Early prenatal stress epigenetically programs dysmasculinization in second-generation offspring via the paternal lineage

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.

Immune Alterations in the Intrauterine Environment Shape Offspring Brain Development in a Sex-Specific Manner

Exposure to immune dysregulation in utero or in early life has been shown to increase risk for neuropsychiatric illness. The sources of inflammation can be varied, including acute exposures due to maternal infection or acute stress, or persistent exposures due to chronic stress, obesity, malnutrition, or autoimmune diseases. These exposures may cause subtle alteration in brain development, structure, and function that can become progressively magnified across the life span, potentially increasing the likelihood of developing a neuropsychiatric conditions. There is some evidence that males are more susceptible to early-life inflammatory challenges than females. In this review, we discuss the various sources of in utero or early-life immune alteration and the known effects on fetal development with a sex-specific lens. To do so, we leveraged neuroimaging, behavioral, cellular, and neurochemical findings. Gaining clarity about how the intrauterine environment affects offspring development is critically important for informing preventive and early intervention measures that may buffer against the effects of these early-life risk factors.

Sex-Biased Expression and Response of microRNAs in Neurological Diseases and Neurotrauma

Neurological diseases and neurotrauma manifest significant sex differences in prevalence, progression, outcome, and therapeutic responses. Genetic predisposition, sex hormones, inflammation, and environmental exposures are among many physiological and pathological factors that impact the sex disparity in neurological diseases. MicroRNAs (miRNAs) are a powerful class of gene expression regulator that are extensively involved in mediating biological pathways. Emerging evidence demonstrates that miRNAs play a crucial role in the sex dimorphism observed in various human diseases, including neurological diseases. Understanding the sex differences in miRNA expression and response is believed to have important implications for assessing the risk of neurological disease, defining therapeutic intervention strategies, and advancing both basic research and clinical investigations. However, there is limited research exploring the extent to which miRNAs contribute to the sex disparities observed in various neurological diseases. Here, we review the current state of knowledge related to the sexual dimorphism in miRNAs in neurological diseases and neurotrauma research. We also discuss how sex chromosomes may contribute to the miRNA sexual dimorphism phenomenon. We attempt to emphasize the significance of sexual dimorphism in miRNA biology in human diseases and to advocate a gender/sex-balanced science.

Epigenetic inheritance of phenotypes associated with parental exposure to cocaine

Parental exposure to drugs of abuse induces changes in the germline that can be transmitted across subsequent generations, resulting in enduring effects on gene expression and behavior. This transgenerational inheritance involves a dynamic interplay of environmental, genetic, and epigenetic factors that impact an individual's vulnerability to neuropsychiatric disorders. This chapter aims to summarize recent research into the mechanisms underlying the inheritance of gene expression and phenotypic patterns associated with exposure to drugs of abuse, with an emphasis on cocaine. We will first define the epigenetic modifications such as DNA methylation, histone post-translational modifications, and expression of non-coding RNAs that are impacted by parental cocaine use. We will then explore how parental cocaine use induces heritable epigenetic changes that are linked to alterations in neural circuitry and synaptic plasticity within reward-related circuits, ultimately giving rise to potential behavioral vulnerabilities. This discussion will consider phenotypic differences associated with gestational as well as both maternal and paternal preconception drug exposure and will emphasize differences based on offspring sex. In this context, we explore the complex interactions between genetics, epigenetics, environment, and biological sex. Overall, this chapter consolidates the latest developments in the multigenerational effects and long-term consequences of parental substance abuse.

Cross-Talk between miRNAs from the Dlk1-Dio3 Locus and Histone Methylation to Protect Male Cerebellum from Methyl Donor Deficiency

SCOPE

Disruption of the one carbon metabolism during development, i.e., following a gestational vitamin B9 and B12 deficiencies, is involved in birth defects and brain development delay. Using a rat nutritional model, consisting of pups born to dams fed a vitamin B9 and B12 deficient diet (MDD), the study previously reports molecular and cellular alterations in the brain, in a sex dependent manner, with females being more affected than males. The study hypothesizes that epigenetic modifications could participate in the sex differences is observed.

METHODS AND RESULTS

The study investigates lysine methylation of histones and expression of microRNAs in the cerebellum of MDD male and female pups. The study reports a differential regulation of H3K36Me2 and H4K20Me3 between males and females, in response to MDD. Moreover, distinct regulation of Kmt5b and Kdm2a expression by miR-134-5p and miR-369-5p from the Dlk1-Dio3 locus, contributes to the maintenance of expression of genes involved in synaptic plasticity.

CONCLUSION

These results could explain the neuroprotection to MDD that male pups display. The work will contribute to the understanding of the consequences of vitamin starvation on brain development, as well as how the epigenome is affected by one carbon metabolism disruption.

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.

Sex-biased gene and microRNA expression in the developing mouse brain is associated with neurodevelopmental functions and neurological phenotypes

BACKGROUND

Sex differences pose a challenge and an opportunity in biomedical research. Understanding how sex chromosomes and hormones affect disease-causing mechanisms will shed light on the mechanisms underlying predominantly idiopathic sex-biased neurodevelopmental disorders such as ADHD, schizophrenia, and autism. Gene expression is a crucial conduit for the influence of sex on developmental processes; therefore, this study focused on sex differences in gene expression and the regulation of gene expression. The increasing interest in microRNAs (miRNAs), small, non-coding RNAs, for their contribution to normal and pathological neurodevelopment prompted us to test how miRNA expression differs between the sexes in the developing brain.

METHODS

High-throughput sequencing approaches were used to identify transcripts, including miRNAs, that showed significantly different expression between male and female brains on day 15.5 of development (E15.5).

RESULTS

Robust sex differences were identified for some genes and miRNAs, confirming the influence of biological sex on RNA. Many miRNAs that exhibit the greatest differences between males and females have established roles in neurodevelopment, implying that sex-biased expression may drive sex differences in developmental processes. In addition to highlighting sex differences for individual miRNAs, gene ontology analysis suggested several broad categories in which sex-biased RNAs might act to establish sex differences in the embryonic mouse brain. Finally, mining publicly available SNP data indicated that some sex-biased miRNAs reside near the genomic regions associated with neurodevelopmental disorders.

CONCLUSIONS

Together, these findings reinforce the importance of cataloguing sex differences in molecular biology research and highlight genes, miRNAs, and pathways of interest that may be important for sexual differentiation in the mouse and possibly the human brain.

Paternal morphine exposure in rats reduces social play in adolescent male progeny without affecting drug-taking behavior in juvenile males or female offspring

The ongoing opioid addiction crisis necessitates the identification of novel risk factors to improve prevention and treatment of opioid use disorder. Parental opioid exposure has recently emerged as a potential regulator of offspring vulnerability to opioid misuse, in addition to heritable genetic liability. An understudied aspect of this "missing heritability" is the developmental presentation of these cross-generational phenotypes. This is an especially relevant question in the context of inherited addiction-related phenotypes, given the prominent role of developmental processes in the etiology of psychiatric disorders. Paternal morphine self-administration was previously shown to alter the sensitivity to the reinforcing and antinociceptive properties of opioids in the next generation. Here, phenotyping was expanded to include the adolescent period, with a focus on endophenotypes related to opioid use disorders and pain. Paternal morphine exposure did not alter heroin or cocaine self-administration in male and female juvenile progeny. Further, baseline sensory reflexes related to pain were unaltered in morphine-sired adolescent rats of either sex. However, morphine-sired adolescent males exhibited a reduction in social play behavior. Our findings suggest that, in morphine-sired male offspring, paternal opioid exposure does not affect opioid intake during adolescence, suggesting that this phenotype does not emerge until later in life. Altered social behaviors in male morphine-sired adolescents indicate that the changes in drug-taking behavior in adults sired by morphine-exposed sires may be due to more complex factors not yet fully assessed.

The long-term gut bacterial signature of a wild primate is associated with a timing effect of pre- and postnatal maternal glucocorticoid levels

BACKGROUND

During development, elevated levels of maternal glucocorticoids (GCs) can have detrimental effects on offspring morphology, cognition, and behavior as well as physiology and metabolism. Depending on the timing of exposure, such effects may vary in strength or even reverse in direction, may alleviate with age, or may concern more stable and long-term programming of phenotypic traits. Maternal effects on gut bacterial diversity, composition, and function, and the persistence of such effects into adulthood of long-lived model species in the natural habitats remain underexplored.

RESULTS

In a cross-sectional sample of infant, juvenile, and adult Assamese macaques, the timing of exposure to elevated maternal GCs during ontogeny was associated with the gut bacterial community of the offspring. Specifically, naturally varying maternal GC levels during early but not late gestation or lactation were associated with reduced bacterial richness. The overall effect of maternal GCs during early gestation on the gut bacterial composition and function exacerbated with offspring age and was 10 times stronger than the effect associated with exposure during late prenatal or postnatal periods. Instead, variation in maternal GCs during the late prenatal or postnatal period had less pronounced or less stable statistical effects and therefore a weaker effect on the entire bacterial community composition, particularly in adult individuals. Finally, higher early prenatal GCs were associated with an increase in the relative abundance of several potential pro-inflammatory bacteria and a decrease in the abundance of Bifidobacterium and other anti-inflammatory taxa, an effect that exacerbated with age.

CONCLUSIONS

In primates, the gut microbiota can be shaped by developmental effects with strong timing effects on plasticity and potentially detrimental consequences for adult health. Together with results on other macaque species, this study suggests potential detrimental developmental effects similar to rapid inflammaging, suggesting that prenatal exposure to high maternal GC concentrations is a common cause underlying both phenomena. Our findings await confirmation by metagenomic functional and causal analyses and by longitudinal studies of long-lived, ecologically flexible primates in their natural habitat, including developmental effects that originate before birth. Video Abstract.

Social deficits in mice prenatally exposed to valproic acid are intergenerationally inherited and rescued by social enrichment

Intergenerational transmission of the effects of environmental factors on brain function and behavior can occur through epigenetic mechanisms. Valproic acid (VPA) is an anticonvulsant drug that, when administered during pregnancy, causes various birth defects. The mechanisms of action are largely unclear: VPA can reduce neuronal excitability, but it also inhibits the histone deacetylases, affecting gene expression. Here we evaluated whether the effects of valproic acid prenatal exposure on autism spectrum disorder (ASD)-related behavioral phenotypes can be transmitted to the second generation (F2) through the paternal or the maternal lineage. Indeed, we found that F2 males of the VPA pedigree show reduced sociability, which can be rescued by exposing the animals to social enrichment. Moreover, as is the case for F1 males, F2 VPA males show increased c-Fos expression in the piriform cortex. However, F3 males show normal sociability, indicating that VPA's effects on this behavior are not transgenerationally inherited. Female behavior is not affected by VPA exposure, and we found no evidence of maternal transmission of the consequences of this pharmacological treatment. Finally, all animals exposed to VPA and their descendants show reduced body weight, highlighting an intriguing effect of this compound on metabolism. We propose the VPA model of ASD as a valuable mouse model to study the role of epigenetic inheritance and its underlying mechanisms affecting behavior and neuronal function.

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.

Maternal adverse childhood experiences impact fetal adrenal volume in a sex-specific manner

BACKGROUND

The mechanisms by which parental early life stress can be transmitted to the next generation, in some cases in a sex-specific manner, are unclear. Maternal preconception stress may increase susceptibility to suboptimal health outcomes via in utero programming of the fetal hypothalamic-pituitary-adrenal (HPA) axis.

METHODS

We recruited healthy pregnant women (N = 147), dichotomized into low (0 or 1) and high (2+) adverse childhood experience (ACE) groups based on the ACE Questionnaire, to test the hypothesis that maternal ACE history influences fetal adrenal development in a sex-specific manner. At a mean (standard deviation) of 21.5 (1.4) and 29.5 (1.4) weeks gestation, participants underwent three-dimensional ultrasounds to measure fetal adrenal volume, adjusting for fetal body weight (_waFAV).

RESULTS

At ultrasound 1, _waFAV was smaller in high versus low ACE males (b = - 0.17; z = - 3.75; p < .001), but females did not differ significantly by maternal ACE group (b = 0.09; z = 1.72; p = .086). Compared to low ACE males, _waFAV was smaller for low (b = - 0.20; z = - 4.10; p < .001) and high ACE females (b = - 0.11; z = 2.16; p = .031); however, high ACE males did not differ from low (b = 0.03; z = .57; p = .570) or high ACE females (b = - 0.06; z = - 1.29; p = .196). At ultrasound 2, _waFAV did not differ significantly between any maternal ACE/offspring sex subgroups (ps ≥ .055). Perceived stress did not differ between maternal ACE groups at baseline, ultrasound 1, or ultrasound 2 (ps ≥ .148).

CONCLUSIONS

We observed a significant impact of high maternal ACE history on _waFAV, a proxy for fetal adrenal development, but only in males. Our observation that the _waFAV in males of mothers with a high ACE history did not differ from the _waFAV of females extends preclinical research demonstrating a dysmasculinizing effect of gestational stress on a range of offspring outcomes. Future studies investigating intergenerational transmission of stress should consider the influence of maternal preconception stress on offspring outcomes.

Potential Regulation of miRNA-29 and miRNA-9 by Estrogens in Neurodegenerative Disorders: An Insightful Perspective

Finding a link between a hormone and microRNAs (miRNAs) is of great importance since it enables the adjustment of genetic composition or cellular functions without needing gene-level interventions. The dicer-mediated cleavage of precursor miRNAs is an interface link between miRNA and its regulators; any disruption in this process can affect neurogenesis. Besides, the hormonal regulation of miRNAs can occur at the molecular and cellular levels, both directly, through binding to the promoter elements of miRNAs, and indirectly, via regulation of the signaling effects of the post-transcriptional processing proteins. Estrogenic hormones have many roles in regulating miRNAs in the brain. This review discusses miRNAs, their detailed biogenesis, activities, and both the general and estrogen-dependent regulations. Additionally, we highlight the relationship between miR-29, miR-9, and estrogens in the nervous system. Such a relationship could be a possible etiological route for developing various neurodegenerative disorders.

Paternal morphine exposure enhances morphine self-administration and induces region-specific neural adaptations in reward-related brain regions of male offspring

Background

A growing body of preclinical studies report that preconceptional experiences can have a profound and long-lasting impact on adult offspring behavior and physiology. However, less is known about paternal drug exposure and its effects on reward sensitivity in the next generation.

Methods

Adult male rats self-administered morphine for 65 days; controls received saline. Sires were bred to drug-naïve dams to produce first-generation (F1) offspring. Morphine, cocaine, and nicotine self-administration were measured in adult F1 progeny. Molecular correlates of addiction-like behaviors were measured in reward-related brain regions of drug naïve F1 offspring.

Results

Male, but not female offspring produced by morphine-exposed sires exhibited dose-dependent increased morphine self-administration and increased motivation to earn morphine infusions under a progressive ratio schedule of reinforcement. This phenotype was drug-specific as self-administration of cocaine, nicotine, and sucrose were not altered by paternal morphine history. The male offspring of morphine-exposed sires also had increased expression of mu-opioid receptors in the ventral tegmental area but not in the nucleus accumbens.

Conclusions

Paternal morphine exposure increased morphine addiction-like behavioral vulnerability in male but not female progeny. This phenotype is likely driven by long-lasting neural adaptations within the reward neural brain pathways.

Sex bias in lymphocytes: Implications for autoimmune diseases

Autoimmune diseases are characterized by a significant sex dimorphism, with women showing increased susceptibility to disease. This is, at least in part, due to sex-dependent differences in the immune system that are influenced by the complex interplay between sex hormones and sex chromosomes, with contribution from sociological factors, diet and gut microbiota. Sex differences are evident in the number and function of lymphocyte populations. Women mount a stronger pro-inflammatory response than males, with increased lymphocyte proliferation, activation and pro-inflammatory cytokine production, whereas men display expanded regulatory cell subsets. Ageing alters the immune landscape of men and women in differing ways, resulting in changes in autoimmune disease susceptibility. Here we review the current literature on sex differences in lymphocyte function, the factors that influence this, and the implications for autoimmune disease. We propose that improved understanding of sex bias in lymphocyte function can provide sex-specific tailoring of treatment strategies for better management of autoimmune diseases.

Beyond Genes: Germline Disruption in the Etiology of Autism Spectrum Disorders

Investigations into the etiology of autism spectrum disorders have been largely confined to two realms: variations in DNA sequence and somatic developmental exposures. Here we suggest a third route-disruption of the germline epigenome induced by exogenous toxicants during a parent's gamete development. Similar to cases of germline mutation, these molecular perturbations may produce dysregulated transcription of brain-related genes during fetal and early development, resulting in abnormal neurobehavioral phenotypes in offspring. Many types of exposures may have these impacts, and here we discuss examples of anesthetic gases, tobacco components, synthetic steroids, and valproic acid. Alterations in parental germline could help explain some unsolved phenomena of autism, including increased prevalence, missing heritability, skewed sex ratio, and heterogeneity of neurobiology and behavior.

The Role of Transposable Elements in Sexual Development

Up to 50% of most mammalian genomes are made up of transposable elements (TEs) that have the potential to mobilize around the genome. Despite this prevalence, research on TEs is only beginning to gain traction within the field of neuroscience. While TEs have long been regarded as “junk” or parasitic DNA, it has become evident that they are adaptive DNA and RNA regulatory elements. In addition to their vital role in normal development, TEs can also interact with steroid receptors, which are key elements to sexual development. In this review, we provide an overview of the involvement of TEs in processes related to sexual development- from TE activity in the germline to TE accumulation in sex chromosomes. Moreover, we highlight sex differences in TE activity and their regulation of genes related to sexual development. Finally, we speculate on the epigenetic mechanisms that may govern TEs’ role in sexual development. In this context, we emphasize the need to further the understanding of sexual development through the lens of TEs including in a variety of organs at different developmental stages, their molecular networks, and evolution.

Migration modulates the prevalence of ASD and ADHD: a systematic review and meta-analysis

BACKGROUND

Migration has been implicated as a risk factor for autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), but evidence is still limited and inconsistent. We aim to investigate the relationship between migration status and risk of ASD and ADHD.

METHODS

Electronic databases including PubMed, EMBASE, Web of Science, and PsychINFO were searched to identify observational studies on this topic, from inception to February 2021. Random-effects meta-analysis models were used to pool the summary odds ratio (OR) and 95% confidence interval (95% CI), and subgroup analyses were conducted to detect possible discrepancies in associations. Certainty of evidence was assessed as per the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) guidelines.

RESULTS

A total of 13 studies (6,532,546 participants) for ASD, five studies (2,875,070 participants) for ADHD, and six studies (31,158 participants) for hyperactivity were included. Overall, the pooled results indicated that migration was associated with increased risk of ASD (pooled OR: 1.32; 95% CI: 1.07-1.63; P for Z test = 0.010), but no association was found between migration and ADHD (pooled OR: 0.84; 95% CI: 0.53-1.32; P for Z test = 0.452) or hyperactivity (pooled standardized mean difference: -0.073; 95% CIs: - 0.383-0.236; P for Z test = 0.642). Subgroup analyses further demonstrated that maternal migration was ASD risk factor (pooled OR: 1.49; 95% CI: 1.19-1.87), and migrant children were more likely to develop ASD with comorbid intellectual disability (ID) (pooled OR: 1.21, P for interaction = 0.006) than ASD without ID. After standardized the origin of migrants, European migrant children from Americas were at higher risk of ASD and ADHD (pooled OR were 4.13 and 1.26), and increased ASD risk was also observed in African children (pooled OR: 2.72). The GRADE of evidence was very low.

CONCLUSIONS

Maternal migration is a risk factor for ASD, and migrant ASD children are more likely comorbid ID. The role of migration on ADHD remains controversial, more studies are needed to assess the association between migration status and ADHD. Health care practitioners should consider screening and providing extra resources for migrant children.

Early programming of reproductive health and fertility: novel neuroendocrine mechanisms and implications in reproductive medicine

BACKGROUND

According to the Developmental Origins of Health and Disease (DOHaD) hypothesis, environmental changes taking place during early maturational periods may alter normal development and predispose to the occurrence of diverse pathologies later in life. Indeed, adverse conditions during these critical developmental windows of high plasticity have been reported to alter the offspring developmental trajectory, causing permanent functional and structural perturbations that in the long term may enhance disease susceptibility. However, while solid evidence has documented that fluctuations in environmental factors, ranging from nutrient availability to chemicals, in early developmental stages (including the peri-conceptional period) have discernible programming effects that increase vulnerability to develop metabolic perturbations, the impact and eventual mechanisms involved, of such developmental alterations on the reproductive phenotype of offspring have received less attention.

OBJECTIVE AND RATIONALE

This review will summarize recent advances in basic and clinical research that support the concept of DOHaD in the context of the impact of nutritional and hormonal perturbations, occurring during the periconceptional, fetal and early postnatal stages, on different aspects of reproductive function in both sexes. Special emphasis will be given to the effects of early nutritional stress on the timing of puberty and adult gonadotropic function, and to address the underlying neuroendocrine pathways, with particular attention to involvement of the Kiss1 system in these reproductive perturbations. The implications of such phenomena in terms of reproductive medicine will also be considered.

SEARCH METHODS

A comprehensive MEDLINE search, using PubMed as main interface, of research articles and reviews, published mainly between 2006 and 2021, has been carried out. Search was implemented using multiple terms, focusing on clinical and preclinical data from DOHaD studies, addressing periconceptional, gestational and perinatal programming of reproduction. Selected studies addressing early programming of metabolic function have also been considered, when relevant.

OUTCOMES

A solid body of evidence, from clinical and preclinical studies, has documented the impact of nutritional and hormonal fluctuations during the periconceptional, prenatal and early postnatal periods on pubertal maturation, as well as adult gonadotropic function and fertility. Furthermore, exposure to environmental chemicals, such as bisphenol A, and maternal stress has been shown to negatively influence pubertal development and gonadotropic function in adulthood. The underlying neuroendocrine pathways and mechanisms involved have been also addressed, mainly by preclinical studies, which have identified an, as yet incomplete, array of molecular and neurohormonal effectors. These include, prominently, epigenetic regulatory mechanisms and the hypothalamic Kiss1 system, which likely contribute to the generation of reproductive alterations in conditions of early nutritional and/or metabolic stress. In addition to the Kiss1 system, other major hypothalamic regulators of GnRH neurosecretion, such as γ-aminobutyric acid and glutamate, may be targets of developmental programming.

WIDER IMPLICATIONS

This review addresses an underdeveloped area of reproductive biology and medicine that may help to improve our understanding of human reproductive disorders and stresses the importance, and eventual pathogenic impact, of early determinants of puberty, adult reproductive function and fertility.

Translating the Transcriptome: Sex Differences in the Mechanisms of Depression and Stress, Revisited

The past decade has produced a plethora of studies examining sex differences in the transcriptional profiles of stress and mood disorders. As we move forward from accepting the existence of extensive molecular sex differences in the brain to exploring the purpose of these sex differences, our approach must become more systemic and less reductionist. Earlier studies have examined specific brain regions and/or cell types. To use this knowledge to develop the next generation of personalized medicine, we need to comprehend how transcriptional changes across the brain and/or the body relate to each other. We provide an overview of the relationships between baseline and depression/stress-related transcriptional sex differences and explore contributions of preclinically identified mechanisms and their impacts on behavior.

Epigenetic mechanisms impacted by chronic stress across the rodent lifespan

Exposures to stress at all stages of development can lead to long-term behavioural effects, in part through changes in the epigenome. This review describes rodent research suggesting that stress in prenatal, postnatal, adolescent and adult stages leads to long-term changes in epigenetic regulation in the brain which have causal impacts on rodent behaviour. We focus on stress-induced epigenetic changes that have been linked to behavioural deficits including poor learning and memory, and increased anxiety-like and depressive-like behaviours. Interestingly, aspects of these stress-induced behavioural changes can be transmitted to offspring across several generations, a phenomenon that has been proposed to result via epigenetic mechanisms in the germline. Here, we also discuss evidence for the differential impact of stress on the epigenome in males and females, conscious of the fact that the majority of published studies have only investigated males. This has led to a limited picture of the epigenetic impact of stress, highlighting the need for future studies to investigate females as well as males.

Age-associated changes in microRNAs affect the differentiation potential of human mesenchymal stem cells: Novel role of miR-29b-1-5p expression

Age-associated osteoporosis is widely accepted as involving the disruption of osteogenic stem cell populations and their functioning. Maintenance of the local bone marrow (BM) microenvironment is critical for regulating proliferation and differentiation of the multipotent BM mesenchymal stromal/stem cell (BMSC) population with age. The potential role of microRNAs (miRNAs) in modulating BMSCs and the BM microenvironment has recently gained attention. However, miRNAs expressed in rapidly isolated BMSCs that are naïve to the non-physiologic standard tissue culture conditions and reflect a more accurate in vivo profile have not yet been reported. Here we directly isolated CD271 positive (+) BMSCs within hours from human surgical BM aspirates without culturing and performed microarray analysis to identify the age-associated changes in BMSC miRNA expression. One hundred and two miRNAs showed differential expression with aging. Target prediction and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that the up-regulated miRNAs targeting genes in bone development pathways were considerably enriched. Among the differentially up-regulated miRNAs the novel passenger strand miR-29b-1-5p was abundantly expressed as a mature functional miRNA with aging. This suggests a critical arm-switching mechanism regulates the expression of the miR-29b-1-5p/3p pair shifting the normally degraded arm, miR-29b-1-5p, to be the dominantly expressed miRNA of the pair in aging. The normal guide strand miR-29b-1-3p is known to act as a pro-osteogenic miRNA. On the other hand, overexpression of the passenger strand miR-29b-1-5p in culture-expanded CD271+ BMSCs significantly down-regulated the expression of stromal cell-derived factor 1 (CXCL12)/ C-X-C chemokine receptor type 4 (SDF-1(CXCL12)/CXCR4) axis and other osteogenic genes including bone morphogenetic protein-2 (BMP-2) and runt-related transcription factor 2 (RUNX2). In contrast, blocking of miR-29b-1-5p function using an antagomir inhibitor up-regulated expression of BMP-2 and RUNX2 genes. Functional assays confirmed that miR-29b-1-5p negatively regulates BMSC osteogenesis in vitro. These novel findings provide evidence of a pathogenic anti-osteogenic role for miR-29b-1-5p and other miRNAs in age-related defects in osteogenesis and bone regeneration.

Single paternal dexamethasone challenge programs offspring metabolism and reveals multiple candidates in RNA-mediated inheritance

Single traumatic events that elicit an exaggerated stress response can lead to the development of neuropsychiatric conditions. Rodent studies suggested germline RNA as a mediator of effects of chronic environmental exposures to the progeny. The effects of an acute paternal stress exposure on the germline and their potential consequences on offspring remain to be seen. We find that acute administration of an agonist for the stress-sensitive Glucocorticoid receptor, using the common corticosteroid dexamethasone, affects the RNA payload of mature sperm as soon as 3 hr after exposure. It further impacts early embryonic transcriptional trajectories, as determined by single-embryo sequencing, and metabolism in the offspring. We show persistent regulation of tRNA fragments in sperm and descendant 2-cell embryos, suggesting transmission from sperm to embryo. Lastly, we unravel environmentally induced alterations in sperm circRNAs and their targets in the early embryo, highlighting this class as an additional candidate in RNA-mediated inheritance of disease risk.

The potential role of stress and sex steroids in heritable effects of sevoflurane

Most surgical procedures require general anesthesia, which is a reversible deep sedation state lacking all perception. The induction of this state is possible because of complex molecular and neuronal network actions of general anesthetics (GAs) and other pharmacological agents. Laboratory and clinical studies indicate that the effects of GAs may not be completely reversible upon anesthesia withdrawal. The long-term neurocognitive effects of GAs, especially when administered at the extremes of ages, are an increasingly recognized health concern and the subject of extensive laboratory and clinical research. Initial studies in rodents suggest that the adverse effects of GAs, whose actions involve enhancement of GABA type A receptor activity (GABAergic GAs), can also extend to future unexposed offspring. Importantly, experimental findings show that GABAergic GAs may induce heritable effects when administered from the early postnatal period to at least young adulthood, covering nearly all age groups that may have children after exposure to anesthesia. More studies are needed to understand when and how the clinical use of GAs in a large and growing population of patients can result in lower resilience to diseases in the even larger population of their unexposed offspring. This minireview is focused on the authors' published results and data in the literature supporting the notion that GABAergic GAs, in particular sevoflurane, may upregulate systemic levels of stress and sex steroids and alter expressions of genes that are essential for the functioning of these steroid systems. The authors hypothesize that stress and sex steroids are involved in the mediation of sex-specific heritable effects of sevoflurane.

Maternal stress programs a demasculinization of glutamatergic transmission in stress-related brain regions of aged rats

Brain aging may be programmed by early-life stress. Aging affects males and females differently, but how perinatal stress (PRS) affects brain aging between sexes is unknown. We showed behavioral and neurobiological sex differences in non-stressed control rats that were strongly reduced or inverted in PRS rats. In particular, PRS decreased risk-taking behavior, spatial memory, exploratory behavior, and fine motor behavior in male aged rats. In contrast, female aged PRS rats displayed only increased risk-taking behavior and reduced exploratory behavior. PRS induced large reductions in the expression of glutamate receptors in the ventral and dorsal hippocampus and prefrontal cortex only in male rats. PRS also reduced the expression of synaptic vesicle-associated proteins, glucocorticoid receptors (GR), and mineralocorticoid receptors (MR) in the ventral hippocampus of aged male rats. In contrast, in female aged rats, PRS enhanced the expression of MRs and brain-derived neurotrophic factor (BDNF) in the ventral hippocampus and the expression of glial fibrillary acidic protein (GFAP) and BDNF in the prefrontal cortex. A common PRS effect in both sexes was a reduction in exploratory behavior and metabotropic glutamate (mGlu2/3) receptors in the ventral hippocampus and prefrontal cortex. A multidimensional analysis revealed that PRS induced a demasculinization profile in glutamate-related proteins in the ventral and dorsal hippocampus and prefrontal cortex, as well as a demasculinization profile of stress markers only in the dorsal hippocampus. In contrast, defeminization was observed only in the ventral hippocampus. Measurements of testosterone and 17-β-estradiol in the plasma and aromatase in the dorsal hippocampus were consistent with a demasculinizing action of PRS. These findings confirm that the brains of males and females differentially respond to PRS and aging suggesting that females might be more protected against early stress and age-related inflammation and neurodegeneration. Taken together, these results may contribute to understanding how early environmental factors shape vulnerability to brain aging in both sexes and may lay the groundwork for future studies aimed at identifying new treatment strategies to improve the quality of life of older individuals, which is of particular interest given that there is a high growth of aging in populations around the world.

Childhood trauma and insulin-like growth factors in amniotic fluid: An exploratory analysis of 79 women

BACKGROUND

Perinatal stress has adverse effects on fetal outcome, yet the effect of early maternal trauma on fetal outcome has scarcely been studied. We investigated effects of maternal childhood trauma and current environment on important regulators of prenatal growth, fetal insulin-like growth factor (IGF)-1 and IGF-2 in amniotic fluid and assessed the impact of IGFs on newborn anthropometrics.

METHODS

79 pregnant women in their second trimester who underwent amniocentesis (15.9 ± 0.9 weeks of gestational age) and their newborns at birth were analyzed. Maternal childhood trauma was assessed using the childhood trauma questionnaire (CTQ) and current environment was operationalized by assessing maternal psychosocial, physical health and endocrine measurements in amniotic fluid.

RESULTS

In this exploratory analysis of 79 pregnant women, maternal childhood trauma, defined as reporting at least low scores on any of the CTQ subscales, negatively correlated with fetal IGF-1 (M_ln = 3.48 vs. 2.98; p = 0.012) and IGF-2 (Mdn_ln = 4.99 vs. 4.70; p = 0.002). Trauma severity, defined as the overall trauma score, negatively correlated with fetal IGF-2 (r = -0.24; p = 0.037). From trauma subscales, maternal sexual abuse correlated with fetal IGF-1 (r = -0.32; p = 0.006) and IGF-2 (r = -0.39; p = 0.001). Maternal BMI negatively correlated with fetal IGF-1 (r = -0.26; p = 0.023) and IGF-2 (r = -0.29; p = 0.011). Newborn anthropometrics were operationalized by length, weight, sex, gestational age, length/gestational age and weight/gestational age at birth. Fetal weight at birth associated with a trend with fetal IGF-1 when controlling for BMI. Maternal hypothalamus-pituitary-adrenal axis activity and maternal exercise did not contribute significantly to predicting fetal IGFs. Maternal childhood trauma (β = -0.27; p = 0.011) and BMI (β = -0.24; p = 0.026) remained significantly associated with fetal IGF-1. Maternal childhood trauma (β = -0.32; p = 0.003), maternal BMI (β = -0.30; p = 0.005) and maternal sexual abuse (β = -0.22; p = 0.049) remained significantly associated with fetal IGF-2 and with a trend with fetal IGF-1 (β = -0.21; p = 0.076) when excluding women with gestational diabetes.

CONCLUSION

Maternal childhood trauma and BMI associate negatively with fetal IGF-1 and IGF-2 in amniotic fluid. Controlling for maternal BMI, fetal weight at birth remains associated with a trend with fetal IGF-1. The presented data suggests that childhood trauma can affect endocrine measurements of the developing next generation, providing a mechanism by which adverse maternal life events are transmitted to the next generation.

Biological Timing and Neurodevelopmental Disorders: A Role for Circadian Dysfunction in Autism Spectrum Disorders

Autism spectrum disorders (ASDs) are a spectrum of neurodevelopmental disorders characterized by impaired social interaction and communication, as well as stereotyped and repetitive behaviors. ASDs affect nearly 2% of the United States child population and the worldwide prevalence has dramatically increased in recent years. The etiology is not clear but ASD is thought to be caused by a combination of intrinsic and extrinsic factors. Circadian rhythms are the ∼24 h rhythms driven by the endogenous biological clock, and they are found in a variety of physiological processes. Growing evidence from basic and clinical studies suggest that the dysfunction of the circadian timing system may be associated with ASD and its pathogenesis. Here we review the findings that link circadian dysfunctions to ASD in both experimental and clinical studies. We first introduce the organization of the circadian system and ASD. Next, we review physiological indicators of circadian rhythms that are found disrupted in ASD individuals, including sleep-wake cycles, melatonin, cortisol, and serotonin. Finally, we review evidence in epidemiology, human genetics, and biochemistry that indicates underlying associations between circadian regulation and the pathogenesis of ASD. In conclusion, we propose that understanding the functional importance of the circadian clock in normal and aberrant neurodevelopmental processes may provide a novel perspective to tackle ASD, and clinical treatments for ASD individuals should comprise an integrative approach considering the dynamics of daily rhythms in physical, mental, and social processes.

Intergenerational trauma is associated with expression alterations in glucocorticoid- and immune-related genes

Offspring of trauma survivors are more likely to develop PTSD, mood, and anxiety disorders and demonstrate endocrine and molecular alterations compared to controls. This study reports the association between parental Holocaust exposure and genome-wide gene expression in peripheral blood mononuclear cells (PBMC) from 77 Holocaust survivor offspring and 15 comparison subjects. Forty-two differentially expressed genes (DEGs) were identified in association with parental Holocaust exposure (FDR-adjusted p < 0.05); most of these genes were downregulated and co-expressed in a gene network related to immune cell functions. When both parental Holocaust exposure and maternal age at Holocaust exposure shared DEGs, fold changes were in the opposite direction. Similarly, fold changes of shared DEGs associated with maternal PTSD and paternal PTSD were in opposite directions, while fold changes of shared DEGs associated with both maternal and paternal Holocaust exposure or associated with both maternal and paternal age at Holocaust exposure were in the same direction. Moreover, the DEGs associated with parental Holocaust exposure were enriched for glucocorticoid-regulated genes and immune pathways with some of these genes mediating the effects of parental Holocaust exposure on C-reactive protein. The top gene across all analyses was MMP8, encoding the matrix metalloproteinase 8, which is a regulator of innate immunity. To conclude, this study identified a set of glucocorticoid and immune-related genes in association with parental Holocaust exposure with differential effects based on parental exposure-related factors.

Epigenetic Mechanisms of Paternal Stress in Offspring Development and Diseases

The major biological function of the sperm cell is to transmit the paternal genetic and epigenetic information to the embryo as well as the following offspring. Sperm has a unique epigenome. An increasing body of epidemiological study supports that paternal stress induced by environmental exposures and lifestyle can modulate the sperm epigenome (including histone modification, DNA methylation, and noncoding RNA expression), sperm-egg fusion, embryo development, and offspring health. Based on the existing literature, we have summarized the paternal exposure on sperm epigenome along with the representative phenotypes of offspring and the possible mechanism involved.

Infant circulating MicroRNAs as biomarkers of effect in fetal alcohol spectrum disorders

Prenatal alcohol exposure (PAE) can result in cognitive and behavioral disabilities and growth deficits. Because alcohol-related neurobehavioral deficits may occur in the absence of overt dysmorphic features or growth deficits, there is a need to identify biomarkers of PAE that can predict neurobehavioral impairment. In this study, we assessed infant plasma extracellular, circulating miRNAs (exmiRNAs) obtained from a heavily exposed Cape Town cohort to determine whether these can be used to predict PAE-related growth restriction and cognitive impairment. PAE, controlling for smoking as a covariate, altered 27% of expressed exmiRNAs with clinically-relevant effect sizes (Cohen's d ≥ 0.4). Moreover, at 2 weeks, PAE increased correlated expression of exmiRNAs across chromosomes, suggesting potential co-regulation. In confirmatory factor analysis, the variance in expression for PAE-altered exmiRNAs at 2 weeks and 6.5 months was best described by three-factor models. Pathway analysis found that factors at 2 weeks were associated with (F1) cell maturation, cell cycle inhibition, and somatic growth, (F2) cell survival, apoptosis, cardiac development, and metabolism, and (F3) cell proliferation, skeletal development, hematopoiesis, and inflammation, and at 6.5 months with (F1) neurodevelopment, neural crest/mesoderm-derivative development and growth, (F2) immune system and inflammation, and (F3) somatic growth and cardiovascular development. Factors F3 at 2 weeks and F2 at 6.5 months partially mediated PAE-induced growth deficits, and factor F3 at 2 weeks partially mediated effects of PAE on infant recognition memory at 6.5 months. These findings indicate that infant exmiRNAs can help identify infants who will exhibit PAE-related deficits in growth and cognition.

Paternal Biomass Smoke Exposure in Rats Produces Behavioral and Cognitive Alterations in the Offspring

Particular concern at the present stage is the health effects of wildfires’ smoke. The aim of the study was to determine the impact of paternal biomass-smoke exposure on offspring’s behavior and cognitive abilities. Male rats were exposed to biomass smoke for four hours/day, five days/week, for four weeks. Average concentration of carbon monoxide and particulate matter of 2.5 μm PM_2.5 in the chamber during exposure were 28.7 ± 5.3 mg/m³ and 1.9 ± 0.5 mg/m³, respectively. At the same time, high concentrations of furfural and acetaldehyde were detected in the air environment of the exposure chambers. Offspring was obtained by mating of experimental males with untreated females, immediately after the end of the exposure and after 60 days (long-term period). Offspring were tested by using the Morris water maze and open field at three months of age. Male and female offspring born by mating immediately after exposure demonstrated decreased exploratory behavior, locomotor activity, and spatial navigation, as well as increased anxiety levels. Locomotor and exploratory activity in rats of both sexes from progeny obtained after long-term exposure to smoke had no statistically significant differences when compared to the control; however, the females showed a high level of anxiety and impaired cognitive functions. The recovery period after biomass-smoke intoxication, comparable in duration of spermatogenesis in rats, was an important factor in reducing the risk of developing central nervous system (CNS) disorders in offspring.

The effects of early life stress on motivated behaviors: A role for gonadal hormones

Motivated behaviors are controlled by the mesocorticolimbic dopamine (DA) system, consisting of projections from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) and prefrontal cortex (PFC), with input from structures including the medial preoptic area (mPOA). Sex differences are present in this circuit, and gonadal hormones (e.g., estradiol and testosterone) are important for regulating DA transmission. Early life stress (ELS) also regulates the mesocorticolimbic DA system. ELS modifies motivated behaviors and the underlying DA circuitry, increasing risk for disorders such as substance use disorder, major depression, and schizophrenia. ELS has been shown to change gonadal hormone signaling in both sexes. Thus, one way that ELS could impact mesocorticolimbic DA is by altering the efficacy of gonadal hormones. This review provides evidence for this idea by integrating the gonadal hormone, motivation, and ELS literature to argue that ELS alters gonadal hormone signaling to impact motivated behavior. We also discuss the importance of these effects in the context of understanding risk and treatments for psychiatric disorders in men and women.

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.

Environmental epigenetics of sex differences in the brain

Experiences throughout the life course lead to unique phenotypes even among those with the same genotype. Genotype sets the substrate on which physiologic processes, which communicate with the brain, mediate the effects of life experiences via epigenetics. Epigenetics modify the expression of genes in the brain and body in response to circulating hormones and other mediators, which are activated to facilitate survival responses through a process called allostasis. Epigenetic signatures can even be inherited, resulting in transgenerational effects. This chapter addresses epigenetics in the context of sex differences, discussing the intersection between genetics and gonadal hormones and their effect in the brain at discrete developmental periods.

Prenatal stress induced chromatin remodeling and risk of psychopathology in adulthood

New insights into the pathophysiology of psychiatric disorders suggest the existence of a complex interplay between genetics and environment. This notion is supported by evidence suggesting that exposure to stress during pregnancy exerts profound effects on the neurodevelopment and behavior of the offspring and predisposes them to psychiatric disorders later in life. Accumulated evidence suggests that vulnerability to psychiatric disorders may result from permanent negative effects of long-term changes in synaptic plasticity due to altered epigenetic mechanisms (histone modifications and DNA methylation) that lead to condensed chromatin architecture, thereby decreasing the expression of candidate genes during early brain development. In this chapter, we have summarized the literature of clinical studies on psychiatric disorders induced by maternal stress during pregnancy. We also discussed the epigenetic alterations of gene regulations induced by prenatal stress. Because the clinical manifestations of psychiatric disorders are complex, it is obvious that the biological progression of these diseases cannot be studied only in postmortem brains of patients and the use of animal models is required. Therefore, in this chapter, we have introduced a well-established mouse model of prenatal stress (PRS) generated in restrained pregnant dams. The behavioral phenotypes of the offspring (PRS mice) born to the stressed dam and underlying epigenetic changes in key molecules related to synaptic activity were described and highlighted. PRS mice may serve as a useful model for investigating the pathogenesis of psychiatric disorders and may be a useful tool for screening for the potential compounds that may normalize aberrant epigenetic mechanisms induced by prenatal stress.

Critical period regulation across multiple timescales

Brain plasticity is dynamically regulated across the life span, peaking during windows of early life. Typically assessed in the physiological range of milliseconds (real time), these trajectories are also influenced on the longer timescales of developmental time (nurture) and evolutionary time (nature), which shape neural architectures that support plasticity. Properly sequenced critical periods of circuit refinement build up complex cognitive functions, such as language, from more primary modalities. Here, we consider recent progress in the biological basis of critical periods as a unifying rubric for understanding plasticity across multiple timescales. Notably, the maturation of parvalbumin-positive (PV) inhibitory neurons is pivotal. These fast-spiking cells generate gamma oscillations associated with critical period plasticity, are sensitive to circadian gene manipulation, emerge at different rates across brain regions, acquire perineuronal nets with age, and may be influenced by epigenetic factors over generations. These features provide further novel insight into the impact of early adversity and neurodevelopmental risk factors for mental disorders.

Premigration social adversity and autism spectrum disorder

BACKGROUND

Several studies suggest significant relationships between migration and autism spectrum disorder (ASD) but there are discrepant results. Given that no studies to date have included a pathological control group, the specificity of the results in ASD can be questioned.

AIMS

To compare the migration experience (premigration, migratory trip, postmigration) in ASD and non-ASD pathological control groups, and study the relationships between migration and autism severity.

METHOD

Parents' and grandparents' migrant status was compared in 30 prepubertal boys with ASD and 30 prepubertal boys without ASD but with language disorders, using a questionnaire including Human Development Index (HDI)/Inequality-adjusted Human Development Index (IHDI) of native countries. Autism severity was assessed using the Child Autism Rating Scale, Autism Diagnostic Observation Schedule and Autism Diagnostic Interview-Revised scales.

RESULTS

The parents' and grandparents' migrant status frequency did not differ between ASD and control groups and was not associated with autism severity. The HDI/IHDI values of native countries were significantly lower for parents and grandparents of children with ASD compared with the controls, especially for paternal grandparents. Furthermore, HDI/IDHI levels from the paternal line (father and especially paternal grandparents) were significantly negatively correlated with autism severity, particularly for social interaction impairments.

CONCLUSIONS

In this study, parents' and/or grandparents' migrant status did not discriminate ASD and pathological control groups and did not contribute either to autism severity. However, the HDI/IHDI results suggest that social adversity-related stress experienced in native countries, especially by paternal grandparents, is potentially a traumatic experience that may play a role in ASD development. A 'premigration theory of autism' is then proposed.

Sexual partner preference in animals and humans

Sex differences in brain and behavior of animals including humans result from an interaction between biological and environmental influences. This is also true for the differences between men and women concerning sexual orientation. Sexual differentiation is mediated by three groups of biological mechanisms: early actions of sex steroids, more direct actions of sex-specific genes not mediated by gonadal sex steroids and epigenetic mechanisms. Differential interactions with parents and conspecifics have additionally long-term influences on behavior. This presentation reviews available evidence indicating that these different mechanisms play a significant role in the control of sexual partner preference in animals and humans, in other words the homosexual versus heterosexual orientation. Clinical and epidemiological studies of phenotypically selected populations indicate that early actions of hormones and genetic factors clearly contribute to the determination of sexual orientation. The maternal embryonic environment also modifies the incidence of male homosexuality via immunological mechanisms. The relative contribution of each of these mechanisms remains however to be determined.

Early life lessons: The lasting effects of germline epigenetic information on organismal development

BACKGROUND

An organism's metabolic phenotype is primarily affected by its genotype, its lifestyle, and the nutritional composition of its food supply. In addition, it is now clear from studies in many different species that ancestral environments can also modulate metabolism in at least one to two generations of offspring.

SCOPE OF REVIEW

We limit ourselves here to paternal effects in mammals, primarily focusing on studies performed in inbred rodent models. Although hundreds of studies link paternal diets and offspring metabolism, the mechanistic basis by which epigenetic information in sperm programs nutrient handling in the next generation remains mysterious. Our goal in this review is to provide a brief overview of paternal effect paradigms and the germline epigenome. We then pivot to exploring one key mystery in this literature: how do epigenetic changes in sperm, most of which are likely to act transiently in the early embryo, ultimately direct a long-lasting physiological response in offspring?

MAJOR CONCLUSIONS

Several potential mechanisms exist by which transient epigenetic modifications, such as small RNAs or methylation states erased shortly after fertilization, could be transferred to more durable heritable information. A detailed mechanistic understanding of this process will provide deep insights into early development, and could be of great relevance for human health and disease.

Transient Administration of Dopaminergic Precursor Causes Inheritable Overfeeding Behavior in Young Drosophila melanogaster Adults

Imbalances in dopaminergic signaling during development have been indicated as part of the underlying neurobiology of several psychiatric illnesses, including schizophrenia, major depression, bipolar disorder, and food addiction. Yet, how transient manipulation of dopaminergic signaling influences long-lasting behavioral consequences, or if these modifications can induce inheritable traits, it is still not understood. In this study, we used the Drosophila melanogaster model to test if transient pharmacological activation of the dopaminergic system leads to modulations of feeding and locomotion in adult flies. We observed that transient administration of a dopaminergic precursor, levodopa, at 6 h, 3 days or 5 days post-eclosion, induced overfeeding behavior, while we did not find significant effects on locomotion. Moreover, this phenotype was inherited by the offspring of flies treated 6 h or 3 days post-eclosion, but not the offspring of those treated 5 days post-eclosion. These results indicate that transient alterations in dopaminergic signaling can produce behavioral alterations in adults, which can then be carried to descendants. These findings provide novel insights into the conditions in which environmental factors can produce transgenerational eating disorders.

The effects of early life adversity on growth, maturation, and steroid hormones in male and female rats

Early life adversity is a risk factor for psychiatric disorders, yet the mechanisms by which adversity increases this risk are still being delineated. Here, we used a limited bedding and nesting (LBN) manipulation in rats that models a low resource environment to examine effects on growth, developmental milestones, and endocrine endpoints. In LBN, dams and pups, from pups' postnatal days 2-9, are exposed to an environment where dams lack proper materials to build a nest. This manipulation is compared to control housing conditions, where rat dams have access to ample nesting materials and enrichment throughout pups' development. We found that the LBN condition altered maternal care, increasing pup-directed behaviors while reducing self-care. This, perhaps compensatory, increase in nursing and attention to pups did not mitigate against changes in metabolism, as LBN reduced weight gain in both sexes and this effect persisted into adulthood. Although adult stress hormone levels in both sexes and vaginal opening and estrous cycle length in females were not disrupted, there was other evidence of endocrine dysregulation. Compared to controls, LBN rats of both sexes had shortened anogenital distances, indicating reduced androgen exposure. LBN males also had higher plasma estradiol levels in adulthood. This combination of results suggests that LBN causes a demasculinizing effect in males that could contribute to lasting changes in the brain and behavior. Importantly, alterations in metabolic and endocrine systems due to early life adversity could be one mechanism by which stress early in life increases risk for later disease.

Advanced paternal age as a risk factor for neurodevelopmental disorders: a translational study

Advanced paternal age (APA) is a risk factor for several neurodevelopmental disorders, including autism and schizophrenia. The potential mechanisms conferring this risk are poorly understood. Here, we show that the personality traits schizotypy and neuroticism correlated with paternal age in healthy subjects (N = 677). Paternal age was further positively associated with gray matter volume (VBM, N = 342) in the right prefrontal and the right medial temporal cortex. The integrity of fiber tracts (DTI, N = 222) connecting these two areas correlated positively with paternal age. Genome-wide methylation analysis in humans showed differential methylation in APA individuals, linking APA to epigenetic mechanisms. A corresponding phenotype was obtained in our rat model. APA rats displayed social-communication deficits and emitted fewer pro-social ultrasonic vocalizations compared to controls. They further showed repetitive and stereotyped patterns of behavior, together with higher anxiety during early development. At the neurobiological level, microRNAs miR-132 and miR-134 were both differentially regulated in rats and humans depending on APA. This study demonstrates associations between APA and social behaviors across species. They might be driven by changes in the expression of microRNAs and/or epigenetic changes regulating neuronal plasticity, leading to brain morphological changes and fronto-hippocampal connectivity, a network which has been implicated in social interaction.

Paternal morphine self-administration produces object recognition memory deficits in female, but not male offspring

RATIONALE

Parental drug use around or before conception can have adverse consequences for offspring. Historically, this research has focused on the effects of maternal substance use on future generations but less is known about the influence of the paternal lineage. This study focused on the impact of chronic paternal morphine exposure prior to conception on behavioral outcomes in male and female progeny.

OBJECTIVES

This study sought to investigate the impact of paternal morphine self-administration on anxiety-like behavior, the stress response, and memory in male and female offspring.

METHODS

Adult, drug-naïve male and female progeny of morphine-treated sires and controls were evaluated for anxiety-like behavior using defensive probe burying and novelty-induced hypophagia paradigms. Hypothalamic-pituitary-adrenal (HPA) axis function was assessed by measuring plasma corticosterone levels following a restraint stressor in male and female progeny. Memory was probed using a battery of tests including object location memory, novel object recognition, and contextual fear conditioning.

RESULTS

Paternal morphine exposure did not alter anxiety-like behavior or stress-induced HPA axis activation in male or female offspring. Morphine-sired male and female offspring showed intact hippocampus-dependent memory: they performed normally on the long-term fear conditioning and object location memory tests. In contrast, paternal morphine exposure selectively disrupted novel object recognition in female, but not male, progeny.

CONCLUSIONS

Our findings demonstrate that paternal morphine taking produces sex-specific and selective impairments in object recognition memory while leaving hippocampal function largely intact.

Ancestral stress programs sex-specific biological aging trajectories and non-communicable disease risk

The incidence of non-communicable diseases (NCDs) is rising globally but their causes are generally not understood. Here we show that cumulative ancestral stress leads to premature aging and raises NCD risk in a rat population. This longitudinal study revealed that cumulative multigenerational prenatal stress (MPS) across four generations (F0-F3) raises age- and sex-dependent adverse health outcomes in F4 offspring. MPS accelerated biological aging processes and exacerbated sex-specific incidences of respiratory and kidney diseases, inflammatory processes and tumors. Unbiased deep sequencing of frontal cortex revealed that MPS altered expression of microRNAs and their target genes involved in synaptic plasticity, stress regulation, immune function and longevity. Multi-layer top-down deep learning metabolite enrichment analysis of urine markers revealed altered metabolic homeodynamics in MPS males. Thus, peripheral metabolic signatures may provide sensitive biomarkers of stress vulnerability and disease risk. Programming by MPS appears to be a significant determinant of lifetime mental health trajectories, physical wellbeing and vulnerability to NCDs through altered epigenetic regulation.

Environmental epigenetics and epigenetic inheritance in domestic farm animals

Epigenetics refers to molecular factors and processes around DNA that can affect genome activity and gene expression independent of DNA sequence. Epigenetic mechanisms drive developmental processes and have also been shown to be tied to disease development. Many epigenetic studies have been done using plants, rodent, and human models, but fewer have focused on domestic livestock species. The goal of this review is to present current epigenetic findings in livestock species (cattle, pigs, sheep and poultry). Much of this research examined epigenetic effects following exposure to toxicants, nutritional changes or infectious disease in those animals directly exposed, or in the offspring they produced. A limited number of studies in domestic animals have examined epigenetic transgenerational inheritance in the absence of continued exposures. One example used a porcine model to investigate the effect that feeding males a diet supplemented with micronutrients had on liver DNA methylation and muscle mass in grand-offspring (the transgenerational F2 generation). Further research into how epigenetic mechanisms affect the health and production traits of domestic livestock and their offspring is important to elucidate.

Epigenetics, Gender, and Sex in the Diagnosis of Depression

Background :

A marked sexual dimorphism exists in psychiatric diagnoses. Culture derived gender bias in diagnostic criteria is one explanation. Adverse childhood events, including sexual and physical abuse, are more reliable and consistent predictors of later psychiatric diagnoses, including depression and post-traumatic stress disorder. Some interesting interactions between genes and experience have been uncovered, but the primary effect appears to be epigenetic with life experience altering gene expression and being transmitted to subsequent generations.

Objectives :

To determine if reconceptualizing depression as encompassing both internalizing and externalizing strategies would eliminate gender differences in the diagnosis of depression

Methods :

We reviewed 74 life stories of patients, collected during a study of the effect of physicians’ knowing patients’ life stories on the quality of the doctor-patient relationship. Looking at diagnoses, the prevalence of women to men was 2.9 to 1. We redefined depression as a response to being in a seemingly hopeless situation accompanied by despair, either externalizing ((more often diagnosed as substance use disorders, impulse control disorders, antisocial personality disorder, or bipolar disorder) or internalizing (the more standard diagnosis of depression). Then we reviewed these life stories from that perspective to determine how many would be diagnosed as depressed.

Results :

With this reconceptualization of depression, the sex ratio changed to 1.2 to 1.

Conclusions:

From this perspective, men and women are equally likely to respond to hopelessness, though men are more socialized to externalize and women to internalize. Considering depression in this way may help to better identify men at risk for suicide.

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.

Towards precision medicine in generalized anxiety disorder: Review of genetics and pharmaco(epi)genetics

Generalized anxiety disorder (GAD) is a prevalent and chronic mental disorder that elicits widespread functional impairment. Given the high degree of non-response/partial response among patients with GAD to available pharmacological treatments, there is a strong need for novel approaches that can optimize outcomes, and lead to medications that are safer and more effective. Although investigations have identified interesting targets predicting treatment response through pharmacogenetics (PGx), pharmaco-epigenetics, and neuroimaging methods, these studies are often solitary, not replicated, and carry several limitations. This review provides an overview of the current status of GAD genetics and PGx and presents potential strategies to improve treatment response by combining better phenotyping with PGx and improved analytical methods. These strategies carry the dual benefit of delivering data on biomarkers of treatment response as well as pointing to disease mechanisms through the biology of the markers associated with response. Overall, these efforts can serve to identify clinical, genetic, and epigenetic factors that can be incorporated into a pharmaco(epi)genetic test that may ultimately improve treatment response and reduce the socioeconomic burden of GAD.