Required for ciliary motility (By similarity). Required for localization of SPEF2 to the ciliary axoneme in ciliated respiratory epithelial cells (PubMed:31545650). {ECO:0000250|UniProtKB:Q80W93, ECO:0000269|PubMed:31545650}. This is the function of HYDIN (HYDIN axonemal central pair apparatus protein, Ensembl gene identifier ENSG00000157423).