Bi-allelic DNAH8 Variants Lead to Multiple Morphological Abnormalities of the Sperm Flagella and Primary Male Infertility

Abstract

Sperm malformation is a direct factor for male infertility. Multiple morphological abnormalities of the flagella (MMAF), a severe form of asthenoteratozoospermia, are characterized by immotile spermatozoa with malformed and/or absent flagella in the ejaculate. Previous studies indicated genetic heterogeneity in MMAF. To further define genetic factors underlying MMAF, we performed whole-exome sequencing in a cohort of 90 Chinese MMAF-affected men. Two cases (2.2%) were identified as carrying bi-allelic missense DNAH8 variants, variants which were either absent or rare in the control human population and were predicted to be deleterious by multiple bioinformatic tools. Re-analysis of exome data from a second cohort of 167 MMAF-affected men from France, Iran, and North Africa permitted the identification of an additional male carrying a DNAH8 homozygous frameshift variant. DNAH8 encodes a dynein axonemal heavy-chain component that is expressed preferentially in the testis. Hematoxylin-eosin staining and electron microscopy analyses of the spermatozoa from men harboring bi-allelic DNAH8 variants showed a highly aberrant morphology and ultrastructure of the sperm flagella. Immunofluorescence assays performed on the spermatozoa from men harboring bi-allelic DNAH8 variants revealed the absent or markedly reduced staining of DNAH8 and its associated protein DNAH17. Dnah8-knockout male mice also presented typical MMAF phenotypes and sterility. Interestingly, intracytoplasmic sperm injections using the spermatozoa from Dnah8-knockout male mice resulted in good pregnancy outcomes. Collectively, our experimental observations from humans and mice demonstrate that DNAH8 is essential for sperm flagellar formation and that bi-allelic deleterious DNAH8 variants lead to male infertility with MMAF.

Novel loss‐of‐function variants in DNAH17 cause multiple morphological abnormalities of the sperm flagella in humans and mice

“…Recent several years have witnessed a great progress in revealing the responsible genes. At least 19 additional genes, including AK7 , ARMC2 , CFAP43/44 , CFAP69 , FSIP2 , QRICH2 , DNAH17 , TTC21A , WDR66 , CEP135 , TTC29 , CFAP65 , and DNAH8 and so forth, have been reported mutated in patients with MMAF, 9,10 showing the high‐genetic heterogeneity of this phenotype. Nevertheless, it is estimated that the causes for approximately 50% of MMAF patients remain unknown, 11,12 suggesting that more genetic factors and the underlying mechanism need to be explored to completely understand the pathogenesis of MMAF.…”

“…2 Recent several years have witnessed a great progress in revealing the responsible genes. At least 19 additional genes, including AK7, ARMC2, CFAP43/44, CFAP69, FSIP2, QRICH2, DNAH17, TTC21A, WDR66, CEP135, TTC29, CFAP65, and DNAH8 and so forth, have been reported mutated in patients with MMAF, 9,10 showing the high-genetic heterogeneity of this phenotype.…”

Novel variants in DNAH9 lead to nonsyndromic severe asthenozoospermia

“…The pathogenic DNAH9 variants lead to significant decreased DNAH9 at mRNA and protein levels, however, we failed to observe obvious ultrastructure defects in sperm of F1 II-1. This could be due to the complexity of ODA, which composed of several heavy chain proteins, including DNAH5, DNAH8, DNAH11, DNAH17, et al [ 19 , 20 , 24 , 25 ]. These normal proteins can form a seemingly normal ODA structure, however, its dynamic ability damaged dramatically, causing severe asthenozoospermia.…”

Infertility due to defective sperm flagella caused by an intronic deletion in DNAH17 that perturbs splicing

“…Dynein axonemal heavy chains are required for the axonemal assembly and the beating movement of the flagella (Inaba, 2003), (Ben Khelifa et al, 2014), (Tu et al, 2019), (Sironen et al, 2020), (Liu et al, 2020), (Whitfield et al, 2019), (Zhang et al, 2020), (Sha et al, 2020). Pathogenic alleles in human and murine DNAH17 manifest in sperm with an abnormal mitochondrial sheath and cytoplasmic droplets, as well as axonemal disorganization including absence of the central pair and missing peripheral microtubule doublets (Whitfield et al, 2019), (Zhang et al, 2020), .…”