Elisabeth Conradt

The roles of DNA methylation of NR3C1 and 11β-HSD2 and exposure to maternal mood disorder in utero on newborn neurobehavior

Exposure to maternal mood disorder in utero may program infant neurobehavior via DNA methylation of the glucocorticoid receptor (NR3C1) and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD-2), two placental genes that have been implicated in perturbations of the hypothalamic pituitary adrenocortical (HPA) axis. We tested the relations among prenatal exposure to maternal depression or anxiety, methylation of exon 1F of NR3C1 and 11β-HSD-2, and newborn neurobehavior. Controlling for relevant covariates, infants whose mothers reported depression during pregnancy and showed greater methylation of placental NR3C1 CpG2 had poorer self-regulation, more hypotonia, and more lethargy than infants whose mothers did not report depression. On the other hand, infants whose mothers reported anxiety during pregnancy and showed greater methylation of placental 11β-HSD-2 CpG4 were more hypotonic compared with infants of mothers who did not report anxiety during pregnancy. Our results support the fetal programming hypothesis and suggest that fetal adjustments to cues from the intrauterine environment, in this case an environment that could be characterized by increased exposure to maternal cortisol, may lead to poor neurodevelopmental outcomes.

Poverty, Problem Behavior, and Promise Differential Susceptibility Among Infants Reared in Poverty

Do infants reared in poverty exhibit certain physiological traits that make them susceptible to the positive and negative features of their caregiving environment? Guided by theories of differential susceptibility and biological sensitivity to context, we evaluated whether high baseline respiratory sinus arrhythmia (RSA) operates as a susceptibility factor among infants reared in poverty (N = 73). Baseline RSA at 5 months, the quality of the attachment relationship at 17 months, and the interaction of these two factors were included in our models as predictors of problem behavior at 17 months. Consistent with theory, results showed no significant differences in problem behavior among infants with low baseline RSA; however, infants with high baseline RSA exhibited the lowest levels of problem behavior if reared in an environment that fostered security, and they exhibited the highest levels of problem behavior if reared in an environment that fostered disorganization. These results have important implications for the psychological health of infants living in poverty.

Global and gene-specific DNA methylation across multiple tissues in early infancy: implications for children's health research

An increasing number of population studies are assessing epigenetic variation in relation to early‐life outcomes in tissues accessible to epidemiologic researchers. Epigenetic mechanisms are highly tissue specific, however, and it is unclear whether the variation observed in one of the tissue types is representative of other sources or whether the variation in DNA methylation is distinct, reflecting potential functional differences across tissues. To assess relations between DNA methylation in various samples from newborns and children in early infancy, we measured promoter or gene‐body DNA methylation in matched term placenta, cord blood, and 3–6 mo saliva samples from 27 unrelated infants enrolled in the Rhode Island Child Health Study. We investigated 7 gene loci (KLF15, NR3C1, LEP, DEPTOR, DDIT4, HSD11B2, and CEBPB) and global methylation, using repetitive region LINE‐1 and ALUYb8 sequences. We observed a great degree of interlocus, intertissue, and interindividual epigenetic variation in most of the analyzed loci. In correlation analyses, only cord blood NR3C1 promoter methylation correlated negatively with methylation in saliva. We conclude that placenta, cord blood, and saliva cannot be used as a substitute for one another to evaluate DNA methylation at these loci during infancy. Each tissue has a unique epigenetic signature that likely reflects their differential functions. Future studies should consider the uniqueness of these features, to improve epigenetic biomarker discovery and translation.—Armstrong, D. A., Lesseur, C., Conradt, E., Lester, B. M., Marsit, C. J. Global and gene‐specific DNA methylation across multiple tissues in early infancy: implications for childrens health research. FASEB J. 28, 2088–2097 (2014). www.fasebj.org

The Contributions of Maternal Sensitivity and Maternal Depressive Symptoms to Epigenetic Processes and Neuroendocrine Functioning

This study tested whether maternal responsiveness may buffer the child to the effects of maternal depressive symptoms on DNA methylation of NR3C1, 11β-HSD2, and neuroendocrine functioning. DNA was derived from buccal epithelial cells and prestress cortisol was obtained from the saliva of 128 infants. Mothers with depressive symptoms who were more responsive and who engaged in more appropriate touch during face-to-face play had infants with less DNA methylation of NR3C1 and 11β-HSD2 compared to mothers with depressive symptoms who were also insensitive. The combination of exposure to maternal depressive symptoms and maternal sensitivity was related to the highest prestress cortisol levels, whereas exposure to maternal depressive symptoms and maternal insensitivity was related to the lowest prestress cortisol levels.

Epigenetic basis for the development of depression in children.

The growing field of epigenetics and human behavior affords an unprecedented opportunity to discover molecular underpinnings of mental health disorders and pave the way for the development of preventive intervention programs. Maternal depression during pregnancy is a serious public health issue and leads to a 4-fold increase in the likelihood that the child will develop depression. We describe how mood disorders, particularly depression, may be shaped by early life stress, programming, and epigenetic processes and pathways showing how these processes could lead to depression in childhood. Implications of this approach to the study of mental health disorders for preventive interventions are discussed.

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.

Prenatal Stress, Fearfulness, and the Epigenome: Exploratory Analysis of Sex Differences in DNA Methylation of the Glucocorticoid Receptor Gene

Exposure to stress in utero is a risk factor for the development of problem behavior in the offspring, though precise pathways are unknown. We examined whether DNA methylation of the glucocorticoid receptor gene, NR3C1, was associated with experiences of stress by an expectant mother and fearfulness in her infant. Mothers reported on prenatal stress and infant temperament when infants were 5 months old (n = 68). Buccal cells for methylation analysis were collected from each infant. Prenatal stress was not related to infant fearfulness or NR3C1 methylation in the sample as a whole. Exploratory sex-specific analysis revealed a trend-level association between prenatal stress and increased methylation of NR3C1 exon 1F for female, but not male, infants. In addition, increased methylation was significantly associated with greater fearfulness for females. Results suggest an experience-dependent pathway to fearfulness for female infants via epigenetic modification of the glucocorticoid receptor gene. Future studies should examine prenatal stress in a comprehensive fashion while considering sex differences in epigenetic processes underlying infant temperament.

Prenatal predictors of infant self-regulation: the contributions of placental DNA methylation of NR3C1 and neuroendocrine activity

We examined whether placental DNA methylation of the glucocorticoid receptor gene, NR3C1 was associated with self-regulation and neuroendocrine responses to a social stressor in infancy. Placenta samples were obtained at birth and mothers and their infants (n = 128) participated in the still-face paradigm when infants were 5 months old. Infant self-regulation following the still-face episode was coded and pre-stress cortisol and cortisol reactivity was assessed in response to the still-face paradigm. A factor analysis of NR3C1 CpG sites revealed two factors: one for CpG sites 1–4 and the other for sites 5–13. DNA methylation of the factor comprising NR3C1 CpG sites 5–13 was related to greater cortisol reactivity and infant self-regulation, but cortisol reactivity was not associated with infant self-regulation. The results reveal that prenatal epigenetic processes may explain part of the development of infant self-regulation.

Are epigenetic changes in the intrauterine environment related to newborn neurobehavior

Advances in the developmental origins of chronic diseases suggest that there are multiple environmental influences linked to normal variations in fetoplacental development [1]. The mechanism of this plasticity is thought to be through fetal programming involving epigenetic processes that alter gene expression and permanently set pathways linked to disease. A key question in the burgeoning field of human behavioral epigenetics is whether similar mechanisms can explain the development of behavioral ‘diseases’, in particular, mental health disorders [2]. However, the study of how variations in the intrauterine environment trigger epigenetic modifications that alter behavioral development is virtually uncharted territory. A good place to start is the neurobehavior of the newborn infant. It is well known that the postnatal environment has a substantial influence on child development [3,4]. By focusing on newborn neurobehavioral phenotypes, we have an opportunity to hone in on the role of the prenatal period before postnatal environmental factors come into play. In addition, newborn neurobehavior may predict long-term developmental outcome, allowing the identification of individual infants most likely to suffer mental illness and the pursuit of interventions to prevent or ameliorate later deficits. Focusing on the epigenetics of newborn neurobehavior could provide the molecular context for individual differences in neurobehavior as well as an understanding of children’s responses to the postnatal environment – that is, why some infants are more vulnerable or susceptible to poor developmental outcome than others. Newborn neurobehavior can be quantified with the NNNS (NICU Network Neurobehavioral Scale), a well-established evaluation that includes neurological and behavioral measures and indicators of stress [5] and has been shown to predict behavior problems, school readiness, and IQ through 4.5 years [6]. Here, we describe a series of studies relating epigenetic changes in placental genes and the NNNS in a sample of several hundred term, healthy infants who vary in physical growth, born to mothers with uncomplicated medical histories [7]. The placenta provides an ideal fetal record of the intrauterine environment and alterations to its function through epigenetic processes that could affect newborn neurobehavior [8]. The placenta modulates the fetal environment and has been described as a ‘third brain’ that links the developing fetal brain and the mature maternal brain, and is thus a sensitive functional tissue to understand the prenatal environment’s effects on neurobehavior [9]. The neuroendocrine system, in particular, programming of the HPA axis is a good model for the exploration of epigenetic effects on placental genes and newborn neurobehavior. This is a well-studied system that includes an extensive literature on cortisol reactivity and the development of mental health disorders [10] and is known to be an active system within placental tissue [11]. In the placenta, 11β-HSD-2 is responsible for the inactivation of maternal cortisol. Increased DNA methylation of 11β-HSD-2 Barry M Lester

Prenatal Substance Exposure: Neurobiologic Organization at 1 Month

OBJECTIVE To examine the autonomic nervous system and neurobehavioral response to a sustained visual attention challenge in 1-month-old infants with prenatal substance exposure. STUDY DESIGN We measured heart rate, respiratory sinus arrhythmia, and neurobehavior during sustained visual orientation tasks included in the Neonatal Intensive Care Unit Network Neurobehavioral Scale in 1129 1-month-old infants with prenatal substance exposure. Four groups were compared: infants with prenatal cocaine and opiate exposure, infants with cocaine exposure, infants with opiate exposure, and infants with exposure to other substances (ie, alcohol, marijuana, and tobacco). RESULTS The infants with prenatal exposure to both cocaine and opiates had the highest heart rates and lowest levels of respiratory sinus arrhythmia during a sustained visual attention challenge compared with the other 3 groups. Infants with prenatal cocaine and opiate exposure had poorer quality of movement and more hypertonicity during the Neonatal Intensive Care Unit Network Neurobehavioral Scale examination. They also had more nonoptimal reflexes and stress/abstinence signs compared with infants with prenatal exposure to cocaine only and those with prenatal exposure to alcohol, tobacco, and marijuana. CONCLUSION Problems with arousal regulation were identified in infants with prenatal substance exposure. Autonomic dysregulation has been implicated as a mechanism by which these difficulties occur. Our results suggest that infants with prenatal exposure to both cocaine and opiates have the greatest autonomic response to the challenge of a sustained visual attention task, possibly putting these infants at risk for problems associated with physiologic and behavioral regulation, a necessary prerequisite for early learning.