Histone modification signatures in human sperm distinguish clinical abnormalities

Sperm chromatin: Evaluation, epigenetic signatures and relevance for embryo development and assisted reproductive technology outcomes

Sperm chromatin is distinct from somatic cell chromatin, as a result of extensive remodeling during the final stages of spermatogenesis. In this process, the majority of histones is replaced with protamines. The chromatin is consequently highly condensed and inert, which facilitates protection of the DNA. The sperm epigenomic landscape is shaped by histone retention, histone and protamine modification, DNA methylation, and RNAs. In recent years, sperm chromatin integrity and its epigenetic marks have been increasingly studied, and the constitution of sperm chromatin is steadily being uncovered. This growing body of research prompts assessment of the frequently overlooked involvement of sperm in fertility and embryonic development. Moreover, numerous endogenous and exogenous factors are known to affect sperm chromatin, which may in turn impact the reproductive success. Concerns have been raised about the effects of assisted reproductive technology (ART) on the sperm epigenome, embryonic development and offspring health. This review examines the structure and epigenetic signatures of sperm chromatin in the context of fertility and early embryonic development. Additionally, sperm chromatin evaluation and causes of aberrant integrity are outlined. Building on the knowledge discussed in the current review, future research should aim to elucidate the intricate relationship between all aspects of sperm chromatin and embryo development. This could lead to the uncovering of new targets for treating infertility, as well as the acquisition of much needed insights into the possible reciprocal association between ART and sperm chromatin integrity.

TLR signaling pathway and the effects of main immune cells and epigenetics factors on the diagnosis and treatment of infertility and sterility

Recurrent pregnancy loss (RPL), often known as spontaneous miscarriages occurring two or more times in a row, is a reproductive disease that affects certain couples. The cause of RPL is unknown in many cases, leading to difficulties in therapy and increased psychological suffering in couples. Toll-like receptors (TLR) have been identified as crucial regulators of inflammation in various human tissues. The occurrence of inflammation during parturition indicates that Toll-like receptor activity in tissues related to pregnancy may play a crucial role in the onset and continuation of normal function, as well as in various pregnancy complications like infection-related preterm. TLRs or their signaling molecules may serve as effective therapeutic targets for inhibiting premature activity. At the maternal-fetal interface, TLRs are found in both immune and non-immune cells, such as trophoblasts and decidual cells. TLR expression patterns are influenced by the phases of pregnancy. In this way, translational combinations like epigenetics, have indicated their impact on the TLRs.Importantly, abnormal DNA methylation patterns and histone alterations have an impressive performance in decreasing fertility by influencing gene expression and required molecular and cellular activities which are vital for a normal pregnancy and embryonic process. TLRs, play a central duty in the innate immune system and can regulate epigenetic elements by many different signaling pathways. The potential roles of TLRs in cells, epigenetics factors their ability to identify and react to infections, and their place in the innate immune system will all be covered in this narrative review essay.

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.

H2BFWT Variations in Sperm DNA and Its Correlation to Pregnancy

Abnormalities in sperm nuclei and chromatin can interfere with normal fertilization, embryonic development, implantation, and pregnancy. We aimed to study the impact of H2BFWT gene variants in sperm DNA on ICSI outcomes in couples undergoing ART treatment. One hundred and nineteen partners were divided into pregnant (G1) and non-pregnant (G2) groups. After semen analysis, complete DNA was extracted from purified sperm samples. The sequence of the H2BFWT gene was amplified by PCR and then subjected to Sanger sequencing. The results showed that there are three mutations in this gene: rs7885967, rs553509, and rs578953. Significant differences were shown in the distribution of alternative and reference alleles between G1 and G2 (p = 0.0004 and p = 0.0020, respectively) for rs553509 and rs578953. However, there was no association between these SNPs and the studied parameters. This study is the first to shed light on the connection between H2BFWT gene variants in sperm DNA and pregnancy after ICSI therapy. This is a pilot study, so further investigations about these gene variants at the transcriptional and translational levels will help to determine its functional consequences and to clarify the mechanism of how pregnancy can be affected by sperm DNA.

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.

Differential sperm histone retention in normozoospermic ejaculates of infertile men negatively affects sperm functional competence and embryo quality

BACKGROUND

The unique epigenetic architecture that sperm cells acquire during spermiogenesis by retaining <15% of either canonical or variant histone proteins in their genome is essential for normal embryogenesis. Whilst heterogeneous levels of retained histones are found in morphologically normal spermatozoa, their effect on reproductive outcomes is not fully understood.

METHODS

Processed spermatozoa (n = 62) were tested for DNA integrity by sperm chromatin dispersion assay, and retained histones were extracted and subjected to dot-blot analysis. The impact of retained histone modifications in normozoospermic patients on sperm functional characteristics, embryo quality, metabolic signature in embryo spent culture medium and pregnancy outcome was studied.

RESULTS

Dot-blot analysis showed heterogeneous levels of retained histones in the genome of normozoospermic ejaculates. Post-wash sperm yield was affected by an increase in H3K27Me3 and H4K20Me3 levels in the sperm chromatin (p < 0.05). Also, spermatozoa with higher histone H3 retention had increased DNA damage (p < 0.05). Spermatozoa from these cohorts, when injected into donor oocytes, correlated to a significant decrease in the fertilisation rate with an increase in sperm histone H3 (p < 0.05) and H3K27Me3 (p < 0.01). An increase in histone H3 negatively affected embryo quality (p < 0.01) and clinical pregnancy outcome post-embryo transfer (p < 0.05). On the other hand, spent culture medium metabolites assessed by high-resolution (800 MHz) nuclear magnetic resonance showed an increased intensity of the amino acid methionine in the non-pregnant group than in the pregnant group (p < 0.05) and a negative correlation with sperm histone H3 in the pregnant group (p < 0.05).

DISCUSSION AND CONCLUSION

Histone retention in spermatozoa can be one of the factors behind the development of idiopathic male infertility. Such spermatozoa may influence embryonic behaviour and thereby affect the success rate of assisted reproductive technology procedures. These results, although descriptive in nature, warrant further research to address the underlying mechanisms behind these clinically important observations.

Etiology of Male Infertility: an Update

Spermatogenesis is a complex process of germ cell division and differentiation that involves extensive cross-talk between the developing germ cells and the somatic testicular cells. Defective endocrine signaling and/or intrinsic defects within the testes can adversely affect spermatogenic progression, leading to subfertility/infertility. In recent years, male infertility has been recognized as a global public health concern, and research over the last few decades has elucidated the complex etiology of male infertility. Congenital reproductive abnormalities, genetic mutations, and endocrine/metabolic dysfunction have been demonstrated to be involved in infertility/subfertility in males. Furthermore, acquired factors like exposure to environmental toxicants and lifestyle-related disorders such as illicit use of psychoactive drugs have been shown to adversely affect spermatogenesis. Despite the large body of available scientific literature on the etiology of male infertility, a substantial proportion of infertility cases are idiopathic in nature, with no known cause. The inability to treat such idiopathic cases stems from poor knowledge about the complex regulation of spermatogenesis. Emerging scientific evidence indicates that defective functioning of testicular Sertoli cells (Sc) may be an underlying cause of infertility/subfertility in males. Sc plays an indispensable role in regulating spermatogenesis, and impaired functional maturation of Sc has been shown to affect fertility in animal models as well as humans, suggesting abnormal Sc as a potential underlying cause of reproductive insufficiency/failure in such cases of unexplained infertility. This review summarizes the major causes of infertility/subfertility in males, with an emphasis on infertility due to dysregulated Sc function.

Genome and Epigenome Disorders and Male Infertility: Feedback from 15 Years of Clinical and Research Experience

Infertility affects around 20% of couples of reproductive age; however, in some societies, as many as one-third of couples are unable to conceive. Different factors contribute to the decline of male fertility, such us environmental and professional exposure to endocrine disruptors, oxidative stress, and life habits with the risk of de novo epigenetics dysregulation. Since the fantastic development of new "omes and omics" technologies, the contribution of inherited or de novo genomes and epigenome disorders to male infertility have been further elucidated. Many other techniques have become available to andrology laboratories for the investigation of genome and epigenome integrity and the maturation and the competency of spermatozoa. All these new methods of assessment are highlighting the importance of genetics and epigenetics investigation for assisted reproduction pathology and for supporting professionals in counselling patients and proposing different management strategies for male infertility. This aims to improve clinical outcomes while minimizing the risk of genetics or health problems at birth.

Bull Sperm SWATH-MS-Based Proteomics Reveals Link between High Fertility and Energy Production, Motility Structures, and Sperm-Oocyte Interaction

The prediction of male or semen fertility potential remains a persistent challenge that has yet to be fully resolved. This work analyzed several in vitro parameters and proteome of spermatozoa in bulls cataloged as high- (HF; n = 5) and low-field (LF; n = 5) fertility after more than a thousand artificial inseminations. Sperm motility was evaluated by computer-assisted sperm analysis. Sperm viability, mitochondrial membrane potential (MMP) and reactive oxygen species (mROS) of spermatozoa were assessed by flow cytometry. Proteome was evaluated by the SWATH-MS procedure. Spermatozoa of HF bulls showed significantly higher total motility than the LF group (41.4% vs 29.7%). Rates of healthy sperm (live, high MMP, and low mROS) for HF and LF bull groups were 49% and 43%, respectively (p > 0.05). Spermatozoa of HF bulls showed a higher presence of differentially abundant proteins (DAPs) related to both energy production (COX7C), mainly the OXPHOS pathway, and the development of structures linked with the motility process (TPPP2, SSMEM1, and SPAG16). Furthermore, we observed that equatorin (EQTN), together with other DAPs related to the interaction with the oocyte, was overrepresented in HF bull spermatozoa. The biological processes related to protein processing, catabolism, and protein folding were found to be overrepresented in LF bull sperm in which the HSP90AA1 chaperone was identified as the most DAP. Data are available via ProteomeXchange with identifier PXD042286.

Hexachlorocyclohexane impairs human sperm motility by affecting lysine glutarylation and mitochondrial functions

Decreased sperm motility is a leading cause of male infertility and persistent organic pollutants are known to contribute significantly to the development of this disease. The effects of organochlorine pesticides such as hexachlorocyclohexane (HCH) on human sperm function and their mechanisms of action have received much attention, but are still not fully understood. Herein, we discovered that HCH has a concentration- and time-dependent inhibitory effect on human sperm motility in vitro. Moreover, HCH could reduce the levels of lysine glutarylation (Kglu) and glucose-6-phosphate dehydrogenase activity in sperm. Meanwhile, HCH could increase reactive oxygen species and thereby lead to mitochondrial depolarization and the down-regulation of adenosine triphosphate levels. In particular, we observed that sodium glutarate (Na-glu), the precursor of glutaryl-CoA, could alleviate the inhibitory effect of HCH on sperm Kglu levels, whereas the ROS scavenger N-acetyl-L-cysteine (NAC) had no effect. Intriguingly, both Na-glu and NAC were able to partially inhibit the HCH-induced increase in sperm ROS levels and impaired sperm motility. In conclusion, we propose that HCH inhibits sperm Kglu, leading to the disruption of mitochondrial energy metabolism, which in turn adversely affects sperm motility.

Nucleosomes in mammalian sperm: conveying paternal epigenetic inheritance or subject to reprogramming between generations?

The genome of mammalian sperm is largely packaged by sperm-specific proteins termed protamines. The presence of some residual nucleosomes has, however, emerged as a potential source of paternal epigenetic inheritance between generations. Sperm nucleosomes bear important regulatory histone marks and locate at gene-regulatory regions, functional elements, and intergenic regions. It is unclear whether sperm nucleosomes are retained at specific genomic locations in a deterministic manner or are randomly preserved due to inefficient exchange of histones by protamines. Recent studies indicate heterogeneity in chromatin packaging within sperm populations and an extensive reprogramming of paternal histone marks post fertilization. Obtaining single-sperm nucleosome distributions is fundamental to estimating the potential of sperm-borne nucleosomes in instructing mammalian embryonic development and in the transmission of acquired phenotypes.

Towards a Multi-Omics of Male Infertility

Infertility is a common problem affecting one in six couples and in 30% of infertile couples, the male factor is a major cause. A large number of genes are involved in spermatogenesis and a significant proportion of male infertility phenotypes are of genetic origin. Studies on infertility have so far primarily focused on chromosomal abnormalities and sequence variants in protein-coding genes and have identified a large number of disease-associated genes. However, it has been shown that a multitude of factors across various omics levels also contribute to infertility phenotypes. The complexity of male infertility has led to the understanding that an integrated, multi-omics analysis may be optimal for unravelling this disease. While there is a vast array of different factors across omics levels associated with infertility, the present review focuses on known factors from the genomics, epigenomics, transcriptomics, proteomics, metabolomics, glycomics, lipidomics, miRNomics, and integrated omics levels. These include: repeat expansions in AR, POLG, ATXN1, DMPK, and SHBG, multiple SNPs, copy number variants in the AZF region, disregulated miRNAs, altered H3K9 methylation, differential MTHFR, MEG3, PEG1, and LIT1 methylation, altered protamine ratios and protein hypo/hyperphosphorylation. This integrative review presents a step towards a multi-omics approach to understanding the complex etiology of male infertility. Currently only a few genetic factors, namely chromosomal abnormalities and Y chromosome microdeletions, are routinely tested in infertile men undergoing intracytoplasmic sperm injection. A multi-omics approach to understanding infertility phenotypes may yield a more holistic view of the disease and contribute to the development of improved screening methods and treatment options. Therefore, beside discovering as of yet unknown genetic causes of infertility, integrating multiple fields of study could yield valuable contributions to the understanding of disease development. Future multi-omics studies will enable to synthesise fragmented information and facilitate biomarker discovery and treatments in male infertility.

Molecular Markers: A New Paradigm in the Prediction of Sperm Freezability

For decades now, sperm cryopreservation has been a pillar of assisted reproduction in animals as well as humans. Nevertheless, the success of cryopreservation varies across species, seasons, and latitudes and even within the same individual. With the dawn of progressive analytical techniques in the field of genomics, proteomics, and metabolomics, new options for a more accurate semen quality assessment have become available. This review summarizes currently available information on specific molecular characteristics of spermatozoa that could predict their cryotolerance before the freezing process. Understanding the changes in sperm biology as a result of their exposure to low temperatures may contribute to the development and implementation of appropriate measures to assure high post-thaw sperm quality. Furthermore, an early prediction of cryotolerance or cryosensitivity may lead to the establishment of customized protocols interconnecting adequate sperm processing procedures, freezing techniques, and cryosupplements that are most feasible for the individual needs of the ejaculate.

Proteomic and genetic dissection of testis-specific histone 2B in infertile men reveals its contribution to meiosis and sperm motility

OBJECTIVE

To investigate testis-specific histone 2B (TSH2B) and its gene anomalies in infertile men.

DESIGN

Case-control study.

SETTING

Basic science laboratory.

PATIENT(S)

Fertile and infertile men.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

The histone and protamine status of sperm was studied by aniline blue and chromomycin A3 staining, respectively. Testis-specific histone 2B, total H2B, and phosphorylated TSH2B (pTSH2B) were estimated by Western blot analysis. The frequency of genetic polymorphisms and rare variants in H2BC1 was studied by Sanger sequencing. Phosphosites on TSH2B in sperm were identified by reverse-phase high-performance liquid chromatography purification of TSH2B followed by mass spectrometric analysis.

RESULT(S)

Aniline blue and chromomycin A3 staining revealed significantly higher histone retention and low protamine in sperm of infertile men. Sperm TSH2B and total H2B levels were significantly lower in oligozoospermic and oligoasthenozoospermic men (in both groups). The TSH2B levels were comparable in asthenozoospermic men; however, the pTSH2B level was significantly low. The H2BC1 gene sequencing identified 6 variants, of which 2 are rare variants (rs368672899 and rs544942090) and 4 (rs4711096, rs4712959, rs4712960 and rs4712961) are single nucleotide polymorphisms. Minor allele frequency of 5'-untranslated region variant rs4711096 was significantly lower in infertile men (OR = 0.65). The rare nonsynonymous variant, rs368672899, p.Ser5Pro was seen in 1 oligoasthenoteratozoospermic individual. Interestingly, mass spectrometric analysis identified a site on TSH2B to bear a phosphate group in the sperm of fertile men.

CONCLUSION(S)

Our study reveals a defect in the replacement of somatic histones with testis-specific variants in infertile men. Chromatin compaction positively correlates with sperm motility, which is suggestive of its utility in diagnostic semen analysis of infertile individuals. Our observations with TSH2B and its cognate gene in sperm of infertile men indicate an essential role for TSH2B in meiosis and its phosphorylation in sperm motility, respectively.

Epigenetic Risks of Medically Assisted Reproduction

Since the birth of Louise Joy Brown, the first baby conceived via in vitro fertilization, more than 9 million children have been born worldwide using assisted reproductive technologies (ART). In vivo fertilization takes place in the maternal oviduct, where the unique physiological conditions guarantee the healthy development of the embryo. During early embryogenesis, a major wave of epigenetic reprogramming takes place that is crucial for the correct development of the embryo. Epigenetic reprogramming is susceptible to environmental changes and non-physiological conditions such as those applied during in vitro culture, including shift in pH and temperature, oxygen tension, controlled ovarian stimulation, intracytoplasmic sperm injection, as well as preimplantation embryo manipulations for genetic testing. In the last decade, concerns were raised of a possible link between ART and increased incidence of imprinting disorders, as well as epigenetic alterations in the germ cells of infertile parents that are transmitted to the offspring following ART. The aim of this review was to present evidence from the literature regarding epigenetic errors linked to assisted reproduction treatments and their consequences on the conceived children. Furthermore, we provide an overview of disease risk associated with epigenetic or imprinting alterations in children born via ART.

Contemporary Use of ICSI and Epigenetic Risks to Future Generations

Since the birth of Louise Brown in 1978 via IVF, reproductive specialists have acquired enormous knowledge and refined several procedures, which are nowadays applied in assisted reproductive technology (ART). One of the most critical steps in this practice is the fertilization process. In the early days of IVF, a remarkable concern was the unpleasant outcomes of failed fertilization, overtaken by introducing intracytoplasmic sperm injection (ICSI), delineating a real breakthrough in modern ART. ICSI became standard practice and was soon used as the most common method to fertilize oocytes. It has been used for severe male factor infertility and non-male factors, such as unexplained infertility or advanced maternal age, without robust scientific evidence. However, applying ICSI blindly is not free of potential detrimental consequences since novel studies report possible health consequences to offspring. DNA methylation and epigenetic alterations in sperm cells of infertile men might help explain some of the adverse effects reported in ICSI studies on reproductive health in future generations. Collected data concerning the health of ICSI children over the past thirty years seems to support the notion that there might be an increased risk of epigenetic disorders, congenital malformations, chromosomal alterations, and subfertility in babies born following ICSI compared to naturally conceived children. However, it is still to be elucidated to what level these data are associated with the cause of infertility or the ICSI technique. This review provides an overview of epigenetic mechanisms and possible imprinting alterations following the use of ART, in particular ICSI. It also highlights the sperm contribution to embryo epigenetic regulation and the risks of in vitro culture conditions on epigenetic dysregulation. Lastly, it summarizes the literature concerning the possible epigenetic disorders in children born after ART.

Female-induced selective modification of sperm protein SUMOylation-potential mechanistic insights into the non-random fertilization in humans

In many species, mate choice continues after the mating via female‐ or egg‐derived biochemical factors that induce selective changes in sperm pre‐fertilization physiology and behaviour. Recent studies have indicated that gamete‐mediated mate choice likely occurs also in humans, but the mechanistic basis of the process has remained virtually unexplored. Here, we investigated whether female‐induced modifications in sperm protein SUMOylation (post‐translational modification of the proteome) could serve as a novel mechanism for gamete‐mediated mate choice in humans. We treated the sperm of ten males with the oocyte‐surrounding bioactive liquid (follicular fluid) of five females and investigated motility, viability and global protein SUMOylation status of the sperm in all (n = 50) of these male–female combinations (full‐factorial design). All the measured sperm traits were affected by male–female combinations, and sperm protein SUMOylation status was also negatively associated with sperm motility. Furthermore, our results indicate that female‐induced sperm protein SUMOylation is selective, potentially allowing females to increase sperm motility in some males, whereas decreasing it in the others. Consequently, our findings suggest that follicular fluid may non‐randomly modify the structure and function of sperm proteome and in this way facilitate gamete‐mediated mate choice in humans and possibly many other species. However, due to the relatively low number of female subjects and their potential infertility problems, our results should be replicated with larger subset of fully fertile women.

Underestimated Aspects in Male Infertility: Epigenetics is A New Approach in Men with Obesity or Diabetes: A Review

Infertility is a complex multifactorial problem that affects about 7% of men and 15% of couples worldwide. Many molecular mechanisms involved in male infertility. Destructive effects of infertility on the next generations are not well understood. Approximately 60-75% of male infertility cases have idiopathic causes, and there is a need for additional investigations other than routine examinations. Molecular factors that surround DNA, which are mitotically stable and independently regulate genome activity of DNA sequences, are known as epigenetics. The known epigenetic mechanisms are DNA methylation, histone modifications and non-coding RNAs. Prevalence of metabolic diseases has been increased dramatically because of changes in lifestyle and the current levels of inactivity. Metabolic disorders, such<br />as obesity and diabetes, are prevalent reasons for male infertility; despite the association between metabolic diseases and male infertility, few studies have been conducted on the effects of epigenetic alterations associated with these diseases and sperm abnormalities. Diabetes can affect the reproductive system and testicular function at multiple levels;<br />however, there are very few molecular and epigenetic studies related to sperm from males with diabetes. On the other hand, obesity has similar conditions, while male obesity is linked to notable alterations in the sperm molecular architecture affecting both function and embryo quality. Therefore, in this review article, we presented new and developed technologies to study different patterns of epigenetic changes, and explained the exact mechanisms of epigenetic changes linked to metabolic diseases and their relationship with male infertility.

Dynamics of hyperacetylated histone H4 (H4Kac) during spermatogenesis in four decapod crustaceans

During spermatogenesis, the transition from histone to protamine is highly conserved in most invertebrates and vertebrates. Thus far, a large and growing body of literature has demonstrated that histones and histone modifications still exist in the sperm nucleus of decapod crustaceans. H4Kac is believed to play an important role in the process of sperm chromatin condensation. However, the dynamics of hyperacetylated histone H4 (H4Kac) during spermatogenesis in decapoda are still unknown. In this paper, the distribution of H4Kac in four decapod crustaceans (Eriocheir sinensis, Charybdis japonica, Procambarus clarkii, and Macrobrachium nipponense) were investigated via immunofluorescence. Our results indicated that H4Kac was visible in the mature sperm nucleus of E. sinensis, C. japonica, and M. nipponense. Unlike the other three species, H4Kac was translocated from the nuclei to cytoplasm in mid-spermatids of P. clarkii. Eventually, H4Kac were not present in mature spermatozoa of P. clarkii. Importantly, we observed for the first time that H4Kac was distributed outside the nucleus, which reminds us that H4Kac may participate in the formation of acrosome structure in decapod crustaceans and may be a prerequisite for proper chromatin decondensation.

A novel posttranslational modification of histone, H3 S-sulfhydration, is down-regulated in asthenozoospermic sperm

Oxidative stress is one of the major causes leading to male infertility including asthenozoospermia. Hydrogen sulfide (H₂S) has been widely recognized to be a potent antioxidant whose role is partially implemented by protein S-sulfhydration. However, protein S-sulfhydration has not been reported in germ cells. Therefore, we investigated whether asthenozoospermia could be associated with sperm protein S-sulfhydration. S-sulfhydrated proteins in human sperm were enriched via biotin-switch assay and analyzed using LC-MS/MS spectrometry. Two hundred forty-four S-sulfhydrated proteins were identified. Importantly, we validated that sperm histones H3.1 and H3.3 were the S-sulfhydrated proteins. Their S-sulfhydrated amino acid residue was Cysteine111. Abundances of S-sulfhydrated H3 (sH3) and S-sulfhydrated H3.3 (sH3.3) were significantly down-regulated in asthenozoospermic sperm, compared with the fertile controls, and were significantly correlated with progressive motility. Retinoic acid (RA) up-regulated level of sH3.3 in primary round spermatids and the C18-4 cells (a mouse spermatogonial stem cell line). Overexpression of the mutant H3.3 (Cysteine111 was replaced with serine) affected expression of 759 genes and raised growth rate of C18-4 cells. For the first time, S-sulfhydration H3 and H3.3 were demonstrated in the present study. Our results highlight that aberrant S-sulfhydration of H3 is a new pathophysiological basis in male infertility.

PRSS50 is a testis protease responsible for proper sperm tail formation and function

Multiple morphological abnormalities of the sperm flagella (MMAF) are a major cause of asthenoteratozoospermia. We have identified protease serine 50 (PRSS50) as having a crucial role in sperm development, because Prss50-null mice presented with impaired fertility and sperm tail abnormalities. PRSS50 could also be involved in centrosome function because these mice showed a threefold increase in acephalic sperm (head-tail junction defect), sperm with multiple heads (spermatid division defect) and sperm with multiple tails, including novel two conjoined sperm (complete or partial parts of several flagellum on the same plasma membrane). Our data support that, in the testis, as in tumorigenesis, PRSS50 activates NFκB target genes, such as the centromere protein leucine-rich repeats and WD repeat domain-containing protein 1 (LRWD1), which is required for heterochromatin maintenance. Prss50-null testes have increased IκκB, and reduced LRWD1 and histone expression. Low levels of de-repressed histone markers, such as H3K9me3, in the Prss50-null mouse testis may cause increases in post-meiosis proteins, such as AKAP4, affecting sperm formation. We provide important insights into the complex mechanisms of sperm development, the importance of testis proteases in fertility and a novel mechanism for MMAF.

Insights and clinical potential of proteomics in understanding spermatogenesis

Introduction: With the worldwide decline on male fertility potential, the importance of the insight of the spermatogenic process has been increasing. In recent years, proteomic methodologies have been applied to seminal fluid of infertile men to search for infertility potential biomarkers. However, to understand the spermatogenic event and to search for treatment to spermatogenic impairment, comparative analysis of testicular proteomics is considered a powerful methodology.Areas covered: Herein, we present a critical overview of the studies addressing proteomic alterations in the development of spermatogenesis during puberty, as well as during the different phases of the spermatogenic event. The comparative studies of the proteomic testicular profile of men with and without spermatogenic impairment are also discussed and key proteins and pathways involved highlighted.Expert opinion: The usage of whole human testicular tissue with its heterogeneous cellular composition makes proteome data interpretation particularly challenging. This may be minimized by controlled experiments involving the collection of testicular tissue and sperm from the same individuals, integrated in a clinically characterized cohort of healthy and infertile men. The analysis of specific subcellular proteomes can add more information to the proteomic puzzle, opening new treatment possibilities for infertile/subfertile men.

Genetic testing for men with infertility: techniques and indications

Genetic testing is an integral component in the workup of male infertility as genetic conditions may be responsible for up to 15% of all cases. Currently, three genetic tests are commonly performed and recommended by major urologic associations: karyotype analysis (KA), Y-chromosome microdeletion testing, and CFTR mutation testing. Despite widespread adoption of these tests, an etiology for infertility remains elusive in up to 80% of cases. Recent work has identified intriguing new targets for genetic testing which may soon see clinical relevance. This review will discuss the indications and techniques for currently offered genetic tests and briefly explore ongoing research directions within this field.

Lack of trusted diagnostic tools for undetermined male infertility

Semen analysis is the cornerstone of evaluating male infertility, but it is imperfect and insufficient to diagnose male infertility. As a result, about 20% of infertile males have undetermined infertility, a term encompassing male infertility with an unknown underlying cause. Undetermined male infertility includes two categories: (i) idiopathic male infertility-infertile males with abnormal semen analyses with an unknown cause for that abnormality and (ii) unexplained male infertility-males with "normal" semen analyses who are unable to impregnate due to unknown causes. The treatment of males with undetermined infertility is limited due to a lack of understanding the frequency of general sperm defects (e.g., number, motility, shape, viability). Furthermore, there is a lack of trusted, quantitative, and predictive diagnostic tests that look inside the sperm to quantify defects such as DNA damage, RNA abnormalities, centriole dysfunction, or reactive oxygen species to discover the underlying cause. To better treat undetermined male infertility, further research is needed on the frequency of sperm defects and reliable diagnostic tools that assess intracellular sperm components must be developed. The purpose of this review is to uniquely create a paradigm of thought regarding categories of male infertility based on intracellular and extracellular features of semen and sperm, explore the prevalence of the various categories of male factor infertility, call attention to the lack of standardization and universal application of advanced sperm testing techniques beyond semen analysis, and clarify the limitations of standard semen analysis. We also call attention to the variability in definitions and consider the benefits towards undetermined male infertility if these gaps in research are filled.

The Role of Exosomal Epigenetic Modifiers in Cell Communication and Fertility of Dairy Cows

Abnormal uterine function affects conception rate and embryo development, thereby leading to poor fertility and reproduction failure. Exosomes are a nanosized subclass of extracellular vesicles (EV) that have important functions as intercellular communicators. They contain and carry transferable bioactive substances including micro RNA (miRNA) for target cells. Elements of the cargo can provide epigenetic modifications of the recipient cells and may have crucial roles in mechanisms of reproduction. The dairy industry accounts for a substantial portion of the economy of many agricultural countries. Exosomes can enhance the expression of inflammatory mediators in the endometrium, which contribute to various inflammatory diseases in transition dairy cows. This results in reduced fertility which leads to reduced milk production and increased cow maintenance costs. Thus, gaining a clear knowledge of exosomal epigenetic modifiers is critical to improving the breeding success and profitability of dairy farms. This review provides a brief overview of how exosomal miRNA contributes to inflammatory diseases and hence to poor fertility, particularly in dairy cows.

Recent advances in clinical diagnosis and treatment of male factor infertility

Infertility is a significant global health issue affecting around 8-12% of couples worldwide with male factor infertility accounting for a substantial proportion of these cases. Despite significant advances within the past few decades, an etiology for male factor infertility cannot be identified in up to 80% of patients and thus, this continues to be an area of active study. This review aims to provide an update on recent advances in the field of male infertility including semen analysis and at-home semen testing, genetics, DNA fragmentation, surgical approaches, and the rise of telemedicine in the era of COVID19.

Role of genetics and epigenetics in male infertility

Male infertility is a complex condition with a strong genetic and epigenetic background. This review discusses the importance of genetic and epigenetic factors in the pathophysiology of male infertility. The interplay between thousands of genes, the epigenetic control of gene expression, and environmental and lifestyle factors, which influence genetic and epigenetic variants, determines the resulting male infertility phenotype. Currently, karyotyping, Y-chromosome microdeletion screening and CFTR gene mutation tests are routinely performed to investigate a possible genetic aetiology in patients with azoospermia and severe oligozoospermia. However, current testing is limited in its ability to identify a variety of genetic and epigenetic conditions that might be implicated in both idiopathic and unexplained infertility. Several epimutations of imprinting genes and developmental genes have been postulated to be candidate markers for male infertility. As such, development of novel diagnostic panels is essential to change the current landscape with regard to prevention, diagnosis and management. Understanding the underlying genetic mechanisms related to the pathophysiology of male infertility, and the impact of environmental exposures and lifestyle factors on gene expression might aid clinicians in developing individualised treatment strategies.

Male Infertility and the Future of In Vitro Fertilization

The male contribution to infertility has traditionally been overlooked, or at best oversimplified. In recent years efforts have been made to optimize diagnostic and therapeutic techniques to maximize fertility outcomes. A renewed focus on the male partner has resulted in an increased understanding of both genetic and epigenetic changes within the male germline. Furthermore, single-nucleotide polymorphisms, copy-number variants, DNA damage, sperm cryopreservation, obesity, and paternal age have recently been recognized as important factors that play a role in male fertility. Developing a deeper knowledge of these issues could potentially lead to improved success with assisted reproductive technology.

Histone Post-Translational Modifications and CircRNAs in Mouse and Human Spermatozoa: Potential Epigenetic Marks to Assess Human Sperm Quality

Spermatozoa (SPZ) are motile cells, characterized by a cargo of epigenetic information including histone post-translational modifications (histone PTMs) and non-coding RNAs. Specific histone PTMs are present in developing germ cells, with a key role in spermatogenic events such as self-renewal and commitment of spermatogonia (SPG), meiotic recombination, nuclear condensation in spermatids (SPT). Nuclear condensation is related to chromatin remodeling events and requires a massive histone-to-protamine exchange. After this event a small percentage of chromatin is condensed by histones and SPZ contain nucleoprotamines and a small fraction of nucleohistone chromatin carrying a landascape of histone PTMs. Circular RNAs (circRNAs), a new class of non-coding RNAs, characterized by a nonlinear back-spliced junction, able to play as microRNA (miRNA) sponges, protein scaffolds and translation templates, have been recently characterized in both human and mouse SPZ. Since their abundance in eukaryote tissues, it is challenging to deepen their biological function, especially in the field of reproduction. Here we review the critical role of histone PTMs in male germ cells and the profile of circRNAs in mouse and human SPZ. Furthermore, we discuss their suggested role as novel epigenetic biomarkers to assess sperm quality and improve artificial insemination procedure.

CircRNA Role and circRNA-Dependent Network (ceRNET) in Asthenozoospermia

The role of circRNA in reproduction is under investigation. CircRNAs are expressed in human testis, spermatozoa (SPZ), and seminal plasma. Their involvement in embryo development has also been suggested. Asthenozoospermia, a common cause of male infertility, is characterized by reduced or absent sperm motility in fresh ejaculate. While abnormal mitochondrial function, altered sperm tail, and genomic causes have been deeply investigated, the epigenetic signature of asthenozoospermic derived SPZ still remains unexplored. CircRNAs may take part in the repertoire of differentially expressed molecules in infertile men. Considering this background, we carried out a circRNA microarray, identifying a total of 9,138 transcripts, 22% of them novel based and 83.5% with an exonic structure. Using KEGG analysis, we evaluated the circRNA contribution in pathways related to mitochondrial function and sperm motility. In order to discriminate circRNAs with a differential expression in SPZ with differential morphological parameters, we separated sperm cells by Percoll gradient and analyzed their differential circRNA payload. A bioinformatic approach was then utilized to build a circRNA/miRNA/mRNA network. With the aim to demonstrate a dynamic contribution of circRNAs to the sperm epigenetic signature, we verified their modulation as a consequence of an oral amino acid supplementation, efficacious in improving SPZ motility.

Post-translational modifications of seminal proteins and their importance in male fertility potential

Introduction: The seminal proteome has been shown to directly influence the male fertile potential. Post-translational modifications (PTMs) are significant changes that play a role in the biological regulation of proteins. Sperm cells are transcriptionally and translationally inactive and these modifications are essential to control protein function.Areas covered: Here we reviewed seven PTMs which importance for male reproductive function investigated in the past decade, namely S-nitrosylation and tyrosine nitration (both occurring by the action of NO), glycosylation, ubiquitination, acetylation, methylation, and SUMOylation. Since they were previously identified in human semen, we focus on their role in sperm function, as well as in physiological and pathophysiological processes which could contribute to the fertility potential. The following keywords were applied: 'post-translational modification', 'sperm', 'semen', 'seminal plasma', 'male infertility', 'nitrosylation', 'nitration', 'histone methylation', 'SUMOylation', 'ubiquitination', 'ubiquitilation', 'glycosylation', and 'acetylation'.Expert opinion: Most biological processes orchestrated by proteins require PTMs for their activation or inhibition. Most of them are dynamic and occur in mature sperm, modulating protein function, thus exerting a significant role in sperm function and fertility. Finally, the study of PTMs should be also addressed in pathophysiological processes, as different clinical conditions are known to alter the proteome.

Untargeted histone profiling during naive conversion uncovers conserved modification markers between mouse and human

Recent progress has enabled the conversion of primed human embryonic stem cells (hESCs) to the naive state of pluripotency, resembling the well-characterized naive mouse ESCs (mESCs). However, a thorough histone epigenetic characterization of this conversion process is currently lacking, while its likeness to the mouse model has not been clearly established. Here, we profile the histone epigenome of hESCs during conversion in a time-resolved experimental design, using an untargeted mass spectrometry-based approach. In total, 23 histone post-translational modifications (hPTMs) changed significantly over time. H3K27Me3 was the most prominently increasing marker hPTM in naive hESCs. This is in line with previous reports in mouse, prompting us to compare all the shared hPTM fold changes between mouse and human, revealing a set of conserved hPTM markers for the naive state. Principally, we present the first roadmap of the changing human histone epigenome during the conversion of hESCs from the primed to the naive state. This further revealed similarities with mouse, which hint at a conserved mammalian epigenetic signature of the ground state of pluripotency.