Epigenetic genes and emotional reactivity to daily life events: a multi-step gene-environment interaction study

Dysfunction of Small-Conductance Ca2+-Activated Potassium (SK) Channels Drives Amygdala Hyperexcitability and Neuropathic Pain Behaviors: Involvement of Epigenetic Mechanisms

Neuroplasticity in the amygdala and its central nucleus (CeA) is linked to pain modulation and pain behaviors, but cellular mechanisms are not well understood. Here, we addressed the role of small-conductance Ca2+-activated potassium (SK) channels in pain-related amygdala plasticity. The facilitatory effects of the intra-CeA application of an SK channel blocker (apamin) on the pain behaviors of control rats were lost in a neuropathic pain model, whereas an SK channel activator (NS309) inhibited pain behaviors in neuropathic rats but not in sham controls, suggesting the loss of the inhibitory behavioral effects of amygdala SK channels. Brain slice electrophysiology found hyperexcitability of CeA neurons in the neuropathic pain condition due to the loss of SK channel-mediated medium afterhyperpolarization (mAHP), which was accompanied by decreased SK2 channel protein and mRNA expression, consistent with a pretranscriptional mechanisms. The underlying mechanisms involved the epigenetic silencing of the SK2 gene due to the increased DNA methylation of the CpG island of the SK2 promoter region and the change in methylated CpG sites in the CeA in neuropathic pain. This study identified the epigenetic dysregulation of SK channels in the amygdala (CeA) as a novel mechanism of neuropathic pain-related plasticity and behavior that could be targeted to control abnormally enhanced amygdala activity and chronic neuropathic pain.

Digital phenotyping adherence, feasibility, and tolerability in outpatients with schizophrenia

Digital phenotyping has potential for use as an objective and ecologically valid form of symptom assessment in clinical trials for schizophrenia. However, there are critical methodological factors that must be addressed before digital phenotyping can be used for this purpose. The current study evaluated levels of adherence, feasibility, and tolerability for active (i.e., signal and event contingent ecological momentary assessment surveys) and passive (i.e., geolocation, accelerometry, and ambulatory psychophysiology) digital phenotyping methods recorded from smartphone and smartband devices. Participants included outpatients diagnosed with schizophrenia (SZ: n = 54) and demographically matched healthy controls (CN: n = 55), who completed 6 days of digital phenotyping. Adherence was significantly lower in SZ than CN for active recordings, but not markedly different for passive recordings. Some forms of passive recordings had lower adherence (ambulatory psychophysiology) than others (accelerometry and geolocation). Active digital phenotyping adherence was predicted by higher psychosocial functioning, whereas passive digital phenotyping adherence was predicted by education, positive symptoms, negative symptoms, and psychosocial functioning in people with SZ. Both groups found digital phenotyping methods tolerable and feasibility was supported by low frequency of invalid responding, brief survey completion times, and similar impediments to study completion. Digital phenotyping methods can be completed by individuals with SZ with good adherence, feasibility, and tolerability. Recommendations are provided for using digital phenotyping methods in clinical trials for SZ.

An investigation of genetic variability of DNA methyltransferases DNMT3A and 3B does not provide evidence for a major role in the pathogenesis of panic disorder and dimensional anxiety phenotypes

While DNA methylation patterns have been studied for a role in the pathogenesis of anxiety disorders, the role of the enzymes establishing DNA methylation-DNA methyltransferases (DNMTs)-has yet to be investigated. In an effort to investigate DNMT genotype-specific effects on dimensional anxiety traits in addition to the categorical phenotype of panic disorder, 506 panic disorder patients and 3112 healthy participants were assessed for anxiety related cognition [Agoraphobic Cognitions Questionnaire (ACQ)], anxiety sensitivity [Anxiety Sensitivity Index (ASI)] as well as pathological worry [Penn State Worry Questionnaire (PSWQ)] and genotyped for five single nucleotide polymorphisms (SNPs) in the DNMT3A (rs11683424, rs1465764, rs1465825) and DNMT3B (rs2424932, rs4911259) genes, which have previously been found associated with clinical and trait-related phenotypes. There was no association with the categorical phenotype panic disorder. However, a significant association was discerned between DNMT3A rs1465764 and PSWQ scores in healthy participants, with the minor allele conveying a protective effect. In addition, a marginally significant association between questionnaire scores (PSWQ, ASI) in healthy participants and DNMT3B rs2424932 was detected, again with the minor allele conveying a protective effect. The present results suggest a possible minor role of DNMT3A and DNMT3B gene variation in conveying resilience towards anxiety disorders. As the observed associations indicated a protective effect of two SNPs particularly with pathological worry, future studies are proposed to explore these variants in generalized anxiety disorder rather than panic disorder.

Epigenetics Underlying Susceptibility and Resilience Relating to Daily Life Stress, Work Stress, and Socioeconomic Status

Susceptibility and resilience to mental disorders result from a complex choreography of gene-environment interactions with epigenetics at the intersection of external psychological stressors and internal biological systems. Increasing awareness of the growing disease burden influenced by daily life stress ("daily hassles"), work-related stress, and low socioeconomic status (SES) has resulted in a novel interest into their underlying molecular signatures. This review offers a brief outline of psychiatric epigenetics and a comprehensive overview of recent findings exploring the relationship of various occupational stressors and DNA methylation in epigenome-wide association studies (EWAS) and in candidate gene studies including the serotonin transporter (SLC6A4; 5-HTTLPR), melatonin receptor 1A (MTNR1A), brain-derived neurotrophic factor (BDNF), tyrosine hydroxylase (TH), and the protein family of DNA methyltransferases (DNMTs). Conceptual and methodological challenges of epigenetic investigations with a special focus on gene-environment interactions are highlighted and discussed. The findings are integrated into a pathophysiological framework featuring epigenetic plasticity factors and work-related stress as a possible central detrimental component targetable by workplace interventions. Finally, the potential of dynamic epigenetic biomarkers of treatment response to pharmacotherapy or psychotherapy is expanded upon.

Effectiveness of a Pharmacogenetic Tool at Improving Treatment Efficacy in Major Depressive Disorder: A Meta-Analysis of Three Clinical Studies

Several pharmacogenetic tests to support drug selection in psychiatric patients have recently become available. The current meta-analysis aimed to assess the clinical utility of a commercial pharmacogenetic-based tool for psychiatry (Neuropharmagen^®) in the treatment management of depressive patients. Random-effects meta-analysis of clinical studies that had examined the effect of this tool on the improvement of depressive patients was performed. Effects were summarized as standardized differences between treatment groups. A total of 450 eligible subjects from three clinical studies were examined. The random effects model estimated a statistically significant effect size for the pharmacogenetic-guided prescription (d = 0.34, 95% CI = 0.11-0.56, p-value = 0.004), which corresponded to approximately a 1.8-fold increase in the odds of clinical response for pharmacogenetic-guided vs. unguided drug selection. After exclusion of patients with mild depression, the pooled estimated effect size increased to 0.42 (95% CI = 0.19-0.65, p-value = 0.004, n = 287), corresponding to an OR = 2.14 (95% CI = 1.40-3.27). These results support the clinical utility of this pharmacogenetic-based tool in the improvement of health outcomes in patients with depression, especially those with moderate-severe depression. Additional pragmatic RCTs are warranted to consolidate these findings in other patient populations.

Gene-Environment Interactions in Psychiatry: Recent Evidence and Clinical Implications

PURPOSE OF REVIEW

We identify the recent evidence for gene-by-environment interaction studies in relation to psychiatric disorders. We focus on the key genotypic data as well as environmental exposures and how they interact to predict psychiatric disorders and psychiatric symptomatology. We direct our focus on the psychiatric outcomes that were focused on by the Psychiatric Genetics Consortium.

RECENT FINDINGS

Many of the studies focus on candidate gene approaches, with most of the studies drawing upon previous literature to decide the genes of interest. Other studies used a genome-wide approach. While some studies demonstrated positive replication of previous findings, replication is still an issue within gene-by-environment interaction studies. Gene-by-environment interaction research in psychiatry globally suggests some susceptibility to environmental exposures based on genotype; however, greater clarity is needed around the idea that genetic risk may not be disorder specific.

DNA methylation of genes regulating appetite and prediction of weight loss after bariatric surgery in obese individuals

PURPOSE

Epigenetic traits are influenced by clinical variables; interaction between DNA methylation (DNAmeth) and bariatric surgery-induced weight loss has been scarcely explored. We investigated whether DNAmeth of genes encoding for molecules/hormones regulating appetite, food intake or obesity could predict successful weight outcome following Roux-en-Y gastric bypass (RYGB).

METHODS

Forty-five obese individuals with no known comorbidities were stratified accordingly to weight decrease one-year after RYGB (excess weight loss, EWL ≥ 50%: good responders, GR; EWL < 50%: worse responders, WR). DNAmeth of leptin (LEP), ghrelin (GHRL), ghrelin receptor (GHSR) and insulin-growth factor-2 (IGF2) was assessed before intervention. Single nucleotide polymorphisms of genes affecting DNAmeth, DNMT3A and DNMT3B, were also determined.

RESULTS

At baseline, type 2 diabetes was diagnosed by OGTT in 13 patients. Post-operatively, GR (n = 23) and WR (n = 22) achieved an EWL of 67.7 ± 9.6 vs 38.2 ± 9.0%, respectively. Baseline DNAmeth did not differ between GR and WR for any tested genes, even when the analysis was restricted to subjects with no diabetes. A relationship between GHRL and LEP methylation profiles emerged (r = 0.47, p = 0.001). Searching for correlation between DNAmeth of the studied genes with demographic characteristics and baseline biochemical parameters of the studied population, we observed a correlation between IGF2 methylation and folate (r = 0.44, p = 0.003). Rs11683424 for DNMT3A and rs2424913 for DNMT3B did not correlate with DNAmeth of the studied genes.

CONCLUSIONS

In severely obese subjects, the degree of DNAmeth of some genes affecting obesity and related conditions does not work as predictor of successful response to RYGB.

Distinct Expression Pattern of Epigenetic Machinery Genes in Blood Leucocytes and Brain Cortex of Depressive Patients

In major depressive disorder (MDD), altered gene expression in brain cortex and blood leucocytes may be due to aberrant expression of epigenetic machinery coding genes. Here, we explore the expression of these genes both at the central and peripheral levels. Using real-time quantitative PCR technique, we first measured expression levels of genes encoding DNA and histone modifying enzymes in the dorsolateral prefrontal cortex (DLPFC) and cingulate cortex (CC) of MDD patients (n = 24) and healthy controls (n = 12). For each brain structure, transcripts levels were compared between subject groups. In an exploratory analysis, we then compared the candidate gene expressions between a subgroup of MDD patients with psychotic characteristics (n = 13) and the group of healthy subjects (n = 12). Finally, we compared transcript levels of the candidate genes in blood leucocytes between separate samples of MDD patients (n = 17) and healthy controls (n = 16). In brain and blood leucocytes of MDD patients, we identified an overexpression of genes encoding enzymes which transfer repressive transcriptional marks: HDAC4-5-6-8 and DNMT3B in the DLPFC, HDAC2 in the CC and blood leucocytes. In the DLPFC of patients with psychotic characteristics, two genes (KAT2A and UBE2A) were additionally overexpressed suggesting a shift to a more transcriptionally permissive conformation of chromatin. Aberrant activation of epigenetic repressive systems may be involved in MDD pathogenesis both in brain tissue and blood leucocytes.

Individualized Immunological Data for Precise Classification of OCD Patients

Obsessive⁻compulsive disorder (OCD) affects about 2% of the general population, for which several etiological factors were identified. Important among these is immunological dysfunction. This review aims to show how immunology can inform specific etiological factors, and how distinguishing between these etiologies is important from a personalized treatment perspective. We found discrepancies concerning cytokines, raising the hypothesis of specific immunological etiological factors. Antibody studies support the existence of a potential autoimmune etiological factor. Infections may also provoke OCD symptoms, and therefore, could be considered as specific etiological factors with specific immunological impairments. Finally, we underline the importance of distinguishing between different etiological factors since some specific treatments already exist in the context of immunological factors for the improvement of classic treatments.

Interactions Between Variation in Candidate Genes and Environmental Factors in the Etiology of Schizophrenia and Bipolar Disorder: a Systematic Review

Schizophrenia and bipolar disorder (BD) are complex and multidimensional disorders with high heritability rates. The contribution of genetic factors to the etiology of these disorders is increasingly being recognized as the action of multiple risk variants with small effect sizes, which might explain only a minor part of susceptibility. On the other site, numerous environmental factors have been found to play an important role in their causality. Therefore, in recent years, several studies focused on gene × environment interactions that are believed to bridge the gap between genetic underpinnings and environmental insults. In this article, we performed a systematic review of studies investigating gene × environment interactions in BD and schizophrenia spectrum phenotypes. In the majority of studies from this field, interacting effects of variation in genes encoding catechol-O-methyltransferase (COMT), brain-derived neurotrophic factor (BDNF), and FK506-binding protein 5 (FKBP5) have been explored. Almost consistently, these studies revealed that polymorphisms in COMT, BDNF, and FKBP5 genes might interact with early life stress and cannabis abuse or dependence, influencing various outcomes of schizophrenia spectrum disorders and BD. Other interactions still require further replication in larger clinical and non-clinical samples. In addition, future studies should address the direction of causality and potential mechanisms of the relationship between gene × environment interactions and various categories of outcomes in schizophrenia and BD.

DNA methyltransferase 3A gene polymorphism contributes to daily life stress susceptibility

Daily life stress markedly affects the response toward stressful stimuli. DNA methy-lation is one of the factors that regulate this response, and is a normal mechanism of somatic cell growth, but its regulatory gene variations may cause alterations in the stress response. The aim of the present study was to investigate genotypic variants of the DNA methyltransferase 3A (DNMT3A) gene in 129 healthy subjects and evaluate its association with daily life stress. Blood samples were collected, and genomic DNA was isolated. DNA was amplified using specific tetra primers for DNMT3A (C/T) rs11683424 and visualized following 2% agarose gel electrophoresis. The association of DNMT3A genetic variants with daily life stress was analyzed using the Kessler Psychological Distress Scale (K10). We observed that the distribution of subjects with genotype CC (wild type), CT (heteromutant), and TT (homomutant) was 13.95%, 81.4%, and 4.65%, respectively. Genetic variations significantly affected the daily life stress condition (p=0.04) in Indonesian healthy subjects, but most of the subjects with the CT phenotype were classified in a stress condition.

Do people with schizophrenia experience more negative emotion and less positive emotion in their daily lives? A meta-analysis of experience sampling studies

Research on emotion experience in response to valenced stimuli has consistently shown that people with schizophrenia have the capacity to experience emotion. Specifically, people with schizophrenia report similar experiences to both positive and negative emotion-eliciting stimuli as individuals without the disorder. However, it is less clear if people with schizophrenia experience similar levels of positive emotion and negative emotion outside of standardized laboratory contexts, as in their daily lives. One reliable method for assessing emotion experience in schizophrenia has been the Experience Sampling Method (ESM), or Ecological Momentary Assessment (EMA). Using the PRISMA guidelines for meta-analysis, we reviewed the literature for all studies that included people with and without schizophrenia, and that included a positive or negative emotion assessment during participants' daily lives. The current study is a meta-analysis of 12 EMA studies of emotion experience, which included a total of 619 people with schizophrenia and 730 healthy controls. Results indicate that people with schizophrenia consistently report more negative and less positive emotion than healthy control participants. These findings differ from laboratory-based studies, which may be due to several factors, including environmental differences, effects of the disorder that appear more clearly in daily life, or additional concerns, such as depression, which has been shown to be related to negative emotion in schizophrenia. Importantly, these findings are in line with questionnaire-based measures of emotion experience, lending some support for their use in research and clinical settings.

Preclinical and Clinical Evidence of DNA Methylation Changes in Response to Trauma and Chronic Stress

Exposure to chronic stress, either repeated severe acute or moderate sustained stress, is one of the strongest risk factors for the development of psychopathologies such as post-traumatic stress disorder and depression. Chronic stress is linked with several lasting biological consequences, particularly to the stress endocrine system but also affecting intermediate phenotypes such as brain structure and function, immune function, and behavior. Although genetic predisposition confers a proportion of the risk, the most relevant molecular mechanisms determining those susceptible and resilient to the effects of stress and trauma may be epigenetic. Epigenetics refers to the mechanisms that regulate genomic information by dynamically changing the patterns of transcription and translation of genes. Mounting evidence from preclinical rodent and clinical population studies strongly support that epigenetic modifications can occur in response to traumatic and chronic stress. Here, we discuss this literature examining stress-induced epigenetic changes in preclinical models and clinical cohorts of stress and trauma occurring early in life or in adulthood. We highlight that a complex relationship between the timing of environmental stressors and genetic predispositions likely mediate the response to chronic stress over time, and that a better understanding of epigenetic changes is needed by further investigations in longitudinal and postmortem brain clinical cohorts.

Epigenetic dysfunctional diseases and therapy for infection and inflammation

Even though the discovery of the term 'epigenetics' was in the 1940s, it has recently become one of the most promising and expanding fields to unravel the gene expression pattern in several diseases. The most well studied example is cancer, but other diseases like metabolic disorders, autism, or inflammation-associated diseases such as lung injury, autoimmune disease, asthma, and type-2 diabetes display aberrant gene expression and epigenetic regulation during their occurrence. The change in the epigenetic pattern of a gene may also alter gene function because of a change in the DNA status. Constant environmental pressure, lifestyle, as well as food habits are the other important parameters responsible for transgenerational inheritance of epigenetic traits. Discovery of epigenetic modifiers targeting DNA methylation and histone deacetylation enzymes could be an alternative source to treat or manipulate the pathogenesis of diseases. Particularly, the combination of epigenetic drugs such as 5-aza-2-deoxycytidine (Aza) and trichostatin A (TSA) are well studied to reduce inflammation in an acute lung injury model. It is important to understand the epigenetic machinery and the function of its components in specific diseases to develop targeted epigenetic therapy. Moreover, it is equally critical to know the specific inhibitors other than the widely used pan inhibitors in clinical trials and explore their roles in regulating specific genes in a more defined way during infection.

Sex Differences in Nucleus Accumbens Transcriptome Profiles Associated with Susceptibility versus Resilience to Subchronic Variable Stress

Depression and anxiety disorders are more prevalent in females, but the majority of research in animal models, the first step in finding new treatments, has focused predominantly on males. Here we report that exposure to subchronic variable stress (SCVS) induces depression-associated behaviors in female mice, whereas males are resilient as they do not develop these behavioral abnormalities. In concert with these different behavioral responses, transcriptional analysis of nucleus accumbens (NAc), a major brain reward region, by use of RNA sequencing (RNA-seq) revealed markedly different patterns of stress regulation of gene expression between the sexes. Among the genes displaying sex differences was DNA methyltransferase 3a (Dnmt3a), which shows a greater induction in females after SCVS. Interestingly, Dnmt3a expression levels were increased in the NAc of depressed humans, an effect seen in both males and females. Local overexpression of Dnmt3a in NAc rendered male mice more susceptible to SCVS, whereas Dnmt3a knock-out in this region rendered females more resilient, directly implicating this gene in stress responses. Associated with this enhanced resilience of female mice upon NAc knock-out of Dnmt3a was a partial shift of the NAc female transcriptome toward the male pattern after SCVS. These data indicate that males and females undergo different patterns of transcriptional regulation in response to stress and that a DNA methyltransferase in NAc contributes to sex differences in stress vulnerability.

SIGNIFICANCE STATEMENT

Women have a higher incidence of depression than men. However, preclinical models, the first step in developing new diagnostics and therapeutics, have been performed mainly on male subjects. Using a stress-based animal model of depression that causes behavioral effects in females but not males, we demonstrate a sex-specific transcriptional profile in brain reward circuitry. This transcriptional profile can be altered by removal of an epigenetic mechanism, which normally suppresses DNA transcription, creating a hybrid male/female transcriptional pattern. Removal of this epigenetic mechanism also induces behavioral resilience to stress in females. These findings shed new light onto molecular factors controlling sex differences in stress response.

Differential Vulnerability to Early-Life Parental Death: The Moderating Effects of Family Suicide History on Risks for Major Depression and Substance Abuse in Later Life

Only a portion of those individuals exposed to parental death in early life (PDE) develop behavioral health disorders. We utilized demographic pedigree data from the Utah Population Database to test for differential vulnerability to PDE by creating a risk score of familial susceptibility to suicide (FS) at the population level. Using logistic panel regression models, we tested for multiplicative interactions between PDE and FS on the risks of major depressive disorder (MDD) and substance abuse (SA), measured using Medicare claims, after age 65. The final sample included 155,983 individuals (born 1886-1944), yielding 1,431,060 person-years at risk (1992-2009). Net of several potential confounders, including probability of survival to age 65, we found an FS × PDE interaction for females, in which PDE and FS as main effects had no impact but jointly increased MDD risk. No statistically significant main or interactive effects were found for SA among females or for either phenotype among males. Our findings are consistent with a differential vulnerability model for MDD in females, in which early-life stress increases the risk for poor behavioral health only among the vulnerable. Furthermore, we demonstrate how demographic and pedigree data might serve as tools for investigating differential vulnerability hypotheses.

Epigenetics and Child Psychiatry: Ethical and Legal Issues

Epigenetics has the potential to revolutionize diagnosis and treatment in psychiatry, especially child psychiatry, as it may offer the opportunity for early detection and prevention, as well as development of new treatments. As with the previous introduction of genetic research in psychiatry, there is also the problem of unrealistic expectations and new legal and ethical problems. This article reviews the potential contributions and problems of epigenetic research in child psychiatry. Previous legal and ethical issues in genetic research serve as a guide to those in epigenetic research. Recommendations for safeguards and guidelines on the use of epigenetics with children and adolescents are outlined based on the identified issues.

DNMT3A moderates cognitive decline in subjects with mild cognitive impairment: replicated evidence from two mild cognitive impairment cohorts

Epigenetic dysregulation has been associated with cognitive decline and Alzheimer's disease. The present study investigated associations between common SNPs in genes regulating DNA methylation and age-related changes in cognitive decline in two independent prospective cohorts of patients suffering from mild cognitive impairment. An association between the rs1187120 SNP in DNMT3A and annual decline in cognitive functioning was discovered and replicated, suggesting that DNMT3A moderates cognitive decline in subjects with mild cognitive impairment.

Ambulatory assessment as a means of longitudinal phenotypes characterization in psychiatric disorders

Ambulatory Assessment (AA) comprises the use of in-field methods to assess individuals' behavior, physiology, and the experience as they unfold in naturalistic settings. We propose that AA is favorable for the investigation of gene-environment interactions and for the search for endophenotypes, being able to assess the experienced environment and to track basic regulatory processes, such as stress reactivity, affective instability, and reward experience, which are potential common factors that underlie psychiatric disorders. In this article, we (a) first describe briefly the rationale of AA and summarize the key advantages of the approach, (b) highlight within-subject regulatory processes, such as stress reactivity, affective instability, and reward experience, (c) describe studies that used AA to examine genetic influences in psychiatric disorders, and (d) briefly review longitudinal studies that have investigated phenotypes of psychiatric disorders. The reported studies yielded promising, although sometimes inconclusive evidence for genetic effects on endophenotypes of psychiatric disorders. Moreover, most studies were twin or family studies, especially in stress-sensitivity research; thus, it is unclear which specific single nucleotide polymorphisms contribute to the endophenotypes of psychiatric disorders. We do hope that within-subject regulatory processes will enable us to clarify the fundamental psychological dimensions that cut across traditional disorders and link them to their genetic underpinnings.