Flagellar protein involved in sperm flagellum axoneme organization and function (PubMed:28552195, PubMed:29449551, PubMed:31884020). Involved in the regulation of the beating frequency of motile cilia on the epithelial cells of the respiratory tract (PubMed:31884020). Expressed in testis (PubMed:28552195). Expressed in the lung, brain, oviduct and nasal cavity (PubMed:31884020). During embryonic development, detected in the left-right organizer at 8.25 dpc and in 17.5 dpc embryos, detected in epithelial cells lining the respiratory tract, brain ependymal cells and the choroid plexus. Mice are viable and show no malformations. However, homozygous males exhibit complete male sterility due to severe defects in sperm mobility. Sperm from mutant mice exhibits teratozoospermia characterized by short, thick, and coiled flagella and sperm axonemal defects. Females are fertile and give litters of normal size (PubMed:28552195, PubMed:29449551, PubMed:31884020). Mice display early onset hydrocephalus and severe mucus accumulation in the nasal cavity (PubMed:31884020). Belongs to the CFAP43 family.