Flagella and motile cilia share a 9 + 2 microtubule-doublet axoneme structure, and asthenozoospermia (reduced spermatozoa motility) is found in 76% of men with primary ciliary dyskinesia (PCD). Nevertheless, causal genetic variants in a conserved axonemal component have been found in cases of isolated asthenozoospermia: 30% of men with multiple morphological anomalies of sperm flagella (MMAF) carry bi-allelic mutations in DNAH1, encoding one of the seven inner-arm dynein heavy chains of the 9 + 2 axoneme. To further understand the basis for isolated asthenozoospermia, we used whole-exome and Sanger sequencing to study two brothers and two independent men with MMAF. In three men, we found bi-allelic loss-of-function mutations in WDR66, encoding cilia- and flagella-associated protein 251 (CFAP251): the two brothers were homozygous for the frameshift chr12: g.122359334delA (p.Asp42Metfs∗4), and the third individual was compound heterozygous for chr12: g.122359542G>T (p.Glu111∗) and chr12: g.122395032_122395033delCT (p.Leu530Valfs∗4). We show that CFAP251 is normally located along the flagellum but is absent in men carrying WDR66 mutations and reveal a spermatozoa-specific isoform probably generated during spermatozoon maturation. CFAP251 is a component of the calmodulin- and radial-spoke- associated complex, located adjacent to DNAH1, on the inner surface of the peripheral microtubule doublets of the axoneme. In Tetrahymena, the CFAP251 ortholog is necessary for efficient coordinated ciliary beating. Using immunofluorescent and transmission electron microscopy, we provide evidence that loss of CFAP251 affects the formation of the mitochondrial sheath. We propose that CFAP251 plays a structural role during biogenesis of the spermatozoon flagellum in vertebrates.
American journal of human genetics. 2018 Aug 16 [Epub]
Yasmina Auguste, Valérie Delague, Jean-Pierre Desvignes, Guy Longepied, Audrey Gnisci, Pierre Besnier, Nicolas Levy, Christophe Beroud, André Megarbane, Catherine Metzler-Guillemain, Michael J Mitchell
Aix Marseille Université, INSERM, Marseille Medical Genetics, U 1251, Marseille, France., AP-HM Hôpital de La Conception, Centre Clinico-Biologique d'Assistance Médicale à la Procréation, Centre de Conservation des Œufs et du Sperme Humain, Pôle Femmes-Parents-Enfants, Marseille 13385, France., Centre Hospitalier Universitaire de Nice, Hôpital de l'Archet 2, Laboratoire de Biologie de la Reproduction, UF7740, Nice 06202, France., Institut Jerome Lejeune, Paris 75015, France., Aix Marseille Université, INSERM, Marseille Medical Genetics, U 1251, Marseille, France; AP-HM Hôpital de La Conception, Centre Clinico-Biologique d'Assistance Médicale à la Procréation, Centre de Conservation des Œufs et du Sperme Humain, Pôle Femmes-Parents-Enfants, Marseille 13385, France., Aix Marseille Université, INSERM, Marseille Medical Genetics, U 1251, Marseille, France. Electronic address: .