Sex differences in epigenetic mechanisms may underlie risk and resilience for mental health disorders

Addressing Psychosocial Care Needs in Women with Peripheral Artery Disease

PURPOSE OF REVIEW

Peripheral artery disease (PAD) is a growing global epidemic. Women with PAD are at elevated risk of experiencing psychosocial stressors that influence the diagnosis, management, and course of their illness due to unique sex- and gender-based factors.

RECENT FINDINGS

We review existing evidence for increased psychosocial risk in women with PAD with a focus on mood disorders, chronic stress, pain experiences, substance use disorders, health behaviors and illness perceptions, and healthcare access. We discuss how these factors exacerbate PAD symptomatology and lead to adverse outcomes. Existing gaps in women's vascular care are reviewed and potential solutions to bridge these gaps through psychosocial care integration are proposed. Current care paradigms for women's vascular care do not adequately screen for and address psychosocial comorbidities. Clinician education, integration of evidence-based psychological care strategies, implementation of workflows for the management of individuals with PAD and mental health comorbidities, reform to reimbursement structures, and further advocacy are needed in this space. This review provides a construct for integrated behavioral health care for women with PAD and advocates for further integration of care.

Extensive evaluation of DNA methylation of functional elements in the murine Fkbp5 locus using high-accuracy DNA methylation measurement via targeted bisulfite sequencing

FKBP5 is an important stress-regulatory gene implicated in stress-related psychiatric diseases. Single nucleotide polymorphisms of the FKBP5 gene were shown to interact with early life stress to alter the glucocorticoid-related stress response and moderate disease risk. Demethylation of cytosine-phosphate-guanine-dinucleotides (CpGs) in regulatory glucocorticoid-responsive elements was suggested to be the mediating epigenetic mechanism for long-term stress effects, but studies on Fkbp5 DNA methylation (DNAm) in rodents are so far limited. We evaluated the applicability of high-accuracy DNA methylation measurement via targeted bisulfite sequencing (HAM-TBS), a next-generation sequencing-based technology, to allow a more in-depth characterisation of the DNA methylation of the murine Fkbp5 locus in three different tissues (blood, frontal cortex and hippocampus). In this study, we not only increased the number of evaluated sites in previously described regulatory regions (in introns 1 and 5), but also extended the evaluation to novel, possibly relevant regulatory regions of the gene (in intron 8, the transcriptional start site, the proximal enhancer and CTCF-binding sites within the 5'UTR). We here describe the assessment of HAM-TBS assays for a panel of 157 CpGs with possible functional relevance in the murine Fkbp5 gene. DNAm profiles were tissue-specific, with lesser differences between the two brain regions than between the brain and blood. Moreover, we identified DNAm changes in the Fkbp5 locus after early life stress exposure in the frontal cortex and blood. Our findings indicate that HAM-TBS is a valuable tool for broader exploration of the DNAm of the murine Fkbp5 locus and its involvement in the stress response.

Early life adversity across different cell- types in the brain

Early life adversity (ELA)- which includes physical, psychological, emotional, and sexual abuse is one of the most common predictors to diverse psychopathologies later in adulthood. As ELA has a lasting impact on the brain at a developmental stage, recent findings from the field highlighted the specific contributions of different cell types to ELA and their association with long lasting consequences. In this review we will gather recent findings describing morphological, transcriptional and epigenetic alterations within neurons, glia and perineuronal nets and their associated cellular subpopulation. The findings reviewed and summarized here highlight important mechanisms underlying ELA and point to therapeutic approaches for ELA and related psychopathologies later in life.

Depressive disorder and antidepressants from an epigenetic point of view

Depressive disorder is a complex, heterogeneous disease that affects approximately 280 million people worldwide. Environmental, genetic, and neurobiological factors contribute to the depressive state. Since the nervous system is susceptible to shifts in activity of epigenetic modifiers, these allow for significant plasticity and response to rapid changes in the environment. Among the most studied epigenetic modifications in depressive disorder is DNA methylation, with findings centered on the brain-derived neurotrophic factor gene, the glucocorticoid receptor gene, and the serotonin transporter gene. In order to identify biomarkers that would be useful in clinical settings, for diagnosis and for treatment response, further research on antidepressants and alterations they cause in the epigenetic landscape throughout the genome is needed. Studies on cornerstone antidepressants, such as selective serotonin reuptake inhibitors, selective serotonin and norepinephrine reuptake inhibitors, norepinephrine, and dopamine reuptake inhibitors and their effects on depressive disorder are available, but systematic conclusions on their effects are still hard to draw due to the highly heterogeneous nature of the studies. In addition, two novel drugs, ketamine and esketamine, are being investigated particularly in association with treatment of resistant depression, which is one of the hot topics of contemporary research and the field of precision psychiatry.

Adolescent idiopathic scoliosis : a review of aetiological theories of a multifactorial disease

Adolescent idiopathic scoliosis (AIS), defined by an age at presentation of 11 to 18 years, has a prevalence of 0.47% and accounts for approximately 90% of all cases of idiopathic scoliosis. Despite decades of research, the exact aetiology of AIS remains unknown. It is becoming evident that it is the result of a complex interplay of genetic, internal, and environmental factors. It has been hypothesized that genetic variants act as the initial trigger that allow epigenetic factors to propagate AIS, which could also explain the wide phenotypic variation in the presentation of the disorder. A better understanding of the underlying aetiological mechanisms could help to establish the diagnosis earlier and allow a more accurate prediction of deformity progression. This, in turn, would prompt imaging and therapeutic intervention at the appropriate time, thereby achieving the best clinical outcome for this group of patients. Cite this article: Bone Joint J 2022;104-B(8):915-921.

Sex differences in the genetic regulation of the blood transcriptome response to glucocorticoid receptor activation

Substantial sex differences have been reported in the physiological response to stress at multiple levels, including the release of the stress hormone, cortisol. Here, we explore the genomic variants in 93 females and 196 males regulating the initial transcriptional response to cortisol via glucocorticoid receptor (GR) activation. Gene expression levels in peripheral blood were obtained before and after GR-stimulation with the selective GR agonist dexamethasone to identify differential expression following GR-activation. Sex stratified analyses revealed that while the transcripts responsive to GR-stimulation were mostly overlapping between males and females, the quantitative trait loci (eQTLs) regulation differential transcription to GR-stimulation was distinct. Sex-stratified eQTL SNPs (eSNPs) were located in different functional genomic elements and sex-stratified transcripts were enriched within postmortem brain transcriptional profiles associated with Major Depressive Disorder (MDD) specifically in males and females in the cingulate cortex. Female eSNPs were enriched among SNPs linked to MDD in genome-wide association studies. Finally, transcriptional sensitive genetic profile scores derived from sex-stratified eSNPS regulating differential transcription to GR-stimulation were predictive of depression status and depressive symptoms in a sex-concordant manner in a child and adolescent cohort (n = 584). These results suggest the potential of eQTLs regulating differential transcription to GR-stimulation as biomarkers of sex-specific biological risk for stress-related psychiatric disorders.

Neurodevelopmental Disabilities in Canadian Children: Prevalence Data from the National Longitudinal Study of Children and Youth

Aim Using population surveys of chronic health conditions, the present study aimed to examine changing trends in the prevalence of neurodevelopmental disabilities (NDD) with age and determine population-based estimates of prevalence and census-based estimates of absolute numbers of affected children.

Methods We analyzed data from three cycles (1994–1999) of Canada's National Longitudinal Survey of Children and Youth (NLSCY) (Statistics Canada Survey).

Results Cross-sectional prevalence rates for chronic NDD in children from birth to 15 years across cycle 1 to 3 of the NLSCY show an increasing trend over the years from 1994 to 1999. Population-based estimates were also calculated from census data. Weighted prevalence rates for four conditions in children aged birth to 15 years increased across the three cycles, except for cerebral palsy. Prevalence estimates in cycle 3 were: epilepsy 5.26/1,000 (95% confidence interval [CI]: 5.01, 5.52), cerebral palsy 2.81/1,000 (95% CI: 2.62, 2.99), intellectual disability 4.77/1,000 (95% CI: 4.53, 5.02), and learning disability 57.06/1,000 (95% CI, 56.36, 57.76). A male gender preponderance was noted for each NDD using logistic regression.

Interpretation Prevalence rates of NDD in Canadian children show an incremental trend across three cycles in four conditions covered in the survey. The changing trends over the three cycles are discussed.

Reconsidering interactive resilience processes in mental health: Implications for child and youth services

Research consistently demonstrates resilience as an interactive process, drawing on personal assets together with relational and contextual resources, to support improved outcomes in contexts of nonnormative adversity. What remains unclear are the dynamics of this process and what drives it. This article draws on a prior scoping review of the literature to conceptually explore the positioning of the individual within this dynamic interplay of risks, resilience, and sociocultural context as it pertains to child and youth mental health. The paper begins by summarizing findings from this scoping review, highlighting core resilience elements and processes. These are then considered in relational to the global meaning theory, situating meaning-making as a key mechanism that mediates the interaction between individuals and their ecologies. Drawing on the literature, this article considers how this interaction shapes the particular ways in which resilience then manifests itself in the lives of individuals and becomes available as a resource to assist in the promotion of mental health.

Distinctions between sex and time in patterns of DNA methylation across puberty

BACKGROUND

There are significant sex differences in human physiology and disease; the genomic sources of these differences, however, are not well understood. During puberty, a drastic neuroendocrine shift signals physical changes resulting in robust sex differences in human physiology. Here, we explore how shifting patterns of DNA methylation may inform these pathways of biological plasticity during the pubertal transition. In this study we analyzed DNA methylation (DNAm) in saliva at two time points across the pubertal transition within the same individuals. Our purpose was to compare two domains of DNAm patterns that may inform processes of sexual differentiation 1) sex related sites, which demonstrated differences between males from females and 2) time related sites in which DNAm shifted significantly between timepoints. We further explored the correlated network structure sex and time related DNAm networks and linked these patterns to pubertal stage, assays of salivary testosterone, a reliable diagnostic of free, unbound hormone that is available to act on target tissues, and overlap with androgen response elements.

RESULTS

Sites that differed by biological sex were largely independent of sites that underwent change across puberty. Time-related DNAm sites, but not sex-related sites, formed correlated networks that were associated with pubertal stage. Both time and sex DNAm networks reflected salivary testosterone levels that were enriched for androgen response elements, with sex-related DNAm networks being informative of testosterone levels above and beyond biological sex later in the pubertal transition.

CONCLUSIONS

These results inform our understanding of the distinction between sex- and time-related differences in DNAm during the critical period of puberty and highlight a novel linkage between correlated patterns of sex-related DNAm and levels of salivary testosterone.

Neuroepigenetic signatures of age and sex in the living human brain

Age- and sex-related alterations in gene transcription have been demonstrated, however the underlying mechanisms are unresolved. Neuroepigenetic pathways regulate gene transcription in the brain. Here, we measure in vivo expression of the epigenetic enzymes, histone deacetylases (HDACs), across healthy human aging and between sexes using [¹¹C]Martinostat positron emission tomography (PET) neuroimaging (n = 41). Relative HDAC expression increases with age in cerebral white matter, and correlates with age-associated disruptions in white matter microstructure. A post mortem study confirmed that HDAC1 and HDAC2 paralogs are elevated in white matter tissue from elderly donors. There are also sex-specific in vivo HDAC expression differences in brain regions associated with emotion and memory, including the amygdala and hippocampus. Hippocampus and white matter HDAC expression negatively correlates with emotion regulation skills (n = 23). Age and sex are associated with HDAC expression in vivo, which could drive age- and sex-related transcriptional changes and impact human behavior.

Gene transcription is known to vary with age and sex, although the underlying mechanisms are unresolved. Here, the authors show that epigenetic enzymes known as HDACs, which regulate gene transcription, are increasingly expressed with age in the living human brain, with sex differences also observed.

Early life stress and the propensity to develop addictive behaviors

There is a vast literature on effects of early life manipulations in rodents much of which is aimed at investigating the long-term consequences related to emotion and cognition in adulthood. Less is known about how these manipulations affect responses reflective of alcohol (AUD) and substance (SUD) use disorders. The purpose of this paper is to review the literature of studies that employed early life manipulations and assessed behavioral responses to psychoactive substances, specifically alcohol, opiates, and stimulants, in rodents. While the findings with alcohol are more limited and mixed, studies with opiates and stimulants show strong support for the ability of these manipulations to enhance behavioral responsivity to these substances in line with epidemiological data. Some outcomes show sex differences. The mechanisms that influence these enduring changes may reflect epigenetic alterations. Several studies support a role for altered DNA methylation (and other epigenetic mechanisms) as biological responses to early environmental insults. The chemical changes induced by DNA methylation affect transcriptional activity of DNA and thus can have a long-term impact on the individual's phenotype. Such effects are particularly robust when they occur during sensitive periods of brain development (e.g., first postnatal weeks in rodents). We review this emerging literature as it relates to the known neurobiology of AUDs and SUDs and suggest new avenues of research. Such findings will have implications for the treatment and prevention of AUDs and SUDs and could provide insight into factors that support resiliency.

Prenatal Androgenization Induces Anxiety-Like Behavior in Female Rats, Associated with Reduction of Inhibitory Interneurons and Increased BDNF in Hippocampus and Cortex

Anxiety is one of the most frequent psychiatric disorders. Despite the fact that most studies describe an anxiolytic effect of testosterone, hyperandrogenemia in mothers is assumed to be related to an increased risk of mood disorders in their offspring. An increasing body of scientific evidence suggests that an altered expression of interneuronal markers of the hippocampus may be the cause of anxiety. The aim of this study was to examine the influence of maternal hyperandrogenemia on behavioral parameters of anxiety-like behavior, neuropeptide Y (NPY) and parvalbumin (PV) expression in the hippocampus, and the level of the brain-derived neurotrophic factor (BDNF) in the hippocampus and cerebral cortex. Pregnant female Wistar albino rats were treated with testosterone undecanoate on the 20th day of gestation. Anxiety-like behavior in adult female offspring was evaluated by the elevated plus maze test and the open field. The number of PV and NPY immunoreactive cells in the hippocampus was determined immunohistochemically. The level of BDNF expression in the hippocampus and cerebral cortex was analyzed with the Western blot test. Prenatal hyperandrogenization increased anxiety-like behavior in female offspring and decreased expression of NPY+ and PV+ in the CA1 region of the hippocampus as compared to the control group. BDNF expression in the hippocampus and cerebral cortex of prenatally androgenized female offspring was significantly increased in comparison with the controls. Prenatal hyperandrogenization may be the cause of anxiety-like behavior in female offspring. Decrease in NPY and PV expression in the hippocampus may explain the possible mechanism of hyperandrogenization induced anxiety.

Inhibition of DNA Methylation in the Developing Rat Brain Disrupts Sexually Dimorphic Neurobehavioral Phenotypes in Adulthood

Accumulating evidence indicates a critical implication of DNA methylation in the brain development. We aim to determine whether the disruption of DNA methylation patterns in the developing brain adversely affects neurobehavioral phenotypes later in life in a sex-dependent manner. 5-Aza-2'-deoxycytidine (5-Aza), a DNA methylation inhibitor, was administered in newborn rats from postnatal day 1 to 3. Neurobehavioral outcomes were analyzed at 3 months of age. 5-Aza treatment significantly inhibited DNA methyltransferase activity and decreased global DNA methylation levels in neonatal rat brains, resulting in asymmetric growth restriction with the increased brain to body weight ratio in both male and female rats at 14 days and 3 months of age. Compared with the saline control, 5-Aza treatment significantly improved performance of male rats on the rotarod test, and 5-Aza-treated female rats demonstrated less anxiety, less depression-like behaviors, and enhanced spatial learning performance. Of importance, neonatal 5-Aza treatment eliminated the sexually dimorphic differences in several neurobehavioral tests in adult rats. In addition, 5-Aza treatment decreased promoter methylation of brain-derived neurotrophic factor (BDNF) gene and significantly increased BDNF mRNA and protein abundance in the prefrontal cortex and hippocampus of female rats in a sex-dependent manner. Thus, brain DNA methylation appears to be essential for sexual differentiations of the brain and neurobehavioral functions. Inhibition of DNA methylation in the developing brain of early life induces aberrant neurobehavioral profiles and disrupts sexually dimorphic neurobehavioral phenotypes in adulthood, of which altered BDNF signaling pathway may be an important mediator.

Environmental influences on the female epigenome and behavior

Environmental factors have long-lasting effects on brain development and behavior. One way experiences are propagated is via epigenetic modifications to the genome. Environmentally-driven epigenetic modifications show incredible brain region- and sex-specificity, and many brain regions affected are ones involved in maternal behavior. In rodent models, females are typically the primary caregiver and thus, any environmental factors that modulate the epigenotype of the mother could have consequences for her current and future offspring. Here we review evidence of the susceptibility of the female epigenome to environmental factors, with a focus on brain regions involved in maternal behavior. Accordingly, implications for interventions that target the mother's epigenome and parenting behavior are discussed.

Annual Research Review: The role of the environment in the developmental psychopathology of autism spectrum condition

BACKGROUND

Although autism spectrum condition (ASC) is strongly genetic in origin, accumulating evidence points to the critical roles of various environmental influences on its emergence and subsequent developmental course.

METHODS

A developmental psychopathology framework was used to synthesise literature on environmental factors associated with the onset and course of ASC (based on a systematic search of the literature using PubMed, PsychInfo and Google Scholar databases). Particular emphasis was placed on gene-environment interplay, including gene-environment interaction (G × E) and gene-environment correlation (rGE).

RESULTS

Before conception, advanced paternal and maternal ages may independently enhance offspring risk for ASC. Exogenous prenatal risks are evident (e.g. valproate and toxic chemicals) or possible (e.g. selective serotonin reuptake inhibitors), and processes endogenous to the materno-foeto-placental unit (e.g. maternal diabetes, enhanced steroidogenic activities and maternal immune activation) likely heighten offspring vulnerability to ASC. Folate intake is a prenatal protective factor, with a particular window of action around 4 weeks preconception and during the first trimester. These prenatal risks and protective mechanisms appear to involve G × E and potentially rGE. A variety of perinatal risks are related to offspring ASC risk, possibly reflecting rGE. Postnatal social factors (e.g. caregiver-infant interaction, severe early deprivation) during the first years of life may operate through rGE to influence the likelihood of manifesting a full ASC phenotype from a 'prodromal' phase (a proposal distinct to the discredited and harmful 'refrigerator mother hypothesis'); and later postnatal risks, after the full manifestation of ASC, shape life span development through transactions mediated by rGE. There is no evidence that vaccination is a postnatal risk for ASC.

CONCLUSIONS

Future investigations should consider the specificity of risks for ASC versus other atypical neurodevelopmental trajectories, timing of risk and protective mechanisms, animal model systems to study mechanisms underlying gene-environment interplay, large-sample genome-envirome designs to address G × E and longitudinal studies to elucidate how rGE plays out over time. Clinical and public health implications are discussed.

Neurodevelopment and ages of onset in depressive disorders

How and why do clinical depressive disorders emerge in adolescence? In this Personal View, we present a neurodevelopmental theory to address causes for adolescent onsets of clinical depressive disorders. We argue that theories should account for three perplexing aspects of depressive disorders in adolescence: the episodic nature of depression; differences between sexes in rates of depression across development; and age-differentiated onsets. We consider how theories such as psychosocial acceleration, heterochronic brain development, dual-process models, glucocorticoid vulnerability hypothesis linked to early life stress, and epigenetic and genetic susceptibility might explain some aspects of adolescent depressive disorders. We argue that some synthesis between existing theories might be needed to establish a sufficient neurodevelopmental theoretical framework to explain onsets of depressive disorders in adolescence.

Mental disorders in childhood and young adulthood among children born to women with fertility problems

STUDY QUESTION

Is the risk of hospital admission or outpatient contact for mental disorders increased in children born to women with fertility problems compared with children born to women without fertility problems?

SUMMARY ANSWER

We found an increased risk of hospital admission or outpatient contact for mental disorders in children born to women with fertility problems.

WHAT IS KNOWN ALREADY

Few studies have investigated the risk of mental disorders in children born after fertility treatment and although some studies have pointed to an increased risk, others found no association. The inconsistent results may be due to methodological constraints in many previous studies, including small sample size and short follow-up, resulting in imprecise risk estimates and lack of information on risk patterns of mental disorders in adulthood.

STUDY DESIGN, SIZE, DURATION

This nationwide retrospective register-based cohort study included all 2 412 721 children born in Denmark between 1969 and 2006. All children were followed from date of birth until date of hospital contact for a mental disorder, date of emigration, date of death or 31 December 2009, whichever occurred first.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Information concerning maternal fertility status for all children in the cohort was obtained by linkage to the Danish Infertility Cohort, which contains data on nearly all women with fertility problems in Denmark since 1963. A total of 124 269 (5%) children were born to women with fertility problems and 2 288 452 (95%) to women without fertility problems. To identify children hospitalized for a mental disorder, the cohort was linked to the Danish Psychiatric Central Research Registry. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between maternal fertility status and the risk of hospital admission or outpatient contact for various groups of mental disorders, including any mental disorder and all 11 main discharge diagnostic groups, classified according to the International Classification of Diseases, version 10.

MAIN RESULTS AND THE ROLE OF CHANCE

During a mean follow-up period of 21 years (range, 0-40 years), 168 686 (7%) children were admitted to hospital or had an outpatient contact for a mental disorder. Children born to women with fertility problems had a significantly higher risk of any mental disorder (HR 1.23; 95% CI 1.20-1.26) and for most of the 11 main discharge groups, including schizophrenia (HR 1.16; 95% CI 1.07-1.27), mood (affective) disorders (HR 1.21; 95% CI 1.15-1.28) and disorders of psychological development (HR 1.15; 95% CI 1.09-1.21) as well as the subgroup of attention-deficit/hyperactivity disorders (HR 1.36; 95% CI 1.29-1.45) compared with children born to women without fertility problems. The risk estimates did not change markedly when analyses were performed separately for mental disorders diagnosed during childhood (0-19 years) and in young adulthood (20-40 years).

LIMITATIONS, REASON FOR CAUTION

The true risk of mental disorders may be somewhat underestimated, as only severe disorders requiring hospital admission or outpatient contact were considered as events. Furthermore, we could not determine whether the increased risks observed were due to factors related to the underlying infertility or to fertility treatment procedures.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first report on mental disorders in adulthood among children born to women with fertility problems. Furthermore, we have assessed the risk of several severe mental disorders not previously studied (e.g. neurotic, stress-related and somatoform disorders and disorders of adult personality and behaviour). These important findings should be investigated further in large epidemiological studies designed to differentiate between factors related to fertility treatment and to the underlying infertility.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by internal funding from the Unit of Virus, Lifestyle and Genes at the Danish Cancer Society Research Center. All authors report no conflicts of interest.

Global and gene-specific DNA methylation alterations in the adolescent amygdala and hippocampus in an animal model of caregiver maltreatment

Epigenetic mechanisms such as DNA methylation are part of an emerging story on how early-life experiences can alter behavioral trajectories and lead to the development of disease and psychological disorders. Previous work from our laboratory has demonstrated alterations in methylation of DNA associated with the brain-derived neurotrophic factor (bdnf) gene within the amygdala and hippocampus of infant and adult rats that were repeatedly exposed to caregiver maltreatment outside the home cage during their first week of life. In the current study we examine changes in global levels of DNA methylation (5-mC) and hydroxymethylation (5-hmC), as well as gene-specific changes in methylation patterns of the candidate gene bdnf (at exons I and IV) within the adolescent amygdala and hippocampus resulting from exposure to maltreatment. While adolescent females exposed to maltreatment showed no significant alterations in global 5-mC or 5-hmC levels, examination of bdnf DNA methylation revealed that maltreated females had greater methylation of exon IV DNA in the amygdala and ventral hippocampus. While adolescent males exposed to maltreatment showed no significant alterations in bdnf DNA methylation, maltreated males had significantly higher 5-mC levels in the dorsal hippocampus and lower 5-hmC levels in the amygdala. These findings demonstrate that the effects of the early caregiving environment are detectable in the adolescent brain at the level of the epigenome, with brain-region specific and sexually-dimorphic epigenetic consequences that could have relevance to adolescent mental health and behavior.

Uncovering RNA binding proteins associated with age and gender during liver maturation

In the present study, we perform an association analysis focusing on the expression changes of 1344 RNA Binding proteins (RBPs) as a function of age and gender in human liver. We identify 88 and 45 RBPs to be significantly associated with age and gender respectively. Experimental verification of several of the predicted associations in mice confirmed our findings. Our results suggest that a small fraction of the gender-associated RBPs (~40%) are expressed higher in males than females. Altogether, these observations show that several of these RBPs are important and conserved regulators in maintaining liver function. Further analysis of the protein interaction network of RBPs associated with age and gender based on the centrality measures like degree, betweenness and closeness revealed that several of these RBPs might be prominent players in aging liver and impart gender specific alterations in gene expression via the formation of protein complexes. Indeed, both age and gender-associated RBPs in liver were found to show significantly higher clustering coefficients and network centrality measures compared to non-associated RBPs. The compendium of RBPs and this study will help us gain insight into the role of post-transcriptional regulatory molecules in aging and gender specific expression of genes.

Elevated fetal steroidogenic activity in autism

Autism affects males more than females, giving rise to the idea that the influence of steroid hormones on early fetal brain development may be one important early biological risk factor. Utilizing the Danish Historic Birth Cohort and Danish Psychiatric Central Register, we identified all amniotic fluid samples of males born between 1993 and 1999 who later received ICD-10 (International Classification of Diseases, 10th Revision) diagnoses of autism, Asperger syndrome or PDD-NOS (pervasive developmental disorder not otherwise specified) (n=128) compared with matched typically developing controls. Concentration levels of Δ4 sex steroids (progesterone, 17α-hydroxy-progesterone, androstenedione and testosterone) and cortisol were measured with liquid chromatography tandem mass spectrometry. All hormones were positively associated with each other and principal component analysis confirmed that one generalized latent steroidogenic factor was driving much of the variation in the data. The autism group showed elevations across all hormones on this latent generalized steroidogenic factor (Cohen's d=0.37, P=0.0009) and this elevation was uniform across ICD-10 diagnostic label. These results provide the first direct evidence of elevated fetal steroidogenic activity in autism. Such elevations may be important as epigenetic fetal programming mechanisms and may interact with other important pathophysiological factors in autism.

Age- and Sex-Dependent Changes in Androgen Receptor Expression in the Developing Mouse Cortex and Hippocampus

During the perinatal period, male mice are exposed to higher levels of testosterone (T) than females, which promotes sexual dimorphism in their brain structures and behaviors. In addition to acting via estrogen receptors after being locally converted into estradiol by aromatase, T also acts directly through androgen receptor (AR) in the brain. Therefore, we hypothesized that AR expression in the developing mouse cortex and hippocampus was sexually dimorphic. To test our hypothesis, we measured and determined AR mRNA and protein levels in mouse cortex/hippocampus collected on the day of birth (PN0) and 7 (PN7), 14 (PN14), and 21 (PN21) days after birth. We demonstrated that, as age advanced, AR mRNA levels increased in the cortex/hippocampus of both sexes but showed no sex difference. Two AR proteins, the full-length (110 kDa) and a smaller isoform (70 kDa), were detected in the developing mouse cortex/hippocampus with an age-dependent increase in protein levels of both AR isoforms at PN21 and a transient masculine increase in expression of the full-length AR protein on PN7. Thus, we conclude that the postnatal age and sex differences in AR protein expression in combination with the sex differences in circulating T may cause sexual differentiation of the mouse cortex/hippocampus.

Litter and sex effects on maternal behavior and DNA methylation of the Nr3c1 exon 17 promoter gene in hippocampus and cerebellum

Early life events can alter gene expression through DNA methylation. The methylation status of the exon 17 promoter of the glucocorticoid receptor (Nr3c1 gene) in hippocampus associates with frequency of pup licking. Much of this work was conducted with male rats. Because dams more frequently lick male pups, this may contribute to sex differences in phenotypes through DNA methylation. Modifying litter gender composition (LGC), in which offspring of single-sex litters are compared to mixed-sex litters, alters maternal behavior. Previously, we demonstrated that LGC and sex affected pup licking times as well as anxiety and hippocampal DNA methylation of the Nr3c1 exon 17 promoter gene in adolescence. Now, we expand upon this work by examining effects in cerebellum and measuring mRNA levels. We also re-assessed DNA methylation in hippocampus using pyrosequencing and re-analyzed pup licking with the more commonly used frequency measure. Litters, culled to 8 pups on postnatal day 1 (PN1), were assigned to one of three conditions: all male (n = 10), all female (n = 12), or half of each sex (n = 20). Licking was rated on PN4, 7, and 10. On PN35, hippocampal and cerebellar samples were obtained. Single-sex males were licked the least and mixed-sex males, the most. Hippocampal Nr3c1 mRNA levels were lowest in mixed females with no LGC or Sex effects in DNA methylation. Cerebellar DNA methylation levels were lowest in mixed males with no effect on mRNA levels. Maternal pup licking associated with DNA methylation of the Nr3c1 exon 17 promoter gene in cerebellum and with hippocampal mRNA.

Brain region- and sex-specific alterations in DAMGO-stimulated [(35) S]GTPγS binding in mice with Oprm1 A112G

The A118G single nucleotide polymorphism (SNP) of the human μ-opioid receptor (MOPR) gene (OPRM1) was associated with heightened dopamine release by alcohol intake, better treatment outcome for nicotine and alcohol addiction, and reduced analgesic responses to morphine. A mouse model that possesses the equivalent substitution (A112G) in the mouse MOPR gene (OPRM1) was generated to delineate the mechanisms of the impact of the SNP. Mice homozygous for the G112 allele (G/G) displayed lower morphine-induced antinociception than mice homozygous for the A112 allele (A/A), similar to the results in humans. In this study, we examined whether A112G SNP affected MOPR-mediated G protein activation in the mouse model. We compared A/A and G/G mice in the MOPR-selective agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO)-stimulated [(35) S]GTPγS binding in brain regions by autoradiography. When the data of males and females were combined, G/G mice exhibited lower DAMGO-stimulated [(35) S]GTPγS binding in the ventral tegmental area than A/A mice, in accord with the previously reported reduced morphine-induced hyperactivity and locomotor sensitization in G/G mice. In the nucleus accumbens (NAc) core, female G/G mice displayed lower DAMGO-stimulated [(35) S]GTPγS binding than female A/A mice, which is consistent with the previously reported deficiency in morphine-induced conditioned place preference in female G/G mice. In G/G mice, males showed higher DAMGO-stimulated [(35) S]GTPγS binding than females in the cingulate cortex, caudate putamen, NAc core, thalamus and amygdala. Thus, A112G SNP affects DAMGO-stimulated [(35) S]GTPγS binding in region- and sex-specific manners.

Epigenetic mechanisms in pubertal brain maturation

Puberty is a critical period of development during which the reemergence of gonadotropin-releasing hormone secretion from the hypothalamus triggers a cascade of hormone-dependent processes. Maturation of specific brain regions including the prefrontal cortex occurs during this window, but the complex mechanisms underlying these dynamic changes are not well understood. Particularly, the potential involvement of epigenetics in this programming has been under-examined. The epigenome is known to guide earlier stages of development, and it is similarly poised to regulate vital pubertal-driven brain maturation. Further, as epigenetic machinery is highly environmentally responsive, its involvement may also lend this period of growth to greater vulnerability to external insults, resulting in reprogramming and increased disease risk. Importantly, neuropsychiatric diseases commonly present in individuals during or immediately following puberty, and environmental perturbations including stress may precipitate disease onset by disrupting the normal trajectory of pubertal brain development via epigenetic mechanisms. In this review, we discuss epigenetic processes involved in pubertal brain maturation, the potential points of derailment, and the importance of future studies for understanding this dynamic developmental window and gaining a better understanding of neuropsychiatric disease risk.

Sex differences in the human peripheral blood transcriptome

BACKGROUND

Genomes of men and women differ in only a limited number of genes located on the sex chromosomes, whereas the transcriptome is far more sex-specific. Identification of sex-biased gene expression will contribute to understanding the molecular basis of sex-differences in complex traits and common diseases.

RESULTS

Sex differences in the human peripheral blood transcriptome were characterized using microarrays in 5,241 subjects, accounting for menopause status and hormonal contraceptive use. Sex-specific expression was observed for 582 autosomal genes, of which 57.7% was upregulated in women (female-biased genes). Female-biased genes were enriched for several immune system GO categories, genes linked to rheumatoid arthritis (16%) and genes regulated by estrogen (18%). Male-biased genes were enriched for genes linked to renal cancer (9%). Sex-differences in gene expression were smaller in postmenopausal women, larger in women using hormonal contraceptives and not caused by sex-specific eQTLs, confirming the role of estrogen in regulating sex-biased genes.

CONCLUSIONS

This study indicates that sex-bias in gene expression is extensive and may underlie sex-differences in the prevalence of common diseases.

Sex differences in DNA methylation may contribute to risk of PTSD and depression: a review of existing evidence

There are well-established sex differences in the prevalence of certain mental disorders. Work in animal models has provided us with an emerging understanding of the role that epigenetic factors play in establishing sex differences in the brain during development. Similarly, work in animal models, and a more limited but growing literature based on human studies, has demonstrated that DNA methylation (DNAm) changes occur in response to environmental stress, with some of these occurring in a sex-specific manner. In this review, we explore whether DNAm plays a role in contributing to the observed sex differences in prevalence of mental disorders in which stress contributes significantly to their etiologies, specifically posttraumatic stress disorder (PTSD) and depression. We propose that investigating sex differences in DNAm among genes known to influence brain development may help to shed light on the sexually dimorphic risk for, or resilience to, developing PTSD and depression.

Exposure to caregiver maltreatment alters expression levels of epigenetic regulators in the medial prefrontal cortex

Quality of maternal care experienced during infancy is a key factor that can confer vulnerability or resilience to psychiatric disorders later in life. Research continues to indicate that early-life experiences can affect developmental trajectories through epigenetic alterations capable of affecting gene regulation and neural plasticity. Previously, our lab has shown that experiences within an adverse caregiving environment (i.e. maltreatment) produce aberrant DNA methylation patterns at various gene loci in the medial prefrontal cortex (mPFC) of developing and adult rats. This study aimed to determine whether caregiver maltreatment likewise affects expression levels of several genes important in regulating DNA methylation patterns (Dnmt1, Dnmt3a, MeCP2, Gadd45b, and Hdac1). While we observed minimal changes in gene expression within the mPFC of developing rats, we observed expression changes for all genes in adult animals. Specifically, exposure to maltreatment produced a significant decrease in mRNA levels of all epigenetic regulators in adult males and a significant decrease in Gadd45b in adult females. Our results here provide further empirical support for the long-term and sex-specific epigenetic consequences of caregiver maltreatment on the mPFC.

Influence of temperament and character on resilience

OBJECTIVE

The purpose of this study was to examine the influence of temperament and character on resilience.

METHODS

A total of 4355 participants completed two questionnaires: the Conner-Davison Resilience Scale (CD-RISC) and the Temperament and Character Inventory-Revised Short (TCI-RS). We used Pearson's correlations to evaluate the correlation between the dimensions of the TCI and the CD-RISC. To determine the most influential TCI dimension with respect to the CD-RISC, a backward multiple regression analysis was performed.

RESULTS

The resilience of both men and women was positively correlated with persistence, self-directedness, and cooperativeness. Conversely, harm avoidance was negatively correlated with resilience. In addition, reward dependence in men and self-transcendence in women were positively correlated with resilience. In the multiple regression analysis, persistence, self-directedness, and harm avoidance significantly predicted resilience after adjusting for age and gender.

CONCLUSION

This results show that social support is affected by personality, which consists of both temperament and character. High persistence and self-directedness as well as low harm avoidance are found to contribute to a better stress response.

Permanent and plastic epigenesis in neuroendocrine systems

The emerging area of neuroepigenetics has been linked to numerous mental health illnesses. Importantly, a large portion of what we know about early gene×environment interactions comes from examining epigenetic modifications of neuroendocrine systems. This review will highlight how neuroepigenetic mechanisms during brain development program lasting differences in neuroendocrine systems and how other neuroepigenetic processes remain plastic, even within the adult brain. As epigenetic mechanisms can either be stable or plastic, elucidating the mechanisms involved in reversing these processes could aid in understanding how to reverse pathological epigenetic programming.

Differential methylation of genes in the medial prefrontal cortex of developing and adult rats following exposure to maltreatment or nurturing care during infancy

Quality of maternal care in infancy is an important contributing factor in the development of behavior and psychopathology. One way maternal care could affect behavioral trajectories is through environmentally induced epigenetic alterations within brain regions known to play prominent roles in cognition, emotion regulation, and stress responsivity. Whereas such research has largely focused on the hippocampus or hypothalamus, the prefrontal cortex (PFC) has only just begun to receive attention. The current study was designed to determine whether exposure to maltreatment or nurturing care is associated with differential methylation of candidate gene loci (bdnf and reelin) within the medial PFC (mPFC) of developing and adult rats. Using a within-litter design, infant male and female rats were exposed to an adverse or nurturing caregiving environment outside their home cage for 30 min per day during the first postnatal week. Additional littermates remained with their biological caregiver within the home cage during the manipulations. We observed that infant rats subjected to caregiver maltreatment emitted more audible and ultrasonic vocalizations than littermates subjected to nurturing care either within or outside of the home cage. While we found no maltreatment-induced changes in bdnf DNA methylation present in infancy, sex-specific alterations were present in the mPFC of adolescents and adults that had been exposed to maltreatment. Furthermore, while maltreated females showed differences in reelin DNA methylation that were transient, males exposed to maltreatment and both males and females exposed to nurturing care outside the home cage showed differences in reelin methylation that emerged by adulthood. Our results demonstrate the ability of infant-caregiver interactions to epigenetically mark genes known to play a prominent role in cognition and psychiatric disorders within the mPFC. Furthermore, our data indicate the remarkable complexity of alterations that can occur, with both transient and later emerging DNA methylation differences that could shape developmental trajectories and underlie gender differences in outcomes.

Comparison of children with autism spectrum disorder with and without schizophrenia spectrum traits: gender, season of birth, and mental health risk factors

Children with autism spectrum disorder (ASD) with and without co-occurring schizophrenia spectrum traits (SST) were examined for differences in co-occurring psychiatric symptoms, background characteristics, and mental health risk factors. Participating mothers and teachers completed a DSM-IV-referenced rating scale and a background questionnaire (mothers only) describing 147 children (6-12 years) with ASD. There was a clear pattern of group differences in co-occurring psychiatric symptom severity (+SST > SST-) and background characteristics. Children with impairing SST had more mental health risk factors. Girls were more likely to be classified SST according to mothers' ratings. Children born in spring-summer were more likely to be classified non-SST by teachers' ratings. Findings provide tentative evidence that SST may be a useful marker of behavioral heterogeneity within the ASD clinical phenotype.

Male-biased autosomal effect of 16p13.11 copy number variation in neurodevelopmental disorders

Copy number variants (CNVs) at chromosome 16p13.11 have been associated with a range of neurodevelopmental disorders including autism, ADHD, intellectual disability and schizophrenia. Significant sex differences in prevalence, course and severity have been described for a number of these conditions but the biological and environmental factors underlying such sex-specific features remain unclear. We tested the burden and the possible sex-biased effect of CNVs at 16p13.11 in a sample of 10,397 individuals with a range of neurodevelopmental conditions, clinically referred for array comparative genomic hybridisation (aCGH); cases were compared with 11,277 controls. In order to identify candidate phenotype-associated genes, we performed an interval-based analysis and investigated the presence of ohnologs at 16p13.11; finally, we searched the DECIPHER database for previously identified 16p13.11 copy number variants. In the clinical referral series, we identified 46 cases with CNVs of variable size at 16p13.11, including 28 duplications and 18 deletions. Patients were referred for various phenotypes, including developmental delay, autism, speech delay, learning difficulties, behavioural problems, epilepsy, microcephaly and physical dysmorphisms. CNVs at 16p13.11 were also present in 17 controls. Association analysis revealed an excess of CNVs in cases compared with controls (OR = 2.59; p = 0.0005), and a sex-biased effect, with a significant enrichment of CNVs only in the male subgroup of cases (OR = 5.62; p = 0.0002), but not in females (OR = 1.19, p = 0.673). The same pattern of results was also observed in the DECIPHER sample. Interval-based analysis showed a significant enrichment of case CNVs containing interval II (OR = 2.59; p = 0.0005), located in the 0.83 Mb genomic region between 15.49-16.32 Mb, and encompassing the four ohnologs NDE1, MYH11, ABCC1 and ABCC6. Our data confirm that duplications and deletions at 16p13.11 represent incompletely penetrant pathogenic mutations that predispose to a range of neurodevelopmental disorders, and suggest a sex-limited effect on the penetrance of the pathological phenotypes at the 16p13.11 locus.

Placental contribution to the origins of sexual dimorphism in health and diseases: sex chromosomes and epigenetics

Sex differences occur in most non-communicable diseases, including metabolic diseases, hypertension, cardiovascular disease, psychiatric and neurological disorders and cancer. In many cases, the susceptibility to these diseases begins early in development. The observed differences between the sexes may result from genetic and hormonal differences and from differences in responses to and interactions with environmental factors, including infection, diet, drugs and stress. The placenta plays a key role in fetal growth and development and, as such, affects the fetal programming underlying subsequent adult health and accounts, in part for the developmental origin of health and disease (DOHaD). There is accumulating evidence to demonstrate the sex-specific relationships between diverse environmental influences on placental functions and the risk of disease later in life. As one of the few tissues easily collectable in humans, this organ may therefore be seen as an ideal system for studying how male and female placenta sense nutritional and other stresses, such as endocrine disruptors. Sex-specific regulatory pathways controlling sexually dimorphic characteristics in the various organs and the consequences of lifelong differences in sex hormone expression largely account for such responses. However, sex-specific changes in epigenetic marks are generated early after fertilization, thus before adrenal and gonad differentiation in the absence of sex hormones and in response to environmental conditions. Given the abundance of X-linked genes involved in placentogenesis, and the early unequal gene expression by the sex chromosomes between males and females, the role of X- and Y-chromosome-linked genes, and especially those involved in the peculiar placenta-specific epigenetics processes, giving rise to the unusual placenta epigenetic landscapes deserve particular attention. However, even with recent developments in this field, we still know little about the mechanisms underlying the early sex-specific epigenetic marks resulting in sex-biased gene expression of pathways and networks. As a critical messenger between the maternal environment and the fetus, the placenta may play a key role not only in buffering environmental effects transmitted by the mother but also in expressing and modulating effects due to preconceptional exposure of both the mother and the father to stressful conditions.

Sex and litter effects on anxiety and DNA methylation levels of stress and neurotrophin genes in adolescent rats

Maternal care variations associate with DNA methylation of the glucocorticoid receptor gene, Nr3c1, in hippocampus at a nerve-growth factor-inducible protein 1 binding site. Epigenetic regulation of brain-derived neurotrophin factor is affected by early stress. These systems contribute to anxiety and fear. Early stress has sex-dependent effects perhaps reflecting sex differences in maternal care. Altering litter gender composition affects maternal behavior and DNA methylation levels of another gene in hippocampus and nucleus accumbens (NAc). We now test if DNA methylation levels of Nr3c1, Egr1, and Bdnf differ by litter composition or sex. Rats from mixed- or single-sex litters were tested for anxiety and fear on postnatal day 35. Brain tissues were collected and analyzed using direct sequencing methods. Females showed hypermethylation of Nr3c1 of hippocampal DNA and litter composition modified sex effects on methylation of Egr1 in NAc. Few differences were seen for Bdnf. LGC modified some sex differences in behavior.

Fetal programming effects of testosterone on the reward system and behavioral approach tendencies in humans

BACKGROUND

Sex differences are present in many neuropsychiatric conditions that affect emotion and approach-avoidance behavior. One potential mechanism underlying such observations is testosterone in early development. Although much is known about the effects of testosterone in adolescence and adulthood, little is known in humans about how testosterone in fetal development influences later neural sensitivity to valenced facial cues and approach-avoidance behavioral tendencies.

METHODS

With functional magnetic resonance imaging we scanned 25 8-11-year-old children while viewing happy, fear, neutral, or scrambled faces. Fetal testosterone (FT) was measured via amniotic fluid sampled between 13 and 20 weeks gestation. Behavioral approach-avoidance tendencies were measured via parental report on the Sensitivity to Punishment and Sensitivity to Rewards questionnaire.

RESULTS

Increasing FT predicted enhanced selectivity for positive compared with negatively valenced facial cues in reward-related regions such as caudate, putamen, and nucleus accumbens but not the amygdala. Statistical mediation analyses showed that increasing FT predicts increased behavioral approach tendencies by biasing caudate, putamen, and nucleus accumbens but not amygdala to be more responsive to positive compared with negatively valenced cues. In contrast, FT was not predictive of behavioral avoidance tendencies, either through direct or neurally mediated paths.

CONCLUSIONS

This work suggests that testosterone in humans acts as a fetal programming mechanism on the reward system and influences behavioral approach tendencies later in life. As a mechanism influencing atypical development, FT might be important across a range of neuropsychiatric conditions that asymmetrically affect the sexes, the reward system, emotion processing, and approach behavior.

Contemporary Genetics for Gender Researchers

Over the past century, much of genetics was deterministic, and feminist researchers framed justified criticisms of genetics research. However, over the past two decades, genetics research has evolved remarkably and has moved far from earlier deterministic approaches. Our article provides a brief primer on modern genetics, emphasizing contemporary evidence for the complex interplay between genes and environment. We focus particularly on the role of gene–environment interactions for gender-imbalanced disorders such as depression. We review research on epigenetics, which is one mechanism by which environment influences gene expression. Modern genetics is not based on a model of genetic determinism; instead, it recognizes the complexity of genetic influences and the nuanced interplay between genes and environment across life span development. Even with the modern genetics approaches, of course, there is still room for criticism and input from gender researchers. We outline methodological and conceptual issues more generally and from a gender researcher’s perspective. We argue that, with interdisciplinary collaborations, modern genetics can be integrated into gender research and vice versa in ways that will create progress in both fields.

Experience and the developing prefrontal cortex

The prefrontal cortex (PFC) receives input from all other cortical regions and functions to plan and direct motor, cognitive, affective, and social behavior across time. It has a prolonged development, which allows the acquisition of complex cognitive abilities through experience but makes it susceptible to factors that can lead to abnormal functioning, which is often manifested in neuropsychiatric disorders. When the PFC is exposed to different environmental events during development, such as sensory stimuli, stress, drugs, hormones, and social experiences (including both parental and peer interactions), the developing PFC may develop in different ways. The goal of the current review is to illustrate how the circuitry of the developing PFC can be sculpted by a wide range of pre- and postnatal factors. We begin with an overview of prefrontal functioning and development, and we conclude with a consideration of how early experiences influence prefrontal development and behavior.

Recent advances in nutrition, genes and brain health

Molecular mechanisms underlying brain structure and function are affected by nutrition throughout the life cycle, with profound implications for health and disease. Responses to nutrition are in turn influenced by individual differences in multiple target genes. Recent advances in genomics and epigenomics are increasing understanding of mechanisms by which nutrition and genes interact. This review starts with a short account of current knowledge on nutrition-gene interactions, focusing on the significance of epigenetics to nutritional regulation of gene expression, and the roles of SNP and copy number variants (CNV) in determining individual responses to nutrition. A critical assessment is then provided of recent advances in nutrition-gene interactions, and especially energy status, in three related areas: (i) mental health and well-being, (ii) mental disorders and schizophrenia, (iii) neurological (neurodevelopmental and neurodegenerative) disorders and Alzheimer's disease. Optimal energy status, including physical activity, has a positive role in mental health. By contrast, sub-optimal energy status, including undernutrition and overnutrition, is implicated in many disorders of mental health and neurology. These actions are mediated by changes in energy metabolism and multiple signalling molecules, e.g. brain-derived neurotrophic factor (BDNF). They often involve epigenetic mechanisms, including DNA methylation and histone modifications. Recent advances show that many brain disorders result from a sophisticated network of interactions between numerous environmental and genetic factors. Personal, social and economic costs of sub-optimal brain health are immense. Future advances in understanding the complex interactions between nutrition, genes and the brain should help to reduce these costs and enhance quality of life.

Reduced expression of the μ opioid receptor in some, but not all, brain regions in mice with OPRM1 A112G

OPRM1 A118G is a common single nucleotide polymorphism (SNP) in the coding region of the human mu opioid receptor (MOPR) gene OPRM1. This SNP is associated with higher morphine doses required for postoperative analgesia as well as a variety of drug addiction phenotypes. A mouse model possessing the equivalent substitution (A112G) in the Oprm1 gene was generated to facilitate mechanistic studies. Mice homozygous for the G112 allele (G/G) displayed lower antinociception to morphine compared with those homozygous for A112 allele (A/A), similar to humans, suggesting that the mice are a good model to further characterize underlying factors contributing to phenotypes associated with this SNP. Here, we compared [³H]DAMGO binding to the MOPR in the brains of A/A and G/G mice using quantitative in vitro autoradiography. A/A mice exhibited higher [³H]DAMGO binding than G/G in the cingulate, motor, and insular cortices, nucleus accumbens core and shell, hypothalamus, thalamus, amygdala, periaqueductal gray, superficial gray of superior colliculus, and ventral tegmental area. No genotype differences were observed in somatosensory cortex, caudate putamen, and hippocampus. When males and females were examined separately, A/A mice showed higher [³H]DAMGO binding than G/G mice in more brain regions in males than in females. Radioligand binding using brain membranes also showed higher [³H]DAMGO binding in the cortex and thalamus in A/A mice than G/G mice but no genotype differences in the caudate putamen or hippocampus. Thus, the A112G SNP is associated with reduced MOPR expression in some, but not all, brain regions, and appears to have some sex differences. The elevated MOPR expression in periaqueductal gray and thalamus in A/A mice are consistent with their higher antinociceptive responses to morphine. The higher MOPR levels in nucleus accumbens and/or ventral tegmental area of A/A mice is consistent with the higher morphine-induced hyperactivity and locomotor sensitization observed in these mice. Thus, these results provide some insights into the observed decreased clinical opioid potency in humans with the A118G SNP.

Adolescent idiopathic scoliosis (AIS), environment, exposome and epigenetics: a molecular perspective of postnatal normal spinal growth and the etiopathogenesis of AIS with consideration of a network approach and possible implications for medical therapy

Genetic factors are believed to play an important role in the etiology of adolescent idiopathic scoliosis (AIS). Discordant findings for monozygotic (MZ) twins with AIS show that environmental factors including different intrauterine environments are important in etiology, but what these environmental factors may be is unknown. Recent evidence for common chronic non-communicable diseases suggests epigenetic differences may underlie MZ twin discordance, and be the link between environmental factors and phenotypic differences. DNA methylation is one important epigenetic mechanism operating at the interface between genome and environment to regulate phenotypic plasticity with a complex regulation across the genome during the first decade of life. The word exposome refers to the totality of environmental exposures from conception onwards, comprising factors in external and internal environments. The word exposome is used here also in relation to physiologic and etiopathogenetic factors that affect normal spinal growth and may induce the deformity of AIS. In normal postnatal spinal growth we propose a new term and concept, physiologic growth-plate exposome for the normal processes particularly of the internal environments that may have epigenetic effects on growth plates of vertebrae. In AIS, we propose a new term and concept pathophysiologic scoliogenic exposome for the abnormal processes in molecular pathways particularly of the internal environment currently expressed as etiopathogenetic hypotheses; these are suggested to have deforming effects on the growth plates of vertebrae at cell, tissue, structure and/or organ levels that are considered to be epigenetic. New research is required for chromatin modifications including DNA methylation in AIS subjects and vertebral growth plates excised at surgery. In addition, consideration is needed for a possible network approach to etiopathogenesis by constructing AIS diseasomes. These approaches may lead through screening, genetic, epigenetic, biochemical, metabolic phenotypes and pharmacogenomic research to identify susceptible individuals at risk and modulate abnormal molecular pathways of AIS. The potential of epigenetic-based medical therapy for AIS cannot be assessed at present, and must await new research derived from the evaluation of epigenetic concepts of spinal growth in health and deformity. The tenets outlined here for AIS are applicable to other musculoskeletal growth disorders including infantile and juvenile idiopathic scoliosis.