A Homozygous Ancestral SVA-Insertion-Mediated Deletion in WDR66 Induces Multiple Morphological Abnormalities of the Sperm Flagellum and Male Infertility

摘要

Multiple morphological abnormalities of the sperm flagellum (MMAF) is a severe form of male infertility defined by the presence of a mosaic of anomalies, including short, bent, curled, thick, or absent flagella, resulting from a severe disorganization of the axoneme and of the peri-axonemal structures. Mutations inDNAH1,CFAP43, andCFAP44, three genes encoding axoneme-related proteins, have been described to account for approximately 30% of the MMAF cases reported so far. Here, we searched for pathological copy-number variants in whole-exome sequencing data from a cohort of 78 MMAF-affected subjects to identify additional genes associated with MMAF. In 7 of 78 affected individuals, we identified a homozygous deletion that removes the two penultimate exons ofWDR66(also namedCFAP251), a gene coding for an axonemal protein preferentially localized in the testis and described to localize to the calmodulin- and spoke-associated complex at the base of radial spoke 3. Sequence analysis of the breakpoint region revealed in all deleted subjects the?presence of a single chimeric SVA (SINE-VNTR-Alu) at the breakpoint site, suggesting that the initial deletion event was potentially mediated by an SVA insertion-recombination mechanism. Study ofTrypanosomaWDR66’s ortholog (TbWDR66) highlighted high sequence and structural analogy with the human protein and confirmed axonemal localization of the protein. Reproduction of the human deletion inTbWDR66impaired flagellar movement, thus confirmingWDR66as a gene associated with the MMAF phenotype and highlighting the importance of the WDR66 C-terminal region.