). Localizes both to epithelial motile cilium and the sperm flagellum (By similarity). In spermatids, rapidly enriched in the coupling apparatus with the elongation of the spermatid. Tightly attached to the implantation fossa during the maturation of the spermatid. In mature spermatzoa evenly distributed along the flagellum at the radial spoke of the axoneme (PubMed:29298896, PubMed:19919626). Expressed in ciliated cell-containing tissues such as testis, brain, lung, ovary and oviduct. Expressed during spermiogenesis.