Deepika Jaiswal

Human Male Infertility: A Complex Multifactorial Phenotype

Infertility is a major reproductive health problem affecting 10% to 15% of couples, with approximately equal contributions. Spermatogenesis is a dynamic and multistep process of male germ cell proliferation and differentiation by which spermatozoa are produced from primordial germ cells. The causes of spermatogenic defects in infertile men are multifactorial and many environmental, nutritional, behavioral and genetic factors affect male infertility. In most of the infertile cases, the underlying mechanisms remain obscure. Genomics and proteomics offer new tools for better understanding the genetics of male infertility. The current review provides insights into the plausible chromosomal, genetic and epigenetic alterations, which may result into infertile phenotype.

One-Carbon Metabolism, Spermatogenesis, and Male Infertility

Balanced diet is the natural source of micronutrients, such as folate and vitamins, vital for proper functioning of the body. One-carbon metabolic pathway along with folate and other vitamins plays an important role in DNA synthesis and in the establishment of epigenetic modifications like DNA/histone methylation. Spermatogenesis involves distinct cellular, genetic, and chromatin changes during the course of production of male gamete sperm. Folate and normal activity of 1-carbon metabolic pathway enzymes are central to nucleotide synthesis, methylation, and maintenance of genomic integrity as well as protection from DNA damage. As a result, polymorphisms in 1-carbon metabolic pathway genes affecting several physiological processes also have an impact on spermatogenesis and may affect directly or indirectly quality of sperm. Alterations in these processes may be a consequence of additive effect resulting from altered expression of 1-carbon metabolic pathway genes and/or inadequate folate/micronutrients supplementation. The present review provides an overview of different cellular and molecular events regulated by 1-carbon metabolic pathway enzymes and their impact on male reproductive health. It also summarizes the different studies where polymorphisms in the enzymes of 1-carbon metabolic pathway or folate deficiency are associated with male infertility and future prospects.

Combined Effect of GSTT1 and GSTM1 Polymorphisms on Human Male Infertility in North Indian Population

Genes of different pathways regulate spermatogenesis, and complexity of spermatogenic process indicates that polymorphisms or mutations in these genes could cause male infertility. Detoxification pathway is involved in the regulation of spermatogenesis by reducing oxidative stress and contributes to the maintenance of global methylation in concert with other pathways. Glutathione S-transferases (GSTs) belong to the family of phase II antioxidant enzymes involved in the cellular detoxification of various physiological substances. Glutathione S-transferases act as an antioxidant and protect spermatozoa from oxidative stress. Increase in the levels of reactive oxygen species (ROS) along with reduced activity of GSTs may result in sperm membrane damage and DNA fragmentation. A case–control study was done to elucidate the role of deletion polymorphism of GSTT1 and GSTM1 genes from GSTs family on idiopathic human male infertility. The study comprises 2 groups: 113 nonobstructive azoospermia patients and 91 healthy fertile controls. Genomic DNA was analyzed by polymerase chain reaction for GSTT1 and GSTM1 genes. The study showed statistically significant protective association of GSTT1 null genotype with human male infertility (odds ratio [OR]: 0.3, 95% confidence interval [CI] 0.143-0.9966, P = .048) but not with GSTM1 null genotype (OR: 0.66, 95% CI 0.3653-1.2234, P = .19). Also, combination of null genotypes of GSTM1 and GSTT1 confers protective effect (OR: 0.28, CI 0.0801-0.948; P = .04). Probably, individuals bearing GSTM1 and GSTT1 (−/−) genotypes may have protective effect by gene–gene interaction mechanism. In summary, our study underscores the significance of combined effect of GSTT1 and GSTM1 null genotypes in modulating the risk of male infertility.

Gr/gr deletions on Y-chromosome correlate with male infertility: an original study, meta-analyses, and trial sequential analyses.

We analyzed the AZFc region of the Y-chromosome for complete (b2/b4) and distinct partial deletions (gr/gr, b1/b3, b2/b3) in 822 infertile and 225 proven fertile men. We observed complete AZFc deletions in 0.97% and partial deletions in 6.20% of the cases. Among partial deletions, the frequency of gr/gr deletions was the highest (5.84%). The comparison of partial deletion data between cases and controls suggested a significant association of the gr/gr deletions with infertility (P = 0.0004); however, the other partial deletions did not correlate with infertility. In cohort analysis, men with gr/gr deletions had a relatively poor sperm count (54.20 ± 57.45 million/ml) in comparison to those without deletions (72.49 ± 60.06), though the difference was not statistically significant (p = 0.071). Meta-analysis also suggested that gr/gr deletions are significantly associated with male infertility risk (OR = 1.821, 95% CI = 1.39–2.37, p = 0.000). We also performed trial sequential analyses that strengthened the evidence for an overall significant association of gr/gr deletions with the risk of male infertility. Another meta-analysis suggested a significant association of the gr/gr deletions with low sperm count. In conclusion, the gr/gr deletions show a strong correlation with male infertility risk and low sperm count, particularly in the Caucasian populations.

Chromosome microarray analysis: a case report of infertile brothers with CATSPER gene deletion.

We present the case of two brothers who were referred to a male infertility clinic for infertility workup. Conventional chromosome analysis and Y chromosome microdeletions did not reveal any genetic alterations. We utilized the chromosome microarray analysis (CMA) to identify novel and common variations associated with this severely impaired spermatogenesis cases. CMA specific results showed a common deletion in the 15q15.3 region that harbors genes like CATSPER2, STRC and PPIP5K1 in both cases (M18 and M19). In addition we identified small duplication in X and 11 chromosomes of M19. This is the first familial case report from India on occurrence of CATSPER gene deletion in human male infertility.

Association of the IL1RN Gene VNTR Polymorphism with Human Male Infertility

Interleukin-1 (IL-1) is a regulatory cytokine that plays an important role in the maintenance of the immune environment of the testis, regulation of junction dynamics and cell differentiation during spermatogenesis. Members of the IL-1 family are pleiotropic cytokines that are involved in inflammation, immunoregulation and other homeostatic functions in the body. IL-1α, IL-1β, and the IL-1 receptor antagonistic molecule (IL-1 Ra) are expressed in the testis under normal homeostasis and they further increase upon infection/inflammation. In the present study we have examined the association of Variable Number Tandem Repeats (VNTR) polymorphism of the Interleukin-1 receptor antagonist gene (IL1RN) with human male infertility. The case-control study comprised of two groups: 331 idiopathic infertile patients and 358 fertile healthy men. The study indicates risk of IL1RN2 variant with male infertility (OR: 1.43, CI: 1.1546 to 1.7804, P = 0.001). To our best knowledge, this is the first report that links IL1RN VNTR polymorphism with human male infertility.

FAS-670 A/G and FAS-1377 G/A polymorphism in cell death pathway gene FAS and human male infertility

Abstract Objective To study the role and association of functional variations present in FAS gene with idiopathic male infertility. Methods The case-control study comprised of two groups: 160 idiopathic infertile nonobstructive azoospermia patients and 200 fertile healthy control men. Genotyping for single-nucleotide polymorphism of FAS -670 A/G (rs1800682) and FAS -1377 G/A (rs2234767) was done by PCR-RFLP method. DNA sequencing was used to ascertain PCR-RFLP results. For FAS -670 A/G and FAS -1377 G/A functional polymorphism, allele and genotype distribution were evaluated using Chi-square test. Results Allele and genotype distribution did not differ significantly between patients and controls for FAS -670 A/G and FAS -1377 G/A. Conclusions Human male infertility is a complex disorder and thus other genetic or environmental factors may be contributing to the complex etiology.

Association of interleukin-1beta C + 3953T gene polymorphism with human male infertility

Cytokines are involved in the regulation of spermatogenesis likely mediating the crosstalk among Sertoli and germ cells to facilitate germ cell movement across the seminiferous epithelium during cellular events such as germ cell differentiation. Members of the Interleukin-1 (IL-1) family are pleiotropic cytokines that are involved in inflammation, immunoregulation, and other homeostatic functions. Interleukin-1 alpha (IL-1α), IL-1β, and the IL-1 antagonistic molecule (IL-1 Ra) are present in the testis under normal homeostasis and they further increase upon infection/inflammation. In the present study we have examined the association of C + 3953T polymorphism of the human IL-1B gene with human male infertility. The case control study comprised of two groups: 222 infertile patients and 230 fertile healthy control men. Genotyping for SNP C + 3953T IL-1B was carried out by polymerase chain reaction followed by analysis with specific endonucleases (PCR-RFLP). DNA sequencing was used to validate the PCR-RFLP results. The genotype frequencies of the IL-1B Taq C/T polymorphism were compared between infertile men and controls. The frequency was significantly higher in asthenozoospermic patients compared to fertile control men (odds ratio = 10.4, CI: 2.50- 43.96, p = 0.001). The C + 3953T of the IL-1B gene is associated with male infertility risk in the asthenozoospermic patients from an Indian population.

Association of polymorphism in cell death pathway gene FASLG with human male infertility

Abstract Objective To investigate –844C>T single nucleotide polymorphism (SNP) present in the promoter of cell death pathway gene FASLG with male infertile phenotype. Methods Genotyping for SNP FASLG (rs763110) was done by polymerase chain reaction followed by analysis with specific endonuclease (PCR-RFLP). DNA sequencing was used to ascertain PCR-RFLP results. Results FASLG –844C>T polymorphism, allele and genotype distribution did not differ significantly between patients and controls ( OR : 1.03, 95% CI = 0.7638 to 1.3952, P =0.83). Thus SNP-844C>T of the FASLG gene is not associated with male infertility risk in the analyzed patients. Conclusions Human male infertility is a complex disorder and thus other genetic or environmental factors may be contributing to the complex etiology, and further study in other region of Indian populations will verify whether it is associated with male infertility risk.

Association of the gonadotrophin‐regulated testicular RNA helicase gene polymorphism with human male infertility

Gonadotrophin‐regulated testicular RNA helicase (GRTH) plays an important role in RNA functions including nuclear transcription, pre‐mRNA splicing and it regulates the translation of specific genes required for the progression of spermatogenesis. In this study, we analysed the association of GRTH gene IVS6+55G/T and c.852C/T polymorphisms with human male infertility. The study showed c.852 T allele was associated with an increased risk of male infertility (OR: 3.16, P = 0.008), whereas IVS6+55G/T allele conferred no risk. In Indian population, this is the first report on association of GRTH gene SNP polymorphism and male infertility and it underscores the significance of GRTH genotypes in modulating the risk of male infertility.