Strikingly, in mice and humans, mutations in CFAP61, CFAP91, CFAP251, and LRRC23 cause male infertility but not primary ciliary dyskinesia or hydrocephalus, suggesting more differences in the RS3 structure and/or function between sperm flagellum and cilia in multiciliated cells [36–40]. Here, CFAP91 is linked to male infertility.