The protamines of the noble false widow spider Steatoda nobilis provide an example of liquid-liquid phase separation chromatin transitions during spermiogenesis.

While there is extensive information about sperm nuclear basic proteins (SNBP) in vertebrates, there is very little information about Arthropoda by comparison. This paper aims to contribute to filling this gap by analyzing these proteins in the sperm of the noble false widow spider Steatoda nobilis (Order Araneae, Family Theridiidae). To this end, we have developed a protein extraction method that allows the extraction of cysteine-containing protamines suitable for the preparation and analysis of SNBPs from samples where the amount of starting tissue material is limited. We carried out top-down mass spectrometry sequencing and molecular phylogenetic analyses to characterize the protamines of S. nobilis and other spiders. We also used electron microscopy to analyze the chromatin organization of the sperm, and we found it to exhibit liquid-liquid phase spinodal decomposition during the late stages of spermiogenesis. These studies further our knowledge of the distribution of SNBPs within the animal kingdom and provide additional support for a proposed evolutionary origin of many protamines from a histone H1 (H5) replication-independent precursor.

Running the gauntlet: challenges to genome integrity in spermiogenesis.

Species' continuity depends on gametogenesis to produce the only cell types that can transmit genetic information across generations. Spermiogenesis, which encompasses post-meiotic, haploid stages of male gametogenesis, is a process that leads to the formation of sperm cells well-known for their motility. Spermiogenesis faces three major challenges. First, after two rounds of meiotic divisions, the genome lacks repair templates (no sister chromatids, no homologous chromosomes), making it incredibly vulnerable to any genomic insults over an extended time (typically days-weeks). Second, the sperm genome becomes transcriptionally silent, making it difficult to respond to new perturbations as spermiogenesis progresses. Third, the histone-to-protamine transition, which is essential to package the sperm genome, counterintuitively involves DNA break formation. How spermiogenesis handles these challenges remains poorly understood. In this review, we discuss each challenge and their intersection with the biology of protamines. Finally, we discuss the implication of protamines in the process of evolution.

Protamines and the sperm nuclear basic proteins Pandora's Box of insects.

Insects are the largest group of animals when it comes to the number and diversity of species. Yet, with the exception of Drosophila, no information is currently available on the primary structure of their sperm nuclear basic proteins (SNBPs). This paper represents the first attempt in this regard and provides information about six species of Neoptera: Poecillimon thessalicus, Graptosaltria nigrofuscata, Apis mellifera, Nasonia vitripennis, Parachauliodes continentalis, and Tribolium castaneum. The SNBPs of these species were characterized by acetic acid urea gel electrophoresis (AU-PAGE) and high-performance liquid chromatography fractionated. Protein sequencing was obtained using a combination of mass spectrometry sequencing, Edman N-terminal degradation sequencing and genome mining. While the SNBPs of several of these species exhibit a canonical arginine-rich protamine nature, a few of them exhibit a protamine-like composition. They appear to be the products of extensive cleavage processing from a precursor protein which are sometimes further processed by other post-translational modifications that are likely involved in the chromatin transitions observed during spermiogenesis in these organisms.

Proteomic analysis of human sperm reveals changes in protamine 1 phosphorylation in men with infertility.

OBJECTIVE: To perform a comprehensive assessment of protamine (P) isoforms and modifications in human sperm with the aim of identifying how P modifications and isoforms are altered in men with reduced sperm motility and low sperm count. DESIGN: Cross-sectional. SETTING: Academic medical center. PATIENTS: A total of 18 men with prior reported pregnancy and normozoospermia (normal sperm), 14 men from couples with infertility and asthenozoospermia (reduced sperm motility), and 24 men from couples with infertility and oligoasthenoteratozoospermia (low sperm count and motility and abnormal sperm morphology). INTERVENTION(S): Not applicable. MAIN OUTCOME MEASURE(S): Proteomic assessment using both top-down and bottom-up liquid chromatography mass spectrometry (MS) analysis. RESULTS: A total of 13 posttranslational modifications were identified on P1 and P2 using bottom-up MS, including both phosphorylation and methylation. Top-down MS revealed an unmodified and phosphorylated isoform of P1 and the 3 major isoforms of P2, HP2, HP3, and HP4. Protamine 1 phosphorylation was overall higher in men with male factor infertility compared with those with normal semen analysis (40.5% vs. 32.6). There was no difference in P posttranslational modifications or isoforms of P2 in men with normal vs. abnormal fertility. CONCLUSION: Human protamines bear a number of posttranslational modifications, with alterations in P1 phosphorylation noted in the setting of male factor infertility.

Management of an unintentional enoxaparin overdose: A case report and literature review.

PURPOSE: The aim of this article is to describe a case in which protamine was used for a low-molecular-weight heparin (LMWH) overdose and present an up-to-date review of the literature on the management of LMWH overdose in adults. SUMMARY: An unintentional administration of enoxaparin 900 mg occurred in a 73-year-old man with coronavirus disease 2019-related pulmonary embolism. Management of the overdose included a protamine bolus followed by an infusion. Anti-factor Xa levels and activated partial thromboplastin time were monitored. Anti-factor Xa levels declined in a linear fashion irrespective of protamine administration. No bleeding or further thrombotic complications occurred in the patient. A review of the literature revealed that the optimal strategy to treat an LMWH overdose is unknown, with treatment of overdoses ranging from clinical observation to aggressive protamine dosing in reported cases. Although protamine effectively neutralizes unfractionated heparin, it is unable to completely reverse LMWH activity and has variable effects on laboratory measures of LMWH anticoagulant activity. CONCLUSION: The current case report provides additional data to previous literature suggesting that protamine may have a limited effect in decreasing anti-factor Xa levels in LMWH overdose. Continued reporting on the management of LMWH overdoses is warranted to clarify the optimal treatment strategy.

What's fishy about protamine? Clinical use, adverse reactions, and potential alternatives.

Protamine, a highly basic protein isolated from salmon sperm, is the only clinically available agent to reverse the anticoagulation of unfractionated heparin. Following intravenous administration, protamine binds to heparin in a nonspecific electrostatic interaction to reverse its anticoagulant effects. In clinical use, protamine is routinely administered to reverse high-dose heparin anticoagulation in cardiovascular procedures, including cardiac surgery with cardiopulmonary bypass. Despite the lack of supportive evidence regarding protamine's effectiveness to reverse low-molecular-weight heparin, it is recommended in guidelines with low-quality evidence. Different dosing strategies have been reported for reversing heparin in cardiac surgical patients based on empiric dosing, pharmacokinetics, or point-of-care measurements of heparin levels. Protamine administration is associated with a spectrum of adverse reactions that range from vasodilation to life-threatening cardiopulmonary dysfunction and shock. The life-threatening responses appear to be hypersensitivity reactions due to immunoglobulin E and/or immunoglobulin G antibodies. However, protamine and heparin-protamine complexes can activate complement inflammatory pathways and inhibit other coagulation factors. Although alternative agents for reversing heparin are not currently available for clinical use, additional research continues evaluating novel therapeutic approaches.

Expansion and loss of sperm nuclear basic protein genes in Drosophila correspond with genetic conflicts between sex chromosomes.

Many animal species employ sperm nuclear basic proteins (SNBPs) or protamines to package sperm genomes tightly. SNBPs vary across animal lineages and evolve rapidly in mammals. We used a phylogenomic approach to investigate SNBP diversification in Drosophila species. We found that most SNBP genes in Drosophila melanogaster evolve under positive selection except for genes essential for male fertility. Unexpectedly, evolutionarily young SNBP genes are more likely to be critical for fertility than ancient, conserved SNBP genes. For example, CG30056 is dispensable for male fertility despite being one of three SNBP genes universally retained in Drosophila species. We found 19 independent SNBP gene amplification events that occurred preferentially on sex chromosomes. Conversely, the montium group of Drosophila species lost otherwise-conserved SNBP genes, coincident with an X-Y chromosomal fusion. Furthermore, SNBP genes that became linked to sex chromosomes via chromosomal fusions were more likely to degenerate or relocate back to autosomes. We hypothesize that autosomal SNBP genes suppress meiotic drive, whereas sex-chromosomal SNBP expansions lead to meiotic drive. X-Y fusions in the montium group render autosomal SNBPs dispensable by making X-versus-Y meiotic drive obsolete or costly. Thus, genetic conflicts between sex chromosomes may drive SNBP rapid evolution during spermatogenesis in Drosophila species.

In sperm, DNA is packaged more tightly than in other cells thanks to small proteins called 'sperm nuclear basic proteins' (SNBPs), also called protamines in mammals. SNBPs are important for sperm to develop properly and correctly perform their role during fertilization. Although the evolution of SNBPs has been studied in mammals, these proteins have not been as thoroughly examined in invertebrates. Chang et al. took advantage of the availability of high-quality sequences for the genomes of 78 species of Drosophila flies to investigate the evolution of the genes that code for SNBPs in these flies. The results showed that, just like in mammals, in Drosophila the protein sequences of SNBPs evolve rapidly. However, unlike mammals, Chang et al. also found that Drosophila species frequently gained and lost genes coding for SNBPs. Interestingly, the 'older' genes (genes that appeared earlier in evolution) that code for SNBPs are not essential for reproduction in the fruit fly Drosophila melanogaster. This is an unexpected finding because older genes usually have essential roles for survival and reproduction, which require them to be passed on to the next generation and remain in the genome. In contrast, younger SNBP genes that had appeared more recently and were not shared between different species of Drosophila were often essential for fertility. These results, combined with other observations about where SNBP genes are located in the genome, led Chang et al. to hypothesize that SNBPs present in sex chromosomes act as 'meiotic drivers' while those on other chromosomes (known as autosomes) suppress meiotic drive. In other words, SNBP genes present in the sex chromosomes may be responsible for killing sister sperm cells that do not carry those genes, while SNBP genes that are not located on sex chromosomes may suppress this activity. This is of particular interest because it indicates that SNBPs are involved in genetic conflicts between the two sex chromosomes: sperm that carry SNBPs on the X chromosome may kill sperm with a Y chromosome, and vice versa. The results of Chang et al. shed light on the mysterious evolution of SNBPs in Drosophila flies. Although previous hypotheses regarding the rapid evolution of SNBPs evolution have focused on their role in genome packaging, this new analysis suggests that much of the evolutionary change is likely driven by genetic conflicts between sex chromosomes.

Insights into the sperm chromatin and implications for male infertility from a protein perspective.

Male germ cells undergo an extreme but fascinating process of chromatin remodeling that begins in the testis during the last phase of spermatogenesis and continues through epididymal sperm maturation. Most of the histones are replaced by small proteins named protamines, whose high basicity leads to a tight genomic compaction. This process is epigenetically regulated at many levels, not only by posttranslational modifications, but also by readers, writers, and erasers, in a context of a highly coordinated postmeiotic gene expression program. Protamines are key proteins for acquiring this highly specialized chromatin conformation, needed for sperm functionality. Interestingly, and contrary to what could be inferred from its very specific DNA-packaging function across protamine-containing species, human sperm chromatin contains a wide spectrum of protamine proteoforms, including truncated and posttranslationally modified proteoforms. The generation of protamine knock-out models revealed not only chromatin compaction defects, but also collateral sperm alterations contributing to infertile phenotypes, evidencing the importance of sperm chromatin protamination toward the generation of a new individual. The unique features of sperm chromatin have motivated its study, applying from conventional to the most ground-breaking techniques to disentangle its peculiarities and the cellular mechanisms governing its successful conferment, especially relevant from the protein point of view due to the important epigenetic role of sperm nuclear proteins. Gathering and contextualizing the most striking discoveries will provide a global understanding of the importance and complexity of achieving a proper chromatin compaction and exploring its implications on postfertilization events and beyond. This article is categorized under: Reproductive System Diseases > Genetics/Genomics/Epigenetics Reproductive System Diseases > Molecular and Cellular Physiology.

Molecular Alterations and Severe Abnormalities in Spermatozoa of Young Men Living in the "Valley of Sacco River" (Latium, Italy): A Preliminary Study.

The Valley of Sacco River (VSR) (Latium, Italy) is an area with large-scale industrial chemical production that has led over time to significant contamination of soil and groundwater with various industrial pollutants, such as organic pesticides, dioxins, organic solvents, heavy metals, and particularly, volatile organic compounds (VOCs). In the present study, we investigated the potential impact of VOCs on the spermatozoa of healthy young males living in the VSR, given the prevalent presence of several VOCs in the semen of these individuals. To accomplish this, spermiograms were conducted followed by molecular analyses to assess the content of sperm nuclear basic proteins (SNBPs) in addition to the protamine-histone ratio and DNA binding of these proteins. We found drastic alterations in the spermatozoa of these young males living in the VSR. Alterations were seen in sperm morphology, sperm motility, sperm count, and protamine/histone ratios, and included significant reductions in SNBP-DNA binding capacity. Our results provide preliminary indications of a possible correlation between the observed alterations and the presence of specific VOCs.

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.

BAF-L Modulates Histone-to-Protamine Transition during Spermiogenesis.

Maturing male germ cells undergo a unique developmental process in spermiogenesis that replaces nucleosomal histones with protamines, the process of which is critical for testicular development and male fertility. The progress of this exchange is regulated by complex mechanisms that are not well understood. Now, with mouse genetic models, we show that barrier-to-autointegration factor-like protein (BAF-L) plays an important role in spermiogenesis and spermatozoal function. BAF-L is a male germ cell marker, whose expression is highly associated with the maturation of male germ cells. The genetic deletion of BAF-L in mice impairs the progress of spermiogenesis and thus male fertility. This effect on male fertility is a consequence of the disturbed homeostasis of histones and protamines in maturing male germ cells, in which the interactions between BAF-L and histones/protamines are implicated. Finally, we show that reduced testicular expression of BAF-L represents a risk factor of human male infertility.

Using Deep Learning Algorithm: The Study of Sperm Head Vacuoles and Its Correlation with Protamine mRNA Ratio.

OBJECTIVE: It is necessary to evaluate fertility effective agents to predict assisted reproduction outcomes. This study was designed to examine sperm vacuole characteristics, and its association with sperm chromatin status and protamine-1 (PRM1) to protamine-2 (PRM2) ratio, to predict assisted pregnancy outcomes. MATERIALS AND METHODS: In this experimental study, ninety eight semen samples from infertile men were classified based on Vanderzwalmen's criteria as follows: grade I: no vacuoles; grade II: ≤2 small vacuoles; grade III: ≥1 large vacuole and grade IV: large vacuole with other abnormalities. The location, frequency and size of vacuoles were assessed using high magnification, a deep learning algorithm, and scanning electron microscopy (SEM). The chromatin integrity, condensation, viability and acrosome integrity, and protamination status were evaluated for vacuolated samples by toluidine blue (TB) staining, aniline blue, triple staining, and CMA3 staining, respectively. Also, Protamine-1 and protamine-2 genes expression was analysed by reverse transcription-quantitative polymerase chain reaction (PCR). The assisted reproduction outcomes were also followed for each cycle. RESULTS: The results show a significant correlation between the vacuole size (III and IV) and abnormal sperm chromatin condensation (P=0.03 and P=0.02, respectively), and also, protamine-deficient (P=0.04 and P=0.03, respectively). The percentage of reacting acrosomes was significantly higher in the grades III and IV spermatozoa in comparison with normal group. The vacuolated spermatozoa with grade IV showed a high protamine mRNA ratio (PRM-2 was underexpressed, P=0.01). In the IVF cycles, we observed a negative association between sperm head vacuole and fertilization rate (P=0.01). This negative association was also significantly observed in pregnancy and live birth rate in the groups with grade III and IV (P=0.04 and P=0.03, respectively). CONCLUSION: The results of our study highlight the importance sperm parameters such as sperm head vacuole characteristics, particularly those parameters with the potency of reflecting protamine-deficiency and in vitro fertilization/ intracytoplasmic sperm injection (IVF/ICSI) outcomes predicting.

Aerobic training mitigates the negative impact of diabetes on fertility.

Diabetes negatively affects the reproductive system. This present study investigated the effects of aerobic training on protamine 1 and 2 mRNA expression, sex hormones, antioxidant defence and sperm quality in diabetic rats. Thirty-six male Wistar rats were randomly allocated into three groups including diabetic training (DT) group, diabetic (D) group and control (C) group. Rats in DT were exercised 5 times per week for 8 weeks. Blood samples were collected for evaluation of sex hormones 48 h after the last training session. Also, the testes were removed and subjected to histological evaluation and semen analysis. Testicular mRNA expressions of protamines were determined by RT-qPCR. Protamines 1 and 2, and the ratio of protamine 1 to protamine 2 were significantly lower in DT and D groups compared with C group (p < 0.01). LH and testosterone levels were significantly lower in D group compared with DT and C group (p < 0.01). Malondialdehyde was significantly lower in DT and C groups compared with D group (p < 0.001). Sperm parameters were significantly lower in D group compared with C group (p < 0.01). Our findings suggest that aerobic training may mitigate the negative impact of diabetes on sex hormones, oxidative stress, protamine content and sperm parameters in male rats.

Sexual selection towards a protamine expression ratio optimum in two rodent groups?

Post-copulatory sexual selection is thought to influence the evolution of genes involved in reproduction. However, the detection of straightforward effects has been proven difficult due to the complexity and diversity of reproductive landscapes found in different taxa. Here, we compare the possible effect of relative testes mass as a sperm competition proxy on protamine genotype (protamine 1/protamine 2 ratio) and the link to sperm head phenotype in two rodent groups, mice, and voles. In mice, protamine expression ratios were found to increase from low values toward a 1:1 ratio in a positive association with testes mass, and relative sperm head area. In contrast, in voles, decreasing protamine expression ratios were found in species with larger testes but, surprisingly, they range from high values, again toward a 1:1 ratio, and showing a negative correlation with relative sperm head area. Altogether, we found differences in the way protamines seem to be selected and involved in adaptations of the sperm head in voles and mice. However, sexual selection driven by sperm competition seems to exhibit a common evolutionary pattern in both groups toward an equilibrium in the expression of the two protamines.

Interaction of heparin and protamine in presence of overdosage: in vitro study.

BACKGROUND: Heparin is used for anticoagulation during cardiopulmonary bypass. After weaning from bypass, protamine is administered to neutralize the effects of heparin and thus reestablish hemostasis. Rotational thrombelastometry has been shown to discriminate between heparin and other impairing effects on coagulation. We analyzed the interaction of heparin and protamine under different conditions of overdosage in an in-vitro trial. METHODS: Blood samples were taken from 17 healthy volunteers, separated, and spiked in vitro with heparin, protamine for heparin neutralization, an overdosage of protamine, and two dosages of re-heparinization to evaluate heparin effects under the condition of protamine overdosage. All samples were analyzed in a standard ROTEM rotational thromboelastometry device after intrinsic activation with and without addition of heparinase. Coagulation time, maximum clot firmness, and clot formation time were recorded. RESULTS: Heparin led to prolongation of coagulation and clot formation times in the test without heparinase. Adequate protamine addition normalized the test, and overdosage of protamine led to significant prolongation of both times. Addition of heparin in the presence of protamine overdosage normalized these parameters. CONCLUSION: We reconfirmed that the ROTEM device enables discrimination of the effects heparin and protamine on coagulation and detection of the coagulation-impairing effects of protamine overdosage. Furthermore, we were able to show a positive effect on coagulation times by heparin in the presence of protamine overdosage. Because this was an in-vitro study, these findings need to be confirmed in vivo, requiring further research.

Molecular Alterations in Spermatozoa of a Family Case Living in the Land of Fires. A First Look at Possible Transgenerational Effects of Pollutants.

In our previous work, we reported alterations in protamines/histones ratio, in DNA binding of these proteins and their involvement in DNA oxidative damage in 84% of the young men living in the Land of Fires. In the present work, we extended our findings, evaluating any alterations in spermatozoa of a family case, a father and son, living in this area, to also give a first look at the possibility of transgenerational inherited effects of environmental contaminants on the molecular alterations of sperm nuclear basic proteins (SNBP), DNA and semen parameters. In the father and son, we found a diverse excess of copper and chromium in the semen, different alterations in SNBP content and low DNA binding affinity of these proteins. In addition, DNA damage, in the presence of CuCl2 and H2O2, increased by adding both the father and son SNBP. Interestingly, son SNBP, unlike his father, showed an unstable DNA binding and were able to produce DNA damage even without external addition of CuCl2, in line with a lower seminal antioxidant activity than the father. The peculiarity of some characteristics of son semen could be a basis for possible future studies on transgenerational effects of pollutants on fertility.

Risk Factors Associated with Difficult Reversal of Heparin by Protamine Sulfate in Cardiopulmonary Bypass: An Ignored Issue.

BACKGROUND: The aim of this study was to evaluate risk factors associated with difficult heparin reversal by protamine after cardiopulmonary bypass. METHODS: Data from 120 consecutive patients who underwent open heart surgery from 2009 to 2017 were retrospectively reviewed. Patients were divided into 2 groups: (1) those in whom complete heparin reversal was achieved after a single infusion of protamine (group A, n=89); and (2) those who required more protamine for heparin reversal (group B, n=31). RESULTS: Female sex, prolonged bypass time (>200 min), long aortic cross-clamping time (>120 min), and a lowest rectal temperature <26°C were significant predictors of difficult heparin reversal. Larger amounts of fresh frozen plasma and platelet concentrate were transfused in group B than in group A. CONCLUSION: Surgeons' efforts to reduce operative time and avoid deep hypothermia may be helpful for increasing the likelihood of easy heparin reversal, especially in female patients.

The Interplay Between Replacement and Retention of Histones in the Sperm Genome.

The genome of eukaryotes is highly organized within the cell nucleus, this organization per se elicits gene regulation and favors other mechanisms like cell memory throughout histones and their post-translational modifications. In highly specialized cells, like sperm, the genome is mostly organized by protamines, yet a significant portion of it remains organized by histones. This protamine-histone-DNA organization, known as sperm epigenome, is established during spermiogenesis. Specific histones and their post-translational modifications are retained at specific genomic sites and during embryo development these sites recapitulate their histone profile that harbored in the sperm nucleus. It is known that histones are the conduit of epigenetic memory from cell to cell, hence histones in the sperm epigenome may have a role in transmitting epigenetic memory from the sperm to the embryo. However, the exact function and mechanism of histone retention remains elusive. During spermatogenesis, most of the histones that organize the genome are replaced by protamines and their retention at specific regions may be deeply intertwined with the eviction and replacement mechanism. In this review we will cover some relevant aspects of histone replacement that in turn may help us to contextualize histone retention. In the end, we focus on the architectonical protein CTCF that is, so far, the only factor that has been directly linked to the histone retention process.

Protamine-2 Deficiency Initiates a Reactive Oxygen Species (ROS)-Mediated Destruction Cascade during Epididymal Sperm Maturation in Mice.

Protamines are the safeguards of the paternal sperm genome. They replace most of the histones during spermiogenesis, resulting in DNA hypercondensation, thereby protecting its genome from environmental noxa. Impaired protamination has been linked to male infertility in mice and humans in many studies. Apart from impaired DNA integrity, protamine-deficient human and murine sperm show multiple secondary effects, including decreased motility and aberrant head morphology. In this study, we use a Protamine-2 (Prm2)-deficient mouse model in combination with label-free quantitative proteomics to decipher the underlying molecular processes of these effects. We show that loss of the sperm's antioxidant capacity, indicated by downregulation of key proteins like Superoxide dismutase type 1 (SOD1) and Peroxiredoxin 5 (PRDX5), ultimately initiates an oxidative stress-mediated destruction cascade during epididymal sperm maturation. This is confirmed by an increased level of 8-OHdG in epididymal sperm, a biomarker for oxidative stress-mediated DNA damage. Prm2-deficient testicular sperm are not affected and initiate the proper development of blastocyst stage preimplantation embryos in vitro upon intracytoplasmic sperm injection (ICSI) into oocytes. Our results provide new insight into the role of Prm2 and its downstream molecular effects on sperm function and present an important contribution to the investigation of new treatment regimens for infertile men with impaired protamination.

Discovery of the Involvement in DNA Oxidative Damage of Human Sperm Nuclear Basic Proteins of Healthy Young Men Living in Polluted Areas.

DNA oxidative damage is one of the main concerns being implicated in severe cell alterations, promoting different types of human disorders and diseases. For their characteristics, male gametes are the most sensitive cells to the accumulation of damaged DNA. We have recently reported the relevance of arginine residues in the Cu(II)-induced DNA breakage of sperm H1 histones. In this work, we have extended our previous findings investigating the involvement of human sperm nuclear basic proteins on DNA oxidative damage in healthy males presenting copper and chromium excess in their semen. We found in 84% of those males an altered protamines/histones ratio and a different DNA binding mode even for those presenting a canonical protamines/histones ratio. Furthermore, all the sperm nuclear basic proteins from these samples that resulted were involved in DNA oxidative damage, supporting the idea that these proteins could promote the Fenton reaction in DNA proximity by increasing the availability of these metals near the binding surface of DNA. In conclusion, our study reveals a new and unexpected behavior of human sperm nuclear basic proteins in oxidative DNA damage, providing new insights for understanding the mechanisms related to processes in which oxidative DNA damage is implicated.