1 INTRODUCTION
The etiology of male infertility is highly heterogeneous, and genetic
factors account for at least 15% of cases (Jiao et al., 2021). The
integrity of the flagella is crucial for sperm motility, and any
structural and functional defects of sperm flagella could impair sperm
function, which is indispensable for spontaneous fertilization (Inaba et
al., 2011). Multiple morphological abnormalities of the sperm flagella
(MMAF) is a rare asthenoteratozoospermia with severely impaired sperm
motility (Ben et al., 2014). This conception was initially reported in
2014 and has attracted increasing attention (Ben et al., 2014). Recent
research based on animal models and genetic analysis has uncovered
certain disease-causing or disease-promoting genes. To date, 23
MMAF-associated genes have been identified, including AK7 (MIM:
615364), ARMC2 (MIM:618424), CEP135 (MIM: 611423),CFAP43 (MIM: 617558), CFAP44 (MIM: 617559), CFAP47(MIM: 301057), CFAP58 (MIM: 619129), CFAP65 (MIM: 614270),CFAP69 (MIM: 617949), CFAP70 (MIM: 618661), CFAP91(MIM: 609910), CFAP251 (MIM: 618146), DNAH1 (MIM: 603332),DNAH2 (MIM: 603333), DNAH6 (MIM: 603336), DNAH8(MIM: 603337), DNAH17 (MIM: 610063), DZIP1 (MIM: 608671),FSIP2 (MIM: 618153), QRICH2 (MIM: 618304), SPEF2(MIM: 610172), TTC21A (MIM: 611430), and TTC29 (MIM:
618735) (Jiao et al., 2021; Toure´ et al., 2020). However, mutations in
each gene are possibly responsible for only a small fraction of
pathogenic factors, and a mass of cases could not be explained.
Therefore, a more comprehensive investigation of the pathology and
molecular mechanisms of MMAF is needed to further boost diagnosis
efficacy.
The cilia and flagella-associated protein (CFAP) protein family is
associated with the development and function of sperm flagellum (Tang et
al., 2017). This family plays an important role in the generation,
assembly, and maintenance of motor functions of cilia and flagella. To
date, multiple CFAP gene deficiencies have been reported to be
associated with MMAF, such as several mutations in CFAP43, CFAP44,
CFAP58, CFAP65, CFAP69, CFAP70, and CFAP251 (Tang et al., 2017;
Coutton et al., 2018; Li et al., 2020; He et al., 2020; He et al., 2019;
Beurois et al., 2019; Auguste et al., 2018). To date, only one report
revealed that cilia and flagella-associated protein 47 (CFAP47,NG_016381.2) leads to MMAF in an X-chromosome-linked inheritance
pattern (Liu et al., 2021). Males with hemizygous CFAP47 variants
exhibit a typical MMAF phenotype, and the ultrastructure shows an
abnormal axoneme, including disorganized outer dense fibers (ODF), and
peripheral microtubule doublets (DMTs), as well as central pair of
microtubules (CPs), are missing (Liu et al., 2021).CFAP47 -mutated male mice are sterile, with decreased sperm
motility and abnormal flagella morphology (Liu et al., 2021). Hence,
future studies should evaluate CFAP47 in larger cohorts to
corroborate the relationship between genotype and phenotype.
Herein, we report two MMAF patients who carried a novel hemizygous
mutation c.1414G>A [p.V472M] in CFAP47 .
Bioinformatics analysis and functional studies in vitro validated the
pathogenicity of the mutation. Furthermore, we first revealed thatCFAP47 mutations are also related to malformed sperm heads and
annulus, as well as suggested the potential mechanism by whichCFAP47 regulates spermatogenesis. Our work provides strong
evidence to confirm the causative relationship between CFAP47variants and MMAF.