Genetic causes of spermatogenic failure

Genomic aspects in reproductive medicine

Infertility is a complex disease characterized by extreme genetic heterogeneity, compounded by various environmental factors. While there are exceptions, individual genetic and genomic variations related to infertility are typically rare, often family-specific, and may serve as susceptibility factors rather than direct causes of the disease. Consequently, identifying the cause of infertility and developing prevention and treatment strategies based on these factors remain challenging tasks, even in the modern genomic era. In this review, we first examine the genetic and genomic variations associated with infertility, and subsequently summarize the concepts and methods of preimplantation genetic testing in light of advances in genome analysis technology.

Correlation between LHCGR and NR5A1 genes polymorphism and male infertility risk

INTRODUCTION

Infertility is one of the important phenomena in human reproduction. Genetic factors are the most important cause of male infertility. Here, we aimed to investigate the correlation between idiopathic male infertility and SNPs of the LHCGR (rs2293275) and NR5A1 (rs1057517779) genes in the Iranian-Azeri population.

METHODS

This case-control study consisted of 100 males with infertility and 100 healthy males from the Iranian Azeri population. Genomic DNA isolation from whole blood samples and Tetra-primer amplification refractory mutation system-polymerase chain reaction (Tetra-ARMS-PCR) method was used for genotyping. The data analysis was performed by chi-square (χ2) and Fisher's exact tests.

RESULTS

Genotyping analysis for LHCGR (rs2293275) polymorphism indicated that the frequency of C in the case group was significantly higher than in the control group (P < .05). Moreover, genotyping analysis for NR5A1 (rs1057517779) polymorphism indicated that the frequencies of the A allele and heterozygote GA genotype in the case group were significantly higher than those in the control group (P < .05).

CONCLUSION

Our study demonstrated that the SNPs of LHCGR (rs2293275) and NR5A1 (rs1057517779) genes may play a critical role in male infertility in the Iranian Azeri population. However, further studies on other ethnic origins with larger sample sizes are essential for accessing more accurate results. Moreover, functional experiments might be needed to understand the role of these polymorphisms in the molecular pathways involved in male fertility.

Tandem mass tag-based quantitative proteomics analyses of the spermatogenesis-ameliorating effect of Youjing granule on rats

RATIONALE

Male infertility is a common reproductive system disease manifested as aberrant spermatogenesis and identified as "kidney deficiency and dampness" in Chinese traditional medicine. Youjing granule (YG) is a Chinese material medica based on tonifying kidneys and removing dampness. It has proven to be able to regulate semen quality in clinical application, but the underlying mechanism has not been clarified.

METHODS

Using serum containing YG to treat primarily cultured spermatogonial stem cells (SSCs), the apoptotic rate and mitosis phase ratio of SSCs were measured. The liquid chromatography-tandem mass spectrometry with tandem mass tags method was applied for analyzing the serum of rats treated with YG/distilled water, and proteomic analyses were performed to clarify the mechanisms of YG.

RESULTS

Totally, 111 proteins in YG-treated serum samples were differentially expressed compared with control groups, and 43 of them were identified as potential target proteins, which were further annotated based on their enrichment in Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways. Proteomic analyses showed that the mechanisms of YG may involve regulation of glycolysis, gluconeogenesis and nucleotide-binding and oligomerization domain-like receptor signaling pathway. In addition, RhoA and Lamp2 were found to be possible responders of YG through reviewing the literature.

CONCLUSIONS

The results demonstrate that our serum proteomics platform is clinically useful in understanding the mechanisms of YG.

A Novel Frameshift Microdeletion of the TEX12 Gene Caused Infertility in Two Brothers with Nonobstructive Azoospermia

Male infertility is a growing health problem, which affects approximately 7% of the global male population. Nonobstructive azoospermia (NOA) is one of the most severe forms of male infertility caused by genetic defects, including chromosome structural abnormalities, Y chromosome microdeletions, or single-gene alterations. However, the etiology of up to 40% of NOA cases is unidentified. By whole-exome sequencing, we detected a homozygous 5-bp-deletion variant in exon 4 of the TEX12 gene (c.196-200del, p.L66fs, NM_031275.4) in two brothers with NOA of a nonconsanguineous Vietnamese family. This deletion variant of 5 nucleotides (ATTAG) results in a premature stop codon in exon 4 and truncation of the C-terminal. Segregation analysis by Sanger sequencing confirmed that the deletion variant was inherited in an autosomal recessive pattern. The 1st and 3rd infertile sons were homozygous for the deletion, whereas the 2nd fertile son and both parents were heterozygous. The new deletion mutation identified in TEX12 gene caused loss of function of TEX12 gene. The loss of TEX12 function has already caused infertility in male mice. Therefore, we concluded that the loss of TEX12 function may cause infertility in men. To our knowledge, this is the first case reported so far indicating disruption of human TEX12, which leads to infertility in men.

Transcriptomic signatures for human male infertility

Introduction: Male infertility is a common, complex disorder. A better understanding of pathogenesis and etiology is needed for timely diagnosis and treatment. The aim of this study, therefore, was to identify genes involved in the pathogenesis of idiopathic male infertility based on data from transcriptomic level supported with data from genomic level. Materials and methods: First, we performed whole gene expression analysis in 20 testis biopsy samples of patients with severely impaired (10) and normal spermatogenesis (10). Further, we have performed systematic review of comparable male infertility studies and overlapped the most significantly expressed genes identified in our study with the most differentially expressed genes from selected studies. Gene Ontology analysis and KEGG functional enrichment have been performed with Enrichr analysis tool. Additionally, we have overlapped these genes with the genes where rare variants have been identified previously. Results: In 10 patients with severely impaired spermatogenesis and 10 controls, we identified more than 1,800 differentially expressed genes (p < 0.001). With the systematic review of three previously performed microarray studies that have met inclusion criteria we identified 257 overlapped differentialy expressed genes (144 downregulated and 113 upregulated). Intersection of genes from transcriptomic studies with genes with identified rare variants revealed a total of 7 genes linked with male infertility phenotype (CYP11A1, CYP17A1, RSPH3, TSGA10, AKAP4, CCIN, NDNF). Conclusion: Our comprehensive study highlighted the role of four genes in pathogenesis of male infertility and provided supporting evidence for three promising candidate genes which dysfunction may result in a male infertility disorder.

Towards a Multi-Omics of Male Infertility

Infertility is a common problem affecting one in six couples and in 30% of infertile couples, the male factor is a major cause. A large number of genes are involved in spermatogenesis and a significant proportion of male infertility phenotypes are of genetic origin. Studies on infertility have so far primarily focused on chromosomal abnormalities and sequence variants in protein-coding genes and have identified a large number of disease-associated genes. However, it has been shown that a multitude of factors across various omics levels also contribute to infertility phenotypes. The complexity of male infertility has led to the understanding that an integrated, multi-omics analysis may be optimal for unravelling this disease. While there is a vast array of different factors across omics levels associated with infertility, the present review focuses on known factors from the genomics, epigenomics, transcriptomics, proteomics, metabolomics, glycomics, lipidomics, miRNomics, and integrated omics levels. These include: repeat expansions in AR, POLG, ATXN1, DMPK, and SHBG, multiple SNPs, copy number variants in the AZF region, disregulated miRNAs, altered H3K9 methylation, differential MTHFR, MEG3, PEG1, and LIT1 methylation, altered protamine ratios and protein hypo/hyperphosphorylation. This integrative review presents a step towards a multi-omics approach to understanding the complex etiology of male infertility. Currently only a few genetic factors, namely chromosomal abnormalities and Y chromosome microdeletions, are routinely tested in infertile men undergoing intracytoplasmic sperm injection. A multi-omics approach to understanding infertility phenotypes may yield a more holistic view of the disease and contribute to the development of improved screening methods and treatment options. Therefore, beside discovering as of yet unknown genetic causes of infertility, integrating multiple fields of study could yield valuable contributions to the understanding of disease development. Future multi-omics studies will enable to synthesise fragmented information and facilitate biomarker discovery and treatments in male infertility.

The Fate of Leydig Cells in Men with Spermatogenic Failure

The steroidogenic cells in the testicle, Leydig cells, located in the interstitial compartment, play a vital role in male reproductive tract development, maintenance of proper spermatogenesis, and overall male reproductive function. Therefore, their dysfunction can lead to all sorts of testicular pathologies. Spermatogenesis failure, manifested as azoospermia, is often associated with defective Leydig cell activity. Spermatogenic failure is the most severe form of male infertility, caused by disorders of the testicular parenchyma or testicular hormone imbalance. This review covers current progress in knowledge on Leydig cells origin, structure, and function, and focuses on recent advances in understanding how Leydig cells contribute to the impairment of spermatogenesis.

Association of CATSPER1, SPATA16 and TEX11 genes polymorphism with idiopathic azoospermia and oligospermia risk in Iranian population

Background

Male infertility is a heterogeneous disease which can occur due to spermatogenesis defects. The idiopathic azoospermia and oligospermia are the common cause of male infertility with unknown underlying molecular mechanisms. The aim of this study was to investigate association of idiopathic azoospermia and oligospermia with single-nucleotide polymorphisms of CATSPER1, SPATA16 and TEX11 genes in Iranian-Azeri men.

Methods

In this case–control study, we recruited 100 infertile men (case group) and 100 fertile men (control group) from Azeri population in north western provinces, Iran, population. The genomic DNA was extracted using a proteinase K method from peripheral blood leukocytes. The genotypes analysis was conducted using tetra-primer amplification refractory mutation system-polymerase chain reaction method. The obtained data were analyzed by statistical software.

Results

We found a significant difference in the frequencies of heterozygote AB and mutant homozygote BB genotypes in the CATSPER1 (rs2845570) gene polymorphism between patients and healthy controls (p < 0.05). Moreover, we observed a significant difference in the frequencies of heterozygote BA genotype in the SPATA16 (rs1515442) gene polymorphism between patients and healthy controls (p < 0.05). However, no significant difference was found in genotypes distribution of case and control groups in the TEX11 (rs143246552) gene polymorphism.

Conclusion

Our finding showed that the CATSPER1 (rs2845570) and SPATA16 (rs1515442) genes polymorphism may play an important role in idiopathic azoospermia and oligospermia in Iranian Azeri population. However, more extensive studies with larger sample sizes from different ethnic origins are essential for access more accurate results.

Dissecting the relationship between artificial insemination success and bull semen quality in the arid region of Tiaret (Algeria)

Despite being subject to prior assortment, frozen bull sperms commercialized for artificial insemination may present certain morphological defects. The present study aims (i) to assess the artificial insemination success of the most common cattle breeds in Algeria and (ii) to evaluate the possible effects of commercialized bull’s semen quality on this operation. Artificial insemination was assessed through four years of field monitoring by inseminating different cattle breeds of normal fertility. However, semen quality was evaluated using light microscopy by measuring viability, motility, and morphological abnormalities of spermatozoa. Field study revealed a high percentage of normal calving in red and white Holstein breed (44.83 %) against the high percentage of embryonic mortality (46.43 %) and calving with a malformation (10.71 %) in Montbéliarde breed. Semen quality assessment revealed that sperm viability and motility were higher in Holstein breeds than in Montbéliarde. Furthermore, significant differences between semen bulls were found in the proportion of abnormal spermatozoa; a higher rate of sperms with the abnormal head was observed in the black and white Holstein breed (69.3±10.98 %). However, the percentage of abnormal sperms with tail defects was higher in the Montbéliarde breed (67.5±10.74 %). The lousy quality of the selected semen and/or the poor handling and storage of frozen semen constitute a determinant factor that hinders the success of artificial insemination in the arid region of Tiaret (Algeria).

Clinical and laboratory differences between chromosomal and undefined causes of non-obstructive azoospermia: A retrospective study

BACKGROUND

Knowledge of clinical and laboratory differences between chromosomal and undefined causes aids etiological research on non-obstructive azoospermia.

OBJECTIVE

Compare clinical and laboratory differences between men with non-obstructive azoospermia due to chromosomal anomalies versus undefined causes.

DESIGN AND SETTING

A cross-sectional retrospective study conducted at a public university hospital in Campinas (Brazil).

METHODS

All men aged 20-40 years with non-obstructive azoospermia were included in the analysis.

RESULTS

The 107 cases included 14 with Klinefelter syndrome (KS) (13%), 1 with mosaic KS, 4 with sex development disorders (2 testicular XX, 1 NR5A1 gene mutation, and 1 mild androgen insensitivity syndrome) (4%), 9 with other non-obstructive azoospermia etiologies (8%), and 79 with undefined causes. The 22 chromosomal anomaly cases (14 KS, 1 mosaic KS, 2 testicular XX, 4 sex chromosome anomalies, and 1 autosomal anomaly) were compared with the 79 undefined cause cases. The KS group had lower average testicular volume, shorter penile length, and lower total testosterone levels but greater height, arm span, serum luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels, and gynecomastia frequency (absent in the undefined group and affecting more than half of the KS group). Patients with testicular XX DSD had LH, FSH, and penile length data intermediate between the KS and undefined cause groups, testicular volume similar to the KS group, and other data similar to the undefined group.

CONCLUSION

Clinical and laboratory data differentiate men with non-obstructive azoospermia and chromosomal anomalies, particularly KS and testicular XX, from those with undefined causes or other chromosomal anomalies.

CFTR mutations causing congenital unilateral absence of the vas deferens (CUAVD) and congenital absence of the uterus (CAU) in a consanguineous family

Cystic fibrosis (CF) is one of the most common recessive genetic diseases, with a wide spectrum of phenotypes, ranging from infertility to severe pulmonary disease. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are considered the main genetic cause for CF. In this study, we recruited a consanguineous Iranian pedigree with four male patients diagnosed with congenital unilateral absence of the vas deferens (CUAVD), and one female patient diagnosed with congenital absence of the uterus (CAU). Testicular biopsy of one patient was performed, and hematoxylin and eosin (H and E) staining of testis sections displayed the presence of germ cell types ranging from spermatogonia to mature spermatids, indicating obstructive azoospermia. To explore the underlying genetic factor in this familial disorder, we therefore performed whole-exome sequencing (WES) on all available family members. WES data filtration and CFTR haplotype analysis identified compound heterozygous mutations in CFTR among four patients (two CUAVD patients carried p.H949Y and p.L997F, and one CUAVD and the female CAU patient carried p.H949Y and p.I148T). All these mutations were predicted to be deleterious by at least half of the prediction software programs and were confirmed by Sanger sequencing. Our study reported that CFTR compound heterozygous mutations in a consanguineous Iranian family cause infertility in both sexes.

Altered Gene Expression in the Testis of Infertile Patients with Nonobstructive Azoospermia

Background

The molecular mechanism of nonobstructive azoospermia (NOA) remains unclear. The aim of this study was to identify gene expression changes in NOA patients and to explore potential biomarkers and therapeutic targets.

Methods

The gene expression profiles of GSE45885 and GSE145467 were collected from the Gene Expression Omnibus (GEO) database, and the differences between NOA and normal spermatogenesis were analyzed. Enrichment analysis was performed to explore biological functions for common differentially expressed genes (DEGs) in GSE45885 and GSE145467. Coexpression analysis of DEGs in GSE45885 was performed, and two modules with the highest correlation with NOA were screened. Key genes were then screened from the intersection genes of the two modules and common DEGs and PPI network. The expression of key genes was validated by quantitative real-time polymerase chain reaction (qRT-PCR) experiments. Finally, through miRTarBase, miRDB, and RAID, the miRNAs were predicted to regulate key genes, respectively.

Results

A total of 345 common DEGs were identified and they were mainly related to spermatogenesis, insulin signaling pathway. Coexpression analysis of DEGs in GSE45885 yielded eight modules; MEblack and MEturquoise had the highest correlation with NOA. Six genes in MEturquoise and RNF141 in MEblack were identified as key genes. qRT-PCR experiments validated the differential expression of key genes between NOA and control. Furthermore, RNF141 was regulated by the largest number of miRNAs.

Conclusion

Our findings suggest that the significant change expression of key genes may be potential markers and therapeutic targets of NOA and may have some impact on the development of NOA.

SPATS1 (spermatogenesis-associated, serine-rich 1) is not essential for spermatogenesis and fertility in mouse

SPATS1 (spermatogenesis-associated, serine-rich 1) is an evolutionarily conserved, testis-specific protein that is differentially expressed during rat male meiotic prophase. Some reports have suggested a link between SPATS1 underexpression/mutation and human pathologies such as male infertility and testicular cancer. Given the absence of functional studies, we generated a Spats1 loss-of-function mouse model using CRISPR/Cas9 technology. The phenotypic analysis showed no overt phenotype in Spats1^-/- mice, with both males and females being fertile. Flow cytometry and histological analyses did not show differences in the testicular content and histology between WT and knockout mice. Moreover, no significant differences in sperm concentration, motility, and morphology, were observed between WT and KO mice. These results were obtained both for young adults and for aged animals. Besides, although an involvement of SPATS1 in the Wnt signaling pathway has been suggested, we did not detect changes in the expression levels of typical Wnt pathway-target genes in mutant individuals. Thus, albeit Spats1 alteration might be a risk factor for male testicular health, we hereby show that this gene is not individually essential for male fertility and spermatogenesis in mouse.

Y chromosome microdeletion and cytogenetic findings in male infertility: A cross-sectional descriptive study

Background

Infertility affects about 15% of couples worldwide, and the male factor alone is responsible for approximately 50% of the cases. Genetic factors have been found to play important roles in the etiology of azoospermia and severe oligospermia conditions that affect 30% of individuals seeking treatment at infertility clinics.

Objective

To determine the frequency of chromosomal abnormalities and Y chromosome microdeletion in infertile men.

Materials and Methods

A total of 100 infertile men with abnormal semen parameters were included in this study from 2014 to 2018. Chromosomal analysis was carried out using standard G-banding using Trypsin Giemsa protocol. Multiplex polymerase chain reaction was used to determine the Y microdeletion frequency.

Results

All participants were aged between 22 and 48 yr with a mean and standard deviation of 35.5 ± 5.1. Of the 100 subjects included in the study, three had Klinefelter syndrome-47,XXY, one had balanced carrier translocation-46,XY,t(2;7)(q21;p12), one with the balanced carrier translocation with inversion of Y chromosome 45,XY,der(13;14)(q10;q10),inv(Y), one had polymorphic variant of chromosome 15, one had Yqh-, and another had an inversion of chromosome 9. Y chromosome microdeletion of Azoospermia factor c region was observed in 2% of the cases. To the best of our knowledge, the current study is the first reported case with unique, balanced carrier translocation of chromosome 2q21 and 7p21.

Conclusion

The present study emphasizes the importance of routine cytogenetic screening and Y microdeletion assessment for infertile men, which can provide specific and better treatment options before undergoing assisted reproductive technology during genetic counseling.

Genetic mutations contributing to non-obstructive azoospermia

Non-obstructive azoospermia is a distinct diagnosis within male infertility in which no sperm is found in the ejaculate as a result of spermatogenesis failure. Because of the increased prevalence of genetic abnormalities in men with non-obstructive azoospermia, male infertility guidelines recommend screening for karyotype abnormalities and Y chromosome microdeletions in this population. Numerous karyotype abnormalities may be present resulting in impaired spermatogenesis, including: Klinefelter syndrome, translocations, and deletions. Y chromosome microdeletions of the AZFa, AZFb, AZFc subregions all can also result in non-obstructive azoospermia with the possibility of sperm being present if only the AZFc subregion is deleted. While these are the two genetic tests recommended by the guidelines, nearly 50%-80% of non-obstructive azoospermia has no identifiable cause and is deemed idiopathic. Several other genetic defects can lead to non-obstructive azoospermia including Kallmann syndrome, mild androgen insensitivity syndrome, and TEX11. While many additional candidate genes have been proposed, many have yet to be verified or are so infrequent in the population that screening is cost-ineffective. Much research is still required in the genetics of non-obstructive azoospermia and will require multi-institutional initiatives to better understand the genetics of condition.

Testicular leiomyoma and spermatogenic failure syndrome in a seabass from broodstock

Testicular leiomyomas and gonadal dysfunctions are not commonly reported in teleost and particularly in broodstock fish. In the present work, a testicular leiomyoma related to an unusual case of spermatogenic failure syndrome, in a broodstock seabass coming from an Italian aquaculture farm, is reported. At gross pathology, the circumscribed neoplasia showed several white nodular masses, originating from the gonad, deforming the anatomo-physiological shape. From light microscopy, the presence of neoplastic tissue islands with spindle cells with a whirling pattern and the low presence of connective tissue were evident and originated from smooth muscle cells. Seminiferous tubules showed severe azoospermia with the absence of sperm cells even closer to the neoplastic area. Immunohistochemical analysis was positive for alpha-SMA, desmin and vimentin but negative for S-100, confirming a diagnosis of leiomyoma. This is the first report of spermatogenic failure syndrome associated with a testicular leiomyoma in fish from broodstock. More efforts should be made in studying broodstock fish pathologies related to fish maintenance and hormonal treatments that could economically affect aquaculture production.

Fertility Relevance Probability Analysis Shortlists Genetic Markers for Male Fertility Impairment

Impairment of male fertility is one of the major public health issues worldwide. Nevertheless, genetic causes of male sub- and infertility can often only be suspected due to the lack of reliable and easy-to-use routine tests. Yet, the development of a marker panel is complicated by the large quantity of potentially predictive markers. Actually, hundreds or even thousands of genes could have fertility relevance. Thus, a systematic method enabling a selection of the most predictive markers out of the many candidates is required. As a criterion for marker selection, we derived a gene-specific score, which we refer to as fertility relevance probability (FRP). For this purpose, we first categorized 2,753 testis-expressed genes as either candidate markers or non-candidates, according to phenotypes in male knockout mice. In a parallel approach, 2,502 genes were classified as candidate markers or non-candidates based on phenotypes in men. Subsequently, we conducted logistic regression analyses with evolutionary rates of genes (dN/dS), transcription levels in testis relative to other organs, and connectivity of the encoded proteins in a protein-protein interaction network as covariates. In confirmation of the procedure, FRP values showed the expected pattern, thus being overall higher in genes with known relevance for fertility than in their counterparts without corresponding evidence. In addition, higher FRP values corresponded with an increased dysregulation of protein abundance in spermatozoa of 37 men with normal and 38 men with impaired fertility. Present analyses resulted in a ranking of genes according to their probable predictive power as candidate markers for male fertility impairment. Thus, AKAP4, TNP1, DAZL, BRDT, DMRT1, SPO11, ZPBP, HORMAD1, and SMC1B are prime candidates toward a marker panel for male fertility impairment. Additional candidate markers are DDX4, SHCBP1L, CCDC155, ODF1, DMRTB1, ASZ1, BOLL, FKBP6, SLC25A31, PRSS21, and RNF17. FRP inference additionally provides clues for potential new markers, thereunder TEX37 and POU4F2. The results of our logistic regression analyses are freely available at the PreFer Genes website (https://prefer-genes.uni-mainz.de/).

Genome-wide association study identifies candidate markers related to lincRNAs associated with male infertility in the Greek population

BACKGROUND

Male infertility is currently one of the most common problems faced by couples worldwide. We performed a GWAS on Greek population and gathered statistically significant SNPs in order to investigate whether they lie within or near lncRNA regions.

OBJECTIVES

The aim of this study was to investigate whether polymorphisms on or near lncRNAs affect interactions with miRNAs and can cause male infertility.

MATERIALS AND METHODS

In the present study, a GWAS was conducted, using samples from 159 individuals (83 normozoospermic individuals and 76 patients of known fertility issues). Standard procedures for quality controls and association testing were followed, based on case-control testing.

RESULTS

We detected six lncRNAs (LINC02231, LINC00347, LINC02134, NCRNA00157, LINC02493, Lnc-CASK-1) that are associated with male infertility through their interaction with miRNAs. Furthermore, we identified the genes targeted by those miRNAs and highlighted their functions in spermatogenesis and the fertilization process.

DISCUSSION AND CONCLUSION

lncRNAs are involved in spermatogenesis through their interaction with miRNAs. Thus, their study is very important, and it may contribute to the understanding of the molecular mechanisms underlying male infertility.

Hypomethylation of the DAZ3 promoter in idiopathic asthenospermia: a screening tool for liquid biopsy

Given the role of the deleted in azoospermia gene in male infertility, whether the somatic deleted in azoospermia methylation status is associated with idiopathic asthenospermia should be determined. To investigate the methylation levels of the deleted in azoospermia promoter in peripheral white blood cells from idiopathic asthenospermia patients relative to those in normozoospermia controls, 61 ethylene diamine tetraacetic acid anticoagulant blood samples were drawn from all participants for DNA isolation. The deleted in azoospermia promoter methylation ratio was detected by MassARRAY-based methylation quantification and confirmed by quantitative methylation-specific polymerase chain reaction. A MassARRAY-based methylation analysis showed that the deleted in azoospermia 3 promoter (0 to − 2 kbp) was significantly hypomethylated in peripheral white blood cells from idiopathic asthenospermia males, specifically one CpG site (− 246 to − 247). Quantitative methylation-specific polymerase chain reaction data further confirmed that the methylation level of the deleted in azoospermia 3 promoter region in idiopathic asthenospermia patients was significantly lower than that in normozoospermia males. The area under the receiver operating characteristic curve determined by quantitative methylation-specific polymerase chain reaction was 0.737 (95% confidence interval: 0.552 to 0.924), with a sensitivity of 53.9% and a specificity of 88.2% at a cut-off level of 74.7%. Therefore, our results suggested that methylation ratio detection of the deleted in azoospermia 3 promoter region by real-time polymerase chain reaction assay is a promising and feasible tool for liquid biopsy in the clinical laboratories. The methylation status of other reported infertility-related genes should also be investigated in peripheral white blood cells.

Conversion from spermatogonia to spermatocytes: Extracellular cues and downstream transcription network

Spermatocyte (spc) formation from spermatogonia (spg) differentiation is the first step of spermatogenesis which produces prodigious spermatozoa for a lifetime. After decades of studies, several factors involved in the functioning of a mouse were discovered both inside and outside spg. Considering the peculiar expression and working pattern of each factor, this review divides the whole conversion of spg to spc into four consecutive development processes with a focus on extracellular cues and downstream transcription network in each one. Potential coordination among Dmrt1, Sohlh1/2 and BMP families mediates Ngn3 upregulation, which marks progenitor spg, with other changes. After that, retinoic acid (RA), as a master regulator, promotes A1 spg formation with its helpers and Sall4. A1-to-B spg transition is under the control of Kitl and impulsive RA signaling together with early and late transcription factors Stra8 and Dmrt6. Finally, RA and its responsive effectors conduct the entry into meiosis. The systematic transcription network from outside to inside still needs research to supplement or settle the controversials in each process. As a step further ahead, this review provides possible drug targets for infertility therapy by cross-linking humans and mouse model.

External and Genetic Conditions Determining Male Infertility

We explain environmental and genetic factors determining male genetic conditions and infertility and evaluate the significance of environmental stressors in shaping defensive responses, which is used in the diagnosis and treatment of male infertility. This is done through the impact of external and internal stressors and their instability on sperm parameters and their contribution to immunogenetic disorders and hazardous DNA mutations. As chemical compounds and physical factors play an important role in the induction of immunogenetic disorders and affect the activity of enzymatic and non-enzymatic responses, causing oxidative stress, and leading to apoptosis, they downgrade semen quality. These factors are closely connected with male reproductive potential since genetic polymorphisms and mutations in chromosomes 7, X, and Y critically impact on spermatogenesis. Microdeletions in the Azoospermic Factor AZF region directly cause defective sperm production. Among mutations in chromosome 7, impairments in the cystic fibrosis transmembrane conductance regulator CFTR gene are destructive for fertility in cystic fibrosis, when spermatic ducts undergo complete obstruction. This problem was not previously analyzed in such a form. Alongside karyotype abnormalities AZF microdeletions are the reason of spermatogenic failure. Amongst AZF genes, the deleted in azoospermia DAZ gene family is reported as most frequently deleted AZF. Screening of AZF microdeletions is useful in explaining idiopathic cases of male infertility as well as in genetic consulting prior to assisted reproduction. Based on the current state of research we answer the following questions: (1) How do environmental stressors lessen the quality of sperm and reduce male fertility; (2) which chemical elements induce oxidative stress and immunogenetic changes in the male reproductive system; (3) how do polymorphisms correlate with changes in reproductive potential and pro-antioxidative mechanisms as markers of pathophysiological disturbances of the male reproductive condition; (4) how do environmental stressors of immunogenetic disorders accompany male infertility and responses; and (5) what is the distribution and prevalence of environmental and genetic risk factors.

The possible role of NF-κB1 Rs28362491 polymorphism in male fertility of Egyptian population

Male reproductive impairment is responsible for at least 50% of cases of couple infertility. Nuclear factor-kappa B (NF-κB) has been functionally linked to germ cell apoptosis, which may affect human fertility. The aim of this study was to determine the association between the rs28362491 SNP of the NF-κB1 gene and infertility in Egyptian men. In this case-control study, semen and blood samples of 247 infertile men, constituting the case group, and of 113 fertile healthy men as the control group were analysed. All study participants were genotyped for polymorphism of the NF-κB1 gene (rs28362491) by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Heterozygous I/D genotype of the NF-κB1 rs28362491 polymorphism was associated with a significantly lower risk of poor semen quality, including asthenozoospermia, astheno-teratozoospermia, and oligo-astheno-teratozoospermia, when compared to I/I genotype (odds ratio = 0.25, 0.26, 0.18, p < .0005, <.0005, <.0005) respectively. Overall, the presence of the D allele was associated with a significantly decreased risk of poor sperm quality as compared to the I allele (odds ratio = 0.56, 0.64, 0.49, p = .050, .038, .001). In conclusion, these results suggest that heterozygosity of the NF-κB1 gene may play a protecting role against male infertility in Egyptians.

Knockout of serine-rich single-pass membrane protein 1 (Ssmem1) causes globozoospermia and sterility in male mice†

Globozoospermia (sperm with an abnormally round head shape) and asthenozoospermia (defective sperm motility) are known causes of male infertility in human patients. Despite many studies, the molecular details of the globozoospermia etiology are still poorly understood. Serine-rich single-pass membrane protein 1 (Ssmem1) is a conserved testis-specific gene in mammals. In this study, we generated Ssmem1 knockout (KO) mice using the CRISPR/Cas9 system, demonstrated that Ssmem1 is essential for male fertility in mice, and found that SSMEM1 protein is expressed during spermatogenesis but not in mature sperm. The sterility of the Ssmem1 KO (null) mice is associated with globozoospermia and loss of sperm motility. To decipher the mechanism causing the phenotype, we analyzed testes with transmission electron microscopy and discovered that Ssmem1-disrupted spermatids have abnormal localization of Golgi at steps eight and nine of spermatid development. Immunofluorescence analysis with anti-Golgin-97 to label the trans-Golgi network, also showed delayed movement of the Golgi to the spermatid posterior region, which causes failure of sperm head shaping, disorganization of the cell organelles, and entrapped tails in the cytoplasmic droplet. In summary, SSMEM1 is crucial for intracellular Golgi movement to ensure proper spatiotemporal formation of the sperm head that is required for fertilization. These studies and the pathway in which SSMEM1 functions have implications for human male infertility and identifying potential targets for nonhormonal contraception.

Evaluation from a different perspective of 10-year results of infertile males with Y chromosome AZFc microdeletions compared with a control group

AZFc microdeletions will be evaluated upon being divided into partial and complete subgroups. The association of deletions with reactive oxidative stress (ROS) and sperm DNA fragmentation (SDFI) and the impact of their coexistence on fertility starting from the pregnancy process until live birth will be presented. Semen analyses, microbiological results, hormones, ROS and sperm TUNEL tests were checked. Preimplantation genetic testing (PGT) was planned for relevant patients. Intracytoplasmic sperm injection (ICSI) was applied. Their embryo fragmentation was monitored via time lapse. Their results were compared with those with no AZF deletion and no other genetic problems. Azoospermia rate was 71.5%, m-TESE success rate was 25%, pregnancy rate was 26% and live child rate was 2.2%. No difference was detected between the partial and total groups in terms of ROS and SDFI rates and no difference was identified with the control group. Better results were obtained in terms of live child rate in patients with partial AZFc and low ROS/SDFI. Spermatozoon was retrieved in AZFc deletions and pregnancy, and live child was identified. No AZFc impact was observed on ROS and SDFI in the results compared with the control groups in terms of their coexistence.

Decreased expression of MRE11 and RAD50 in testes from humans with spermatogenic failure

PURPOSE

To assess testicular mRNA and protein expression levels of MRE11 and RAD50 in human azoospermia patients.

METHODS

Patients diagnosed with maturation arrest at the spermatocyte stage (MA) and Sertoli cell-only syndrome (SCOS) were recruited through diagnostic testicular biopsy. Patients with normal spermatogenesis were studied as controls. In addition, knockdown of MRE11 and RAD50 was performed in GC-2spd(ts) cells to investigate their roles in cellular proliferation and apoptosis.

RESULTS

mRNA and protein expression levels of MRE11 and RAD50 were measured using quantitative polymerase chain reaction, western blotting, and immunohistochemistry, respectively. Knockdown of both MRE11 and RAD50 utilized transfection with small interfering RNAs.

CONCLUSION

Our findings demonstrated altered expression levels of MRE11 and RAD50 in human testes with MA and SCOS, and showed that these alterations might be associated with impaired spermatogenesis. These results offer valuable new perspectives into the molecular mechanisms of male infertility.

TBC1D20 Is Essential for Mouse Blood-Testis Barrier Integrity Through Maintaining the Epithelial Phenotype and Modulating the Maturation of Sertoli Cells

Sertoli cells are important for spermatogenesis not only by directly interacting with germ line cells in the seminiferous epithelium but also by constituting the blood-testis barrier (BTB) structure to create a favorable environment for spermatogenesis. Blind sterile (bs) male mice are infertile, with excessive germ cell apoptosis and spermatogenesis arrest. TBC1D20 (TBC1 domain family member 20) deficiency has been identified as the causative mutation in bs mice. However, whether TBC1D20 loss of function also impairs BTB integrity, which further contributes to the failed spermatogenesis of bs male mice, remains unclear. In the present study, biotin tracer assay and transmission electron microscopy showed severely disrupted BTB integrity in bs testes. Compared to the wild-type Sertoli cells, BTB components of cultured bs Sertoli cells in vitro was perturbed with downregulation of E-cadherin, ZO-1, β-catenin, and Claudin 11. The obvious rearrangement of F-actin indicated disrupted epithelial-mesenchymal balance in TBC1D20-deficient Sertoli cells. The ability of bs Sertoli cells to maintain the clone formation of spermatogonia stem cells was also obviously limited. Furthermore, the decreasing of SOX9 (sex-determining region Y box 9) and WT1 (Wilms' tumor 1) and increasing of vimentin in bs Sertoli cells indicated that TBC1D20 loss of function attenuated the differentiation progression of bs Sertoli cells. In summary, TBC1D20 loss of function impedes the maturation of adult Sertoli cells and resulted in impaired BTB integrity, which is further implicated in the infertile phenotype of bs male mice.

SYCP2 Translocation-Mediated Dysregulation and Frameshift Variants Cause Human Male Infertility

Unexplained infertility affects 2%-3% of reproductive-aged couples. One approach to identifying genes involved in infertility is to study subjects with this clinical phenotype and a de novo balanced chromosomal aberration (BCA). While BCAs may reduce fertility by production of unbalanced gametes, a chromosomal rearrangement may also disrupt or dysregulate genes important in fertility. One such subject, DGAP230, has severe oligozoospermia and 46,XY,t(20;22)(q13.3;q11.2). We identified exclusive overexpression of SYCP2 from the der(20) allele that is hypothesized to result from enhancer adoption. Modeling the dysregulation in budding yeast resulted in disrupted structural integrity of the synaptonemal complex, a common cause of defective spermatogenesis in mammals. Exome sequencing of infertile males revealed three heterozygous SYCP2 frameshift variants in additional subjects with cryptozoospermia and azoospermia. In sum, this investigation illustrates the power of precision cytogenetics for annotation of the infertile genome, suggests that these mechanisms should be considered as an alternative etiology to that of segregation of unbalanced gametes in infertile men harboring a BCA, and provides evidence of SYCP2-mediated male infertility in humans.

Recent advances and future opportunities to diagnose male infertility

PURPOSE OF REVIEW

Infertility affects 10-15% of couples, making it one of the most frequent health disorders for individuals of reproductive age. The state of childlessness and efforts to restore fertility cause substantial emotional, social, and financial stress on couples. Male factors contribute to about half of all infertility cases, and yet are understudied relative to female factors. The result is that the majority of men with infertility lack specific causal diagnoses, which serves as a missed opportunity to inform therapies for these couples.

RECENT FINDINGS

In this review, we describe current standards for diagnosing male infertility and the various interventions offered to men in response to differential diagnoses. We then discuss recent advances in the field of genetics to identify novel etiologies for formerly unexplained infertility.

SUMMARY

With a specific genetic diagnosis, male factors can be addressed with appropriate reproductive counseling and with potential access to assisted reproductive technologies to improve chances of a healthy pregnancy.

Correlation between methylenetetrahydrofolate reductase gene polymorphism and oligoasthenospermia and the effects of folic acid supplementation on semen quality

Background

The present study investigated the correlation between 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and oligoasthenospermia, as well as the effects of folic acid supplementation on semen quality.

Methods

The present study was a case control study. The PCR-chip assay was applied to analyze the distribution characteristics of the frequencies and genotypes of the MTHFR C677T allele in 167 Han Chinese patients with idiopathic male infertility (including 86 patients with oligospermia and 81 patients with asthenospermia) and in 78 males with normal semen parameters. Moreover, homocysteine (Hcy) levels were assessed for the different groups. Semen quality was measured following three months of folic acid supplementation for the oligospermia and asthenospermia groups.

Results

The cytosine-thymine (CT) genotype (50% vs. 39.5%) and the thymine-thymine (TT) genotype (51.2% vs. 7.7%) carriers in the oligospermia group exhibited significantly higher percentages compared with those of the control group. The percentage of the CT genotype carriers in the asthenospermia group was significantly higher compared with that of the control group (59.3% vs. 50%), while the frequency of the TT genotype was significantly increased (22.2% vs. 7.7%). Furthermore, serum Hcy levels in the oligospermia and asthenospermia groups were significantly higher compared with those of the control group. The data also demonstrated that sperm density increased significantly following three months of folic acid supplementation to patients with oligospermia or asthenospermia. In these patients, the highest increase was noted for the subjects carrying the TT genotype.

Conclusions

The MTHFR C677T mutation and the elevated Hcy levels are important risk factors for the development of oligoasthenospermia. Folic acid supplementation can significantly improve sperm density.

Genotyping of the EIF1AY Gene in Iranian Patients with Non-Obstructive Azoospermia

Background

EIF1AY is one of the genes essential for normal spermatogenesis and is located in azoospermic factors region.

Objective

The present study was designed to investigate the EIF1AY gene nucleotide variations, and correlate it with spermatogenic maturation arrest and azoospermia in Iranian population.

Methods

A total number of 30 Iranian idiopathic non-obstructive azoospermic patients were selected as case group and 30 fertile men served as a control group who had at least 1 child. Nucleotide variation was analyzed in exon 3 and exon 5 in EIF1AY gene of both groups. DNA extraction from peripheral blood samples of selected individuals was done followed by amplification by PCR and sequencing with Sangar method.

Results

Totally 3 single nucleotide variations were identified: one in the intronic region of exon 3, next one in non-coding transcript exon variant (rs13447352) and the third one in the exonic region of exon 5, all were registered in NCBI-Gene database.

Conclusion

There was no statistically significant difference in the incidence of nucleotide variation between 2 study populations (p > 0.05). Further studies are required to specify the effects of Y: T20588295G variation on modification of protein structure, as well as the expression pattern of the gene and its association with azoospermia.

Spermatogenesis disorder is associated with mutations in the ligand-binding domain of an androgen receptor

Androgens play a key role in spermatogenesis, and their functions are mediated by the androgen receptor (AR). Some mutations in the AR gene have the potential to alter the primary structure and function of the protein. The aim of this study was to investigate the AR gene mutations in a cohort of males with idiopathic azoospermia referred to Royan Institute. Fifty-one biopsy samples were obtained for routine clinical purposes from 15 men with hypospermatogenesis (HS), 17 patients with maturation arrest (MA) and 19 patients with Sertoli cell-only syndrome (SCOS). The AR cDNAs were prepared from tissue mRNAs and were sequenced. One synonymous variant and three nonsynonymous protein coding single nucleotide polymorphisms (nsSNPs) were detected. Protein structure prediction demonstrated that the S815I and M746T nonsynonymous variants would affect protein structure and its normal function. Our study suggests that mutations in the AR gene would change or disturb the receptor's normal activity. Although these variations may influence spermatogenesis, it is difficult to say that they lead to a lack of spermatogenesis.

Chromosomal translocations and semen quality: A study on 144 male translocation carriers

RESEARCH QUESTION

Chromosomal translocations are known genetic causes of male infertility. Are certain translocations or chromosomal regions more directly associated with sperm defects? Is there a threshold of sperm impairment that can be relevant for detection of translocations?

DESIGN

This is a monocentric retrospective observational study covering a 10-year period. Eighty-one patients carrying a reciprocal translocation (RCT) and 63 carrying a Robertsonian translocation (ROBT) were compared with 105 fertile patients. Semen quality before and after sperm migration was compared. The aims were to define whether a threshold based on sperm analysis could be proposed for detection of translocations and to identify whether some redundant chromosomal regions might be associated with sperm quality defects.

RESULTS

The number of progressive spermatozoa retrieved after sperm preparation (NPS-ASP) was altered in both RCT and ROBT carriers compared with controls, with a stronger alteration in ROBT. Based on the NPS-ASP results in this large group of translocation carriers, a relatively robust threshold, fixed at less than 5 million, may be proposed for detection of translocations. The alteration of NPS-ASP was independent of the chromosome involved in ROBT, while in RCT, four redundant chromosomal regions (1q21, 6p21, 16q21, 17q11.2) were associated with poor or very poor NPS-ASP.

CONCLUSIONS

The NPS-ASP appears to be a good parameter to assess sperm function and would be a useful tool to detect chromosomal translocations. Four redundant regions have been identified on four chromosomes, suggesting that they may contain genes of interest to study sperm functions.

A novel stopgain mutation c.G992A (p.W331X) in TACR3 gene was identified in nonobstructive azoospermia by targeted next-generation sequencing

BACKGROUND

Nonobstructive azoospermia (NOA) is one of the most severe forms of male infertility because of impaired spermatogenesis with the absence of spermatozoa in the ejaculate. The causes of this disease can be partly attributed to genetic factors. Some common structural variants and single nucleotide polymorphisms (SNPs) were reported to be associated with NOA. However, the underlying etiology and genetic mechanism(s) remain largely unclear. The aim of this study was to investigate the associated mutations of spermatogenic genes in Chinese infertile men with NOA.

METHODS

The entire coding region of 25 genes associated with spermatogenesis was sequenced from 200 infertile men with NOA. Screening was carried out using the targeted exome sequencing to identify genetic variations and SNPs of the entire coding region of these genes.

RESULTS

After the targeted exome sequencing data were filtered through several currently existing variation databases, a series of variations were found. In this paper, we report one novel stopgain variation c.G992A (p.W331X) in the exon 4 of TACR3 gene. The variant was heterozygous and categorized as pathogenic.

CONCLUSION

In conclusion, our study revealed a novel stopgain mutation c.G992A (p.W331X) in TACR3 which expanded the mutation spectrum of TACR3 in Chinese NOA infertile men and advanced our understanding of the genetic susceptibility to NOA.

An illustration of human sperm morphology and their functional ability among different group of subfertile males

Condensed sperm chromatin is a prerequisite for natural fertilization. Some reports suggested the prevalence of chromatin condensation defects in teratozoospermia cases with head anomalies; conversely, earlier studies exemplified its occurrence in morphologically normal spermatozoa too. The aim of this study was to compare the condensation defects in correlation with head anomalies among different groups of subfertile males and its impact on the rate of fertilization in assisted reproduction procedures. Ultrastructure analysis of spermatozoa through scanning electron microscopy and atomic force microscopy could facilitate an in-depth evaluation of sperm morphology. Nuclear condensation defects (%) in spermatozoa were analyzed in 666 subjects, and its effect on the rate of fertilization was analyzed in 116 IVF and 90 intracytoplasmic sperm injection cases. There was no correlation of condensation defects with head anomalies (%). Student's t-test showed no significant changes in mean values of condensation defects in abnormal semen samples in comparison with the normal group. Condensation defects were observed in normal spermatozoa too, which was negatively associated with the rate of fertilization in IVF (p < 0.01), but intracytoplasmic sperm injection outcome remained unaffected. Ultrastructure study revealed sperm morphological features in height, amplitude, and three-dimensional views in atomic force microscopy images presenting surface topography, roughness property of head, and compact arrangement of mitochondria over axoneme with height profile at nanoscale. In pathological forms, surface roughness and nuclear thickness were marked higher than the normal spermatozoa. Thus, percentage of normal spermatozoa with condensation defects could be a predictive factor for the rate of fertilization in IVF. From diverse shapes of nucleus in AFM imaging, it could be predicted that defective nuclear shaping might be impeding the activity of some proteins/ biological motors, those regulate the proper Golgi spreading over peri-nuclear theca.

A homozygous FANCM frameshift pathogenic variant causes male infertility

PURPOSE

Fanconi anemia (FA) genes play important roles in spermatogenesis. In mice, disruption of Fancm impairs male fertility and testicular integrity, but whether FANCM pathogenic variants (PV) similarly affect fertility in men is unknown. Here we characterize a Pakistani family having three infertile brothers, two manifesting oligoasthenospermia and one exhibiting azoospermia, born to first-cousin parents. A homozygous PV in FANCM (c.1946_1958del, p.P648Lfs*16) was found cosegregating with male infertility. Our objective is to validate that FANCM p.P648Lfs*16 is the PV causing infertility in this family.

METHODS

Exome and Sanger sequencing were used for PV screening. DNA interstrand crosslink (ICL) sensitivity was assessed in lymphocytes from patients. A mouse model carrying a PV nearly equivalent to that in the patients (Fancm^ΔC/ΔC) was generated, followed by functional analysis in spermatogenesis.

RESULTS

The loss-of-function FANCM PV increased ICL sensitivity in lymphocytes of patients and Fancm^ΔC/ΔC spermatogonia. Adult Fancm^ΔC/ΔC mice showed spermatogenic failure, with germ cell loss in 50.2% of testicular tubules and round-spermatid maturation arrest in 43.5% of tubules. In addition, neither bone marrow failure nor cancer/tumor was detected in all the patients or adult Fancm^ΔC/ΔC mice.

CONCLUSION

These findings revealed male infertility to be a novel phenotype of human patients with a biallelic FANCM PV.

Two cases of complex balanced autosomal translocations associated with severe oligozoospermia

Complex balanced autosomal translocation is rare and can lead to impaired spermatogenesis in males; however, its effects on oligozoospermia have rarely been reported. We report here two cases of rare complex balanced translocation in men with infertility. The karyotype of the first case was 46,XY,der(1)t(1;12)(p22;p11.2)ins(9;1)(p24;q25q23),der(9)ins(9;1),der(12)t(1;12)·ish der(1)t(1;12)(RP11-636B1+;RP11-659D23+)ins(9;1)(RP11-118P13+),der(9)ins(9;1),der(12)t(1;12). And the patient showed severe oligozoospermia with adult schizophrenia without other abnormalities. The karyotype of the second patient was 46,XY,der(5)t(5;11)(q14;p11.2),der(11)t(11;18)(p11.2;q11.2),der(18)t(5,18)(q14;p11.3)add(18)(q11.2?)·ish der(5)t(5;11)(RP11-846K3+,RP11-89B9+),der(11)t(11;18)(RP11-89B9-,RP11-170L12+,RP11-469N6+),der(18)t(5;18)(RP11-125L2+,RP11-29M13+)add(18)(q11.2?), and the patient displayed severe oligozoospermia without other abnormalities. The two cases were verified by fluorescent in situ hybridization, and no abnormalities were found by genome-wide copy number variation analysis. To our knowledge, these two cases of complex autosomal karyotypes have not been reported previously. Although rare, these cases suggest that complex balanced translocations may be important causes of oligozoospermia. We speculate that the balanced translocation hinders germ cell meiosis and causes impaired spermatogenesis. Accordingly, the two reported patients have very low probabilities of giving birth to a normal child; therefore, we suggest choosing donor semen or adopting a child.

Association of T/A polymorphism in miR-1302 binding site in CGA gene with male infertility in Isfahan population

Infertility occurs in 10-15% of couples worldwide and close to half of it is caused by male factors. One of the genes that can affect male infertility is CGA. Polymorphisms in CGA gene may affect gene expression, therefore affecting male infertility by disrupting the regulation of this gene. One of the polymorphisms is the substitution of T with A in the miR-1302 binding site in the 3' untranslated region of the CGA gene. In this study, we explored this polymorphism in Isfahan population. In this case-control study, by the use of Tetra primer-ARMS-PCR technique, rs6631 has been investigated in 224 infertile men and 196 controls. Infertile men were recruited from Isfahan Fertility and Infertility Center. Analysis of genotype and allele frequencies indicated that the differences between case and control populations were significant for rs6631 because P = 0.00 which is above the threshold. We found a significant relationship between this polymorphism and male infertility. This study which performed for the first time in Iran suggests that polymorphism in CGA gene can affect male infertility. Also, this polymorphism has high heterozygosity, so it can be used for further studies in different populations.

SPINK2 deficiency causes infertility by inducing sperm defects in heterozygotes and azoospermia in homozygotes

Azoospermia, characterized by the absence of spermatozoa in the ejaculate, is a common cause of male infertility with a poorly characterized etiology. Exome sequencing analysis of two azoospermic brothers allowed the identification of a homozygous splice mutation in SPINK2, encoding a serine protease inhibitor believed to target acrosin, the main sperm acrosomal protease. In accord with these findings, we observed that homozygous Spink2 KO male mice had azoospermia. Moreover, despite normal fertility, heterozygous male mice had a high rate of morphologically abnormal spermatozoa and a reduced sperm motility. Further analysis demonstrated that in the absence of Spink2, protease-induced stress initiates Golgi fragmentation and prevents acrosome biogenesis leading to spermatid differentiation arrest. We also observed a deleterious effect of acrosin overexpression in HEK cells, effect that was alleviated by SPINK2 coexpression confirming its role as acrosin inhibitor. These results demonstrate that SPINK2 is necessary to neutralize proteases during their cellular transit toward the acrosome and that its deficiency induces a pathological continuum ranging from oligoasthenoteratozoospermia in heterozygotes to azoospermia in homozygotes.

Decreased Expression of CDC25A in Azoospermia as the Etiology of Spermatogenesis Failure

BACKGROUND

Spermatogenesis is a tightly regulated developmental process of male germ cells. The stages in spermatogenesis are mitosis, meiosis and spermiogenesis. One of the genes playing a role in meiosis is Cell Division Cycle 25A (CDC25A). Decreased expression of CDC25A is associated with failure of spermatogenesis and sperm retrieval. Infertility examination for azoospermia has been limited on histological examination. Hence, molecular research to find marker genes for infertility will improve the examination of testis biopsies.

METHODS

This research is a cross sectional study of 50 testicular biopsies with Johnsen scoring categories from scoring 2 to 8. Analysis of mRNA expression used qPCR and protein expression using immunohistochemistry. Statistical analysis with Spearman correlation was considered significant at p<0.05.

RESULTS

The result showed that transcript level and protein expression of CDC25A decreased in score 5 of Johnsen scoring categories. Moderate Spearman rho correlation (r=0.546) between mRNA relative expression and protein expression of CDC25A was significant at p<0.01.

CONCLUSION

Decreased expression of CDC25A is associated with meiotic arrest as the etiology of spermatogenic failure in many azoospermic men.

A systematic review on the genetics of male infertility in the era of next-generation sequencing

OBJECTIVES

To identify the role of next-generation sequencing (NGS) in male infertility, as advances in NGS technologies have contributed to the identification of novel genes responsible for a wide variety of human conditions and recently has been applied to male infertility, allowing new genetic factors to be discovered.

MATERIALS AND METHODS

PubMed was searched for combinations of the following terms: 'exome', 'genome', 'panel', 'sequencing', 'whole-exome sequencing', 'whole-genome sequencing', 'next-generation sequencing', 'azoospermia', 'oligospermia', 'asthenospermia', 'teratospermia', 'spermatogenesis', and 'male infertility', to identify studies in which NGS technologies were used to discover variants causing male infertility.

RESULTS

Altogether, 23 studies were found in which the primary mode of variant discovery was an NGS-based technology. These studies were mostly focused on patients with quantitative sperm abnormalities (non-obstructive azoospermia and oligospermia), followed by morphological and motility defects. Combined, these studies uncover variants in 28 genes causing male infertility discovered by NGS methods.

CONCLUSIONS

Male infertility is a condition that is genetically heterogeneous, and therefore remarkably amenable to study by NGS. Although some headway has been made, given the high incidence of this condition despite its detrimental effect on reproductive fitness, there is significant potential for further discoveries.

Genetics of the human Y chromosome and its association with male infertility

The human Y chromosome harbors genes that are responsible for testis development and also for initiation and maintenance of spermatogenesis in adulthood. The long arm of the Y chromosome (Yq) contains many ampliconic and palindromic sequences making it predisposed to self-recombination during spermatogenesis and hence susceptible to intra-chromosomal deletions. Such deletions lead to copy number variation in genes of the Y chromosome resulting in male infertility. Three common Yq deletions that recur in infertile males are termed as AZF (Azoospermia Factor) microdeletions viz. AZFa, AZFb and AZFc. As estimated from data of nearly 40,000 Y chromosomes, the global prevalence of Yq microdeletions is 7.5% in infertile males; however the European infertile men are less susceptible to Yq microdeletions, the highest prevalence is in Americans and East Asian infertile men. In addition, partial deletions of the AZFc locus have been associated with infertility but the effect seems to be ethnicity dependent. Analysis of > 17,000 Y chromosomes from fertile and infertile men has revealed an association of gr/gr deletion with male infertility in Caucasians and Mongolian men, while the b2/b3 deletion is associated with male infertility in African and Dravidian men. Clinically, the screening for Yq microdeletions would aid the clinician in determining the cause of male infertility and decide a rational management strategy for the patient. As these deletions are transmitted to 100% of male offspring born through assisted reproduction, testing of Yq deletions will allow the couples to make an informed choice regarding the perpetuation of male infertility in future generations. With the emerging data on association of Yq deletions with testicular cancers and neuropsychiatric conditions long term follow-up data is urgently needed for infertile men harboring Yq deletions. If found so, the information will change the current the perspective of androgenetics from infertility and might have broad implication in men health.

Partial Deletions of Y-Chromosome in Infertile Men with Non-obstructive Azoospermia and Oligoasthenoteratozoospermia in a Turkish Population

Many genetic alterations have been identified to aid in understanding the genetic basis of male infertility, however, the cause of 30% of male infertility remains unknown. Some studies indicated that subdeletions of Y chromosome may be a reason for male infertility caused by testicular failure. In this regard, we aimed to investigate frequency of AZFc region subdeletions and their clinical effects in patients with idiopathic infertility. A total of 333 male infertile patients with non-obstructive azoospermia (NOA) or oligoasthenoteratozoospermia (OAT), and 87 normozoospermic controls were screened to detect gr/gr, b1/b3 and b2/b3 subdeletions. We recorded higher gr/gr deletion frequency in normozoospermic controls compared NAO and OAT groups (p=0.026). There were no significant differences in b2/b3 subdeletion rates among groups (p=0.437). In the OAT group, follicle-stimulating hormone levels of cases with b2/b3 deletion were statistically lower than cases without b2/b3 deletion (p=0.047). No statistical correlations were indicated among subdeletions, sperm count and assisted reproductive technology (ART) outcomes. These data demonstrate that gr/gr and b2/b3 subdeletions may not play a significant role in the etiopathogenesis of male infertility and ART outcomes in the studied population.

Next-generation sequencing for patients with non-obstructive azoospermia: implications for significant roles of monogenic/oligogenic mutations

Azoospermia affects up to 1% of adult men. Non-obstructive azoospermia is a multifactorial disorder whose molecular basis remains largely unknown. To date, mutations in several genes and multiple submicroscopic copy-number variations (CNVs) have been identified in patients with non-obstructive azoospermia. The aim of this study was to clarify the contribution of nucleotide substitutions in known causative genes and submicroscopic CNVs in the genome to the development of non-obstructive azoospermia. To this end, we conducted sequence analysis of 25 known disease-associated genes using next-generation sequencing and genome-wide copy-number analysis using array-based comparative genomic hybridization. We studied 40 Japanese patients with idiopathic non-obstructive azoospermia. Functional significance of molecular alterations was assessed by in silico analyses. As a result, we identified four putative pathogenic mutations, four rare polymorphisms possibly associated with disease risk, and four probable neutral variants in 10 patients. These sequence alterations included a heterozygous splice site mutation in SOHLH1 and a hemizygous missense substitution in TEX11, which have been reported as causes of non-obstructive azoospermia. Copy-number analysis detected five X chromosomal or autosomal CNVs of unknown clinical significance, in addition to one known pathogenic Y chromosomal microduplication. Five patients carried multiple molecular alterations. The results indicate that monogenic and oligogenic mutations, including those in SOHLH1 and TEX11, account for more than 10% of cases of idiopathic non-obstructive azoospermia. Furthermore, this study suggests possible contributions of substitutions in various genes as well as submicroscopic CNVs on the X chromosome and autosomes to non-obstructive azoospermia, which require further validation.

Investigation of piwi-interacting RNA pathway genes role in idiopathic non-obstructive azoospermia

Genes involved in piwi-interacting RNAs (piRNAs) pathway have an essential role in spermatogenesis. HIWI and TDRD proteins are critical for piRNA biogenesis and function. Therefore, Mutations and polymorphisms in HIWI and TDRD genes may play role in male infertility. The aim of the present study was to investigate the role of HIWI2 rs508485 (T>C) and HIWI3 rs11703684 (C>T) polymorphisms and mutational analysis of TDRD5 gene in idiopathic non-obstructive azoospermia in a case-control study including 226 non-obstructive azoospermia patients and 200 fertile males. Genotyping for both polymorphisms was performed using Tetra-Primer ARMS PCR. Mutation analysis of TDRD5 gene was done using multi-temperature single strand conformation polymorphism technique (MSSCP). The frequency of rs508485TC genotype was significantly different in the studied groups (P = 0.0032; OR = 2.12; 95% CI, 1.29-3.48). In addition, the genotype frequencies showed a significant difference under dominant model (P = 0.005; OR = 2.79; 95% CI, 1.22-3.13). No mutation was detected in the Tudor domain of the TDRD5 in the studied patients. In conclusion, we provide evidence for association between genetic variation in the HIWI2 gene and idiopathic non-obstructive azoospermia in Iranian patients. Therefore, piRNA pathway genes variants can be considered as risk factors for male infertility.