The function of CFAP251 (cilia and flagella associated protein 251, Ensembl gene identifier ENSG00000158023) is as follows. Involved in spermatozoa motility (PubMed:30122540, PubMed:30122541). May also regulate cilium motility through its role in the assembly of the axonemal radial spokes (By similarity). {ECO:0000250|UniProtKB:A8IRK7, ECO:0000250|UniProtKB:Q24DE2, ECO:0000269|PubMed:30122540, ECO:0000269|PubMed:30122541}.