Involved in sperm flagellum axonemal organization and function (PubMed:12223483, PubMed:32161152). May regulate cilium motility through its role in the assembly of the axonemal radial spokes (By similarity). Interacts with MYCBP and AKAP1. Part of a complex containing MYCBP, AKAP1 and PRKAR2B. Does not interact with MYCBP. Localized in the neck of the sperm. Additional isoforms may exist. Strongly expressed in the liver. Widely expressed, but strongly expressed in all spermatogenesis-related tissues, including the testis, the epithelium of cauda and the corpus epididymis, as well as the spermatid and mature sperm. Also expressed in Leydig cells. Phosphorylated by PKA. The disease is caused by variants affecting the gene represented in this entry. May be produced by alternative promoter usage. Belongs to the CFAP91 family. Truncated N-terminus.