Gene-environment interaction and male reproductive function

Organochlorine pesticide exposures, metabolic enzyme genetic polymorphisms and semen quality parameters among men attending an infertility clinic

The associations of organochlorine pesticides (OCPs) with semen quality from human studies are conflicting, and also it is largely unknown whether the associations are modified by genetic polymorphisms. We aimed to evaluate the associations between serum concentrations of 18 OCPs and semen quality among 387 Chinese men, and further to examine the modifying effects by genetic polymorphisms in cytochrome P450 (CYP2E1) and glutathione S-transferase (GSTT1). Multivariable linear regressions were used to evaluate the relationships between serum OCP concentrations and semen quality, and the role of CYP2E1 and GSTT1 polymorphisms in modifying the associations were assessed. Multiple testing was adjusted using the false discovery rate (FDR). We observed that men with detectable concentrations of serum ɤ-HCH had a decrease in sperm motility of 7.07% (95% CI: -10.9%, -3.24%) compared to those with undetectable concentrations (FDR-P value = 0.02). Men with TT of CYP2E1 rs 915906 genotypes had higher median concentrations of serum dieldrin compared with those with CT/CC of CYP2E1 rs 915906 genotypes. There were interactions between CYP2E1 and GSTT1 polymorphisms and certain OCPs namely ɤ-HCH, δ-HCH, dieldrin, endosulfan I, and endrin aldehyde on semen quality. For example, elevated dieldrin levels in relation to decreased sperm concentration, sperm count, and sperm motility were only observed among men with CC of CYP2E1 rs2031920 genotypes (all P_interaction < 0.05). However, these interactions were not statistically significant after the FDR adjustment. Our results suggested that CYP2E1 and GSTT1 polymorphisms may modify the effects of OCP exposures on semen quality. Due to the relatively small size samples, further investigation is warranted to confirm the findings.

Uncovering Evidence for Endocrine-Disrupting Chemicals That Elicit Differential Susceptibility through Gene-Environment Interactions

Exposure to endocrine-disrupting chemicals (EDCs) is linked to myriad disorders, characterized by the disruption of the complex endocrine signaling pathways that govern development, physiology, and even behavior across the entire body. The mechanisms of endocrine disruption involve a complex system of pathways that communicate across the body to stimulate specific receptors that bind DNA and regulate the expression of a suite of genes. These mechanisms, including gene regulation, DNA binding, and protein binding, can be tied to differences in individual susceptibility across a genetically diverse population. In this review, we posit that EDCs causing such differential responses may be identified by looking for a signal of population variability after exposure. We begin by summarizing how the biology of EDCs has implications for genetically diverse populations. We then describe how gene-environment interactions (GxE) across the complex pathways of endocrine signaling could lead to differences in susceptibility. We survey examples in the literature of individual susceptibility differences to EDCs, pointing to a need for research in this area, especially regarding the exceedingly complex thyroid pathway. Following a discussion of experimental designs to better identify and study GxE across EDCs, we present a case study of a high-throughput screening signal of putative GxE within known endocrine disruptors. We conclude with a call for further, deeper analysis of the EDCs, particularly the thyroid disruptors, to identify if these chemicals participate in GxE leading to differences in susceptibility.

Sperm viability varies with buffer and genotype in Drosophila melanogaster

Sperm quality, an important male fitness trait, is commonly compared between studies. However, few studies consider how genetic and environmental variation affect sperm quality, even in the genetic model Drosophila melanogaster. Here we show that sperm viability, the proportion of live sperm, differed across the genotypes Oregon-R, Dahomey, and Canton-S by more than 15%, and across buffers (phosphate-buffered saline (PBS), Grace's Medium and Drosophila Ringer solution) by more than 20%. In terms of genotype-buffer pair comparisons, nearly half of the comparisons would produce significant differences in sperm viability (15 in 36), or its temporal decrease in a stress medium (19 in 36). Grace's medium produced the longest-lived sperm in vitro and the smallest differences between genotypes, Drosophila Ringer Solution produced the shortest lifespan and the largest differences. Our results suggest that fly and other sperm researchers would benefit from a standardized protocol of measuring sperm viability.

[Candidate SNP-markers altering TBP binding affinity for promoters of the Y-linked genes CDY2A, SHOX, and ZFY are lowering many indexes of reproductive potential in men]

Репродуктивный потенциал – уровень физического и психического состояния организма, позволяю- щий при достижении социальной зрелости воспроизводить здоровое потомство. В узком биомедицинском смыс- ле определение включает комплекс функциональных показателей репродуктивной системы, но в более широком смысле его можно рассматривать как совокупность физиологических, поведенческих, адаптивных, ментальных, ан- тропометрических и генетических характеристик особи, способствующих размножению. Целью настоящей работы было расширить область применимости созданного ранее Web-сервиса SNP_TATA_Z-tester для поиска кандидатных маркеров однонуклеотидного полиморфизма (SNP) на хромосоме Y человека, связанных с мужским репродуктив- ным потенциалом (МРП). В поиске кандидатных SNP-маркеров для МРП мы сосредоточились на генах хромосомы Y человека. Изучены 35 SNP в промоторах генов CDY2A, SHOX и ZFY, представляющих все три типа генов хромосомы Y человека: уникальный, псевдоаутосомный и паралог гена хромосомы X человека соответственно. Предсказаны 11 кандидатных SNP-маркеров ослабления МРП из-за изменения сродства TATA-связывающего белка (TBP) к этим промоторам. Выборочно верифицированы in vitro величины сродства «TBP-промотор», предсказанные в этой рабо- те. Установлена достоверная корреляция (r = 0.94, p < 0.005) между ними и результатами измерения in vitro сродства ТВР человека к олигонуклеотидам, идентичным сайтам ТВР-связывания исследуемых промоторов. Проведя поиск в базе данных PubMed по ключевым словам, мы нашли клиническое описание патологических состояний человека, соответствующих изменению экспрессии генов, несущих предсказанные нами кандидатные SNP-маркеры. Среди них оказались такие патологии, как нарушение сперматогенеза (ZFY: rs1388535808 и rs996955491), задержка поло- вого созревания (CDY2A: rs200670724), нарушения эмбриогенеза (SHOX: rs28378830) и непропорционально низкий рост с деформациями Маделунга (SHOX: rs1452787381). Они свидетельствуют, что в случае SNP-промоторов генов хромосомы Y человека следует ожидать изменений широкого круга показателей МРП, выходящих далеко за рамки генетического контроля собственно мужской репродуктивной функции.

Disruptive natural selection by male reproductive potential prevents underexpression of protein-coding genes on the human Y chromosome as a self-domestication syndrome

Background

In population ecology, the concept of reproductive potential denotes the most vital indicator of chances to produce and sustain a healthy descendant until his/her reproductive maturity under the best conditions. This concept links quality of life and longevity of an individual with disease susceptibilities encoded by his/her genome. Female reproductive potential has been investigated deeply, widely, and comprehensively in the past, but the male one has not received an equal amount of attention. Therefore, here we focused on the human Y chromosome and found candidate single-nucleotide polymorphism (SNP) markers of male reproductive potential.

Results

Examining in silico (i.e., using our earlier created Web-service SNP_TATA_Z-tester) all 1206 unannotated SNPs within 70 bp proximal promoters of all 63 Y-linked genes, we found 261 possible male-reproductive-potential SNP markers that can significantly alter the binding affinity of TATA-binding protein (TBP) for these promoters. Among them, there are candidate SNP markers of spermatogenesis disorders (e.g., rs1402972626), pediatric cancer (e.g., rs1483581212) as well as male anxiety damaging family relationships and mother’s and children’s health (e.g., rs187456378). First of all, we selectively verified in vitro both absolute and relative values of the analyzed TBP–promoter affinity, whose Pearson’s coefficients of correlation between predicted and measured values were r = 0.84 (significance p <  0.025) and r = 0.98 (p <  0.025), respectively. Next, we found that there are twofold fewer candidate SNP markers decreasing TBP–promoter affinity relative to those increasing it, whereas in the genome-wide norm, SNP-induced damage to TBP–promoter complexes is fourfold more frequent than SNP-induced improvement (p <  0.05, binomial distribution). This means natural selection against underexpression of these genes. Meanwhile, the numbers of candidate SNP markers of an increase and decrease in male reproductive potential were indistinguishably equal to each other (p <  0.05) as if male self-domestication could have happened, with its experimentally known disruptive natural selection. Because there is still not enough scientific evidence that this could have happened, we discuss the human diseases associated with candidate SNP markers of male reproductive potential that may correspond to domestication-related disorders in pets.

Conclusions

Overall, our findings seem to support a self-domestication syndrome with disruptive natural selection by male reproductive potential preventing Y-linked underexpression of a protein.

Pesticide interactions and risks of sperm chromosomal abnormalities

Disentangling the separate and synergistic effects of chemicals poses methodological challenges for accurate exposure assessment and for investigating epidemiologically how chemicals affect reproduction. We investigated combined exposures to ubiquitous contemporary use pesticides, specifically organophosphates (OP) and pyrethroids (PYR), and their association with germ cell abnormalities among adult men. Fluorescence in situ hybridization was used to determine disomy in sperm nuclei and urine was analyzed for concentrations of PYR metabolites (3-phenoxybenzoic acid; 3PBA) and OP dialkyl phosphate (DAP) metabolites. Incidence rate ratios using Poisson models were estimated for each disomy type by exposure quartile of DAP metabolites and 3PBA, controlling for confounders. The shape of the associations between PYRs, OPs and disomy were frequently nonmonotonic. There were consistent interactions between OP and PYR metabolite concentrations and the risk for sperm abnormalities. Taking both chemicals into account simultaneously resulted in quantitatively different associations than what was reported previously for OPs and PYRs separately, demonstrating the importance of modeling multiple concentrations simultaneously. Methods investigating interactions using Poisson models are needed to better quantify chemical interactions and their effects on count-based health outcomes, the importance of which was shown here for germ cell abnormalities.

Trends of SHBG and ABP levels in male farmers: Influences of environmental fluoride exposure and ESR alpha gene polymorphisms

A number of epidemiological studies have reported that chronic exposure to high concentrations of fluoride not only causes dental and skeletal fluorosis but additionally affects serum levels of reproductive hormones. However, possible interaction between fluoride exposure and estrogen receptor alpha (ESRα) gene polymorphisms on sex hormone-binding globulin (SHBG) and androgen binding protein (ABP) of male farmers has not been detailed. Here, we conducted a cross-sectional study including 348 male farmers with different fluoride exposure levels from drinking water in Henan province of China to explore effects of fluoride exposure and ESRα genetic variation on serum SHBG and ABP levels. We found serum SHBG levels in male farmers from the high exposure group to be lower than those of the low exposure group. We also found that concentrations of SHBG affected ABP levels. Furthermore, fluoride exposure and single nucleotide polymorphisms at the XbaI and rs3798577 loci of the ESRα gene affected serum ABP levels. Our findings suggest that chronic fluoride exposure from drinking water is associated with alterations of serum SHBG and ABP concentrations in local male farmers and that the effect of fluoride exposure on ABP levels vary depending on ESRα gene polymorphisms.

Fit to father? Online accounts of lifestyle changes and help-seeking on a male infertility board

The reproductive realm is routinely viewed as a feminised space requiring women's commitment and labour. By contrast, men's procreative contributions and 'reproductive masculinity' is represented as unproblematic, with men assumed to be fertile across the lifespan. Recent scientific research has, however, cast doubt over these longstanding assumptions, suggesting that a link does exist between 'lifestyle' factors and male fertility. The notion that fertility can be improved with effort (for both women and men) can be located within wider cultural and political shifts which construct individuals as increasingly responsible for acting on health messages and engaging in self-disciplining body projects. Through an exploration of 'lifestyle changes' within a men's online infertility discussion forum board, this paper examines how discourses of individualisation healthism and masculinity are reproduced and interlinked. Our thematic analysis indicates that 'lifestyle work' is construed as crucial for achieving conception - and as a means to demonstrate men's commitment to the dyadic goal of parenthood, which in turn may challenge and extend previous notions of 'reproductive masculinity'.

Candidate SNP markers of reproductive potential are predicted by a significant change in the affinity of TATA-binding protein for human gene promoters

BACKGROUND

The progress of medicine, science, technology, education, and culture improves, year by year, quality of life and life expectancy of the populace. The modern human has a chance to further improve the quality and duration of his/her life and the lives of his/her loved ones by bringing their lifestyle in line with their sequenced individual genomes. With this in mind, one of genome-based developments at the junction of personalized medicine and bioinformatics will be considered in this work, where we used two Web services: (i) SNP_TATA_Comparator to search for alleles with a single nucleotide polymorphism (SNP) that alters the affinity of TATA-binding protein (TBP) for the TATA boxes of human gene promoters and (ii) PubMed to look for retrospective clinical reviews on changes in physiological indicators of reproductive potential in carriers of these alleles.

RESULTS

A total of 126 SNP markers of female reproductive potential, capable of altering the affinity of TBP for gene promoters, were found using the two above-mentioned Web services. For example, 10 candidate SNP markers of thrombosis (e.g., rs563763767) can cause overproduction of coagulation inducers. In pregnant women, Hughes syndrome provokes thrombosis with a fatal outcome although this syndrome can be diagnosed and eliminated even at the earliest stages of its development. Thus, in women carrying any of the above SNPs, preventive treatment of this syndrome before a planned pregnancy can reduce the risk of death. Similarly, seven SNP markers predicted here (e.g., rs774688955) can elevate the risk of myocardial infarction. In line with Bowles' lifespan theory, women carrying any of these SNPs may modify their lifestyle to improve their longevity if they can take under advisement that risks of myocardial infarction increase with age of the mother, total number of pregnancies, in multiple pregnancies, pregnancies under the age of 20, hypertension, preeclampsia, menstrual cycle irregularity, and in women smokers.

CONCLUSIONS

According to Bowles' lifespan theory-which links reproductive potential, quality of life, and life expectancy-the above information was compiled for those who would like to reduce risks of diseases corresponding to alleles in own sequenced genomes. Candidate SNP markers can focus the clinical analysis of unannotated SNPs, after which they may become useful for people who would like to bring their lifestyle in line with their sequenced individual genomes.

Gene-environment interaction: Does fluoride influence the reproductive hormones in male farmers modified by ERα gene polymorphisms?

The occurrence of endemic fluorosis is derived from high fluoride levels in drinking water and industrial fumes or dust. Reproductive disruption is also a major harm caused by fluoride exposure besides dental and skeletal lesions. However, few studies focus on the mechanism of fluoride exposure on male reproductive function, especially the possible interaction of fluoride exposure and gene polymorphism on male reproductive hormones. Therefore, we conducted a cross-sectional study in rural areas of Henan province in China to explore the interaction between the estrogen receptor alpha (ERα) gene and fluoride exposure on reproductive hormone levels in male farmers living in the endemic fluorosis villages. The results showed that fluoride exposure significantly increased the serum level of estradiol in the hypothalamic-pituitary-testicular (HPT) axis in male farmers. Moreover, the observations indicated that fluoride exposure and genetic markers had an interaction on serum concentration of follicle-stimulating hormone and estradiol, and the interaction among different loci of the ERα gene could impact the serum testosterone level. Findings in the present work suggest that chronic fluoride exposure in drinking water could modulate the levels of reproductive hormones in males living in endemic fluorosis areas, and the interaction between fluoride exposure and ERα polymorphisms might affect the serum levels of hormones in the HPT axis in male farmers.

An Ecology of Sperm: Sperm Diversification by Natural Selection

Using basic ecological concepts, we introduce sperm ecology as a framework to study sperm cells. First, we describe environmental effects on sperm and conclude that evolutionary and ecological research should not neglect the overwhelming evidence presented here (both in external and internal fertilizers and in terrestrial and aquatic habitats) that sperm function is altered by many environments, including the male environment. Second, we determine that the evidence for sperm phenotypic plasticity is overwhelming. Third, we find that genotype-by-environment interaction effects on sperm function exist, but their general adaptive significance (e.g., local adaptation) awaits further research. It remains unresolved whether sperm diversification occurs by natural selection acting on sperm function or by selection on male and female microenvironments that enable optimal plastic performance of sperm (sperm niches). Environmental effects reduce fitness predictability under sperm competition, predict species distributions under global change, explain adaptive behavior, and highlight the role of natural selection in behavioral ecology and reproductive medicine.

Dialkyl phosphate urinary metabolites and chromosomal abnormalities in human sperm

BACKGROUND

The past decade has seen numerous human health studies seeking to characterize the impacts of environmental exposures, such as organophosphate (OP) insecticides, on male reproduction. Despite an extensive literature on OP toxicology, many hormone-mediated effects on the testes are not well understood.

OBJECTIVES

This study investigated environmental exposures to OPs and their association with the frequency of sperm chromosomal abnormalities (i.e., disomy) among adult men.

METHODS

Men (n=159) from a study assessing the impact of environmental exposures on male reproductive health were included in this investigation. Multi-probe fluorescence in situ hybridization (FISH) for chromosomes X, Y, and 18 was used to determine XX18, YY18, XY18 and total disomy in sperm nuclei. Urine was analyzed using gas chromatography coupled with mass spectrometry for concentrations of dialkyl phosphate (DAP) metabolites of OPs [dimethylphosphate (DMP); dimethylthiophosphate (DMTP); dimethyldithiophosphate (DMDTP); diethylphosphate (DEP); diethylthiophosphate (DETP); and diethyldithiophosphate (DEDTP)]. Poisson regression was used to model the association between OP exposures and disomy measures. Incidence rate ratios (IRRs) were calculated for each disomy type by exposure quartiles for most metabolites, controlling for age, race, BMI, smoking, specific gravity, total sperm concentration, motility, and morphology.

RESULTS

A significant positive trend was seen for increasing IRRs by exposure quartiles of DMTP, DMDTP, DEP and DETP in XX18, YY18, XY18 and total disomy. A significant inverse association was observed between DMP and total disomy. Findings for total sum of DAP metabolites concealed individual associations as those results differed from the patterns observed for each individual metabolite. Dose-response relationships appeared nonmonotonic, with most of the increase in disomy rates occurring between the second and third exposure quartiles and without additional increases between the third and fourth exposure quartiles.

CONCLUSIONS

This is the first epidemiologic study of this size to examine the relationship between environmental OP exposures and human sperm disomy outcomes. Our findings suggest that increased disomy rates were associated with specific DAP metabolites, suggesting that the impacts of OPs on testis function need further characterization in epidemiologic studies.

Bisphenol-A and Female Infertility: A Possible Role of Gene-Environment Interactions

Background: Bisphenol-A (BPA) is widely used and ubiquitous in the environment. Animal studies indicate that BPA affects reproduction, however, the gene-environment interaction mechanism(s) involved in this association remains unclear. We performed a literature review to summarize the evidence on this topic. Methods: A comprehensive search was conducted in PubMed using as keywords BPA, gene, infertility and female reproduction. Full-text articles in both human and animals published in English prior to December 2014 were selected. Results: Evidence shows that BPA can interfere with endocrine function of hypothalamic-pituitary axis, such as by changing gonadotropin-releasing hormones (GnRH) secretion in hypothalamus and promoting pituitary proliferation. Such actions affect puberty, ovulation and may even result in infertility. Ovary, uterus and other reproductive organs are also targets of BPA. BPA exposure impairs the structure and functions of female reproductive system in different times of life cycle and may contribute to infertility. Both epidemiological and experimental evidences demonstrate that BPA affects reproduction-related gene expression and epigenetic modification that are closely associated with infertility. The detrimental effects on reproduction may be lifelong and transgenerational. Conclusions: Evidence on gene-environment interactions, especially from human studies, is still limited. Further research on this topic is warranted.

Gene-environment interactions in male reproductive health: special reference to the aryl hydrocarbon receptor signaling pathway

Over the last few decades, there have been numerous reports of adverse effects on the reproductive health of wildlife and laboratory animals caused by exposure to endocrine disrupting chemicals (EDCs). The increasing trends in human male reproductive disorders and the mounting evidence for causative environmental factors have therefore sparked growing interest in the health threat posed to humans by EDCs, which are substances in our food, environment and consumer items that interfere with hormone action, biosynthesis or metabolism, resulting in disrupted tissue homeostasis or reproductive function. The mechanisms of EDCs involve a wide array of actions and pathways. Examples include the estrogenic, androgenic, thyroid and retinoid pathways, in which the EDCs may act directly as agonists or antagonists, or indirectly via other nuclear receptors. Dioxins and dioxin-like EDCs exert their biological and toxicological actions through activation of the aryl hydrocarbon-receptor, which besides inducing transcription of detoxifying enzymes also regulates transcriptional activity of other nuclear receptors. There is increasing evidence that genetic predispositions may modify the susceptibility to adverse effects of toxic chemicals. In this review, potential consequences of hereditary predisposition and EDCs are discussed, with a special focus on the currently available publications on interactions between dioxin and androgen signaling.

Association of GSTM1 and GSTT1 genes with the susceptibility to male infertility: result from a meta-analysis

The deletion polymorphisms of the glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) genes were considered as candidates for genetic susceptibility factors of male infertility. Previous studies concerning the relationship between the null genotype of the two genes and male infertility have been reported in recent years. However, the results remain elusive. A meta-analysis was performed to estimate the relationship between the deletion polymorphism of the GSTM1 or GSTT1 gene, and male infertility in this study. Sixteen studies concerning the GSTM1 gene, including 2174 cases and 1861 controls, and 13 case-control studies on the GSTT1 gene with a total number of 1992 cases and 1617 controls were processed. The results showed that the null genotype of the GSTM1 gene was associated with male infertility in the overall populations (P=0.003, OR=1.40, 95%CI=1.12-1.75), especially in Caucasian (P=0.012, OR=1.50, 95%CI=1.09-2.07) as well as Chinese (P=0.001, OR=1.55, 95%CI=1.19-2.03). The null genotype of the GSTT1 gene was strongly related to male infertility only in Chinese (P=0.000, OR=1.70, 95%CI=1.34-2.14). These results indicated that the null genotype of the GSTM1 gene might contribute to the susceptibility of male infertility, whereas the null genotype of the GSTT1 gene may be a genetic susceptibility factor of male infertility for the Chinese.

Null genotype of GSTM1 and GSTT1 may contribute to susceptibility to male infertility with impaired spermatogenesis in Chinese population

Glutathione-S-transferases (GSTs) play a protective role during spermatogenesis and GST genes may be involved in impaired spermatogenesis. A case-control study was performed to explore the association of genes GSTM1 and GSTT1, two members of GST gene family, with spermatogenesis impairment. The deletion polymorphism distribution of genes GSTM1 and GSTT1 was investigated in 353 patients with azoospermia or oligospermia and 201 fertile controls in Chinese population using multiplex PCR. As a result, the frequencies of null genotype of genes GSTM1 (67.4% versus 57.7%, p = 0.022, OR = 1.516, 95% CI = 1.001-2.168) and GSTT1 (61.8% versus 46.8%, p = 0.001, OR = 1.838, 95% CI = 1.295-2.610) in patients were significantly higher than those in controls. After stratifying patients, the frequencies of null genotype of gene GSTM1 in oligospermia (68.3% versus 57.7%, p = 0.027, OR = 1.580, 95% CI = 1.051-2.375) and GSTT1 in azoospermia (66.9% versus 46.8%, p < 0.001, OR = 2.299, 95% CI = 1.484-3.562) as well as oligospermia (57.9% versus 46.8%, p = 0.025, OR = 1.567, 95% CI = 1.057-2.322) were still significantly higher compared with controls. The results suggested that null genotypes of GSTM1 and GSTT1 are associated with spermatogenesis impairment and may contribute to susceptibility to spermatogenesis impairment and male infertility in Chinese population.

Genetic variants in TP53 and MDM2 associated with male infertility in Chinese population

The TP53, a transcriptional regulator and tumor suppressor, is functionally important in spermatogenesis. MDM2 is a key regulator of the p53 pathway and modulates p53 activity. Both proteins have been functionally linked to germ cell apoptosis, which may affect human infertility, but very little is known on how common polymorphisms in these genes may influence germ cell apoptosis and the risk of male infertility. Thus, this study was designed to test whether three previously described polymorphisms 72Arg>Pro (rs1042522) and the Ex2+19C>T (rs2287498) in TP53, and the 5' untranslated region (5' UTR) 309T>G (rs937283) in MDM2, are associated with idiopathic male infertility in a Chinese population. The three polymorphisms were genotyped using OpenArray assay in a hospital-based case-control study, including 580 infertile patients and 580 fertile controls. Our analyses revealed that TP53 Ex2+19C>T and MDM2 309T>G polymorphisms are associated with male infertility. Furthermore, we detected a nearly statistically significant additive interaction between TP53 rs2287498 and MDM2 rs937283 for the development of male infertility (P(interaction)=0.055). In summary, this study found preliminary evidence, demonstrating that genetic variants in genes of the TP53 pathway are risk factors for male infertility.