Genetic analyses of a large cohort of infertile patients with globozoospermia, DPY19L2 still the main actor, GGN confirmed as a guest player

Exome-wide association study reveals 7 functional variants associated with ex-vivo drug response in acute myeloid leukemia patients

Acute myeloid leukemia (AML) is an aggressive blood cancer characterized by poor survival outcomes. Further, due to the extreme molecular heterogeneity of the disease, drug treatment response varies from patient to patient. The variability of drug response can cause unnecessary treatment in more than half of the patients with no or partial therapy responses leading to severe side effects, monetary as well as time loss. Understanding the genetic risk factors underlying the drug response in AML can help with improved prediction of treatment responses and identification of biomarkers in addition to mechanistic insights to monitor treatment response. Here, we report the results of the first Exome-Wide Association Study (EWAS) of ex-vivo drug response performed to date with 175 AML cases and 47 drugs. We used information from 55,423 germline exonic SNPs to perform the analysis. We identified exome-wide significant (p < 9.02 × 10- 7) associations for rs113985677 in CCIN with tamoxifen response, rs115400838 in TRMT5 with idelalisib response, rs11878277 in HDGFL2 with entinostat, and rs2229092 in LTA associated with vorinostat response. Further, using multivariate genome-wide association analysis, we identified the association of rs11556165 in ATRAID, and rs11236938 in TSKU with the combined response of all 47 drugs and 29 nonchemotherapy drugs at the genome-wide significance level (p < 5 × 10- 8). Additionally, a significant association of rs35704242 in NIBAN1 was associated with the combined response for nonchemotherapy medicines (p = 2.51 × 10- 8), and BI.2536, gefitinib, and belinostat were identified as the central traits. Our study represents the first EWAS to date on ex-vivo drug response in AML and reports 7 new associated loci that help to understand the anticancer drug response in AML patients.

Molecular insights into sperm head shaping and its role in human male fertility

BACKGROUND

Sperm head shaping, controlled by the acrosome-acroplaxome-manchette complex, represents a significant morphological change during spermiogenesis and involves numerous proteins expressed in a spatially and temporally specific manner. Defects in sperm head shaping frequently lead to teratozoospermia concomitant with oligozoospermia and asthenozoospermia, but the pathogenic mechanism underlying sperm head shaping, and its role in male infertility, remain poorly understood.

OBJECTIVE AND RATIONALE

This review aims to summarize the mechanism underlying sperm head shaping, reveal the relationship between gene defects associated with sperm head shaping and male infertility in humans and mice, and explore potential clinical improvements in ICSI treatment.

SEARCH METHODS

We searched the PubMed database for articles published in English using the keyword 'sperm head shaping' in combination with the following terms: 'acrosome formation', 'proacrosomal vesicles (PAVs)', 'manchette', 'perinuclear theca (PT)', 'chromatin condensation', 'linker of nucleoskeleton and cytoskeleton (LINC) complex', 'histone-to-protamine (HTP) transition', 'male infertility', 'ICSI', and 'artificial oocyte activation (AOA)'. The selected publications until 1 August 2024 were critically summarized, integrated, and thoroughly discussed, and the irrelevant literature were excluded.

OUTCOMES

A total of 6823 records were retrieved. After careful screening, integrating relevant literature, and excluding articles unrelated to the topic of this review, 240 articles were ultimately included in the analysis. Firstly, we reviewed the important molecular events and structures integral to sperm head shaping, including PAV formation to fusion, acrosome attachment to the nucleus, structure and function of the manchette, PT, chromatin condensation, and HTP transition. Then, we set forth human male infertility associated with sperm head shaping and identified genes related to sperm head shaping resulting in teratozoospermia concomitant with oligozoospermia and asthenozoospermia. Finally, we summarized the outcomes of ICSI in cases of male infertility resulting from mutations in the genes associated with sperm head shaping, as well as the ICSI outcomes through AOA for infertile men with impaired sperm head.

WIDER IMPLICATIONS

Understanding the molecular mechanisms of sperm head shaping and its relationship with human male infertility holds profound clinical implications, which may contribute to risk prediction, genetic diagnosis, and the potential treatment of human male infertility.

Golgi pH elevation due to loss of V-ATPase subunit V0a2 function correlates with tissue-specific glycosylation changes and globozoospermia

Loss-of-function variants in ATP6V0A2, encoding the trans Golgi V-ATPase subunit V0a2, cause wrinkly skin syndrome (WSS), a connective tissue disorder with glycosylation defects and aberrant cortical neuron migration. We used knock-out (Atp6v0a2-/-) and knock-in (Atp6v0a2RQ/RQ) mice harboring the R755Q missense mutation selectively abolishing V0a2-mediated proton transport to investigate the WSS pathomechanism. Homozygous mutants from both strains displayed a reduction of growth, dermis thickness, and elastic fiber formation compatible with WSS. A hitherto unrecognized male infertility due to globozoospermia was evident in both mouse lines with impaired Golgi-derived acrosome formation and abolished mucin-type O-glycosylation in spermatids. Atp6v0a2-/- mutants showed enhanced fucosylation and glycosaminoglycan modification, but reduced levels of glycanated decorin and sialylation in skin and/or fibroblasts, which were absent or milder in Atp6v0a2RQ/RQ. Atp6v0a2RQ/RQ mutants displayed more abnormal migration of cortical neurons, correlating with seizures and a reduced O-mannosylation of α-dystroglycan. While anterograde transport within the secretory pathway was similarly delayed in both mutants the brefeldin A-induced retrograde fusion of Golgi membranes with the endoplasmic reticulum was less impaired in Atp6v0a2RQ/RQ. Measurement of the pH in the trans Golgi compartment revealed a shift from 5.80 in wildtype to 6.52 in Atp6v0a2-/- and 6.25 in Atp6v0a2RQ/RQ. Our findings suggest that altered O-glycosylation is more relevant for the WSS pathomechanism than N-glycosylation and leads to a secondary dystroglycanopathy. Most phenotypic and cellular properties correlate with the different degrees of trans Golgi pH elevation in both mutants underlining the fundamental relevance of pH regulation in the secretory pathway.

Atypical structure of the nuclear membrane, distribution of nuclear pores and lamin B1 in spermatozoa of patients with complete and partial globozoospermia

Globozoospermia is a form of male infertility characterized by spermatozoa with spherical heads lacking acrosomes. The aim of this study was to evaluate ultrastructural and molecular defects in different types of globozoospermia. Semen samples from 12 infertile patients (9 with complete globozoospermia and 3 with partial globozoospermia) and 10 normozoospermic men (control) were examined by transmission electron microscopy and immunocytochemistry with antibodies against lamin B1. The presence of lamin A and progerin was assessed by reverse transcription-PCR. Whole exome sequencing was performed in three patients. In semen samples with complete and partial globozoospermia, lamin B1 was observed at the periphery of sperm nuclei, whereas lamin A and progerin were absent. Nuclear envelope pores were found in spermatozoa from both patient groups, regardless of morphology and chromatin condensation, in contrast to the control group. Non-condensed chromatin was present in 51%-81% of cases of complete globozoospermia and in 36%-79% of cases of partial globozoospermia. Homozygous DPY19L2 and SPATA16 variants were identified in two patients with partial globozoospermia and one patient with complete globozoospermia. An atypical nuclear membrane with abnormal nuclear pore distribution and lamin B1 localization was observed in spermatozoa from patients with both complete and partial globozoospermia. The genetic defects in the DPY19L2 and SPATA16 genes detected in patients from both globozoospermic groups suggest a generalized disruption of nuclear structure in globozoospermia, highlighting the genetic and phenotypic similarities between complete and partial globozoospermia.

Conserved genes regulating human sex differentiation, gametogenesis and fertilization

The study of the functional genome in mice and humans has been instrumental for describing the conserved molecular mechanisms regulating human reproductive biology, and for defining the etiologies of monogenic fertility disorders. Infertility is a reproductive disorder that includes various conditions affecting a couple's ability to achieve a healthy pregnancy. Recent advances in next-generation sequencing and CRISPR/Cas-mediated genome editing technologies have facilitated the identification and characterization of genes and mechanisms that, if affected, lead to infertility. We report established genes that regulate conserved functions in fundamental reproductive processes (e.g., sex determination, gametogenesis, and fertilization). We only cover genes the deletion of which yields comparable fertility phenotypes in both rodents and humans. In the case of newly-discovered genes, we report the studies demonstrating shared cellular and fertility phenotypes resulting from loss-of-function mutations in both species. Finally, we introduce new model systems for the study of human reproductive biology and highlight the importance of studying human consanguineous populations to discover novel monogenic causes of infertility. The rapid and continuous screening and identification of putative genetic defects coupled with an efficient functional characterization in animal models can reveal novel mechanisms of gene function in human reproductive tissues.

Genetic mechanisms of fertilization failure and early embryonic arrest: a comprehensive review

BACKGROUND

Infertility and pregnancy loss are longstanding problems. Successful fertilization and high-quality embryos are prerequisites for an ongoing pregnancy. Studies have proven that every stage in the human reproductive process is regulated by multiple genes and any problem, at any step, may lead to fertilization failure (FF) or early embryonic arrest (EEA). Doctors can diagnose the pathogenic factors involved in FF and EEA by using genetic methods. With the progress in the development of new genetic technologies, such as single-cell RNA analysis and whole-exome sequencing, a new approach has opened up for us to directly study human germ cells and reproductive development. These findings will help us to identify the unique mechanism(s) that leads to FF and EEA in order to find potential treatments.

OBJECTIVE AND RATIONALE

The goal of this review is to compile current genetic knowledge related to FF and EEA, clarifying the mechanisms involved and providing clues for clinical diagnosis and treatment.

SEARCH METHODS

PubMed was used to search for relevant research articles and reviews, primarily focusing on English-language publications from January 1978 to June 2023. The search terms included fertilization failure, early embryonic arrest, genetic, epigenetic, whole-exome sequencing, DNA methylation, chromosome, non-coding RNA, and other related keywords. Additional studies were identified by searching reference lists. This review primarily focuses on research conducted in humans. However, it also incorporates relevant data from animal models when applicable. The results were presented descriptively, and individual study quality was not assessed.

OUTCOMES

A total of 233 relevant articles were included in the final review, from 3925 records identified initially. The review provides an overview of genetic factors and mechanisms involved in the human reproductive process. The genetic mutations and other genetic mechanisms of FF and EEA were systematically reviewed, for example, globozoospermia, oocyte activation failure, maternal effect gene mutations, zygotic genome activation abnormalities, chromosome abnormalities, and epigenetic abnormalities. Additionally, the review summarizes progress in treatments for different gene defects, offering new insights for clinical diagnosis and treatment.

WIDER IMPLICATIONS

The information provided in this review will facilitate the development of more accurate molecular screening tools for diagnosing infertility using genetic markers and networks in human reproductive development. The findings will also help guide clinical practice by identifying appropriate interventions based on specific gene mutations. For example, when an individual has obvious gene mutations related to FF, ICSI is recommended instead of IVF. However, in the case of genetic defects such as phospholipase C zeta1 (PLCZ1), actin-like7A (ACTL7A), actin-like 9 (ACTL9), and IQ motif-containing N (IQCN), ICSI may also fail to fertilize. We can consider artificial oocyte activation technology with ICSI to improve fertilization rate and reduce monetary and time costs. In the future, fertility is expected to be improved or restored by interfering with or supplementing the relevant genes.

Advances in the study of genetic factors and clinical interventions for fertilization failure

Fertilization failure refers to the failure in the pronucleus formation, evaluating 16-18 h post in vitro fertilization or intracytoplasmic sperm injection. It can be caused by sperm, oocytes, and sperm-oocyte interaction and lead to great financial and physical stress to the patients. Recent advancements in genetics, molecular biology, and clinical-assisted reproductive technology have greatly enhanced research into the causes and treatment of fertilization failure. Here, we review the causes that have been reported to lead to fertilization failure in fertilization processes, including the sperm acrosome reaction, penetration of the cumulus and zona pellucida, recognition and fusion of the sperm and oocyte membranes, oocyte activation, and pronucleus formation. Additionally, we summarize the progress of corresponding treatment methods of fertilization failure. This review will provide the latest research advances in the genetic aspects of fertilization failure and will benefit both researchers and clinical practitioners in reproduction and genetics.

Structure, sequon recognition and mechanism of tryptophan C-mannosyltransferase

C-linked glycosylation is essential for the trafficking, folding and function of secretory and transmembrane proteins involved in cellular communication processes. The tryptophan C-mannosyltransferase (CMT) enzymes that install the modification attach a mannose to the first tryptophan of WxxW/C sequons in nascent polypeptide chains by an unknown mechanism. Here, we report cryogenic-electron microscopy structures of Caenorhabditis elegans CMT in four key states: apo, acceptor peptide-bound, donor-substrate analog-bound and as a trapped ternary complex with both peptide and a donor-substrate mimic bound. The structures indicate how the C-mannosylation sequon is recognized by this CMT and its paralogs, and how sequon binding triggers conformational activation of the donor substrate: a process relevant to all glycosyltransferase C superfamily enzymes. Our structural data further indicate that the CMTs adopt an unprecedented electrophilic aromatic substitution mechanism to enable the C-glycosylation of proteins. These results afford opportunities for understanding human disease and therapeutic targeting of specific CMT paralogs.

Novel homozygous variant of CCIN causes male infertility owing to the abnormal sperm head with a nuclear subsidence phenotype

(A) Characteristics of spermatozoa in asthenoteratozoospermia affected man. (B) Pedigree and Sanger sequencing analysis of the family. (C) The effect of the missense variant in the CCIN gene.

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.

Globozoospermia: A Case Report and Systematic Review of Literature

PURPOSE

Globozoospermia is a genetic syndrome characterized by the presence of round-headed spermatozoa and infertility due to the inability of these spermatozoa to fertilize the oocyte. In this article, we present the clinical case of a young globozoospermic patient with a new, not yet described mutation of the DPY19L2 gene. We also performed a systematic review of the literature on gene mutations, the outcome of assisted reproductive techniques, and the risk of transmission of abnormalities to the offspring in patients with globozoospermia and made recommendations to offer a more appropriate clinical management of these patients.

MATERIALS AND METHODS

We performed a systematic search in the PubMed, Google Scholar, and Scopus databases from their inception to December 2021. The search strategy included the combination of the following Medical Subjects Headings (MeSH) terms and keywords: "globozoospermia", "round-headed spermatozoa", "round head spermatozoa", "intracytoplasmic sperm injection", "ICSI", "offspring", "child health", "assisted reproductive technique outcome". All the eligible studies were selected following the PECOS (Population, Exposure, Comparison/Comparator, Outcomes, Study design) model. The quality of included studies was assessed by applying the "Cambridge Quality Checklists".

RESULTS

The main genes involved in the pathogenesis of globozoospermia are DPY19L2, SPATA16, PICK1, GGN, SPACA1, ZPBP, CCDC62, and CCNB3 genes. Other genes could also play a role. These include C2CD6, C7orf61, CCIN, DNH17, DNH6, PIWIL4, and CHPT1. Globozoospermic patients should undergo ART to achieve fertility. In particular, intracytoplasmic sperm injection with assisted oocyte activation or intracytoplasmic morphologically-selected sperm injection appears to be associated with a higher success rate. Patients with globozoospermia should also be evaluated for the high rate of sperm aneuploidy which appears to influence the success rate of ART but does not appear to be associated with an increased risk of transmission of genetic abnormalities to offspring.

CONCLUSIONS

This systematic review summarizes the evidence on the gene panel to be evaluated, ICSI outcomes, and the health of the offspring in patients with globozoospermia. Evidence-based recommendations on the management of patients with globozoospermia are provided.

Multiomics analysis of male infertility

Infertility affects 8-12% of couples globally, and the male factor is a primary cause in approximately 50% of couples. Male infertility is a multifactorial reproductive disorder, which can be caused by paracrine and autocrine factors, hormones, genes, and epigenetic changes. Recent studies in rodents and most notably in humans using multiomics approach have yielded important insights into understanding the biology of spermatogenesis. Nonetheless, the etiology and pathogenesis of male infertility are still largely unknown. In this review, we summarized and critically evaluated findings based on the use of advanced technologies to compare normal and obstructive azoospermia (OA) versus non-obstructive azoospermia (NOA) men, including whole-genome bisulfite sequencing (WGBS), single cell RNA-seq (scRNA-seq), whole exome sequencing (WES), and ATAC-seq. It is obvious that the multiomics approach is the method of choice for basic research and clinical studies including clinical diagnosis of male infertility.

Awareness and reporting of globozoospermia among in vitro fertilization and andrology laboratories: A national survey

Globozoospermia (GZ) is a rare disorder found in less than 0.1% of infertile men in which spermatozoa lack acrosomes necessary for penetration of an oocyte. While methods have been demonstrated to allow globozoospermic men to achieve a viable pregnancy with their partner, the Wold Health Organization considers identifying and reporting GZ on semen analysis to be 'important'. Our study aims to determine if and to what extent in vitro fertilization (IVF) laboratories nationwide recognize and report GZ on semen analysis reports. We constructed an IRB-approved survey sent nationwide to IVF and andrology clinic laboratory directors listed by the Society for Assisted Reproductive Technology and/or the American Society for Reproductive Medicine. Results from the survey were de-identified for analysis. A total of 490 surveys were sent with a response rate of 10% (n = 51). Most respondents (66%) practiced in a private, rather than academic, setting. A majority of respondents were confident in their technicians' knowledge of GZ (86%) and ability to identify it on a sample (94%). However, only half of respondents noted a space to report the concern for GZ to the ordering physician, and 25% of respondents did not feel their clinic was able to identify patients where there is a concern for GZ. Similarly, 84% of respondents did not report a percent of acrosome-deficient sperm. Less than half of respondents reported that their clinic has previously diagnosed GZ. Though the majority of respondents felt that their laboratory technicians would be able to identify GZ, a significant minority felt that their clinic did not have means to be able to report concern for GZ. This may be due to the absence of a proper channel to report a concern for GZ, a lack of knowledge about the condition, or failure to distinguish GZ from a broader reported percentage of morphologically abnormal sperm. Given evidence that the diagnosis of GZ may be under-reported in the United States, there should be a national standard for laboratory technicians to be trained to recognize GZ and be able to report their suspicion to the ordering clinician.

Identification of a new splice-acceptor mutation in HFM1 and functional analysis through molecular docking in nonobstructive azoospermia

PURPOSE

To investigate the genetic cause of nonobstructive azoospermia (NOA).

METHODS

We performed whole exome sequencing (WES) on the proband who had three relatives suffering from NOA. We used a list of candidate genes which have high expression level in testis and their mutations have been reported in NOA. Sanger sequencing verified the identified variant and its structural and functional consequence was evaluated by protein three-dimensional (3D) structure prediction and protein-ligand docking.

RESULTS

WES revealed a novel splice-acceptor mutation (c.1832-2A>T) in helicase for meiosis 1 (HFM1) gene, which co-segregated with the NOA in this family. 3D structural models were generated and verified. Molecular docking indicated that the c.1832-2A>T mutation affects not only the ADP binding residues but also the hydrogen bond interactions. The ADP binding site will be lost in the mutant protein, potentially causing defective crossover and synapsis.

CONCLUSION

We report that the c.1832-2A>T mutation is the likely cause of NOA in the family studied. Regarding that many reported NOA genes are involved in the formation of crossovers and synapsis and have critical roles in the production of germ cells, we suggest that such genes should be considered for screening of infertility among large cohorts of infertile individuals.

Translational aspects of novel findings in genetics of male infertility-status quo 2021

INTRODUCTION

Male factor infertility concerns 7-10% of men and among these 40-60% remain unexplained.

SOURCES OF DATA

This review is based on recent published literature regarding the genetic causes of male infertility.

AREAS OF AGREEMENT

Screening for karyotype abnormalities, biallelic pathogenic variants in the CFTR gene and Y-chromosomal microdeletions have been routine in andrology practice for >20 years, explaining ~10% of infertility cases. Rare specific conditions, such as congenital hypogonadotropic hypogonadism, disorders of sex development and defects of sperm morphology and motility, are caused by pathogenic variants in recurrently affected genes, which facilitate high diagnostic yield (40-60%) of targeted gene panel-based testing.

AREAS OF CONTROVERSY

Progress in mapping monogenic causes of quantitative spermatogenic failure, the major form of male infertility, has been slower. No 'recurrently' mutated key gene has been identified and worldwide, a few hundred patients in total have been assigned a possible monogenic cause.

GROWING POINTS

Given the high genetic heterogeneity, an optimal approach to screen for heterogenous genetic causes of spermatogenic failure is sequencing exomes or in perspective, genomes. Clinical guidelines developed by multidisciplinary experts are needed for smooth integration of expanded molecular diagnostics in the routine management of infertile men.

AREAS TIMELY FOR DEVELOPING RESEARCH

Di-/oligogenic causes, structural and common variants implicated in multifactorial inheritance may explain the 'hidden' genetic factors. It is also critical to understand how the recently identified diverse genetic factors of infertility link to general male health concerns across lifespan and how the clinical assessment could benefit from this knowledge.

Whole-exome sequencing of a cohort of infertile men reveals novel causative genes in teratozoospermia that are chiefly related to sperm head defects

STUDY QUESTION

Can whole-exome sequencing (WES) and in vitro validation studies identify new causative genes associated with teratozoospermia, particularly for sperm head defect?

SUMMARY ANSWER

We investigated a core group of infertile patients, including 82 cases with unexplained abnormal sperm head and 67 individuals with multiple morphological abnormalities of the sperm flagella (MMAF), and revealed rare and novel deleterious gene variants correlated with morphological abnormalities of the sperm head or tail defects.

WHAT IS KNOWN ALREADY

Teratozoospermia is one of the most common factors causing male infertility. Owing to high phenotypic variability, currently known genetic causes of teratozoospermia can only explain a rather minor component for patients with anomalous sperm-head shapes, and the agents responsible for atypical sperm head shapes remain largely unknown.

STUDY DESIGN, SIZE, DURATION

We executed WES analysis of a Chinese cohort of patients (N = 149) with teratozoospermia to identify novel genetic causes particularly for defective sperm head. We also sought to reveal the influence of different abnormalities of sperm morphology on ICSI outcome.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In this study, a cohort of 149 infertile men (82 with abnormal sperm head and 67 with MMAF) were recruited. We implemented WES on infertile patients and analyzed the negative effects of the mutations of candidate genes on their protein conformations and/or expression. We also investigated the candidate genes' spatiotemporal expression/localization during spermatogenesis in both humans and mice, and explored their interactions with proteins that are known to be involved in sperm development. We also compared the ICSI outcomes of the affected individuals with various aberrations in sperm morphology.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified rare and deleterious variants of piwi like RNA-mediated gene silencing 4 (PIWIL4: 1/82 patients, 1.21%), coiled-coil and C2 domain containing 1B (CC2D1B: 1/82 patients, 1.21%), cyclin B3 (CCNB3: 1/82 patients, 1.21%), KIAA1210 (KIAA1210: 2/82 patients, 2.43%) and choline phosphotransferase 1 (CHPT1: 1/82 patients, 1.21%), which are novel correlates of morphological abnormalities of the sperm head; functional evidence supports roles for all of these genes in sperm head formation. The mutations of septin 12 (SEPTIN12: 2/82 patients, 2.43%) are suggested to be associated with acrosome defects. We additionally observed novel causative mutations of dynein axonemal heavy chain 2 (DNAH2: 1/67 patients, 1.49%), dynein axonemal heavy chain 10 (DNAH10: 1/67 patients, 1.49%) and dynein axonemal heavy chain 12 (DNAH12: 1/67 patients, 1.49%) in patients with MMAF, and revealed a significantly lower fertilization rate of the abnormal sperm-head group compared to the MMAF group following ICSI. Consequently, our study also suggests that the mutations of PIWIL4 and CC2D1B might be circumvented by ICSI to a degree, and that CHPT1 and KIAA1210 loss-of-function variants might be associated with failed ICSI treatment.

LIMITATIONS, REASONS FOR CAUTION

In this study, we discovered the relationship between the genotype and phenotype of the novel causative genes of sperm head deformities in humans. However, the molecular mechanism of the relevant genes involved in sperm head development needs to be further illuminated in future research. Furthermore, evidence should be provided using knockout/knock-in mouse models for additional confirmation of the roles of these novel genes in spermatogenesis.

WIDER IMPLICATIONS OF THE FINDINGS

This cohort study of 149 Chinese infertile men documents novel genetic factors involved in teratozoospermia, particularly in anomalous sperm head formation. For the first time, we suggest that SEPTIN12 is related to human acrosomal hypoplasia, and that CCNB3 is a novel causative gene for globozoospermia in humans. We also uncovered variants in two genes-KIAA1210 and CHPT1associated with acrosomal biogenesis in patients with small or absent acrosomes. Additionally, it is postulated that loss-of-function mutations of PIWIL4 and CC2D1B have a contribution to the abnormal sperm-head formation. Furthermore, we are first to demonstrate the influence of different sperm morphologies on ICSI outcomes and indicates that the abnormal sperm head may play a significant role in fertilization failure. Our findings therefore provide valuable information for the diagnosis of teratozoospermia, particularly with respect to abnormalities of the sperm head. This will allow clinicians to adopt the optimal treatment strategy and to develop personalized medicine directly targeting these effects.

STUDY FUNDING/COMPETING INTEREST(S)

This work was financed by the West China Second University Hospital of Sichuan University (KS369 and KL042). The authors declare that they do not have any conflicts of interests.

TRIAL REGISTRATION NUMBER

N/A.

FAM71F1 binds to RAB2A and RAB2B and is essential for acrosome formation and male fertility in mice

The acrosome is a cap-shaped, Golgi-derived membranous organelle that is located over the anterior of the sperm nucleus and highly conserved throughout evolution. Although morphological changes during acrosome biogenesis in spermatogenesis have been well described, the molecular mechanism underlying this process is still largely unknown. Family with sequence similarity 71, member F1 and F2 (FAM71F1 and FAM71F2) are testis-enriched proteins that contain a RAB2B-binding domain, a small GTPase involved in vesicle transport and membrane trafficking. Here, by generating mutant mice for each gene, we found that Fam71f1 is essential for male fertility. In Fam71f1-mutant mice, the acrosome was abnormally expanded at the round spermatid stage, likely because of enhanced vesicle trafficking. Mass spectrometry analysis after immunoprecipitation indicated that, in testes, FAM71F1 binds not only RAB2B, but also RAB2A. Further study suggested that FAM71F1 binds to the GTP-bound active form of RAB2A/B, but not the inactive form. These results indicate that a complex of FAM71F1 and active RAB2A/B suppresses excessive vesicle trafficking during acrosome formation.

Will whole-genome sequencing become the first-line genetic analysis for male infertility in the near future?

Whereas the initially strategy for the genetic analysis of male infertility was based on a candidate gene approach, the development of next-generation sequencing technologies (such as whole-exome sequencing (WES)) provides an opportunity to analyze many genes in a single procedure. In order to recommend WES or whole-genome sequencing (WGS) after genetic counselling, an objective evaluation of the current genetic screening strategy for male infertility is required, even if, at present, we have to take into consideration the complexity of such a procedure, not discussed in this commentary.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.

Towards Post-Meiotic Sperm Production: Genetic Insight into Human Infertility from Mouse Models

Declined quality and quantity of sperm is currently the major cause of patients suffering from infertility. Male germ cell development is spatiotemporally regulated throughout the whole developmental process. While it has been known that exogenous factors, such as environmental exposure, diet and lifestyle, et al, play causative roles in male infertility, recent progress has revealed abundant genetic mutations tightly associated with defective male germline development. In mammals, male germ cells undergo dramatic morphological change (i.e., nuclear condensation) and chromatin remodeling during post-meiotic haploid germline development, a process termed spermiogenesis; However, the molecular machinery players and functional mechanisms have yet to be identified. To date, accumulated evidence suggests that disruption in any step of haploid germline development is likely manifested as fertility issues with low sperm count, poor sperm motility, aberrant sperm morphology or combined. With the continually declined cost of next-generation sequencing and recent progress of CRISPR/Cas9 technology, growing studies have revealed a vast number of disease-causing genetic variants associated with spermiogenic defects in both mice and humans, along with mechanistic insights partially attained and validated through genetically engineered mouse models (GEMMs). In this review, we mainly summarize genes that are functional at post-meiotic stage. Identification and characterization of deleterious genetic variants should aid in our understanding of germline development, and thereby further improve the diagnosis and treatment of male infertility.

Bi-allelic mutation in Fsip1 impairs acrosome vesicle formation and attenuates flagellogenesis in mice

Fibrous sheath interacting protein 1 (Fsip1) is a cytoskeletal structural protein of the sperm flagellar proteome. A few studies have reported that it plays a vital role in the tumorigenesis and cancer progression. However, little is known about the role of Fsip1 in spermatogenesis and mammalian sperm flagellogenesis. Fsip1 protein showed the highest expression in round spermatids, and was translocated from nucleus to the anterior region of the elongating spermatid head. To investigate its role we constructed homozygous Fsip1 null (Fsip1^−/−) mice. We found that the homozygous Fsip1^−/− mutant mice were infertile, with a low sperm count and impaired motility. Interestingly, a subtle phenotype characterized by abnormal head shape, and flagella deformities was observed in the sperm of Fsip1^−/− mutant mice similar to the partial globozoospermia phenotype. Electron microscopy analysis of Fsip1^−/− sperm revealed abnormal accumulation of mitochondria, disrupted axoneme and retained cytoplasm. Testicular sections showed increased cytoplasmic vacuoles in the elongated spermatid of Fsip1^–/–mice, which indicated an intraflagellar transport (IFT) defect. Using proteomic approaches, we characterized the cellular components and the mechanism underlying this subtle phenotype. Our result indicated that Fsip1^–/–downregulates the formation of acrosomal membrane and vesicles proteins, intraflagellar transport particles B, and sperm flagellum components. Our results suggest that Fsip1 is essential for normal spermiogenesis, and plays an essential role in the acrosome biogenesis and flagellogenesis by attenuating intraflagellar transport proteins.

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Disruption of Fsip1 leads to infertility with partial globozoospermia phenotype.

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Homozygous deletion of Fsip1 alters spermiogenesis.

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Fsip1 Knockout disrupts acrosome vesicle formation.

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Fsip1 motif analysis involves in internal fertilization.

Deletion of the Spata3 Gene Induces Sperm Alterations and In Vitro Hypofertility in Mice

Thanks to the analysis of an Interspecific Recombinant Congenic Strain (IRCS), we previously defined the Mafq1 quantitative trait locus as an interval on mouse Chromosome 1 associated with male hypofertility and ultrastructural abnormalities. We identified the Spermatogenesis associated protein 3 gene (Spata3 or Tsarg1) as a pertinent candidate within the Mafq1 locus and performed the CRISPR-Cas9 mediated complete deletion of the gene to investigate its function. Male mice deleted for Spata3 were normally fertile in vivo but exhibited a drastic reduction of efficiency in in vitro fertilization assays. Mobility parameters were normal but ultrastructural analyses revealed acrosome defects and an overabundance of lipids droplets in cytoplasmic remnants. The deletion of the Spata3 gene reproduces therefore partially the phenotype of the hypofertile IRCS strain.