Paternal ethanol exposure and behavioral abnormities in offspring: associated alterations in imprinted gene methylation

Preconception ethanol exposure changes anxiety, depressive and checking-like behavior and alter the expression levels of MAO-B in male offspring

Alcohol use, which alters the epigenome, increases the probability that it could affect subsequent generations, even if they were never directly exposed to ethanol or even in utero. We explored the effects of parental ethanol exposure before conception on behavioral changes in the offspring. Considering the role of Monoamine oxidase-B (MAO-B) in dopamine turnover in the prefrontal cortex (PFC) and its influence on behavior, and taking into account that ethanol exposure could alter MAO-B, we assessed the protein levels in the offspring. Male and female rats were exposed to ethanol for 30 days and then allowed ten days of abstinence. Afterward, they were mated with either control or ethanol-exposed rats. The F1 and F2 male offspring underwent tests to assess behavioral changes. Additionally, the levels of MAO-B in the PFC were evaluated. Results revealed that in the F1, anxiety increased only in the bi-parental ethanol-exposed male offspring in the elevated plus maze test (p < 0.05), while depressive-like behavior rose only in maternal and bi-parental ethanol-exposed offspring (p < 0.01). However, compulsive-like behavior increased in all ethanol-exposed offspring (p < 0.01). No significant phenotypic changes were observed in the F2. The levels of MAO-B in the PFC increased in the maternal (p < 0.05) and bi-parental ethanol-exposed offspring (p < 0.01). Our study demonstrates that parental ethanol exposure, even in the days preceding mating, adversely affects behaviors and induces molecular changes in the brain. Given these findings, it becomes imperative to monitor children exposed to parental (especially maternal) ethanol for the prevention of mental disorders.

Multigenerational effects of alcohol: A behavioral study in three zebrafish populations

Fetal alcohol exposure can result in fetal alcohol spectrum disorder (FASD), which encompasses a range of cognitive and behavioral impairments. Although zebrafish have been used as a reliable model to study FASD, little is known about the ontogeny of this disorder and population differences in subsequent generations not directly exposed to alcohol. In this study, we evaluated the behavioral outcomes of zebrafish populations AB, Outbred (OB), and Tubingen (TU), offspring of parents exposed to alcohol during embryonic development. The offspring of adult fish with FASD (exposed to 1 % alcohol at the embryonic stage) was compared to the offspring of unexposed parental fish (0 % alcohol at the embryo phase). The behavioral profile of the offspring was assessed at 6 days post-fertilization (dpf) and 45 dpf. At 6dpf, the AB FASD offspring exhibited hyperactivity and increased time at the edge of the tank, while the TU and OB FASD offspring showed hypoactivity. At 45dpf, TU fish maintained the larval locomotor pattern, characterized by decreased average speed and total distance traveled and increased immobility. However, AB and OB fish did not show alterations in locomotor activity and anxiety-related responses at 45dpf. Our results demonstrate, for the first time, that FASD zebrafish offspring display behavioral differences, which were most evident during the early ontogenetic phase (6dpf) but may vary throughout animal ontogeny. TU fish exhibited the most consistent behavioral pattern across different developmental stages. These findings provide insights into the multigenerational and persistent behavioral consequences of embryonic alcohol exposure in zebrafish. Further research should focus on other features that can be inherited and the development of treatments for the offspring affected by it.

Alcohol: Epigenome alteration and inter/transgenerational effect

While DNA serves as the fundamental genetic blueprint for an organism, it is not a static entity. Gene expression, the process by which genetic information is utilized to create functional products like proteins, can be modulated by a diverse range of environmental factors. Epigenetic mechanisms, including DNA methylation, histone modification, and microRNAs, play a pivotal role in mediating the intricate interplay between the environment and gene expression. Intriguingly, alterations in the epigenome have the potential to be inherited across generations. Alcohol use disorder (AUD) poses significant health issues worldwide. Alcohol has the capability to induce changes in the epigenome, which can be inherited by offspring, thus impacting them even in the absence of direct alcohol exposure. This review delves into the impact of alcohol on the epigenome, examining how its effects vary based on factors such as the age of exposure (adolescence or adulthood), the duration of exposure (chronic or acute), and the specific sample collected (brain, blood, or sperm). The literature underscores that alcohol exposure can elicit diverse effects on the epigenome during different life stages. Furthermore, compelling evidence from human and animal studies demonstrates that alcohol induces alterations in epigenome content, affecting both the brain and blood. Notably, rodent studies suggest that these epigenetic changes can result in lasting phenotype alterations that extend across at least two generations. In conclusion, the comprehensive literature analysis supports the notion that alcohol exposure induces lasting epigenetic alterations, influencing the behavior and health of future generations. This knowledge emphasizes the significance of addressing the potential transgenerational effects of alcohol and highlights the importance of preventive measures to minimize the adverse impact on offspring.

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.

Oxidative Stress Biomarkers in Male Infertility: Established Methodologies and Future Perspectives

Male fertility can be affected by oxidative stress (OS), which occurs when an imbalance between the production of reactive oxygen species (ROS) and the body's ability to neutralize them arises. OS can damage cells and influence sperm production. High levels of lipid peroxidation have been linked to reduced sperm motility and decreased fertilization ability. This literature review discusses the most commonly used biomarkers to measure sperm damage caused by ROS, such as the high level of OS in seminal plasma as an indicator of imbalance in antioxidant activity. The investigated biomarkers include 8-hydroxy-2-deoxyguanosine acid (8-OHdG), a marker of DNA damage caused by ROS, and F2 isoprostanoids (8-isoprostanes) produced by lipid peroxidation. Furthermore, this review focuses on recent methodologies including the NGS polymorphisms and differentially expressed gene (DEG) analysis, as well as the epigenetic mechanisms linked to ROS during spermatogenesis along with new methodologies developed to evaluate OS biomarkers. Finally, this review addresses a valuable insight into the mechanisms of male infertility provided by these advances and how they have led to new treatment possibilities. Overall, the use of biomarkers to evaluate OS in male infertility has supplied innovative diagnostic and therapeutic approaches, enhancing our understanding of male infertility mechanisms.

Influence of substance use on male reproductive health and offspring outcomes

The prevalence of substance use globally is rising and is highest among men of reproductive age. In Africa, and South and Central America, cannabis use disorder is most prevalent and in Eastern and South-Eastern Europe, Central America, Canada and the USA, opioid use disorder predominates. Substance use might be contributing to the ongoing global decline in male fertility, and emerging evidence has linked paternal substance use with short-term and long-term adverse effects on offspring development and outcomes. This trend is concerning given that substance use is increasing, including during the COVID-19 pandemic. Preclinical studies have shown that male preconception substance use can influence offspring brain development and neurobehaviour through epigenetic mechanisms. Additionally, human studies investigating paternal health behaviours during the prenatal period suggest that paternal tobacco, opioid, cannabis and alcohol use is associated with reduced offspring mental health, in particular hyperactivity and attention-deficit hyperactivity disorder. The potential effects of paternal substance use are areas in which to focus public health efforts and health-care provider counselling of couples or individuals interested in conceiving.

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.

Paternal alcohol exposure attenuates maintenance and reinstated operant responding for alcohol in the offspring of rats

BACKGROUND

The heritability of alcohol use disorder is close to 50%, yet common genetic variants account for less than 5% of risk. The missing heritability may reflect environmental exposure in the parents prior to conception. Indeed, paternal alcohol exposure has many behavioral and biological consequences for rodent offspring. We recently found that paternal alcohol exposure attenuated the acquisition of operant alcohol self-administration in offspring of rats of both sexes. Here we test whether this effect extends to other phases of operant self-administration thought to model motivation, craving, and relapse.

METHODS

Wistar male rats exposed to alcohol vapors or air for 6 weeks were mated with alcohol-naïve females 8 weeks later. The adult offspring were trained to lever press for alcohol and tested under several conditions: (1) maintenance responding under a progressive ratio schedule, (2) extinction responding due to removal of the alcohol delivery contingency, (3) reinstatement of extinguished responding in the presence of alcohol-associated cues, and (4) reinitiation of lever press responding for alcohol delivery under fixed and progressive ratio schedules.

RESULTS

Alcohol-sired offspring showed reduced responding under the progressive ratio schedule and blunted cue-induced reinstatement of extinguished responding. Alcohol-sired offspring also emitted fewer responses during extinction sessions and did not reinitiate responding to the same extent as control-sired rats after alcohol delivery was restored.

CONCLUSIONS

Across all conditions, paternal alcohol exposure led to a reduction in the reinforcing effects of alcohol in offspring. These results are consistent with studies conducted with paternal cocaine exposure except that here we find effects in rats of both sexes.

Developmental origins of health and disease: Impact of paternal nutrition and lifestyle

Most epidemiological and experimental studies have focused on maternal influences on offspring's health. The impact of maternal undernutrition, overnutrition, hypoxia, and stress is linked to adverse offspring outcomes across a range of systems including cardiometabolic, respiratory, endocrine, and reproduction among others. During the past decade, it has become evident that paternal environmental factors are also linked to the development of diseases in offspring. In this article, we aim to outline the current understanding of the impact of male health and environmental exposure on offspring development, health, and disease and explore the mechanisms underlying the paternal programming of offspring health. The available evidence suggests that poor paternal pre-conceptional nutrition and lifestyle, and advanced age can increase the risk of negative outcomes in offspring, via both direct (genetic/epigenetic) and indirect (maternal uterine environment) effects. Beginning at preconception, and during utero and the early life after birth, cells acquire an epigenetic memory of the early exposure which can be influential across the entire lifespan and program a child's health. Potentially not only mothers but also fathers should be advised that maintaining a healthy diet and lifestyle is important to improve offspring health as well as the parental health status. However, the evidence is mostly based on animal studies, and well-designed human studies are urgently needed to verify findings from animal data.

Paternal exposure to arsenic and sperm DNA methylation of imprinting gene Meg3 in reproductive-aged men

BACKGROUND

Prenatal exposure to arsenic and mercury have been associated with adverse pregnancy outcomes that might be in part mediated by dynamic modification of imprinting gene that are emerging mechanism.

OBJECTIVES

The objective of this study was to examine the impacts of paternal exposure to arsenic and co-exposure to arsenic and mercury on human sperm DNA methylation status of imprinting genes, respectively.

METHODS

A total of 352 male subjects (23-52 years old) were recruited and demographic data were obtained through questionnaires. Urinary arsenic and mercury levels were measured using hydride generation-atomic fluorescence spectrometer. Multivariate regression model was employed to investigate the relationship between urinary arsenic levels and sperm DNA methylation status at H19, Meg3 and Peg3, measured by pyrosequencing, and evaluating the interaction with mercury.

RESULTS

After adjusting potential confounds factors by multivariate regression model, the results indicated a significantly positive relationship between urinary arsenic levels and the methylation status of Meg3 at both mean level (β =  + 0.125, p < 0.001) and all individual CpGs, i.e., CpG1 (β =  + 0.094, p < 0.001), CpG2 (β =  + 0.132, p < 0.001), CpG3 (β =  + 0.121, p < 0.001), CpG4 (β =  + 0.142, p < 0.001), CpG5 (β =  + 0.111, p < 0.001), CpG6 (β =  + 0.120, p < 0.001), CpG7 (β =  + 0.143, p < 0.001), CpG8 (β =  + 0.139, p < 0.001) of Meg3 DMRs. The interaction effects analysis indicated the interaction effects of arsenic and mercury on Meg3 were not existing.

CONCLUSIONS

Paternal nonoccupational exposure to arsenic induces the altered DNA methylation status of Meg3 in human sperm DNA. In addition, the interaction effects of arsenic and mercury on Meg3 were not existing. These findings would implicate the sensibility of sperm epigenome for environmental pollutions.

Paternal genetic intergenerational and transgenerational effects of cadmium exposure on hormone synthesis disorders in progeny ovarian granulosa cells

To investigate the paternal genetic effects of cadmium (Cd) exposure on hormone synthesis disorders in the ovarian granulosa cells (GCs) of offspring. Here, male Sprague‒Dawley (SD) rats were gavaged with CdCl₂ (0, 0.5, 2, 8 mg/kg) from postnatal day (PND) 28-56, followed by mating with newly purchased healthy adult females to produce F1, and F1 adult males (PND 56) were mated with newly purchased healthy adult females to produce F2. The serum levels of estradiol (E₂) and progesterone (Pg) decreased in F1 but essentially returned to normal in F2. The levels of StAR, CYP11A1, CYP17A1, CYP19A1, and SF-1 showed different alterations in F1 and F2 ovarian GCs. The expression patterns of miRNAs and imprinted genes related to hormone synthesis in GCs of F1 and F2 differed, but methylation of hormone synthesis-related genes was not significantly altered (except for individual loci in F1). In addition, there were significant changes in the expression of imprinted genes and miRNAs in F0 and F1 sperm. We conclude that paternal Cd exposure causes intergenerational genetic effects (hormone synthesis disorders) and transgenerational effects (reparative changes in hormone synthesis function) in ovarian GCs. These genetic effects were related to the downregulation of StAR in F1 and the upregulation of CYP17A1, CYP19A1, StAR and SF-1 in F2. Important changes in miRNAs and imprinted genes were also observed, but not all alterations originated from paternal inheritance.

Sperm RNA Payload: Implications for Intergenerational Epigenetic Inheritance

There is mounting evidence that ancestral life experiences and environment can influence phenotypes in descendants. The parental environment regulates offspring phenotypes potentially via modulating epigenetic marks in the gametes. Here, we review examples of across-generational inheritance of paternal environmental effects and the current understanding of the role of small RNAs in such inheritance. We discuss recent advances in revealing the small RNA payload of sperm and how environmental conditions modulate sperm small RNAs. Further, we discuss the potential mechanism of inheritance of paternal environmental effects by focusing on sperm small RNA-mediated regulation of early embryonic gene expression and its role in influencing offspring phenotypes.

Paternal alcohol exposure has task- and sex-dependent behavioral effect in offspring

BACKGROUND

Endophenotypes for alcohol use disorder are well known and may reflect paternal exposure effects passed down to offspring via epigenetic mechanisms. Previously, we showed that paternal alcohol exposure prior to conception attenuates the acquisition of operant alcohol self-administration. We now test whether paternal alcohol exposure alters their offsprings' behavioral responses to alcohol (endophenotypes) and global DNA methylation levels in reward-related brain regions.

METHODS

Adult male rats were exposed to alcohol vapors or air for 6 weeks and mated with alcohol-naïve females 8 weeks later. Adult male and female offspring of the alcohol- and control-sired litters were tested on three behaviors 30 m after gavage with water or alcohol (1.5 g/kg): open field, elevated plus maze, and accelerating rotarod. Global DNA methylation levels in sperm, nucleus accumbens, and prefrontal cortex were examined in male sires and in another group of offspring.

RESULTS

Alcohol-sired males showed less anxiety-like behavior in the elevated plus maze that was not affected by alcohol administration. By contrast, alcohol had anxiolytic effects in the open field in male offspring only with no paternal alcohol effect. Neither paternal alcohol exposure nor alcohol administration altered locomotor activity in either sex. Sex-specific effects of paternal alcohol exposure were seen in the rotarod test. Alcohol-sired male offspring showed blunted sensitivity to the alcohol's motor-impairing effects, whereas alcohol-sired female offspring showed enhanced sensitivity. Global DNA methylation was altered in the sperm of alcohol-exposed males, but no changes were seen in their offspring.

CONCLUSIONS

Paternal alcohol exposure prior to conception has sex- and task-dependent effects on unconditioned behaviors in their offspring.

Genetics and epigenetics: paternal adolescent ethanol consumption in serotonin transporter knock-out rats and offspring sensitivity to ethanol

RATIONALE

Alcohol use disorder (AUD) is shown to have an overall heritability of around 50%. One of the genes associated with AUD is SLC6A4 (solute carrier family 6 member A4) which codes for the serotonin transporter (SERT). The study looked at serotonin dysfunction on ethanol consumption in adolescents and the subsequent intergenerational effects of drinking by using a rat model: SERT^+/+ (regular functioning), SERT^+/- (50% transporter reduction) and SERT^-/- (complete reduction).

OBJECTIVES

We investigated sex and genotype differences in ethanol consumption in SERT knock-out Wistar rats (F0) followed by studying behaviour in the offspring (F1) of the male drinkers to assess effects of paternal alcohol consumption.

METHODS

An intermittent access two-bottle choice paradigm (IA2BC) was used to yield ethanol drinking behaviour in F0 adolescent Wistar rats. The highest drinking males were mated to alcohol-naive females and their offspring were compared with controls. Drinking behaviour (IA2BC) and ethanol-induced motor coordination effects (via rotarod) were measured in the F1s.

RESULTS

F0 drinking saw no SERT genotype differences in males. However, females consumed higher volumes of ethanol compared to males, with SERT^-/- females showing the highest intake. A clearer genotype effect was seen in the F1 animals, with reduction in SERT activity leading to enhanced ethanol intake in both sexes. Importantly, paternal exposure to ethanol significantly reduced the ethanol induced motor side effects in offspring, independent of sex and genotype.

CONCLUSIONS

These indicate a difference in the way genetic factors may act across sexes and suggest the involvement of epigenetic mechanisms in the intergenerational effects of alcohol.

Paternal transgenerational nutritional epigenetic effect: A new insight into nutritional manipulation to reduce the use of antibiotics in animal feeding

The use of antibiotics in animal feeding has been banned in many countries because of increasing concerns about the development of bacterial resistance to antibiotics and potential issues on food safety. Searching for antibiotic substitutes is essential. Applying transgenerational epigenetic technology to animal production could be an alternative. Some environmental changes can be transferred to memory-like responses in the offspring through epigenetic mechanisms without changing the DNA sequence. In this paper, we reviewed those nutrients and non-nutritional additives that have transgenerational epigenetic effects, including some amino acids, vitamins, and polysaccharides. The paternal transgenerational nutritional epigenetic regulation was particularly focused on mechanism of the substantial contribution of male stud animals to the animal industries. We illustrated the effects of paternal transgenerational epigenetics on the metabolism and immunity in farming animals and proposed strategies to modulate male breeding livestock or poultry.

Low and high postpubertal ethanol use: damage on adulthood reproduction and offspring

Graphical abstract

Abstract

The relationship between adolescent ethanol uses and its impacts throughout life are not conclusive. Thus, we evaluated if the low and high consumption of ethanol at postpuberty interferes with the reproduction and ethanol-naive offspring and if the effects are dose-related. Female and male rats were divided into three groups: low drinker (L), high drinker (H) and control (C). The L and H groups were exposed to ethanol up to 10 % from 65 to 80 days with withdrawal after this period. The ethanol consumed by low drinkers was 1.41 ± 0.21 g/kg/day and by high drinkers 4.59 ± 0.45 g/kg/day. The study was conducted in two phases. The first phase verified the reproductive capacity in adulthood on generations (litter size and sex ratio). Data were collected over 10 years. The second phase analyzed the parent reproductive parameters (body weight, reproductive organ weight, sperm parameters and estrous cycle) and the pup development. We observed a reduced litter size in both drinker groups. Gestational body weight gain and feed consumption were lower in L and H. We observed an alteration in reproductive organs weight in both sexes of H. Females presented a longer estrous cycle duration. Males presented an increase in abnormal sperm, a decrease in sperm count and accelerated transit time. The ethanol-naive offspring development was also impaired. We conclude that low and high postpubertal alcohol use impairs long-term reproductive parameters, even after alcohol withdrawal. There is also impaired ethanol-naive offspring. Besides, the effects are dose-related.

Lay summary

The effects of alcohol use have been reported in several studies. However, better knowledge about early alcohol use and its impact on reproduction in adulthood, after abstinence and on ethanol-naive offspring could help improve preventive measures and mechanisms of action. One of the methods used was retrospective analysis which allows to evaluate the effects of postpubertal ethanol use on the reproductive capacity of rats over generations. Despite our limitations, we verified that the post-adolescent period acts as a susceptibility window, and lifestyle at this age modulates the long-term reproductive parameters. The early ethanol use impairs reproduction function since sperm parameters and the estrous cycle have been altered. The dose of alcohol also contributes to damage on the drinkers’ reproduction and on the physical development of ethanol-naive offspring. Future studies are necessary to identify the mechanism involved in long-term alcohol use effects, even in withdrawal, as well as ethanol-naive offspring outcomes.

Transgenerational Abnormalities Induced by Paternal Preconceptual Alcohol Drinking: Findings from Humans and Animal Models

Alcohol consumption during pregnancy and lactation is a widespread preventable cause of neurodevelopmental impairment in newborns. While the harmful effects of gestational alcohol use have been well documented, only recently, the role of paternal preconceptual alcohol consumption (PPAC) prior to copulating has drawn specific epigenetic considerations. Data from human and animal models have demonstrated that PPAC may affect sperm function, eliciting oxidative stress. In newborns, PPAC may induce changes in behavior, cognitive functions, and emotional responses. Furthermore, PPAC may elicit neurobiological disruptions, visuospatial impairments, hyperactivity disorders, motor skill disruptions, hearing loss, endocrine, and immune alterations, reduced physical growth, placental disruptions, and metabolic alterations. Neurobiological studies on PPAC have also disclosed changes in brain function and structure by disrupting the growth factors pathways. In particular, as shown in animal model studies, PPAC alters brain nerve growth factor (NGF) and brainderived neurotrophic factor (BDNF) synthesis and release. This review shows that the crucial topic of lifelong disabilities induced by PPAC and/or gestational alcohol drinking is quite challenging at the individual, societal, and familial levels. Since a nontoxic drinking behavior before pregnancy (for both men and women), during pregnancy, and lactation cannot be established, the only suggestion for couples planning pregnancies is to completely avoid the consumption of alcoholic beverages.

Transgenerational Effects of Prenatal Ethanol Exposure in Prepubescent Mice

Background: Fetal alcohol spectrum disorders (FASD) represent a leading cause of non-genetic neuropathologies. Recent preclinical evidence from suggests that prenatal ethanol exposure (PrEE), like other environmental exposures, may have a significant, transgenerational impact on the offspring of directly exposed animals, including altered neocortical development at birth and behavior in peri-pubescent mice. How these adverse behavioral outcomes are manifested within the brain at the time of behavioral disruption remains unknown.

Methods: A transgenerational mouse model of FASD was used to generate up to a third filial generation of offspring to study. Using a multi-modal battery of behavioral assays, we assessed motor coordination/function, sensorimotor processing, risk-taking behavior, and depressive-like behavior in postnatal day (P) 20 pre-pubescent mice. Additionally, sensory neocortical area connectivity using dye tracing, neocortical gene expression using in situ RNA hybridization, and spine density of spiny stellate cells in the somatosensory cortex using Golgi-Cox staining were examined in mice at P20.

Results: We found that PrEE induces behavioral abnormalities including abnormal sensorimotor processing, increased risk-taking behavior, and increased depressive-like behaviors that extend to the F3 generation in 20-day old mice. Assessment of both somatosensory and visual cortical connectivity, as well as cortical RZRβ expression in pre-pubescent mice yielded no significant differences among any experimental generations. In contrast, only directly-exposed F1 mice displayed altered cortical expression of Id2 and decreased spine density among layer IV spiny stellate cells in somatosensory cortex at this pre-pubescent, post weaning age.

Conclusion: Our results suggest that robust, clinically-relevant behavioral abnormalities are passed transgenerationally to the offspring of mice directly exposed to prenatal ethanol. Additionally, in contrast to our previous findings in the newborn PrEE mouse, a lack of transgenerational findings within the brain at this later age illuminates the critical need for future studies to attempt to discover the link between neurological function and the described behavioral changes. Overall, our study suggests that multi-generational effects of PrEE may have a substantial impact on human behavior as well as health and well-being and that these effects likely extend beyond early childhood.

Paternal alcohol consumption has intergenerational consequences in male offspring

PURPOSE

Alcoholism is a heterogeneous set of disorders caused by ethanol intake. Harmful effects of paternal consumption on the offspring are poorly explored and not fully understood. We analyzed the effect of paternal alcohol consumption on both their own reproductive capacity and that of their male offspring.

METHODS

We used a model of ethanol consumption (15% v/v in drinking water) for 12 days in adult CF-1 male mice. DNA integrity and post-translational modifications of histones were assessed in sperm; testicular weight, histology, and DNA fragmentation were analyzed. Treated or untreated male mice were mated with non-treated females to obtain two cell embryos that were cultured for 7 days; morphology and embryonic cell death were evaluated. Males of both groups were mated with non-treated females. Adult male offspring was euthanized, and sperm and testicular parameters determined.

RESULTS

Paternal ethanol consumption caused histological and epigenetic changes, as well as damage in DNA integrity in the testicular germline and sperm. These alterations gave rise to deleterious effects on embryonic development and to testicular and spermatic changes in the offspring.

CONCLUSION

This study provides critical information on reproductive disturbances brought about by paternal alcohol consumption and the profound impact these could have on the male progeny. The need to explore the effects of paternal alcohol consumption in detail and warn about the importance of controlling alcohol intake for the well-being of future generations should not be underscored.

Preconceptional paternal alcohol consumption and the risk of child behavioral problems: a prospective cohort study

Animal studies demonstrated that paternal alcohol exposure before conception increases the risk of adverse neurodevelopment in offspring, but limited evidence is known in humans. Based on Shanghai-Minhang Birth Cohort Study, we aimed to examine associations between preconceptional paternal alcohol consumption and child behavioral problems. Paternal alcohol consumption during the last 3 months before conception was obtained by maternal report. Children born to fathers who drank alcohol at least once a week were classified as exposed. Child behavioral problems were assessed using the Child Behavior Checklist (CBCL) at age of 2, 4, and 6. Negative binomial regression was used to estimate the rate ratio (RR) of CBCL raw scores in 796 offspring. The risks of rating scores on anxious/depressed were increased by 33% (RR 1.33, 95% CI 1.09, 1.61) and 37% (RR 1.37, 95% CI 1.02, 1.84) among boys in the exposed group at age of 4 and 6, respectively. We also found that risks of somatic complaints were increased by 18% (RR 1.18, 95%CI 1.00, 1.40) and 65% (RR 1.65, 95%CI 1.14, 2.38) among girls in the exposed group at age of 4 and 6. The increased risks of sleep problems (RR 1.25, 95% CI 1.00, 1.55) in girls at age 4, thought problems (RR 1.32, 95% CI 1.01, 1.73) in girls at age 6, rule-breaking behaviors (RR 1.35, 95% CI 1.09, 1.67) in boys at age 6 were also found. The risks of CBCL scores on anxious/depressed and sleep problems in girls at age 4, as well as the risks of somatic complaints and rule-breaking behaviors in boys at age 6 increased with the level of exposure to paternal alcohol consumption. Our findings provided preliminary evidence that preconceptional paternal alcohol consumption may increase risks of child behavioral problems.

Effects of paternal exposure to cigarette smoke on sperm DNA methylation and long-term metabolic syndrome in offspring

BACKGROUND

Although paternal exposure to cigarette smoke may contribute to obesity and metabolic syndrome in offspring, the underlying mechanisms remain uncertain.

METHODS

In the present study, we analyzed the sperm DNA-methylation profiles in tobacco-smoking normozoospermic (SN) men, non-tobacco-smoking normozoospermic (N) men, and non-smoking oligoasthenozoospermic (OA) men. Using a mouse model, we also analyzed global methylation and differentially methylated regions (DMRs) of the DLK1 gene in paternal spermatozoa and the livers of progeny. In addition, we quantified DLK1 expression, executed an intra-peritoneal glucose tolerance test (IPGTT), measured serum metabolites, and analyzed liver lipid accumulation in the F1 offspring.

RESULTS

Global sperm DNA-methylation levels were significantly elevated (p  < 0.05) in the SN group, and the methylation patterns were different among N, SN, and OA groups. Importantly, the methylation level of the DLK1 locus (cg11193865) was significantly elevated in the SN group compared to both N and OA groups (p  < 0.001). In the mouse model, the group exposed to cigarette smoke extract (CSE) exhibited a significantly higher global methylation DNA level in spermatozoa (p  < 0.001) and on the DMR sites of Dlk1 in 10-week-old male offspring (p  < 0.05), with a significant increase in Dlk1 expression in their livers (p  < 0.001). In addition, IPGTT and LDL levels were significantly altered (p  < 0.001), with elevated liver fat accumulation (p  < 0.05) in F1 offspring.

CONCLUSION

Paternal exposure to cigarette smoke led to increased global methylation of sperm DNA and alterations to the DMR of the DLK1 gene in the F1 generation, which may be inherited parentally and may perturb long-term metabolic function.

Paternal alcohol exposure reduces acquisition of operant alcohol self-administration and affects Bdnf DNA methylation in male and female offspring

Familial transmission of alcohol use disorder reflects genetic and environmental factors. Paternal alcohol exposure may affect rodent offspring via epigenetic modifications transmitted through the male germ line. While such exposure alters alcohol sensitivity in mouse offspring, no studies examined if it impacts the development of operant alcohol self-administration in rats. We exposed male (sires) Wistar rats to chronic intermittent ethanol in vapour chambers (16 h/day; 5 days/week) or to air for 6 weeks. Eight weeks later, rats were mated with alcohol-naive females. Adult alcohol- and control-sired F1 offspring were assessed in acquisition of alcohol self-administration in which increasing alcohol concentrations (2.5%, 5% and 10%, v/v) were delivered after one lever press (fixed ratio 1 or FR1). Prior to alcohol sessions, rats were trained to lever press for food delivery under an FR1 schedule of reinforcement. DNA methylation levels of the brain derived neurotrophic factor (Bdnf) gene were measured in sperm, nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) in sires and in offspring. Alcohol-exposed sires had lower Bdnf DNA methylation levels in NAc and greater methylation levels in mPFC. Although this pattern was not recapitulated in offspring, alcohol-sired offspring of both sexes did show aberrant Bdnf DNA methylation patterns compared to control-sired offspring. Alcohol-sired offspring self-administered less alcohol (5% and 10%) with no group differences in food responding. Results indicate that paternal alcohol exposure prior to conception protects against alcohol's initial reinforcing effects but the pattern of dysregulated Bdnf methylation in reward-related circuitry did not mimic changes seen in sires.

Exposure of parents to alcohol alters behavior of offspring in zebrafish

Alcoholism and alcohol abuse represent a significant medical and societal problem, and have been thoroughly investigated in humans as well as using animal models. A less well understood aspect of alcohol related disorders is the possible effect of this drug on offspring whose parents were exposed prior to conception. The zebrafish has been successfully employed in alcohol research, however, the effect of exposing the parents to alcohol before fertilization of the eggs on offspring has not been demonstrated in this species. In this proof of concept study, we attempt to address this hiatus. We exposed both adult male and female zebrafish to 0.0% (control) or 0.5% (vol/vol) alcohol chronically for 7 days, subsequently bred the fish within their respective treatment group, collected the fertilized eggs, allowed them to develop, and tested the behavior of free-swimming offspring at their age of 7-9 days post-fertilization. We conducted the analysis in two genetically distinct quasi-inbred strains of zebrafish, AB and TL. Although gross morphology and general activity of the fish appeared unaffected, we found significant behavioral alterations in offspring of alcohol exposed parents compared to offspring of control parents in both strains. These alterations included robustly increased duration and reduced frequency of immobility, increased turn angle, and increased intra-individual variance of turn angle in offspring of alcohol exposed parents in both strains. The mechanisms underlying these behavioral effects or whether the effects are due to exposure of the father, the mother, or both to alcohol are unknown. Nevertheless, our results now set the stage for future studies with zebrafish that will address these questions.

Nutrition and cognition across the lifetime: an overview on epigenetic mechanisms

The functioning of our brain depends on both genes and their interactions with environmental factors. The close link between genetics and environmental factors produces structural and functional cerebral changes early on in life. Understanding the weight of environmental factors in modulating neuroplasticity phenomena and cognitive functioning is relevant for potential interventions. Among these, nutrition plays a key role. In fact, the link between gut and brain (the gut-brain axis) is very close and begins in utero, since the Central Nervous System (CNS) and the Enteric Nervous System (ENS) originate from the same germ layer during the embryogenesis. Here, we investigate the epigenetic mechanisms induced by some nutrients on the cognitive functioning, which affect the cellular and molecular processes governing our cognitive functions. Furthermore, epigenetic phenomena can be positively affected by specific healthy nutrients from diet, with the possibility of preventing or modulating cognitive impairments. Specifically, we described the effects of several nutrients on diet-dependent epigenetic processes, in particular DNA methylation and histones post-translational modifications, and their potential role as therapeutic target, to describe how some forms of cognitive decline could be prevented or modulated from the early stages of life.

Paternal and/or maternal preconception-induced neurobehavioral teratogenicity in animal and human models

Prenatal insult exposure effects on the offspring, have and are still considered the main interest of most teratological studies, while paternal and maternal preconception effects have received relatively little interest. Once thought to be a myth, paternal exposure to insults leading to numerous detrimental effects in the offspring, has been confirmed on several occasions and is gaining increased attention. These effects could be demonstrated molecularly, biochemically and/or behaviorally. Different epigenetic mechanisms have been proposed for these effects to occur, including DNA methylation, histone modification and sperm RNA transmission. Paternal insult exposure has been shown to cause several neurobehavioral and developmental defects in the offspring. Findings on parental insult exposure effects on the progeny will be discussed in this review, with the main focus being on neurobehavioral effects after parental preconceptional exposure. The exposure to the insults induced long-lasting, mostly marked, defects. A few pioneering, prevention and reversal studies were published. Interestingly, most studies were conducted on paternal exposure and, at the present state of this field, on animal models. Clinical translation remains the subsequent challenge.

The Influence of Cross-Fostering on Alcohol Consumption and Depressive-Like Behaviors in HA and LA Mice: The Role of the Endogenous Opioid System

The development of alcohol dependence and depression is determined by various genetic and environmental factors. In the presented study, we used high analgesia (HA) and low analgesia (LA) mouse lines, characterized by different endogenous opioid system activity and divergent blood–brain barrier permeability, to determine the influence of cross-fostering of these lines raised by surrogate mothers on ethanol consumption and development of depressive-like behaviors. We also investigated ethanol drinking by biological parents or surrogate mothers. Furthermore, we investigated whether these parental changes would alter the effect of naloxone on ethanol intake and depressive-like behaviors in offspring. Our results reveal that cross-fostering of HA and LA raised by surrogate mothers has a greater impact on depressive-like behaviors than ethanol consumption. Ethanol intake by biological parents substantially affected depressive-like behaviors and ethanol consumption in offspring. Moreover, ethanol intake by biological parents or an adoptive mother modified the effect of naloxone on ethanol consumption and preference and depressive-like behaviors in the HA offspring only. Together, these results indicate that cross-fostering differentially affects the effect of naloxone on alcohol consumption and the development of depression.

The offspring of alcohol-exposed sires exhibit heightened ethanol intake and behavioral alterations in the elevated plus maze

Research suggests that addictive traits are indeed heritable, but very few preclinical studies have explored transgenerational effects of paternal alcohol exposure. The present study addressed this gap in knowledge. We explored whether offspring of ethanol-exposed sires would be more likely to accept ethanol than descendants of water-exposed and control sires. We also investigated whether the second generation of ethanol-exposed descendants would accept ethanol more than controls and were more or less likely to experience anxiety-like behavior in behavioral assessments. We exposed male rats to repeated binge doses of alcohol (4 g/kg/day across 8 days), water, or left them untreated and mated them with untreated females. We then bred the offspring of these rats to test transgenerational effects of paternal alcohol exposure. We tested 14-day-old offspring from the first and second filial generation for their acceptance of ethanol and water, and measured anxiety-like behavior in 38-day-old, second-generation offspring using an elevated plus maze. The results indicate that offspring of ethanol-exposed sires increase ethanol acceptance in the first generation compared to untreated controls, whereas in the second-generation increased ethanol acceptance vs. these controls is seen in descendants of both ethanol- and vehicle-treated sires. At adolescence, the second generation of rats derived from alcohol-exposed sires exhibited significantly more time spent in the open arms and significantly more arm entries than any other group. The present study suggests that parental ethanol exposure is associated with lingering effects in the infant and adolescent offspring. The second filial generation was also found to be affected, albeit similarly by grandparental ethanol exposure or by the stress of the vehicle administration.

Paternal exposure to exercise and/or caffeine and alcohol modify offspring behavioral and pathophysiological recovery from repetitive mild traumatic brain injury in adolescence

Only recently has the scope of parental research expanded to include the paternal sphere with epidemiological studies implicating stress, nutrition and alcohol consumption in the neurobiological and behavioral characteristics of offspring. This study was designed to determine if paternal exposure to caffeine, alcohol and exercise prior to conception would improve or exacerbate offspring recovery from adolescent repetitive mild traumatic brain injury (RmTBI). Sires received 7 weeks of standard drinking water, or caffeine and ethanol and were housed in regular cages or cages with running wheels, prior to being mated to control females. At postnatal day 40, offspring were administered RmTBI or sham injuries and were assessed for post concussive symptomology. Post-mortem quantitative real-time polymerase chain reaction (qRT-PCR) was used to assess gene expression in the prefrontal cortex (PFC), nucleus accumbens (NAc) and changes in telomere length. Additionally, enzyme-linked immunosorbent assay (ELISA's) were run on serum to detect levels of cytokines, chemokines and sex hormones. Paternal experience did not improve or exacerbate RmTBI behavioral outcomes. However, female and male offspring displayed unique responses to RmTBI and paternal experience, resulting in changes in physical, behavioral and molecular outcomes. Injury and paternal exercise modified changes in female offspring, whereas male offspring were affected by paternal exercise, caffeine and alcohol treatment. Additionally, paternal experience and RmTBI modified expression of many genes in the PFC, NAc, telomere length and levels of sex hormones. Although further exploration is required to understand the heterogeneity that exists in disease risk and resiliency, this study provides corroborating evidence that paternal experiences prior to conception influences offspring development.

Epigenetics of the developing and aging brain: Mechanisms that regulate onset and outcomes of brain reorganization

Brain development is a life-long process that encompasses several critical periods of transition, during which significant cognitive changes occur. Embryonic development, puberty, and reproductive senescence are all periods of transition that are hypersensitive to environmental factors. Rather than isolated episodes, each transition builds upon the last and is influenced by consequential changes that occur in the transition before it. Epigenetic marks, such as DNA methylation and histone modifications, provide mechanisms by which early events can influence development, cognition, and health outcomes. For example, parental environment influences imprinting patterns in gamete cells, which ultimately impacts gene expression in the embryo which may result in hypersensitivity to poor maternal nutrition during pregnancy, raising the risks for cognitive impairment later in life. This review explores how epigenetics induce and regulate critical periods, and also discusses how early environmental interactions prime a system towards a particular health outcome and influence susceptibility to disease or cognitive impairment throughout life.

Adolescent Substance Abuse, Transgenerational Consequences and Epigenetics

Adolescence is the transitional period between childhood and adulthood and a critical period in brain development. Adolescence in humans is also associated with increased expression of risk-taking behaviors. Epidemiological and clinical studies, for example, show a surge of drug abuse and raise the hypothesis that the adolescent brain undergoes critical changes resulting in diminished control. Determining how substance abuse during this critical period might cause longterm neurobiological changes in cognition and behavior is therefore critically important. The present work aims to provide an evaluation of the transgenerational and multi-generational phenotypes derived from parent animals exposed to drugs of abuse only during their adolescence. Specifically, we will consider changes found following the administration of cannabinoids, nicotine, alcohol and opiates. In addition, epigenetic modifications of the genome following drug exposure will be discussed as emerging evidence of the underlying adverse transgenerational effects. Notwithstanding, much of the new data discussed here is from animal models, indicating that future clinical studies are much needed to better understand the neurobiological consequences and mechanisms of drug actions on the human brains' development and maturation.

Epigenetic changes on rat chromosome 4 contribute to disparate alcohol drinking behavior in alcohol-preferring and -nonpreferring rats

BACKGROUND

Paternal alcohol abuse is a well-recognized risk factor for the development of an alcohol use disorder (AUD). In addition to genetic and environmental risk factors, heritable epigenetic factors also have been proposed to play a key role in the development of AUD. However, it is not clear whether epigenetic factors contribute to the genetic inheritance in families affected by AUD. We used reciprocal crosses of the alcohol-preferring (P) and -nonpreferring (NP) rat lines to test whether epigenetic factors also impacted alcohol drinking in up to two generations of offspring.

METHODS

F1 offspring derived by reciprocal breeding of P and NP rats were tested for differences in alcohol consumption using a free-choice protocol of 10% ethanol, 20% ethanol, and water that were available concurrently. In a separate experiment, an F2 population was tested for alcohol consumption not only due to genetic differences. These rats were generated from inbred P (iP) and iNP rat lines that were reciprocally bred to produce genetically identical F1 offspring that remained alcohol-naïve. Intercrosses of the F1 generation animals produced the F2 generation. Alcohol consumption was then assessed in the F2 generation using a standard two-bottle choice protocol, and was analyzed using genome-wide linkage analysis. Alcohol consumption measures were also analyzed for sex differences.

RESULTS

Average alcohol consumption was higher in the F1 offspring of P vs. NP sires and in the F2 offspring of F0 iP vs. iNP grandsires. Linkage analyses showed the maximum LOD scores for alcohol consumption in both male and female offspring were on chromosome 4 (Chr 4). The LOD score for both sexes considered together was higher when the grandsire was iP vs. iNP (5.0 vs. 3.35, respectively). Furthermore, the F2 population displayed enhanced alcohol consumption when the P alleles from the F0 sire were present.

CONCLUSIONS

These results demonstrate that epigenetic and/or non-genetic factors mapping to rat chromosome 4 contribute to a transgenerational paternal effect on alcohol consumption in the P and NP rat model of AUD.

Mapping the past, present and future research landscape of paternal effects

BACKGROUND

Although in all sexually reproducing organisms an individual has a mother and a father, non-genetic inheritance has been predominantly studied in mothers. Paternal effects have been far less frequently studied, until recently. In the last 5 years, research on environmentally induced paternal effects has grown rapidly in the number of publications and diversity of topics. Here, we provide an overview of this field using synthesis of evidence (systematic map) and influence (bibliometric analyses).

RESULTS

We find that motivations for studies into paternal effects are diverse. For example, from the ecological and evolutionary perspective, paternal effects are of interest as facilitators of response to environmental change and mediators of extended heredity. Medical researchers track how paternal pre-fertilization exposures to factors, such as diet or trauma, influence offspring health. Toxicologists look at the effects of toxins. We compare how these three research guilds design experiments in relation to objects of their studies: fathers, mothers and offspring. We highlight examples of research gaps, which, in turn, lead to future avenues of research.

CONCLUSIONS

The literature on paternal effects is large and disparate. Our study helps in fostering connections between areas of knowledge that develop in parallel, but which could benefit from the lateral transfer of concepts and methods.

Exposure to drugs of abuse induce effects that persist across generations

Substance use disorders are highly prevalent and continue to be one of the leading causes of disability in the world. Notably, not all people who use addictive drugs develop a substance use disorder. Although substance use disorders are highly heritable, patterns of inheritance cannot be explained purely by Mendelian genetic mechanisms. Vulnerability to developing drug addiction depends on the interplay between genetics and environment. Additionally, evidence from the past decade has pointed to the role of epigenetic inheritance in drug addiction. This emerging field focuses on how environmental perturbations, including exposure to addictive drugs, induce epigenetic modifications that are transmitted to the embryo at fertilization and modify developmental gene expression programs to ultimately impact subsequent generations. This chapter highlights intergenerational and transgenerational phenotypes in offspring following a history of parental drug exposure. Special attention is paid to parental preconception exposure studies of five drugs of abuse (alcohol, cocaine, nicotine, cannabinoids, and opiates) and associated behavioral and physiological outcomes in offspring. The highlighted studies demonstrate that parental exposure to drugs of abuse has enduring effects that persist into subsequent generations. Understanding the contribution of epigenetic inheritance in drug addiction may provide clues for better treatments and therapies for substance use disorders.

Effects of Paternal Preconception Vapor Alcohol Exposure Paradigms on Behavioral Responses in Offspring

We and others previously reported that paternal preconception chronic ethanol exposure leads to molecular, physiological, and behavioral changes in offspring including reduced ethanol consumption and preference relative to controls. The goal of the present study was to further explore the impact of paternal ethanol exposure on a wide variety of basal and drug-induced behavioral responses in first generation offspring. Adult male mice were exposed to chronic intermittent vapor ethanol or control conditions for 5-6 weeks before being mated with ethanol-naïve females to produce ethanol (E)- and control (C)-sired offspring. E-sired male offspring showed stress hyporesponsivity in a stress-induced hyperthermia assay and E-sired female offspring had reduced binge-like ethanol consumption in a drinking in the dark assay compared to C-sired offspring. E-sired offspring also showed altered sensitivity to a sedative/hypnotic dose of the GABAergic drug midazolam, but not ketamine or ethanol, in a loss of the righting response assay. E-sired offspring did not differ from controls in marble burying, novel object location, novel object recognition, social interaction, bottle-brush, novelty suppressed feeding, prepulse inhibition, every-other-day ethanol drinking, or home cage activity assays. This study adds to a growing body of literature suggesting that like in utero alcohol exposure, paternal preconception alcohol exposure can also have effects that persist and impact behavior of offspring.

Impact of nicotine, alcohol, and cocaine exposure on germline integrity and epigenome

Converging evidence suggests that parental exposure to drugs of abuse can affect offspring phenotypes. The impacts of drug abuse on germ cell quality may mediate multigenerational and transgenerational inheritance, although biological pathways underlying this mode of inheritance are not yet characterized. Germline epigenetic marks are modified by drug exposure and have emerged as promising mechanistic candidates in recent work. Drug exposure also impacts overall germline integrity and reproductive functioning, although the role of these consequences in multi/transgenerational inheritance is unclear. This review synthesizes literature on effects of exposure to alcohol, cocaine, and nicotine on the germline with a focus on epigenetic modifications following drug exposure and broader impacts on germline integrity and reproductive functioning. We discuss potential interactions between reproductive functioning, germline integrity, and germline epigenome/transcriptome in pathways underlying multi/transgenerational inheritance. We find that existing data may support independent or interactive contributions of these germline impacts on offspring phenotypes in a manner that may mediate multi/transgenerational inheritance.

The neural mechanisms and consequences of paternal caregiving

In recent decades, human sociocultural changes have increased the numbers of fathers that are involved in direct caregiving in Western societies. This trend has led to a resurgence of interest in understanding the mechanisms and effects of paternal care. Across the animal kingdom, paternal caregiving has been found to be a highly malleable phenomenon, presenting with great variability among and within species. The emergence of paternal behaviour in a male animal has been shown to be accompanied by substantial neural plasticity and to be shaped by previous and current caregiving experiences, maternal and infant stimuli and ecological conditions. Recent research has allowed us to gain a better understanding of the neural basis of mammalian paternal care, the genomic and circuit-level mechanisms underlying paternal behaviour and the ways in which the subcortical structures that support maternal caregiving have evolved into a global network of parental care. In addition, the behavioural, neural and molecular consequences of paternal caregiving for offspring are becoming increasingly apparent. Future cross-species research on the effects of absence of the father and the transmission of paternal influences across generations may allow research on the neuroscience of fatherhood to impact society at large in a number of important ways.

The Impact of Paternal Alcohol Consumption on Offspring Brain and Behavioral Development

BACKGROUND

Fetal alcohol spectrum disorders (FASD) describe the wide array of long-lasting developmental abnormalities in offspring due to prenatal alcohol (ethanol [EtOH]) exposure via maternal gestational drinking. Although the teratogenic consequences of prenatal EtOH exposure, are apparent, the effects of preconception paternal EtOH exposure (PatEE) are still unclear. Previous research suggests that PatEE can induce molecular changes and abnormal behavior in the offspring. However, it is not known whether PatEE impacts the development of the neocortex and behavior in offspring as demonstrated in maternal consumption models of FASD (J Neurosci, 33, 2013, 18893).

METHODS

In this study, we utilized a novel mouse model of PatEE where male mice self-administered 25% EtOH for an extended period prior to conception, generating indirect exposure to the offspring through the paternal germline. Following mating, we examined the effects of PatEE on offspring neocortical development at postnatal day (P) 0 and evaluated several aspects of behavior at both P20 and P30 using a battery of behavioral assays.

RESULTS

PatEE resulted in significant impact on neocortical development, including abnormal patterns of gene expression within the neocortex at P0 and subtle alterations in patterns of intraneocortical connections. Additionally, PatEE mice exhibited a sex-specific increase in activity and sensorimotor integration deficits at P20, and decreased balance, coordination, and short-term motor learning at P30. This suggests that PatEE may generate long-lasting, sex-specific effects on offspring behavior.

CONCLUSIONS

These results demonstrate that the developmental impact of preconception PatEE is more harmful than previously thought and provide additional insights into the biological mechanisms that may underlie atypical behavior observed in children of alcoholic fathers.

Association of Sperm Methylation at LINE-1, Four Candidate Genes, and Nicotine/Alcohol Exposure With the Risk of Infertility

In this study, we examined whether smoking and drinking affect sperm quality and the DNA methylation of the repetitive element LINE-1, MEST, P16, H19, and GNAS in sperm. Semen samples were obtained from 143 male residents in a minority-inhabited district of Guizhou province in southwest China. Quantitative DNA methylation analysis of the samples was performed using MassARRAY EpiTYPER assays. Sperm motility was significantly lower in both the nicotine-exposed (P = 0.0064) and the nicotine- and alcohol-exposed (P = 0.0008) groups. Follicle-stimulating hormone (FSH) levels were higher in the nicotine-exposed group (P = 0.0026). The repetitive element LINE-1 was hypermethylated in the three exposed groups, while P16 was hypomethylated in the alcohol and both the alcohol and nicotine exposure groups. Our results also show that alcohol and nicotine exposure altered sperm cell quality, which may be related to the methylation levels of MEST and GNAS. In addition, MEST, GNAS, and the repetitive element LINE1 methylation was significantly associated with the concentration of sperm as well as FSH and luteinizing hormone levels.

Paternal benzo[a]pyrene exposure alters the sperm DNA methylation levels of imprinting genes in F0 generation mice and their unexposed F1-2 male offspring

BACKGROUND

Benzo[a]pyrene (BaP) is an environmental pollutant known to cause teratogenesis. However, the mechanism underlying this teratogenic effect is not fully understood. Recently, the alteration of DNA methylation of imprinting genes has emerged as a specific epigenetic mechanism linking the impact of environmental pollutants on embryonic development to paternal exposures. The aim of this study was to investigate the transgenerational effects of paternal BaP exposure on the imprinting genes in mouse sperm DNA.

METHODS

Male C57BL/6J mice received BaP (1.0 or 2.5 mg/kg) or olive oil twice a week for 12 weeks. The methylation status of 6 imprinting genes (H19, Meg3, Peg1, Peg3, Igf2 and Snrpn) was examined by bisulfite pyrosequencing of the sperm DNA of BaP-exposed F0 generation and their offspring.

RESULTS

BaP exposure reduced the methylation levels in the imprinting genes H19 and Meg3 and increased the methylation levels of Peg1 and Peg3; however, no significant differences was observed for the methylation levels of Igf2 or Snrpn in the sperm DNA. Furthermore, BaP-exposed male mice were mated with unexposed female mice to generate F1-2 generations. The methylation levels of the 6 genes in the sperm DNA from F1-2 offspring showed a similar pattern as that of the F0 male. The effects were attenuated in F1-2 generations.

CONCLUSIONS

Paternal BaP exposure altered the methylation levels of imprinting genes, implicating that imprinting genes are susceptible to environmental toxicants. Furthermore, a similar alteration was observed in the F1-2 generations although the attenuated in methylation in F2 generation, revealing a potential transgenerational effect.

Who's your daddy? Behavioral and epigenetic consequences of paternal drug exposure

Substance use disorders (SUDs) reflect genetic and environmental factors. While identifying reliable genetic variants that predispose individuals to developing SUDs has been challenging, epigenetic factors may also contribute to the heritability of SUDs. Familial drug use associates with a wide range of problems in children, including an increased risk for developing a SUD. The implications of maternal drug use on offspring development are a well-studied area; however, paternal drug use prior to conception has received relatively little attention. Paternal exposure to several environmental stimuli (i.e. stress or diet manipulations) results in behavioral and epigenetic changes in offspring. The purpose of this review is to determine the state of the preclinical literature on the behavioral and epigenetic consequences of paternal drug exposure. Drug-sired offspring show several developmental and physiological abnormalities. These offspring also show deficits in cognitive and emotional domains. Examining sensitivity to drugs in offspring is a growing area of research. Drug-sired offspring are resistant to the rewarding and reinforcing properties of drugs. However, greater paternal motivation for the drug, combined with high drug intake, can result in addiction-like behaviors in offspring. Drug-sired offspring also show altered histone modifications and DNA methylation levels of imprinted genes and microRNAs; epigenetic-mediated changes were also noted in genes related to glutamatergic and neurotrophic factor signaling. In some instances, drug use resulted in aberrant epigenetic modifications in sire sperm, and these changes were maintained in the brains of offspring. Thus, paternal drug exposure has long-lasting consequences that include altered drug sensitivity in subsequent generations. We discuss factors (i.e. maternal behaviors) that may moderate these paternal drug-induced effects as well as ideas for future directions.

Intergenerational Effects of Alcohol: A Review of Paternal Preconception Ethanol Exposure Studies and Epigenetic Mechanisms in the Male Germline

While alcohol use disorder (AUD) is a highly heritable psychiatric disease, efforts to elucidate that heritability by examining genetic variation (e.g., single nucleotide polymorphisms) have been insufficient to fully account for familial AUD risk. Perhaps not coincidently, there has been a burgeoning interest in novel nongenomic mechanisms of inheritance (i.e., epigenetics) that are shaped in the male or female germ cells by significant lifetime experiences such as exposure to chronic stress, malnutrition, or drugs of abuse. While many epidemiological and preclinical studies have long pointed to a role for the parental preconception environment in offspring behavior, over the last decade many studies have implicated a causal relationship between the environmentally sensitive sperm epigenome and intergenerational phenotypes. This critical review will detail the heritable effects of alcohol and the potential role for epigenetics.

Offspring of male rats exposed to binge alcohol exhibit heightened ethanol intake at infancy and alterations in T-maze performance

Alcohol use is associated with a variety of negative consequences, including heightened likelihood of cognitive impairment, proclivity to alcohol use disorders (AUD), and alterations in the drinker's offspring. Children and rodents exposed to alcohol during pregnancy, or those whose fathers consumed alcohol prior to mating, often exhibit neurodevelopmental, physiological, and behavioral deficits. The present study assessed cognitive function and alcohol intake in male and female rats that were offspring of alcohol-exposed fathers. Adult male rats were exposed to alcohol or vehicle (0.0 or 2.0 g/kg, respectively; twice daily for 2 days followed by a rest day, for a total of eight alcohol or vehicle exposure days), or were left untreated and then mated with non-manipulated females. The offspring were assessed for alcohol intake, via intraoral infusion, followed by cognitive assessment via an alternating T-maze task. The results indicated that paternal ethanol exposure, prior to breeding, resulted in offspring that consumed significantly more ethanol than vehicle or untreated controls. Furthermore, the offspring of alcohol-exposed fathers exhibited a significant failure to initiate and complete the T-maze performance tests. Although, when they did engage in the tests they performed at the level of controls (i.e., 80% correct). The present results add to a growing body of literature suggesting that paternal pre-conception alcohol exposure can have deleterious effects on the offspring.

Epigenetic effects of paternal cocaine on reward stimulus behavior and accumbens gene expression in mice

Paternal cocaine use causes phenotypic alterations in offspring behavior and associated neural processing. In rodents, changes in first generation (F1) offspring include drug reward behavior, circadian timing, and anxiety responses. This study, utilizing a murine (C57BL/6J) oral cocaine model, examines the effects of paternal cocaine exposure on fundamental characteristics of offspring reward responses, including: 1) the extent of cocaine-induced effects after different durations of sire drug withdrawal; 2) sex- and drug-dependent differences in F1 reward preference; 3) effects on second generation (F2) cocaine preference; and 4) corresponding changes in reward area (nucleus accumbens) mRNA expression. We demonstrate that paternal cocaine intake over a single ˜40-day spermatogenic cycle significantly decreased cocaine (but not ethanol or sucrose) preference in a sex-specific manner in F1 mice from sires mated 24 h after drug withdrawal. However, F1 offspring of sires bred 4 months after withdrawal did not exhibit altered cocaine preference. Altered cocaine preference also was not observed in F2's. RNASeq analyses of F1 accumbens tissue revealed changes in gene expression in male offspring of cocaine-exposed sires, including many genes not previously linked to cocaine addiction. Enrichment analyses highlight genes linked to CNS development, synaptic signaling, extracellular matrix, and immune function. Expression correlation analyses identified a novel target, Fam19a4, that may negatively regulate many genes in the accumbens, including genes already identified in addiction. Collectively, these results reveal that paternal cocaine effects in F1 offspring may involve temporally limited epigenetic germline effects and identify new genetic targets for addiction research.

Paternal Preconception Every-Other-Day Ethanol Drinking Alters Behavior and Ethanol Consumption in Offspring

Alcohol use disorder is a devastating disease with a complex etiology. Recent preclinical studies have revealed that paternal preconception chronic intermittent ethanol (EtOH) exposure via vaporized EtOH altered drinking behaviors and sensitivity to EtOH selectively in male offspring. In the current study, we used a voluntary oral route of paternal preconception EtOH exposure, i.e., intermittent every-other-day two-bottle choice drinking, and tested offspring for behavioral alterations. Fifteen EtOH drinking sires and 10 control sires were mated to EtOH naïve females to produce EtOH-sired and control-sired offspring. These offspring were tested using the elevated plus maze, open field, drinking in the dark, and unlimited access two-bottle choice assays. We found that paternal preconception every-other-day two-bottle choice drinking resulted in reduced EtOH consumption selectively in male offspring in the drinking in the dark assay compared to control-sired offspring. No differences were detected in either sex in the unlimited access two-bottle choice and elevated plus maze assays. Open field analysis revealed complex changes in basal behavior and EtOH-induced behaviors that were sex specific. We concluded that paternal preconception voluntary EtOH consumption has persistent effects that impact the next generation. This study adds to a growing appreciation that one’s behavioral response to EtOH and EtOH drinking behavior are impacted by EtOH exposure of the prior generation.

Imprinting methylation in SNRPN and MEST1 in adult blood predicts cognitive ability

Genomic imprinting is important for normal brain development and aberrant imprinting has been associated with impaired cognition. We studied the imprinting status in selected imprints (H19, IGF2, SNRPN, PEG3, MEST1, NESPAS, KvDMR, IG-DMR and ZAC1) by pyrosequencing in blood samples from longitudinal cohorts born in 1936 (n = 485) and 1921 (n = 223), and anterior hippocampus, posterior hippocampus, periventricular white matter, and thalamus from brains donated to the Aberdeen Brain Bank (n = 4). MEST1 imprint methylation was related to childhood cognitive ability score (-0.416 95% CI -0.792,-0.041; p = 0.030), with the strongest effect evident in males (-0.929 95% CI -1.531,-0.326; p = 0.003). SNRPN imprint methylation was also related to childhood cognitive ability (+0.335 95%CI 0.008,0.663; p = 0.045). A significant association was also observed for SNRPN methylation and adult crystallised cognitive ability (+0.262 95%CI 0.007,0.517; p = 0.044). Further testing of significant findings in a second cohort from the same region, but born in 1921, resulted in similar effect sizes and greater significance when the cohorts were combined (MEST1; -0.371 95% CI -0.677,-0.065; p = 0.017; SNRPN; +0.361 95% CI 0.079,0.643; p = 0.012). For SNRPN and MEST1 and four other imprints the methylation levels in blood and in the five brain regions were similar. Methylation of the paternally expressed, maternally methylated genes SNRPN and MEST1 in adult blood was associated with cognitive ability in childhood. This is consistent with the known importance of the SNRPN containing 15q11-q13 and the MEST1 containing 7q31-34 regions in cognitive function. These findings, and their sex specific nature in MEST1, point to new mechanisms through which complex phenotypes such as cognitive ability may be inherited. These mechanisms are potentially relevant to both the heritable and non-heritable components of cognitive ability. The process of epigenetic imprinting—within SNRPN and MEST1 in particular—and the factors that influence it, are worthy of further study in relation to the determinants of cognitive ability.

Imprinting methylation in SNRPN and MEST1 in adult blood predicts cognitive ability

Genomic imprinting is important for normal brain development and aberrant imprinting has been associated with impaired cognition. We studied the imprinting status in selected imprints (H19, IGF2, SNRPN, PEG3, MEST1, NESPAS, KvDMR, IG-DMR and ZAC1) by pyrosequencing in blood samples from longitudinal cohorts born in 1936 (n = 485) and 1921 (n = 223), and anterior hippocampus, posterior hippocampus, periventricular white matter, and thalamus from brains donated to the Aberdeen Brain Bank (n = 4). MEST1 imprint methylation was related to childhood cognitive ability score (-0.416 95% CI -0.792,-0.041; p = 0.030), with the strongest effect evident in males (-0.929 95% CI -1.531,-0.326; p = 0.003). SNRPN imprint methylation was also related to childhood cognitive ability (+0.335 95%CI 0.008,0.663; p = 0.045). A significant association was also observed for SNRPN methylation and adult crystallised cognitive ability (+0.262 95%CI 0.007,0.517; p = 0.044). Further testing of significant findings in a second cohort from the same region, but born in 1921, resulted in similar effect sizes and greater significance when the cohorts were combined (MEST1; -0.371 95% CI -0.677,-0.065; p = 0.017; SNRPN; +0.361 95% CI 0.079,0.643; p = 0.012). For SNRPN and MEST1 and four other imprints the methylation levels in blood and in the five brain regions were similar. Methylation of the paternally expressed, maternally methylated genes SNRPN and MEST1 in adult blood was associated with cognitive ability in childhood. This is consistent with the known importance of the SNRPN containing 15q11-q13 and the MEST1 containing 7q31-34 regions in cognitive function. These findings, and their sex specific nature in MEST1, point to new mechanisms through which complex phenotypes such as cognitive ability may be inherited. These mechanisms are potentially relevant to both the heritable and non-heritable components of cognitive ability. The process of epigenetic imprinting-within SNRPN and MEST1 in particular-and the factors that influence it, are worthy of further study in relation to the determinants of cognitive ability.

Epigenetic Transgenerational Inheritance

Epigenetic information refers to heritable changes in gene expression that occur without modifications at the DNA sequence level. These changes are orchestrated by different epigenetic mechanisms such as DNA methylation, posttranslational modifications of histones, and the presence of noncoding RNAs. Epigenetic information regulates chromatin structure to confer cell-specific gene expression.The sperm epigenome is the result of three periods of global resetting during men's life. Germ cell epigenome reprogramming is designed to allow cell totipotency and to prevent the transmission of epimutations via spermatozoa. At the end of these reprogramming events, the sperm epigenome has a very specific epigenetic pattern that is a footprint of past reprogramming events and has an influence on embryo development.Several data demonstrate that not all regions of the epigenome are erased during the reprogramming periods, suggesting the transmission of epigenetic information from fathers to offspring via spermatozoa. Moreover, it is becoming increasingly clear that the sperm epigenome is sensitive to environmental factors during the process of gamete differentiation, suggesting the plasticity of the sperm epigenetic signature according to the circumstances of the individual's life.In this chapter, we provided strong evidences about the association between variations of the sperm epigenome and the exposure to environmental factors. Moreover, we will present data about how epigenetic mechanisms are candidates for transferring paternal environmental information to offspring.