Epigenetic Regulation of Placental NR3C1: Mechanism Underlying Prenatal Programming of Infant Neurobehavior by Maternal Smoking?

Evidence for neurobehavioral risk phenotypes at birth

Observations of newborn behavior provide clinicians and researchers with a first description of the neurobehavioral organization of the newborn that is largely independent of the postnatal environment. The Neonatal Network Neurobehavioral Scale (NNNS) was developed in 2004 to evaluate how prenatal exposure to substances such as cocaine is related to neurobehavioral outcomes. There are now 156 empirical articles published using the NNNS, which we review and summarize. Z-scores from published studies using the NNNS were compiled and aggregated supporting the replicability of three newborn neurobehavioral phenotypes: one typical and two that are predictive of later cognitive and behavioral delay; hyper- and hypo-dysregulated newborns. These phenotypes emerged from independent samples and research groups and were identified in a variety of populations, including infants with prenatal substance exposure, preterm infants, and healthy term infants. Our findings show that newborn neurobehavior can be measured in a reliable and valid manner and that certain behavioral phenotypes, identifiable at birth, can predict neurodevelopmental challenges. These findings have important clinical utility. Intervening early with infants exhibiting these risk phenotypes may prevent later neurodevelopmental delay. IMPACT: We reviewed all empirical studies published using the Neonatal Network Neurobehavioral Scale and found evidence for two replicable stress phenotypes that predict later behavioral outcomes. This study highlights the utility of the Neonatal Network Neurobehavioral Scale for early identification of newborn neurodevelopmental risk phenotypes. Early identification of neurodevelopmental risk, when neuroplasticity is high, may ultimately reduce the burden of subsequent neurobehavioral problems through early intervention.

Early developmental risks for tobacco addiction: A probabilistic epigenesis framework

Considerable progress has been made in elucidating the relationships between early life psychobiological and environmental risk factors and the development of tobacco addiction. However, a comprehensive understanding of the heterogeneity in tobacco addiction phenotypes requires integrating research findings. The probabilistic epigenesis meta-theory offers a valuable framework for this integration, considering systemic, multilevel, developmental, and evolutionary perspectives. In this paper, we critically review relevant research on early developmental risks associated with tobacco addiction and highlight the integrative heuristic value of the probabilistic epigenesis framework for this research. For this, we propose a four-level systems approach as an initial step towards integration, analyzing complex interactions among different levels of influence. Additionally, we explore a coaction approach to examine key interactions between early risk factors. Moreover, we introduce developmental pathways to understand interindividual differences in tobacco addiction risk during development. This integrative approach holds promise for advancing our understanding of tobacco addiction etiology and informing potentially effective intervention strategies.

Epigenome-Wide Associations of Placental DNA Methylation and Behavioral and Emotional Difficulties in Children at 3 Years of Age

The placenta is a key organ for fetal and brain development. Its epigenome can be regarded as a biochemical record of the prenatal environment and a potential mechanism of its association with the future health of the fetus. We investigated associations between placental DNA methylation levels and child behavioral and emotional difficulties, assessed at 3 years of age using the Strengths and Difficulties Questionnaire (SDQ) in 441 mother-child dyads from the EDEN cohort. Hypothesis-driven and exploratory analyses (on differentially methylated probes (EWAS) and regions (DMR)) were adjusted for confounders, technical factors, and cell composition estimates, corrected for multiple comparisons, and stratified by child sex. Hypothesis-driven analyses showed an association of cg26703534 (AHRR) with emotional symptoms, and exploratory analyses identified two probes, cg09126090 (intergenic region) and cg10305789 (PPP1R16B), as negatively associated with peer relationship problems, as well as 33 DMRs, mostly positively associated with at least one of the SDQ subscales. Among girls, most associations were seen with emotional difficulties, whereas in boys, DMRs were as much associated with emotional than behavioral difficulties. This study provides the first evidence of associations between placental DNA methylation and child behavioral and emotional difficulties. Our results suggest sex-specific associations and might provide new insights into the mechanisms of neurodevelopment.

Associations between prenatal exposure to second hand smoke and infant self-regulation in a New York city longitudinal prospective birth cohort

BACKGROUND

Prenatal exposure to active or passive maternal smoking -also referred to as second hand smoke (SHS) exposure - are associated with externalizing behaviors, hyperactivity and attention deficit hyperactivity disorder, problems which derive in part from altered self-regulation.

OBJECTIVES

Determine the influence of prenatal SHS on infant self-regulation using direct measures of infant behavior in 99 mothers from the Fair Start birth cohort followed at the Columbia Center for Children's Environmental Health.

METHODS

Self-regulation was operationalized with self-contingency, the likelihood of maintaining/changing behavior from second-to-second, measured via split-screen video recordings of mothers playing with their 4-month infants. Mother and infant facial and vocal affect, gaze-on/-off partner, and mother touch were coded on a 1 s time-base. Third trimester prenatal SHS was assessed via self-report of a smoker in the home. Weighted-lag time-series models tested conditional effects of SHS-exposure (vs. non-exposure) on infant self-contingency for eight modality-pairings (e.g., mother gaze-infant gaze). Individual-seconds time-series models and analysis of predicted values at t₀ interrogated significant weighted-lag findings. Because prior findings link developmental risk factors with lowered self-contingency, we hypothesized that prenatal SHSSHS would predict lowered infant self-contingency.

RESULTS

Relative to non-exposed infants, those who were prenatally exposed to SHS had lower self-contingency (more variable behavior) in all eight models. Follow-up analyses showed that, given infants were likely to be in the most negative facial or vocal affect, those with prenatal SHS were more likely to make larger behavioral changes, moving into less negative or more positive affect and to alternate between gaze-on and off mother. Mothers who were exposed to SHS during pregnancy (vs. non-exposed) showed a similar, albeit less prevalent, pattern of larger changes out of negative facial affect.

CONCLUSION

These findings extend prior work linking prenatal SHS with youth dysregulated behavior, showing similar effects in infancy, a critically important period that sthe stage for future child development.

The Molecular Gut-Brain Axis in Early Brain Development

Millions of nerves, immune factors, and hormones in the circulatory system connect the gut and the brain. In bidirectional communication, the gut microbiota play a crucial role in the gut-brain axis (GBA), wherein microbial metabolites of the gut microbiota regulate intestinal homeostasis, thereby influencing brain activity. Dynamic changes are observed in gut microbiota as well as during brain development. Altering the gut microbiota could serve as a therapeutic target for treating abnormalities associated with brain development. Neurophysiological development and immune regulatory disorders are affected by changes that occur in gut microbiota composition and function. The molecular aspects relevant to the GBA could help develop targeted therapies for neurodevelopmental diseases. Herein, we review the findings of recent studies on the role of the GBA in its underlying molecular mechanisms in the early stages of brain development. Furthermore, we discuss the bidirectional regulation of gut microbiota from mother to infant and the potential signaling pathways and roles of posttranscriptional modifications in brain functions. Our review summarizes the role of molecular GBA in early brain development and related disorders, providing cues for novel therapeutic targets.

Epigenetic Biomarkers Screening of Non-Coding RNA and DNA Methylation Based on Peripheral Blood Monocytes in Smokers

This study aims to use bioinformatics methods to determine the epigenetic changes in microRNA expression and DNA methylation caused by cigarette smoking. The data of mRNA, miRNA expression, and methylation microarray were obtained from the GEO database to filter differentially expressed genes (DEGs), differentially expressed miRNAs (DEMs), and methylated CpG probes (DMPs) through the limma package. The R clusterProfile package was used for functional annotation and enrichment analysis. The protein-protein interaction (PPI) network was constructed by the String database and visualized in Cytoscape software. Starbase database was employed to predict lncRNA and CirRNA based on the sequence of miRNA, and to establish a regulatory network of ceRNA. By overlapping DEG and DEM, 107 down-miRNA-targeted up-regulated genes and 65 up-miRNA-target down-regulated genes were obtained, which were mainly enriched in autophagy signaling pathways and protein ubiquitination pathways, respectively. In addition, 324 genes with low methylation and high expression and 204 genes with high methylation and low expression were respectively related to the degeneration of the nervous system and the function of the cardiovascular system. Interestingly, 43 genes were up-regulated under the dual regulation of reduced miRNA and hypomethylation, while 14 genes were down-regulated under the dual regulation of increased miRNA and hypermethylation. Ten chemicals have been identified as putative therapeutic agents for pathological conditions caused by smoking. In addition, among these genes, HSPA4, GRB2, PRKCA, and BCL2L1 could play a fundamental role in related diseases caused by smoking and may be used as the biomarkers for precise diagnosis and targets for future therapies of smoking-related diseases.

Prenatal substance exposure and maternal hostility from pregnancy to toddlerhood: Associations with temperament profiles at 16 months of age

We investigated whether infant temperament was predicted by level of and change in maternal hostility, a putative transdiagnostic vulnerability for psychopathology, substance use, and insensitive parenting. A sample of women (N = 247) who were primarily young, low-income, and had varying levels of substance use prenatally (69 nonsmokers, 81 tobacco-only smokers, and 97 tobacco and marijuana smokers) reported their hostility in the third trimester of pregnancy and at 2, 9, and 16 months postpartum, and their toddler's temperament and behavior problems at 16 months. Maternal hostility decreased from late pregnancy to 16 months postpartum. Relative to pregnant women who did not use substances, women who used both marijuana and tobacco prenatally reported higher levels of hostility while pregnant and exhibited less change in hostility over time. Toddlers who were exposed to higher levels of prenatal maternal hostility were more likely to be classified in temperament profiles that resemble either irritability or inhibition, identified via latent profile analysis. These two profiles were each associated with more behavior problems concurrently, though differed in their association with competence. Our results underscore the utility of transdiagnostic vulnerabilities in understanding the intergenerational transmission of psychopathology risk and are discussed in regards to the Research Domain Criteria (RDoC) framework.

DNA methylome perturbations: an epigenetic basis for the emergingly heritable neurodevelopmental abnormalities associated with maternal smoking and maternal nicotine exposure†

Maternal smoking during pregnancy is associated with an ensemble of neurodevelopmental consequences in children and therefore constitutes a pressing public health concern. Adding to this burden, contemporary epidemiological and especially animal model research suggests that grandmaternal smoking is similarly associated with neurodevelopmental abnormalities in grandchildren, indicative of intergenerational transmission of the neurodevelopmental impacts of maternal smoking. Probing the mechanistic bases of neurodevelopmental anomalies in the children of maternal smokers and the intergenerational transmission thereof, emerging research intimates that epigenetic changes, namely DNA methylome perturbations, are key factors. Altogether, these findings warrant future research to fully elucidate the etiology of neurodevelopmental impairments in the children and grandchildren of maternal smokers and underscore the clear potential thereof to benefit public health by informing the development and implementation of preventative measures, prophylactics, and treatments. To this end, the present review aims to encapsulate the burgeoning evidence linking maternal smoking to intergenerational epigenetic inheritance of neurodevelopmental abnormalities, to identify the strengths and weaknesses thereof, and to highlight areas of emphasis for future human and animal model research therein.

Biobehavioral organization shapes the immune epigenome in infant rhesus Macaques (Macaca mulatta)

How individuals respond to and cope with stress is linked with their health and well-being. It is presumed that early stress responsiveness helps shape the health of the developing organism, but the relationship between stress responsiveness and early immune function during development is not well-known. We hypothesized that stress responsiveness may shape epigenetic regulation of immune genes in infancy. We investigated whether aspects of behavioral responsiveness and hypothalamic-pituitary adrenal stress-response were associated with epigenome-wide immune cell DNA methylation patterns in 154 infant rhesus monkeys (3-4 months old). Infants' behavioral and physiological responses were collected during a standardized biobehavioral assessment, which included temporary relocation and separation from their mother and social group. Genome-wide DNA methylation was quantified using restricted representation bisulfite sequencing (RRBS) from blood DNA collected 2-hours post-separation. Epigenome-wide analyses were conducted using simple regression, multiple regression controlling for immune cell counts, and permutation regression, all corrected for false discovery rate. Across the variables analyzed, there were 20,368 unique sites (in 9,040 genes) at which methylation was significantly associated with at least one behavioral responsiveness or cortisol measure across the three analyses. There were significant associations in 442 genes in the Immune System Process ontology category, and 94 genes in the Inflammation mediated by chemokine and cytokine signaling gene pathway. Out of 35 candidate genes that were selected for further investigation, there were 13 genes with at least one site at which methylation was significantly associated with behavioral responsiveness or cortisol, including two intron sites in the glucocorticoid receptor gene, at which methylation was negatively correlated with emotional behavior the day following the social separation (Day 2 Emotionality; β = -0.39, q < 0.001) and cortisol response following a relocation stressor (Sample 1; β = -0.33, q < 0.001). We conclude that biobehavioral stress responsiveness may correlate with the developing epigenome, and that DNA methylation of immune cells may be a mechanism by which patterns of stress response affect health and immune functioning.

Epigenetic Alterations of Maternal Tobacco Smoking during Pregnancy: A Narrative Review

In utero exposure to maternal tobacco smoking is the leading cause of birth complications in addition to being associated with later impairment in child's development. Epigenetic alterations, such as DNA methylation (DNAm), miRNAs expression, and histone modifications, belong to possible underlying mechanisms linking maternal tobacco smoking during pregnancy and adverse birth outcomes and later child's development. The aims of this review were to provide an update on (1) the main results of epidemiological studies on the impact of in utero exposure to maternal tobacco smoking on epigenetic mechanisms, and (2) the technical issues and methods used in such studies. In contrast with miRNA and histone modifications, DNAm has been the most extensively studied epigenetic mechanism with regard to in utero exposure to maternal tobacco smoking. Most studies relied on cord blood and children's blood, but placenta is increasingly recognized as a powerful tool, especially for markers of pregnancy exposures. Some recent studies suggest reversibility in DNAm in certain genomic regions as well as memory of smoking exposure in DNAm in other regions, upon smoking cessation before or during pregnancy. Furthermore, reversibility could be more pronounced in miRNA expression compared to DNAm. Increasing evidence based on longitudinal data shows that maternal smoking-associated DNAm changes persist during childhood. In this review, we also discuss some issues related to cell heterogeneity as well as downstream statistical analyses used to relate maternal tobacco smoking during pregnancy and epigenetics. The epigenetic effects of maternal smoking during pregnancy have been among the most widely investigated in the epigenetic epidemiology field. However, there are still huge gaps to fill in, including on the impact on miRNA expression and histone modifications to get a better view of the whole epigenetic machinery. The consistency of maternal tobacco smoking effects across epigenetic marks and across tissues will also provide crucial information for future studies. Advancement in bioinformatic and biostatistics approaches is key to develop a comprehensive analysis of these biological systems.

Glucocorticoid receptor gene (NR3C1) methylation during the first thousand days: Environmental exposures and developmental outcomes

The first 1000 days from conception are a sensitive period for human development programming. During this period, environmental exposures may result in long-lasting epigenetic imprints that contribute to future developmental trajectories. The present review reports on the effects of adverse and protective environmental conditions occurring during the first 1000 days on glucocorticoid receptor gene (NR3C1) regulation in humans. Thirty-four studies were included. Wide variations emerged for biological tissues, number and position of analyzed CpG sites, and age at methylation and outcomes assessment. Increased NR3C1 methylation associated with first 1000 days stress exposures. Maternal caregiving behaviors significantly buffered precocious stress exposures. A less robust pattern of findings emerged for the association of NR3C1 methylation with physical health, neurobehavioral and neuroendocrine outcomes. Although drawing comprehensive conclusions is partially hindered by methodological limitations, the present review underlines the relevance of the first 1000 days from conception as a time window for developmental plasticity. Prospective cohort studies and epigenome-wide approaches may increase our understanding of dynamics epigenetic changes and their consequences for child development.

A systematic review of childhood maltreatment and DNA methylation: candidate gene and epigenome-wide approaches

Childhood maltreatment is a major risk factor for chronic and severe mental and physical health problems across the lifespan. Increasing evidence supports the hypothesis that maltreatment is associated with epigenetic changes that may subsequently serve as mechanisms of disease. The current review uses a systematic approach to identify and summarize the literature related to childhood maltreatment and alterations in DNA methylation in humans. A total of 100 empirical articles were identified in our systematic review of research published prior to or during March 2020, including studies that focused on candidate genes and studies that leveraged epigenome-wide data in both children and adults. Themes arising from the literature, including consistent and inconsistent patterns of results, are presented. Several directions for future research, including important methodological considerations for future study design, are discussed. Taken together, the literature on childhood maltreatment and DNA methylation underscores the complexity of transactions between the environment and biology across development.

Measuring the Outcomes of Maternal COVID-19-related Prenatal Exposure (MOM-COPE): study protocol for a multicentric longitudinal project

INTRODUCTION

COVID-19 is a highly infectious respiratory disease that rapidly emerged as an unprecedented epidemic in Europe, with a primary hotspot in Northern Italy during the first months of 2020. Its high infection rate and rapid spread contribute to set the risk for relevant psychological stress in citizens. In this context, mother-infant health is at risk not only because of potential direct exposure to the virus but also due to high levels of stress experienced by mothers from conception to delivery. Prenatal stress exposure associates with less-than-optimal child developmental outcomes, and specific epigenetic mechanisms (eg, DNA methylation) may play a critical role in mediating this programming association.

METHODS AND ANALYSIS

We present the methodological protocol for a longitudinal, multicentric study on the behavioural and epigenetic effects of COVID-19-related prenatal stress in a cohort of mother-infant dyads in Northern Italy. The dyads will be enrolled at 10 facilities in Northern Italy. Saliva samples will be collected at birth to assess the methylation status of specific genes linked with stress regulation in mothers and newborns. Mothers will provide retrospective data on COVID-19-related stress during pregnancy. At 3, 6 and 12 months, mothers will provide data on child behavioural and socioemotional outcomes, their own psychological status (stress, depressive and anxious symptoms) and coping strategies. At 12 months, infants and mothers will be videotaped during semistructured interaction to assess maternal sensitivity and infant's relational functioning.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee (Pavia). Results will be published in peer-reviewed journals and presented at national and international scientific conferences.

TRIAL REGISTRATION NUMBER

NCT04540029; Pre-results.

Neurodevelopment of high and low-risk pregnancy babies at 6 months of age

OBJECTIVE

to compare neurodevelopment differences between babies born from low-risk pregnancies and babies born from high-risk pregnancies.

STUDY DESIGN

Longitudinal design SETTING: Spain PARTICIPANTS: A total of 91 women participated in the study, divided into two groups: 49 women in the low-risk pregnancy group and 42 women in the high-risk group.

MEASUREMENT AND FINDINGS

The average amount of cortisol in pregnant mothers' hair was determined in both groups. Following their birth, the babies' neurodevelopment was evaluated using the Bayley-III instrument at 6 months of age and a new sample of cortisol was obtained from both the baby and the mother. The results showed that pregnancy risk group could predict cognitive, fine motor, gross motor and general motor neurodevelopment.

KEY CONCLUSIONS

These results seem to show that an appropriate treatment tailored to the needs of individualised pregnancies may favor babies' neurodevelopment, including that of babies born from high-risk pregnancies.

IMPLICATIONS FOR RESEARCH

It is essential to take special care of pregnant women no matter their medical condition and offer them the best medical care available.

Prenatal tobacco and marijuana co-use: Sex-specific influences on infant cortisol stress response

Although tobacco (TOB) and marijuana (MJ) are often co-used in pregnancy, little is known regarding the joint impact of MJ + TOB on offspring development, including the developing neuroendocrine stress system. Further, despite evidence for sex-specific impacts of prenatal exposures in preclinical models, the sex-specific impact of prenatal MJ + TOB exposure on offspring neuroendocrine regulation in humans is also unknown. In the current study, overall and sex-specific influences of MJ + TOB co-use on offspring cortisol regulation were investigated over the first postnatal month. 111 mother-infant pairs from a low-income, racially and ethnically diverse sample participated. Based on Timeline Followback data with biochemical verification, three groups were identified: (1) prenatal MJ + TOB, (2) TOB only, and (3) controls. Baseline cortisol and cortisol stress response were assessed at seven points over the first postnatal month using a handling paradigm in which saliva cortisol was assessed before, during, and following a standard neurobehavioral assessment (NICU Network Neurobehavioral Scale). A significant exposure group by offspring sex interaction emerged for baseline cortisol over the first postnatal month (p = .043); MJ + TOB-exposed males showed 35-36% attenuation of baseline cortisol levels vs. unexposed and TOB-exposed males (ps ≤ .003), while no effects of exposure emerged for females. Both MJ + TOB and TOB-exposed infants showed a 22% attenuation of cortisol stress response over the first postnatal month vs. unexposed infants (ps < .03), with evidence for sex-specific effects in exploratory analyses. Although results are preliminary, this is the first human study to investigate the impact of prenatal MJ exposure on infant cortisol and the first to reveal a sex-specific impact of prenatal MJ + TOB on cortisol regulation in humans. Future, larger-scale studies are needed to elucidate mechanisms and consequences of sex-specific effects of MJ and MJ + TOB on the developing neuroendocrine stress system.

Combined neurodevelopmental exposure to deltamethrin and corticosterone is associated with Nr3c1 hypermethylation in the midbrain of male mice

Attention-Deficit Hyperactivity Disorder (ADHD) is one of the most common neurodevelopmental disorders and manifests inattention, hyperactivity, and impulsivity symptoms in childhood that can last throughout life. Genetic and environmental studies implicate the dopamine system in ADHD pathogenesis. Work from our group and that of others indicates that deltamethrin insecticide and stress exposure during neurodevelopment leads to alterations in dopamine function, and we hypothesized that exposure to both of these factors together would lead to synergistic effects on DNA methylation of key genes within the midbrain, a highly dopaminergic region, that could contribute to these findings. Through targeted next-generation sequencing of a panel of cortisol and dopamine pathway genes, we observed hypermethylation of the glucocorticoid receptor gene, Nr3c1, in the midbrain of C57/BL6N males in response to dual deltamethrin and corticosterone exposures during development. This is the first description of DNA methylation studies of Nr3c1 and key dopaminergic genes within the midbrain in response to a pyrethroid insecticide, corticosterone, and these two exposures together. Our results provide possible connections between environmental exposures that impact the dopamine system and the hypothalamic-pituitary-adrenal axis via changes in DNA methylation and provides new information about the presence of epigenetic effects in adulthood after exposure during neurodevelopment.

The placenta-brain-axis

All mammalian species depend on the placenta, a transient organ, for exchange of gases, nutrients, and waste between the mother and conceptus. Besides serving as a conduit for such exchanges, the placenta produces hormones and other factors that influence maternal physiology and fetal development. To meet all of these adaptations, the placenta has evolved to become the most structurally diverse organ within all mammalian taxa. However, commonalities exist as to how placental responses promote survival against in utero threats and can alter the trajectory of fetal development, in particular the brain. Increasing evidence suggests that reactions of the  placenta to various in utero stressors may lead to long-standing health outcomes, otherwise considered developmental origin of health and disease effects. Besides transferring nutrients and gases, the placenta produces neurotransmitters, including serotonin, dopamine, norepinephrine/epinephrine, that may circulate and influence brain development. Neurobehavioral disorders, such as autism spectrum disorders, likely trace their origins back to placental disturbances. This intimate relationship between the placenta and brain has led to coinage of the term, the placenta-brain-axis. This axis will be the focus herein, including how conceptus sex might influence it, and technologies employed to parse out the effects of placental-specific transcript expression changes on later neurobehavioral disorders. Ultimately, the placenta might provide a historical record of in utero threats the fetus confronted and a roadmap to understand how placenta responses to such encounters impacts the placental-brain-axis. Improved early diagnostic and preventative approaches may thereby be designed to mitigate such placental disruptions.

Placental Studies for Child Development

Research on children's psychological and behavioral development readily incorporates changing biological models and techniques. In this article, we suggest that, in response to increasing evidence of robust influences of prenatal exposures on children's neurodevelopment and mental and physical health, developmental science also needs to consider the placenta's role in development. We argue why placental mechanisms are plausible targets in developmental science, and suggest initial and practical steps toward integrating placenta markers and mechanisms into research on child development.

Microorganisms in the Placenta: Links to Early-Life Inflammation and Neurodevelopment in Children

Prenatal exposure to various stressors can influence both early and later life childhood health. Microbial infection of the intrauterine environment, specifically within the placenta, has been associated with deleterious birth outcomes, such as preterm birth, as well as adverse neurological outcomes later in life. The relationships among microorganisms in the placenta, placental function, and fetal development are not well understood. Microorganisms have been associated with perinatal inflammatory responses that have the potential for disrupting fetal brain development. Microbial presence has also been associated with epigenetic modifications in the placenta, as well other tissues. Here we review research detailing the presence of microorganisms in the placenta and associations among such microorganisms, placental DNA methylation, perinatal inflammation, and neurodevelopmental outcomes.

Neonatal NR3C1 Methylation and Social-Emotional Development at 6 and 18 Months of Age

The variation in childhood social-emotional development within at-risk populations may be attributed in part to epigenetic mechanisms such as DNA methylation (DNAm) that respond to environmental stressors. These mechanisms may partially underlie the degree of vulnerability (and resilience) to negative social-emotional development within adverse psychosocial environments. Extensive research supports an association between maternal adversity and offspring DNAm of the NR3C1 gene, which encodes the glucocorticoid receptor (GR). A gap in knowledge remains regarding the relationship between NR3C1 DNAm, measured in neonatal (1-month of age) buccal cells, and subsequent social-emotional development during infancy and early childhood. We conducted a longitudinal cohort study of n = 53 mother-child dyads (n = 30 with developmental outcomes formed the basis of current study) who were enrolled in a home visiting (HV) program. Higher mean DNAm of the NR3C1 exon 1F promoter was significantly associated with lower 6-month Ages and Stages Questionnaire: Social-Emotional (ASQ:SE) scores-more positive infant social-emotional functioning. A similar trend was observed at 18-months of age in a smaller sample (n = 12). The findings of this pilot study indicate that in a diverse and disadvantaged population, the level of neonatal NR3C1 DNAm is related to later social-emotional development. Limitations and implications for future research are discussed.

Prenatal tobacco and marijuana co-use: Impact on newborn neurobehavior

Tobacco and marijuana are some of the most common prenatal substance exposures worldwide. The social acceptability and political landscape of marijuana and its potency have changed dramatically in the last two decades leading to increased use by pregnant women. Despite evidence for increasing marijuana use and high rates of co-use of tobacco (TOB) and marijuana (MJ) during pregnancy, the impact of prenatal exposure to each substance is typically studied in isolation. We investigated the influence of co-exposure to TOB and MJ on infant neurobehavioral development over the first postnatal month. Participants were 111 mother-infant pairs from a low-income, diverse sample (Mean age = 25 ± 5; 54% minorities). TOB and MJ use were assessed by Timeline Followback interview with biochemical confirmation. Three groups were identified: (a) prenatal MJ + TOB, (b) prenatal TOB only, (c) controls. Newborn neurobehavior was assessed at seven time points over the first postnatal month using the NICU Network Neurobehavioral Scale. MJ + TOB-exposed infants showed decreased ability to self-soothe (Self-regulation) and attend to stimuli (Attention), and increased need for examiner soothing (Handling) and low motor activity (Lethargy) versus unexposed infants. Despite low levels of MJ use in MJ + TOB co-users, co-exposure was associated with nearly double the impact on infant self-soothing and need for examiner soothing versus TOB-exposure alone. Effects of MJ + TOB co-exposure appeared more pronounced for daughters than for sons. Although results are preliminary, they highlight additional risk from dual exposure to MJ + TOB vs. TOB exposure alone, particularly for daughters. Results also highlight the critical importance of investigating prenatal exposures in concert and the need for intervention efforts to address MJ co-use in pregnant TOB users.

An epigenetic pathway approach to investigating associations between prenatal exposure to maternal mood disorder and newborn neurobehavior

Following recent advances in behavioral and psychiatric epigenetics, researchers are increasingly using epigenetic methods to study prenatal exposure to maternal mood disorder and its effects on fetal and newborn neurobehavior. Despite notable progress, various methodological limitations continue to obscure our understanding of the epigenetic mechanisms underpinning prenatal exposure to maternal mood disorder on newborn neurobehavioral development. Here we detail this problem, discussing limitations of the currently dominant analytical approaches (i.e., candidate epigenetic and epigenome-wide association studies), then present a solution that retains many benefits of existing methods while minimizing their shortcomings: epigenetic pathway analysis. We argue that the application of pathway-based epigenetic approaches that target DNA methylation at transcription factor binding sites could substantially deepen our mechanistic understanding of how prenatal exposures influence newborn neurobehavior.

The role of nicotinic receptor genes (CHRN) in the pathways of prenatal tobacco exposure on smoking behavior among young adult light smokers

BACKGROUND

Prenatal tobacco exposure (PTE) is associated with more frequent smoking among young, light smokers. Little is known about how nicotinic acetylcholine receptor (CHRN) genes may contribute to this relationship.

METHODS

Data were drawn from a longitudinal cohort of young light smokers of European ancestry (N = 511). Three single nucleotide polymorphisms (SNPs) among offspring, rs16969968 and rs6495308 in CHRNA5A3B4 and rs2304297 in CHRNB3A6, were analyzed with respect to whether they 1) predict PTE status; 2) confound the previously-reported effects of PTE on future smoking; 3) have effects on youth smoking frequency that are mediated through PTE; and 4) have effects that are moderated by PTE.

RESULTS

rs2304297 and rs6495308 were associated with increased likelihood and severity of PTE, respectively. In a path analysis, rs16969968 directly predicted more frequent smoking in young adulthood (B = 1.50, p = .044); this association was independent of, and not mediated by, PTE. The risk of rs16969968 (IRR = 1.07, p = .015) and the protective effect of rs2304297 (IRR = 0.84, p < .001) on smoking frequency were not moderated by PTE. PTE moderated the effect of rs6495308, such that these alleles were protective against later smoking frequency only among non-exposed youth (IRR = 0.85, p < .001).

CONCLUSIONS

The association between offspring CHRNB3A6 and PTE is a novel finding. The risk of rs16969968 on youth smoking is independent and unrelated to that of PTE among young, light smokers. PTE moderates the protective effect of rs6495308 on youth smoking frequency. However, PTE's pathway to youth smoking behavior was not explained by these genetic factors, leaving its mechanism(s) of action unclear.

Impact of maternal prenatal smoking on fetal to infant neurobehavioral development

Despite recent emphasis on the profound importance of the fetal environment in "programming" postnatal development, measurement of offspring development typically begins after birth. Using a novel coding strategy combining direct fetal observation via ultrasound and actocardiography, we investigated the impact of maternal smoking during pregnancy (MSDP) on fetal neurobehavior; we also investigated links between fetal and infant neurobehavior. Participants were 90 pregnant mothers and their infants (52 MSDP-exposed; 51% minorities; ages 18-40). Fetal neurobehavior at baseline and in response to vibro-acoustic stimulus was assessed via ultrasound and actocardiography at M = 35 weeks gestation and coded via the Fetal Neurobehavioral Assessment System (FENS). After delivery, the NICU Network Neurobehavioral Scale was administered up to seven times over the first postnatal month. MSDP was associated with increased fetal activity and fetal limb movements. Fetal activity, complex body movements, and cardiac-somatic coupling were associated with infants' ability to attend to stimuli and to self-regulate over the first postnatal month. Furthermore, differential associations emerged by MSDP group between fetal activity, complex body movements, quality of movement, and coupling, and infant attention and self-regulation. The present study adds to a growing literature establishing the validity of fetal neurobehavioral measures in elucidating fetal programming pathways.

Additive drug-specific and sex-specific risks associated with co-use of marijuana and tobacco during pregnancy: Evidence from 3 recent developmental cohorts (2003-2015)

BACKGROUND

Methodologic challenges related to the concomitant use (co-use) of substances and changes in policy and potency of marijuana contribute to ongoing uncertainty about risks to fetal neurodevelopment associated with prenatal marijuana use. In this study, we examined two biomarkers of fetal neurodevelopmental risk-birth weight and length of gestation-associated with prenatal marijuana use, independent of tobacco (TOB), alcohol (ALC), other drug use (OTH), and socioeconomic risk (SES), in a pooled sample (N = 1191) derived from 3 recent developmental cohorts (2003-2015) with state-of-the-art substance use measures. We examined differential associations by infant sex, and multiplicative effects associated with co-use of MJ and TOB.

METHODS

Participants were mother-infant dyads with complete data on all study variables derived from Growing Up Healthy (n = 251), Behavior and Mood in Babies and Mothers (Cohorts 1 and 2; n = 315), and the Early Growth and Development Study (N = 625). We estimated direct effects on birth weight and length of gestation associated with MJ, TOB, and co-use (MJ x TOB), using linear regression analysis in the full sample, and in male (n = 654) and female (n = 537) infants, separately.

RESULTS

Mean birth weight and length of gestation were 3277 g (SD = 543) and 37.8 weeks (SD = 2.0), respectively. Rates of prenatal use were as follows: any use, n = 748 (62.8%); MJ use, n = 273 (22.9%); TOB use, n = 608 (51.0%); co-use of MJ and TOB, n = 230 (19.3%); ALC use, n = 464 (39.0%); and OTH use n = 115 (9.7%.) For all infants, unique effects on birth weight were observed for any MJ use [B(SE) = -84.367(38.271), 95% C.I. -159.453 to -9.281, p = .028], any TOB use [B(SE) = -0.99.416(34.418), 95% C.I. -166.942 to -31.889, p = .004], and each cigarette/day in mean TOB use [B(SE) = -12.233(3.427), 95% C.I. -18.995 to -5.510, p < .001]. Additional effects of co-use on birth weight, beyond these drug-specific effects, were not supported. In analyses stratified by sex, while TOB use was associated with lower birth weight in both sexes, MJ use during pregnancy was associated with lower birth weight of male infants [B(SE) = -153.1 (54.20); 95% C.I. -259.5 to -46.7, p = .005], but not female infants [B(SE) = 8.3(53.1), 95% C.I. -96.024 to 112.551, p = .876]. TOB, MJ, and their co-use were not associated with length of gestation.

CONCLUSIONS

In this sample, intrauterine co-exposure to MJ and TOB was associated with an estimated 18% reduction in birth weight not attributable to earlier delivery, exposure to ALC or OTH drugs, nor to maternal SES. We found evidence for greater susceptibility of male fetuses to any prenatal MJ exposure. Examination of dose-dependence in relationships found in this study, using continuous measures of exposure, is an important next step. Finally, we underscore the need to consider (a) the potential moderating influence of fetal sex on exposure-related neurodevelopmental risks; and (b) the importance of quantifying expressions of risk through subtle alterations, rather than dichotomous outcomes.

Possible roles for glucocorticoid signalling in breast cancer

Our understanding of breast cancer biology, and our ability to manipulate breast cancers have grown exponentially in the last 20 years. Much of that expansion has focused on the roles of steroids in driving these neoplasms. Initially this research focused on estrogens and progesterone receptors, and more recently on androgen actions in breast cancers. This review aims to make the case for glucocorticoids as the next essential steroid subclass that contributes significantly to our understanding of steroidogenic regulation of these neoplasms. Glucocorticoids have the potential to play multiple roles in the regulation of breast cancers including their control of cellular differentiation, apoptosis and proliferation. Beyond this they also act as a master integrator of organ homeostats in relation to such as circadian rhythms and stress responses. Therefore a better understanding of glucocorticoids and breast cancer could help to explain some of the epidemiological links between circadian disruption and/or stress and breast cancer development. Finally glucocorticoids are currently used during chemotherapeutic treatment in breast cancer therapy and yet results of various studies suggest that this may have an adverse impact on treatment success. This review aims to summarise the current evidence for glucocorticoids as actors in breast cancer and then suggest future essential approaches in order to determine the roles of glucocorticoids in this disease.

Maternal depression, antidepressant use and placental oxytocin receptor DNA methylation: Findings from the MPEWS study

The aim of this study was to investigate placental DNA methylation of the oxytocin receptor gene (OXTR) in women with depression in pregnancy. We also explored the role of antidepressant medication in pregnancy on placental OXTR methylation. Data were obtained from 239 women in the Mercy Pregnancy and Emotional Wellbeing Study (MPEWS), a selected pregnancy cohort. Current depressive disorders were diagnosed using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (SCID-IV). Depressive symptoms were measured during the third trimester in pregnancy using the Edinburgh Postnatal Depression Scale (EPDS). Plasma levels of antidepressant drugs were measured in maternal and cord blood obtained at delivery. OXTR DNA methylation was measured in placenta samples. Depressive symptoms in pregnancy were not associated with significant changes in DNA methylation of OXTR in the placenta. Cord plasma antidepressant levels were more strongly associated than maternal antidepressant dose or circulating blood antidepressant levels with increased DNA methylation of a specific unit within the promotor region of OXTR. This study provides preliminary data to suggest that antidepressant use during pregnancy can alter OXTR methylation in placental tissue. Our findings also indicate that the way exposures are measured in pregnancy can influence the direction and strength of findings. Future studies should investigate whether altered OXTR methylation might mediate the impacts of maternal antidepressant treatment on pregnancy and offspring outcomes.

Epigenetic mechanisms in the placenta related to infant neurodevelopment

As the 'third brain' the placenta links the developing fetal brain and the maternal brain enabling study of epigenetic process in placental genes that affect infant neurodevelopment. We described the characteristics and findings of the 17 studies on epigenetic processes in placental genes and human infant neurobehavior. Studies showed consistent findings in the same cohort of term healthy infants across epigenetic processes (DNA methylation, genome wide, gene and miRNA expression) genomic region (single and multiple genes, imprinted genes and miRNAs) using candidate gene and genome wide approaches and across biobehavioral systems (neurobehavior, cry acoustics and neuroendocrine). Despite limitations, studies support future work on molecular processes in placental genes related to neurodevelopmental trajectories including implications for intervention.

Prenatal substance exposure and offspring development: Does DNA methylation play a role?

The period of in utero development is one of the most critical windows during which adverse conditions and exposures may influence the growth and development of the fetus as well as its future postnatal health and behavior. Maternal substance use during pregnancy remains a relatively common but nonetheless hazardous in utero exposure. For example, previous epidemiological studies have associated prenatal substance exposure with reduced birth weight, poor developmental and psychological outcomes, and increased risk for diseases and behavioral disorders (e.g., externalizing behaviors like ADHD, conduct disorder, and substance use) later in life. Researchers are now learning that many of the mechanisms whereby adverse in utero exposures may affect key pathways crucial for proper fetal growth and development are epigenetic in nature, with the majority of work in humans considering DNA methylation specifically. This review will explore the research to date on epigenetic alterations tied to maternal substance use during pregnancy and will also discuss the possible role of DNA methylation in the robust relationship between maternal substance use and later behavioral and developmental sequelae in offspring.

Prenatal Depression and Infant Temperament: The Moderating Role of Placental Gene Expression

Prior research has demonstrated the link between maternal depression during pregnancy (i.e., prenatal depression) and increased neurodevelopmental dysregulation in offspring. However, little is known about the roles of key hypothalamic-pituitary axis regulatory genes in the placenta modulating this association. This study will examine whether placental gene expression levels of 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2), glucocorticoid receptor (NR3C1), and mineralocorticoid receptor (NR3C2) can help elucidate the underlying mechanisms linking prenatal depression to infant temperament, particularly in infants with high negativity and low emotion regulation. Stored placenta tissues (N = 153) were used to quantify messenger ribonucleic acid levels of HSD11B2, NR3C1, and NR3C2. Assessments of prenatal depression and infant temperament at 6 months of age were ascertained via maternal report. Results found that prenatal depression was associated with increased Negative Affectivity (p < .05) after controlling for postnatal depression and psychosocial characteristics. Furthermore, the association between prenatal depression and Negative Affectivity was moderated by gene expression levels of HSD11B2, NR3C1, and NR3C2 such that greater gene expression significantly lessened the association between prenatal depression and Negative Affectivity. Our findings suggest that individual differences in placental gene expression may be used as an early marker of susceptibility or resilience to prenatal adversity.

Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

The increasing prevalence of neurodevelopmental disorders, especially autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD), calls for more research into the identification of etiologic and risk factors. The Developmental Origin of Health and Disease (DOHaD) hypothesizes that the environment during fetal and childhood development affects the risk for many chronic diseases in later stages of life, including neurodevelopmental disorders. Epigenetics, a term describing mechanisms that cause changes in the chromosome state without affecting DNA sequences, is suggested to be the underlying mechanism, according to the DOHaD hypothesis. Moreover, many neurodevelopmental disorders are also related to epigenetic abnormalities. Experimental and epidemiological studies suggest that exposure to prenatal environmental toxicants is associated with neurodevelopmental disorders. In addition, there is also evidence that environmental toxicants can result in epigenetic alterations, notably DNA methylation. In this review, we first focus on the relationship between neurodevelopmental disorders and environmental toxicants, in particular maternal smoking, plastic-derived chemicals (bisphenol A and phthalates), persistent organic pollutants, and heavy metals. We then review studies showing the epigenetic effects of those environmental factors in humans that may affect normal neurodevelopment.

Medical morbidities and DNA methylation of NR3C1 in preterm infants

BACKGROUND

Although there are no accepted "normal" levels of circulating cortisol in preterm infants, critically ill preterm infants show lower cortisol levels than healthy preterm infants. The regulation of cortisol reactivity by epigenetic changes in glucocorticoid receptor gene (NR3C1) expression has been demonstrated. This study aims to examine the relationship between medical morbidities in preterm infants and DNA methylation of NR3C1.

METHODS

Pyrosequencing was used to determine DNA methylation in CpG sites 1-4 of promoter region 1F of NR3C1. Cluster analysis placed 67 preterm infants born <1,500 g into groups based on medical morbidities. The DNA methylation pattern was compared across groups.

RESULTS

Cluster analysis identified a high medical risk cluster and a low medical risk cluster. A Mann-Whitney U-test showed lower methylation at CpG1 for infants in the high-risk group (M = 0.336, SE = 0.084) than infants in the low-risk group (M = 0.617, SE = 0.109, P = 0.032). The false discovery rate was low (q = 0.025). Cohen's D effect size was moderate (0.525).

CONCLUSION

Decreased DNA methylation of CpG1 of NR3C1 in high-risk infants may allow for increased binding of transcription factors involved in the stress response, repair and regulation of NR3C1. This may ensure healthy growth in high-risk preterm infants over increasing cortisol levels.

Contextual adversity, telomere erosion, pubertal development, and health: Two models of accelerated aging, or one?

Two independent lines of inquiry suggest that growing up under conditions of contextual adversity (e.g., poverty and household chaos) accelerates aging and undermines long-term health. Whereas work addressing the developmental origins of health and disease highlights accelerated-aging effects of contextual adversity on telomere erosion, that informed by an evolutionary analysis of reproductive strategies highlights such effects with regard to pubertal development (in females). That both shorter telomeres early in life and earlier age of menarche are associated with poor health later in life raises the prospect, consistent with evolutionary life-history theory, that these two bodies of theory and research are tapping into the same evolutionary–developmental process whereby longer term health costs are traded off for increased probability of reproducing before dying via a process of accelerated aging. Here we make the case for such a claim, while highlighting biological processes responsible for these effects, as well as unknowns in the epigenetic equation that might instantiate these contextually regulated developmental processes.

Introduction to the Special Section on Epigenetics

Epigenetics provides the opportunity to revolutionize our understanding of the role of genetics and the environment in explaining human behavior, although the use of epigenetics to study human behavior is just beginning. In this introduction, the authors present the basics of epigenetics in a way that is designed to make this exciting field accessible to a wide readership. The authors describe the history of human behavioral epigenetic research in the context of other disciplines and graphically illustrate the burgeoning of research in the application of epigenetic methods and principles to the study of human behavior. The role of epigenetics in normal embryonic development and the influence of biological and environmental factors altering behavior through epigenetic mechanisms and developmental programming are discussed. Some basic approaches to the study of epigenetics are reviewed. The authors conclude with a discussion of challenges and opportunities, including intervention, as the field of human behavioral epigenetics continue to grow.