Oxidative stress and cryoresistance of sturgeon sperm: A review

Currently, the majority of sturgeons are relict fishes of high economic value yet endangered with extinction. Cryopreservation of sperm has great potential in fish farming and conservation, but the problem of low cryoresistance of sturgeon sperm has not yet been solved. The goal of this work was to review current literature data on the causes of low tolerance of sturgeon sperm to cryodamage. The influence of cryopreservation on the parameters of physiology and metabolism of sturgeon sperm (morphology and fine ultrastructure, mobility and fertilization ability, integrity of the plasma membrane, protein, lipid and metabolite profiles, antioxidant status, DNA damage), as well as on biomarkers of oxidative stress (lipids peroxidation levels and carbonyl derivatives of proteins) is discussed. Since the development of oxidative stress is an important mechanism of sperm cryodamage induction, the review presents the literature on the role of oxygen-derived species in damage of sturgeon reproductive cells caused by cryopreservation. Particular attention is paid to the system of antioxidant protection of sturgeon seminal plasma and spermatozoa, represented by antioxidant enzymes and low molecular weight antioxidants capable of utilizing various reactive forms of oxygen and nitrogen. The review discusses the results of lipidomic and proteomic studies of sturgeon sperm, which made it possible to obtain new data on the lipid composition of cell membranes, to detect proteins involved in the protection of sturgeon spermatozoa from oxidative damage during cryopreservation. This review presents the use of «omics» technology to elucidate the mechanism of cryodamage in sturgeon sperm. Additionally, the review summarizes information on the unique anatomical, morphological, biochemical, and physiological features of sturgeon sperm, which may be associated with low cryoresistance of sturgeon, in order to establish prospects for further research on improving the methods of the conservation of sperm of these threatened species.

The effect of sperm DNA fragmentation on ICSI outcomes depending on oocyte quality

BACKGROUND

Sperm deoxyribonucleic acid (DNA) fragmentation is commonly encountered in spermatozoa, and the oocyte assumes responsibility for repairing sperm DNA fragmentation during the oocyte-embryo transition.

OBJECTIVES

This study aimed to investigate whether the effect of sperm DNA fragmentation on intracytoplasmic sperm injection outcomes depends on the incidence of oocyte dimorphisms.

MATERIALS AND METHODS

For the present cohort, 2942 fertilized oocytes from 525 patients submitted to intracytoplasmic sperm injection cycles were assessed. The present study was conducted in a private in vitro fertilization center affiliated to a university from June 2016 to July 2019. Semen samples were divided into the following two groups depending on the sperm DNA fragmentation index: a low fragmentation index group (<30% sperm DNA fragmentation, n = 1468) and a high fragmentation index group (≥30% sperm DNA fragmentation, n = 486). In addition, mature oocytes were examined before sperm injection, and intracytoplasmic and extracytoplasmic defects were recorded. The effect of the sperm DNA fragmentation index on laboratory and clinical intracytoplasmic sperm injection outcomes (depending on the presence of oocyte defects) was evaluated.

RESULTS

Significant increases in the rates of fertilization, high-quality embryo, implantation, and pregnancy were noted for cycles with <30% sperm DNA fragmentation than cycles with ≥30% sperm DNA fragmentation (regardless of the presence of oocyte dimorphisms). The presence of dimorphisms significantly impacted laboratory and clinical outcomes. The lowest fertilization and high-quality embryo rates were observed when a high sperm DNA fragmentation index was associated with the presence of dark cytoplasm, vacuoles, resistant membrane, and non-resistant membrane. The lowest implantation and pregnancy rates were observed when a high sperm DNA fragmentation index was associated with the presence of vacuoles, defective perivitelline space, and fragmented polar body. The effect of sperm DNA fragmentation on miscarriage rates was significantly influenced by the presence of centrally located cytoplasmic granulation, a defective perivitelline space and non-resistant membrane.

CONCLUSION

A high sperm DNA fragmentation index increases the likelihood of miscarriage in intracytoplasmic sperm injection cycles, an effect that may potentially be magnified by the presence of oocyte dysmorphisms.

Checkpoint Kinase 1 Is a Key Signal Transducer of DNA Damage in the Early Mammalian Cleavage Embryo

After fertilization, remodeling of the oocyte and sperm genome is essential for the successful initiation of mitotic activity in the fertilized oocyte and subsequent proliferative activity of the early embryo. Despite the fact that the molecular mechanisms of cell cycle control in early mammalian embryos are in principle comparable to those in somatic cells, there are differences resulting from the specific nature of the gene totipotency of the blastomeres of early cleavage embryos. In this review, we focus on the Chk1 kinase as a key transduction factor in monitoring the integrity of DNA molecules during early embryogenesis.

Conservation Biology and Reproduction in a Time of Developmental Plasticity

The objective of this review is to ask whether, and how, principles in conservation biology may need to be revisited in light of new knowledge about the power of epigenetics to alter developmental pathways. Importantly, conservation breeding programmes, used widely by zoological parks and aquariums, may appear in some cases to reduce fitness by decreasing animals' abilities to cope when confronted with the 'wild side' of their natural habitats. Would less comfortable captive conditions lead to the selection of individuals that, despite being adapted to life in a captive environment, be better able to thrive if relocated to a more natural environment? While threatened populations may benefit from advanced reproductive technologies, these may actually induce undesirable epigenetic changes. Thus, there may be inherent risks to the health and welfare of offspring (as is suspected in humans). Advanced breeding technologies, especially those that aim to regenerate the rarest species using stem cell reprogramming and artificial gametes, may also lead to unwanted epigenetic modifications. Current knowledge is still incomplete, and therefore ethical decisions about novel breeding methods remain controversial and difficult to resolve.

CopyCatchers are versatile active genetic elements that detect and quantify inter-homolog somatic gene conversion

CRISPR-based active genetic elements, or gene-drives, copied via homology-directed repair (HDR) in the germline, are transmitted to progeny at super-Mendelian frequencies. Active genetic elements also can generate widespread somatic mutations, but the genetic basis for such phenotypes remains uncertain. It is generally assumed that such somatic mutations are generated by non-homologous end-joining (NHEJ), the predominant double stranded break repair pathway active in somatic cells. Here, we develop CopyCatcher systems in Drosophila to detect and quantify somatic gene conversion (SGC) events. CopyCatchers inserted into two independent genetic loci reveal unexpectedly high rates of SGC in the Drosophila eye and thoracic epidermis. Focused RNAi-based genetic screens identify several unanticipated loci altering SGC efficiency, one of which (c-MYC), when downregulated, promotes SGC mediated by both plasmid and homologous chromosome-templates in human HEK293T cells. Collectively, these studies suggest that CopyCatchers can serve as effective discovery platforms to inform potential gene therapy strategies.

Correlation between the DNA fragmentation index (DFI) and sperm morphology of infertile patients

Purpose

To evaluate the correlation between the DNA Fragmentation Index (DFI) and sperm morphology in patients undergoing ICSI, as a predictive parameter in reproductive outcomes.

Methods

A retrospective study was conducted on 125 infertile patients enrolled in a fertility clinic. Seminal characteristics were measured following the WHO guidelines (2010) for the examination of the seminal fluid. After collecting motile sperm population by pellet swim up, DFI was calculated and simultaneously associated with sperm morphology using in situ TUNEL assay and an image analyzer software in at least 250 spermatozoa for each patient.

Results

All subjects were divided into two groups according to a cutoff established, by choice, of the sperm DFI (15%): group A (< 15%) consisting of 65 patients and group B (≥ 15%) of 60 patients. Data were analyzed using non-parametric statistical methods. The results demonstrate that there is no statistical difference between the two groups in seminal characteristics. The collective data show a high significant correlation, suggesting that spermatozoa with abnormal morphology are the best candidates to contain DNA damage (p < 0.001). Also, when group A is compared with group B, an increased percentage of morphologically normal spermatozoa with fragmented DNA was observed in patients, with DFI values ≥ 15% (p < 0.001).

Conclusion

These results are aimed at providing an exact value of DFI in morphologically normal spermatozoa, which will be helpful to the embryologist in evaluating the risk of transferring, during the ICSI procedure, a spermatozoon whit normal morphology but fragmented DNA.

DNA damage and repair in the female germline: contributions to ART

BACKGROUND

DNA integrity and stability are critical determinants of cell viability. This is especially true in the female germline, wherein DNA integrity underpins successful conception, embryonic development, pregnancy and the production of healthy offspring. However, DNA is not inert; rather, it is subject to assault from various environment factors resulting in chemical modification and/or strand breakage. If structural alterations result and are left unrepaired, they have the potential to cause mutations and propagate disease. In this regard, reduced genetic integrity of the female germline ranks among the leading causes of subfertility in humans. With an estimated 10% of couples in developed countries taking recourse to ART to achieve pregnancy, the need for ongoing research into the capacity of the oocyte to detect DNA damage and thereafter initiate cell cycle arrest, apoptosis or DNA repair is increasingly more pressing.

OBJECTIVE AND RATIONALE

This review documents our current knowledge of the quality control mechanisms utilised by the female germline to prevent and remediate DNA damage during their development from primordial follicles through to the formation of preimplantation embryos.

SEARCH METHODS

The PubMed database was searched using the keywords: primordial follicle, primary follicle, secondary follicle, tertiary follicle, germinal vesical, MI, MII oocyte, zygote, preimplantation embryo, DNA repair, double-strand break and DNA damage. These keywords were combined with other phrases relevant to the topic. Literature was restricted to peer-reviewed original articles in the English language (published 1979-2018) and references within these articles were also searched.

OUTCOMES

In this review, we explore the quality control mechanisms utilised by the female germline to prevent, detect and remediate DNA damage. We follow the trajectory of development from the primordial follicle stage through to the preimplantation embryo, highlighting findings likely to have important implications for fertility management, age-related subfertility and premature ovarian failure. In addition, we survey the latest discoveries regarding DNA repair within the metaphase II (MII) oocyte and implicate maternal stores of endogenous DNA repair proteins and mRNA transcripts as a primary means by which they defend their genomic integrity. The collective evidence reviewed herein demonstrates that the MII oocyte can engage in the activation of major DNA damage repair pathway(s), therefore encouraging a reappraisal of the long-held paradigm that oocytes are largely refractory to DNA repair upon reaching this late stage of their development. It is also demonstrated that the zygote can exploit a number of protective strategies to mitigate the risk and/or effect the repair, of DNA damage sustained to either parental germline; affirming that DNA protection is largely a maternally driven trait but that some aspects of repair may rely on a collaborative effort between the male and female germlines.

WIDER IMPLICATIONS

The present review highlights the vulnerability of the oocyte to DNA damage and presents a number of opportunities for research to bolster the stringency of the oocyte's endogenous defences, with implications extending to improved diagnostics and novel therapeutic applications to alleviate the burden of infertility.

Cryoprotectants synergy improve zebrafish sperm cryopreservation and offspring skeletogenesis

The synergy obtained by the combination of cryoprotectants is a successful strategy that can be beneficial on the optimization of zebrafish sperm cryopreservation. Recently, a protocol was established for this species using an electric ultrafreezer (-150 °C) performing cooling rate (-66 °C/min) and storage within one step. The ultimate objective of sperm cryopreservation is to generate healthy offspring. Therefore, the objective of this study was to select the most adequate cryoprotectant combination, for the previously established protocol, that generate high quality offspring with normal skeletogenesis. Among the permeating cryoprotectant concentrations studied 12.5% and 15% of N,N-dimethylformamide (DMF) yielded high post-thaw sperm quality and hatching rates. For these two concentrations, the presence of bovine serum albumin (10 mg/mL), egg yolk (10%), glycine (30 mM) and bicine (50 mM) was evaluated for post-thaw sperm motility, viability, in vitro fertilization success and offspring skeletal development (30 days post fertilization). Higher concentration of permeating cryoprotectant (15%) decreased the incidence of deformed arches and severe skeletal malformations, which suggests higher capacity to protect the cell against cold stress and DNA damage. Extender containing 15% DMF with Ctrl, Bicine and egg yolk were the non-permeating cryoprotectants with higher post-thaw quality. The use of these compounds results in a reduction in vertebral fusions, compressions and severity of skeletal malformations in the offspring. Therefore, these extender compositions are beneficial for the quality of zebrafish offspring sired by cryopreserved sperm with -66 °C/min freezing rate. To the best of our knowledge, this is the first report on skeletal development of the offspring sired by cryopreserved sperm performed with different freezing media compositions in zebrafish.

Distribution of DNA damage in the human sperm nucleus: implications of the architecture of the sperm head

The sperm nucleus is prone to sustain DNA damage before and after ejaculation. Distribution of the damage is not homogeneous, and the factors determining differential sensitivity among nuclear regions have not yet been characterized. Human sperm chromatin contains three structural domains, two of which are considered the most susceptible to DNA damage: the histone bound domain, harboring developmental related genes, and the domain associated with nuclear matrix proteins. Using a quantitative polymerase chain reaction (qPCR) approach, we analyzed the number of lesions in genes homeobox A3 (HOXA3), homeobox B5 (HOXB5), sex-determining region Y (SRY)-box 2 (SOX2), β-GLOBIN, rDNA 18S, and rDNA 28S in human sperm after ultraviolet irradiation (400 μW cm⁻², 10 min), H₂O₂ treatment (250 mmol l⁻¹, 20 min), and cryopreservation, which showed differential susceptibility to genetic damage. Differential vulnerability is dependent on the genotoxic agent and independent of the sperm nuclear proteins to which the chromatin is bound and of accessibility to the transcription machinery. Immunodetection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) showed that the highest level of oxidation was observed after H₂O₂ treatment. The distribution of oxidative lesions also differed depending on the genotoxic agent. 8-OHdG did not colocalize either with histone 3 (H3) or with type IIα + β topoisomerase (TOPO IIα + β) after H₂O₂ treatment but matched perfectly with peroxiredoxin 6 (PRDX6), which is involved in H₂O₂ metabolism. Our study reveals that the characteristics of the sperm head domains are responsible for access of the genotoxicants and cause differential degree of damage to nuclear areas, whereas chromatin packaging has a very limited relevance. The histone-enriched genes analyzed cannot be used as biomarkers of oxidative DNA damage.

Double-stranded sperm DNA damage is a cause of delay in embryo development and can impair implantation rates

OBJECTIVE

To analyze the effect of single- and double-stranded sperm DNA fragmentation (ssSDF and dsSDF) on human embryo kinetics monitored under a time-lapse system.

DESIGN

Observational, double blind, prospective cohort study.

SETTING

University spin-off and private center.

PATIENT(S)

One hundred ninety-six embryos from 43 infertile couples were included prospectively.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

SsSDF and dsSDF were analyzed in the same semen sample used for intracytoplasmic sperm injection. Embryo kinetics was then monitored using time-lapse technology, and the timing of each embryo division was obtained.

RESULT(S)

When comparing embryos obtained from semen samples with low dsSDF and high dsSDF, splitting data using a statistically significant delay in high dsSDF was observed in second polar body extrusion, T4, T8, morula, and starting blastocyst and embryo implantation rates were impaired. Embryo kinetics and implantation rates are not significantly affected when high values of ssSDF are present. Different patterns of delay in embryo kinetics were observed for these different types of DNA damage: dsSDF caused a delay along all stages of embryo development; however, its major effect was observed at the second polar body extrusion and morula stages, coinciding with embryo DNA damage checkpoint activation as described before; ssSDF had its major effect at the pronucleus stage, but embryo kinetics was then restored at all following stages. The results show that dsSDF could be the main type of DNA damage that affects embryo development in intracytoplasmic sperm injection cycles, probably due to motility-based sperm selection in this assisted reproduction procedure.

CONCLUSION(S)

Double-stranded sperm DNA damage caused a delay in embryo development and impaired implantation, while single-stranded DNA damage did not significantly affect embryo kinetics and implantation.

Maternal temperature exposure impairs emotional and cognitive responses and triggers dysregulation of neurodevelopment genes in fish

Fish are sensitive to temperature, but the intergenerational consequences of maternal exposure to high temperature on offspring behavioural plasticity and underlying mechanisms are unknown. Here we show that a thermal maternal stress induces impaired emotional and cognitive responses in offspring rainbow trout (Oncorhynchus mykiss). Thermal stress in mothers triggered the inhibition of locomotor fear-related responses upon exposure to a novel environment and decreased spatial learning abilities in progeny. Impaired behavioural phenotypes were associated with the dysregulation of several genes known to play major roles in neurodevelopment, including auts2 (autism susceptibility candidate 2), a key gene for neurodevelopment, more specifically neuronal migration and neurite extension, and critical for the acquisition of neurocognitive function. In addition, our analysis revealed the dysregulation of another neurodevelopment gene (dpysl5) as well as genes associated with human cognitive disorders (arv1, plp2). We observed major differences in maternal mRNA abundance in the eggs following maternal exposure to high temperature indicating that some of the observed intergenerational effects are mediated by maternally-inherited mRNAs accumulated in the egg. Together, our observations shed new light on the intergenerational determinism of fish behaviour and associated underlying mechanisms. They also stress the importance of maternal history on fish behavioural plasticity.

High sperm DNA fragmentation delays human embryo kinetics when oocytes from young and healthy donors are microinjected

BACKGROUND

Time-lapse monitoring (TLM) technology has been implemented in the clinical setting for the culture and selection of human embryos. Many studies have assessed the association between sperm DNA fragmentation (sDNAf) and clinical outcomes after ART, but little is known about the influence of sDNA on embryo morphokinetics.

OBJECTIVES

The objective of this retrospective study, which includes 971 embryos from 135 consecutive ICSI cycles (56 cases with own oocytes, 79 with oocytes from young and healthy donors), was to assess if sDNAf has an impact on embryo morphokinetics.

MATERIALS AND METHODS

Samples used to perform ICSI were analyzed by the flow cytometry TUNEL assay, and embryo development was assessed through an EmbyoScope^® system. The association between sDNAf and the timings of cell cleavage was analyzed by categorizing the first variable into quartiles: ≤6.50%; 6.51-10.70%; 10.71-20.15%; >20.15%.

RESULTS

In cases where sDNAf was above 20.15% (the upper quartile), embryos derived from donated oocytes (n = 644) showed significantly slower divisions. Such association was not observed in embryos obtained from the patients' own oocytes (n = 327). The embryo cleavage pattern (either normal, direct from 1 to 3 blastomeres, direct from 1 to 4 blastomeres, incomplete, reversed or asynchronous) was independent of the sDNAf level. Blastocyst arrival rate was 63.0% and the rate of good quality embryos (transferred and frozen embryos divided by the number of zygotes) was 45.49%. Neither parameter was related to the levels of sDNAf.

DISCUSSION

According to our results, the association between high sDNAf and donated oocytes led to delayed cell division. To our knowledge, this is the first study suggesting that sDNAf can delay human embryo cleavage timings when oocytes from donors are inseminated.

CONCLUSIONS

This finding may indicate that, in the presence of increased DNA damage, time is needed before the first embryonic cell division for the activation of the optimal DNA repairing machinery in higher quality oocytes.

Effects of freezing and activation on membrane quality and DNA damage in Xenopus tropicalis and Xenopus laevis spermatozoa

There is growing concern over the effect of sperm cryopreservation on DNA integrity and the subsequent development of offspring generated from this cryopreserved material. In the present study, membrane integrity and DNA stability of Xenopus laevis and Xenopus tropicalis spermatozoa were evaluated in response to cryopreservation with or without activation, a process that happens upon exposure to water to spermatozoa of some aquatic species. A dye exclusion assay revealed that sperm plasma membrane integrity in both species decreased after freezing, more so for X. laevis than X. tropicalis spermatozoa. The sperm chromatin dispersion (SCD) test showed that for both X. tropicalis and X. laevis, activated frozen spermatozoa produced the highest levels of DNA fragmentation compared with all fresh samples and frozen non-activated samples (P<0.05). Understanding the nature of DNA and membrane damage that occurs in cryopreserved spermatozoa from Xenopus species represents the first step in exploiting these powerful model organisms to understand the developmental consequences of fertilising with cryopreservation-damaged spermatozoa.

Tolerance to paternal genotoxic damage promotes survival during embryo development in zebrafish (Danio rerio)

Spermatozoa carry DNA damage that must be repaired by the oocyte machinery upon fertilization. Different strategies could be adopted by different vertebrates to face the paternal genotoxic damage. Mammals have strong sperm selection mechanisms and activate a zygotic DNA damage response (DDR) (including cell cycle arrest, DNA repair and alternative apoptosis) in order to guarantee the genomic conformity of the reduced progeny. However, external fertilizers, with different reproductive strategies, seem to proceed distinctively. Previous results from our group showed a downregulation of apoptotic activity in trout embryos with a defective DNA repairing ability, suggesting that mechanisms of tolerance to damaged DNA could be activated in fish to maintain cell survival and to progress with development. In this work, zebrafish embryos were obtained from control or UV-irradiated sperm (carrying more than 10% of fragmented DNA but still preserving fertilization ability). DNA repair (γH2AX and 53BP1 foci), apoptotic activity, expression of genes related to DDR and malformation rates were analyzed throughout development. Results showed in the progeny from damaged sperm, an enhanced repairing activity at the mid-blastula transition stage that returned to its basal level at later stages, rendering at hatching a very high rate of multimalformed larvae. The study of transcriptional and post-translational activity of tp53 (ZDF-GENE-990415-270) revealed the activation of an intense DDR in those progenies. However, the downstream pro-apoptotic factor noxa (ZDF-GENE-070119-3) showed a significant downregulation, whereas the anti-apoptotic gene bcl2 (ZDF-GENE-051015-1) was upregulated, triggering a repressive apoptotic scenario in spite of a clear genomic instability. This repression can be explained by the observed upregulation of p53 isoform Δ113p53, which is known to enhance bcl2 transcription. Our results showed that tp53 is involved in DNA damage tolerance (DDT) pathways, allowing the embryo survival regardless of the paternal DNA damage. DDT could be an evolutionary mechanism in fish: tolerance to unrepaired sperm DNA could introduce new mutations, some of them potentially advantageous to face a changing environment.

Summary: In fish embryos, genomic instability generated by fertilization with DNA damaged sperm activates mechanisms of DNA damage tolerance, which seems to be mediated by Δ113p53 expression, promoting survival.

Maternal SENP7 programs meiosis architecture and embryo survival in mouse

Understanding the mechanisms underlying abnormal egg production and pregnancy loss is significant for human fertility. SENP7, a SUMO poly-chain editing enzyme, has been regarded as a mitotic regulator of heterochromatin integrity and DNA repair. Herein, we report the roles of SENP7 in mammalian reproductive scenario. Mouse oocytes deficient in SENP7 experienced meiotic arrest at prophase I and metaphase I stages, causing a substantial decrease of mature eggs. Hyperaceylation and hypomethylation of histone H3 and up-regulation of Cdc14B/C accompanied by down-regulation of CyclinB1 and CyclinB2 were further recognized as contributors to defective M-phase entry and spindle assembly in oocytes. The spindle assembly checkpoint activated by defective spindle morphogenesis, which was also caused by mislocalization and ubiquitylation-mediated proteasomal degradation of γ-tubulin, blocked oocytes at meiosis I stage. SENP7-depleted embryos exhibited severely defective maternal-zygotic transition and progressive degeneration, resulting in nearly no blastocyst production. The disrupted epigenetic landscape on histone H3 restricted Rad51C loading onto DNA lesions due to elevated HP1α euchromatic deposition, and reduced DNA 5hmC challenged the permissive status for zygotic DNA repair, which induce embryo death. Our study pinpoints SENP7 as a novel determinant in epigenetic programming and major pathways that govern oocyte and embryo development programs in mammals.

Impact of sperm DNA damage and oocyte-repairing capacity on trout development

Zygotic repair of paternal DNA is essential during embryo development. In spite of the interest devoted to sperm DNA damage, its combined effect with defect-repairing oocytes has not been analyzed. Modification of the breeding season is a common practice in aquaculture. This practice reduces developmental success and could affect the both factors: sperm DNA integrity and oocyte repair capacity. To evaluate the maternal role, we analyzed the progeny outcome after fertilizing in-season trout oocytes with untreated and with UV-irradiated sperm. We also analyzed the offspring obtained out of season with untreated sperm. The analysis of the number of lesions in 4 sperm nuclear genes revealed an increase of 1.22–11.18 lesions/10 kb in out-of-season sperm, similar to that obtained after sperm UV irradiation (400 µW/cm25 min). Gene expression showed in out-of-season oocytes the overexpression of repair genes (ogg1, ung, lig3, rad1) and downregulation of tp53, indicating an enhanced repairing activity and reduced capacity to arrest development upon damage. The analysis of the progeny in out-of-season embryos revealed a similar profile tolerant to DNA damage, leading to a much lower apoptotic activity at organogenesis, lower hatching rates and increased rate of malformations. The effects were milder in descendants from in-season-irradiated sperm, showing an enhanced repairing activity at epibolia. Results point out the importance of the repairing machinery provided by the oocyte and show how susceptible it is to environmental changes. Transcripts related to DNA damage signalization and repair could be used as markers of oocyte quality.