Epigenetic dynamics and interplay during spermatogenesis and embryogenesis: implications for male fertility and offspring health

SETD1B-mediated broad H3K4me3 controls proper temporal patterns of gene expression critical for spermatid development

Epigenetic programming governs cell fate determination during development through intricately controlling sequential gene activation and repression. Although H3K4me3 is widely recognized as a hallmark of gene activation, its role in modulating transcription output and timing within a continuously developing system remains poorly understood. In this study, we provide a detailed characterization of the epigenomic landscapes in developing male germ cells. We identified thousands of spermatid-specific broad H3K4me3 domains regulated by the SETD1B-RFX2 axis, representing a previously underappreciated form of H3K4me3. These domains, overlapping with H3K27ac-marked enhancers and promoters, play critical roles in orchestrating robust transcription and accurate temporal control of gene expression. Mechanistically, these broad H3K4me3 compete effectively with regular H3K4me3 for transcriptional machinery, thereby ensuring robust levels and precise timing of master gene expression in mouse spermiogenesis. Disruption of this mechanism compromises the accuracy of transcription dosage and timing, ultimately impairing spermiogenesis. Additionally, we unveil remarkable changes in the distribution of heterochromatin marks, including H3K27me3 and H3K9me2, during the mitosis-to-meiosis transition and completion of meiotic recombination, which closely correlates with gene silencing. This work underscores the highly orchestrated epigenetic regulation in spermatogenesis, highlighting the previously unrecognized role of Setd1b in the formation of broad H3K4me3 domains and transcriptional control, and provides an invaluable resource for future studies toward the elucidation of spermatogenesis.

Histone lysine methyltransferases and their specific methylation marks show significant changes in mouse testes from young to older ages

Spermatogenesis is finely regulated by histone methylation, which is crucial for regulating gene expression and chromatin remodeling. Functional studies have demonstrated that the histone lysine methyltransferases (KMTs) SETD1B, CFP1, SETDB1, G9A, and SETD2 play pivotal roles in spermatogenesis through establishing the key histone methylation marks, H3K4me3, H3K9me2, H3K9me3, and H3K36me3, respectively. This study aimed to evaluate the spatiotemporal expression of these KMTs and methylation marks as well as senescence-associated β-galactosidase (β-GAL), transcriptional activity, and apoptosis rates in mouse testes during biological aging. In accordance with these purposes, the following groups of Balb/C mice were created: young (1- and 2-week-old), prepubertal (3- and 4-week-old), pubertal (5- and 6-week-old), postpubertal (16-, 18-, and 20-week-old), and aged (48-, 50-, and 52-week-old). The β-GAL staining gradually increased from the young to the aged groups (P < 0.01). The SETD1B, G9A, SETDB1, and SETD2 protein levels increased in spermatogonia, early and pachytene spermatocytes, and Sertoli cells of the aged group (P < 0.05). In contrast, CFP1 protein level decreased in spermatogonia, pachytene spermatocytes, round spermatids, and Sertoli cells towards the older ages (P < 0.05). Moreover, H3K4me3, H3K9me2, H3K9me3, and H3K36me3 levels increased in the aged group (P < 0.05). There was also a significant reduction in apoptosis rates in seminiferous tubules of the pubertal, postpubertal, and aged groups (P < 0.01). Consequently, accumulation of histone methylation marks due to increased expression of KMTs in spermatogenic and Sertoli cells during testicular aging may alter chromatin reprogramming and gene expression, contributing to age-related fertility loss.

Oxidative-Stress-Mediated Epigenetic Dysregulation in Spermatogenesis: Implications for Male Infertility and Offspring Health

Male reproductive health is governed by an intricate interplay of genetic, epigenetic, and environmental factors. Epigenetic mechanisms-encompassing DNA methylation, histone modifications, and non-coding RNA activity-are crucial both for spermatogenesis and sperm maturation. However, oxidative stress, driven by excessive reactive oxygen species, disrupts these processes, leading to impaired sperm function and male infertility. This disruption extends to epigenetic modifications, resulting in abnormal gene expression and chromatin remodeling that compromise genomic integrity and fertilization potential. Importantly, oxidative-stress-induced epigenetic alterations can be inherited, affecting the health and fertility of offspring and future generations. This review investigates how oxidative stress influences epigenetic regulation in male reproduction by modifying DNA methylation, histone modifications, and non-coding RNAs, ultimately compromising spermatogenesis. Additionally, it discusses the transgenerational implications of these epigenetic disruptions and their potential role in hereditary infertility and disease predisposition. Understanding these mechanisms is vital for developing therapeutic strategies that mitigate oxidative damage and restore epigenetic homeostasis in the male germline. By integrating insights from molecular, clinical, and transgenerational research, this work emphasizes the need for targeted interventions to enhance male reproductive health and prevent adverse outcomes in progeny. Furthermore, elucidating the dose-response relationships between oxidative stress and epigenetic changes remains a critical research priority, informing personalized diagnostics and therapeutic interventions. In this context, future studies should adopt standardized markers of oxidative damage, robust clinical trials, and multi-omic approaches to capture the complexity of epigenetic regulation in spermatogenesis. Such rigorous investigations will ultimately reduce the risk of transgenerational disorders and optimize reproductive health outcomes.

International Symposium on Ruminant Physiology: Paternal Nutrient Supply: Impacts on Physiological and Whole Animal Outcomes in Offspring

Recent evidence suggests that environmental factors experienced by sires can be transmitted through the ejaculate (seminal plasma + sperm) into the female reproductive tract, influencing fertilization, embryo development, and postnatal offspring outcomes. This concept is termed paternal programming. In rodents, sire nutrition was shown to directly alter offspring outcomes through sperm epigenetic signatures, DNA damage/oxidative stress, cytokine profiles, and/or the seminal microbiome. Response variables impacted in rodent models, including adiposity, muscle mass, metabolic responses, and reproductive performance, could have major productivity and financial implications for producers if these paternal programming responses are also present in ruminant species. However, a paucity of data exist regarding paternal programming in ruminants. The limited data in the literature mainly point to alterations in sperm epigenome as a result of sire diet or environment. Global nutrition has been implicated in ruminant models to alter seminal cytokine profiles, which could subsequently alter the uterine environment and immune response to mating. Several reports indicate that embryo development and epigenetic signatures can be impacted by sire plane of nutrition and inclusion of specific feed ingredients into diets (polyunsaturated fatty acids, folic acid, and rumen protected methionine). Models of sheep nutrition indicate that addition of rumen protected methionine can impact DNA methylation and offspring performance characteristics extending to the F3 generation, and that divergent planes of sire nutrition can cause altered hormone profiles and insulin/glucose metabolism in offspring. There are almost unlimited opportunities for discovery in this area, but researchers are encouraged to target critical questions such as whether and the extent to which paternal programming effects are present in common management scenarios, the mechanisms by which paternal programming is inherited in ruminants, and whether the effects of paternal nutrition interact with those of maternal nutrition to influence offspring physiology, whole animal outcomes, and herd or flock productivity.

Sperm epigenetics and male infertility: unraveling the molecular puzzle

BACKGROUND

The prevalence of infertility among couples is estimated to range from 8 to 12%. A paradigm shift has occurred in understanding of infertility, challenging the notion that it predominantly affects women. It is now acknowledged that a significant proportion, if not the majority, of infertility cases can be attributed to male-related factors. Various elements contribute to male reproductive impairments, including aberrant sperm production caused by pituitary malfunction, testicular malignancies, aplastic germ cells, varicocele, and environmental factors.

MAIN BODY

The epigenetic profile of mammalian sperm is distinctive and specialized. Various epigenetic factors regulate genes across different levels in sperm, thereby affecting its function. Changes in sperm epigenetics, potentially influenced by factors such as environmental exposures, could contribute to the development of male infertility.

CONCLUSION

In conclusion, this review investigates the latest studies pertaining to the mechanisms of epigenetic changes that occur in sperm cells and their association with male reproductive issues.

Cancer risk and male Infertility: Unravelling predictive biomarkers and prognostic indicators

In recent years, there has been a global increase in cases of male infertility. There are about 30 million cases of male infertility worldwide and male reproductive health is showing rapid decline in last few decades. It is now recognized as a potential risk factor for developing certain types of cancer, particularly genitourinary malignancies like testicular and prostate cancer. Male infertility is considered a potential indicator of overall health and an early biomarker for cancer. Cases of unexplained male factor infertility have high levels of oxidative stress and oxidative DNA damage and this induces both denovo germ line mutations and epimutations due to build up of 8-hydroxy 2 deoxygunaosine abase which is highly mutagenic and also induces hypomethylation and genomic instability. Consequently, there is growing evidence to explore the various factors contributing to an increased cancer risk. Currently, the available prognostic and predictive biomarkers associated with semen characteristics and cancer risk are limited but gaining significant attention in clinical research for the diagnosis and treatment of elevated cancer risk in the individual and in offspring. The male germ cell being transcriptionally and translationally inert has a highly truncated repair mechanism and has minimal antioxidants and thus most vulnerable to oxidative injury due to environmental factors and unhealthy lifestyle and social habits. Therefore, advancing our understanding requires a thorough evaluation of the pathophysiologic mechanisms at the DNA, RNA, protein, and metabolite levels to identify key biomarkers that may underlie the pathogenesis of male infertility and associated cancer. Advanced methodologies such as genomics, epigenetics, proteomics, transcriptomics, and metabolomics stand at the forefront of cutting-edge approaches for discovering novel biomarkers, spanning from infertility to associated cancer types. Henceforth, in this review, we aim to assess the role and potential of recently identified predictive and prognostic biomarkers, offering insights into the success of assisted reproductive technologies, causes of azoospermia and idiopathic infertility, the impact of integrated holistic approach and lifestyle modifications, and the monitoring of cancer susceptibility, initiation and progression. Comprehending these biomarkers is crucial for providing comprehensive counselling to infertile men and cancer patients, along with their families.

Recent Advancements in Research on DNA Methylation and Testicular Germ Cell Tumors: Unveiling the Intricate Relationship

Testicular germ cell tumors (TGCTs) are the most common type of testicular cancer, with a particularly high incidence in the 15-45-year age category. Although highly treatable, resistance to therapy sometimes occurs, with devastating consequences for the patients. Additionally, the young age at diagnosis and the treatment itself pose a great threat to patients' fertility. Despite extensive research concerning genetic and environmental risk factors, little is known about TGCT etiology. However, epigenetics has recently come into the spotlight as a major factor in TGCT initiation, progression, and even resistance to treatment. As such, recent studies have been focusing on epigenetic mechanisms, which have revealed their potential in the development of novel, non-invasive biomarkers. As the most studied epigenetic mechanism, DNA methylation was the first revelation in this particular field, and it continues to be a main target of investigations as research into its association with TGCT has contributed to a better understanding of this type of cancer and constantly reveals novel aspects that can be exploited through clinical applications. In addition to biomarker development, DNA methylation holds potential for developing novel treatments based on DNA methyltransferase inhibitors (DNMTis) and may even be of interest for fertility management in cancer survivors. This manuscript is structured as a literature review, which comprehensively explores the pivotal role of DNA methylation in the pathogenesis, progression, and treatment resistance of TGCTs.

Unravelling the epigenetic impact: Oxidative stress and its role in male infertility-associated sperm dysfunction

Male infertility is a multifactorial condition influenced by epigenetic regulation, oxidative stress, and mitochondrial dysfunction. Oxidative stress-induced damage leads to epigenetic modifications, disrupting gene expression crucial for spermatogenesis and fertilization. Paternal exposure to oxidative stress induces transgenerational epigenetic alterations, potentially impacting male fertility in offspring. Mitochondrial dysfunction impairs sperm function, while leukocytospermia exacerbates oxidative stress-related sperm dysfunction. Therefore, this review focuses on understanding these mechanisms as vital for developing preventive strategies, including targeting oxidative stress-induced epigenetic changes and implementing lifestyle modifications to prevent male infertility. This study investigates how oxidative stress affects the epigenome and sperm production, function, and fertilization. Unravelling the molecular pathways provides valuable insights that can advance our scientific understanding. Additionally, these findings have clinical implications and can help to address the significant global health issue of male infertility.

Sperm deoxyribonucleic acid fragmentation index at the time of intracytoplasmic sperm injection and standard in vitro fertilization is correlated with lower fertilization but not with blastocyst genetic diagnosis

Objective

To determine the effects of sperm deoxyribonucleic acid (DNA) fragmentation at the time of fertilization on in vitro fertilization (IVF) outcomes and genetic diagnosis using next generation sequencing.

Design

Prospective double-blinded study.

Setting

Private Clinic.

Patients

Couples (n = 150).

Intervention

In vitro fertilization with preimplantation genetic testing for aneuploidy and sperm DNA fragmentation assay, as in sperm chromatin structure assay the day of retrieval.

Main Outcome Measures

Laboratory outcomes are listed in the results section. Statistical analysis was performed using JMP, XYLSTAT, and STATA version 15.

Results

The sperm DNA fragmentation index (DFI) in the neat ejaculate did not predict fertilization rate, quality, blastulation, or genetic diagnosis. No statistically significant results were obtained comparing <15% with >15%, <20% with >20%, <30% with >30% except for DFI. No statistically significant differences in oocyte source age or male age were observed. No statistically significant differences comparing <15% with >15%, <20% with >20%, <30% with >30% DFI at the time of standard IVF or intracytoplasmic sperm injection (ICSI) were observed for % euploid, aneuploid, mosaic, blastulation, biopsied, or D5/total biopsied. The DFI of >15% had more good quality D3 embryos than the <15% group, as did the >20% group compared with the <20% group. The ICSI fertilization was significantly higher in all 3 lower percentage groups compared with the higher counterpart. Standard IVF had significantly more blastocysts/fertilized suitable for biopsy and more D5/total number biopsied than ICSI embryos despite no difference in DFI.

Conclusions

The DFI at fertilization is correlated with decreased fertilization for ICSI and IVF.

Epigenetic markers in the embryonal germ cell development and spermatogenesis

Spermatogenesis is the process of generation of male reproductive cells from spermatogonial stem cells in the seminiferous epithelium of the testis. During spermatogenesis, key spermatogenic events such as stem cell self-renewal and commitment to meiosis, meiotic recombination, meiotic sex chromosome inactivation, followed by cellular and chromatin remodeling of elongating spermatids occur, leading to sperm cell production. All the mentioned events are at least partially controlled by the epigenetic modifications of DNA and histones. Additionally, during embryonal development in primordial germ cells, global epigenetic reprogramming of DNA occurs. In this review, we summarized the most important epigenetic modifications in the particular stages of germ cell development, in DNA and histone proteins, starting from primordial germ cells, during embryonal development, and ending with histone-to-protamine transition during spermiogenesis.

LncRNA8276 primes cell-cell adhesion for regulation of spermatogenesis

BACKGROUND

Human sperm concentration and motility have dropped dramatically (50%) in the past few decades, and environmental factors are involved in this decline. Long non-coding RNAs (lncRNA) have been discovered to be involved in many cellular processes including spermatogenesis.

OBJECTIVE

This investigation aimed to explore the role of lncRNA8276 in murine spermatogenesis.

MATERIALS AND METHODS

The expression of lncRNA8276 was modified by knockdown or overexpression in mouse testes and spermatogonial stem cells (C18-4 cell line). Sperm quality was determined in the F0 and F1 generations of mice. Furthermore, the underlying mechanisms were studied through gene expression and/or protein expression of spermatogenesis-related genes and cell junction-related genes by different methods.

RESULTS

In the current investigation, we discovered that sperm lncRNA8276 was decreased by NH3 /H2 S in three generations (F0, F1, and F2) of mouse sperm. In vivo testicular knockdown of lncRNA8276 led to a decline in sperm concentration and motility in both F0 (muF0) and F1 (muF1) generations Moreover, knockdown lncRNA8276 decreased the gene and protein levels of important genes related to cell-cell junctions and spermatogenesis. The data were further confirmed in mouse spermatogonia stem cell line C18-4 cells through knockdown of lncRNA8276.

DISCUSSION AND CONCLUSION

Our study suggests that lncRNA8276 may be involved in cell-cell junction formation in the mouse testis to regulate spermatogenesis. It may be a target for the modification of spermatogenesis and male fertility, or male contraception. This investigation offers a potential therapeutic strategy for male infertility.

Genetic and Epigenetic Evaluation of Human Spermatogonial Stem Cells Isolated by MACS in Different Two and Three-Dimensional Culture Systems

<strong>Objective: </strong>Epigenetic and genetic changes have important roles in stem cell achievements. Accordingly, the aim of this<br />study is the evaluation of the epigenetic and genetic alterations of different culture systems, considering their efficacy in<br />propagating human spermatogonial stem cells isolated by magnetic-activated cell sorting (MACS).<br /><strong>Materials and Methods:</strong> In this experimental study, obstructive azoospermia (OA) patient-derived spermatogonial cells were divided into two groups. The MACS enriched and non-enriched spermatogonial stem cells (SSCs) were cultured in the control and treated groups; co-culture of SSCs with Sertoli cells of men with OA, co-culture of SSCs with healthy Sertoli cells of fertile men, the culture of SSCs on PLA nanofiber and culture of testicular cell suspension. Gene-specific methylation by MSP, expression of pluripotency (NANOG, C-MYC and OCT-4), and germ cells specific genes (Integrin α6, Integrin β1, PLZF) evaluated. Cultured SSCs from the optimized group were transplanted into the recipient azoospermic mouse.<br /><strong>Results:</strong> The use of MACS for the purification of human stem cells was effective at about 69% with the culture of the testicular suspension, being the best culture system. Upon purification, the germ-specific gene expression was significantly higher in testicular cell suspension and treated groups (P≤0.05). During the culture time, gene-specific methylation patterns of the examined genes did not show any changes. Our data from transplantation indicated the homing of the donor-derived cells and the presence of human functional sperm.<br /><strong>Conclusion:</strong> Our in vivo and in vitro results confirmed that culture of testicular cell suspension and selection of<br />spermatogonial cells could be effective ways for purification and enrichment of the functional human spermatogonial cells. The epigenetic patterns showed that the specific methylation of the evaluated genes at this stage remained constant with no alteration throughout the entire culture systems over time.

EZH2 enhances proliferation and migration of trophoblast cell lines by blocking GADD45A-mediated p38/MAPK signaling pathway

Impaired activity of the trophoblasts is a major contributor to the progression of pregnancy pathologies including preeclampsia (PE). This research probed the function of enhancer of zeste homolog 2 (EZH2) in activity of trophoblast cells and its correlation with growth arrest and DNA damage inducible alpha (GADD45A). EZH2 was predicted to be downregulated in placental tissues in PE according to a gene chip analysis, and reduced expression of EZH2 was detected in the placental tissues of patients with PE. Overexpression of EZH2 augmented proliferation and invasiveness of two trophoblast cell lines HTR-8/SVneo and JEG3 cells. EZH2 catalyzed trimethylation of lysine 27 on histone 3 (H3K27me3) in GADD45A promoter to suppress its transcription. GADD45A silencing increased the activity of the trophoblast cell lines and inactivated the p38/mitogen-activated protein kinase (MAPK) signaling pathway. Rescue experiments confirmed that either inhibition of GADD45A or p38 restored the proliferation, migration, and invasiveness of the trophoblast cell lines suppressed by EZH2 silencing. In conclusion, this work suggests that EZH2 enhances activity of trophoblast cell lines by suppressing GADD45A-mediated p38/MAPK signaling pathway.

Global 5mC and 5hmC DNA Levels in Human Sperm Subpopulations with Differentially Protaminated Chromatin in Normo- and Oligoasthenozoospermic Males

Epigenetic modifications play a special role in the male infertility aetiology. Published data indicate the link between sperm quality and sperm chromatin protamination. This study aimed to determine the relationship between methylation (5mC) and hydroxymethylation (5hmC) in sperm DNA, with respect to sperm chromatin protamination in three subpopulations of fertile normozoospermic controls and infertile patients with oligo-/oligoasthenozoospermia. For the first time, a sequential staining protocol was applied, which allowed researchers to analyse 5mC/5hmC levels by immunofluorescence staining, with a previously determined chromatin protamination status (aniline blue staining), using the same spermatozoa. TUNEL assay determined the sperm DNA fragmentation level. The 5mC/5hmC levels were diversified with respect to chromatin protamination status in both studied groups of males, with the highest values observed in protaminated spermatozoa. The linkage between chromatin protamination and 5mC/5hmC levels in control males disappeared in patients with deteriorated semen parameters. A relationship between 5mC/5hmC and sperm motility/morphology was identified in the patient group. Measuring the 5mC/5hmC status of sperm DNA according to sperm chromatin integrity provides evidence of correct spermatogenesis, and its disruption may represent a prognostic marker for reproductive failure.

Epigenetics and Testicular Cancer: Bridging the Gap Between Fundamental Biology and Patient Care

Testicular cancer is the most common solid tumor affecting young males. Most testicular cancers are testicular germ cell tumors (TGCTs), which are divided into seminomas (SGCTs) and non-seminomatous testicular germ cell tumors (NSGCTs). During their development, primordial germ cells (PGCs) undergo epigenetic modifications and any disturbances in their pattern might lead to cancer development. The present study provides a comprehensive review of the epigenetic mechanisms–DNA methylation, histone post-translational modifications, bivalent marks, non-coding RNA–associated with TGCT susceptibility, initiation, progression and response to chemotherapy. Another important purpose of this review is to highlight the recent investigations regarding the identification and development of epigenetic biomarkers as powerful tools for the diagnostic, prognostic and especially for epigenetic-based therapy.

Transgenerational effects on the fecundity and sperm proteome in rats exposed to a mixture of pyrethroids at doses similar to human consumption

Pyrethroid based pesticide usage for crop protection resulted in percolation of these compounds into the food chain. Toxicological studies that reflect exposure to pyrethroids through food in the human settings are rare. We conducted animal experimentations using a mixture of pyrethroids that is equivalent to the amount consumed by average individual through rice and vegetables in the Indian context. Male rats treated with a mixture of pyrethroids for 1-12 months displayed decreased transgenerational fecundity, sperm count, activities of 3β- and 17β-HSD and perturbed hormonal profile. At the transcriptome level, the expression of genes involved in spermatogenesis, steroidogenesis, germ cell epigenetic modulators and germ cell apoptosis were altered in the testis. In the sperm lysates of control rats, 506 proteins identified by mass spectrometry. The differential expression of these proteins (treated/control ratio) in the pyrethroid exposed rats was analyzed. Among the 506 proteins, 153 had a ratio of 0; 41 had a ratio ranging from >0 to <0.5; and 10 had a ratio >2.0. Interestingly, the differential expression was transgenerational. 26 proteins that were differentially expressed in the sperm of F0 treated rats continued to remain the same in the F1, F2 and F3 generations, while the differential expression was maintained up to F2 and F1 generations for 46 and 2 proteins respectively. Some of the proteins that continued to be differentially expressed in the later generations are reported to have critical roles in male reproduction. These results indicate that the reduced fecundity observed in the later generations could be due to the continued differential expression that was initiated by pyrethroid treatment in the F0 rats. Results of our study, for the first time, provide evidence that long-term exposure to pyrethroids affects transgenerational fecundity manifested by changes in sperm proteome.

MicroRNA regulates the toxicological mechanism of four mycotoxins in vivo and in vitro

Mycotoxins can cause body poisoning and induce carcinogenesis, often with a high mortality rate. Therefore, it is of great significance to seek new targets that indicate mycotoxin activity and to diagnose and intervene in mycotoxin-induced diseases in their early stages. MicroRNAs (miRNAs) are physiological regulators whose dysregulation is closely related to the development of diseases. They are thus important markers for the occurrence and development of diseases. In this review, consideration is given to the toxicological mechanisms associated with four major mycotoxins (ochratoxin A, aflatoxin B1, deoxynivalenol, and zearalenone). The roles that miRNAs play in these mechanisms and the interactions between them and their target genes are explained, and summarize the important role of histone modifications in their toxicity. As a result, the ways that miRNAs are regulated in the pathogenicity signaling pathways are revealed which highlights the roles played by miRNAs in preventing and controlling the harmful effects of the mycotoxins. It is hoped that this review will provide a theoretical basis for the prevention and control of the damage caused by these mycotoxins.

Effects of glufosinate-ammonium on male reproductive health: Focus on epigenome and transcriptome in mouse sperm

Glufosinate-ammonium (GLA) is a widely used herbicide with emerging concern over its neural and reproductive toxicity. To uncover potential effects of GLA on male reproductive health in mammals, adult male C57BL/6J mice were administered 0.2 mg/kg·d GLA for 5 weeks. After examination on fertility, testis histology and semen quality in the GLA group, we performed deep sequencing to identify repressive epigenetic marks including DNA methylation and histone modifications (H3K27me3 and H3K9me3), together with mRNA transcript levels in sperm. Then, we integrated multi-omics sequencing data to comprehensively explore GLA-induced epigenetic and transcriptomic alterations. We found no significant difference either on fertility, testis histology or semen quality-related indicators. As for epigenome, the protein level of H3K27me3 was significantly increased in GLA sperm. Next generation sequencing showed alterations of these epigenetic marks and extensive transcription inhibition in sperm. These differential repressive marks were mainly distributed at intergenic regions and introns. According to results by Gene Ontology enrichment analysis, both differentially methylated and expressed genes were mainly enriched in pathways related to synapse organization. Subtle differences in genomic imprinting were also observed between the two groups. These results suggested that GLA predominantly impaired sperm epigenome and transcriptome in mice, with little effect on fertility, testis histology or semen quality. Further studies on human sperm using similar strategies need to be conducted for a better understanding of the male reproductive toxicity of GLA.

Epigenetic Modifications, A New Approach to Male Infertility Etiology: A Review

Recent studies have indicated that epigenetic alterations are critical for normal function and development of spermatozoa during the fertilization process. This review will focus on the latest advances in epigenome profiling of the chromatin modifications during sperm development, as well as the potential roles of epigenetic mechanisms in the context of male infertility. In this review, all data were collected from published studies that considered the effect of epigenetic abnormalities on human spermatogenesis, sperm parameters quality, fertilization process, embryo development and live births. The database PubMed was searched for all experimental and clinical studies using the Keywords "epigenetic modifications", "male infertility", "spermatogenesis", "embryo development" and "reproductive function". Post-translational modifications of histone, DNA methylations and chromatin remodeling are among the most common forms of epigenetic modifications that regulate all stages of spermatogenesis and fertilization process. Incorrect epigenetic modifications of certain genes involved in the spermatogenesis and sperm maturation may be a main reason of male reproductive disorder and infertility. Most importantly, abnormal patterns of epigenetic modifications or transgenerational phenotypes and miRNAs expression may be transmitted from one generation to the next through assisted reproductive techniques (ART) and cause an increased risk of birth defects, infertility and congenital anomalies in children. Epigenetic modifications must be considered as a one of the main factors of unexplained male infertility etiology. Due to high risk of transmitting incorrect primary imprints to offspring, there is a need for more research into epigenetic alterations in couples who benefit of ART support.

Downregulation of EZH2 in Trophoblasts Induces Decidual M1 Macrophage Polarization: a Potential Cause of Recurrent Spontaneous Abortion

Macrophages are known to be pivotal for ensuring the establishment of the immune tolerance microenvironment at the maternal–fetal interface. In particular, trophoblasts stay in close contact with decidual macrophages (DMs), which have been reported to play an active role in the modulation of the polarization of DMs. Thus, any dysfunction of trophoblasts might be associated with certain pregnancy‐related complications, such as recurrent spontaneous abortion (RSA). Enhancer of zeste homolog 2 (EZH2) is an important epigenetic regulatory gene that has been previously shown to be related to immune regulation. The present study assessed the expression of EZH2 in villi tissue obtained from healthy controls and RSA patients. Trophoblasts conditioned medium was collected to incubate macrophages differentiated from the THP‐1 cell line. The expression and function of EZH2 in trophoblasts were knocked down either by the use of siRNA or GSK126 as an inhibitor. Our results show a significant decrease in the expression of EZH2 in villi tissue from RSA patients as compared to healthy controls. Further, the inhibition of expression or function of EZH2 in trophoblasts promoted M1 macrophage polarization, which might be involved in the pathogenesis of RSA. Moreover, the suppression of EZH2 was found to affect the secretion of immune and inflammatory cytokines in trophoblasts. Altogether, these results indicated the importance of EZH2 in the regulation of immune functions of trophoblasts and thus highlighted its potential to be explored as a therapeutic target to prevent and treat pregnancy loss.

Environmental pollutants exposure and male reproductive toxicity: The role of epigenetic modifications

Male fertility rates have shown a progressive decrease in recent decades. There is a growing concern about the male reproductive dysfunction caused by environmental pollutants exposure, however the underlying molecular mechanisms are still not well understood. Epigenetic modifications play a key role in the biological responses to external stressors. Therefore, this review discusses the roles of epigenetic modifications in male reproductive toxicity induced by environmental pollutants, with a particular emphasis on DNA methylation, histone modifications and miRNAs. The available literature proposed that environmental pollutants can directly or cause oxidative stress and DNA damage to induce a variety of epigenetic changes, which lead to gene dysregulation, mitochondrial dysfunction and consequent male reproductive toxicity. However, future studies focusing on more kinds of epigenetic modifications and their crosstalk as well as epidemiological data are still required to fill in the current research gaps. In addition, the intrinsic links between pollutants-mediated epigenetic regulations and male reproduction-related physiological responses deserve to be further explored.

Effect of oral administration of a mixture of pyrethroids at doses relevant to human exposure on the general and male reproductive physiology in the rat

Studies on the effects of unintentional intake of pyrethroid pesticides that are akin to actual human exposure settings are very rare. Such an exposure is primarily by consuming the food products as routine diet that contain residual levels of pyrethroids. In this study, rats were orally administered for 15 months with a mixture of pyrethroids at a dose that is one-fifth (high dose; HD) or one-twenty fifth (low dose; LD) of the residual levels commonly present in the average amount of rice and vegetables consumed by Indian population. Lipid profile, kidney and liver function were assessed. Lipid peroxidation, nitric oxide, antioxidant enzyme activities and histopathological changes were analyzed in the liver, lung, kidney, pancreas, testes, caput, cauda and prostate. The effect on the male reproductive system as a function of sperm count, enzyme activity of 3β-HSD and 17β-HSD and the expression profile of genes involved in spermatogenesis, steroidogenesis, genetic reprogramming and apoptosis of male gametes were evaluated. Significant increase in the relative organ weight, perturbations in the activities of antioxidant enzymes, lipid profile and liver function were observed in both LD and HD groups. Damage to the anatomical architecture was evident in all the tissues due to pyrethroid toxicity. Exposure to LD and HD of pyrethroid mixture resulted in decreased sperm count, activities of 3β-HSD and 17β-HSD, impaired capacitation and acrosome reaction and perturbations in the expression of genes that govern male gamete production. Results of our study indicate that exposure to pyrethroids for longer durations even at doses that are far below the residual levels present in the food consumed will result in severe damage to general physiological processes as well as reproductive function.

Methylation patterns of methylenetetrahydrofolate reductase gene promoter in infertile males

Errors of folate/homocysteine pathways which are critical for transferring methyl groups have been suggested to affect male fertility. We aimed to evaluate the methylation patterns of the promoter of methylenetetrahydrofolate reductase (MTHFR) gene in infertile males and to investigate the association between MTHFR promoter methylation and success of sperm retrieval. Thirty-five nonobstructive azoospermic and 46 severe oligozoospermic patients constituted the study group and were compared with 49 fertile and/or normozoospermic men. The methylation status was analysed by methylation-specific polymerase chain reaction. MTHFR promoter methylation was detected in infertile men with NOA and SO in the ratio of 48.6% and 58.7%, respectively. Methylation was also observed in 51% of controls. MTHFR promoter was methylated in 65% of men with viable spermatozoon during TESE. No association was found regarding to the profile of MTHFR promoter methylation between both NOA and SO patients and controls (p = .621). There was no relation between the methylation status of MTHFR promoter and low motility and poor morphology (p = .682 and p = .413, respectively). No association was found between MTHFR promoter methylation and presence of viable spermatozoa (p = .382). Our data indicate that the promoter methylation of MTHFR gene may not be associated with male infertility.

Kisspeptins, new local modulators of male reproduction: A comparative overview

Spermatogenesis is a complex process that leads to the production of male gametes within the testis through the coordination of mitotic, meiotic and differentiation events, under a deep control of endocrine, paracrine and autocrine modulators along the Hypothalamus-pituitary-gonad (HPG) axis. The kisspeptin system plays a fundamental role along the HPG axis as it is the main positive modulator upstream of the hypothalamic neurons that secrete the Gonadotropin Releasing Hormone (GnRH), the decapeptide that supports pituitary gonadotropins and the production of gonadal sex steroid. Currently, kisspeptins and their receptor, KISS1R, have a recognized activity in the central control of puberty onset, sex maturation, reproduction and sex-steroid feedback mechanisms in both animal models and human. However, kisspeptin signaling has been widely reported in peripheral tissues, particularly in the testis of mammalian and non-mammalian vertebrates, with functions related to Leydig cells physiology and steroid biosynthesis, spermatogenesis progression and spermatozoa functions, but its mandatory role within the testis is still a matter of discussion. This review provides a summary of the main intratesticular effects of kisspeptin in vertebrates, via a comparative approach. Particular emphasis was devoted to data from the anuran amphibian Pelophylax esculentus, the first animal model in which the direct intratesticular activity of kisspeptin was reported.

Characterisation of sperm piRNAs and their correlation with semen quality traits in swine

Piwi-interacting RNAs (piRNAs) are a class of non-coding RNAs that are essential in the transcriptional silencing of transposable elements and warrant genome stability in the mammalian germline. In this study, we have identified piRNAs in porcine sperm using male germline and zygote datasets from human, mice, cow and pig, and evaluated the relation between their abundances and sperm quality traits. In our analysis, we identified 283 382 piRNAs, 1355 of which correlated with P ≤ 0.01 to at least one semen quality trait. Fifty-seven percent of the correlated piRNAs mapped less than 50 kb apart from any other piRNA in the pig genome. Furthermore, piRNA location was significantly enriched near long interspersed nuclear elements. Moreover, some of the significant piRNAs mapped within or close to genes relevant for fertility or spermatogenesis such as CSNK1G2 and PSMF1.

Effect of long-term treatment with a mixture of pyrethroids on the expression of genes that govern male germ cell production in rats

Humans are exposed to pyrethroid-based pesticides through agricultural produce. In this study, male Wistar rats were orally treated for 9 to 12 months with a mixture of pyrethroids that is equivalent to one-fifth (high dose; HD) or one-twenty fifth (low dose; LD) of the amount of pyrethroids present in the cereals and rice consumed by an average Indian. In rats treated for 9 months, the spermatogenesis-associated genes Abp, Ar, Cd9, Dax1, Dazap1, Ddx3y, Gdnf, Gfra1, Grth, Inhb, Ovol1, P1, Plzf, Pygo2, Scf, Tgfb1, Tp1, Tp2, and Vim1 were downregulated in both LD and HD groups. In rats treated for 12 months Gdnf, Hsf2, Inhb, Tgfb1, Thy1, and Ybx2 expression was downregulated in both LD and HD groups. Steroidogenesis-associated genes 17-β-Hsd, Gata4, Hmgcr, Hmgcs1, Pde4b, and Tspo gene expression were reduced in both LD- and HD-treated groups treated for 9 months. In 12-month-treated rats, Creb1 expression decreased in both LD and HD groups. The epigenetic reprogramming-associated genes, Dnmt1, Dnmt3a, Dnmt3b, Hdac10, Hp1bp3, Kat3a Kat3b, Mch2ta, Ncoa7, and Sirt1 were downregulated in both HD and LD groups of 9-months-treated rats. In rats treated for 12 months, Hdac10, Mch2ta, Ncoa7, and Sirt1 messenger RNA levels decreased in both the HD and LD groups. Thus, we demonstrate that long-term exposure to a mixture of pyrethroids caused aberrations in the transcriptome of factors involved in sperm production and development.

Unravelling how in vitro capacitation alters ram sperm chromatin before and after cryopreservation

BACKGROUND

Sperm chromatin structure provides valuable information for the prediction of male fertility and can be altered during different procedures. Previous studies have shown that sperm chromatin condensation decreased during in vitro capacitation. Moreover, cryopreservation can affect sperm DNA integrity and chromatin compaction.

OBJECTIVES

This study aimed to investigate dynamic modifications produced in the chromatin structure of ram spermatozoa during in vitro capacitation before and after cryopreservation.

MATERIALS AND METHODS

Chromatin decondensation (AB+), DNA methylation, DNA fragmentation index (%DFI) and high DNA stainability (HDS) were evaluated in fresh and frozen-thawed ram spermatozoa incubated under capacitating (CAP) conditions at 1, 5, 15, 30, 60, 120, 180 and 240 minutes and under non-capacitating (NC) conditions at 0, 15 and 240 minutes.

RESULTS

Incubation in NC conditions did not induce significant changes in chromatin condensation (P > .05; AB + and HDS). However, incubation of fresh and cryopreserved ram spermatozoa under CAP conditions significantly increased chromatin decondensation (P < .05), reaching the highest percentage of AB + and HDS from 180 to 240 minutes in fresh samples and from 5 to 30 minutes in cryopreserved samples. Both variables (HDS and AB+) were positively correlated with tyrosine phosphorylation, total motility, progressive motility, curvilinear velocity and amplitude of lateral head displacement, as well as between them under CAP conditions in fresh and cryopreserved spermatozoa. DNA methylation significantly increased in cryopreserved spermatozoa (P < .05), but only after extended incubation under CAP conditions (60-240 minutes), while the %DFI, albeit higher in cryopreserved samples, remained constant under CAP and NC conditions in both types of sample (P > .05).

DISCUSSION AND CONCLUSIONS

Our results suggest that sperm chromatin condensation decreased progressively during in vitro capacitation of ram spermatozoa, while sperm DNA integrity remained intact. Such changes in chromatin condensation appeared faster after sperm cryopreservation.

The role of environmental optimization for storing bulls' sperm cells

Artificial insemination has achieved a dynamic increase in genetic progress, and this is due to the improvement of sperm preservation technology. In recent years, a lot of attention has been paid to optimizing bull sperm storage environment and objectifying methods of sperm quality analysis. This review presents bull sperm preservation methods and ways to modify their storage environment. The main purpose of sperm preparation for artificial insemination is to obtain sperm with a high percentage of viable, motile sperm with normal morphology and low DNA fragmentation rates. Currently conducted experiments indicate the possibility of improving the quality of insemination doses produced using various components enriching common diluents. However, despite extensive research, no better results have been achieved than obtaining insemination doses with sperm viability that exceeds just over 60%. Obtaining a very good quality of frozen semen seems to be still unachievable today.

Environmental Impact on Male (In)Fertility via Epigenetic Route

In the last 40 years, male reproductive health-which is very sensitive to both environmental exposure and metabolic status-has deteriorated and the poor sperm quality observed has been suggested to affect offspring development and its health in adult life. In this scenario, evidence now suggests that epigenetics shapes endocrine functions, linking genetics and environment. During fertilization, spermatozoa share with the oocyte their epigenome, along with their haploid genome, in order to orchestrate embryo development. The epigenetic signature of spermatozoa is the result of a dynamic modulation of the epigenetic marks occurring, firstly, in the testis-during germ cell progression-then, along the epididymis, where spermatozoa still receive molecules, conveyed by epididymosomes. Paternal lifestyle, including nutrition and exposure to hazardous substances, alters the phenotype of the next generations, through the remodeling of a sperm epigenetic blueprint that dynamically reacts to a wide range of environmental and lifestyle stressors. With that in mind, this review will summarize and discuss insights into germline epigenetic plasticity caused by environmental stimuli and diet and how spermatozoa may be carriers of induced epimutations across generations through a mechanism known as paternal transgenerational epigenetic inheritance.

How defective spermatogenesis affects sperm DNA integrity

Spermatogenesis is the essential process to maintain and promote male fertility. It is extraordinarily complex with many regulatory elements and numerous steps. The process involves several cell types, regulatory molecules, repair mechanisms and epigenetic regulators. Evidence has shown that fertility can be negatively impacted by reduced sperm DNA integrity. Sources of sperm DNA damage include replication errors and causes of DNA fragmentation which include abortive apoptosis, defective maturation and oxidative stress. This review outlines the process of spermatogenesis, spermatogonial regulation and sperm differentiation; additionally, DNA damage and currently studied DNA repair mechanisms in spermatozoon are also covered.

Sperm Cryodamage in Ruminants: Understanding the Molecular Changes Induced by the Cryopreservation Process to Optimize Sperm Quality

Sperm cryopreservation represents a powerful tool for livestock breeding. Several efforts have been made to improve the efficiency of sperm cryopreservation in different ruminant species. However, a significant amount of sperm still suffers considerable cryodamage, which may affect sperm quality and fertility. Recently, the use of different “omics” technologies in sperm cryobiology, especially proteomics studies, has led to a better understanding of the molecular modifications induced by sperm cryopreservation, facilitating the identification of different freezability biomarkers and certain proteins that can be added before cryopreservation to enhance sperm cryosurvival. This review provides an updated overview of the molecular mechanisms involved in sperm cryodamage, which are in part responsible for the structural, functional and fertility changes observed in frozen–thawed ruminant sperm. Moreover, the molecular basis of those factors that can affect the sperm freezing resilience of different ruminant species is also discussed as well as the molecular aspects of those novel strategies that have been developed to reduce sperm cryodamage, including new cryoprotectants, antioxidants, proteins, nanoparticles and vitrification.

Low doses of carbendazim and chlorothalonil synergized to impair mouse spermatogenesis through epigenetic pathways

Pesticides have been extensively produced and used to help the agricultural production which leads to the contamination of the environment, soil, groundwater sources, and even foodstuffs. Fungicides carbendazim (CBZ) and chlorothalonil (Chl) are widely applied in agriculture and other aspects. CBZ or Chl have been reported to disrupt spermatogenesis and decrease semen quality. However, it is not understood the effects of pubertal exposure to low doses of CBZ and Chl together, and the underlying mechanisms. Therefore, the aim of current investigation was to explore the negative impacts of pubertal exposure to low doses of CBZ and Chl together on spermatogenesis and the role of epigenetic modifications in the process. We demonstrated that CBZ and Chl together synergize to decrease sperm motility in vitro (CBZ 1.0 + Chl 0.1, CBZ 10.0 + CHl 1.0, CBZ 100.0 + Chl 10 μM in incubation medium for 24 h) and sperm concentration and motility in vivo with ICR mice (CBZ 0.1 + Chl 0.1, CBZ 1.0 + CHl 1.0, CBZ 10.0 + Chl 10 mg/kg body weight; oral gavage for five weeks). CBZ + Chl significantly increase reactive oxygen species (ROS) and apoptosis by the increase in the protein level of caspase 8 in vitro. Moreover, CBZ + Chl synergized to disrupt mouse spermatogenesis with the disturbance in sperm production proteins and sperm proteins (VASA, A-Myb, STK31, AR, Acrosin). CBZ + Chl synergized to decrease the protein level of estrogen receptor alpha and the protein level of DNA methylation marker 5 mC in Leydig cells, and to increase the protein levels of histone methylation marker H3K9 and the methylation enzyme G9a in germ cells. Therefore, greater attention should be paid to the use of CBZ and Chl as pesticides to minimise their adverse impacts on spermatogenesis.

Does co-transplantation of mesenchymal and spermatogonial stem cells improve reproductive efficiency and safety in mice?

Background

Spermatogonial stem cell transplantation (SSCT) is a promising therapy in restoring the fertility of childhood cancer survivors. However, the low efficiency of SSCT is a significant concern. SSCT could be improved by co-transplanting transforming growth factor beta 1 (TGFβ1)-induced mesenchymal stem cells (MSCs). In this study, we investigated the reproductive efficiency and safety of co-transplanting spermatogonial stem cells (SSCs) and TGFβ1-induced MSCs.

Methods

A mouse model for long-term infertility was used to transplant SSCs (SSCT, n = 10) and a combination of SSCs and TGFβ1-treated MSCs (MSi-SSCT, n = 10). Both transplanted groups and a fertile control group (n = 7) were allowed to mate naturally to check the reproductive efficiency after transplantation. Furthermore, the testes from transplanted males and donor-derived male offspring were analyzed for the epigenetic markers DNA methyltransferase 3A (DNMT3A) and histone 4 lysine 5 acetylation (H4K5ac).

Results

The overall tubular fertility index (TFI) after SSCT (76 ± 12) was similar to that after MSi-SSCT (73 ± 14). However, the donor-derived TFI after MSi-SSCT (26 ± 14) was higher compared to the one after SSCT (9 ± 5; P = 0.002), even after injecting half of the number of SSCs in MSi-SSCT. The litter sizes after SSCT (3.7 ± 3.7) and MSi-SSCT (3.7 ± 3.6) were similar but differed significantly with the control group (7.6 ± 1.0; P < 0.001). The number of GFP⁺ offspring per litter obtained after SSCT (1.6 ± 0.5) and MSi-SSCT (2.0 ± 1.0) was also similar. The expression of DNMT3A and H4K5ac in germ cells of transplanted males was found to be significantly reduced compared to the control group. However, in donor-derived offspring, DNMT3A and H4K5ac followed the normal pattern.

Conclusion

Co-transplanting SSCs and TGFβ1-treated MSCs results in reproductive efficiency as good as SSCT, even after transplanting half the number of SSCs. Although transplanted males showed lower expression of DNMT3A and H4K5ac in donor-derived germ cells, the expression was restored to normal levels in germ cells of donor-derived offspring. This procedure could become an efficient method to restore fertility in a clinical setup, but more studies are needed to ensure safety in the long term.

Estrogen Receptor-Related DNA and Histone Methylation May Be Involved in the Transgenerational Disruption in Spermatogenesis by Selective Toxic Chemicals

Air pollution is a global threat to human health especially spermatogenesis. Animal and epidemiological studies suggest that epigenetic factors can transmit the pathologies transgenerationally. Paternal epigenetic effects can greatly impact offspring health. In this study and together with our previous report, we found that H₂S donor Na₂S and/or NH₃ donor NH₄Cl diminished mouse fertility, decreased spermatozoa concentration and motility, and impaired spermatogenesis in three consequent generations (F0, F1, and F2). In the current study, we found that DNA methylation, histone methylation, and estrogen receptor alpha (ERα) were impaired by NH₄Cl and/or Na₂S in F0, F1, and F2 mouse testes. Moreover, NH₄Cl and/or Na₂S might act as environmental endocrine-disrupting chemicals to decrease estrogen and testosterone in mouse blood. It has been reported that ERα signaling is intertwined together with DNA methylation and histone methylation, which plays very important roles in spermatogenesis. These data together indicate that the transgenerational disruption in spermatogenesis by NH₄Cl and/or Na₂S may be through ERα-related DNA methylation and histone methylation pathways. Therefore, we strongly recommend that greater attention should be paid to NH₃ and/or H₂S contamination to minimize their impact on human health especially spermatogenesis.

Updates on the Effect of Mycotoxins on Male Reproductive Efficiency in Mammals

Mycotoxins are ubiquitous and unavoidable harmful fungal products with the ability to cause disease in both animals and humans, and are found in almost all types of foods, with a greater prevalence in hot humid environments. These mycotoxins vary greatly in structure and biochemical effects; therefore, by better understanding the toxicological and pathological aspects of mycotoxins, we can be better equipped to fight the diseases, as well as the biological and economic devastations, they induce. Multiple studies point to the association between a recent increase in male infertility and the increased occurrence of these mycotoxins in the environment. Furthermore, understanding how mycotoxins may induce an accumulation of epimutations during parental lifetimes can shed light on their implications with respect to fertility and reproductive efficiency. By acknowledging the diversity of mycotoxin molecular function and mode of action, this review aims to address the current limited knowledge on the effects of these chemicals on spermatogenesis and the various endocrine and epigenetics patterns associated with their disruptions.

Low dose chlorothalonil impairs mouse spermatogenesis through the intertwining of Estrogen Receptor Pathways with histone and DNA methylation

Recently, environment contaminants including pesticides, fungicides, mycotoxin and others chemicals have been suggested to be responsible for the decline in the human spermatozoa quality especially motility and the increase in infertility rate. Chlorothalonil is used widely for protection of vegetables and crops because it is a broad spectrum fungicide. It has been reported that chronic occupational exposure to fungicides was associated with poor spermatozoa morphology in young men. The pubertal period is very important for the male reproductive system development due to spermatogonial cell proliferation, the expansion of meiotic and haploid germ cells. Although some investigations have studied the male reproductive toxicity of chlorothalonil, almost no studies focused on spermatogenesis. The aim of our current investigation was to explore the impacts of chlorothalonil on spermatogenesis and the underlying mechanisms. It demonstrates: i) chlorothalonil decreased boar spermatozoa motility in vitro and increased the cell apoptosis; ii) chlorothalonil inhibited mouse spermatogenesis in vivo; iii) chlorothalonil disturbed spermatogenesis through the disruption of estrogen receptor signalling; iv) chlorothalonil disrupted histone methylation and DNA methylation which might be through estrogen signalling pathways. Due to the over use or incorrect use, chlorothalonil might cause serious problems to human health, especially spermatogenesis. Therefore we strongly recommend that greater attention should be paid to this fungicide to minimise its impact on human health especially spermatogenesis.

Enhanced immunological detection of epigenetic modifications of DNA in healthy and cancerous cells by fluorescence microscopy

Epigenetic modifications of DNA, including methylation, hydroxymethylation, formylation, and carboxylation of cytosines, are proposed to function in gene regulation during reproduction and development. Changes in cytosine methylation are associated with a range of diseases, such as cancer. Immunofluorescence uses specific antibodies to quantitatively detect the global amount of cytosine modifications by fluorescence microscopy. The most critical stage of immunofluorescence is the antigen retrieval to remove the protein content around the DNA, allowing specific antibodies to bind to DNA epitopes. Acid treatments have commonly been used for antigen retrieval. Previously, trypsin was added after acid in the protocol, which increased the amount of detectable DNA methylation. In this study, the protocol was further enhanced by the addition of pepsin, which is able to target charged hydrophobic amino acids in proteins, unlike trypsin, which breaks positive hydrophilic amino acids. The global levels of cytosine modifications in CF-1, HeLa, and AR42J cells were compared using this protocol. In all cells, the sequential treatment of trypsin and pepsin increased the specificity of the staining. With the synergistic effect of the two enzymes, it is possible to target different protein groups packaging DNA molecules and removing them effectively. The findings suggest that this revised protocol can be conveniently used for each cytosine modification in the cells examined, and should be optimized for other cells. These new antigen retrieval conditions may more accurately detect the changes in cytosine modifications during development and in diseases.

Low dose carbendazim disrupts mouse spermatogenesis might Be through estrogen receptor related histone and DNA methylation

Pesticides, fungicides are reportedly involved in a decline in spermatozoa quality, especially motility, and a consequent increase in the rate of infertility. Fungicide carbendazim (CBZ) is widely used in agriculture and other aspects. Although CBZ is known to disrupt spermatogenesis, causing a decrease in spermatozoa concentration and motility, the mechanisms are not fully understood. We aimed to further explore the underlying mechanisms of CBZ disruption of spermatogenesis. Pubertal mice were exposed to low doses (0.1, 1 and 10 mg/kg body weight) of CBZ for 5 weeks, then many factors related to spermatogenesis have been explored. It was found that 0.1-10 mg/kg body weight of CBZ exposure decreased mouse sperm motility and concentration, diminished the important protein factors (VASA, PGK2, B-Amy and CREM) for spermatogenesis, reduced sperm protein acrosin level, disrupted very vital epigenetic factors H3K27, 5 mC and 5 hmC. Furthermore, CBZ exposure damaged estrogen receptor alpha (ERα) pathway by decreased the protein levels of ERα and its targets PI3K and AKT. In summary low doses of CBZ exposure disrupted mouse spermatogenesis through estrogen receptor signaling; and that histone methylation and DNA methylation might play vital roles in CBZ disturbance of spermatogenesis through intertwining with estrogen signaling pathways. CBZ from the contamination in environment or food chain poses a serious threat to the normal development of spermatozoa. Therefore we strongly recommend to minimise the use of CBZ since it causes the severe issues on spermatogenesis.

Meclofenamic acid represses spermatogonial proliferation through modulating m6A RNA modification

Background

N6-Methyladenosine (m⁶A), the most prevalent modification in mammalian mRNA, plays important roles in numerous biological processes. Several m⁶A associated proteins such as methyltransferase like 3 (METTL3), methyltransferase like 14 (METTL14), α-ketoglutarate-dependent dioxygenase AlkB homolog 5 (ALKBH5) and YTH domain containing 2 (YTHDC2) are involved in the regulation of spermatogenesis and oogenesis. However, the role of the first detected m6A demethylase, fat mass and obesity associate protein (FTO), in germ cells remains elusive. Elucidation of FTO roles in the regulation of germ cell fate will provide novel insights into the mammalian reproduction.

Methods

Mouse GC-1 spg cells were treated with the ester form of meclofenamic acid (MA2) to inhibit the demethylase activity of FTO. The cellular m⁶A and m⁶A_m level were analyzed through high performance liquid chromatography combined with tandem mass spectrometry (HPLC/MS-MS). The cell apoptosis was detected via TUNEL and flow cytometry. The cell proliferation was detected through EdU and western blot. The mRNA level of core cyclin dependent kinases (CDKs) was quantified via q-PCR. RNA decay assay were performed to detect RNA stability. Dual fluorescence assay was conducted to study whether MA2 affects the expression of CDK2 dependent on the m⁶A modification at 3’UTR.

Results

MA2 significantly increased the cellular m⁶A level and down-regulated the expression of CDK1, CDK2, CDK6 and CdC25a, resulting in arrest of G1/S transition and decrease of cell proliferation. MA2 downregulated CDK2 mRNA stability. Additionally, mutation of the predicted m⁶A sites in the Cdk2–3’UTR could mitigated the degradation of CDK2 mRNA after MA2 treatment.

Conclusion

MA2 affected CDKs expression through the m⁶A-dependent mRNA degradation pathway, and thus repressed spermatogonial proliferation.

Electronic supplementary material

The online version of this article (10.1186/s40104-019-0361-6) contains supplementary material, which is available to authorized users.

Decreased global DNA hydroxymethylation in neural tube defects: Association with polycyclic aromatic hydrocarbons

5-Hydroxymethylcytosine (5hmC), a distinct epigenetic marker that plays a role in DNA active demethylation, has been reported to be important for embryonic development and may respond to environmental exposure. No studies have evaluated the association between DNA hydroxymethylation and the risk for fetal neural tube defects (NTDs), with consideration of prenatal exposure to polycyclic aromatic hydrocarbons (PAHs), a risk factor for NTDs. We measured the global levels of 5hmC% in neural tissue from 92 terminated NTD cases and 33 terminated non-malformed fetuses. A lower level of 5hmC% was found in the NTD cases (median [interquartile range]: 0.25 [0.12-0.39]) compared to the controls (0.45 [0.19-1.00]). After adjusting for periconceptional folate supplementation, risk for NTDs increased with decreasing tertiles of 5hmC% (odds ratio: 7.89, 95% confidence interval: 2.32, 26.86, for the lowest tertile relative to the top tertile; p_{for trend} = 0.002). Linear regression revealed that concentrations of high-molecular-weight PAHs (H_PAHs) in fetal liver tissue were negatively associated with log2-transformed 5hmC%. Superoxide dismutase activity and 5hmC% were positively correlated in fetal neural tissue (r_s = 0.64; p < 0.05). A mouse whole-embryo culture model was used for further validation. Decreased levels of 5hmC% and increased levels of reactive oxygen species were found in mouse embryos treated with BaP, a well-studied PAH. Taken together, levels of 5hmC% in fetal neural tissue were inversely associated with the risk for NTDs, and this association may be related to oxidative stress induced by exposure to PAHs.

Gestational exposure to low-dose zearalenone disrupting offspring spermatogenesis might be through epigenetic modifications

Zearalenone (ZEA), a F-2 mycotoxin produced by Fusarium, has been found to be an endocrine disruptor through oestrogen receptor signalling pathway to impair spermatogenesis. The disruption on reproductive systems by ZEA exposure might be transgenerational. In our previous report, we have found that low dose (lower than no-observed effect level, NOEL) of ZEA impaired mouse spermatogenesis and decreased mouse semen quality. The purpose of the current investigation was to explore the impacts of low-dose ZEA on spermatogenesis in the offspring after prenatal exposure and the underlying mechanisms. And it demonstrated that prenatal low-dose ZEA exposure disrupted the meiosis process to inhibit the spermatogenesis in offspring and even to diminish the semen quality by the decrease in spermatozoa motility and concentration. The DNA methylation marker 5hmC was decreased, the histone methylation markers H3K9 and H3K27 were elevated, and oestrogen receptor alpha was reduced in the offspring testis after prenatal low-dose ZEA exposure. The data suggest that the disruption in spermatogenesis by prenatal low-dose ZEA exposure may be through the modifications on epigenetic pathways (DNA methylation and histone methylation) and the interactions with oestrogen receptor signalling pathway. Moreover, in the current study, the male offspring were indirectly exposed to low-dose ZEA through placenta and the spermatogenesis in offspring was disrupted which suggested that the toxicity of ZEA on reproductive systems was very severe. Therefore, we strongly recommend that greater attention should be paid to this mycotoxin to minimize its adverse impact on human spermatogenesis.

The Attenuation of Trophoblast Invasion Caused by the Downregulation of EZH2 Is Involved in the Pathogenesis of Human Recurrent Miscarriage

Recurrent miscarriage (RM) is currently defined as two or more losses of a clinically established intrauterine pregnancy. Despite years of research, RM continues to be a clinically frustrating challenge for patients and physicians, and its etiology remains poorly understood. Accumulating evidence has suggested that epigenetic modifications are involved in early embryogenesis, and defects in epigenetic patterning contribute to the development of RM. Here, we studied the role of enhancer of zeste homolog 2 (EZH2) in the pathogenesis of RM and found that the EZH2 expression was significantly decreased in the villi from women with RM compared with that in control villi. EZH2 promoted the invasion of trophoblast cells. Moreover, EZH2 could promote epithelial-mesenchymal transition by epigenetically silencing CDX1. Both chromatin immunoprecipitation (ChIP)-PCR and dual-luciferase report assays demonstrated that EZH2 repressed CDX1 transcription via direct binding to its promoter region and then trimethylating Histone3-Lysine27. Furthermore, we discovered that progesterone, which is used extensively in the treatment of miscarriage and RM, increased the expression of EZH2 via the extracellular signaling-regulated kinase (ERK1/2) pathway. These findings revealed that EZH2 may regulate trophoblast invasion as an epigenetic factor, suggesting that EZH2 might be a potential therapeutic target for RM.

Sperm nuclear protamines: A checkpoint to control sperm chromatin quality

Protamines are nuclear proteins which are specifically expressed in haploid male germ cells. Their replacement of histones and binding to DNA is followed by chromatin hypercondensation that protects DNA from negative influences by environmental factors. Mammalian sperm contain two types of protamines: PRM1 and PRM2. While the proportion of the two protamines is highly variable between different species, abnormal ratios within a species are known to be associated with male subfertility. Therefore, it is more than likely that correct protamine expression represents a kind of chromatin checkpoint during sperm development rendering protamines as suitable biomarkers for the estimation of sperm quality. This review presents an overview of our current knowledge on protamines comparing gene and protein structures between different mammalian species with particular consideration given to man, mouse and stallion. At last, recent insights into the possible role of inherited sperm histones for early embryo development are provided.