Bi-allelic Mutations in TTC29 Cause Male Subfertility with Asthenoteratospermia in Humans and Mice

Abstract

As a type of severe asthenoteratospermia, multiple morphological abnormalities of the flagella (MMAF) are characterized by the presence of immotile spermatozoa with severe flagellar malformations. MMAF is a genetically heterogeneous disorder, and the known MMAFassociated genes can only account for approximately 60% of human MMAF cases. Here we conducted whole-exome sequencing and identified bi-allelic truncating mutations of the TTC29 (tetratricopeptide repeat domain 29) gene in three (3.8%) unrelated cases from a cohort of 80 MMAF-affected Han Chinese men. TTC29 is preferentially expressed in the testis, and TTC29 protein contains the tetratricopeptide repeat domains that play an important role in cilia-and flagella-associated functions. All of the men harboring TTC29 mutations presented a typical MMAF phenotype and dramatic disorganization in axonemal and/or other peri-axonemal structures. Immunofluorescence assays of spermatozoa from men harboring TTC29 mutations showed deficiency of TTC29 and remarkably reduced staining of intraflagellar-transport-complex-B-associated proteins (TTC30A and IFT52). We also generated a Ttc29-mutated mouse model through the use of CRISPR-Cas9 technology. Remarkably, Ttc29-mutated male mice also presented reduced sperm motility, abnormal flagellar ultrastructure, and male subfertility. Furthermore, intracytoplasmic sperm injections performed for Ttc29-mutated mice and men harboring TTC29 mutations consistently acquired satisfactory outcomes. Collectively, our experimental observations in humans and mice suggest that bi-allelic mutations in TTC29, as an important genetic pathogeny, can induce MMAF-related asthenoteratospermia. Our study also provided effective guidance for clinical diagnosis and assisted reproduction treatments.

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

“…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.…”

“…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.…”

The Role of Genetics and Oxidative Stress in the Etiology of Male Infertility—A Unifying Hypothesis?

“…These mutations generate isolated male infertility associated with severe asthenozoospermia in the absence of any other pathology and are known collectively as Multiple Morphological Abnormalities of the sperm Flagella (MMAF). The list of mutations responsible for MMAF is expanding rapidly but currently includes mutations in adenylate kinase 7 ( AK7 ) ( 36 ), glutamine rich 2 ( QRICH2) ( 37 ), cilia and flagella associated proteins ( CFAP43, CFAP44, CFAP65, CFAP69, CFAP70, CFAP91, CFAP251 ) ( 38 – 44 ) WD repeat domain 19 ( WDR19 ) ( 45 ), DAZ interacting zinc finger protein ( DZIP1 ) ( 46 ), DNAH1 (also implicated in PCD) ( 47 ) DNAH2 ( 48 ), DNAH6 ( 49 ), DNAH17 ( 50 ), TTC29 ( 51 ), TTC21A ( 52 ), armadillo repeat containing 2 ( ARMC2 ) ( 53 ) CEP135 (centrosomal protein 135) ( 54 ). fibrous sheath interacting protein 2 ( FSIP2 ) ( 55 ), ADP ribosylation factor like GTPase 2 binding protein ( ARL2BP ) ( 56 ), sperm flagellar 2 ( SPEF2 ) ( 57 ), and DnaJ heat shock protein family ( Hsp40 ) member B13 ( DNAJB13 ) ( 58 ).…”

Essential role of CFAP53 in sperm flagellum biogenesis

“…Previous studies have identified several flagella-associated genes, including AKAP3, AKAP4, TTC21A, TTC29, FSIP2, DNAH1, DNAH2, DNAH6, DNAH8, DNAH17 , and DZIP1 , that are involved in sperm flagellum biogenesis (Ben Khelifa et al, 2014; Y. Li et al, 2019; C. Liu et al, 2019; C.…”

“…Liu et al, 2019; C. Liu et al, 2020; W. Liu et al, 2019; Lv et al, 2020; Martinez et al, 2018; Sha, Wei, et al, 2020; Tu et al, 2019; Turner et al, 2001).…”