Transgenerational epigenetic programming via sperm microRNA recapitulates effects of paternal stress

Astrocyte-derived exosomes regulate sperm miR-34c levels to mediate the transgenerational effects of paternal chronic social instability stress

The effects of chronically stressing male mice can be transmitted across generations by stress-specific changes in their sperm miRNA content, which induce stress-specific phenotypes in their offspring. However, how each stress paradigm alters the levels of distinct sets of sperm miRNAs is not known. We showed previously that exposure of male mice to chronic social instability (CSI) stress results in elevated anxiety and reduced sociability specifically in their female offspring across multiple generations because it reduces miR-34c levels in sperm of stressed males and their unstressed male offspring. Here, we describe evidence that astrocyte-derived exosomes (A-Exos) carrying miR-34c mediate how CSI stress has this transgenerational effect on sperm. We found that CSI stress decreases miR-34c carried by A-Exos in the prefrontal cortex and amygdala, as well as in the blood of males. Importantly, miR-34c A-Exos levels are also reduced in these tissues in their F1 male offspring, who despite not being exposed to stress, exhibit reduced sperm miR-34c levels and transmit the same stress-associated traits to their male and female offspring. Furthermore, restoring A-Exos miR-34c content in the blood of CSI-stressed males by intravenous injection of miR-34c-containing A-Exos restores miR-34c levels in their sperm. These findings reveal an unexpected role for A-Exos in maintaining sperm miR-34c levels by a process that when suppressed by CSI stress mediates this example of transgenerational epigenetic inheritance.

Melatonin influence on miRNA expression in sperm, hypothalamus, pre-frontal cortex and cerebellum of Wistar rats

Melatonin is a pineal hormone synthesized exclusively at night, in several organisms. Its action on sperm is of particular interest, since they transfer genetic and epigenetic information to the offspring, including microRNAs, configuring a mechanism of paternal epigenetic inheritance. MicroRNAs are known to participate in a wide variety of mechanisms in basically all cells and tissues, including the brain and the sperm cells, which are known, respectively, to present 70% of all identified microRNAs and to transfer these molecules to the embryo. MicroRNAs from sperm have been associated with modulation of embryonic development and inheritance of psychiatric symptoms, including autism. Given that microRNAs and melatonin are ubiquitous molecules with important roles in the organism, the aim of this study was to investigate the expression of specific microRNAs in sperm, brain and cerebellum of pinealectomized rats. For this study, Wistar rats had their pineal gland removed at 60 post-partum. Part of these rats received exogenous melatonin until the day of the euthanasia. The control group did not receive any treatment or manipulation. The sperm, hypothalamus, prefrontal cortex and cerebellum were collected for analysis of microRNA expression by RT-qPCR. The results suggest that melatonin absence caused by pinealectomy increases the expression of the target microRNAs in the sperm. Although the data suggest an alteration (increase or decrease depending on the region and microRNA) of expression levels of some microRNAs in the brain and cerebellum of pinealectomized rats, the differences were not statistically significant. This seems to be a consequence of the intragroup variation. Melatonin administration restored the levels of the target microRNAs in the sperm. Additional studies are needed to understand the impact of the alterations of microRNA expression to the pinealectomized rats as well as to their descendants.

Sperm-borne small non-coding RNAs: potential functions and mechanisms as epigenetic carriers

Over the past two decades, the study of sperm-borne small non-coding RNAs (sncRNAs) has garnered substantial growth. Once considered mere byproducts during germ cell maturation, these sncRNAs have now been recognized as crucial carriers of epigenetic information, playing a significant role in transmitting acquired traits from paternal to offspring, particularly under environmental influences. A growing body of evidence highlights the pivotal role of these sncRNAs in facilitating epigenetic inheritance across generations. However, the exact mechanisms through which these paternally supplied epigenetic carriers operate remain unclear and are under hot debate. This concise review presents the most extensive evidence to date on environmentally-responsive sperm-borne sncRNAs, encompassing brief summary of their origin, dynamics, compartmentalization, characteristics, as well as in-depth elaboration of their functional roles in epigenetic and transgenerational inheritance. Additionally, the review delves into the potential mechanisms by which sperm-delivered sncRNAs may acquire and transmit paternally acquired traits to offspring, modulating zygotic gene expression and influencing early embryonic development.

How do lifestyle and environmental factors influence the sperm epigenome? Effects on sperm fertilising ability, embryo development, and offspring health

Recent studies support the influence of paternal lifestyle and diet before conception on the health of the offspring via epigenetic inheritance through sperm DNA methylation, histone modification, and small non-coding RNA (sncRNA) expression and regulation. Smoking may induce DNA hypermethylation in genes related to anti-oxidation and insulin resistance. Paternal diet and obesity are associated with greater risks of metabolic dysfunction in offspring via epigenetic alterations in the sperm. Metabolic changes, such as high blood glucose levels and increased body weight, are commonly observed in the offspring of fathers subjected to chronic stress, in addition to an enhanced risk of depressive-like behaviour and increased sensitivity to stress in both the F0 and F1 generations. DNA methylation is correlated with alterations in sperm quality and the ability to fertilise oocytes, possibly via a differentially regulated MAKP81IP3 signalling pathway. Paternal exposure to toxic endocrine-disrupting chemicals (EDCs) is also linked to the transgenerational transmission of increased predisposition to disease, infertility, testicular disorders, obesity, and polycystic ovarian syndrome (PCOS) in females through epigenetic changes during gametogenesis. As the success of assisted reproductive technology (ART) is also affected by paternal diet, BMI, and alcohol consumption, its outcomes could be improved by modifying factors that are dependent on male lifestyle choices and environmental factors. This review discusses the importance of epigenetic signatures in sperm-including DNA methylation, histone retention, and sncRNA-for sperm functionality, early embryo development, and offspring health. We also discuss the mechanisms by which paternal lifestyle and environmental factors (obesity, smoking, EDCs, and stress) may impact the sperm epigenome.

Adaptive Significance of Non-coding RNAs: Insights from Cancer Biology

The molecular basis of adaptive evolution and cancer progression are both complex processes that share many striking similarities. The potential adaptive significance of environmentally-induced epigenetic changes is currently an area of great interest in both evolutionary and cancer biology. In the field of cancer biology intense effort has been focused on the contribution of stress-induced non-coding RNAs (ncRNAs) in the activation of epigenetic changes associated with elevated mutation rates and the acquisition of environmentally adaptive traits. Examples of this process are presented and combined with more recent findings demonstrating that stress-induced ncRNAs are transferable from somatic to germline cells leading to cross-generational inheritance of acquired adaptive traits. The fact that ncRNAs have been implicated in the transient adaptive response of various plants and animals to environmental stress is consistent with findings in cancer biology. Based on these collective observations, a general model as well as specific and testable hypotheses are proposed on how transient ncRNA-mediated adaptive responses may facilitate the transition to long-term biological adaptation in both cancer and evolution.

Depletion of the paternal gut microbiome alters sperm small RNAs and impacts offspring physiology and behavior in mice

The paternal environment prior to conception has been demonstrated to influence offspring physiology and behavior, with the sperm epigenome (including noncoding RNAs) proposed as a potential facilitator of non-genetic inheritance. Whilst the maternal gut microbiome has been established as an important influence on offspring development, the impact of the paternal gut microbiome on offspring development, health and behavior is largely unknown. Gut microbiota have major influences on immunity, and thus we hypothesized that they may be relevant to paternal immune activation (PIA) modulating epigenetic inheritance in mice. Therefore, male C57BL/6J mice (F0) were orally administered non-absorbable antibiotics via drinking water in order to substantially deplete their gut microbiome. Four weeks after administration of the antibiotics (gut microbiome depletion), F0 male mice were then mated with naïve female mice. The F1 offspring of the microbiome-depleted males had reduced body weight as well as altered gut morphology (shortened colon length). F1 females showed significant alterations in affective behaviors, including measures of anxiety and depressive-like behaviors, indicating altered development. Analysis of small noncoding RNAs in the sperm of F0 mice revealed that gut microbiome depletion is associated with differential expression of 8 different PIWI-interacting RNAs (piRNAs), each of which has the potential to modulate the expression of multiple downstream gene targets, and thus influence epigenetic inheritance and offspring development. This study demonstrates that the gut-germline axis influences sperm small RNA profiles and offspring physiology, with specific impacts on offspring affective and/or coping behaviors. These findings may have broader implications for other animal species with comparable gut microbiota, intergenerational epigenetics and developmental biology, including humans.

Perinatal Psychoneuroimmunology of Prenatal Stress and Its Effects on Fetal and Postnatal Brain Development

Prenatal stress (PS) impacts early behavioral, neuroimmune, and cognitive development. Pregnant rat models have been very valuable in examining the mechanisms of such fetal programming. A pregnant sheep model of maternal stress offers the unique advantages of chronic in utero monitoring and manipulation. This chapter presents the techniques used to model single and multigenerational stress exposures and their pleiotropic effects on the offspring.

Associations of preconception air pollution exposure with growth trajectory in young children: A prospective cohort study

Gestational air pollution exposure was associated with childhood obesity. However, little is known about the effect of air pollution exposure during the preconception period, a critical window when environmental exposures may affect body growth trajectory and increase obesity risk. We conducted a population-based prospective cohort study of preconception women and their newborn children followed until 2 years old from metropolitan Shanghai, China to investigate the impact of preconception air pollution on childhood weight and body mass index (BMI) growth trajectories. Exposures to PM2.5, PM10, and NO2 during 3 months before conception and each trimester of pregnancy were estimated using high-resolution spatiotemporal models matched at residential addresses. Children's weight and BMI were assessed postnatally every three months. Multivariate and longitudinal models with piecewise linear mixed effects were used to examine the relationship between preconception air pollution and child growth trajectories of weight, BMI, and standardized BMI (BMIZ). The study population comprised 26,714 women in the baseline enrolled in preconception clinics and 5,834 children reached 2 years included in the analysis with 34,398 longitudinal weight and height measurements. One interquartile range (IQR) increase in preconception PM2.5 (16.2 μg/m3) was associated with a 0.078 (95% confidence interval (CI): 0.002-0.154, p = 0.04) increase in attained BMIZ and 1 IQR increase of PM10 (21.1 μg/m3) were associated with an 0.093 (95% CI: 0.002-0.184, p = 0.04) kg/m2 increase in attained BMI, respectively, at the age of two years, after controlling for individual covariates and gestational air pollution exposure. Higher weight, BMI, and BMIZ growth rates during 6-24 months of life were also associated with higher preconception NO2 and PM exposure. Males and children born to mothers less than 35 years old or with overweight/obesity status were more affected by preconception air pollution exposure on weight growth. The 3-month preconception period was a critical time window for air pollution exposure.

The Impact of Parental Preconception Nutrition, Body Weight, and Exercise Habits on Offspring Health Outcomes: A Narrative Review

An increasing number of studies highlight the critical role of both maternal and paternal nutrition and body weight before conception in shaping offspring health. Traditionally, research has focused on maternal factors, particularly in utero exposures, as key determinants of chronic disease development. However, emerging evidence underscores the significant influence of paternal preconception health on offspring metabolic outcomes. While maternal health remains vital, with preconception nutrition playing a pivotal role in fetal development, paternal obesity and poor nutrition are linked to increased risks of metabolic disorders, including type 2 diabetes and cardiovascular disease in children. This narrative review aims to synthesize recent findings on the effects of both maternal and paternal preconception health, emphasizing the need for integrated early interventions. The literature search utilized PubMed, UNF One Search, and Google Scholar, focusing on RCTs; cohort, retrospective, and animal studies; and systematic reviews, excluding non-English and non-peer-reviewed articles. The findings of this review indicate that paternal effects are mediated by epigenetic changes in sperm, such as DNA methylation and non-coding RNA, which influence gene expression in offspring. Nutrient imbalances during preconception in both parents can lead to low birth weight and increased metabolic disease risk, while deficiencies in folic acid, iron, iodine, and vitamin D are linked to developmental disorders. Additionally, maternal obesity elevates the risk of chronic diseases in children. Future research should prioritize human studies to explore the influence of parental nutrition, body weight, and lifestyle on offspring health, ensuring findings are applicable across diverse populations. By addressing both maternal and paternal factors, healthcare providers can better reduce the prevalence of metabolic syndrome and its associated risks in future generations.

Transgenerational epigenetic self-memory of Dio3 dosage is associated with Meg3 methylation and altered growth trajectories and neonatal hormones

Intergenerational and transgenerational epigenetic effects resulting from conditions in previous generations can contribute to environmental adaptation as well as disease susceptibility. Previous studies in rodent and human models have shown that abnormal developmental exposure to thyroid hormone affects endocrine function and thyroid hormone sensitivity in later generations. Since the imprinted type 3 deiodinase gene (Dio3) regulates sensitivity to thyroid hormones, we hypothesize its epigenetic regulation is altered in descendants of thyroid hormone overexposed individuals. Using DIO3-deficient mice as a model of developmental thyrotoxicosis, we investigated Dio3 total and allelic expression and growth and endocrine phenotypes in descendants. We observed that male and female developmental overexposure to thyroid hormone altered total and allelic Dio3 expression in genetically intact descendants in a tissue-specific manner. This was associated with abnormal growth and neonatal levels of thyroid hormone and leptin. Descendant mice also exhibited molecular abnormalities in the Dlk1-Dio3 imprinted domain, including increased methylation in Meg3 and altered foetal brain expression of other genes of the Dlk1-Dio3 imprinted domain. These molecular abnormalities were also observed in the tissues and germ line of DIO3-deficient ancestors originally overexposed to thyroid hormone in utero. Our results provide a novel paradigm of epigenetic self-memory by which Dio3 gene dosage in a given individual, and its dependent developmental exposure to thyroid hormone, influences its own expression in future generations. This mechanism of epigenetic self-correction of Dio3 expression in each generation may be instrumental in descendants for their adaptive programming of developmental growth and adult endocrine function.

Transcriptomics of bovine sperm and oocytes

Traditionally, sperm and embryos were studied using microscopy to assess morphology and motility. However, OMICS technologies, especially transcriptomic analysis, are now being used to screen the molecular dynamics of fertility markers at cellular and molecular levels, with high sensitivity. Transcriptomics is the study of the transcriptome - RNA transcripts produced by the genome - using high-throughput methods to understand how the RNAs are expressed. In this review, we have discussed gene contributions to sperm structure and function and their role in fertilization and early embryo development. Further, we identified miRNAs shared by sperm, oocytes, and early embryos and their roles in fertilization and early embryo development.

Sperm RNA code in spermatogenesis and male infertility

Spermatozoa are traditionally thought to be transcriptionally inert, but recent studies have revealed the presence of sperm RNA, some of which is derived from the residues of spermatocyte transcription and some from epididymosomes. Paternal sperm RNA can be affected by external factors and further modified at the post-transcriptional level, for example N6-methyladenosine (m6A), thus shaping spermatogenesis and reproductive outcome. This review briefly introduces the origin of sperm RNA and, on this basis, summarizes the current knowledge on RNA modifications and their functional role in spermatogenesis and male infertility. The bottlenecks and knowledge gaps in the current research on RNA modification in male reproduction have also been indicated. Further investigations are needed to elucidate the functional consequences of these modifications, providing new therapeutic and preventive strategies for reproductive health and genetic inheritance.

Transmission of reduced levels of miR-34/449 from sperm to preimplantation embryos is a key step in the transgenerational epigenetic inheritance of the effects of paternal chronic social instability stress

The transgenerational effects of exposing male mice to chronic social instability (CSI) stress are associated with decreased sperm levels of multiple members of the miR-34/449 family that persist after their mating through preimplantation embryo (PIE) development. Here we demonstrate the importance of these miRNA changes by showing that restoring miR-34c levels in PIEs derived from CSI stressed males prevents elevated anxiety and defective sociability normally found specifically in their adult female offspring. It also restores, at least partially, levels of sperm miR-34/449 normally reduced in their male offspring who transmit these sex-specific traits to their offspring. Strikingly, these experiments also revealed that inducing miR-34c levels in PIEs enhances the expression of its own gene and that of miR-449 in these cells. The same induction of embryo miR-34/449 gene expression likely occurs after sperm-derived miR-34c is introduced into oocytes upon fertilization. Thus, suppression of this miRNA amplification system when sperm miR-34c levels are reduced in CSI stressed mice can explain how a comparable fold-suppression of miR-34/449 levels can be found in PIEs derived from them, despite sperm containing ~50-fold lower levels of these miRNAs than those already present in PIEs. We previously found that men exposed to early life trauma also display reduced sperm levels of miR-34/449. And here we show that miR-34c can also increase the expression of its own gene, and that of miR-449 in human embryonic stem cells, suggesting that human PIEs derived from men with low sperm miR-34/449 levels may also contain this potentially harmful defect.

Subchronic elevation in ambient temperature drives alterations to the sperm epigenome and accelerates early embryonic development in mice

Forecasted increases in the prevalence and severity of extreme weather events accompanying changes in climatic behavior pose potential risk to the reproductive capacity of humans and animals of ecological and agricultural significance. While several studies have revealed that heat stress induced by challenges such as testicular insulation can elicit a marked negative effect on the male reproductive system, and particularly the production of spermatozoa, less is known about the immediate impact on male reproductive function following subchronic whole-body exposure to elevated ambient temperature. To address this knowledge gap, we exposed unrestrained male mice to heat stress conditions that emulate a heat wave (daily cycle of 8 h at 35 °C followed by 16 h at 25 °C) for a period of 7 d. Neither the testes or epididymides of heat-exposed male mice exhibited evidence of gross histological change, and similarly, spermatozoa of exposed males retained their functionality and ability to support embryonic development. However, the embryos generated from heat-exposed spermatozoa experienced pronounced changes in gene expression linked to acceleration of early embryo development, aberrant blastocyst hatching, and increased fetal:placental weight ratio. Such changes were causally associated with an altered sperm small noncoding RNA (sncRNA) profile, such that these developmental phenotypes were recapitulated by microinjection of wild-type embryos sired by control spermatozoa with RNAs extracted from heat-exposed spermatozoa. Such data highlight that even relatively modest excursions in ambient temperature can affect male reproductive function and identify the sperm sncRNA profile as a particular point of vulnerability to this imposed environmental stress.

The paternal contribution to shaping the health of future generations

Paternal health and exposure to adverse environments in the period prior to conception have a profound impact on future generations. Adversities such as stress, diet, and toxicants influence offspring health. Emerging evidence indicates that epigenetic mechanisms including noncoding RNA, DNA methylation, and chromatin remodelling mediate these effects. Preclinical studies have contributed to advancing mechanistic understanding in the field; however, human research is limited and primarily observational. Here, we discuss the evidence linking paternal to offspring health and advocate for further research in this area, which may ultimately inform policy and healthcare guidelines to improve paternal preconception health and offspring outcomes.

Sperm miR-142-3p Reprogramming Mediates Paternal Pre-Pregnancy Caffeine Exposure-Induced Non-Alcoholic Steatohepatitis in Male Offspring Rats

Numerous studies have suggested a strong association between paternal adverse environmental exposure and increased disease susceptibility in offspring. However, the impact of paternal pre-pregnant caffeine exposure (PPCE) on offspring health remains unexplored. This study elucidates the sperm reprogramming mechanism and potential intervention targets for PPCE-induced non-alcoholic steatohepatitis (NASH) in offspring. Here, male rats are administrated caffeine (15-60 mg kg-1/d) by gavage for 8 weeks and then mated with females to produce offspring. This study finds that NASH with transgenerational inheritance occurred in PPCE adult offspring. Mechanistically, a reduction of miR-142-3p is implicated in the occurrence of NASH, characterized by hepatic lipid metabolism dysfunction and chronic inflammation through an increase in ACSL4. Conversely, overexpression of miR-142-3p mitigated these manifestations. The origin of reduced miR-142-3p levels is traced to hypermethylation in the miR-142-3p promoter region of parental sperm, induced by elevated corticosterone levels rather than by caffeine per se. Similar outcomes are confirmed in offspring conceived via in vitro fertilization using miR-142-3pKO sperm. Overall, this study provides the first evidence of transgenerational inheritance of NASH in PPCE offspring and identifies miR-142-3p as a potential therapeutic target for NASH induced by paternal environmental adversities.

A review of environmental epigenetics in aquatic invertebrates

Aquatic ecosystems face significant challenges due to increasing human-induced environmental stressors. Recent studies emphasize the role of epigenetic mechanisms in the stress responses and adaptations of organisms to those stressors. Epigenetics influences gene expression, enabling phenotypic plasticity and transgenerational effects. Therefore, understanding the epigenetic responses of aquatic invertebrates to environmental stressors is imperative for aquatic ecosystem research. In this study, we organize the mechanisms of epigenetics in aquatic invertebrates and explore their roles in the responses of aquatic invertebrates to environmental stressors. Furthermore, we discuss the inheritance of epigenetic changes and their influence across generations in aquatic invertebrates. A comprehensive understanding of epigenetic responses is crucial for long-term ecosystem management and conservation strategies in the face of irreversible climate change in aquatic environments. In this review, we synthesize existing knowledge about environmental epigenetics in aquatic invertebrates to provide insights and suggest directions for future research.

A narrative review of sperm selection technology for assisted reproduction techniques

Background and Objective

In-vitro fertilization (IVF) with intracytoplasmic sperm injection (ICSI) has become increasingly prevalent even in cases without significant male factor infertility; however, stagnant live-birth rates, both nationally and internationally, have driven more research into sperm selection. To date, nothing has replaced swim-up and density-gradient preparation methods and therefore we sought to review the state of the science.

Methods

A PubMed search was performed between years of 1989 and 2024 for English research articles reporting data on sperm selection technology in assisted reproductive technology.

Key Content and Findings

IVF with ICSI is increasingly prevalent even in men with normal semen parameters. Despite technologic advances and widespread use, reproductive outcomes with ICSI have been stagnant. This market for opportunity growth has allowed for sperm selection techniques to grow exponentially with heterogeneity in utilization and a paucity of positive reproductive outcomes. Swim-up and density-gradient centrifugation remain the most utilized sperm selection techniques. Various future technologies show promise including epigenetics, sperm biomarkers and a potential role of artificial intelligence; however, more research is needed.

Conclusions

Given unchanged IVF success rates, sperm selection technologies hold promise to improve reproductive outcomes beyond traditional ICSI. At present, no technique has shown superiority to swim up and density centrifugation.

Paternal preconception donepezil exposure enhances learning in offspring

BACKGROUND

Recent research has indicated that parental use of central nervous system-targeting medications during periconceptional periods may affect offspring across various developmental and behavioral domains. The present study sought to investigate the potential influence of paternal use of donepezil, a specific reversible central acetylcholinesterase inhibitor that activates the cholinergic system to promote cognition, on offspring.

RESULTS

In this study, male rats were bred after 21 days of oral donepezil administration at a dose of 4 mg/kg to generate F1 offspring. Both male and female F₁ offspring displayed enhanced performance in learning and short-term memory tests, including novel object recognition, Y maze, and operant learning. Transcriptomic analysis revealed notable alterations in genes associated with the extracellular matrix in the hippocampal tissue of the F1 generation. Integration with genes related to intelligence identified potential core genes that may be involved in the observed behavioral enhancements.

CONCLUSIONS

These findings indicate that prolonged paternal exposure to donepezil may enhance the learning and memory abilities of offspring, possibly by targeting nonneural, extracellular regions. Further research is required to fully elucidate any potential transgenerational effects.

Dysregulated miR-124 mediates impaired social memory behavior caused by paternal early social isolation

Early social isolation (SI) leads to various abnormalities in emotion and behavior during adulthood. However, the negative impact of SI on offspring remains unclear. This study has discovered that paternal early SI causes social memory deficits and anxiety-like behavior in F1 young adult mice, with alterations of myelin and synapses in the medial prefrontal cortex (mPFC). The 2-week SI in the F1 progeny exacerbates social memory impairment and hypomyelination in the mPFC. Furthermore, the down-regulation of miR-124, a key inhibitor of myelinogenesis, or over-expression of its target gene Nr4a1 in the mPFC of the F1 mice improves social interaction ability and enhances oligodendrocyte maturation and myelin formation. Mechanistically, elevated levels of miR-124 in the sperm of paternal SI mice are transmitted epigenetically to offspring, altering the expression levels of miR-124/Nr4a1/glucocorticoid receptors in mPFC oligodendrocytes. This, in turn, impedes the establishment of myelinogenesis-dependent social behavior. This study unveils a novel mechanism through which miR-124 mediates the intergenerational effects of early isolation stress, ultimately impairing the establishment of social behavior and neurodevelopment.

Epididymal acquired sperm microRNAs modify post-fertilization embryonic gene expression

Sperm small RNAs have emerged as important non-genetic contributors to embryogenesis and offspring health. A subset of sperm small RNAs is thought to be acquired during epididymal transit. However, the identity of the specific small RNAs transferred remains unclear. Here, we employ Cre/Lox genetics to generate germline- and epididymal-specific Dgcr8 knockout (KO) mice to investigate the dynamics of sperm microRNAs (miRNAs) and their functions post-fertilization. Testicular sperm from germline Dgcr8 KO mice has reduced levels of 116 miRNAs. Enthrallingly, following epididymal transit, the abundance of 72% of these miRNAs is restored. Conversely, sperm from epididymal Dgcr8 KO mice displayed reduced levels of 27 miRNAs. This loss of epididymal miRNAs in sperm was accompanied by transcriptomic changes in embryos fertilized by this sperm, which was rescued by microinjection of epididymal miRNAs. These findings ultimately demonstrate the acquisition of miRNAs from the soma by sperm during epididymal transit and their subsequent regulation of embryonic gene expression.

Dynamics and necessity of SIRT1 for maternal-zygotic transition

Dynamic changes in maternal‒zygotic transition (MZT) require complex regulation of zygote formation, maternal transcript decay, embryonic genome activation (EGA), and cell cycle progression. Although these changes are well described, some key regulatory factors are still elusive. Sirtuin-1 (SIRT1), an NAD+-dependent histone deacetylase, is a versatile driver of MZT via its epigenetic and nonepigenetic substrates. This study focused on the dynamics of SIRT1 in early embryos and its contribution to MZT. A conditional SIRT1-deficient knockout mouse model was used, accompanied by porcine and human embryos. Embryos across mammalian species showed the prominent localization of SIRT1 in the nucleus throughout early embryonic development. Accordingly, SIRT1 interacts with histone H4 on lysine K16 (H4K16) in both mouse and human blastocysts. While maternal SIRT1 is dispensable for MZT, at least one allele of embryonic Sirt1 is required for early embryonic development around the time of EGA. This role of SIRT1 is surprisingly mediated via a transcription-independent mode of action.

Astrocyte-Derived Exosomes Regulate Sperm miR-34c Levels to Mediate the Transgenerational Effects of Paternal Chronic Social Instability Stress

The effects of chronically stressing male mice can be transmitted across generations by stress-specific changes in their sperm miRNA content that induce stress-specific phenotypes in their offspring. But how each stress paradigm alters the levels of distinct sets of sperm miRNAs is not known. We showed previously that exposure of male mice to chronic social instability (CSI) stress results in elevated anxiety and reduced sociability specifically in their female offspring across multiple generations because it reduces miR-34c levels in sperm of stressed males and their unstressed male offspring. Here we describe evidence that a strocyte-derived exos omes ( A-Exos ) carrying miR-34c mediate how CSI stress has this transgenerational effect on sperm. We found that CSI stress decreases miR-34c carried by A-Exos in the prefrontal cortex and amygdala, as well as in the blood of males. Importantly, miR-34c A-Exos levels are also reduced in these tissues in their F1 male offspring, who despite not being exposed to stress exhibit reduced sperm miR-34c levels and transmit the same stress-associated traits to their male and female offspring. Furthermore, restoring A-Exos miR-34c content in the blood of CSI-stressed males by intravenous injection of miR-34c-containing A-Exos restores miR-34c levels in their sperm. These findings reveal an unexpected role for A-Exos in maintaining sperm miR-34c levels by a process that when suppressed by CSI stress mediates this example of transgenerational epigenetic inheritance.

Paternal hypercholesterolemia elicits sex-specific exacerbation of atherosclerosis in offspring

Emerging studies suggest that various parental exposures affect offspring cardiovascular health, yet the specific mechanisms, particularly the influence of paternal cardiovascular disease (CVD) risk factors on offspring cardiovascular health, remain elusive. The present study explores how paternal hypercholesterolemia affects offspring atherosclerosis development using the LDL receptor-deficient (LDLR-/-) mouse model. We found that paternal high-cholesterol diet feeding led to significantly increased atherosclerosis in F1 female, but not male, LDLR-/- offspring. Transcriptomic analysis highlighted that paternal hypercholesterolemia stimulated proatherogenic genes, including Ccn1 and Ccn2, in the intima of female offspring. Sperm small noncoding RNAs (sncRNAs), particularly transfer RNA-derived (tRNA-derived) small RNAs (tsRNAs) and rRNA-derived small RNAs (rsRNAs), contribute to the intergenerational transmission of paternally acquired metabolic phenotypes. Using a newly developed PANDORA-Seq method, we identified that high-cholesterol feeding elicited changes in sperm tsRNA/rsRNA profiles that were undetectable by traditional RNA-Seq, and these altered sperm sncRNAs were potentially key factors mediating paternal hypercholesterolemia-elicited atherogenesis in offspring. Interestingly, high-cholesterol feeding altered sncRNA biogenesis-related gene expression in the epididymis but not testis of LDLR-/- sires; this may have led to the modified sperm sncRNA landscape. Our results underscore the sex-specific intergenerational effect of paternal hypercholesterolemia on offspring cardiovascular health and contribute to the understanding of chronic disease etiology originating from parental exposures.

Experimentally altering microRNA levels in embryos alters adult phenotypes

We previously identified a unique genetic feature of Autism Spectrum Disorder (ASD) in human patients and established mouse models, a low to very low level of six microRNAs, miR-19a-3p, miR-361-5p, miR-3613-3p, miR-150-5p, miR-126-3p and miR-499a-5p. We attempted to interfere experimentally in mice with two of them, miR19a-3p and miR499a-5p by microinjecting into zygote pronuclei either the complementary sequence or an excess of the microRNA. Both resulted in low levels in the tissues and sperm of the targeted microRNAs and their pri and pre precursors. This method stably modify predetermined levels of miRNAs and identify miRNA alterations that cause changes in autistic behavior and predispose the individual to an inherited disease. Excess miRNA results in single-stranded miRNA variations in both free and DNA-bound RNA (R-loop) fractions in mouse models thus appearing to affect their own transcription. Analysis of miRNAs fractions in human patients blood samples confirm low level of six microRNAs also in R-loop fractions.

The transgenerational effects of maternal low-protein diet during lactation on offspring

Environmental factors such as diet and lifestyle can influence the health of both mothers and offspring. However, its transgenerational transmission and underlying mechanisms remain largely unknown. Here, using a maternal lactation-period low-protein diet (LPD) mouse model, we show that maternal LPD during lactation causes decreased survival and stunted growth, significantly reduces ovulation and litter size, and alters the gut microbiome in the female LPD-F1 offspring. The transcriptome of LPD-F1 metaphase II (MII) oocytes shows that differentially expressed genes are enriched in female pregnancy and multiple metabolic processes. Moreover, maternal LPD causes early stunted growth and impairs metabolic health, which is transmitted over two generations. The methylome alteration of LPD-F1 oocytes can be partly transmitted to the F2 oocytes. Together, our results reveal that LPD during lactation transgenerationally affects offspring health, probably via oocyte epigenetic changes.

DNA Methylation Profiling in Genetically Selected Clarias magur (Hamilton, 1822) Provides Insights into the Epigenetic Regulation of Growth and Development

DNA methylation is an epigenetic alteration that impacts gene expression without changing the DNA sequence affecting an organism's phenotype. This study utilized a reduced representation bisulfite sequencing (RRBS) approach to investigate the patterns of DNA methylation in genetically selected Clarias magur stocks. RRBS generated 249.22 million reads, with an average of 490,120 methylation sites detected in various parts of genes, including exons, introns, and intergenic regions. A total of 896 differentially methylated regions (DMRs) were identified; 356 and 540 were detected as hyper-methylated and hypo-methylated regions, respectively. The DMRs and their association with overlapping genes were explored using whole genome data of magur, which revealed 205 genes in exonic, 210 in intronic, and 480 in intergenic regions. The analysis identified the maximum number of genes enriched in biological processes such as RNA biosynthetic process, response to growth factors, nervous system development, neurogenesis, and anatomical structure morphogenesis. Differentially methylated genes (DMGs) such as myrip, mylk3, mafb, egr3, ndnf, meis2a, foxn3, bmp1a, plxna3, fgf6, sipa1l1, mcu, cnot8, trim55b, and myof were associated with growth and development. The selected DMGs were analyzed using real-time PCR, which showed altered mRNA expression levels. This work offers insights into the epigenetic mechanisms governing growth performance regulation in magur stocks. This work provides a valuable resource of epigenetic data that could be integrated into breeding programs to select high-performing individuals.

Mimicking bacterial infection in male mice changes sperm small RNA profiles and multigenerationally alters offspring behavior and physiology

Paternal pre-conceptual exposures, including stress, diet, substance abuse, parasite infection, and viral immune activation via Poly I:C, have been reported to influence the brains and behavior of offspring through sperm epigenetic changes. However, the effects of paternal (F0) pre-conceptual exposure to bacterial-induced immune activation on the behavior and physiology of F1 and F2 generations remain unexplored. We examined this using C57BL/6J mice. Eight-week-old males (F0) received a single intraperitoneal injection of the bacterial mimetic lipopolysaccharide (LPS: 5 mg/kg) or 0.9 % saline (vehicle control) before mating with naïve females at four weeks post-injection. Comprehensive behavioral assessments were conducted to investigate anxiety, social behaviors, depressive-like behaviors and cognition in both the F1 and F2 generations within the age range of 8 to 14 weeks. Results demonstrated that only female offspring of LPS-exposed fathers exhibited reduced anxiety levels in the light/dark box, large open field, and novelty-suppressed feeding test. These F1 female offspring also exhibited heightened sociability in the 3-chambered social interaction test and a reduced preference for saccharin in the saccharin preference test. Additionally, the F1 male offspring of LPS-challenged males demonstrated an increased total distance traveled in the light/dark box and a longer distance covered in the light zone. They also exhibited diminished preference for social novelty in the 3-chambered social interaction test and an elevated novel arm preference index in the Y-maze. In the F2 generation, male descendants of LPS-treated fathers showed reduced latency to feed in the novelty-suppressed feeding test. Additionally, the F2 generation of LPS-challenged fathers, but not the F1 generation, displayed enhanced immune response in both sexes after an acute LPS immune challenge (5 mg/kg). Analysis of sperm small noncoding RNA profiles from LPS-treated F0 mice revealed significant changes at 4 weeks after administration of LPS. These changes included three microRNAs, eight PIWI-interacting RNAs, and two transfer RNAs, exhibiting significant upregulation (mmu-miR-146a-5p, mmu-piR-27082 and mmu-piR-29102) or downregulation (mmu-miR-5110, mmu-miR-467e-3p, mmu-piR-22583, mmu-piR-23548, mmu-piR-36341, mmu-piR-50293, mmu-piR-16583, mmu-piR-36507, Mus_musculus_tRNA-Ile-AAT-2-1 and Mus_musculus_tRNA-Tyr-GTA-1-1). Additionally, we detected 52 upregulated small noncoding RNAs (including 9 miRNAs, 41 piRNAs, and 2 tRNAs) and 7 downregulated small noncoding RNAs (3 miRNAs, 3 piRNAs, and 1 tRNA) in the sperm of F1 offspring from LPS-treated males. These findings provide compelling evidence for the involvement of epigenetic mechanisms in the modulation of brain function and immunity, and associated behavioral and immunological traits, across generations, in response to bacterial infection.

Stress Biomarkers Transferred Into the Female Reproductive Tract by Seminal Plasma Are Associated with ICSI Outcomes

This study aimed to determine whether male stress is related to seminal stress biomarkers and pregnancy achievement in women exposed to their partner's seminal plasma (SP) in the intracytoplasmic sperm injection (ICSI) cycle. In this pilot prospective study, 20 couples undergoing ICSI, as well as 5 fertile sperm donors and 10 saliva donors, were investigated. Women were exposed to their partner's SP via unprotected sexual intercourse during the ICSI cycle and intravaginal application on the day of ovum pick-up (Day-OPU). Semen samples were collected from male partners by masturbation on the Day-OPU. Saliva and serum samples were collected prior to masturbation. Body fluids were frozen at - 80 °C until assayed. Biomarkers of activity of the sympathetic adrenomedullary axis (salivary alpha-amylase and adrenaline), sympathetic neural axis (noradrenaline and dopamine), hypothalamic-pituitary-adrenal (HPA) system (cortisol), and immune system (C-reactive protein and interleukin (IL)-18) were estimated to examine their association with SP composition and clinical pregnancy achievement. The clinical pregnancy rate was 45.0%. In the unsuccessful ICSI group, blunted levels of salivary and serum cortisol were found compared to the successful ICSI group and the fertile sperm donors. With regard to seminal markers, decreased cortisol level and elevated noradrenaline, noradrenaline/cortisol ratio, and lL-18 levels were strongly associated with ICSI failure (areas under the ROC curves were, 0.813, 0.848, 0.899, and 0.828, respectively). These findings confirm that stress response systems activity affects SP composition, which in turn is associated with ICSI outcomes in women exposed to their partner's SP during an ICSI cycle.

Future in the past: paternal reprogramming of offspring phenotype and the epigenetic mechanisms

That certain preconceptual paternal exposures reprogram the developmental phenotypic plasticity in future generation(s) has conceptualized the "paternal programming of offspring health" hypothesis. This transgenerational effect is transmitted primarily through sperm epigenetic mechanisms-DNA methylation, non-coding RNAs (ncRNAs) and associated RNA modifications, and histone modifications-and potentially through non-sperm-specific mechanisms-seminal plasma and circulating factors-that create 'imprinted' memory of ancestral information. The epigenetic landscape in sperm is highly responsive to environmental cues, due to, in part, the soma-to-germline communication mediated by epididymosomes. While human epidemiological studies and experimental animal studies have provided solid evidences in support of transgenerational epigenetic inheritance, how ancestral information is memorized as epigenetic codes for germline transmission is poorly understood. Particular elusive is what the downstream effector pathways that decode those epigenetic codes into persistent phenotypes. In this review, we discuss the paternal reprogramming of offspring phenotype and the possible underlying epigenetic mechanisms. Cracking these epigenetic mechanisms will lead to a better appreciation of "Paternal Origins of Health and Disease" and guide innovation of intervention algorithms to achieve 'healthier' outcomes in future generations. All this will revolutionize our understanding of human disease etiology.

Persisting neurobehavioral consequences of daily or intermittent paternal cannabis administration in F1 and F2 Rats

Repeated paternal preconception exposure to Δ9-tetrahydrocannabinol (Δ9-THC) alone or together with the other constituents in a cannabis extract has been shown in our earlier studies in rats to cause significant neurobehavioral impairment in their offspring. In the current study, we compared the effects of daily cannabis extract (CE) exposure to cannabis on two consecutive days per week, modeling weekend cannabis use in human. The CE contained Δ9-THC as well as cannabidiol and cannabinol. We also extended the investigation of the study to cross-generational effects of grand-paternal cannabis exposure on the F2 generation and included testing the effects of paternal cannabis exposure on responding for opiate self-administration in F1 and F2 generation offspring. We replicated the findings of neurobehavioral impairment in F1 offspring of male rats exposed to cannabis extract containing 4 mg/kg/day of Δ9-THC daily for four weeks prior to mating with drug naïve females. The 4-week cannabis extract exposure caused a significant decrease in weight gain in the male rats exposed daily. In contrast, their offspring showed significantly greater body weights and anogenital distances (AGD) in the third to fourth weeks after birth. The behavioral effects seen in the F1 generation were increased habituation of locomotor activity in the figure-8 maze in female offspring and increased lever pressing for the opiate drug remifentanil in male offspring. The F2 generation showed significantly impaired negative geotaxis and an elimination of the typical sex-difference in locomotor activity, with effects not seen in the F1 generation. This study shows that daily paternal cannabis exposure for four weeks prior to mating causes significant neurobehavioral impairment in the F1 and F2 offspring. Intermittent exposure on two consecutive days per week for four weeks caused comparable neurobehavioral impairment. In sum, there should be concern about paternal as well as maternal exposure to cannabis concerning neurobehavioral development of their offspring.

Epigenetic mechanisms linking early-life adversities and mental health

Early-life adversities, whether prenatal or postnatal exposure, have been linked to adverse mental health outcomes later in life increasing the risk of several psychiatric disorders. Research on its neurobiological consequences demonstrated an association between exposure to adversities and persistent alterations in the structure, function, and connectivity of the brain. Consistent evidence supports the idea that regulation of gene expression through epigenetic mechanisms are involved in embedding the impact of early-life experiences in the genome and mediate between social environments and later behavioral phenotypes. In addition, studies from rodent models and humans suggest that these experiences and the acquired risk factors can be transmitted through epigenetic mechanisms to offspring and the following generations potentially contributing to a cycle of disease or disease risk. However, one of the important aspects of epigenetic mechanisms, unlike genetic sequences that are fixed and unchangeable, is that although the epigenetic markings are long-lasting, they are nevertheless potentially reversible. In this review, we summarize our current understanding of the epigenetic mechanisms involved in the mental health consequences derived from early-life exposure to malnutrition, maltreatment and poverty, adversities with huge and pervasive impact on mental health. We also discuss the evidence about transgenerational epigenetic inheritance in mammals and experimental data suggesting that suitable social and pharmacological interventions could reverse adverse epigenetic modifications induced by early-life negative social experiences. In this regard, these studies must be accompanied by efforts to determine the causes that promote these adversities and that result in health inequity in the population.

Parental experiences orchestrate locust egg hatching synchrony by regulating nuclear export of precursor miRNA

Parental experiences can affect the phenotypic plasticity of offspring. In locusts, the population density that adults experience regulates the number and hatching synchrony of their eggs, contributing to locust outbreaks. However, the pathway of signal transmission from parents to offspring remains unclear. Here, we find that transcription factor Forkhead box protein N1 (FOXN1) responds to high population density and activates the polypyrimidine tract-binding protein 1 (Ptbp1) in locusts. FOXN1-PTBP1 serves as an upstream regulator of miR-276, a miRNA to control egg-hatching synchrony. PTBP1 boosts the nucleo-cytoplasmic transport of pre-miR-276 in a "CU motif"-dependent manner, by collaborating with the primary exportin protein exportin 5 (XPO5). Enhanced nuclear export of pre-miR-276 elevates miR-276 expression in terminal oocytes, where FOXN1 activates Ptbp1 and leads to egg-hatching synchrony in response to high population density. Additionally, PTBP1-prompted nuclear export of pre-miR-276 is conserved in insects, implying a ubiquitous mechanism to mediate transgenerational effects.

Sperm long non-coding RNAs as markers for ram fertility

It is critical in sheep farming to accurately estimate ram fertility for maintaining reproductive effectiveness and for production profitability. However, there is currently a lack of reliable biomarkers to estimate semen quality and ram fertility, which is hindering advances in animal science and technology. The objective of this study was to uncover long non-coding RNAs (lncRNAs) in sperm from rams with distinct fertility phenotypes. Mature rams were allocated into two groups: high and low fertility (HF; n = 31; 94.5 ± 2.8%, LF; n = 25; 83.1 ± 5.73%; P = 0.028) according to the pregnancy rates sired by the rams (average pregnancy rate; 89.4 ± 7.2%). Total RNAs were isolated from sperm of the highest- and lowest-fertility rams (n = 4, pregnancy rate; 99.2 ± 1.6%, and 73.6 ± 4.4%, respectively) followed by next-generation sequencing of the transcripts. We uncovered 11,209 lncRNAs from the sperm of rams with HF and LF. In comparison to each other, there were 93 differentially expressed (DE) lncRNAs in sperm from the two distinct fertility phenotypes. Of these, 141 mRNAs were upregulated and 134 were downregulated between HF and LF, respectively. Genes commonly enriched for 9 + 2 motile cilium and sperm flagellum were ABHD2, AK1, CABS1, ROPN1, SEPTIN2, SLIRP, and TEKT3. Moreover, CABS1, CCDC39, CFAP97D1, ROPN1, SLIRP, TEKT3, and TTC12 were commonly enriched in flagellated sperm motility and sperm motility. Differentially expressed mRNAs were enriched in the top 16 KEGG pathways. Targets of the differentially expressed lncRNAs elucidate functions in cis and trans manner using the genetic context of the lncRNA locus, and lncRNA sequences revealed 471 mRNAs targets of 10 lncRNAs. This study illustrates the existence of potential lncRNA biomarkers that can be implemented in analyzing the quality of ram sperm and determining the sperm fertility and is used in breeding soundness exams for precision livestock farming to ensure food security on a global scale.

A comprehensive analysis of spermatozoal RNA elements in idiopathic infertile males undergoing fertility treatment

Current approaches to diagnosing male infertility inadequately assess the complexity of the male gamete. Beyond the paternal haploid genome, spermatozoa also deliver coding and non-coding RNAs to the oocyte. While sperm-borne RNAs have demonstrated potential involvement in embryo development, the underlying mechanisms remain unclear. In this study, 47 sperm samples from normozoospermic males undergoing fertility treatment using donor oocytes were sequenced and analyzed to evaluate associations between sperm RNA elements (exon-sized sequences) and blastocyst progression. A total of 366 RNA elements (REs) were significantly associated with blastocyst rate (padj < 0.05), some of which were linked to genes related to critical developmental processes, including mitotic spindle formation and both ectoderm and mesoderm specification. Of note, 27 RE-associated RNAs are predicted targets of our previously reported list of developmentally significant miRNAs. Inverse RE-miRNA expression patterns were consistent with miRNA-mediated down-regulation. This study provides a comprehensive set of REs which differ by the patient's ability to produce blastocysts. This knowledge can be leveraged to improve clinical screening of male infertility and ultimately reduce time to pregnancy.

Trans-generational effects of parental exposure to drugs of abuse on offspring memory functions

Recent evidence reported that parental-derived phenotypes can be passed on to the next generations. Within the inheritance of epigenetic characteristics allowing the transmission of information related to the ancestral environment to the offspring, the specific case of the trans-generational effects of parental drug addiction has been extensively studied. Drug addiction is a chronic disorder resulting from complex interactions among environmental, genetic, and drug-related factors. Repeated exposures to drugs induce epigenetic changes in the reward circuitry that in turn mediate enduring changes in brain function. Addictive drugs can exert their effects trans-generally and influence the offspring of addicted parents. Although there is growing evidence that shows a wide range of behavioral, physiological, and molecular phenotypes in inter-, multi-, and trans-generational studies, transmitted phenotypes often vary widely even within similar protocols. Given the breadth of literature findings, in the present review, we restricted our investigation to learning and memory performances, as examples of the offspring's complex behavioral outcomes following parental exposure to drugs of abuse, including morphine, cocaine, cannabinoids, nicotine, heroin, and alcohol.

Prenatal maternal glucocorticoid exposure modifies sperm miRNA profiles across multiple generations in the guinea-pig

Maternal stress and glucocorticoid exposure during pregnancy have multigenerational effects on neuroendocrine function and behaviours in offspring. Importantly, effects are transmitted through the paternal lineage. Altered phenotypes are associated with profound differences in transcription and DNA methylation in the brain. In the present study, we hypothesized that maternal prenatal synthetic glucocorticoid (sGC) exposure in the F0 pregnancy will result in differences in miRNA levels in testes germ cells and sperm across multiple generations, and that these changes will associate with modified microRNA (miRNA) profiles and gene expression in the prefrontal cortex (PFC) of subsequent generations. Pregnant guinea-pigs (F0) were treated with multiple courses of the sGC betamethasone (Beta) (1 mg kg-1; gestational days 40, 41, 50, 51, 60 and 61) in late gestation. miRNA levels were assessed in testes germ cells and in F2 PFC using the GeneChip miRNA 4.0 Array and candidate miRNA measured in epididymal sperm by quantitative real-time PCR. Maternal Beta exposure did not alter miRNA levels in germ cells derived from the testes of adult male offspring. However, there were significant differences in the levels of four candidate miRNAs in the sperm of F1 and F2 adult males. There were no changes in miRNA levels in the PFC of juvenile F2 female offspring. The present study has identified that maternal Beta exposure leads to altered miRNA levels in sperm that are apparent for at least two generations. The fact that differences were confined to epididymal sperm suggests that the intergenerational effects of Beta may target the epididymis. KEY POINTS: Paternal glucocorticoid exposure prior to conception leads to profound epigenetic changes in the brain and somatic tissues in offspring, and microRNAs (miRNAs) in sperm may mediate these changes. We show that there were significant differences in the miRNA profile of epididymal sperm in two generations following prenatal glucocorticoid exposure that were not observed in germ cells derived from the testes. The epididymis is a probable target for intergenerational programming. The effects of prenatal glucocorticoid treatment may span multiple generations.

Parental preconception stress in zebrafish induces long-lasting anxiety in offspring

The growth and function of the vertebrate brain are impacted by environmental stimuli and early life stress. Adults who experience chronic stress during early life are more likely to suffer various neurodevelopmental and health issues. However, our understanding of how these specific environmental signals at different developmental stages affect brain development is poorly understood. In this study, we investigated if stress in parents prior to conception modulates neurodevelopment in offspring. We used a chronic unpredictable stress model adapted to zebrafish, which is an increasingly popular vertebrate model in neuroscience research to investigate the effects of both maternal and paternal preconception stress on offspring behavior. We evaluated the responsiveness of three anxiety-related behavioral paradigms in zebrafish: the novel tank test, thigmotaxis, and shoaling behavior. We found larvae from stressed females exhibited anxiety-like behavior in a thigmotaxis assay. As these larvae matured into adults, they continued to exhibit anxiety-like behavior in a novel tank and shoaling behavioral assay. These studies indicate preconception stress exposure in parents can induce life-long alterations in offspring neurodevelopment. Further, these results expand the hypothesis that chronically elevated glucocorticoid signaling not only in stressed mothers, but also stressed dads can affect neurodevelopment in offspring. We propose that zebrafish may be a useful model to study the transgenerational effects of chronic stress mediated via the maternal and paternal line.

Optimized total RNA isolation from bovine sperm with enhanced sperm head lysis

Increasing evidence of sperm RNA's role in fertilization and embryonic development has provided impetus for its isolation and thorough characterization. Sperm are considered tough-to-lyse cells due to the compact condensed DNA in sperm heads. Lack of consensus among bovine sperm RNA isolation protocols introduces experimental variability in transcriptome studies. Here, we describe an optimized method for total RNA isolation from bovine sperm using the TRIzol reagent. This study critically investigated the effects of various lysis conditions on sperm RNA isolation. Sperm suspended in TRIzol were subjected to a combination of mechanical treatments (sonication and passage through a 30G needle and syringe) and chemical treatments (supplementation with reducing agents 1,4-dithiothreitol and tris(2-carboxyethyl) phosphine hydrochloride (TCEP)). Microscopic evaluation of sperm lysis confirmed preferential sperm tail versus sperm head lysis. Interestingly, only TCEP-supplemented TRIzol (both mechanical treatments) had progressive sperm head lysis and consistently yielded total sperm RNA. Furthermore, RNA integrity was confirmed based on the electrophoresis profile and an absence of genomic DNA and somatic cells (e.g., epithelial cells, spermatids, etc.) with RT-qPCR. Our findings highlighted the importance of sperm lysis, specifically of the sperm head using TCEP with mechanical treatment, in total RNA isolation and presented a bovine-specific sperm RNA isolation method to reduce experimental variabilities.

HPA flexibility and FKBP5: promising physiological targets for conservation

Hypothalamic-pituitary-adrenal axis (HPA) flexibility is an emerging concept recognizing that individuals that will cope best with stressors will probably be those using their hormones in the most adaptive way. The HPA flexibility concept considers glucocorticoids as molecules that convey information about the environment from the brain to the body so that the organismal phenotype comes to complement prevailing conditions. In this context, FKBP5 protein appears to set the extent to which circulating glucocorticoid concentrations can vary within and across stressors. Thus, FKBP5 expression, and the HPA flexibility it causes, seem to represent an individual's ability to regulate its hormones to orchestrate organismal responses to stressors. As FKBP5 expression can also be easily measured in blood, it could be a worthy target of conservation-oriented research attention. We first review the known and likely roles of HPA flexibility and FKBP5 in wildlife. We then describe putative genetic, environmental and epigenetic causes of variation in HPA flexibility and FKBP5 expression among and within individuals. Finally, we hypothesize how HPA flexibility and FKBP5 expression should affect organismal fitness and hence population viability in response to human-induced rapid environmental changes, particularly urbanization. This article is part of the theme issue 'Endocrine responses to environmental variation: conceptual approaches and recent developments'.

Semen proteome and transcriptome of the endangered black-footed ferret (Mustela nigripes) show association with the environment and fertility outcome

The ex situ population of the endangered black-footed ferret (Mustela nigripes) has been experiencing declines in reproductive success over the past 30 years of human-managed care. A potential cause may be environmental-dependent inbreeding depression with diet being one of the contributing factors since ferrets are not fed their natural diet of prairie dogs. Here, we generated and analyzed semen proteome and transcriptome data from both wild and ex situ ferrets maintained on various diets. We identified 1757 proteins across all samples, with 149 proteins unique to the semen of wild ferrets and forming a ribosomal predicted protein-protein interaction cluster. Wild ferrets also differed from ex situ ferrets in their transcriptomic profile, showing enrichment in ribosomal RNA processing and potassium ion transport. Successful fertility outcomes documented for ex situ ferrets showed the strongest association with the semen transcriptome, with enrichment in genes involved in translation initiation and focal adhesion. Fertility also synergized with the effect of diet on differentially expressed transcriptomes, mainly affecting genes enriched in mitochondrial function. Our data and functional networks are important for understanding the causes and mechanisms of declining fertility in the ex situ ferret population and can be used as a resource for future conservation efforts.

Inter- and transgenerational heritability of preconception chronic stress or alcohol exposure: Translational outcomes in brain and behavior

Chronic stress and alcohol (ethanol) use are highly interrelated and can change an individual's behavior through molecular adaptations that do not change the DNA sequence, but instead change gene expression. A recent wealth of research has found that these nongenomic changes can be transmitted across generations, which could partially account for the "missing heritability" observed in genome-wide association studies of alcohol use disorder and other stress-related neuropsychiatric disorders. In this review, we summarize the molecular and behavioral outcomes of nongenomic inheritance of chronic stress and ethanol exposure and the germline mechanisms that could give rise to this heritability. In doing so, we outline the need for further research to: (1) Investigate individual germline mechanisms of paternal, maternal, and biparental nongenomic chronic stress- and ethanol-related inheritance; (2) Synthesize and dissect cross-generational chronic stress and ethanol exposure; (3) Determine cross-generational molecular outcomes of preconception ethanol exposure that contribute to alcohol-related disease risk, using cancer as an example. A detailed understanding of the cross-generational nongenomic effects of stress and/or ethanol will yield novel insight into the impact of ancestral perturbations on disease risk across generations and uncover actionable targets to improve human health.

Chronically high stress hormone levels dysregulate sperm long noncoding RNAs and their embryonic microinjection alters development and affective behaviours

Previous studies on paternal epigenetic inheritance have shown that sperm RNAs play a role in this type of inheritance. The microinjection of sperm small noncoding RNAs into fertilised mouse oocytes induces reprogramming of the early embryo, which is thought to be responsible for the differences observed in adult phenotype. While sperm long noncoding RNAs (lncRNAs) have also been investigated in a previous study, their microinjection into fertilised oocytes did not yield conclusive results regarding their role in modulating brain development and adult behavioural phenotypes. Therefore, in the current study we sought to investigate this further. We used our previously established paternal corticosterone (stress hormone) model to assess sperm lncRNA expression using CaptureSeq, a sequencing technique that is more sensitive than the ones used in other studies in the field. Paternal corticosterone exposure led to dysregulation of sperm long noncoding RNA expression, which encompassed lncRNAs, circular RNAs and transposable element transcripts. Although they have limited functional annotation, bioinformatic approaches indicated the potential of these lncRNAs in regulating brain development and function. We then separated and isolated the sperm lncRNAs and performed microinjections into fertilised oocytes, to generate embryos with modulated lncRNA populations. We observed that the resulting adult offspring had lower body weight and altered anxiety and affective behavioural responses, demonstrating roles for lncRNAs in modulating development and brain function. This study provides novel insights into the roles of lncRNAs in epigenetic inheritance, including impacts on brain development and behaviours of relevance to affective disorders.

Small RNAs: an ideal choice as sperm quality biomarkers

Spermatozoa were classically known as vehicles for the delivery of the paternal genome to the oocyte. However, in 1962, spermatozoa were discovered to carry significant amounts of RNA in them, which raised questions about the significance of these molecules in such a highly specialized cell. Scientific research in the last six decades has investigated the biological significance of sperm RNAs by various means. Irrespective of what sperm RNAs do, their presence in spermatozoa has attracted attention for their exploitation as biomarkers of fertility. Research in this direction started in the year 2000 and is still underway. A major hurdle in this research is the definition of the standard human sperm RNAome. Only a few normozoospermic samples have been analyzed to define the normal sperm RNAome. In this article, we provide a perspective on the suitability of sperm RNAs as biomarkers of fertility and the importance of defining the normal sperm RNAome before we can succeed in identifying RNA-based biomarkers of sperm quality and fertility. The identification of sperm RNA biomarkers of fertility can be exploited for quality screening of donor sperm samples, explain infertility in idiopathic cases, and RNA therapeutics for the treatment of male infertility.

Frequency, morbidity and equity - the case for increased research on male fertility

Currently, most men with infertility cannot be given an aetiology, which reflects a lack of knowledge around gamete production and how it is affected by genetics and the environment. A failure to recognize the burden of male infertility and its potential as a biomarker for systemic illness exists. The absence of such knowledge results in patients generally being treated as a uniform group, for whom the strategy is to bypass the causality using medically assisted reproduction (MAR) techniques. In doing so, opportunities to prevent co-morbidity are missed and the burden of MAR is shifted to the woman. To advance understanding of men's reproductive health, longitudinal and multi-national centres for data and sample collection are essential. Such programmes must enable an integrated view of the consequences of genetics, epigenetics and environmental factors on fertility and offspring health. Definition and possible amelioration of the consequences of MAR for conceived children are needed. Inherent in this statement is the necessity to promote fertility restoration and/or use the least invasive MAR strategy available. To achieve this aim, protocols must be rigorously tested and the move towards personalized medicine encouraged. Equally, education of the public, governments and clinicians on the frequency and consequences of infertility is needed. Health options, including male contraceptives, must be expanded, and the opportunities encompassed in such investment understood. The pressing questions related to male reproductive health, spanning the spectrum of andrology are identified in the Expert Recommendation.

Differential susceptibility of male and female germ cells to glucocorticoid-mediated signaling

While physiologic stress has long been known to impair mammalian reproductive capacity through hormonal dysregulation, mounting evidence now suggests that stress experienced prior to or during gestation may also negatively impact the health of future offspring. Rodent models of gestational physiologic stress can induce neurologic and behavioral changes that persist for up to three generations, suggesting that stress signals can induce lasting epigenetic changes in the germline. Treatment with glucocorticoid stress hormones is sufficient to recapitulate the transgenerational changes seen in physiologic stress models. These hormones are known to bind and activate the glucocorticoid receptor (GR), a ligand-inducible transcription factor, thus implicating GR-mediated signaling as a potential contributor to the transgenerational inheritance of stress-induced phenotypes. Here, we demonstrate dynamic spatiotemporal regulation of GR expression in the mouse germline, showing expression in the fetal oocyte as well as the perinatal and adult spermatogonia. Functionally, we find that fetal oocytes are intrinsically buffered against changes in GR signaling, as neither genetic deletion of GR nor GR agonism with dexamethasone altered the transcriptional landscape or the progression of fetal oocytes through meiosis. In contrast, our studies revealed that the male germline is susceptible to glucocorticoid-mediated signaling, specifically by regulating RNA splicing within the spermatogonia, although this does not abrogate fertility. Together, our work suggests a sexually dimorphic function for GR in the germline, and represents an important step towards understanding the mechanisms by which stress can modulate the transmission of genetic information through the germline.

Divergent planes of nutrition in mature rams influences body composition, hormone and metabolite concentrations, and offspring birth measurements, but not semen characteristics or offspring growth

Objectives of this experiment were to characterize the effects of ram plane of nutrition on body composition, concentrations of hormones and metabolites, sperm characteristics, and offspring outcomes. Mature Rambouillet rams (n = 24, BW = 82.9 ± 2.63 kg) were individually housed and randomly assigned to either a positive (POS; n = 8), maintenance (MAINT; n = 8), or negative (NEG; n = 8) plane of nutrition for an 84-day feeding period. Rams were fed a common diet, with daily feed allocations adjusted weekly based on body weight (BW) to achieve the targeted weight gain or loss (approximately 12% of initial BW). On 0, 28, 56, and 84-d, body condition score (BCS) and scrotal circumference (SC) were recorded, and blood and semen were collected. Following the feeding period, rams were placed in pens with 10 ewes each for a 28-d breeding period. Ewes were managed similarly throughout gestation and body weight and measurements were recorded at birth and weaning. Data were analyzed as repeated measures in time where appropriate with the mixed procedure of SAS, and individual ram was the experimental unit for all analysis. Ram BW was influenced by a treatment × day interaction (P < 0.001), with POS (0.12 ± 0.01 kg) having greater daily weight change than MAINT (0.1 ± 0.01 kg), which was greater than NEG (-0.12 ± 0.01 kg). Ram BCS and SC were influenced by treatment × day interactions (P ≤ 0.01), being similar on day 0 but POS being greater than NEG by day 56. Concentrations of triiodothyronine (T3) and T3:T4 ratio exhibited treatment × day interactions (P ≤ 0.02), as POS had greater values than NEG by day 84 (P ≤ 0.02). Concentration of insulin-like growth factor-1 was greater in POS than MAINT and NEG (P ≤ 0.02), and non-esterified fatty acids and thyroxine (T4) were influenced by a day effect (P ≤ 0.01), but testosterone was unaffected (P ≥ 0.09). Minimal differences in semen volume, sperm concentration, motility, or morphology were observed among treatments (P ≥ 0.31). A similar proportion of ewes bred by rams in the respective treatments lambed and weaned lambs (P ≥ 0.54). Birth weight, chest circumference, and shoulder-hip length were greater (P ≤ 0.05) in NEG lambs compared with POS and MAINT; however, no differences were detected in weaning weight and weaning body measurements (P ≥ 0.40). Findings suggest paternal nutrition during the period of sperm development may influence offspring outcomes, potentially as a result of in-utero programming of paternal origin.

Effects of paternal ionizing radiation exposure on fertility and offspring's health

Purpose

The intergenerational effects of ionizing radiation remain controversial. Extensive insights have been revealed for DNA mutations and cancer incidence in progeny, yet many of these results were obtained by immediate post-radiation mating. However, conception at short times after radiation exposure is likely to be avoided. After a long period of fertility recovery, whether unexposed sperm derived from exposed spermatogonia would challenge the health of the offspring is not yet clearly demonstrated.

Methods

Ten-week-old C57BL/6J males underwent whole-body acute γ irradiation at 0 and 6.4 Gy. Testes and sperm were collected at different times after radiation to examine reproductive changes. The reproductive, metabolic, and neurodevelopmental parameters were measured in the offspring of controls and the offspring derived from irradiated undifferentiated spermatogonia.

Results

Paternal fertility was lost after acute 6.4 Gy γ radiation and recovered at 10-11 weeks post irradiation in mice. The reproductive, metabolic, and neurodevelopmental health of offspring born to irradiated undifferentiated spermatogonia were comparable to those of controls.

Conclusion

The male mice could have healthy offspring after recovery from the damage caused by ionizing radiation.

Paternal immune activation by Poly I:C modulates sperm noncoding RNA profiles and causes transgenerational changes in offspring behavior

Paternal pre-conceptual environmental experiences, such as stress and diet, can affect offspring brain and behavioral phenotypes via epigenetic modifications in sperm. Furthermore, maternal immune activation due to infection during gestation can reprogram offspring behavior and brain functioning in adulthood. However, the effects of paternal pre-conceptual exposure to immune activation on the behavior and physiology of offspring (F1) and grand-offspring (F2) are not currently known. We explored effects of paternal pre-conceptual exposure to viral-like immune activation on F1 and F2 behavioral and physiological phenotypes using a C57BL/6J mouse model. Males were treated with a single injection (intraperitoneal) of the viral mimetic polyinosinic:polycytidylic acid (Poly I:C: 12 mg/kg) then bred with naïve female mice four weeks after the Poly I:C (or 0.9% saline control) injection. The F1 offspring of Poly I:C treated fathers displayed increased depression-like behavior in the Porsolt swim test, an altered stress response in the novelty-suppressed feeding test, and significant transcriptomic changes in their hippocampus. Additionally, the F1 male offspring of Poly I:C treated F0 males showed significantly increased immune responsivity after a Poly I:C immune challenge (12 mg/kg). Furthermore, the F2 male grand-offspring took longer to enter and travelled significantly shorter distances in the light zone of the light/dark box. An analysis of the small noncoding RNA profiles in sperm from Poly I:C treated males and their male offspring revealed significant effects of Poly I:C on the sperm microRNA content at the time of conception and on the sperm PIWI-interacting RNA content of the male offspring. Notably, eight miRNAs with an FDR < 0.05 (miR-141-3p, miR-126b-5p, miR-669o-5p, miR-10b-3p, miR-471-5p, miR-463-5p, miR-148b-3p, and miR-181c-5p) were found to be significantly downregulated in the sperm of Poly I:C treated males. Collectively, we demonstrate that paternal pre-conceptual exposure to a viral immune challenge results in both intergenerational and transgenerational effects on brain and behavior that may be mediated by alterations in the sperm small noncoding RNA content.