CFAP70 mutations lead to male infertility due to severe astheno-teratozoospermia. A case report

Abstract

The use of high-throughput sequencing techniques has allowed the identification of numerous mutations in genes responsible for severe astheno-teratozoospermia due to multiple morphological abnormalities of the sperm flagella (MMAF). However, more than half of the analysed cases remain unresolved suggesting that many yet uncharacterised gene defects account for this phenotype. Based on whole-exome sequencing data from a large cohort of 167 MMAF-affected subjects, we identified two unrelated affected individuals carrying a homozygous deleterious mutation in CFAP70, a gene not previously linked to the MMAF phenotype. One patient had a homozygous splice variant c.1723-1G>T, altering a consensus splice acceptor site of CFAP70 exon 16, and one had a likely deleterious missense variant in exon 3 (p.Phe60Ile). The CFAP70 gene encodes a regulator protein of the outer dynein arms (ODA) strongly expressed in the human testis. In the sperm cells from the patient carrying the splice variant, immunofluorescence (IF) experiments confirmed the absence of the protein in the sperm flagellum. Moreover, IF analysis showed the absence of markers for the ODAs and the central pair complex of the axoneme. Interestingly, whereas CFAP70 staining was present in sperm cells from patients with mutations in the three other MMAF-related genes ARMC2, FSIP2 and CFAP43, we observed an absence of staining in sperm cells from patients mutated in the WDR66 gene, suggesting a possible interaction between two different axonemal components. In conclusion, this work provides the first evidence that loss of CFAP70 function causes MMAF and that ODA-related proteins may be crucial for the assembly and/or stability of the flagellum axoneme in addition to its motility.

Absence of murine CFAP61 causes male infertility due to multiple morphological abnormalities of the flagella

“…KO males were completely sterile. phological defects and characterized by sperm flagella which are short, coiled, irregular, or even absent-has been associated with a variety of genes in humans and in mice (e.g., AKAP3, AKAP4, AK7, CCDC39, DNAH1, CFAP43, CFAP44, CFAP69, CFAP65, CFAP70, CFAP251, SPATA6, TE KT4, TSSK4, ODF2, ROPN1, FSIP2, TTC21A, and QRICH2) [3,7,[13][14][15][16][17][18][19][20][21][22][23][24][25]27,32,33]. The increasingly large number of such genes emphasizes the extensive genetic heterogeneity of MMAF, strongly suggest that more genes remain to be identified for MMAF.…”

“…Recalling that MMAF phenotype are typified by short, coiled, irregular, or absent flagella, previous studies have established that MMAF flagella can be accompanied with ultrastructure abnormalities of axonemes or can lack outer dense fibers or fibrous sheaths [7,11,14,18]. Previous studies have reported that many infertile males harbor genetic polymorphisms for genes encoding cilia and flagella associated proteins (CFAPs), including CFAP43 (also known as WDR96), CFAP44 (also known as WDR52), CFAP69, CFAP70, CFAP251, and CFAP65, thereby associating these genetic loci with MMAF phenotype and disarrangement of 9 peripheral microtubule doublets alongside 2 central microtubules [14,18,21,22,25,27,32]. QRICH2 ablation causes similar phenotype [33].…”

“…Therefore, different mutant mouse models have been developed to study the genetic and molecular causes of sperm developmental defects, yielding deep understanding regarding spermatogenesis [12]. Previous studies in human and mutant mouse models have investigated and identified several genes associated with flagella abnormalities including AKAP3, AKAP4, AK7, CCDC39, DNAH1, CFAP43, CFAP44, CFAP69, CFAP65, CFAP70, CFAP251, SPATA6, TEKT4, TSSK4, ODF2, ROPN1, FSIP2, R2D2, TTC21A and QRICH2 [3,4,7,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. However, the etiology of several genetic factors responsible for MMAF is still elusive as genetic mutation accounts for 60% of MMAF defects, mirroring the strong genetic heterogeneity which can occur with MMAF [3].…”

Biallelic variants in MAATS1 encoding CFAP91, a calmodulin-associated and spoke-associated complex protein, cause severe astheno-teratozoospermia and male infertility

“…Exome sequencing allowed us to partially elucidate genetic and physiopathological mechanisms leading to sperm flagellum defects. To date, variants in at least 16 genes have been found to be associated with MMAF phenotype 3–17. We however observe that despite regular new gene identification, about two-thirds of MMAF individuals remain unresolved demonstrating the high genetic heterogeneity of this phenotype 4.…”

Genomics of sex allocation in the parasitoid wasp Nasonia vitripennis

“…While no direct studies have been done into the role of CFAP52 in Nasonia sperm, CFAP52 shows high expression levels in N. vitripennis testis [ 60 , 61 ]. Splice region changes could affect the functionality of CFAP52, and because of its role in sperm motility, affect male fertility, as was found for splice variants in other cilia- and flagella-associated proteins in humans (CFAP43/44 and CFAP70 [ 62 , 63 ]). Such an effect could directly impact sex allocation in the haplodiploid N. vitripennis, in which fertilization is the key trigger to female development [ 64 ].…”