Comparative single-cell analysis of biopsies clarifies pathogenic mechanisms in Klinefelter syndrome.

Klinefelter syndrome (KS), also known as 47, XXY, is characterized by a distinct set of physiological abnormalities, commonly including infertility. The molecular basis for Klinefelter-related infertility is still unclear, largely because of the cellular complexity of the testis and the intricate endocrine and paracrine signaling that regulates spermatogenesis. Here, we demonstrate an analysis framework for dissecting human testis pathology that uses comparative analysis of single-cell RNA-sequencing data from the biopsies of 12 human donors. By comparing donors from a range of ages and forms of infertility, we generate gene expression signatures that characterize normal testicular function and distinguish clinically distinct forms of male infertility. Unexpectedly, we identified a subpopulation of Sertoli cells within multiple individuals with KS that lack transcription from the XIST locus, and the consequence of this is increased X-linked gene expression compared to all other KS cell populations. By systematic assessment of known cell signaling pathways, we identify 72 pathways potentially active in testis, dozens of which appear upregulated in KS. Altogether our data support a model of pathogenic changes in interstitial cells cascading from loss of X inactivation in pubertal Sertoli cells and nominate dosage-sensitive factors secreted by Sertoli cells that may contribute to the process. Our findings demonstrate the value of comparative patient analysis in mapping genetic mechanisms of disease and identify an epigenetic phenomenon in KS Sertoli cells that may prove important for understanding causes of infertility and sex chromosome evolution.

NRF2 loss recapitulates heritable impacts of paternal cigarette smoke exposure.

Paternal cigarette smoke (CS) exposure is associated with increased risk of behavioral disorders and cancer in offspring, but the mechanism has not been identified. Here we use mouse models to investigate mechanisms and impacts of paternal CS exposure. We demonstrate that CS exposure induces sperm DNAme changes that are partially corrected within 28 days of removal from CS exposure. Additionally, paternal smoking is associated with changes in prefrontal cortex DNAme and gene expression patterns in offspring. Remarkably, the epigenetic and transcriptional effects of CS exposure that we observed in wild type mice are partially recapitulated in Nrf2-/- mice and their offspring, independent of smoking status. Nrf2 is a central regulator of antioxidant gene transcription, and mice lacking Nrf2 consequently display elevated oxidative stress, suggesting that oxidative stress may underlie CS-induced heritable epigenetic changes. Importantly, paternal sperm DNAme changes do not overlap with DNAme changes measured in offspring prefrontal cortex, indicating that the observed DNAme changes in sperm are not directly inherited. Additionally, the changes in sperm DNAme associated with CS exposure were not observed in sperm of unexposed offspring, suggesting the effects are likely not maintained across multiple generations.

Transcription and imprinting dynamics in developing postnatal male germline stem cells.

Postnatal spermatogonial stem cells (SSCs) progress through proliferative and developmental stages to populate the testicular niche prior to productive spermatogenesis. To better understand, we conducted extensive genomic profiling at multiple postnatal stages on subpopulations enriched for particular markers (THY1, KIT, OCT4, ID4, or GFRa1). Overall, our profiles suggest three broad populations of spermatogonia in juveniles: (1) epithelial-like spermatogonia (THY1(+); high OCT4, ID4, and GFRa1), (2) more abundant mesenchymal-like spermatogonia (THY1(+); moderate OCT4 and ID4; high mesenchymal markers), and (3) (in older juveniles) abundant spermatogonia committing to gametogenesis (high KIT(+)). Epithelial-like spermatogonia displayed the expected imprinting patterns, but, surprisingly, mesenchymal-like spermatogonia lacked imprinting specifically at paternally imprinted loci but fully restored imprinting prior to puberty. Furthermore, mesenchymal-like spermatogonia also displayed developmentally linked DNA demethylation at meiotic genes and also at certain monoallelic neural genes (e.g., protocadherins and olfactory receptors). We also reveal novel candidate receptor-ligand networks involving SSCs and the developing niche. Taken together, neonates/juveniles contain heterogeneous epithelial-like or mesenchymal-like spermatogonial populations, with the latter displaying extensive DNA methylation/chromatin dynamics. We speculate that this plasticity helps SSCs proliferate and migrate within the developing seminiferous tubule, with proper niche interaction and membrane attachment reverting mesenchymal-like spermatogonial subtype cells back to an epithelial-like state with normal imprinting profiles.

Standards in semen examination: publishing reproducible and reliable data based on high-quality methodology.

Biomedical science is rapidly developing in terms of more transparency, openness and reproducibility of scientific publications. This is even more important for all studies that are based on results from basic semen examination. Recently two concordant documents have been published: the 6th edition of the WHO Laboratory Manual for the Examination and Processing of Human Semen, and the International Standard ISO 23162:2021. With these tools, we propose that authors should be instructed to follow these laboratory methods in order to publish studies in peer-reviewed journals, preferable by using a checklist as suggested in an Appendix to this article.

Disruption of human meiotic telomere complex genes TERB1, TERB2 and MAJIN in men with non-obstructive azoospermia.

Non-obstructive azoospermia (NOA), the lack of spermatozoa in semen due to impaired spermatogenesis affects nearly 1% of men. In about half of cases, an underlying cause for NOA cannot be identified. This study aimed to identify novel variants associated with idiopathic NOA. We identified a nonconsanguineous family in which multiple sons displayed the NOA phenotype. We performed whole-exome sequencing in three affected brothers with NOA, their two unaffected brothers and their father, and identified compound heterozygous frameshift variants (one novel and one extremely rare) in Telomere Repeat Binding Bouquet Formation Protein 2 (TERB2) that segregated perfectly with NOA. TERB2 interacts with TERB1 and Membrane Anchored Junction Protein (MAJIN) to form the tripartite meiotic telomere complex (MTC), which has been shown in mouse models to be necessary for the completion of meiosis and both male and female fertility. Given our novel findings of TERB2 variants in NOA men, along with the integral role of the three MTC proteins in spermatogenesis, we subsequently explored exome sequence data from 1495 NOA men to investigate the role of MTC gene variants in spermatogenic impairment. Remarkably, we identified two NOA patients with likely damaging rare homozygous stop and missense variants in TERB1 and one NOA patient with a rare homozygous missense variant in MAJIN. Available testis histology data from three of the NOA patients indicate germ cell maturation arrest, consistent with mouse phenotypes. These findings suggest that variants in MTC genes may be an important cause of NOA in both consanguineous and outbred populations.

Differential impacts of particulate air pollution exposure on early and late stages of spermatogenesis.

BACKGROUND: Despite increasing evidence that particulate air pollution has adverse effects on human semen quality, few studies examine the impact of air pollution on clinically relevant thresholds used to diagnose male fertility problems. Furthermore, exposure is often assessed using average air pollution levels in a geographic area rather than individualized estimates. Finally, physiologically-informed exposure windows are inconsistent. OBJECTIVES: We sought to test the hypothesis that airborne particulate exposures during early-phase spermatogenesis will have a differential impact on spermatogenic formation compared to late-phase exposures, using an individualized model of exposure to particulate matter ≤ 2.5 µm and ≤ 10 µm (PM2.5 and PM10, respectively). METHODS: From an original cohort of 183 couples, we conducted a retrospective analysis of 130 healthy males seeking to become parents, using spermatogenesis-relevant exposure windows of 77-34 days and 37-0 days prior to semen collection to encompass sperm development stages of mitosis/meiosis and spermiogenesis, respectively. Individualized residential exposure to PM2.5 and PM10 was estimated by selecting multiple air pollution sensors within the same geographic air basin as participants and employing inverse distance weighting to calculate mean daily exposure levels. We used multiple logistic regression to assess the association between pollution, temperature, and dichotomized World Health Organization semen parameters. RESULTS: During the early phase of spermatogenesis, air pollution exposure is associated with 1.52 (95% CI: 1.04-2.32) times greater odds of < 30% normal heads per 1-unit increase in IQR for PM2.5. In the late phase of spermatogenesis, air pollution exposure is associated with 0.35 (95% CI: 0.10-0.74) times greater odds of semen concentration < 15 million/mL per 1-unit increase in IQR for PM2.5, and 0.28 (95% CI: 0.07-0.72) for PM10. CONCLUSION: Particulate exposure has a differential and more deleterious impact on sperm during early-phase spermatogenesis than late-phase.

A Randomized Trial to Evaluate the Effects of Folic Acid and Zinc Supplementation on Male Fertility and Livebirth: Design and Baseline Characteristics.

The Folic Acid and Zinc Supplementation Trial (FAZST) was a multicenter, double-blind, block-randomized, placebo-controlled trial to determine whether folic acid and zinc supplementation in men improves semen quality and increases livebirth rate among couples seeking infertility treatment (2013-2017). Eligible men were aged 18 years or older with female partners aged 18-45 years, seeking infertility treatment. Men were randomized (1:1) to 5 mg folic acid and 30 mg elemental zinc daily or matching placebo for 6 months. Randomization was stratified by site and intended infertility treatment (in vitro fertilization (IVF), non-IVF/study site, and non-IVF/outside clinic). Follow-up of men continued for 6 months, and female partners were passively followed for a minimum of 9 months. Women who conceived were followed throughout pregnancy. Overall, 2,370 men were randomized during 2013-2017 (1,185 folic acid and zinc, 1,185 placebo); they had a mean age of 33 years and body mass index (weight (kg)/height (m)2) of 29.8. Most participants were white (82%), well educated (83% with some college), and employed (72%). Participant characteristics were balanced across intervention arms. Study visits were completed by 89%, 77%, and 75% of men at months 2, 4, and 6, respectively. Here we describe the study design, recruitment, data collection, lessons learned, and baseline participant characteristics.

Genetic dissection of spermatogenic arrest through exome analysis: clinical implications for the management of azoospermic men.

PURPOSE: Azoospermia affects 1% of men and it can be the consequence of spermatogenic maturation arrest (MA). Although the etiology of MA is likely to be of genetic origin, only 13 genes have been reported as recurrent potential causes of MA. METHODS: Exome sequencing in 147 selected MA patients (discovery cohort and two validation cohorts). RESULTS: We found strong evidence for five novel genes likely responsible for MA (ADAD2, TERB1, SHOC1, MSH4, and RAD21L1), for which mouse knockout (KO) models are concordant with the human phenotype. Four of them were validated in the two independent MA cohorts. In addition, nine patients carried pathogenic variants in seven previously reported genes-TEX14, DMRT1, TEX11, SYCE1, MEIOB, MEI1, and STAG3-allowing to upgrade the clinical significance of these genes for diagnostic purposes. Our meiotic studies provide novel insight into the functional consequences of the variants, supporting their pathogenic role. CONCLUSION: Our findings contribute substantially to the development of a pre-testicular sperm extraction (TESE) prognostic gene panel. If properly validated, the genetic diagnosis of complete MA prior to surgical interventions is clinically relevant. Wider implications include the understanding of potential genetic links between nonobstructive azoospermia (NOA) and cancer predisposition, and between NOA and premature ovarian failure.

Effect of Folic Acid and Zinc Supplementation in Men on Semen Quality and Live Birth Among Couples Undergoing Infertility Treatment: A Randomized Clinical Trial.

Importance: Dietary supplements marketed for male fertility commonly contain folic acid and zinc based on limited prior evidence for improving semen quality. However, no large-scale trial has examined the efficacy of this therapy for improving semen quality or live birth. Objective: To determine the effect of daily folic acid and zinc supplementation on semen quality and live birth. Design, Setting, and Participants: The Folic Acid and Zinc Supplementation Trial was a multicenter randomized clinical trial. Couples (n = 2370; men aged ≥18 years and women aged 18-45 years) planning infertility treatment were enrolled at 4 US reproductive endocrinology and infertility care study centers between June 2013 and December 2017. The last 6-month study visit for semen collection occurred during August 2018, with chart abstraction of live birth and pregnancy information completed during April 2019. Interventions: Men were block randomized by study center and planned infertility treatment (in vitro fertilization, other treatment at a study site, and other treatment at an outside clinic) to receive either 5 mg of folic acid and 30 mg of elemental zinc (n = 1185) or placebo (n = 1185) daily for 6 months. Main Outcomes and Measures: The co-primary outcomes were live birth (resulting from pregnancies occurring within 9 months of randomization) and semen quality parameters (sperm concentration, motility, morphology, volume, DNA fragmentation, and total motile sperm count) at 6 months after randomization. Results: Among 2370 men who were randomized (mean age, 33 years), 1773 (75%) attended the final 6-month study visit. Live birth outcomes were available for all couples, and 1629 men (69%) had semen available for analysis at 6 months after randomization. Live birth was not significantly different between treatment groups (404 [34%] in the folic acid and zinc group and 416 [35%] in the placebo group; risk difference, -0.9% [95% CI, -4.7% to 2.8%]). Most of the semen quality parameters (sperm concentration, motility, morphology, volume, and total motile sperm count) were not significantly different between treatment groups at 6 months after randomization. A statistically significant increase in DNA fragmentation was observed with folic acid and zinc supplementation (mean of 29.7% for percentage of DNA fragmentation in the folic acid and zinc group and 27.2% in the placebo group; mean difference, 2.4% [95% CI, 0.5% to 4.4%]). Gastrointestinal symptoms were more common with folic acid and zinc supplementation compared with placebo (abdominal discomfort or pain: 66 [6%] vs 40 [3%], respectively; nausea: 50 [4%] vs 24 [2%]; and vomiting: 32 [3%] vs 17 [1%]). Conclusions and Relevance: Among a general population of couples seeking infertility treatment, the use of folic acid and zinc supplementation by male partners, compared with placebo, did not significantly improve semen quality or couples' live birth rates. These findings do not support the use of folic acid and zinc supplementation by male partners in the treatment of infertility. Trial Registration: ClinicalTrials.gov Identifier: NCT01857310.

The Role of the Epididymis and the Contribution of Epididymosomes to Mammalian Reproduction.

It is well-established that testicular spermatozoa are immature and acquire motility and fertilization capabilities during transit throughout the epididymis. The epididymis is a duct-like organ that connects the testis to the vas deferens and is comprised of four anatomical regions: the initial segment, caput, corpus, and cauda. Sperm maturation occurs during epididymal transit by the interaction of sperm cells with the unique luminal environment of each epididymal region. In this review we discuss the epididymis as an essential reproductive organ responsible for sperm concentration, maturation (including sperm motility acquisition and fertilizing ability), protection and storage. Importantly, we also discuss specific characteristics and roles of epididymal-derived exosomes (epididymosomes) in establishing sperm competency within the intricate process of reproduction. This review suggests that an increasing body of evidence is working to develop a complete picture of the role of the epididymis in male reproduction, offspring health, and disease susceptibility.

The Sperm Epigenome: Implications for Assisted Reproductive Technologies.

Compared to other cells, sperm undergo dramatic remodeling of their chromatin during late spermiogenesis in which approximately 95% of histones are removed and replaced with protamines. Despite this large-scale remodeling, key developmental genes, some miRNA genes, and imprinted genes retain their association with histone. The developmental genes have a unique epigenetic signature, termed bivalency, that poises the genes for embryonic activation. Anomalies in that epigenetic poising signature, either in the form of DNA methylation aberrations, improper protamination, or altered histone modifications, are associated with infertility and reduced embryogenesis capability. Additionally, some small noncoding RNAs are retained, while others are actively added to the sperm and appear to affect embryogenesis. Therefore, initial studies have begun to formulate pathways by which the sperm epigenome can be used as a diagnostic tool in the clinic. While in their infancy, these assays likely portend improved diagnostics and added information for patients and clinicians. Recent studies also highlight the possibility that the sperm epigenome can be used to evaluate lifestyle and environmental risks to the patient and potentially to the offspring.

Sperm DNA Fragmentation: Consequences for Reproduction.

DNA fragmentation, or the accumulation of single- and double-strand DNA breaks, is a common property of sperm, and an increase in the level of sperm DNA fragmentation is known to influence natural reproduction. The effect of sperm DNA fragmentation on male infertility and assisted reproductive treatment (ART) outcomes remains controversial and is one of the most frequently debated topics of reproductive medicine. For the past 30 years, a number of assays have been developed to quantify the level of sperm DNA fragmentation. In this chapter, we review the causes of sperm DNA fragmentation, describe the commonly used tests to evaluate these abnormalities, and perform a systematic review of existing studies to determine the impact of sperm DNA fragmentation on male fertility and ART outcomes.

Paternal germ line aging: DNA methylation age prediction from human sperm.

BACKGROUND: The relationship between aging and epigenetic profiles has been highlighted in many recent studies. Models using somatic cell methylomes to predict age have been successfully constructed. However, gamete aging is quite distinct and as such age prediction using sperm methylomes is ineffective with current techniques. RESULTS: We have produced a model that utilizes human sperm DNA methylation signatures to predict chronological age by utilizing methylation array data from a total of 329 samples. The dataset used for model construction includes infertile patients, sperm donors, and individuals from the general population. Our model is capable predicting age with an R2 of 0.89, a mean absolute error (MAE) of 2.04 years, and a mean absolute percent error (MAPE) of 6.28% in our data set. We additionally investigated the reproducibility of prediction with our model in an independent cohort where 6 technical replicates of 10 individual samples were tested on different arrays. We found very similar age prediction accuracy (MAE = 2.37 years; MAPE = 7.05%) with a high degree of precision between replicates (standard deviation of only 0.877 years). Additionally, we found that smokers trended toward increased age profiles when compared to 'never smokers' though this pattern was only striking in a portion of the samples screened. CONCLUSIONS: The predictive model described herein was built to offer researchers the ability to assess "germ line age" by accessing sperm DNA methylation signatures at genomic regions affected by age. Our data suggest that this model can predict an individual's chronological age with a high degree of accuracy regardless of fertility status and with a high degree of repeatability. Additionally, our data suggest that the aging process in sperm may be impacted by environmental factors, though this effect appears to be quite subtle and future work is needed to establish this relationship.

The impact of ejaculatory abstinence on semen analysis parameters: a systematic review.

OBJECTIVE: The aim of this study was to evaluate recent publications and determine the impact of ejaculatory abstinence on semen analysis parameters as well as fertility outcomes. METHODS: This was a systematic review of 28 recent publications. The focus of this study was the impact of abstinence on semen parameters and fertility outcomes in papers published since the year 2000. The specific parameters evaluated were volume, sperm count, motility, morphology, pH, DNA fragmentation rate, viability, and pregnancy or fertilization rates following assisted reproduction. RESULTS: Twenty-eight recent publications met inclusion criteria. Analysis of publications showed that longer abstinence is associated with increases in semen volume and sperm count. Studies evaluating the effect of abstinence on motility, morphology, and DNA fragmentation rates are contradictory and inconclusive, although a trend appears to exist toward improvements in semen parameters with shorter abstinence. Semen pH was unaffected by abstinence. The majority of publications found no difference in rates of viability with varying abstinence times, although total number of viable sperm increases with increasing abstinence. Some studies evaluating the impact of ejaculatory abstinence on intrauterine insemination (IUI), intracytoplasmic sperm injection (ICSI), and in vitro fertilization (IVF) demonstrated an association between short abstinence and improved outcomes. CONCLUSIONS: The impact of abstinence on sperm quality is complex. While certain semen parameters improve with longer abstinence, others appear to improve with shorter abstinence. No clear recommendations can be made regarding ideal abstinence due to the conflicting nature of current evidence. Going forward, more research is needed to evaluate the impact of abstinence on pregnancy and fertilization rates.

Do paternal semen parameters influence the birth weight or BMI of the offspring? A study from the Utah Population Database.

PURPOSE: To study the role of individual semen parameters on the offspring birth weight and body mass index (BMI) from a population of men evaluated in an assisted reproduction technology (ART) clinic compared to fertile controls. METHODS: We performed a retrospective study using a cohort with fertile, age-matched controls of men evaluated with semen analysis at the University of Utah Andrology Clinic from 1996 to 2011 and Intermountain Healthcare from 2002 to 2011. We use the offspring from both our sub-fertile cohort and controls using the Utah Population Database. The two main outcomes of interest were offspring birth weight and adolescent BMI. RESULTS: The offspring of men with impaired sperm parameters had significantly lower birth weight compared to fertile control offspring. Low-concentration offspring weighed 158 g less (95% CI - 278~- 38; p = 0.01), low total count weighed 172 g less (95% CI - 294~- 51; p = 0.005), and low total motility weighed 155 g less (95% CI - 241~- 69; p < 0.001) compared to those of the controls. When we controlled for the use of ART within the sub-fertile group, we found that there was a significant trend of increasing birth weight across levels of total motile count and total sperm count compared to the azoospermic group. We did not find any consistent significant differences between the subject and control adolescence BMI based on semen parameters. CONCLUSIONS: Despite limitations within our population-based dataset, we found that poor quality semen analysis parameters pointed towards an association with low birth weight in the offspring of sub-fertile men compared to the offspring of normal fertile controls. However, in contrast to studies of ART effects on offspring, we did not find evidence of long-term associations between semen quality and offspring BMI.

Childhood Cancer Risk in the Siblings and Cousins of Men with Poor Semen Quality.

PURPOSE: Poor semen quality is associated with reduced somatic health and increased cancer risk. Infertility and cancer are increasingly being linked by epidemiologists and basic scientists. We sought to identify semen parameters associated with an increased childhood cancer risk in the family members of subfertile men. MATERIALS AND METHODS: We performed a retrospective cohort study in men from the SHARE (Subfertility Heath and Assisted Reproduction) study who underwent semen analysis between 1994 and 2011. We used fertile population controls from the Utah Population Data Base. Our primary outcome was the risk of any childhood (18 years or younger) cancer in the siblings and cousins of men who underwent semen analysis compared to fertile, age matched controls. Cox proportional hazard regression models were used to test the association between semen quality and childhood cancer incidence. RESULTS: We selected 10,511 men with complete semen analysis and an equal number of fertile controls. These men had a total of 63,891 siblings and 327,753 cousins. A total of 170 and 958 childhood cancers were identified in siblings and cousins, respectively. The 3 most common cancers diagnosed in siblings were acute lymphoblastic leukemia in 37, brain cancer in 35 and Hodgkin lymphoma in 15. Oligozoospermia was associated with a twofold increased risk of any childhood cancer and a threefold increased risk of acute lymphoblastic leukemia in the siblings of subfertile men compared to fertile controls (HR 2.09, 95% CI 1.18-3.69 vs HR 3.07, 95% CI 1.11-8.46). CONCLUSIONS: Siblings of men with oligozoospermia are at increased risk for any-site cancer and acute lymphoblastic leukemia. This suggests a shared genetic/epigenetic insult or an environmental exposure that merits further investigation.

Risk of childhood mortality in family members of men with poor semen quality.

STUDY QUESTION: What is the familial childhood mortality in first-degree (FDR) and second-degree relatives (SDR) of patients undergoing semen analysis (SA)? SUMMARY ANSWER: The relationship between infertility and congenital malformations (CM) in offspring is complex, with an increased risk of death due to CM in FDR, but not SDR, of men with lower semen parameters. WHAT IS KNOWN ALREADY: Semen quality is an established predictor of men's somatic health. We can gain a better understanding of possible genetic or environmental determinants of the infertility phenotype by exploring familial aggregation of childhood mortality in relatives of men with poor semen quality. STUDY DESIGN, SIZE, DURATION: Retrospective cohort study from the Subfertility, Health and Assisted Reproduction study (cohort compiled 1996-2011) linked with patient/familial information from the Utah Population Database (UPDB). Index cases included a clinic-referred sample of 12 889 men who underwent SA and had adequate familial and follow-up data in the UPDB. Parameters of semen quality included: semen concentration, sperm count, motility, total motile count, sperm head morphology, sperm tail morphology and vitality. PARTICIPANTS/MATERIALS, SETTING, METHODS: SA data were collected from two tertiary medical center andrology laboratories that have captured ~90% of all SA performed in Utah since 2004. Age- and sex-matched fertile controls were selected to create the comparison group for determining risk of childhood death (to age 20 years) in family members. A total of 79 750 siblings and 160 016 aunts/uncles were used to investigate the familial aggregation of childhood mortality. The main outcome was childhood mortality in FDR and SDR of men with SA and their matched controls. All-cause and cause-specific Cox proportional hazard models were used to test the association between semen quality and childhood mortality in family members. Cause-specific models were considered for cancer and CM. MAIN RESULTS AND THE ROLE OF CHANCE: In the cohort of men with SA, there were 406 (1.0%) deaths in FDR and 772 (1.1%) deaths in SDR due to any cause. There was no significant difference in the risk of all-cause childhood mortality between the relatives of men with SA and the fertile control group [hazard ratio (HR)Female = 1.08, 95% CI = 0.88, 1.32; HRMale = 0.88, 95% CI = 0.75, 1.04]. We found no association between semen quality and risk for childhood cancer mortality in FDR or SDR (HRFDR = 0.98, 95% CI = 0.62, 1.54; HRSDR = 1.12, 95% CI = 0.83, 1.50). The FDR of men with SA and fertile controls were followed on average for 19.71 and 19.73 years, respectively. During this period of follow-up, FDR of men with SA had an unadjusted 40% relative risk of increased CM-related death. After stratifying by semen parameters and adjusting for birth year, we found FDR of men with worse semen quality, and notably azoospermic men (HR = 2.69, 95% CI = 1.24,5.84), were at higher risk of CM-related death. LIMITATIONS REASONS FOR CAUTION: A large proportion of men with SA in the study had normal semen parameters. It is important to note that these men themselves may not be subfertile, but they were subfertile at the couple level (i.e. the female partner may be infertile). In addition, care is needed when interpreting our results, as we do not have semen measures on our sample of fertile men. Second, we were unable to include potential confounders such as medical comorbidities, smoking status, or environmental exposures. Third, men with SA were seen at the University of Utah or Intermountain Health Care clinics for a fertility evaluation thereby suggesting a more select population. Fourth, we chose to categorize morphology into equally distributed quartiles as a response to the fact that the World Health Organization threshold for normal motility changed multiple times during our study period. Lastly, we do not know the proportion of female partners with diagnosed infertility. We chose not to subcategorize each infertile male by infertile diagnosis because our goal was to understand how semen parameters influenced familial childhood mortality. WIDER IMPLICATIONS OF THE FINDINGS: We are not the first study to show a relationship between fertility and CMs. Children conceived through ART may be at higher risk of birth defects, however it is not known if the relationship is causal or if there is some underlying factor linking infertility and birth outcomes. This study provides further evidence that the increased risk of congenital birth defects may not be due to the ART, but rather genetic or environmental factors that link the two outcomes. We encourage further research in order to confirm a relationship between semen quality and increased risk for CM. STUDY FUNDING/COMPETING INTERESTS: This work was supported by the National Institutes of Health - National Institute of Aging [Grant numbers 1R21AG036938-01, 2R01 AG022095 and 1K12HD085852-01]. Authors have no competing interests to disclose. TRIAL REGISTRATION NUMBER: Not applicable.

Age-associated sperm DNA methylation alterations: possible implications in offspring disease susceptibility.

Recent evidence demonstrates a role for paternal aging on offspring disease susceptibility. It is well established that various neuropsychiatric disorders (schizophrenia, autism, etc.), trinucleotide expansion associated diseases (myotonic dystrophy, Huntington's, etc.) and even some forms of cancer have increased incidence in the offspring of older fathers. Despite strong epidemiological evidence that these alterations are more common in offspring sired by older fathers, in most cases the mechanisms that drive these processes are unclear. However, it is commonly believed that epigenetics, and specifically DNA methylation alterations, likely play a role. In this study we have investigated the impact of aging on DNA methylation in mature human sperm. Using a methylation array approach we evaluated changes to sperm DNA methylation patterns in 17 fertile donors by comparing the sperm methylome of 2 samples collected from each individual 9-19 years apart. With this design we have identified 139 regions that are significantly and consistently hypomethylated with age and 8 regions that are significantly hypermethylated with age. A representative subset of these alterations have been confirmed in an independent cohort. A total of 117 genes are associated with these regions of methylation alterations (promoter or gene body). Intriguingly, a portion of the age-related changes in sperm DNA methylation are located at genes previously associated with schizophrenia and bipolar disorder. While our data does not establish a causative relationship, it does raise the possibility that the age-associated methylation of the candidate genes that we observe in sperm might contribute to the increased incidence of neuropsychiatric and other disorders in the offspring of older males. However, further study is required to determine whether, and to what extent, a causative relationship exists.

Human spermatogenic failure purges deleterious mutation load from the autosomes and both sex chromosomes, including the gene DMRT1.

Gonadal failure, along with early pregnancy loss and perinatal death, may be an important filter that limits the propagation of harmful mutations in the human population. We hypothesized that men with spermatogenic impairment, a disease with unknown genetic architecture and a common cause of male infertility, are enriched for rare deleterious mutations compared to men with normal spermatogenesis. After assaying genomewide SNPs and CNVs in 323 Caucasian men with idiopathic spermatogenic impairment and more than 1,100 controls, we estimate that each rare autosomal deletion detected in our study multiplicatively changes a man's risk of disease by 10% (OR 1.10 [1.04-1.16], p<2 × 10(-3)), rare X-linked CNVs by 29%, (OR 1.29 [1.11-1.50], p<1 × 10(-3)), and rare Y-linked duplications by 88% (OR 1.88 [1.13-3.13], p<0.03). By contrasting the properties of our case-specific CNVs with those of CNV callsets from cases of autism, schizophrenia, bipolar disorder, and intellectual disability, we propose that the CNV burden in spermatogenic impairment is distinct from the burden of large, dominant mutations described for neurodevelopmental disorders. We identified two patients with deletions of DMRT1, a gene on chromosome 9p24.3 orthologous to the putative sex determination locus of the avian ZW chromosome system. In an independent sample of Han Chinese men, we identified 3 more DMRT1 deletions in 979 cases of idiopathic azoospermia and none in 1,734 controls, and found none in an additional 4,519 controls from public databases. The combined results indicate that DMRT1 loss-of-function mutations are a risk factor and potential genetic cause of human spermatogenic failure (frequency of 0.38% in 1306 cases and 0% in 7,754 controls, p = 6.2 × 10(-5)). Our study identifies other recurrent CNVs as potential causes of idiopathic azoospermia and generates hypotheses for directing future studies on the genetic basis of male infertility and IVF outcomes.