Mutational screening of the NR5A1 in azoospermia

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.

Targeted next-generation sequencing panel screening of 668 Chinese patients with non-obstructive azoospermia

PURPOSE

We aimed (1) to determine the molecular diagnosis rate and the recurrent causative genes of patients with non-obstructive azoospermia (NOA) using targeted next-generation sequencing (NGS) panel screening and (2) to discuss whether these genes help in the prognosis for microsurgical testicular sperm extraction (micro-TESE).

METHODS

We used NGS panels to screen 668 Chinese men with NOA. Micro-TESE outcomes for six patients with pathogenic mutations were followed up. Functional assays were performed for two NR5A1 variants identified: p.I224V and p.R281C.

RESULTS

Targeted NGS panel sequencing could explain 4/189 (2.1% by panel 1) or 10/479 (2.1% by panel 2) of the patients with NOA after exclusion of karyotype abnormalities and Y chromosome microdeletions. Almost all mutations detected were newly described except for NR5A1 p.R281C and TEX11 p.M156V. Two missense NR5A1 mutations-p.R281C and p.I244V-were proved to be deleterious by in vitro functional assays. Mutations in TEX11, TEX14, and NR5A1 genes are recurrent causes of NOA, but each gene explains only a very small percentage (less than 4/668; 0.6%). Only the patient with NR5A1 mutations produced viable spermatozoa through micro-TESE, but other patients with TEX11 and TEX14 had poor micro-TESE prognoses.

CONCLUSIONS

A targeted NGS panel is a feasible diagnostic method for patients with NOA. Because each gene implicated explains only a small proportion of such cases, more genes should be included to further increase the diagnostic rate. Considering previous reports, we suggest that only a few genes that are directly linked to meiosis can indicate poor micro-TESE prognosis, such as TEX11, TEX14, and SYCE1.

Genetics of Azoospermia

Azoospermia affects 1% of men, and it can be due to: (i) hypothalamic-pituitary dysfunction, (ii) primary quantitative spermatogenic disturbances, (iii) urogenital duct obstruction. Known genetic factors contribute to all these categories, and genetic testing is part of the routine diagnostic workup of azoospermic men. The diagnostic yield of genetic tests in azoospermia is different in the different etiological categories, with the highest in Congenital Bilateral Absence of Vas Deferens (90%) and the lowest in Non-Obstructive Azoospermia (NOA) due to primary testicular failure (~30%). Whole-Exome Sequencing allowed the discovery of an increasing number of monogenic defects of NOA with a current list of 38 candidate genes. These genes are of potential clinical relevance for future gene panel-based screening. We classified these genes according to the associated-testicular histology underlying the NOA phenotype. The validation and the discovery of novel NOA genes will radically improve patient management. Interestingly, approximately 37% of candidate genes are shared in human male and female gonadal failure, implying that genetic counselling should be extended also to female family members of NOA patients.

Male Infertility Knowledgebase: decoding the genetic and disease landscape

Male infertility is a multifactorial condition that contributes to around one-third of cases of infertility worldwide. Several chromosomal aberrations, single-gene and polygenic associations with male factor defects have been reported. These defects manifest as sperm number or sperm quality defects leading to infertility. However, in almost 40% of cases, the genetic etiology of male infertility remains unexplained. Understanding the causal genetic factors is crucial for effective patient management and counseling. Integrating the vast amount of available omics data on male infertility is a first step towards understanding, delineating and prioritizing genes associated with the different male reproductive disorders. The Male Infertility Knowledgebase (MIK) is a manually curated repository developed to boost research on the elusive genetic etiology of male infertility. It integrates information on ∼17 000 genes, their associated pathways, gene ontology, diseases and gene and sequence-based analysis tools. In addition, it also incorporates information on reported chromosomal aberrations and syndromic associations with male infertility. Disease enrichment of genes in MIK indicate a shared genetic etiology between cancer, male and female infertility disorders. While the genes involved in cancer pathways were found to be common causal factors for sperm number and sperm quality defects, the interleukin pathways were found to be shared and enriched between male factor defects and non-reproductive conditions like cardiovascular diseases, metabolic diseases, etc. Disease information in MIK can be explored further to identify high-risk conditions associated with male infertility and delineate shared genetic etiology. Utility of the knowledgebase in predicting novel genes is illustrated by identification of 149 novel candidates for cryptorchidism using gene prioritization and network analysis. MIK will serve as a platform for review of genetic information on male infertility, identification pleiotropic genes, prediction of novel candidate genes for the different male infertility diseases and for portending future high-risk diseases associated with male infertility.

Database URL: http://mik.bicnirrh.res.in/

Next-generation sequencing: toward an increase in the diagnostic yield in patients with apparently idiopathic spermatogenic failure

A large proportion of patients with idiopathic spermatogenic failure (SPGF; oligozoospermia or nonobstructive azoospermia [NOA]) do not receive a diagnosis despite an extensive diagnostic workup. Recent evidence has shown that the etiology remains undefined in up to 75% of these patients. A number of genes involved in germ-cell proliferation, spermatocyte meiotic divisions, and spermatid development have been called into play in the pathogenesis of idiopathic oligozoospermia or NOA. However, this evidence mainly comes from case reports. Therefore, this study was undertaken to identify the molecular causes of SPGF. To accomplish this, 15 genes (USP9Y, NR5A1, KLHL10, ZMYND15, PLK4, TEX15, TEX11, MEIOB, SOHLH1, HSF2, SYCP3, TAF4B, NANOS1, SYCE1, and RHOXF2) involved in idiopathic SPGF were simultaneously analyzed in a cohort of 25 patients with idiopathic oligozoospermia or NOA, accurately selected after a thorough diagnostic workup. After next-generation sequencing (NGS) analysis, we identified the presence of rare variants in the NR5A1 and TEX11 genes with a pathogenic role in 3/25 (12.0%) patients. Seventeen other different variants were identified, and among them, 13 have never been reported before. Eleven out of 17 variants were likely pathogenic and deserve functional or segregation studies. The genes most frequently mutated were MEIOB, followed by USP9Y, KLHL10, NR5A1, and SOHLH1. No alterations were found in the SYCP3, TAF4B, NANOS1, SYCE1, or RHOXF2 genes. In conclusion, NGS technology, by screening a specific custom-made panel of genes, could help increase the diagnostic rate in patients with idiopathic oligozoospermia or NOA.

Genetic Landscape of Nonobstructive Azoospermia and New Perspectives for the Clinic

Nonobstructive azoospermia (NOA) represents the most severe expression of male infertility, involving around 1% of the male population and 10% of infertile men. This condition is characterised by the inability of the testis to produce sperm cells, and it is considered to have an important genetic component. During the last two decades, different genetic anomalies, including microdeletions of the Y chromosome, karyotype defects, and missense mutations in genes involved in the reproductive function, have been described as the primary cause of NOA in many infertile men. However, these alterations only explain around 25% of azoospermic cases, with the remaining patients showing an idiopathic origin. Recent studies clearly suggest that the so-called idiopathic NOA has a complex aetiology with a polygenic inheritance, which may alter the spermatogenic process. Although we are far from a complete understanding of the molecular mechanisms underlying NOA, the use of the new technologies for genetic analysis has enabled a considerable increase in knowledge during the last years. In this review, we will provide a comprehensive and updated overview of the genetic basis of NOA, with a special focus on the possible application of the recent insights in clinical practice.

Recent advances in mammalian reproductive biology

Reproductive biology is a uniquely important topic since it is about germ cells, which are central for transmitting genetic information from generation to generation. In this review, we discuss recent advances in mammalian germ cell development, including preimplantation development, fetal germ cell development and postnatal development of oocytes and sperm. We also discuss the etiologies of female and male infertility and describe the emerging technologies for studying reproductive biology such as gene editing and single-cell technologies.

Monogenic Forms of Male Infertility

Male infertility is a multifactorial and heterogeneous pathological condition affecting 7% of the general male population. The genetic landscape of male infertility is highly complex as semen and testis histological phenotypes are extremely heterogeneous, and at least 2000 genes are predicted to be involved in spermatogenesis. Genetic factors have been described in each etiological category of male reproductive impairment: (1) hypothalamic-pituitary axis dysfunction; (2) quantitative and qualitative alterations of spermatogenesis; (3) ductal obstruction/dysfunction. In 25% of azoospermic and in 10% of oligozoospermic men, a genetic anomaly can be diagnosed with the current genetic testing. However, up to now, only a relatively low number of monogenic factors have a clear-cut cause-effect relationship with impaired reproductive function. Thanks to the widespread diffusion of Next-Generation Sequencing, a continuously increasing number of monogenic causes of male infertility are being discovered and their validation is currently ongoing. The identification of genetic factors is of outmost clinical importance since there is a risk of transmission of genetic defects through natural or assisted reproductive techniques. The benefit of the genetic diagnosis of infertility has an obvious clinical significance for the patient itself with implications not only for his reproductive health but in many instances also for his general health.

NR5A1 mutations are not associated with male infertility in Indian men

NR5A1 or steroidogenic factor 1 (SF1) is an autosomal gene, which encodes a protein that is a member of nuclear receptor family. NR5A1 regulates the transcription of numerous genes that are expressed in hypothalamic-pituitary-gonadal axis and adrenal cortex which in turn, coordinate the gonadal development, steroidogenesis and sex differentiation. Several mutations in NR5A1 have been reported to cause gonadal dysgenesis with adrenal insufficiency in individuals with 46,XY karyotype. However, studies in the past few years have shown that NR5A1 mutations can also contribute to primary ovarian insufficiency and impaired spermatogenesis. As there is no genetic study on NR5A1 in Indian infertile men, we have sequenced the entire coding region (exons 2-7) of NR5A1 in 502 infertile men of which, 414 were non-obstructive azoospermic and 88 severe oligozoospermic, along with 427 ethnically matched fertile controls. Interestingly, none of the mutations reported to be associated with male infertility were found in our study, except one polymorphism, rs1110061. However, it was not significantly different between infertile and fertile groups (p = .76). In addition, we have identified six intronic variants; but none of them was significantly associated with male infertility.

Glucose-6-phosphate dehydrogenase deficiency does not increase the susceptibility of sperm to oxidative stress induced by H2O2

Objective

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect. G6PD plays a key role in the pentose phosphate pathway, which is a major source of nicotinamide adenine dinucleotide phosphate (NADPH). NADPH provides the reducing equivalents for oxidation-reduction reductions involved in protecting against the toxicity of reactive oxygen species such as H₂O₂. We hypothesized that G6PD deficiency may reduce the amount of NADPH in sperms, thereby inhibiting the detoxification of H₂O₂, which could potentially affect their motility and viability, resulting in an increased susceptibility to infertility.

Methods

Semen samples were obtained from four males with G6PD deficiency and eight healthy males as a control. In both groups, motile sperms were isolated from the seminal fluid and incubated with 0, 10, 20, 40, 60, 80, and 120 µM concentrations of H₂O₂. After 1 hour incubation at 37℃, sperms were evaluated for motility and viability.

Results

Incubation of sperms with 10 and 20 µM H₂O₂ led to very little decrease in motility and viability, but motility decreased notably in both groups in 40, 60, and 80 µM H₂O₂, and viability decreased in both groups in 40, 60, 80, and 120 µM H₂O₂. However, no statistically significant differences were found between the G6PD-deficient group and controls.

Conclusion

G6PD deficiency does not increase the susceptibility of sperm to oxidative stress induced by H₂O₂, and the reducing equivalents necessary for protection against H₂O₂ are most likely produced by other pathways. Therefore, G6PD deficiency cannot be considered as major risk factor for male infertility.