Background Multiple morphological abnormalities of the flagella (MMAF) consistently lead to male infertility due to a reduced or absent sperm motility defined as asthenozoospermia. Despite numerous genes recently described to be recurrently associated with MMAF, more than half of the cases analysed remain unresolved, suggesting that many yet uncharacterised gene defects account for this phenotype
Methods Exome sequencing was performed on 167 infertile men with an MMAF phenotype. Immunostaining and transmission electron microscopy (TEM) in sperm cells from affected individuals were performed to characterise the ultrastructural sperm defects. Gene inactivation using RNA interference (RNAi) was subsequently performed in Trypanosoma.
Results We identified six unrelated affected patients carrying a homozygous deleterious variants in MAATS1, a gene encoding CFAP91, a calmodulin-associated and spoke-associated complex (CSC) protein. TEM and immunostaining experiments in sperm cells showed severe central pair complex (CPC) and radial spokes defects. Moreover, we confirmed that the WDR66 protein is a physical and functional partner of CFAP91 into the CSC. Study of Trypanosoma MAATS1’s orthologue (TbCFAP91) highlighted high sequence and structural analogies with the human protein and confirmed the axonemal localisation of the protein. Knockdown of TbCFAP91 using RNAi impaired flagellar movement led to CPC defects in Trypanosoma as observed in humans.
Conclusions We showed that CFAP91 is essential for normal sperm flagellum structure and function in human and Trypanosoma and that biallelic variants in this gene lead to severe flagellum malformations resulting in astheno-teratozoospermia and primary male infertility.
- reproductive medicine
- molecular genetics
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GM and JB contributed equally.
PR and CCo contributed equally.
Contributors All authors of this manuscript fulfil the criteria of authorship. VS, ED and RZ recruited patients and collected clinical information. CCa, MB, Z-EK, GLG, CK, IG, YF and GP performed molecular analyses. GM and JB performed IF experiments. NT-M performed the bioinformatic analysis. DD, DRR and MB performed the Trypanosoma study. AT and ED performed the TEM experiments. GM, JB, AT, CA, MB, PFR and CCo performed data analysis and interpretation. GM, JB, AT, CA, MB, PFR and CCo designed the study and wrote the manuscript.
Funding This work was mainly supported by the following grants by the Agence Nationale de la Recherche (ANR) (MUCOFERTIL 12-BSV1–0011 and MASFLAGELLA 14-CE15), the LabEx ParaFrap (ANR-11-LABX-0024), the 'Whole genome sequencing of subjects with Flagellar Growth Defects (FGD)' financed by the fondation maladies rares (FMR) for the programme Séquençage à haut débit 2012. The electron microscopy analysis was done in the Bordeaux Imaging Centre, a service unit of the CNRS/INSERM and Bordeaux University, member of the national infrastructure France BioImaging supported by the ANR (ANR-10-INSB-04).
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available on reasonable request.
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