Teratozoospermia: spotlight on the main genetic actors in the human

Deficiency of MFSD6L, an acrosome membrane protein, causes oligoasthenoteratozoospermia in humans and mice

Oligoasthenoteratozoospermia is an important factor affecting male fertility and has been found to be associated with genetic factors. However, there are still a proportion of oligoasthenoteratozoospermia cases that cannot be explained by known pathogenic genetic variants. Here, we perform genetic analyses and identify bi-allelic loss-of-function variants of MFSD6L from an oligoasthenoteratozoospermia-affected family. Mfsd6l knock-out male mice also present male subfertility with reduced sperm concentration, motility, and deformed acrosomes. Further mechanistic analyses reveal that MFSD6L, as an acrosome membrane protein, plays an important role in the formation of acrosome by interacting with the inner acrosomal membrane protein SPACA1. Moreover, poor embryonic development is consistently observed after intracytoplasmic sperm injection treatment using spermatozoa from the MFSD6L-deficient man and male mice. Collectively, our findings reveal that MFSD6L is required for the anchoring of sperm acrosome and head shaping. The deficiency of MFSD6L affects male fertility and causes oligoasthenoteratozoospermia in humans and mice.

Utility of exome sequencing in primary spermatogenic disorders: From research to diagnostics

BACKGROUND

Primary spermatogenic disorders represent a severe form of male infertility whereby sperm production is impaired due to testicular dysfunction, leading to reduced quality or quantity of spermatozoa. Gene-centered research has certainly demonstrated the importance of the genetic factor in the etiology of both poor sperm morphology or motility and reduced sperm count. In the last decade, next-generation sequencing has expanded the research to whole exome which has transformed our understanding of male infertility genetics, but uncertainty persists in its diagnostic yield, especially in large unrelated populations.

OBJECTIVE

To evaluate the utility of exome sequencing in detecting genetic factors contributing to various traits of primary spermatogenic disorders, which is a crucial step before interpreting the diagnostic yield of the platform.

MATERIALS AND METHODS

We manually curated 415 manuscripts and included 19 research studies that predominantly performed whole exome sequencing in cohorts of unrelated cases with primary spermatogenic defects.

RESULTS

The detection rate, defined as the fraction of cases with an identifiable genetic cause, typically remained below 25% for quantitative defects of spermatozoa, whereas improved rates were observed for traits of abnormal sperm morphology/motility and in populations enriched with consanguineous families. Unlike the quantitative defects, the genetic architecture of the qualitative issues of spermatozoa featured a small number of recurrent genes describing a large fraction of studied cases. These observations were also in line with the lower biological complexity of the pathways affected by the reported genes.

DISCUSSION AND CONCLUSIONS

This review demonstrates the variability in detection rates of exome sequencing across semen phenotypes, which may have an impact on the expectations of the diagnostic yield in the clinical setting.

A novel homozygous mutation of CFAP300 identified in a Chinese patient with primary ciliary dyskinesia and infertility

Primary ciliary dyskinesia (PCD) is a clinically rare, genetically and phenotypically heterogeneous condition characterized by chronic respiratory tract infections, male infertility, tympanitis, and laterality abnormalities. PCD is typically resulted from variants in genes encoding assembly or structural proteins that are indispensable for the movement of motile cilia. Here, we identified a novel nonsense mutation, c.466G>T, in cilia- and flagella-associated protein 300 (CFAP300) resulting in a stop codon (p.Glu156 *) through whole-exome sequencing (WES). The proband had a PCD phenotype with laterality defects and immotile sperm flagella displaying a combined loss of the inner dynein arm (IDA) and outer dynein arm (ODA). Bioinformatic programs predicted that the mutation is deleterious. Successful pregnancy was achieved through intracytoplasmic sperm injection (ICSI). Our results expand the spectrum of CFAP300 variants in PCD and provide reproductive guidance for infertile couples suffering from PCD caused by them.

A novel homozygous splicing mutation in AK7 causes multiple morphological abnormalities of sperm flagella in patients from consanguineous Pakistani families

Multiple morphological abnormalities of the flagella (MMAF) represent a severe form of sperm defects leading to asthenozoospermia and male infertility. In this study, we identified a novel homozygous splicing mutation (c.871-4 ACA>A) in the adenylate kinase 7 (AK7) gene by whole-exome sequencing in infertile individuals. Spermatozoa from affected individuals exhibited typical MMAF characteristics, including coiled, bent, short, absent, and irregular flagella. Transmission electron microscopy analysis showed disorganized axonemal structure and abnormal mitochondrial sheets in sperm flagella. Immunofluorescence staining confirmed the absence of AK7 protein from the patients' spermatozoa, validating the pathogenic nature of the mutation. This study provides direct evidence linking the AK7 gene to MMAF-associated asthenozoospermia in humans, expanding the mutational spectrum of AK7 and enhancing our understanding of the genetic basis of male infertility.

Novel variations in TENT5D lead to teratozoospermia in infertile patients

PURPOSE

Teratozoospermia is the main pathogenic factor of male infertility. However, the genetic etiology of teratozoospermia is largely unknown. This study aims to clarify the relationship between novel variations in TENT5D and teratozoospermia in infertile patients.

MATERIALS AND METHODS

Two infertile patients were enrolled. Routine semen analysis of patients and normal controls was conducted with the WHO guidelines. Whole-exome sequencing (WES) was conducted to identify pathogenic variants in the two patients. Morphology and ultrastructure analysis of spermatozoa in the two patients was determined by Papanicolaou staining, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The functional effect of the identified variants was analyzed by immunofluorescence staining and western blotting. The expression of TENT5D in different germ cells was detected by immunofluorescence staining.

RESULTS

Two new hemizygous variations, c.101C > T (p.P34L) and c.125A > T (p.D42V), in TENT5D were detected in two patients with male infertility. Morphology analysis showed abnormalities in spermatozoa morphology in the two patients, including multiple heads, headless, multiple tails, coiled, and/or bent flagella. Ultrastructure analysis showed that most of the spermatozoa exhibited missing or irregularly arranged '9+2' structures. Further functional experiments confirmed the abrogated TENT5D protein expression in patients. In addition, both p.P34L and p.D42V substitutions resulted in a conformational change of the TENT5D protein. We precisely analyzed the subcellular localization of TENT5D in germ cells in humans and mice. And we found that TENT5D was predominantly detected in the head and flagellum of elongating spermatids and epididymal spermatozoa.

CONCLUSIONS

Our results showed further evidence of a relationship between TENT5D mutation and human male infertility, providing new genetic insight for use in the diagnosis and treatment of male infertility.

The landscape of RNA-binding proteins in mammalian spermatogenesis

Despite continuous expansion of the RNA-binding protein (RBP) world, there is a lack of systematic understanding of RBPs in mammalian testis, which harbors one of the most complex tissue transcriptomes. We adapted RNA interactome capture to mouse male germ cells, building an RBP atlas characterized by multiple layers of dynamics along spermatogenesis. Trapping of RNA-crosslinked peptides showed that the glutamic acid-arginine (ER) patch, a residue-coevolved polyampholytic element present in coiled-coils, enhances RNA binding of its host RBPs. Deletion of this element in NONO (non-POU domain-containing octamer-binding protein) led to a defective mitosis-to-meiosis transition due to compromised NONO-RNA interactions. Whole-exome sequencing of over 1000 infertile men revealed a prominent role of RBPs in the human genetic architecture of male infertility and identified risk ER patch variants.

Arsenic exposure causes decline in sperm motility accompanied by energy metabolism disorders in mouse testes

Arsenic (As) is a notorious environmental toxicant widely present in various natural environments. As exposure has been correlated with the decline in sperm motility. Yet, the mechanism has not been fully elucidated. Adult male C57 mice were given 0, 1, or 15 mg/L NaAsO2 for 10 weeks. The mature seminiferous tubules and sperm count were decreased in As-exposed mice. Sperm motility and several sperm motility parameters, including average path velocity (VAP), straight-line velocity (VSL), curvilinear velocity (VCL), beat-cross frequency (BCF), linearity (LIN), straightness (STR), and amplitude of lateral head displacement (ALH), were declined in As-exposed mice. RNA sequencing and transcriptomics analyses revealed that differentially expressed genes (DEGs) were mainly enriched in metabolic pathways. Untargeted metabolomics analyses indicated that energy metabolism was disrupted in As-exposed mouse testes. Gene set enrichment analysis showed that glycolysis and oxidative phosphorylation were disturbed in As-exposed mouse testes. As-induced disruption of testicular glucose metabolism and oxidative phosphorylation was further validated by RT-PCR and Western blotting. In conclusion, As exposure causes decline in sperm motility accompanied by energy metabolism disorders in mouse testes.

Bi-allelic variants in chromatoid body protein TDRD6 cause spermiogenesis defects and severe oligoasthenoteratozoospermia in humans

BACKGROUND

The association between the TDRD6 variants and human infertility remains unclear, as only one homozygous missense variant of TDRD6 was found to be associated with oligoasthenoteratozoospermia (OAT).

METHODS

Whole-exome sequencing and Sanger sequencing were employed to identify potential pathogenic variants of TDRD6 in infertile men. Histology, immunofluorescence, immunoblotting and ultrastructural analyses were conducted to clarify the structural and functional abnormalities of sperm in mutated patients. Tdrd6-knockout mice were generated using the CRISPR-Cas9 system. Total RNA-seq and single-cell RNA-seq (scRNA-seq) analyses were used to elucidate the underlying molecular mechanisms, followed by validation through quantitative RT-PCR and immunostaining. Intracytoplasmic sperm injection (ICSI) was also used to assess the efficacy of clinical treatment.

RESULTS

Bi-allelic TDRD6 variants were identified in five unrelated Chinese individuals with OAT, including homozygous loss-of-function variants in two consanguineous families. Notably, besides reduced concentrations and impaired motility, a significant occurrence of acrosomal hypoplasia was detected in multiple spermatozoa among five patients. Using the Tdrd6-deficient mice, we further elucidate the pivotal role of TDRD6 in spermiogenesis and acrosome identified. In addition, the mislocalisation of crucial chromatoid body components DDX4 (MVH) and UPF1 was also observed in round spermatids from patients harbouring TDRD6 variants. ScRNA-seq analysis of germ cells from a patient with TDRD6 variants revealed that TDRD6 regulates mRNA metabolism processes involved in spermatid differentiation and cytoplasmic translation.

CONCLUSION

Our findings strongly suggest that TDRD6 plays a conserved role in spermiogenesis and confirms the causal relationship between TDRD6 variants and human OAT. Additionally, this study highlights the unfavourable ICSI outcomes in individuals with bi-allelic TDRD6 variants, providing insights for potential clinical treatment strategies.

Gene-deficient mouse model established by CRISPR/Cas9 system reveals 15 reproductive organ-enriched genes dispensable for male fertility

Since the advent of gene-targeting technology in embryonic stem cells, mice have become a primary model organism for investigating human gene function due to the striking genomic similarities between the two species. With the introduction of the CRISPR/Cas9 system for genome editing in mice, the pace of loss-of-function analysis has accelerated significantly. This has led to the identification of numerous genes that play crucial roles in male reproductive processes, including meiosis, chromatin condensation, flagellum formation in the testis, sperm maturation in the epididymis, and fertilization in the oviduct. Despite the advancements, the functions of many genes, particularly those enriched in male reproductive tissues, remain largely unknown. In our study, we focused on 15 genes and generated 13 gene-deficient mice [4933411K16Rik, Adam triple (Adam20, Adam25, and Adam39), BC048671, Cfap68, Gm4846, Gm4984, Gm13570, Nt5c1b, Ppp1r42, Saxo4, Sh3d21, Spz1, and Tektl1] to elucidate their roles in male fertility. Surprisingly, all 13 gene-deficient mice exhibited normal fertility in natural breeding experiments, indicating that these genes are not essential for male fertility. These findings have important implications as they may help prevent other research laboratories from duplicating efforts to generate knockout mice for genes that do not demonstrate an apparent phenotype related to male fertility. By shedding light on the dispensability of these genes, our study contributes to a more efficient allocation of research resources in the exploration of male reproductive biology.

The lack of Tex44 causes severe subfertility with flagellar abnormalities in male mice

By analyzing a mouse Interspecific Recombinant Congenic Strain (IRCS), we previously identified a quantitative trait locus (QTL), called Mafq1 on mouse chromosome 1, that is associated with male hypofertility and ultrastructural sperm abnormalities. Within this locus, we identified a new candidate gene that could be implicated in a reproductive phenotype: Tex44 (Testis-expressed protein 44). We thus performed a CRISPR/Cas9-mediated complete deletion of this gene in mice in order to study its function. Tex44-KO males were severely hypofertile in vivo and in vitro due to a drastic reduction of sperm motility which itself resulted from important morphological sperm abnormalities. Namely, Tex44-KO sperm showed a disorganized junction between the midpiece and the principal piece of the flagellum, leading to a 180° flagellar bending in this region. In addition, the loss of some axonemal microtubule doublets and outer dense fibers in the flagellum's principal piece has been observed. Our results suggest that, in mice, TEX44 is implicated in the correct set-up of the sperm flagellum during spermiogenesis and its absence leads to flagellar abnormalities and consequently to severe male hypofertility.

Genetic Causes of Qualitative Sperm Defects: A Narrative Review of Clinical Evidence

Several genes are implicated in spermatogenesis and fertility regulation, and these genes are presently being analysed in clinical practice due to their involvement in male factor infertility (MFI). However, there are still few genetic analyses that are currently recommended for use in clinical practice. In this manuscript, we reviewed the genetic causes of qualitative sperm defects. We distinguished between alterations causing reduced sperm motility (asthenozoospermia) and alterations causing changes in the typical morphology of sperm (teratozoospermia). In detail, the genetic causes of reduced sperm motility may be found in the alteration of genes associated with sperm mitochondrial DNA, mitochondrial proteins, ion transport and channels, and flagellar proteins. On the other hand, the genetic causes of changes in typical sperm morphology are related to conditions with a strong genetic basis, such as macrozoospermia, globozoospermia, and acephalic spermatozoa syndrome. We tried to distinguish alterations approved for routine clinical application from those still unsupported by adequate clinical studies. The most important aspect of the study was related to the correct identification of subjects to be tested and the correct application of genetic tests based on clear clinical data. The correct application of available genetic tests in a scenario where reduced sperm motility and changes in sperm morphology have been observed enables the delivery of a defined diagnosis and plays an important role in clinical decision-making. Finally, clarifying the genetic causes of MFI might, in future, contribute to reducing the proportion of so-called idiopathic MFI, which might indeed be defined as a subtype of MFI whose cause has not yet been revealed.

Identification of novel homozygous asthenoteratospermia-causing ARMC2 mutations associated with multiple morphological abnormalities of the sperm flagella

PURPOSE

To identify the genetic causes of multiple morphological abnormalities in sperm flagella (MMAF) and male infertility in patients from two unrelated Han Chinese families.

METHODS

Whole-exome sequencing was conducted using blood samples from the two individuals with MMAF and male infertility. Hematoxylin and eosin staining and scanning electron microscopy were performed to evaluate sperm morphology. Ultrastructural and immunostaining analyses of the spermatozoa were performed. The HEK293T cells were used to confirm the pathogenicity of the variants.

RESULTS

We identified two novel homozygous missense ARMC2 variants: c.314C > T: p.P105L and c.2227A > G: p.N743D. Both variants are absent or rare in the human population genome data and are predicted to be deleterious. In vitro experiments indicated that both ARMC2 variants caused a slightly increased protein expression. ARMC2-mutant spermatozoa showed multiple morphological abnormalities (bent, short, coiled, absent, and irregular) in the flagella. In addition, the spermatozoa of the patients revealed a frequent absence of the central pair complex and disrupted axonemal ultrastructure.

CONCLUSION

We identified two novel ARMC2 variants that caused male infertility and MMAF in Han Chinese patients. These findings expand the mutational spectrum of ARMC2 and provide insights into the complex causes and pathogenesis of MMAF.

A novel homozygous nonsense variant of AK7 is associated with multiple morphological abnormalities of the sperm flagella

RESEARCH QUESTION

Is the novel homozygous nonsense variant of AK7 associated with multiple morphological abnormalities of the sperm flagella (MMAF), a specific type of oligoasthenoteratozoospermia leading to male infertility?

DESIGN

Whole-exome sequencing and Sanger sequencing were performed to identify potential gene variants. Immunoblotting and immunofluorescence were applied to confirm the relationship between mutated genes and disease phenotypes. The concentration of reactive oxygen species and the rate of apoptosis were measured to evaluate the mitochondrial function of spermatozoa. Transmission electron microscopy and scanning electron microscopy were employed to observe sperm ultrastructure.

RESULTS

A novel homozygous nonsense variant of AK7, c.1153A>T (p. Lys385*), was identified in two infertile siblings with asthenoteratozoospermia through whole-exome sequencing. Both immunoblotting and immunofluorescence assays showed practically complete absence of AK7 in the patient's spermatozoa. Additionally, the individual with the novel AK7 variant exhibited a phenotype characterized by severe oxidative stress and apoptosis caused by mitochondrial metabolic dysfunction of spermatozoa. Notably, remarkable flagellar defects with multiple axonemes in uniflagellate spermatozoa, accompanied by mitochondrial vacuolization, were observed; this has not been reported previously in patients with other AK7 variants.

CONCLUSIONS

This study found that a novel identified homozygous nonsense variant of AK7 may be associated with MMAF-related asthenoteratozoospermia. The observed functional associations between mitochondria and sperm flagellar assembly provide evidence for potential mutual regulation between AK7 and flagella-associated proteins during spermatogenesis.

Decreased embryo developmental potential and lower cumulative pregnancy rate in men with multiple morphological abnormalities of the sperm flagella

Objective

Multiple morphological abnormalities of the sperm flagella (MMAF) is characterized by abnormal flagellar phenotypes, which is a particular kind of asthenoteratozoospermia. Previous studies have reported a comparable intracytoplasmic sperm injection (ICSI) outcome in terms of fertilization rate and clinical pregnancy rate in patients with MMAF compared with those with no MMAF; however, others have conflicting opinions. Assisted reproductive technology (ART) outcomes in individuals with MMAF are still controversial and open to debate.

Methods

A total of 38 patients with MMAF treated at an academic reproductive center between January 2014 and July 2022 were evaluated in the current retrospective cohort study and followed up until January 2023. Propensity score matching was used to adjust for the baseline clinical characteristics of the patients and to create a comparable control group. The genetic pathogenesis of MMAF was confirmed by whole exome sequencing. The main outcomes were the embryo developmental potential, the cumulative pregnancy rate (CLPR), and the cumulative live birth rate (CLBR).

Results

Pathogenic variants in known genes of DNAH1, DNAH11, CFAP43, FSIP2, and SPEF2 were identified in patients with MMAF. Laboratory outcomes, including the fertilization rate, 2PN cleavage rate, blastocyst formation rate, and available blastocyst rate, followed a trend of decline in the MMAF group (p < 0.05). Moreover, according to the embryo transfer times and complete cycles, the CLPR in the cohort of MMAF was lower compared with the oligoasthenospermia pool (p = 0.033 and p = 0.020, respectively), while no statistical differences were observed in the neonatal outcomes.

Conclusion

The current study presented decreased embryo developmental potential and compromised clinical outcomes in the MMAF cohort. These findings may provide clinicians with evidence to support genetic counseling and clinical guidance in specific patients with MMAF.

AKAP3-mediated type I PKA signaling is required for mouse sperm hyperactivation and fertility†

The protein kinase A (PKA) signaling pathway, which mediates protein phosphorylation, is important for sperm motility and male fertility. This process relies on A-kinase anchoring proteins that organize PKA and its signalosomes within specific subcellular compartments. Previously, it was found that the absence of A-kinase anchoring protein 3 (AKAP3) leads to multiple morphological abnormalities in mouse sperm. But how AKAP3 regulates sperm motility is yet to be elucidated. AKAP3 has two amphipathic domains, here named dual and RI, in its N-terminus. These domains are responsible for binding regulatory subunits I alpha (RIα) and II alpha (RIIα) of PKA and for RIα only, respectively. Here, we generated mutant mice lacking the dual and RI domains of AKAP3. It was found that the deletion of these domains caused male mouse infertile, accompanied by mild defects in the fibrous sheath of sperm tails. Additionally, the levels of serine/threonine phosphorylation of PKA substrates and tyrosine phosphorylation decreased in the mutant sperm, which exhibited a defect in hyperactivation under capacitation conditions. The protein levels of PKA subunits remained unchanged. But, interestingly, the regulatory subunit RIα was mis-localized from principal piece to midpiece of sperm tail, whereas this was not observed for RIIα. Further protein-protein interaction assays revealed a preference for AKAP3 to bind RIα over RIIα. Collectively, our findings suggest that AKAP3 is important for sperm hyperactivity by regulating type-I PKA signaling pathway mediated protein phosphorylation via its dual and RI domains.

CCDC28A deficiency causes sperm head defects, reduced sperm motility and male infertility in mice

Mature spermatozoa with normal morphology and motility are essential for male reproduction. The epididymis has an important role in the proper maturation and function of spermatozoa for fertilization. However, factors related to the processes involved in spermatozoa modifications are still unclear. Here we demonstrated that CCDC28A, a member of the CCDC family proteins, is highly expressed in testes and the CCDC28A deletion leads to male infertility. We found CCDC28A deletion had a mild effect on spermatogenesis. And epididymal sperm collected from Ccdc28a-/- mice showed bent sperm heads, acrosomal defects, reduced motility and decreased in vitro fertilization competence whereas their axoneme, outer dense fibers, and fibrous sheath were all normal. Furthermore, we found that CCDC28A interacted with sperm acrosome membrane-associated protein 1 (SPACA1) and glycogen synthase kinase 3a (GSK3A), and deficiencies in both proteins in mice led to bent heads and abnormal acrosomes, respectively. Altogether, our results reveal the essential role of CCDC28A in regulating sperm morphology and motility and suggesting a potential marker for male infertility.

Decabromodiphenyl ether induces the chromosome association disorders of spermatocytes and deformation failures of spermatids in mice

The environmental presence of decabromodiphenyl ether (BDE-209), which is toxic to the male reproductive system, is widespread. The current study investigated its mechanism of toxicity in mice. The results showed, that BDE-209 induced DNA damage, decreased the expression of the promoter of meiosis spermatogenesis- and oogenesis-specific basic helix-loop-helix 1 (Sohlh1), meiosis related-factors Lethal (3) malignant brain tumor like 2 (L3MBTL2), PIWI-like protein 2 (MILI), Cyclin-dependent kinase 2 (CDK2), Cyclin A, synaptonemal complex protein 1 (SYCP1) and synaptonemal complex protein 3 (SYCP3), and caused spermatogenic cell apoptosis, resulting in a decrease in sperm quantity and quality. Furthermore, BDE-209 downregulated the levels of anaphase-promoting complex/cyclosome (APC/C), increased the expression of PIWI-like protein 1 (MIWI) in the cytoplasm of elongating spermatids, and decreased the nuclear levels of RING finger protein 8 (RNF8), ubiquitinated (ub)-H2A/ub-H2B, and Protamine 1 (PRM1)/Protamine 2 (PRM2), while increasing H2A/H2B nuclear levels in spermatids. The reproductive toxicity was persistent for 50 days following the withdrawal of BDE-209 exposure. The results suggested that BDE-209 inhibits the initiation of meiosis by decreasing the expression of Sohlh1. Furthermore, the reduced expression of L3MBTL2 inhibited the formation of chromosomal synaptonemal complexes by depressing the expression of meiosis regulators affecting the meiotic progression and also inhibited histone ubiquitination preventing the replacement of histones by protamines, by preventing RNF8 from entering nuclei, which affected the evolution of spermatids into mature sperm.

Coiled-coil domain-containing 38 is required for acrosome biogenesis and fibrous sheath assembly in mice

During spermiogenesis, haploid spermatids undergo dramatic morphological changes to form slender sperm flagella and cap-like acrosomes, which are required for successful fertilization. Severe deformities in flagella cause a male infertility syndrome, multiple morphological abnormalities of the flagella (MMAF), while acrosomal hypoplasia in some cases leads to sub-optimal embryonic developmental potential. However, evidence regarding the occurrence of acrosomal hypoplasia in MMAF is limited. Here, we report the generation of base-edited mice knocked out for coiled-coil domain-containing 38 (Ccdc38) via inducing a nonsense mutation and find that the males are infertile. The Ccdc38-KO sperm display acrosomal hypoplasia and typical MMAF phenotypes. We find that the acrosomal membrane is loosely anchored to the nucleus and fibrous sheaths are disorganized in Ccdc38-KO sperm. Further analyses reveal that Ccdc38 knockout causes a decreased level of TEKT3, a protein associated with acrosome biogenesis, in testes and an aberrant distribution of TEKT3 in sperm. We finally show that intracytoplasmic sperm injection overcomes Ccdc38-related infertility. Our study thus reveals a previously unknown role for CCDC38 in acrosome biogenesis and provides additional evidence for the occurrence of acrosomal hypoplasia in MMAF.

Whole-exome sequencing identifies ADGB as a novel causative gene for male infertility in humans: from motility to fertilization

OBJECTIVES

In male mice, adgb-knockout has been reported to cause male infertility with spermatogenesis defects involving flagella and acrosome. However, this remains unclear for humans.

MATERIALS AND METHODS

Sequencing studies were conducted in a research hospital on samples from three unrelated infertile men with severe asthenoteratozoospermia from Han Chinese families. Data were collected through rigorous in silico analysis. Sanger sequencing were performed to identify pathogenic mutations. Sperm cells from patients were characterized using electron microscopy and used to verify the pathogenicity of the genetic factors through functional assays. Intracytoplasmic sperm injections (ICSI) assays were performed in ADGB-affected males.

MAIN RESULTS

Herein, in a cohort of 105 Han Chinese men with idiopathic asthenoteratozoospermia, we reported the identification of bi-allelic deleterious variants of ADGB in three infertile men from unrelated families using whole-exome sequencing. We found one homozygous frameshift ADGB variant (NM_024694.4: c.2801_2802del:p.K934Rfs*33), one homozygous missense ADGB variant (NM_024694.4: c.C3167T:p.T1056I), and one compound heterozygous ADGB variant (NM_024694.4: c.C3167T:p.T1056I; c.C3197T:p.A1066V). These variants were rare in general population and were predicted to be damaging by multiple bioinformatics tools. Further, the spermatozoa from patients harboring ADGB variants showed multiple acrosome and flagellum malformations under light and electron microscopy. Functional assays revealed the structural defects associated with dysregulation of ADGB and multiple spermatogenesis proteins. Notably, the fertilization success via ICSI treatment in all three patients, as well as the normal expression of PLCζ but CaM deficiency in the spermatozoa, suggesting that ICSI other than in vitro fertilization (IVF) is an optimal treatment for ADGB-deficient patients.

DISCUSSION AND CONCLUSION

Our findings provide new information for the molecular diagnosis of asthenoteratozoospermia and valuable reference for personalized genetic counselling and clinical treatment for these patients. The underlying risk of IVF failure behind sperm defects was highlighted.

Adverse outcome pathways of PBDEs inducing male reproductive toxicity

Polybrominated diphenyl ethers (PBDEs) are widely used brominated flame retardants, they are easily released into environment and causing adverse effects to the ecosystem and human health. This review aims to summarize the research status of PBDEs-induced male reproductive toxicity and its mechanisms at various levels such as molecular/cellular, tissue/organ and individual/population. The Adverse Outcome Pathways (AOPs) diagram showed that PBDEs-induced reactive oxygen species (ROS) production, disruptions of estrogen receptor-α (ERα) and antagonism of androgen receptor (AR) were defined as critical molecular initiating events (MIEs). They caused key events (KEs) at the molecular and cellular levels, including oxidative stress, increased DNA damage, damaging mitochondria, increased glycolipid levels and apoptosis, depletion of ectoplasmic specialization and decreased Leydig cells numbers. These in turn lead to followed KEs at the tissue or organ levels, such as the impaired spermatogenesis, impaired blood-testis barrier and reduced testosterone synthesis and function. As a result, reproductive system-related adverse outcomes (AOs) were reported, such as the decreased sperm quantity or quality, shorten male anogenital distance and cryptorchidism in individual and reduced reproduction of the population. This review assembled information on the mechanisms of male reproductive toxicity induced by PBDEs, and constructed a causal mechanism relationship diagram from different levels using the an AOP framework to provide theoretical basis for ecological risk assessment and environmental management of PBDEs. The AOP framework makes it possible to develop risk management strategies based on toxicity mechanisms and support for development of Integrated Approach to Testing and Assessment (IATA) which are available for regulatory purposes.

Novel variants in DNAH6 cause male infertility associated with multiple morphological abnormalities of the sperm flagella (MMAF) and ICSI outcomes

Variations in the dynein axonemal heavy chain gene, dynein axonemal heavy chain 6 ( DNAH6 ), lead to multiple morphological abnormalities of the flagella. Recent studies have reported that these deficiencies may result in sperm head deformation. However, whether DNAH6 is also involved in human acrosome biogenesis remains unknown. The purpose of this study was to investigate DNAH6 gene variants and their potential functions in the formation of defective sperm heads and flagella. Whole-exome sequencing was performed on a cohort of 375 patients with asthenoteratozoospermia from the First Affiliated Hospital of Anhui Medical University (Hefei, China). Hematoxylin and eosin staining, scanning electron microscopy, and transmission electron microscopy were performed to analyze the sperm morphology and ultrastructure. Immunofluorescence staining and Western blot analysis were conducted to examine the effects of genetic variants. We identified three novel deleterious variants in DNAH6 among three unrelated families. The absence of inner dynein arms and radial spokes was observed in the sperm of patients with DNAH6 variants. Additionally, deficiencies in the acrosome, abnormal chromatin compaction, and vacuole-containing sperm heads were observed in these patients with DNAH6 variants. The decreased levels of the component proteins in these defective structures were further confirmed in sperm from patients with DNAH6 variants using Western blot. After intracytoplasmic sperm injection (ICSI) treatment, the partner of one patient with a DNAH6 variant achieved successful pregnancy. Overall, novel variants in DNAH6 genes that contribute to defects in the sperm head and flagella were identified, and the findings indicated ICSI as an effective clinical treatment for such patients.

A novel NPHP4 homozygous missense variant identified in infertile brothers with multiple morphological abnormalities of the sperm flagella

PURPOSE

Asthenozoospermia is an important cause of male infertility, and the most serious type is characterized by multiple morphological abnormalities of the sperm flagella (MMAF). However, the precise etiology of MMAF remains unknown. In the current study, we recruited a consanguineous Pakistani family with two infertile brothers suffering from primary infertility due to MMAF without obvious signs of PCD.

METHODS

We performed whole-exome sequencing on DNAs of the patients, their parents, and a fertile brother and identified the homozygous missense variant (c.1490C > G (p.P497R) in NPHP4 as the candidate mutation for male infertility in this family.

RESULTS

Sanger sequencing confirmed that this mutation recessively co-segregated with the MMAF in this family. In silico analysis revealed that the mutation site is conserved across different species, and the identified mutation also causes abnormalities in the structure and hydrophobic interactions of the NPHP4 protein. Different bioinformatics tools predict that NPHP4p.P497R mutation is pathogenic. Furthermore, Papanicolaou staining and scanning electron microscopy of sperm revealed that affected individuals displayed typical MMAF phenotype with a high percentage of coiled, bent, short, absent, and/or irregular flagella. Transmission electron microscopy images of the patient's spermatozoa revealed significant anomalies in the sperm flagella with the absence of a central pair of microtubules (9 + 0) in every section scored.

CONCLUSIONS

Taken together, these results show that the homozygous missense mutation in NPHP4 is associated with MMAF.

Application of Intracytoplasmic Morphologically Selected Sperm Injection (IMSI) on a Teratozoospermic Patient and Its Effect on the In-Vitro Fertilization (IVF) Outcome

Infertility, defined as the inability to conceive after 12 months of unprotected sexual activity, affects millions globally. Approximately 80% of cases have identifiable causes, including endometriosis, tubal obstruction, ovulatory dysfunction, and male sperm abnormalities. Lifestyle factors, such as smoking and obesity, also impact fertility. Sperm morphology, a key factor in male infertility, often presents as teratozoospermia, with defects in the head, midpiece, or tail. Poor ovarian reserve, indicated by low anti-mullerine hormone (AMH) and antra-follicular count (AFC) values, contributes to female infertility, often exacerbated by age-related factors. Elevated follicle-stimulating hormone (FSH) levels further diminish oocyte quantity and quality. Intracytoplasmic Sperm Injection (ICSI), a micromanipulation technique aiding infertile couples, may face challenges in detecting subtle sperm morphology defects. Advanced methods like Motile Sperm Organelle Morphological Examination (MSOME) and Intracytoplasmic Morphologically Selected Sperm Injection (IMSI) under high magnification enhance sperm selection accuracy. We present the case of a 36-year-old woman and her 42-year-old husband who sought assistance after seven years of infertility. Previous Intrauterine injection (IUI) and ICSI attempts failed due to the wife's low ovarian reserve and elevated FSH, compounded by the husband's teratozoospermia. Their earlier In-Vitro Fertilization (IVF) experience yielded a single poor-quality oocyte, hindering blastocyst formation. Investigations revealed the wife's poor AFC, AMH of 0.033ng/ml, and FSH at 24IU/L. Her medical history included hypertension and gallbladder removal. The husband exhibited 98% defective sperm, devoid of a substance abuse history. The wife's family had a polycystic ovarian syndrome (PCOS) history, and her low AMH and AFC yielded only three poor-quality oocytes during the current assessment. Oocytes were retrieved, and sperm were selected with the help of IMSI. After ICSI, the patient successfully conceived.

Deleterious genetic changes in AGTPBP1 result in teratozoospermia with sperm head and flagella defects

Approximately 10%-15% of couples worldwide are infertile, and male factors account for approximately half of these cases. Teratozoospermia is a major cause of male infertility. Although various mutations have been identified in teratozoospermia, these can vary among ethnic groups. In this study, we performed whole-exome sequencing to identify genetic changes potentially causative of teratozoospermia. Out of seven genes identified, one, ATP/GTP Binding Protein 1 (AGTPBP1), was characterized, and three missense changes were identified in two patients (Affected A: p.Glu423Asp and p.Pro631Leu; Affected B: p.Arg811His). In those two cases, severe sperm head and tail defects were observed. Moreover, AGTPBP1 localization showed a fragmented pattern compared to control participants, with specific localization in the neck and annulus regions. Using murine models, we found that AGTPBP1 is localized in the manchette structure, which is essential for sperm structure formation. Additionally, in Agtpbp1-null mice, we observed sperm head and tail defects similar to those in sperm from AGTPBP1-mutated cases, along with abnormal polyglutamylation tubulin and decreasing △-2 tubulin levels. In this study, we established a link between genetic changes in AGTPBP1 and human teratozoospermia for the first time and identified the role of AGTPBP1 in deglutamination, which is crucial for sperm formation.

LRRC23 deficiency causes male infertility with idiopathic asthenozoospermia by disrupting the assembly of radial spokes

Asthenozoospermia (AZS) is the primary cause of infertility in males. The radial spoke (RS) is an axonemal structure, connecting the peripheral doublet microtubules with the central pair of microtubules. This T-shaped multiprotein complex functions as a mechanochemical sensor to promote sperm motility. LRRC23 is a novel subunit of the RS complex that is necessary for flagellar assembly and movement in mice. However, the importance of LRRC23 in modulating RS formation in humans remains unclear. Here, we identified a homozygous nonsense mutation in LRRC23 (c.376C>T:p. Arg126X) in an infertile AZS patient whose parents were consanguineous. We verified the adversity of this novel mutation because of its ability to disrupt LRRC23 synthesis and impair RSs integrity. Furthermore, we demonstrated an interaction between LRRC23 and RSPH3 in vitro, indicating that LCCR23 is associated with RS in humans. Meanwhile, the LRRC23-mutant patient had a good prognosis following intracytoplasmic sperm injection. This study provides strong preliminary evidence that LRRC23 defects are potential causative factors of AZS in humans, which expands our knowledge for improved genetic counseling and better reproductive recommendations for patients with AZS.

FAM71D is dispensable for spermatogenesis and male fertility in mice

In mammals, the generation of sperm cells capable of fertilization is a highly complex process including spermatogenesis in the testis and maturation in the epididymis. In our previous study, we have demonstrated that FAM71D (Family with sequence similarity 71, member D), which could interact with calmodulin, was highly expressed in human and mouse testis. To investigate the physiological role of FAM71D in spermatogenesis, we next generate Fam71d loss-of-function mouse model using CRISPR/Cas9 technology. We performed immunofluorescence and RT-qPCR to examine the protein and mRNA expression in testicular cells. We found that FAM71D was predominantly localized in the round and elongated spermatids. And FAM71D KO mice displayed normal development of germ cell and fertility. Furthermore, testicular histology and sperm concentration showed no significant difference between WT and KO mice. These data demonstrate that FAM71D is dispensable for mouse spermatogenesis and male fertility.

CCDC146 is required for sperm flagellum biogenesis and male fertility in mice

Multiple morphological abnormalities of the flagella (MMAF) is a severe disease of male infertility, while the pathogenetic mechanisms of MMAF are still incompletely understood. Previously, we found that the deficiency of Ccdc38 might be associated with MMAF. To understand the underlying mechanism of this disease, we identified the potential partner of this protein and found that the coiled-coil domain containing 146 (CCDC146) can interact with CCDC38. It is predominantly expressed in the testes, and the knockout of this gene resulted in complete infertility in male mice but not in females. The knockout of Ccdc146 impaired spermiogenesis, mainly due to flagellum and manchette organization defects, finally led to MMAF-like phenotype. Furthermore, we demonstrated that CCDC146 could interact with both CCDC38 and CCDC42. It also interacts with intraflagellar transport (IFT) complexes IFT88 and IFT20. The knockout of this gene led to the decrease of ODF2, IFT88, and IFT20 protein levels, but did not affect CCDC38, CCDC42, or ODF1 expression. Additionally, we predicted and validated the detailed interactions between CCDC146 and CCDC38 or CCDC42, and built the interaction models at the atomic level. Our results suggest that the testis predominantly expressed gene Ccdc146 is essential for sperm flagellum biogenesis and male fertility, and its mutations might be associated with MMAF in some patients.

Novel axonemal protein ZMYND12 interacts with TTC29 and DNAH1, and is required for male fertility and flagellum function

Male infertility is common and complex, presenting a wide range of heterogeneous phenotypes. Although about 50% of cases are estimated to have a genetic component, the underlying cause often remains undetermined. Here, from whole-exome sequencing on samples from 168 infertile men with asthenoteratozoospermia due to severe sperm flagellum, we identified homozygous ZMYND12 variants in four unrelated patients. In sperm cells from these individuals, immunofluorescence revealed altered localization of DNAH1, DNALI1, WDR66, and TTC29. Axonemal localization of ZMYND12 ortholog TbTAX-1 was confirmed using the Trypanosoma brucei model. RNAi knock-down of TbTAX-1 dramatically affected flagellar motility, with a phenotype similar to the sperm from men bearing homozygous ZMYND12 variants. Co-immunoprecipitation and ultrastructure expansion microscopy in T. brucei revealed TbTAX-1 to form a complex with TTC29. Comparative proteomics with samples from Trypanosoma and Ttc29 KO mice identified a third member of this complex: DNAH1. The data presented revealed that ZMYND12 is part of the same axonemal complex as TTC29 and DNAH1, which is critical for flagellum function and assembly in humans, and Trypanosoma. ZMYND12 is thus a new asthenoteratozoospermia-associated gene, bi-allelic variants of which cause severe flagellum malformations and primary male infertility.

Targeted Amino Acids Profiling of Human Seminal Plasma from Teratozoospermia Patients Using LC-MS/MS

Identifying the metabolome of human seminal plasma (HSP) is a new research area to screen putative biomarkers of infertility. This case-control study was performed on HSP specimens of 15 infertile patients with teratozoospermia (defined as normal sperm morphology < 4%) and 12 confirmed fertile normozoospermic men as the control group to investigate the seminal metabolic signature and whether there are differences in the metabolome between two groups. HSPs were subjected to LC-MS-MS analysis. MetaboAnalyst5.0 software was utilized for statistical analysis. Different univariate and multivariate analyses were used, including T-tests, fold change analysis, random forest (RF), and metabolite set enrichment analysis (MSEA). Teratozoospermic samples contained seventeen significantly different amino acids. Upregulated metabolites include glutamine, asparagine, and glycylproline, whereas downregulated metabolites include cysteine, γ-aminobutyric acid, histidine, hydroxylysine, hydroxyproline, glycine, proline, methionine, ornithine, tryptophan, aspartic acid, argininosuccinic acid, α-aminoadipic acid, and β-aminoisobutyric acid. RF algorithm defined a set of 15 metabolites that constitute the significant features of teratozoospermia. In particular, increased glutamine, asparagine, and decreased cysteine, tryptophan, glycine, and valine were strong predictors of teratozoospemia. The most affected metabolic pathways in teratozoospermic men are the aminoacyl-tRNA, arginine, valine-leucine, and isoleucine biosynthesis. Altered metabolites detected in teratozoospermia were responsible for various roles in sperm functions that classified into four subgroups as follows: related metabolites to antioxidant function, energy production, sperm function, and spermatogenesis. The altered amino acid metabolome identified in this study may be related to the etiology of teratozoospermia, and may provide novel insight into potential biomarkers of male infertility for therapeutic targets.

Results and perinatal outcomes from 189 ICSI cycles of couples with asthenozoospermic men and flagellar defects assessed by transmission electron microscopy

RESEARCH QUESTION

Do patients presenting with flagella ultrastructural defects as assessed by electron microscopy, and defined within three phenotypes (dysplasia of the fibrous sheath [DFS], primary flagellar dyskinesia [PFD] and non-specific flagellar abnormalities [NSFA]), have decreased chances of success in intracytoplasmic sperm injection (ICSI) or adverse obstetric and neonatal outcomes?

DESIGN

Retrospective analysis of 189 ICSI cycles from 80 men with spermatozoa flagellum ultrastructural defects (DFS [n = 16]; PFD [n = 14]; NSFA [n = 50] compared with a control group (n = 97). Cycles were cumulatively analysed. All fresh and frozen embryo transfers resulting from each ICSI attempt were included. The effect of transmission electron microscopy (TEM) phenotype on the main ICSI outcomes was assessed by a multivariate logistic regression combined with a generalized linear mixed model to account for the non-independence of the observations.

RESULTS

No predictive value of TEM phenotype was found on the main outcomes of ICSI, namely fertilization rates, pregnancy and delivery rates, and cumulative pregnancy and delivery rates. Cumulative pregnancy rates ranged from 29.0-43.3% in the different TEM phenotype subgroups compared with 36.8% in the control group. Cumulative live birth rates ranged from 24.6-36.7% compared with 31.4% in the control group. No increase was found in miscarriages, preterm births, low birth weights or birth abnormalities.

CONCLUSIONS

Data on the cumulative chances of success in ICSI of patients with ultrastructural flagellar defects, a rare cause of male infertility often associated with an underlying genetic cause, are reassuring, as are obstetrical and neonatal outcomes in this population.

Experimental and molecular support for Cfap70 as a causative gene of 'multiple morphological abnormalities of the flagella' with male infertility†

Multiple morphological abnormalities of the flagella, a severe form of asthenozoospermia, can lead to male infertility. Recent studies have implicated an association between human CFAP70 deficiency and multiple morphological abnormalities of the flagella; however, the underlying biological mechanism and supporting experimental evidence in animal models remain unclear. To address this gap, we used CRISPR/Cas9 technology to generate Cfap70-deficient mice to investigate the relationship between Cfap70 deficiency and multiple morphological abnormalities of the flagella. Our findings show that the loss of CFAP70 leads to multiple morphological abnormalities of the flagella and spermiogenesis defects. Specifically, the lack of CFAP70 impairs sperm flagellum biogenesis and head shaping during spermiogenesis. Late-step spermatids from Cfap70-deficient mouse testis exhibited club-shaped sperm heads and abnormal disassembly of the manchette. Furthermore, we found that CFAP70 interacts with DNAI1 and DNAI2; Cfap70 deficiency also reduces the level of AKAP3 in sperm flagella, indicating that CFAP70 may participate in the flagellum assembly and transport of flagellar components. These findings provide compelling evidence implicating Cfap70 as a causative gene of multiple morphological abnormalities of the flagella and highlight the consequences of CFAP70 loss on flagellum biogenesis.

Unveiling the Genetic Complexity of Teratozoospermia: Integrated Genomic Analysis Reveals Novel Insights into lncRNAs' Role in Male Infertility

Male infertility is a global health issue, affecting over 20 million men worldwide. Genetic factors are crucial in various male infertility forms, including teratozoospermia. Nonetheless, the genetic causes of male infertility remain largely unexplored. In this study, we employed whole-genome sequencing and RNA expression analysis to detect differentially expressed (DE) long-noncoding RNAs (lncRNAs) in teratozoospermia, along with mutations that are exclusive to teratozoospermic individuals within these DE lncRNAs regions. Bioinformatic tools were used to assess variants' impact on lncRNA structure, function, and lncRNA-miRNA interactions. Our analysis identified 1166 unique mutations in teratozoospermic men within DE lncRNAs, distinguishing them from normozoospermic men. Among these, 64 variants in 23 lncRNAs showed potential regulatory roles, 7 variants affected 4 lncRNA structures, while 37 variants in 17 lncRNAs caused miRNA target loss or gain. Pathway Enrichment and Gene Ontology analyses of the genes targeted by the affected miRNAs revealed dysregulated pathways in teratozoospermia and a link between male infertility and cancer. This study lists novel variants and lncRNAs associated for the first time with teratozoospermia. These findings pave the way for future studies aiming to enhance diagnosis and therapy in the field of male infertility.

Novel mutations in DNAH17 cause sperm flagellum defects and their influence on ICSI outcome

PURPOSE

To identify new mutations in DNAH17 that cause male infertility and analyze intracytoplasmic sperm injection (ICSI) outcomes in patients with DNAH17 mutations.

METHODS

A total of five cases of new DNAH17 mutations exhibiting the multiple morphological abnormalities of the sperm flagella (MMAF) phenotype were identified through semen analysis and genetic testing. They were recruited at our reproductive medicine center from September 2018 to July 2022. Information on DNAH17 genetic mutations and ICSI outcomes was systematically explored following a literature review.

RESULTS

Three novel compound mutations in DNAH17 were identified in patients with male infertility caused by MMAF. This study and previous publications included 21 patients with DNAH17 mutations. DNAH17 has been associated with asthenozoospermia and male infertility, but different types of DNAH17 variants appear to be involved in different sperm phenotypes. In 11 couples of infertile patients with DNAH17 mutations, there were 17 ICSI cycles and 13 embryo transplantation cycles. Only three men with DNAH17 variants ultimately achieved clinical pregnancy with their partners through ICSI combined with assisted oocyte activation (AOA).

CONCLUSIONS

Loss-of-function mutations in DNAH17 can lead to severe sperm flagellum defects and male infertility. Patients with MMAF-harboring DNAH17 mutations generally have worse pregnancy outcomes following ICSI. ICSI combined with AOA may improve the outcome of assisted reproductive techniques (ARTs) for men with DNAH17 variants.

CCDC189 affects sperm flagellum formation by interacting with CABCOCO1

Multiple morphological abnormalities of the sperm flagella (MMAF) are one of the major causes of male infertility and are characterized by multiple defects. In this study, we found that the coiled-coil domain-containing 189 (Ccdc189) gene was predominantly expressed in mouse testes and that inactivation of the Ccdc189 gene caused male infertility. Histological studies revealed that most sperm from Ccdc189-deficient mice carried coiled, curved or short flagella, which are typical MMAF phenotypes. Immunoelectron microscopy showed that the CCDC189 protein was located at the radial spoke of the first peripheral microtubule doublet in the sperm axoneme. A CCDC189-interacting protein, CABCOCO1 (ciliary-associated calcium-binding coiled-coil protein 1), was discovered via co-immunoprecipitation and mass spectrometry, and inactivation of Cabcoco1 caused malformation of sperm flagella, which was consistent with findings obtained with Ccdc189-deficient mice. Further studies revealed that inactivation of CCDC189 caused downregulation of CABCOCO1 protein expression and that both CCDC189 and CABCOCO1 interacted with the radial-spoke-specific protein RSPH1 and intraflagellar transport proteins. This study demonstrated that Ccdc189 is a radial-spoke-associated protein and is involved in sperm flagellum formation through its interactions with CABCOCO1 and intraflagellar transport proteins.

The use of ICSI in ART: evidence for practice

This article reviews the evidence regarding the safety and efficacy of intra-cytoplasmic sperm injection (ICSI). It provides evidence-based clinical and laboratory guidelines and recommendations for use of ICSI within an assisted reproductive technology (ART) service. The guidelines address the evidence for the use of ICSI rather than conventional IVF (cIVF); the use of ART techniques supplementary to ICSI; and risks associated with ICSI. This article is not intended to be the only approved standard of practice or to dictate an exclusive course of treatment. Other plans of management may be appropriate, taking into account the needs and medical history of the patient, available resources, and institutional or clinical practice limitations.

Structures of sperm flagellar doublet microtubules expand the genetic spectrum of male infertility

Sperm motility is crucial for successful fertilization. Highly decorated doublet microtubules (DMTs) form the sperm tail skeleton, which propels the movement of spermatozoa. Using cryo-electron microscopy (cryo-EM) and artificial intelligence (AI)-based modeling, we determined the structures of mouse and human sperm DMTs and built an atomic model of the 48-nm repeat of the mouse sperm DMT. Our analysis revealed 47 DMT-associated proteins, including 45 microtubule inner proteins (MIPs). We identified 10 sperm-specific MIPs, including seven classes of Tektin5 in the lumen of the A tubule and FAM166 family members that bind the intra-tubulin interfaces. Interestingly, the human sperm DMT lacks some MIPs compared with the mouse sperm DMT. We also discovered variants in 10 distinct MIPs associated with a subtype of asthenozoospermia characterized by impaired sperm motility without evident morphological abnormalities. Our study highlights the conservation and tissue/species specificity of DMTs and expands the genetic spectrum of male infertility.

Phytochemical consumption and the risk of teratozoospermia: findings from a hospital-based case-control study in China

STUDY QUESTION

Are dietary phytochemicals associated with the risk of teratozoospermia?

SUMMARY ANSWER

Dietary intake of carotene, including total carotene, α-carotene, β-carotene as well as retinol equivalent, and lutein + zeaxanthin, were inversely correlated with the risk of teratozoospermia.

WHAT IS KNOWN ALREADY

Phytochemicals are natural plant derived bioactive compounds, which have been reported to be potentially associated with male reproductive health. To date, no study has investigated the association between phytochemical intake and the risk of teratozoospermia.

STUDY DESIGN SIZE DURATION

This hospital-based case-control study, which included 146 newly diagnosed teratozoospermia cases and 581 controls with normozoospermia from infertile couples, was conducted in a hospital-based infertility clinic in China, from June 2020 to December 2020.

PARTICIPANTS/MATERIALS SETTING METHODS

Dietary information was collected using a validated semi-quantitative 110-item food frequency questionnaire. Unconditional logistic regression was applied to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between phytochemical (i.e. phytosterol, carotene, flavonoid, isoflavone, anthocyanidin, lutein + zeaxanthin, and resveratrol) intake and the risk of teratozoospermia.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed a decreased risk of teratozoospermia for the highest compared with the lowest tertile consumption of total carotene (OR = 0.40, 95% CI = 0.21-0.77), α-carotene (OR = 0.53, 95% CI = 0.30-0.93), β-carotene (OR = 0.47, 95% CI = 0.25-0.88), retinol equivalent (OR = 0.47, 95% CI = 0.24-0.90), and lutein + zeaxanthin (OR = 0.35, 95% CI = 0.19-0.66), with all of the associations showing evident linear trends (all P trend <0.05). In addition, significant dose-response associations were observed between campestanol and α-carotene consumption and the risk of teratozoospermia. Moreover, there was a significant multiplicative interaction between BMI and lutein + zeaxanthin intake (P interaction <0.05).

LIMITATIONS REASONS FOR CAUTION

The cases and controls were not a random sample of the entire target population, which could lead to admission rate bias. Nevertheless, the controls were enrolled from the same infertility clinic, which could reduce the bias caused by selection and increase the comparability. Furthermore, our study only included a Chinese population, therefore caution is required regarding generalization of our findings to other populations.

WIDER IMPLICATIONS OF THE FINDINGS

Dietary phytochemicals, namely carotene, lutein, and zeaxanthin, might exert a positive effect on teratozoospermia. These phytochemicals are common in the daily diet and dietary supplements, and thus may provide a preventive intervention for teratozoospermia.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by Natural Science Foundation of Liaoning Province (No. 2022-MS-219 to X.B.W.), Outstanding Scientific Fund of Shengjing Hospital (No. M1150 to Q.J.W.), Clinical Research Cultivation Project of Shengjing Hospital (No. M0071 to B.C.P.), and JieBangGuaShuai Project of Liaoning Province (No. 2021JH1/1040050 to Y.H.Z.). All authors declared that there was no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Novel homozygous variants in TTC12 cause male infertility with asthenoteratozoospermia owing to dynein arm complex and mitochondrial sheath defects in flagella

Introduction: Tracing the genetic causes for male infertility due to asthenoteratozoospermia has revealed at least 40 causative genes, which provides valuable reference for the genetic testing of asthenoteratozoospermia in clinical practice. To identify deleterious variants in the human tetratricopeptide repeat domain 12 (TTC12) gene in a large cohort of infertile Chinese males with asthenoteratozoospermia. Methods: A total of 314 unrelated asthenoteratozoospermia-affected men were recruited for whole exome sequencing. The effects of the identified variants were evaluated by in silico analysis, and confirmed by in vitro experiments. Intracytoplasmic sperm injection (ICSI) was used to evaluate the efficiency of assisted reproduction technique therapy. Results and Discussion: Novel homozygous TTC12 variants (c.1467_1467delG (p.Asp490Thrfs*14), c.1139_1139delA (p.His380Profs*4), and c.1117G>A (p.Gly373Arg)) were identified in three (0.96%) of the 314 cases. Three mutants were indicated to be damaging using in silico prediction tools, and were further confirmed by in vitro functional analysis. Hematoxylin and eosin staining and ultrastructural observation of the spermatozoa revealed multiple morphological abnormalities of flagella, with the absence of outer and inner dynein arms. Notably, significant mitochondrial sheath malformations were also observed in the sperm flagella. Immunostaining assays indicated that TTC12 is present throughout the flagella, and was strongly concentrated in the mid-piece in control spermatozoa. However, spermatozoa from TTC12-mutated individuals exhibited almost no staining intensity of TTC12 and outer and inner dynein arms components. The three men accepted ICSI treatment using their ejaculated spermatozoa, and two female partners successfully delivered healthy babies. Our findings provide direct genetic evidence that homozygous variants in TTC12 cause male infertility with asthenoteratozoospermia by causing dynein arm complex defects and mitochondrial sheath malformations in the flagellar. We also demonstrated that TTC12 deficiency-mediated infertility could be overcome by ICSI technology.

Microcystin leucine arginine induces human sperm damage: Involvement of the Ca2+/CaMKKβ/AMPK pathway

As a common pollutant in the water environment, microcystin leucine arginine (MC-LR) can enter semen and damage the sperm in animals. However, the mechanism by which MC-LR damages human sperm is unclear. Therefore, human sperm samples were obtained from the Henan Provincial Sperm Bank and exposed to different concentrations (0, 1, 10, and 100 μg/L) of MC-LR for 1, 2, 4, and 6 h, to invegest the effects and potential mechanism of MC-LR on sperm. The results showed that MC-LR mainly accumulated in the neck and flagellum of human sperm. Compared to the control group, the sperm capacitation rate and motility were significantly decreased in the 100 μg/L group. After exposure of 100 μg/L of MC-LR, the central microtubule and microtubule doublet of sperm flagellum were blurred, asymmetrical, or even lost. Furthermore, the expression levels of flagellin DNAH17, SPEF2, SPAG16, SPAG6, and CFAP44 in human sperm were reduced. Also, the phosphorylation levels of CaMKKβ and AMPK can be inhibited by MC-LR. These findings revealed that MC-LR can induce functional and structural damage in human sperm, and the Ca²⁺/CaMKKβ/AMPK pathway may be involved in this process. This study will provide a basis for prevention and treatment of male fertility declines caused by MC-LR.

Biallelic variants in IQCN cause sperm flagellar assembly defects and male infertility

STUDY QUESTION

What is the effect of defects in the manchette protein IQ motif-containing N (IQCN) on sperm flagellar assembly?

SUMMARY ANSWER

Deficiency in IQCN causes sperm flagellar assembly defects and male infertility.

WHAT IS KNOWN ALREADY

The manchette is a transient structure that is involved in the shaping of the human spermatid nucleus and protein transport within flagella. Our group recently reported that the manchette protein IQCN is essential for fertilization. Variants in IQCN lead to total fertilization failure and defective acrosome structure phenotypes. However, the function of IQCN in sperm flagellar assembly is still unknown.

STUDY DESIGN, SIZE, DURATION

Fifty men with infertility were recruited from a university-affiliated center from January 2014 to October 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Genomic DNA was extracted from the peripheral blood samples of all 50 individuals for whole-exome sequencing. The ultrastructure of the spermatozoa was assessed by transmission electron microscopy. Computer-assisted sperm analysis (CASA) was used to test the parameters of curvilinear velocity (VCL), straight-line velocity (VSL), and average path velocity (VAP). An Iqcn knockout (Iqcn-/-) mouse model was generated by CRISPR-Cas9 technology to evaluate sperm motility and the ultrastructure of the flagellum. Hyperactivation and sperm fertilizing ability were assessed in a mouse model. Immunoprecipitation followed by liquid chromatography-mass spectrometry was used to detect IQCN-binding proteins. Immunofluorescence was used to validate the localization of IQCN-binding proteins.

MAIN RESULTS AND THE ROLE OF CHANCE

Biallelic variants in IQCN (c.3913A>T and c.3040A>G; c.2453_2454del) were identified in our cohort of infertile men. The sperm from the affected individuals showed an irregular '9 + 2' structure of the flagellum, which resulted in abnormal CASA parameters. Similar phenotypes were observed in Iqcn-/- male mice. VSL, VCL, and VAP in the sperm of Iqcn-/- male mice were significantly lower than those in Iqcn+/+ male mice. Partial peripheral doublet microtubules (DMTs) and outer dense fibers (ODFs) were absent, or a chaotic arrangement of DMTs was observed in the principal piece and end piece of the sperm flagellum. Hyperactivation and IVF ability were impaired in Iqcn-/- male mice. In addition, we investigated the causes of motility defects and identified IQCN-binding proteins including CDC42 and the intraflagellar transport protein families that regulate flagellar assembly during spermiogenesis.

LIMITATIONS, REASONS FOR CAUTION

More cases are needed to demonstrate the relation between IQCN variants and phenotypes.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings expand the genetic and phenotypic spectrum of IQCN variants in causing male infertility, providing a genetic marker for sperm motility deficiency and male infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Natural Science Foundation of China (81974230 and 82202053), the Changsha Municipal Natural Science Foundation (kq2202072), the Hunan Provincial Natural Science Foundation (2022JJ40658), and the Scientific Research Foundation of Reproductive and Genetic Hospital of CITIC-Xiangya (YNXM-202114 and YNXM-202201). No conflicts of interest were declared.

TRIAL REGISTRATION NUMBER

N/A.

Molecular genetic mechanisms of teratozoospermia

In recent years, the incidence of teratospermia has been increasing, and it has become a very important factor leading to male infertility. The research on the molecular mechanism of teratospermia is also progressing rapidly. This article briefly summarizes the clinical incidence of teratozoospermia, and makes a retrospective summary of related studies reported in recent years. Specifically discussing the relationship between gene status and spermatozoa, the review aims to provide the basis for the genetic diagnosis and gene therapy of teratozoospermia.

Focus on centrin in normal and altered human spermatozoa

This review provides details on the role of centrin in human spermatozoa and in various forms of male infertility. Centrin is a calcium (Ca²⁺)-binding phosphoprotein that is located in the centrioles - which are typical structures of the sperm connecting piece and play a key role in centrosome dynamics during sperm morphogenesis - as well as in zygotes and early embryos during spindle assembly. In humans, three different centrin genes encoding three isoforms have been discovered. Centrin 1, the only one expressed in spermatozoa, seems to be lost inside the oocyte after fertilization. The sperm connecting piece is characterized by the presence of numerous proteins including centrin, that deserves particular attention because, in humans, it is enriched during maturation of the centrioles. In normal sperm, centrin 1 is visible as two distinct spots in the head-tail junction; however, in some defective spermatozoa, centrin 1 distribution is altered. Centrin has been studied in humans and animal models. Its mutations may lead to several structural alterations, such as serious defects in the connective piece and, subsequently, fertilization failure or incomplete embryonic development. However, the effects of these abnormalities on male fertility have not been fully studied. Because the presence and the function of centrin in the sperm connecting piece appears important for reproductive success, additional studies are needed to bring medical benefits in resolving some cases of idiopathic infertility.

Human globozoospermia-related genes and their role in acrosome biogenesis

The mammalian acrosome is a secretory vesicle attached to the sperm nucleus whose fusion with the overlying plasma membrane is required to achieve fertilization. Acrosome biogenesis starts during meiosis, but it lasts through the entire process of haploid cell differentiation (spermiogenesis). Acrosome biogenesis is a stepwise process that involves membrane traffic from the Golgi apparatus, but it also seems that the lysosome/endosome system participates in this process. Defective sperm head morphology is accompanied by defective acrosome shape and function, and patients with these characteristics are infertile or subfertile. The most extreme case of acrosome biogenesis failure is globozoospermia syndrome, which is primarily characterized by the presence of round-headed spermatozoa without acrosomes with cytoskeleton defects around the nucleus and infertility. Several genes participating in acrosome biogenesis have been uncovered using genetic deletions in mice, but only a few of them have been found to be deleted or modified in patients with globozoospermia. Understanding acrosome biogenesis is crucial to uncovering the molecular basis of male infertility and developing new diagnostic tools and assisted reproductive technologies that may help infertile patients through more effective treatment techniques. This article is categorized under: Reproductive System Diseases > Environmental Factors Infectious Diseases > Stem Cells and Development Reproductive System Diseases > Molecular and Cellular Physiology.

FSIP2 plays a role in the acrosome development during spermiogenesis

BACKGROUND

Loss-of-function mutations in FSIP2 result in multiple morphological abnormalities of the flagella in humans and mice. Intriguingly, a recent study found that FSIP2 might regulate the expression of acrosomal proteins, indicating that Fsip2 might be involved in acrosome development in mice. However, whether FSIP2 also function in acrosome biogenesis in humans is largely unknown, and the underlying mechanism of which is unexplored.

OBJECTIVE

Our objective was to reveal potential function of FSIP2 in regulating sperm acrosome formation.

METHODS

We performed whole exome sequencing on four asthenoteratozoospermic patients. Western blot analysis and immunofluorescence staining were conducted to assess the protein expression of FSIP2. Proteomics approach, liquid chromatography-tandem mass spectrometry and co-immunoprecipitation were implemented to clarify the molecules in acrosome biogenesis regulated by FSIP2.

RESULTS

Biallelic FSIP2 variants were identified in four asthenoteratozoospermic individuals. The protein expression of MUT-FSIP2 was sharply decreased or absent in vitro or in vivo. Interestingly, aside from the sperm flagellar defects, the acrosomal hypoplasia was detected in numerous sperm from the four patients. FSIP2 co-localised with peanut agglutinin in the acrosome during spermatogenesis. Moreover, FSIP2 interacted with proteins (DPY19L2, SPACA1, HSP90B1, KIAA1210, HSPA2 and CLTC) involved in acrosome biogenesis. In addition, spermatozoa from patients carrying FSIP2 mutations showed downregulated expression of DPY19L2, ZPBP, SPACA1, CCDC62, CCIN, SPINK2 and CSNK2A2.

CONCLUSION

Our findings unveil that FSIP2 might involve in sperm acrosome development, and consequently, its mutations might contribute to globozoospermia or acrosomal aplasia. We meanwhile first uncover the potential molecular mechanism of FSIP2 regulating acrosome biogenesis.

Deficiency of cancer/testis antigen gene CT55 causes male infertility in humans and mice

The Cancer/Testis Antigen (CTA) genes comprise a group of genes whose expression under physiological conditions is restricted to the testis but is activated in many human cancers. Depending on the particular expression pattern, the CTA genes are speculated to play a role in spermatogenesis, but evidence is limited thus far. Here, we reported patients with a hemizygous nonsense mutation in cancer-testis antigen 55 (CT55) suffering from male infertility with extreme disruption in sperm production, morphology, and locomotion. Specifically, the insufficiency of sperm individualization, excessive residue of unnecessary cytoplasm, and defects in acrosome development were evident in the spermatozoa of the patients. Furthermore, mouse models with depletion of Ct55 showed accelerated infertility with age, mimicking the defects in sperm individualization, unnecessary cytoplasm removal, and meanwhile exhibiting the disrupted cumulus-oocyte complex penetration. Mechanistically, our functional experiments uncovered CT55 as a new autophagic manipulator to regulate spermatogenesis via selectively interacting with LAMP2 and GABARAP (which are key regulators in the autophagy process) and further fine-tuning their expression. Therefore, our findings revealed CT55 as a novel CTA gene involved in spermatogenesis due to its unprecedented autophagy activity.

New Mutations in DNHD1 Cause Multiple Morphological Abnormalities of the Sperm Flagella

Male infertility is a common and complex disease and presents as a wide range of heterogeneous phenotypes. Multiple morphological abnormalities of the sperm flagellum (MMAF) phenotype is a peculiar condition of extreme morphological sperm defects characterized by a mosaic of sperm flagellum defects to a total asthenozoospermia. At this time, about 40 genes were associated with the MMAF phenotype. However, mutation prevalence for most genes remains individually low and about half of individuals remain without diagnosis, encouraging us to pursue the effort to identify new mutations and genes. In the present study, an a cohort of 167 MMAF patients was analyzed using whole-exome sequencing, and we identified three unrelated patients with new pathogenic mutations in DNHD1, a new gene recently associated with MMAF. Immunofluorescence experiments showed that DNHD1 was totally absent from sperm cells from DNHD1 patients, supporting the deleterious effect of the identified mutations. Transmission electron microscopy reveals severe flagellum abnormalities of sperm cells from one mutated patient, which appeared completely disorganized with the absence of the central pair and midpiece defects with a shortened and misshapen mitochondrial sheath. Immunostaining of IFT20 was not altered in mutated patients, suggesting that IFT may be not affected by DNHD1 mutations. Our data confirmed the importance of DNHD1 for the function and structural integrity of the sperm flagellum. Overall, this study definitively consolidated its involvement in MMAF phenotype on a second independent cohort and enriched the mutational spectrum of the DNHD1 gene.

Impact of antioxidants in improving semen parameters like count, motility and DNA fragmentation in sub-fertile males: a randomized, double-blind, placebo-controlled clinical trial

Male infertility is solely responsible for 20-30% of infertility cases. Oxidative damage of sperm DNA is positively linked with oligoasthenoteratozoospermia (OAT), and male infertility. The antioxidants are being explored worldwide to combat OAT, sperm DNA fragmentation and reactive oxygen species. The objective of the study was to assess the effectiveness of an antioxidant blend in improving sperm count, semen parameters and reducing DNA fragmentation index (DFI) in sub-fertile males. A prospective, double-blind, randomized, placebo-controlled trial was conducted in 300 sub-fertile males (25-45 years) from ten study sites in India. Subjects were randomized in either the antioxidant blend treatment group or placebo group. We assessed changes in sperm count, motility, normal morphology, semen volume, and percent DFI before and after treatment (90 days). To further stratify data on different criteria post hoc analysis was performed. Statistical analysis was performed using SPSS 10.0 software. There were improvements in sperm count, semen volume, sperm motility, and sperm normal morphology in the treatment group. There was improvement in sperm count in severe oligospermia subjects (sperm count < 5 million/mL, 5-10 million/mL, 10.1-15 million/mL), and high-extremely higher baseline DFI (20-30%, 31-40% and above 40%), as per post hoc analysis. There was no premature discontinuation and adverse events were reported during the study, indicating safety and well-tolerability of treatment. Study results confirmed the well-researched fact of antioxidants being effective to reduce oxidative stress and thus improve sperm DNA integrity and also improved semen parameters in males aged 40 and above.

Trial Registration

Clinical Trials Registry-India Identifier: CTRI/2020/12/029590.

Biallelic loss-of-function mutations in SEPTIN4 (C17ORF47), encoding a conserved annulus protein, cause thin midpiece spermatozoa and male infertility in humans

Asthenoteratozoospermia is the primary cause of infertility in humans. However, the genetic etiology remains largely unknown for those suffering from severe asthenoteratozoospermia caused by thin midpiece defects. In this study, we identified two biallelic loss-of-function variants of SEPTIN4 (previously SEPT4) (Patient 1: c.A721T, p.R241* and Patient 2: c.C205T, p.R69*) in two unrelated individuals from two consanguineous Chinese families. SEPT4 is a conserved annulus protein that is critical for male fertility and the structural integrity of the sperm midpiece in mice. SEPT4 mutations disrupted the formation of SEPT-based annulus and localization of SEPTIN subunits in sperms from patients. The ultrastructural analysis demonstrated striking thin midpiece spermatozoa defects owing to annulus loss and disorganized mitochondrial sheath. Immunofluorescence and immunoblotting analyses of the mitochondrial sheath proteins TOMM20 and HSP60 further indicated that the distribution and abundance of mitochondria were impaired in men harboring biallelic SEPT4 variants. Additionally, we found that the precise localization of SLC26A8, a testis-specific anion transporter that colocalizes with SEPT4 at the sperm annulus, was missing without SEPT4. Moreover, the patient achieved a good pregnancy outcome following intracytoplasmic sperm injection. Overall, our study demonstrated for the first time that SEPT4 variants that induced thin midpiece spermatozoa defects were directly associated with human asthenoteratozoospermia.

Sperm selection with Annexin-V coated polystrene bead technique (APB-Tech): A novel and reliable method for the microscopic selection of viable and non-apoptotic sperm to be used for intracytoplasmic sperm injection

Infertility is a growing health problem that affects 20% of couples who want to conceive. 'Intracytoplasmic sperm injection' (ICSI) is a commonly used assisted reproduction treatment technique that offers the couples to overcome a wide variety of infertility reasons, including female, male and unexplained infertility. A crucial step in ICSI is choosing the correct sperm with the highest potential to form a healthy embryo and thus a healthy offspring. The sperm selection strategies aim to obtain a sperm population with better motility and morphology, which are insufficient to predict a sperm's reproductive potential. The elimination of apoptotic sperms, which is shown to be higher in infertile males and which is shown to affect embryo development and reproductive cohort significantly should also be included in the selection strategies. Among all sperm selection methods, there are only a few which can eliminate apoptotic sperm, but because they need extra types of equipments, a long training period, and high costs, they couldn't find place in the most commonly used techniques in an IVF lab. Selecting the non-apoptotic sperm cells will help us choose a sperm that is more likely to be chosen by the natural selection mechanisms and thus will help to mimic the natural conception more. The study aimed to develop a novel, easy and a harmless individual sperm selection technique to enable choosing non-apoptotic viable sperm cells via light microscopy without any need for extra equipment, education and cost to be used for ''ICSI'. The technique is based on the binding ability of Annexin-V covered polystrene beads to the externalized phosphatidylserine at the outer leaflet of an apoptotic sperm's plasma membrane. After Annexin-V covered polystyrene beads were prepared, beads obtained were attached to BALB-c mice sperm, and the technique is optimized to obtain the most efficient attachment conditions. The results are then compared with the results of four well-known reliable apoptosis detection techniques to test the validity and sperm survival test to test the toxicity of the technique. The method is proven to be '''reliable' by comparing it with the results of well-known techniques, including TUNEL and SCSA (sperm chromatin structure assay), and '''safe' by showing its non-toxicity via sperm survival test (SST). In addition, the method enables the selection of sperm cells more closer to naturally-chosen ones from a pool of sperm that should not be allowed to be randomly chosen during microinjection. To date, it was impossible to distinguish a non-apoptotic sperm without harming it or without needing additional equipment other than a routine IVF lab and extra training other than routine andrology work. The technique is named as 'Annexin-V coated polystyrene bead technique (APB-Tech)'. Based on our results, further studies on APB-Tech should be focused on the possible improvement of ICSI outcomes and, thus, success rates.

Clinical detection, diagnosis and treatment of morphological abnormalities of sperm flagella: A review of literature

Sperm carries male genetic information, and flagella help move the sperm to reach oocytes. When the ultrastructure of the flagella is abnormal, the sperm is unable to reach the oocyte and achieve insemination. Multiple morphological abnormalities of sperm flagella (MMAF) is a relatively rare idiopathic condition that is mainly characterized by multiple defects in sperm flagella. In the last decade, with the development of high-throughput DNA sequencing approaches, many genes have been revealed to be related to MMAF. However, the differences in sperm phenotypes and reproductive outcomes in many cases are attributed to different pathogenic genes or different pathogenic mutations in the same gene. Here, we will review information about the various phenotypes resulting from different pathogenic genes, including sperm ultrastructure and encoding proteins with their location and functions as well as assisted reproductive technology (ART) outcomes. We will share our clinical detection and diagnosis experience to provide additional clinical views and broaden the understanding of this disease.