Required for assembly of dynein regulatory complex (DRC) and inner dynein arm complexes, which are responsible for ciliary beat regulation, thereby playing a central role in motility in cilia and flagella. Not required for outer dynein arm complexes assembly. Required for axonemal recruitment of CCDC39.Involvement in disease:Defects in CCDC40 are the cause of primary ciliary dyskinesia type 15 (CILD15) . A disorder characterized by abnormalities of motile cilia. Respiratory infections leading to chronic inflammation and bronchiectasis are recurrent, due to defects in the respiratory cilia; reduced fertility is often observed in male patients due to abnormalities of sperm tails. Half of the patients exhibit randomization of left-right body asymmetry and situs inversus, due to dysfunction of monocilia at the embryonic node. Primary ciliary dyskinesia associated with situs inversus is referred to as Kartagener syndrome.