Whole-exome sequencing identifies mutations in FSIP2 as a recurrent cause of multiple morphological abnormalities of the sperm flagella

How exome sequencing improves the diagnostics and management of men with non-syndromic infertility

Male infertility affects approximately 17% of all men and represents a complex disorder in which not only semen parameters such as sperm motility, morphology, and number of sperm are highly variable, but also testicular phenotypes range from normal spermatogenesis to complete absence of germ cells. Genetic factors significantly contribute to the disease but chromosomal aberrations, mostly Klinefelter syndrome, and microdeletions of the Y-chromosome have remained the only diagnostically and clinically considered genetic causes. Monogenic causes remain understudied and, thus, often unidentified, leaving the majority of the male factor couple infertility pathomechanistically unexplained. This has been changing mostly because of the introduction of exome sequencing that allows the analysis of multiple genes in large patient cohorts. As a result, pathogenic variants in single genes have been associated with non-syndromic forms of all aetiologic sub-categories in the last decade. This review highlights the contribution of exome sequencing to the identification of novel disease genes for isolated (non-syndromic) male infertility by presenting the results of a comprehensive literature search. Both, reduced sperm count in azoospermic and oligozoospermic patients, and impaired sperm motility and/or morphology, in asthenozoospermic and/or teratozoospermic patients are highly heterogeneous diseases with well over 100 different candidate genes described for each entity. Applying the standardized evaluation criteria of the ClinGen gene curation working group, 70 genes with at least moderate evidence to contribute to the disease are highlighted. The implementation of these valid disease genes in clinical exome sequencing is important to increase the diagnostic yield in male infertility and, thus, improve clinical decision-making and appropriate genetic counseling. Future advances in androgenetics will continue to depend on large-scale exome and genome sequencing studies of comprehensive international patient cohorts, which are the most promising approaches to identify additional disease genes and provide reliable data on the gene-disease relationship.

Development of functional spermatozoa in mammalian spermiogenesis

Infertility is a global health problem affecting one in six couples, with 50% of cases attributed to male infertility. Spermatozoa are male gametes, specialized cells that can be divided into two parts: the head and the flagellum. The head contains a vesicle called the acrosome that undergoes exocytosis and the flagellum is a motility apparatus that propels the spermatozoa forward and can be divided into two components, axonemes and accessory structures. For spermatozoa to fertilize oocytes, the acrosome and flagellum must be formed correctly. In this Review, we describe comprehensively how functional spermatozoa develop in mammals during spermiogenesis, including the formation of acrosomes, axonemes and accessory structures by focusing on analyses of mouse models.

Structure and Composition of Spermatozoa Fibrous Sheath in Diverse Groups of Metazoa

The proper functioning and assembly of the sperm flagella structures contribute significantly to spermatozoa motility and overall male fertility. However, the fine mechanisms of assembly steps are poorly studied due to the high diversity of cell types, low solubility of the corresponding protein structures, and high tissue and cell specificity. One of the open questions for investigation is the attachment of longitudinal columns to the doublets 3 and 8 of axonemal microtubules through the outer dense fibers. A number of mutations affecting the assembly of flagella in model organisms are known. Additionally, evolutionary genomics data and comparative analysis of flagella morphology are available for a set of non-model species. This review is devoted to the analysis of diverse ultrastructures of sperm flagellum of Metazoa combined with an overview of the evolutionary distribution and function of the mammalian fibrous sheath proteins.

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.

Lack of CCDC146, a ubiquitous centriole and microtubule-associated protein, leads to non-syndromic male infertility in human and mouse

From a cohort of 167 infertile patients suffering from multiple morphological abnormalities of the flagellum (MMAF), pathogenic bi-allelic mutations were identified in the CCDC146 gene. In somatic cells, CCDC146 is located at the centrosome and at multiple microtubule-related organelles during mitotic division, suggesting that it is a microtubule-associated protein (MAP). To decipher the molecular pathogenesis of infertility associated with CCDC146 mutations, a Ccdc146 knock-out (KO) mouse line was created. KO male mice were infertile, and sperm exhibited a phenotype identical to CCDC146 mutated patients. CCDC146 expression starts during late spermiogenesis. In the spermatozoon, the protein is conserved but is not localized to centrioles, unlike in somatic cells, rather it is present in the axoneme at the level of microtubule doublets. Expansion microscopy associated with the use of the detergent sarkosyl to solubilize microtubule doublets suggests that the protein may be a microtubule inner protein (MIP). At the subcellular level, the absence of CCDC146 impacted all microtubule-based organelles such as the manchette, the head-tail coupling apparatus (HTCA), and the axoneme. Through this study, a new genetic cause of infertility and a new factor in the formation and/or structure of the sperm axoneme were characterized.

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.

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.

Nuclear sperm integrity and ICSI prognosis in Tunisian patients with MMAF syndrome (multiple morphological abnormalities of the sperm flagella)

Multiple Morphological Abnormalities of the Sperm Flagella (MMAF) is a severe form of teratozoospermia associated with several sperm flagellar abnormalities. The study included 52 patients with MMAF syndrome and a control group of 25 fertile men. The impact of nuclear sperm quality on intracytoplasmic sperm injection (ICSI) results was studied in 20 couples. TUNEL assay was used to assess sperm DNA fragmentation and aniline-blue staining was used to assess chromatin condensation. To investigate chromosomal meiotic segregation, we used fluorescence in situ hybridization (FISH). Semen morphology analysis revealed a mosaic of multiple flagella morphological abnormalities, including 46.73% short flagella, 16.22% bent flagella, 22.07% coiled flagella, and 10.90% absent flagella, all of which were associated with a high percentage of sperm head abnormalities. The mean DNA fragmentation index was substantially higher in patients compared to controls (p = 0.001), whereas the rate of aniline blue-reacted spermatozoa was not significantly different. There was a significant difference in aneuploidy frequencies between the two groups (p < 0.05). Infertile males with MMAF syndrome had lower sperm nuclear quality, which affected ICSI results. As a result, better sperm selection procedures are being employed to increase the success rate of assisted reproductive technologies (ART).

The human sperm proteome-Toward a panel for male fertility testing

BACKGROUND

Although male factor accounts for 40%-50% of unintended childlessness, we are far from fully understanding the detailed causes. Usually, affected men cannot even be provided with a molecular diagnosis.

OBJECTIVES

We aimed at a higher resolution of the human sperm proteome for better understanding of the molecular causes of male infertility. We were particularly interested in why reduced sperm count decreases fertility despite many normal-looking spermatozoa and which proteins might be involved.

MATERIAL AND METHODS

Applying mass spectrometry analysis, we qualitatively and quantitatively examined the proteomic profiles of spermatozoa from 76 men differing in fertility. Infertile men had abnormal semen parameters and were involuntarily childless. Fertile subjects exhibited normozoospermia and had fathered children without medical assistance.

RESULTS

We discovered proteins from about 7000 coding genes in the human sperm proteome. These were mainly known for involvements in cellular motility, response to stimuli, adhesion, and reproduction. Numbers of sperm proteins showing at least threefold deviating abundances increased from oligozoospermia (N = 153) and oligoasthenozoospermia (N = 154) to oligoasthenoteratozoospermia (N = 368). Deregulated sperm proteins primarily engaged in flagellar assembly and sperm motility, fertilization, and male gametogenesis. Most of these participated in a larger network of male infertility genes and proteins.

DISCUSSION

We expose 31 sperm proteins displaying deviant abundances under infertility, which already were known before to have fertility relevance, including ACTL9, CCIN, CFAP47, CFAP65, CFAP251 (WDR66), DNAH1, and SPEM1. We propose 18 additional sperm proteins with at least eightfold differential abundance for further testing of their diagnostic potential, such as C2orf16, CYLC1, SPATA31E1, SPATA31D1, SPATA48, EFHB (CFAP21), and FAM161A.

CONCLUSION

Our results shed light on the molecular background of the dysfunctionality of the fewer spermatozoa produced in oligozoospermia and syndromes including it. The male infertility network presented may prove useful in further elucidating the molecular mechanism 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.

Ovine fertility by artificial insemination in the breeding season could be affected by intraseasonal variations in ram sperm proteomic profile

It is important to note that seasonality could affect ram reproductive parameters, and therefore, fertility results after artificial insemination. In this work, 1) we assessed fertility rates after cervical artificial insemination of 11,805 ewes at the beginning (June 21st to July 20th) and at the end (November 20th to December 21st) of the reproductive season in the Assaf breed for the last four years, and 2) we aimed to identify male factors influencing the different reproductive success obtained depending on the time at the mating season in which ovine artificial insemination was performed. For this purpose, we evaluated certain ram reproductive and ultrasonographical parameters as well as we performed a multiparametric and proteomic sperm analysis of 6-19 rams at two very distant points in the mating season (July as Early Breeding Season -EBS- and November as Late Breeding Season -LBS-). Rutinary assessments carried out in the ovine reproduction centers (testicular volume, libido, sperm production and mass motility) showed non-significant differences (P ≥ 0.05) between both studied times, as well as the ram ultrasonographic evaluation (Resistive and Pulsatility Index as Doppler parameters; and pixels mean gray level, and hypoechoic areas percentage and density as echotexture parameters). However, at level of sperm functionality, although sperm quality appeared non-significantly lower (P ≥ 0.05) in the EBS, we identified a significantly different (P < 0.05) sperm proteomic profile between the seasonality points. The following proteins were identified with the lowest abundance in the EBS with a fold change > 4, a P = 2.40e-07, and a q = 2.23e-06: Fibrous Sheath-Interacting Protein 2, Disintegrin and Metalloproteinase Domain-Containing Protein 20-like, Phosphoinositide-Specific Phospholipase C, Tektin 5, Armadillo Repeat-Containing Protein 12 Isoform X3, Solute Carrier Family 9B1, Radial Spoke Head Protein 3 Homolog, Pro-Interleukin-16, NADH Dehydrogenase [Ubiquinone] 1 Alpha Subcomplex Subunit 8, Testis, Prostate and Placenta-Expressed Protein, and Acyl Carrier Protein Mitochondrial. In conclusion, while our basic analyses on male and sperm quality showed similar results between the beginning and the end of the breeding season, on a proteomic level we detected a lower expression of sperm proteins linked to the energy metabolism, sperm-oocyte interactions, and flagellum structure in the EBS. Probably, this different protein expression could be related to the lower fertility rate of Assaf ewes after cervical artificial insemination at this time. More importantly, sperm proteins can be used as highly effective molecular markers in predicting sperm fertilization ability related to intraseasonal variations.

A novel mutation in CFAP47 causes male infertility due to multiple morphological abnormalities of the sperm flagella

Introduction

A previous study suggested that loss of CFAP47 function is involved in multiple morphological abnormalities of the sperm flagella (MMAF) in humans and mice. However, the comprehensive role of CFAP47 in spermatogenesis is largely unknown.

Methods

Whole-exome sequencing (WES) was conducted to identify pathogenic variant in two patients with MMAF. The functional effect of the identified mutations was investigated by immunofluorescence staining and western blotting. Intracytoplasmic sperm injection (ICSI) was used to assist fertilization for the patient with MMAF.

Results

In this study, we identified a novel missense mutation (c.1414G>A; p.V472M) in CFAP47 in two unrelated patients with oligoasthenoteratozoospermia. Intriguingly, in addition to the MMAF phenotype very analogous to the previous report, the two patients notably presented abnormal morphology of sperm heads, the sperm mitochondrial sheath was obviously disorganized, and the sperm annulus were almost defective. Further functional experiments confirmed that the expression of CFAP47 was markedly reduced in the spermatozoa of the patients. Mechanism analysis suggested that CFAP47 might regulate the expression of CFAP65, CFAP69 and SEPTIN4 through their physical interactions and thus modulating sperm morphogenesis.

Conclusion

we revealed a novel mutation in CFAP47 and further expanded the phenotype and mutation spectrum of CFAP47, as well as the potential mechanism of CFAP47 manipulating spermatogenesis, finally providing important guidance for genetic counseling and targeted treatment for CFAP47 mutation-related male infertility.

Genomics of adaptive evolution in the woolly mammoth

Ancient genomes provide a tool to investigate the genetic basis of adaptations in extinct organisms. However, the identification of species-specific fixed genetic variants requires the analysis of genomes from multiple individuals. Moreover, the long-term scale of adaptive evolution coupled with the short-term nature of traditional time series data has made it difficult to assess when different adaptations evolved. Here, we analyze 23 woolly mammoth genomes, including one of the oldest known specimens at 700,000 years old, to identify fixed derived non-synonymous mutations unique to the species and to obtain estimates of when these mutations evolved. We find that at the time of its origin, the woolly mammoth had already acquired a broad spectrum of positively selected genes, including ones associated with hair and skin development, fat storage and metabolism, and immune system function. Our results also suggest that these phenotypes continued to evolve during the last 700,000 years, but through positive selection on different sets of genes. Finally, we also identify additional genes that underwent comparatively recent positive selection, including multiple genes related to skeletal morphology and body size, as well as one gene that may have contributed to the small ear size in Late Quaternary woolly mammoths.

Sperm Motility Annotated Genes: Are They Associated with Impaired Fecundity?

Sperm motility is a prerequisite for achieving pregnancy, and alterations in sperm motility, along with sperm count and morphology, are commonly observed in subfertile men. The aim of the study was to determine whether the expression level of genes annotated with the Gene Ontology (GO) term 'sperm motility' differed in sperm collected from healthy men and men diagnosed with oligoasthenozoospermia. Reverse transcription quantitative real-time PCR (RT-qPCR), quantitative mass spectrometry (LC-MS/MS), and enrichment analyses were used to validate a set of 132 genes in 198 men present at an infertility clinic. Out of the 132 studied sperm-motility-associated genes, 114 showed differentially expressed levels in oligoasthenozoospermic men compared to those of normozoospermic controls using an RT-qPCR analysis. Of these, 94 genes showed a significantly lower expression level, and 20 genes showed a significantly higher expression level. An MS analysis of sperm from an independent cohort of healthy and subfertile men identified 692 differentially expressed proteins, of which 512 were significantly lower and 180 were significantly higher in oligoasthenozoospermic men compared to those of the normozoospermic controls. Of the 58 gene products quantified with both techniques, 48 (82.75%) showed concordant regulation. Besides the sperm-motility-associated proteins, the unbiased proteomics approach uncovered several novel proteins whose expression levels were specifically altered in abnormal sperm samples. Among these deregulated proteins, there was a clear overrepresentation of annotation terms related to sperm integrity, the cytoskeleton, and energy-related metabolism, as well as human phenotypes related to spermatogenesis and sperm-related abnormalities. These findings suggest that many of these proteins may serve as diagnostic markers of male infertility. Our study reveals an extended number of sperm-motility-associated genes with altered expression levels in the sperm of men with oligoasthenozoospermia. These genes and/or proteins can be used in the future for better assessments of male factor infertility.

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.

Compound Heterozygous Mutations in FSIP2 Cause Morphological Abnormalities in Sperm Flagella Leading to Male Infertility

Multiple morphological abnormalities of sperm flagella (MMAF) indicate severe teratozoospermia. The fibrous sheath interacting protein 2 (FSIP2) plays an important role in the normal construction of the flagella. In this study, a novel compound heterozygous mutation site of FSIP2, involving c.272_275delinsAGGTTTTTATA (p.L92Vfster74) and c.16788_16791del (p.E5596fs), was identified using whole-exome sequencing in a 32-year-old male. Electron microscope images revealed thick sperm neck, scattered sperm mitochondria, and short sperm tail. In addition, FSIP2 could not be visualized in sperm cells via immunofluorescence staining. Moreover, we used a protein domain prediction tool to identify a potential FSIP2 functional domain (5901-6774), the corresponding deletion of which was responsible for the MMAF phenotype in the infertile man. Finally, we reviewed the literature on FSIP2 and found that FSIP2 mutations are relatively concentrated, with high-frequency mutation regions in exon 16 and exon 17 accounting for 50% (10/20) and 35% (7/20) of cases, respectively. In conclusion, FISP2 is a common pathogenic gene of MMAF, which may provide a rationale for genetic counseling in the next generation of patients with male infertility.

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.

Exome sequencing and functional analyses revealed CETN1 variants leads to impaired cell division and male fertility

Human spermatogenesis requires an orchestrated expression of numerous genes in various germ cell subtypes. Therefore, the genetic landscape of male infertility is highly complex. Known genetic factors alone account for at least 15% of male infertility. However, ~40% of infertile men remain undiagnosed and are classified as idiopathic infertile men. We performed exome sequencing in 47 idiopathic infertile men (discovery cohort), followed by replication study (40 variants in 33 genes) in 844 infertile men and 709 controls using Sequenom MassARRAY® based genotyping. We report 17 variants in twelve genes that comprise both previously reported (DNAH8, DNAH17, FISP2 and SPEF2) and novel candidate genes (BRDT, CETN1, CATSPERD, GMCL1, SPATA6, TSSK4, TSKS and ZNF318) for male infertility. The latter have a strong biological nexus to human spermatogenesis and their respective mouse knockouts are concordant with human phenotypes. One candidate gene CETN1, identified in this study, was sequenced in another independent cohort of 840 infertile and 689 fertile men. Further, CETN1 variants were functionally characterized using biophysical and cell biology approaches. We demonstrate that CETN1 variant- p.Met72Thr leads to multipolar cells, fragmented nuclei during mitosis leading to cell death and show significantly perturbed ciliary disassembly dynamics. Whereas CETN1-5' UTR variant; rs367716858 leads to loss of a methylation site and increased reporter gene expression in vitro. We report a total of eight novel candidate genes identified by exome sequencing, which may have diagnostic relevance and can contribute to improved diagnostic workup and clinical management of male infertility.

Diverse monogenic subforms of human spermatogenic failure

Non-obstructive azoospermia (NOA) is the most severe form of male infertility and typically incurable. Defining the genetic basis of NOA has proven challenging, and the most advanced classification of NOA subforms is not based on genetics, but simple description of testis histology. In this study, we exome-sequenced over 1000 clinically diagnosed NOA cases and identified a plausible recessive Mendelian cause in 20%. We find further support for 21 genes in a 2-stage burden test with 2072 cases and 11,587 fertile controls. The disrupted genes are primarily on the autosomes, enriched for undescribed human "knockouts", and, for the most part, have yet to be linked to a Mendelian trait. Integration with single-cell RNA sequencing data shows that azoospermia genes can be grouped into molecular subforms with synchronized expression patterns, and analogs of these subforms exist in mice. This analysis framework identifies groups of genes with known roles in spermatogenesis but also reveals unrecognized subforms, such as a set of genes expressed across mitotic divisions of differentiating spermatogonia. Our findings highlight NOA as an understudied Mendelian disorder and provide a conceptual structure for organizing the complex genetics of male infertility, which may provide a rational basis for disease classification.

Genomic features of mediastinal germ cell tumors: a narrative review

BACKGROUND AND OBJECTIVE

Germ cell tumors (GCTs) are uncommon malignancies generally originating from gonads. However, about 5% of GCTs arise outside the gonad (extragonadal), of which 80% develop from the mediastinum. While the prognosis of seminomas is not affected by the gonadal or extragonadal primary location, the prognosis of nonseminoma primary mediastinal GCTs (NS-PMGCTs) is poor, compared to its gonadal counterpart with an estimated 5-year overall survival of about 50%. The current treatments are sub-optimal to increase the cure rate of these rare GCTs. Therefore, molecular insights into these tumors would be valuable to develop novel therapies. The main objective of this review is to describe and dissect the genomic features associated with primary mediastinal GCTs (PMGCTs), highlighting the more frequent genomic alterations and their correlation with clinical outcomes.

METHODS

We conducted a narrative review of the English literature available in PubMed and Google Scholar between 1982 and 2021, including meta-analyses, systematic reviews, case series and case reports regarding the genomic and clinical features of PMGCTs. We analyzed the available data to describe the molecular characteristics of PMGCTs compared to testicular GCTs (TGCTs), highlighting the most relevant biological and prognostic factors.

KEY CONTENT AND FINDINGS

The high percentage of platinum resistance, the unique association with hematologic malignancies (HMs) and other malignancies, the higher prevalence of P53 mutations, and a distinct genomic landscape characterize this rare disease.

CONCLUSIONS

Although some studies have unveiled recurrent molecular alterations in PMGCTs, few are particularly suitable for targeted therapy. Due to the rarity of PMGCTs, data sharing and the creation of an international consortium would be helpful to have a better understanding of the molecular drivers of these tumors.

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.

LRRC46 Accumulates at the Midpiece of Sperm Flagella and Is Essential for Spermiogenesis and Male Fertility in Mouse

The sperm flagellum is essential for male fertility. Multiple morphological abnormalities of the sperm flagella (MMAF) is a severe form of asthenoteratozoospermia. MMAF phenotypes are understood to result from pathogenic variants of genes from multiple families including AKAP, DANI, DNAH, RSPH, CCDC, CFAP, TTC, and LRRC, among others. The Leucine-rich repeat protein (LRRC) family includes two members reported to cause MMAF phenotypes: Lrrc6 and Lrrc50. Despite vigorous research towards understanding the pathogenesis of MMAF-related diseases, many genes remain unknown underlying the flagellum biogenesis. Here, we found that Leucine-rich repeat containing 46 (LRRC46) is specifically expressed in the testes of adult mice, and show that LRRC46 is essential for sperm flagellum biogenesis. Both scanning electron microscopy (SEM) and Papanicolaou staining (PS) presents that the knockout of Lrrc46 in mice resulted in typical MMAF phenotypes, including sperm with short, coiled, and irregular flagella. The male KO mice had reduced total sperm counts, impaired sperm motility, and were completely infertile. No reproductive phenotypes were detected in Lrrc46-/- female mice. Immunofluorescence (IF) assays showed that LRRC46 was present throughout the entire flagella of control sperm, albeit with evident concentration at the mid-piece. Transmission electron microscopy (TEM) demonstrated striking flagellar defects with axonemal and mitochondrial sheath malformations. About the important part of the Materials and Methods, SEM and PS were used to observe the typical MMAF-related irregular flagella morphological phenotypes, TEM was used to further inspect the sperm flagellum defects in ultrastructure, and IF was chosen to confirm the location of protein. Our study suggests that LRRC46 is an essential protein for sperm flagellum biogenesis, and its mutations might be associated with MMAF that causes male infertility. Thus, our study provides insights for understanding developmental processes underlying sperm flagellum formation and contribute to further observe the pathogenic genes that cause male infertility.

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.

Homozygous Loss of Septin12, but not its Haploinsufficiency, Leads to Male Infertility and Fertilization Failure

The SEPTIN12 gene has been associated with male infertility. Male Septin12^+/− chimera mice were infertile, supporting the prevailing view that SEPTIN12 haploinsufficiency causes male infertility. In this study, we identified a heterozygous mutation on SEPTIN12, c.72C>A (p.Cys24Ter) in the male partner of a patient couple, who had a previous fertilization failure (FF) after intracytoplasmic sperm injection (ICSI) and became pregnant after ICSI together with artificial oocyte activation (AOA). To investigate the role of SEPTIN12 in FF and oocyte activation, we constructed Septin12 knockout mice. Surprisingly, Septin12^−/− male mice, but not Septin12^+/− male mice, are infertile, and have reduced sperm counts and abnormal sperm morphology. Importantly, AOA treatment enhances the 2-cell embryo rate of ICSI embryos injected with Septin12^−/− sperm, indicating that FF caused by male Septin12 deficiency is overcome by AOA. Mechanistically, loss of PLCζ around the acrosome might be the reason for FF of Septin12^−/− sperm. Taken together, our data indicated that homozygous knockout of Septin12, but not Septin12 haploinsufficiency, leads to male infertility and FF.

Whole-exome sequencing and functional validation reveals a rare missense variant in MMP7 confers ovarian endometriosis risk

Prior studies have shown that genetic factors play important roles in ovarian endometriosis. Herein, we first analyzed the WES data from 158 patients with ovarian endometriosis and 385 local control women without endometriosis. Among which, a rare missense variant in the MMP7 (p.I79T, rs150338402) gene exhibited significant frequency difference. This rare variant was screened in an additional 1176 patients and 600 control women via direct DNA sequencing. Meanwhile, a total of 38 available clinical characteristics were collected. Our results showed 45 out of 1334 (3.37%) patients, while 15 out of 985 control women (1.52%) (P = 0.0076) harbored this rare variant, respectively. This rare variant was associated with clinical features such as follicle stimulating hormone (FSH, Padj = 0.0342), luteinizing hormone (LH, Padj = 0.0038), progesterone (PROG, Padj = 1.4e-7), testosterone (TESTO, Padj = 0.0923), total bilirubin (TBIL, Padj = 0.0699), carcinoembryonic antigen (CEA, Padj = 0.0665), and squamous cell carcinoma antigen (SCC, Padj = 0.0817), respectively. Functional assays showed this rare variant could promote cell migration, invasion, epithelial-mesenchymal transition (EMT), and increase the proteolytic protein activity of MMP7, implicating that the increased capacities of cell invasion, migration, and EMT might be mediated by enhanced proteolytic activity of MMP7 mutant. These results showed the MMP7 rare missense variant (p.I79T) played important roles in the pathogenesis of ovarian endometriosis. In conclusion, we identified for the first time, a significantly enriched MMP7 rare variant in ovarian endometriosis; this rare variant was closely associated with certain clinical features in ovarian endometriosis, thus, it could be a promising early diagnostic biomarker for this disease.

Mitochondrial regulation during male germ cell development

Mitochondria tailor their morphology to execute their specialized functions in different cell types and/or different environments. During spermatogenesis, mitochondria undergo continuous morphological and distributional changes with germ cell development. Deficiencies in these processes lead to mitochondrial dysfunction and abnormal spermatogenesis, thereby causing male infertility. In recent years, mitochondria have attracted considerable attention because of their unique role in the regulation of piRNA biogenesis in male germ cells. In this review, we describe the varied characters of mitochondria and focus on key mitochondrial factors that play pivotal roles in the regulation of spermatogenesis, from primordial germ cells to spermatozoa, especially concerning metabolic shift, stemness and reprogramming, mitochondrial transformation and rearrangement, and mitochondrial defects in human sperm. Further, we discuss the molecular mechanisms underlying these processes.

Successful outcomes of intracytoplasmic sperm injection-embryo transfer using ejaculated spermatozoa from two Chinese asthenoteratozoospermic brothers with a compound heterozygous FSIP2 mutation

Multiple morphological abnormalities of the sperm flagella (MMAF) is a characteristic form of severe asthenozoospermia and closely related to male infertility. However, it is not sure whether intracytoplasmic sperm injection (ICSI) allows MMAF patients reproductive success. The present study reported the first case of successful intracytoplasmic sperm injection-embryo transfer (ICSI-ET) in Chinese brothers with a novel compound heterozygous mutation of FSIP2 (fibrous sheath interacting protein 2), a newly identified MMAF-related genes. The proband and his brother were referred for MMAF because of their abnormal sperm flagellum. Through whole-exome sequencing in the genetic analyses of the proband, his brother and parents showed that the proband and his brother carry a novel compound heterozygous FSIP2 mutation (c.1750T>A and c.13600A>G), which will lead to abnormal expression of FSIP2 and loss of its function. Considering that these brothers had the MMAF phenotype, we recommended ICSI treatment. The successful outcome of ICSI indicated that a lose-function mutation of FSIP2 might not have any effect on ICSI, although the latest report showed a failed outcome of ICSI in a patient with FSIP2 mutation. This study provides new knowledge to understand the effect of MMAF caused by FSIP2 mutation on ICSI outcome.

CFAP61 is required for sperm flagellum formation and male fertility in human and mouse

Defects in the structure or motility of cilia and flagella may lead to severe diseases such as primary ciliary dyskinesia (PCD), a multisystemic disorder with heterogeneous manifestations affecting primarily respiratory and reproductive functions. We report that CFAP61 is a conserved component of the calmodulin- and radial spoke-associated complex (CSC) of cilia. We find that a CFAP61 splice variant, c.143+5G>A, causes exon skipping/intron retention in human, inducing a multiple morphological abnormalities of the flagella (MMAF) phenotype. We generated Cfap61 knockout mice that recapitulate the infertility phenotype of the human CFAP61 mutation, but without other symptoms usually observed in PCD. We find that CFAP61 interacts with the CSC, radial spoke stalk and head. During early stages of Cfap61-/- spermatid development, the assembly of radial spoke components is impaired. As spermiogenesis progresses, the axoneme in Cfap61-/- cells becomes unstable and scatters, and the distribution of intraflagellar transport proteins is disrupted. This study reveals an organ-specific mechanism of axoneme stabilization that is related to male infertility.

Bi-allelic variants in human WDR63 cause male infertility via abnormal inner dynein arms assembly

Inner dynein arm (IDA), composed of a series of protein complex, is necessary to cilia and flagella bend formation and beating. Previous studies indicated that defects of IDA protein complex result in multiple morphological abnormalities of the sperm flagellum (MMAF) and male infertility. However, the genetic causes and molecular mechanisms in the IDAs need further exploration. Here we identified two loss-of-function variants of WDR63 in both MMAF and non-obstructive azoospermia (NOA) affected cohorts. WDR63 encodes an IDA-associated protein that is dominantly expressed in testis. We next generated Wdr63-knockout (Wdr63-KO) mice through the CRISPR-Cas9 technology. Remarkably, Wdr63-KO induced decreased sperm number, abnormal flagellar morphology and male infertility. In addition, transmission electron microscopy assay showed severely disorganized "9 + 2" axoneme and absent inner dynein arms in the spermatozoa from Wdr63-KO male mice. Mechanistically, we found that WDR63 interacted with WDR78 mainly via WD40-repeat domain and is necessary for IDA assembly. Furthermore, WDR63-associated male infertility in human and mice could be overcome by intracytoplasmic sperm injection (ICSI) treatment. In conclusion, the present study demonstrates that bi-allelic variants of WDR63 cause male infertility via abnormal inner dynein arms assembly and flagella formation and can be used as a genetic diagnostic indicator for infertility males.

Genetic diagnosis, sperm phenotype and ICSI outcome in case of severe asthenozoospermia with multiple morphological abnormalities of the flagellum

STUDY QUESTION

Are ICSI outcomes impaired in cases of severe asthenozoospermia with multiple morphological abnormalities of the flagellum (MMAF phenotype)?

SUMMARY ANSWER

Despite occasional technical difficulties, ICSI outcomes for couples with MMAF do not differ from those of other couples requiring ICSI, irrespective of the genetic defect.

WHAT IS KNOWN ALREADY

Severe asthenozoospermia, especially when associated with the MMAF phenotype, results in male infertility. Recent findings have confirmed that a genetic aetiology is frequently responsible for this phenotype. In such situations, pregnancies can be achieved using ICSI. However, few studies to date have provided detailed analyses regarding the flagellar ultrastructural defects underlying this phenotype, its genetic aetiologies, and the results of ICSI in such cases of male infertility.

STUDY DESIGN, SIZE, DURATION

We performed a retrospective study of 25 infertile men exhibiting severe asthenozoospermia associated with the MMAF phenotype identified through standard semen analysis. They were recruited at an academic centre for assisted reproduction in Paris (France) between 2009 and 2017. Transmission electron microscopy (TEM) and whole exome sequencing (WES) were performed in order to determine the sperm ultrastructural phenotype and the causal mutations, respectively. Finally 20 couples with MMAF were treated by assisted reproductive technologies based on ICSI.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients with MMAF were recruited based on reduced sperm progressive motility and increased frequencies of absent, short, coiled or irregular flagella compared with those in sperm from fertile control men. A quantitative analysis of the several ultrastructural defects was performed for the MMAF patients and for fertile men. The ICSI results obtained for 20 couples with MMAF were compared to those of 378 men with oligoasthenoteratozoospermia but no MMAF as an ICSI control group.

MAIN RESULTS AND THE ROLE OF CHANCE

TEM analysis and categorisation of the flagellar anomalies found in these patients provided important information regarding the structural defects underlying asthenozoospermia and sperm tail abnormalities. In particular, the absence of the central pair of axonemal microtubules was the predominant anomaly observed more frequently than in control sperm (P < 0.01). Exome sequencing, performed for 24 of the 25 patients, identified homozygous or compound heterozygous pathogenic mutations in CFAP43, CFAP44, CFAP69, DNAH1, DNAH8, AK7, TTC29 and MAATS1 in 13 patients (54.2%) (11 affecting MMAF genes and 2 affecting primary ciliary dyskinesia (PCD)-associated genes). A total of 40 ICSI cycles were undertaken for 20 MMAF couples, including 13 cycles (for 5 couples) where a hypo-osmotic swelling (HOS) test was required due to absolute asthenozoospermia. The fertilisation rate was not statistically different between the MMAF (65.7%) and the non-MMAF (66.0%) couples and it did not differ according to the genotype or the flagellar phenotype of the subjects or use of the HOS test. The clinical pregnancy rate per embryo transfer did not differ significantly between the MMAF (23.3%) and the non-MMAF (37.1%) groups. To date, 7 of the 20 MMAF couples have achieved a live birth from the ICSI attempts, with 11 babies born without any birth defects.

LIMITATIONS, REASONS FOR CAUTION

The ICSI procedure outcomes were assessed retrospectively on a small number of affected subjects and should be confirmed on a larger cohort. Moreover, TEM analysis could not be performed for all patients due to low sperm concentrations, and WES results are not yet available for all of the included men.

WIDER IMPLICATIONS OF THE FINDINGS

An early and extensive phenotypic and genetic investigation should be considered for all men requiring ICSI for severe asthenozoospermia. Although our study did not reveal any adverse ICSI outcomes associated with MMAF, we cannot rule out that some rare genetic causes could result in low fertilisation or pregnancy rates.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used for this study and there are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

A novel stop-gain mutation in ARMC2 is associated with multiple morphological abnormalities of the sperm flagella

RESEARCH QUESTION

Male infertility is a global issue worldwide and multiple morphological abnormalities of the sperm flagella (MMAF) is one of the most severe forms of the qualitative sperm defects with a heterogeneous genetic cause that has not been completely understood. Can whole-exome sequencing (WES) reveal novel genetic causes contributing to MMAF in a consanguineous Pakistani family, comprising three infertile brothers?

DESIGN

WES and bioinformatic analysis were conducted to screen potential pathogenic variants. The identified variant was validated by Sanger sequencing in all available family members Transmission electron microscopy analyses was carried out to examine the flagella ultrastructure of spermatozoa from patient.

RESULTS

WES and Sanger sequencing identified a novel homozygous stop-gain mutation (ENST00000392644.4, c.182C>G, p.S61X) in ARMC2, which is expected to lead to loss of protein functions. Transmission electron microscopy analyses revealed that the flagellar ultrastructure of the patient's spermatozoa was disorganized along with a complete absence of central pair complex (CPC), suggesting that ARMC2 is involved in the assembly, stability of the axonemal complex, or both, particularly the CPC.

CONCLUSION

We report that a familial stop-gain mutation in ARMC2 is associated with male infertility in humans caused by MMAF accompanied with loss of CPCs and axonemal disorganization. We provide genetic evidence that ARMC2 is essential for human spermatogenesis and its mutation may be pathogenic for MMAF. These findings will improve the knowledge about the genetic basis of MMAF and provide information for genetic counselling of this disease.

Diagnostics and Management of Male Infertility in Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD), a disease caused by the malfunction of motile cilia, manifests mainly with chronic recurrent respiratory infections. In men, PCD is also often associated with infertility due to immotile sperm. Since causative mutations for PCD were identified in over 50 genes, the role of these genes in sperm development should be investigated in order to understand the effect of PCD mutations on male fertility. Previous studies showed that different dynein arm heavy chains are present in respiratory cilia and sperm flagellum, which may partially explain the variable effects of mutations on airways and fertility. Furthermore, recent studies showed that male reproductive tract motile cilia may play an important part in sperm maturation and transport. In some PCD patients, extremely low sperm counts were reported, which may be due to motile cilia dysfunction in the reproductive tract rather than problems with sperm development. However, the exact roles of PCD genes in male fertility require additional studies, as do the treatment options. In this review, we discuss the diagnostic and treatment options for men with PCD based on the current knowledge.

Protein Identification of Spermatozoa and Seminal Plasma in Bottlenose Dolphin (Tursiops truncatus)

Proteins play an important role in many reproductive functions such as sperm maturation, sperm transit in the female genital tract or sperm-oocyte interaction. However, in general, little information concerning reproductive features is available in the case of aquatic animals. The present study aims to characterize the proteome of both spermatozoa and seminal plasma of bottlenose dolphins (Tursiops truncatus) as a model organism for cetaceans. Ejaculate samples were obtained from two trained dolphins housed in an aquarium. Spermatozoa and seminal plasma were analyzed by means of proteomic analyses using an LC-MS/MS, and a list with the gene symbols corresponding to each protein was submitted to the DAVID database. Of the 419 proteins identified in spermatozoa and 303 in seminal plasma, 111 proteins were shared by both. Furthermore, 70 proteins were identified as involved in reproductive processes, 39 in spermatozoa, and 31 in seminal plasma. The five most abundant proteins were also identified in these samples: AKAP3, ODF2, TUBB, GSTM3, ROPN1 for spermatozoa and CST11, LTF, ALB, HSP90B1, PIGR for seminal plasma. In conclusion, this study provides the first characterization of the proteome in cetacean sperm and seminal plasma, opening the way to future research into new biomarkers, the analysis of conservation capacity or possible additional applications in the field of assisted reproductive technologies.

Loss of DRC1 function leads to multiple morphological abnormalities of the sperm flagella and male infertility in human and mouse

Motile cilia and flagellar defects can result in primary ciliary dyskinesia, which is a multisystemic genetic disorder that affects roughly 1:10 000 individuals. The nexin-dynein regulatory complex (N-DRC) links neighboring doublet microtubules within flagella, serving as a central regulatory hub for motility in Chlamydomonas. Herein, we identified two homozygous DRC1 variants in human patients that were associated with multiple morphological abnormalities of the sperm flagella (MMAF) and male infertility. Drc1^−/−, Drc1^R554X/R554X and Drc1^W244X/W244X mice on the C57BL/6 background suffered from pre-pubertal mortality. However, when the ICR background was introduced, some of these mice were able to survive and recapitulate the MMAF phenotypes detected in human patients. By analyzing these animals, we determined that DRC1 is an essential regulator of N-DRC assembly in cilia and flagella. When DRC1 is absent, this results in the shortening of cilia and consequent impairment of their motility. Damage associated with DRC1 deficiency in sperm flagella was more pronounced than in cilia, as manifested by complete axoneme structural disorder in addition to the loss of the DRC structure. Altogether, these findings suggest that DRC1 is required for the structural stability of flagella but not cilia, emphasizing the key role of this protein in mammalian species.

Insight on multiple morphological abnormalities of sperm flagella in male infertility: what is new?

The syndrome of multiple morphological abnormalities of the sperm flagella (MMAF) is a specific kind of asthenoteratozoospermia with a mosaic of flagellar morphological abnormalities (absent, short, bent, coiled, and irregular flagella). MMAF was proposed in 2014 and has attracted increasing attention; however, it has not been clearly understood. In this review, we elucidate the definition of MMAF from a systematical view, the difference between MMAF and other conditions with asthenoteratozoospermia or asthenozoospermia (such as primary mitochondrial sheath defects and primary ciliary dyskinesia), the knowledge regarding its etiological mechanism and related genetic findings, and the clinical significance of MMAF for intracytoplasmic sperm injection and genetic counseling. This review provides the basic knowledge for MMAF and puts forward some suggestions for further investigations.

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.

Hypomorphic and hypermorphic mouse models of Fsip2 indicate its dosage-dependent roles in sperm tail and acrosome formation

Loss-of-function mutations in multiple morphological abnormalities of the sperm flagella (MMAF)-associated genes lead to decreased sperm motility and impaired male fertility. As an MMAF gene, the function of fibrous sheath-interacting protein 2 (FSIP2) remains largely unknown. In this work, we identified a homozygous truncating mutation of FSIP2 in an infertile patient. Accordingly, we constructed a knock-in (KI) mouse model with this mutation. In parallel, we established an Fsip2 overexpression (OE) mouse model. Remarkably, KI mice presented with the typical MMAF phenotype, whereas OE mice showed no gross anomaly except for sperm tails with increased length. Single-cell RNA sequencing of the testes uncovered altered expression of genes related to sperm flagellum, acrosomal vesicle and spermatid development. We confirmed the expression of Fsip2 at the acrosome and the physical interaction of this gene with Acrv1, an acrosomal marker. Proteomic analysis of the testes revealed changes in proteins sited at the fibrous sheath, mitochondrial sheath and acrosomal vesicle. We also pinpointed the crucial motifs of Fsip2 that are evolutionarily conserved in species with internal fertilization. Thus, this work reveals the dosage-dependent roles of Fsip2 in sperm tail and acrosome formation.

Whole-Exome Sequencing Analysis of Human Semen Quality in Russian Multiethnic Population

The global trend toward the reduction of human spermatogenic function observed in many countries, including Russia, raised the problem of extensive screening and monitoring of male fertility and elucidation of its genetic and ethnic mechanisms. Recently, whole-exome sequencing (WES) was developed as a powerful tool for genetic analysis of complex traits. We present here the first Russian WES study for identification of new genes associated with semen quality. The experimental 3 × 2 design of the WES study was based on the analysis of 157 samples including three ethnic groups—Slavs (59), Buryats (n = 49), and Yakuts (n = 49), and two different semen quality groups—pathozoospermia (n = 95) and normospermia (n = 62). Additionally, our WES study group was negative for complete AZF microdeletions of the Y-chromosome. The normospermia group included men with normal sperm parameters in accordance with the WHO-recommended reference limit. The pathozoospermia group included men with impaired semen quality, namely, with any combined parameters of sperm concentration <15 × 10⁶/ml, and/or progressive motility <32%, and/or normal morphology <4%. The WES was performed for all 157 samples. Subsequent calling and filtering of variants were carried out according to the GATK Best Practices recommendations. On the genotyping stage, the samples were combined into four cohorts: three sets corresponded to three ethnic groups, and the fourth set contained all the 157 whole-exome samples. Association of the obtained polymorphisms with semen quality parameters was investigated using the χ2 test. To prioritize the obtained variants associated with pathozoospermia, their effects were determined using Ensembl Variant Effect Predictor. Moreover, polymorphisms located in genes expressed in the testis were revealed based on the genomic annotation. As a result, the nine potential SNP markers rs6971091, rs557806, rs610308, rs556052, rs1289658, rs278981, rs1129172, rs12268007, and rs17228441 were selected for subsequent verification on our previously collected population sample (about 1,500 males). The selected variants located in seven genes FAM71F1, PPP1R15A, TRIM45, PRAME, RBM47, WDFY4, and FSIP2 that are expressed in the testis and play an important role in cell proliferation, meiosis, and apoptosis.

Exome sequencing reveals variants in known and novel candidate genes for severe sperm motility disorders

STUDY QUESTION

What are the causative genetic variants in patients with male infertility due to severe sperm motility disorders?

SUMMARY ANSWER

We identified high confidence disease-causing variants in multiple genes previously associated with severe sperm motility disorders in 10 out of 21 patients (48%) and variants in novel candidate genes in seven additional patients (33%).

WHAT IS KNOWN ALREADY

Severe sperm motility disorders are a form of male infertility characterised by immotile sperm often in combination with a spectrum of structural abnormalities of the sperm flagellum that do not affect viability. Currently, depending on the clinical sub-categorisation, up to 50% of causality in patients with severe sperm motility disorders can be explained by pathogenic variants in at least 22 genes.

STUDY DESIGN, SIZE, DURATION

We performed exome sequencing in 21 patients with severe sperm motility disorders from two different clinics.

PARTICIPANTS/MATERIALS, SETTING, METHOD

Two groups of infertile men, one from Argentina (n = 9) and one from Australia (n = 12), with clinically defined severe sperm motility disorders (motility <5%) and normal morphology values of 0–4%, were included. All patients in the Argentine cohort were diagnosed with DFS-MMAF, based on light and transmission electron microscopy. Sperm ultrastructural information was not available for the Australian cohort. Exome sequencing was performed in all 21 patients and variants with an allele frequency of <1% in the gnomAD population were prioritised and interpreted.

MAIN RESULTS AND ROLE OF CHANCE

In 10 of 21 patients (48%), we identified pathogenic variants in known sperm assembly genes: CFAP43 (3 patients); CFAP44 (2 patients), CFAP58 (1 patient), QRICH2 (2 patients), DNAH1 (1 patient) and DNAH6 (1 patient). The diagnostic rate did not differ markedly between the Argentinian and the Australian cohort (55% and 42%, respectively). Furthermore, we identified patients with variants in the novel human candidate sperm motility genes: DNAH12, DRC1, MDC1, PACRG, SSPL2C and TPTE2. One patient presented with variants in four candidate genes and it remains unclear which variants were responsible for the severe sperm motility defect in this patient.

LARGE SCALE DATA

N/A

LIMITATIONS, REASONS FOR CAUTION

In this study, we described patients with either a homozygous or two heterozygous candidate pathogenic variants in genes linked to sperm motility disorders. Due to unavailability of parental DNA, we have not assessed the frequency of de novo or maternally inherited dominant variants and could not determine the parental origin of the mutations to establish in all cases that the mutations are present on both alleles.

WIDER IMPLICATIONS OF THE FINDINGS

Our results confirm the likely causal role of variants in six known genes for sperm motility and we demonstrate that exome sequencing is an effective method to diagnose patients with severe sperm motility disorders (10/21 diagnosed; 48%). Furthermore, our analysis revealed six novel candidate genes for severe sperm motility disorders. Genome-wide sequencing of additional patient cohorts and re-analysis of exome data of currently unsolved cases may reveal additional variants in these novel candidate genes.

STUDY FUNDING/COMPETING INTEREST(S)

This project was supported in part by funding from the Australian National Health and Medical Research Council (APP1120356) to M.K.O.B., J.A.V. and R.I.M.L., The Netherlands Organisation for Scientific Research (918-15-667) to J.A.V., the Royal Society and Wolfson Foundation (WM160091) to J.A.V., as well as an Investigator Award in Science from the Wellcome Trust (209451) to J.A.V. and Grants from the National Research Council of Argentina (PIP 0900 and 4584) and ANPCyT (PICT 9591) to H.E.C. and a UUKi Rutherford Fund Fellowship awarded to B.J.H.

Essential Role of CFAP53 in Sperm Flagellum Biogenesis

The sperm flagellum is essential for male fertility. Despite vigorous research progress toward understanding the pathogenesis of flagellum-related diseases, much remains unknown about the mechanisms underlying the flagellum biogenesis itself. Here, we show that the cilia and flagella associated protein 53 (Cfap53) gene is predominantly expressed in testes, and it is essential for sperm flagellum biogenesis. The knockout of this gene resulted in complete infertility in male mice but not in the females. CFAP53 localized to the manchette and sperm tail during spermiogenesis, the knockout of this gene impaired flagellum biogenesis. Furthermore, we identified two manchette and sperm tail-associated proteins that interacted with CFAP53 during spermiogenesis. Together, our results suggest that CFAP53 is an essential protein for sperm flagellum biogenesis, and its mutations might be associated with multiple morphological abnormalities of the flagella (MMAF).

Association Between FSIP2 Mutation and an Improved Efficacy of Immune Checkpoint Inhibitors in Patients With Skin Cutaneous Melanoma

Background

Immune checkpoint inhibitors (ICIs) have shown remarkable success in treating skin cutaneous melanoma (SKCM); however, the response to treatment varies greatly between patients. Considering that the efficacy of ICI treatment is influenced by many factors, we selected the Fibrosheath interacting protein 2 (FSIP2) gene and systematically analyzed its potential to predict the efficacy of ICI treatment.

Methods

Patient data were collected from an ICI treatment cohort (n = 120) and a The Cancer Genome Atlas (TCGA)-SKCM cohort (n = 467). The data were divided into an FSIP2-mutant (MT) group and FSIP2-wild-type (WT) group according to FSIP2 mutation status. In this study, we analyzed the patients' overall survival rate, tumor mutational burden (TMB), neoantigen load (NAL), copy number variation (CNV), cell infiltration data and immune-related genes. We used gene set enrichment analysis (GSEA) to delineate biological pathways and processes associated with the efficacy of immunotherapy.

Results

The efficacy of ICI treatment of SKCM patients with FSIP2 mutation was significantly better than that of patients without FSIP2 mutation. The patients in the FSIP2-MT group had higher tumor immunogenicity and lower regulatory T cell (Treg) infiltration. Results of GSEA showed that pathways related to tumor progression (MAPK and FGFR), immunomodulation, and IL-2 synthesis inhibition were significantly downregulated in the FSIP2-MT group.

Conclusion

Our research suggests that the FSIP2 gene has the potential to predict the efficacy of ICI treatment. The high tumor immunogenicity and low Treg levels observed may be closely related to the fact that patients with FSIP2-MT can benefit from ICI treatment.

Novel bi-allelic mutations in DNAH1 cause multiple morphological abnormalities of the sperm flagella resulting in male infertility

Background

Male infertility is a major health concern and approximately 10–15% of cases are caused by genetic abnormalities. Defects in the sperm flagella are closely related to male infertility, since flagellar beating allows sperm to swim. The sperm of males afflicted with multiple morphological abnormalities of the flagella (MMAF) possess severe defects of the sperm flagella, may impair sperm motility and lead to male infertility. Currently, known genetic defects only account for MMAF in about 60% of patients and need more intensive efforts to explore the relationship between genes and MMAF.

Methods

The whole-exome sequencing (WES) was performed to analyze the genetic cause of the MMAF patient. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the morphology of sperm cells and to identify the ultrastructural characteristics of the flagella in the patient. The expression of DNAH1 was analyzed by sperm immunofluorescence staining.

Results

We identified the negative effects produced by the DNAH1 mutations c. 8170.C>T (p. R2724*) and c. 4670C>T (p. T1557M) on DNAH1 expression and the development of sperm flagella.

Conclusions

Our findings suggest that DNAH1 is associated with the formation of sperm flagella and homozygous loss-of-function mutations in DNAH1 can impair sperm motility and cause male infertility.

Mutations in DNAH8 contribute to multiple morphological abnormalities of sperm flagella and male infertility

Asthenoteratospermia is an important cause of male infertility. Here, we report two infertile patients with severe asthenoteratospermia accompanied by new genetic abnormality. Whole-exome sequencing and bioinformatics analysis suggested that compound heterozygous mutations in DNAH8 (MIM:603337) may be responsible for multiple morphological abnormalities of the sperm flagella (MMAF). Immunofluorescence assay showed that DNAH8 protein expression was significantly decreased in the sperm tail of the patients, and electron microscopy exhibited an abnormal flagellum ultrastructure, while clinical pregnancy could be achieved by intracytoplasmic sperm injection. Therefore, the compound heterozygous mutations in the DNAH8 gene may be responsible for MMAF.

Defining new genetic etiologies of male infertility: progress and future prospects

Male infertility is a common and complex disease, manifesting as a wide range of phenotypes, ranging from apparently normal semen parameters with an inexplicable inability to conceive, to the complete absence of sperm production. The diversity of male infertility phenotypes, coupled with the extreme complexity of spermatogenesis has significantly confounded the identification of the underlying genetic causes for these conditions, though incremental progress has been made, particularly in the past decade. In this review, we discuss the progress that has been made to date, tools and resources that have proven effective in accelerating discovery of novel genetic markers for male infertility, and areas in which we see the greatest potential for advancing the field in the coming years. These include the development and use of robust phenotyping tools, the continued development of in vitro and animal models for variant validation, increased utilization and refinement of whole genome approaches for discovery, and further expansion of consortia that assemble groups of clinicians and basic researchers with the unified goal of disentangling the complex genetic architecture of male infertility. As these resources mature, and funding agencies increasingly recognize the importance of these efforts for improving human health, the discovery of novel genetic markers for male infertility will certainly continue to accelerate.

Novel mutations in FSIP2 lead to multiple morphological abnormalities of the sperm flagella and poor ICSI prognosis

Multiple morphological abnormalities of the sperm flagella (MMAF) is defined as deformities that cause sperm motility disorders, further resulting in male infertility. However, the reported genes related to sperm flagellar defects can only explain approximately 60% of human MMAF cases. Here, we report two novel compound heterozygous mutations, c.16246_16247insCCCAAATATCACC (p. T5416fs*7) and c.17323C > T (p.Q5774*), in the fibrous sheath-interacting protein 2 gene (FSIP2; OMIM: 615796) in an infertile patient by whole-exome sequencing (WES). Western blotting and immunofluorescence staining confirmed that the compound heterozygous mutations abrogated FSIP2 protein expression. Notably, our staining revealed that FSIP2 is expressed in the cytoplasm of primary germ cell and flagella of spermatids during the spermiogenesis. Moreover, intracytoplasmic sperm injection (ICSI) was carried out using sperm from this patient; however, pregnancy failed after embryo transfer through one cycle. Our findings may be helpful in establishing a genetic diagnosis for MMAF, as well as provide additional beneficial knowledge for genetic counseling and infertility treatment.

The sodium/proton exchanger SLC9C1 (sNHE) is essential for human sperm motility and fertility

Asthenozoospermia, defined by the absence or reduction of sperm motility, constitutes the most frequent cause of human male infertility. This pathological condition is caused by morphological and/or functional defects of the sperm flagellum, which preclude proper sperm progression. While in the last decade many causal genes were identified for asthenozoospermia associated with severe sperm flagellar defects, the causes of purely functional asthenozoospermia are still poorly defined. We describe here the case of an infertile man, displaying asthenozoospermia without major morphological flagellar anomalies and carrying a homozygous splicing mutation in SLC9C1 (sNHE), which we identified by whole-exome sequencing. SLC9C1 encodes a sperm-specific sodium/proton exchanger, which in mouse regulates pH homeostasis and interacts with the soluble adenylyl cyclase (sAC), a key regulator of the signalling pathways involved in sperm motility and capacitation. We demonstrate by means of RT-PCR, immunodetection and immunofluorescence assays on patient's semen samples that the homozygous splicing mutation (c.2748 + 2 T > C) leads to in-frame exon skipping resulting in a deletion in the cyclic nucleotide-binding domain of the protein. Our work shows that in human, similar to mouse, SLC9C1 is required for sperm motility. Overall, we establish a homozygous truncating mutation in SLC9C1 as a novel cause of human asthenozoospermia and infertility.