Plays a role in flagellar formation and sperm motility. Interacts with CFAP47. Expressed in the cytoplasm of the spermatogonia, round spermatids, early elongating spermatids and late elongating spermatids and in the flagella of epididymal spermatozoa. Predominatly expressed in testis (PubMed:31571197). Highly expressed in round and elongating spermatids (PubMed:31571197, PubMed:31413122). Expressed also in certain ciliated organs, such as the brain, lung and kidney (PubMed:31413122). Begins to be significantly expressed at postnatal day 15, reachs a peak at postnatal day 22 and then maintains stable expression level. Deficient male are infertile whereas female mutants could give birth. Deficient male show severe morphological abnormalities of the sperm flagella. The majority of spermatozoa display absent or short flagella and the flagellar axoneme is completely disorganised. Belongs to the CFAP65 family.