An epigenetic framework for neurodevelopmental disorders: from pathogenesis to potential therapy

Sex-biased gene expression during neural differentiation of human embryonic stem cells

Sex differences in the developing human brain are primarily attributed to hormonal influence. Recently however, genetic differences and their impact on the developing nervous system have attracted increased attention. To understand genetically driven sexual dimorphisms in neurodevelopment, we investigated genome-wide gene expression in an in vitro differentiation model of male and female human embryonic stem cell lines (hESC), independent of the effects of human sex hormones. Four male and four female-derived hESC lines were differentiated into a population of mixed neurons over 37 days. Differential gene expression and gene set enrichment analyses were conducted on bulk RNA sequencing data. While similar differentiation tendencies in all cell lines demonstrated the robustness and reproducibility of our differentiation protocol, we found sex-biased gene expression already in undifferentiated ESCs at day 0, but most profoundly after 37 days of differentiation. Male and female cell lines exhibited sex-biased expression of genes involved in neurodevelopment, suggesting that sex influences the differentiation trajectory. Interestingly, the highest contribution to sex differences was found to arise from the male transcriptome, involving both Y chromosome and autosomal genes. We propose 13 sex-biased candidate genes (10 upregulated in male cell lines and 3 in female lines) that are likely to affect neuronal development. Additionally, we confirmed gene dosage compensation of X/Y homologs escaping X chromosome inactivation through their Y homologs and identified a significant overexpression of the Y-linked demethylase UTY and KDM5D in male hESC during neuron development, confirming previous results in neural stem cells. Our results suggest that genetic sex differences affect neuronal differentiation trajectories, which could ultimately contribute to sex biases during human brain development.

Further Delineation of Clinical Phenotype of ZMYND11 Variants in Patients with Neurodevelopmental Dysmorphic Syndrome

Intellectual disability with speech delay and behavioural abnormalities, as well as hypotonia, seizures, feeding difficulties and craniofacial dysmorphism, are the main symptoms associated with pathogenic variants of the ZMYND11 gene. The range of clinical manifestations of the ZMYND phenotype is constantly being expanded by new cases described in the literature. Here, we present two previously unreported paediatric patients with neurodevelopmental challenges, who were diagnosed with missense variants in the ZMYND11 gene. It should be noted that one of the individuals manifested with hyperinsulinaemic hypoglycaemia (HH), a symptom that was not described before in published works. The reason for the occurrence of HH in our proband is not clear, so we try to explain the origin of this symptom in the context of the ZMYND11 syndrome. Thus, this paper contributes to knowledge on the range of possible manifestations of the ZMYND disease and provides further evidence supporting its association with neurodevelopmental challenges.

Behavioral and Molecular Characterization of Prenatal Stress Effects on the C57BL/6J Genetic Background for the Study of Autism Spectrum Disorder

Stress-inducing events during pregnancy are associated with aberrant neurodevelopment resulting in adverse psychiatric outcomes, including autism spectrum disorder (ASD). While numerous preclinical models for the study of ASD are frequently generated using C57BL/6J mice, few studies have investigated the effects of prenatal stress on this genetic background. In the current manuscript, we stressed C57BL/6 dams during gestation and examined numerous behavioral and molecular endophenotypes in the adult male and female offspring to characterize the resultant phenotype as compared with offspring born from nonstressed (NS) dams. Adult mice born from prenatal restraint stressed (PRS) dams demonstrated reduced sociability and reciprocal social interaction along with increased marble burying behaviors relative to mice born from nonstressed control dams. Differential expression of genes related to excitatory and inhibitory neurotransmission was evaluated in the medial prefrontal cortex, amygdala, hippocampus, nucleus accumbens and caudate putamen via qRT-PCR. The male PRS mouse behavioral phenotype coincided with aberrant expression of glutamate and GABA marker genes (e.g., Grin1, Grin2b, Gls, Gat1, Reln) in neural substrates of social behavior. Rescue of the male PRS sociability deficit by a known antipsychotic with epigenetic properties (i.e., clozapine (5 mg/kg) + 18 hr washout) indicated possible epigenetic regulation of genes that govern sociability. Clozapine treatment increased the expression levels of genes involved in DNA methylation, histone methylation, and histone acetylation in the nucleus accumbens. Identification of etiology-specific mechanisms underlying clinically relevant behavioral phenotypes may ultimately provide novel therapeutic interventions for the treatment of psychiatric disorders including ASD.

Risk of attention deficit hyperactivity disorder diagnosis following multiple exposures to general anesthesia in the paediatric population: A systematic review and meta-analysis

Objectives

The risk of attention deficit hyperactivity disorder (ADHD) following multiple exposures to anesthesia has been debated. Our objective was to systematically review the literature to examine the association between multiple exposures to general anesthesia before age 5 and subsequent diagnosis of ADHD.

Methods

A systematic search of EMBASE, PubMed, and SCOPUS was performed using key search terms in February 2022. We included studies that: were published after 1980, included only otherwise healthy children who experienced two or more exposures to general anesthetic before age 5, diagnosed ADHD by a medical professional before age 19 years after exposure to general anesthetic, were cross-sectional, case-control, or cohort study, and were published in English. The results (expressed as hazard ratios [HR] and associated 95% confidence intervals [CI]) were pooled using meta-analytic techniques. Studies which did not present their results as HR and 95% CI were analyzed separately. GRADE was used to determine the certainty of the findings. PRISMA guidelines were followed at each stage of the review.

Results

Eight studies (196,749 children) were included. Five reported HR and 95% CI and were subsequently pooled for meta-analysis. Multiple exposures to anesthesia were associated with diagnosis of ADHD before the 19th year of life (HR: 1.71; 95% CI: 1.59, 1.84). Two of the three studies not used in the meta-analysis also found an increased risk of ADHD diagnosis following multiple anesthetic exposures.

Conclusions

There was an association between multiple early exposures to general anesthesia and later diagnosis of ADHD.

Histone 3 Trimethylation Patterns are Associated with Resilience or Stress Susceptibility in a Rat Model of Major Depression Disorder

Major Depressive Disorder (MDD) is a severe and multifactorial psychiatric condition. Evidence has shown that environmental factors, such as stress, significantly explain MDD pathophysiology. Studies have hypothesized that changes in histone methylation patterns are involved in impaired glutamatergic signaling. Based on this scenario, this study aims to investigate histone 3 involvement in depression susceptibility or resilience in MDD pathophysiology by investigating cellular and molecular parameters related to i) glutamatergic neurotransmission, ii) astrocytic functioning, and iii) neurogenesis. For this, we subjected male Wistar rats to the Chronic Unpredictable Mild Stress (CUMS) model of depression. We propose that by evaluating the sucrose consumption, open field, and object recognition test performance from animals submitted to CUMS, it is possible to predict with high specificity rats with susceptibility to depressive-like phenotype and resilient to the depressive-like phenotype. We also demonstrated, for the first time, that patterns of H3K4me3, H3K9me3, H3K27me3, and H3K36me3 trimethylation are strictly associated with the resilient or susceptible to depressive-like phenotype in a brain-region-specific manner. Additionally, susceptible animals have reduced DCx and GFAP and resilient animals present increase of AQP-4 immunoreactivity. Together, these results provide evidence that H3 trimethylations are related to the development of the resilient or susceptible to depressive-like phenotype, contributing to further advances in the pathophysiology of MDD and the discovery of mechanisms behind resilience.

An enriched maternal environment and stereotypies of sows differentially affect the neuro-epigenome of brain regions related to emotionality in their piglets

Epigenetic mechanisms are important modulators of neurodevelopmental outcomes in the offspring of animals challenged during pregnancy. Pregnant sows living in a confined environment are challenged with stress and lack of stimulation which may result in the expression of stereotypies (repetitive behaviours without an apparent function). Little attention has been devoted to the postnatal effects of maternal stereotypies in the offspring. We investigated how the environment and stereotypies of pregnant sows affected the neuro-epigenome of their piglets. We focused on the amygdala, frontal cortex, and hippocampus, brain regions related to emotionality, learning, memory, and stress response. Differentially methylated regions (DMRs) were investigated in these brain regions of male piglets born from sows kept in an enriched vs a barren environment. Within the latter group of piglets, we compared the brain methylomes of piglets born from sows expressing stereotypies vs sows not expressing stereotypies. DMRs emerged in each comparison. While the epigenome of the hippocampus and frontal cortex of piglets is mainly affected by the maternal environment, the epigenome of the amygdala is mainly affected by maternal stereotypies. The molecular pathways and mechanisms triggered in the brains of piglets by maternal environment or stereotypies are different, which is reflected on the differential gene function associated to the DMRs found in each piglets' brain region . The present study is the first to investigate the neuro-epigenomic effects of maternal enrichment in pigs' offspring and the first to investigate the neuro-epigenomic effects of maternal stereotypies in the offspring of a mammal.

Epigenetic regulation of metabotropic glutamate 2/3 receptors: Potential role for ultra-resistant schizophrenia?

Schizophrenia is a severe and debilitating psychiatric disorder characterized by early cognitive deficits, emotional and behavioral abnormalities resulted by a dysfunctional gene x environment interaction. Genetic and epigenetic abnormalities in cortical parvalbumin-positive GABAergic interneurons lead to alterations in glutamate-mediated excitatory neurotransmission, synaptic plasticity, and neuronal development. Epigenetic alterations during pregnancy or early phases of postnatal life are associated with schizophrenia vulnerability as well as inflammatory processes which are at the basis of brain pathology. An epigenetic animal model of schizophrenia showed specific changes in promoter DNA methylation activity of genes related to schizophrenia such as reelin, BDNF and GAD67, and altered expression and function of mGlu2/3 receptors in the frontal cortex. Although antipsychotic medications represent the main treatment for schizophrenia and generally show an optimal efficacy profile for positive symptoms and relatively poor efficacy for negative or cognitive symptoms, a considerable percentage of individuals show poor response, do not achieve a complete remission, and approximately 30 % of patients show treatment-resistance. Here, we explore the potential role of epigenetic abnormalities linked to metabotropic glutamate 2/3 receptors changes in expression and function as key molecular factors underlying the difference in response to antipsychotics.

Dysregulation of immune and metabolism pathways in maternal immune activation induces an increased risk of autism spectrum disorders

AIMS

Maternal immune activation (MIA) via infection during pregnancy is known to be an environmental risk factor for neurodevelopmental disorders and the development of autism spectrum disorders (ASD) in the offspring, but it still remains elusive that the molecular relevance between infection-induced abnormal neurodevelopmental events and an increased risk for ASD development.

MAIN METHODS

Fully considering the extremely high genetic heterogeneity of ASD and the universality of risk-gene with minimal effect-sizes, the gene and pathway-based association analysis was performed with the transcriptomic and DNA methylation landscapes of temporal human embryonic brain development and ASD, and the time-course transcriptional profiling of MIA. We conducted the transcriptional profiling of mouse abnormal neurodevelopment two days following induced MIA via LPS injection at E10.5.

KEY FINDINGS

A novel evidence was proved that illustrated altering four immune and metabolism-related risk pathways, including starch and sucrose metabolism, ribosome, protein processing in endoplasmic reticulum, and retrograde endocannabinoid signaling pathway, which were prominent involvement in the process of MIA regulating abnormal fetal brain development to induce an increased risk of ASD. Here, we have observed that almost all key genes within these risk pathways are significantly differentially expressed at embryonic days (E) 10.5-12.5, which is considered to be the optimal coincidence window of mouse embryonic brain development to study the intimate association between MIA and ASD using mouse animal models.

SIGNIFICANCE

There search establishes that MIA causes dysregulation of immune and metabolic pathways, which leads to abnormal embryonic neurodevelopment, thus promoting development of ASD symptoms in offspring.

Brain-derived neurotrophic factor (BDNF) epigenomic modifications and brain-related phenotypes in humans: A systematic review

Epigenomic modifications of the brain-derived neurotrophic factor (BDNF) gene have been postulated to underlie the pathogenesis of neurodevelopmental, psychiatric, and neurological conditions. This systematic review summarizes current evidence investigating the association of BDNF epigenomic modifications (DNA methylation, non-coding RNA, histone modifications) with brain-related phenotypes in humans. A novel contribution is our creation of an open access web-based application, the BDNF DNA Methylation Map, to interactively visualize specific positions of CpG sites investigated across all studies for which relevant data were available. Our literature search of four databases through September 27, 2021 returned 1701 articles, of which 153 met inclusion criteria. Our review revealed exceptional heterogeneity in methodological approaches, hindering the identification of clear patterns of robust and/or replicated results. We summarize key findings and provide recommendations for future epigenomic research. The existing literature appears to remain in its infancy and requires additional rigorous research to fulfill its potential to explain BDNF-linked risk for brain-related conditions and improve our understanding of the molecular mechanisms underlying their pathogenesis.

Constrained neuro fuzzy inference methodology for explainable personalised modelling with applications on gene expression data

Interpretable machine learning models for gene expression datasets are important for understanding the decision-making process of a classifier and gaining insights on the underlying molecular processes of genetic conditions. Interpretable models can potentially support early diagnosis before full disease manifestation. This is particularly important yet, challenging for mental health. We hypothesise this is due to extreme heterogeneity issues which may be overcome and explained by personalised modelling techniques. Thus far, most machine learning methods applied to gene expression datasets, including deep neural networks, lack personalised interpretability. This paper proposes a new methodology named personalised constrained neuro fuzzy inference (PCNFI) for learning personalised rules from high dimensional datasets which are structurally and semantically interpretable. Case studies on two mental health related datasets (schizophrenia and bipolar disorders) have shown that the relatively short and simple personalised fuzzy rules provided enhanced interpretability as well as better classification performance compared to other commonly used machine learning methods. Performance test on a cancer dataset also showed that PCNFI matches previous benchmarks. Insights from our approach also indicated the importance of two genes (ATRX and TSPAN2) as possible biomarkers for early differentiation of ultra-high risk, bipolar and healthy individuals. These genes are linked to cognitive ability and impulsive behaviour. Our findings suggest a significant starting point for further research into the biological role of cognitive and impulsivity-related differences. With potential applications across bio-medical research, the proposed PCNFI method is promising for diagnosis, prognosis, and the design of personalised treatment plans for better outcomes in the future.

The Strategy of Targeting Peroxisome Proliferator-Activated Receptor (PPAR) in the Treatment of Neuropsychiatric Disorders

Peroxisome proliferator-activated receptors (PPARs) are nonsteroid nuclear receptors and transcription factors that regulate several neuroinflammatory and metabolic processes, recently involved in several neuropsychiatric conditions, including Alzheimer's disease, Parkinson's disease, major depressive disorder, post-traumatic stress disorder (PTSD), schizophrenia spectrum disorders, and autism spectrum disorders. PPARs are ligand-activated receptors that, following stimulation, induce neuroprotective effects by decreasing neuroinflammatory processes through inhibition of the nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) expression and consequent suppression of pro-inflammatory cytokine production. PPARs heterodimerize with the retinoid X-receptor (RXR) and bind to PPAR-responsive regulatory elements (PPRE) in the promoter region of target genes involved in lipid metabolism, synthesis of cholesterol, catabolism of amino acids, and inflammation. Interestingly, PPARs are considered functionally part of the extended endocannabinoid (eCB) system that includes the classic eCB, anandamide, which act at cannabinoid receptor types 1 (CB1) and 2 (CB2) and are implicated in the pathophysiology of stress-related neuropsychiatric disorders. In preclinical studies, PPAR stimulation improves anxiety and depression-like behaviors by enhancing neurosteroid biosynthesis. The peculiar functional role of PPARs by exerting anti-inflammatory and neuroprotective effects and their expression localization in neurons and glial cells of corticolimbic circuits make them particularly interesting as novel therapeutic targets for several neuropsychiatric disorders characterized by underlying neuroinflammatory/neurodegenerative mechanisms. Herein, we discuss the pathological hallmarks of neuropsychiatric conditions associated with neuroinflammation, as well as the pivotal role of PPARs with a special emphasis on the subtype alpha (PPAR-α) as a suitable molecular target for therapeutic interventions.

Functional Nutrition as Integrated Intervention for In- and Outpatient with Schizophrenia

Schizophrenia is a chronic and progressive disorder characterized by cognitive, emotional, and behavioral abnormalities associated with neuronal development and synaptic plasticity alterations. Genetic and epigenetic abnormalities in cortical parvalbumin-positive GABAergic interneurons and consequent alterations in glutamate-mediated excitatory neurotransmission during early neurodevelopment underlie schizophrenia manifestation and progression. Also, epigenetic alterations during pregnancy or early phases of postnatal life are associated with schizophrenia vulnerability and inflammatory processes, which are at the basis of brain pathology and a higher risk of comorbidities, including cardiovascular diseases and metabolic syndrome. In addition, schizophrenia patients adopt an unhealthy lifestyle and poor nutrition, leading to premature death. Here, I explored the role of functional nutrition as an integrated intervention for the long-term management of patients with schizophrenia. Several natural bioactive compounds in plant-based whole foods, including flavonoids, phytonutrients, vitamins, fatty acids, and minerals, modulate brain functioning by targeting neuroinflammation and improving cognitive decline. Although further clinical studies are needed, a functional diet rich in natural bioactive compounds might be effective in synergism with standard treatments to improve schizophrenia symptoms and reduce the risk of comorbidities.

Mapping miRNA Research in Schizophrenia: A Scientometric Review

Micro RNA (miRNA) research has great implications in uncovering the aetiology of neuropsychiatric conditions due to the role of miRNA in brain development and function. Schizophrenia, a complex yet devastating neuropsychiatric disorder, is one such condition that had been extensively studied in the realm of miRNA. Although a relatively new field of research, this area of study has progressed sufficiently to warrant dozens of reviews summarising findings from past to present. However, as a majority of reviews cannot encapsulate the full body of research, there is still a need to synthesise the diversity of publications made in this area in a systematic but easy-to-understand manner. Therefore, this study adopted bibliometrics and scientometrics, specifically document co-citation analysis (DCA), to review the literature on miRNAs in the context of schizophrenia over the course of history. From a literature search on Scopus, 992 papers were found and analysed with CiteSpace. DCA analysis generated a network of 13 major clusters with different thematic focuses within the subject area. Finally, these clusters are qualitatively discussed. miRNA research has branched into schizophrenia, among other medical and psychiatric conditions, due to previous findings in other forms of non-coding RNA. With the rise of big data, bioinformatics analyses are increasingly common in this field of research. The future of research is projected to rely more heavily on interdisciplinary collaboration. Additionally, it can be expected that there will be more translational studies focusing on the application of these findings to the development of effective treatments.

Disruption of the gene regulatory programme in neurodevelopmental disorders

Cortical development consists of a series of synchronised events, including fate transition of cortical progenitors, neuronal migration, specification and connectivity. It is becoming clear that gene expression programs governing these events rely on the interplay between signalling molecules, transcription factors and epigenetic mechanisms. When genetic or environmental factors disrupt expression of genes involved in important brain development processes, neurodevelopmental disorders can occur. This review aims to highlight how recent advances in technologies have helped uncover and imitate the gene regulatory mechanisms commonly disrupted in neurodevelopmental disorders.

Neuroepigenetic Changes in DNA Methylation Affecting Diabetes-Induced Cognitive Impairment

Chronic diabetic conditions have been associated with certain cerebral complications, that include neurobehavioral dysfunctional patterns and morphological alterations of neurons, especially the hippocampus. Neuroanatomical studies done by the authors have shown decreased total dendritic length, intersections, dendritic length per branch order and nodes in the CA1 hippocampal region of the diabetic brain as compared to its normal control group, indicating reduced dendritic arborization of the hippocampal CA1 neurons. Epigenetic alterations in the brain are well known to affect age-associated disorders, however its association with the evolving diabetes-induced damage in the brain is still not fully understood. DNA hypermethylation within the neurons, tend to silent the gene expression of several regulatory proteins. The findings in the study have shown an increase in global DNA methylation in palmitic acid-induced lipotoxic Neuro-2a cells as well as within the diabetic mice brain. Inhibiting DNA methylation, restored the levels of HSF1 and certain HSPs, suggesting plausible effect of DNMTs in maintaining the proteostasis and synaptic fidelity. Neuroinflammation, as exhibited by the astrocyte activation (GFAP), were further significantly decreased in the 5-azadeoxycytidine group (DNMT inhibitor). This was further evidenced by decrease in proinflammatory cytokines TNF⍺, IL-6, and mediators iNOS and Phospho-NFkB. Our results suggest that changes in DNA methylation advocate epigenetic dysregulation and its involvement in disrupting the synaptic exactitude in the hippocampus of diabetic mice model, providing an insight into the pathophysiology of diabetes-induced neuroepigenetic changes.

Changes in Stereotypies: Effects over Time and over Generations

Simple Summary

Herein, we propose that there should be discussion about the function and effects of stereotypies in relation to the time during which they are shown. In the first stages, stereotypies may help animals deal with challenges. However, behavior can potentially alter the brain, impairing its function due the absence of a diverse repertory, and change brain connections, neurophysiology and later neuroanatomy. The neuroanatomical changes in individuals showing stereotypies could be an effect rather than a cause of the stereotypy. As a consequence, studies showing different outcomes for animal welfare from stereotypy expression could be due to variation in a timeline of expression. Stereotypies are widely used as an animal welfare indicator, and their expression can tell us about psychological states. However, there are questions about the longer-term consequences if animals express stereotypies: do the stereotypies help in coping? During the prenatal period, stereotypic behavior expressed by the mother can change the phenotype of the offspring, especially regarding emotionality, one mechanism acting via methylation in the limbic system in the brain. Are individuals that show stereotypies for shorter or longer periods all better adjusted, and hence have better welfare, or is the later welfare of some worse than that of individuals that do not show the behavior?

Abstract

Stereotypies comprise a wide range of repeated and apparently functionless behaviors that develop in individuals whose neural condition or environment results in poor welfare. While stereotypies are an indicator of poor welfare at the time of occurrence, they may have various consequences. Environmental enrichment modifies causal factors and reduces the occurrence of stereotypies, providing evidence that stereotypies are an indicator of poor welfare. However, stereotypy occurrence and consequences change over time. Furthermore, there are complex direct and epigenetic effects when mother mammals that are kept in negative conditions do or do not show stereotypies. It is proposed that, when trying to deal with challenging situations, stereotypies might initially help animals to cope. After further time in the conditions, the performance of the stereotypy may impair brain function and change brain connections, neurophysiology and eventually neuroanatomy. It is possible that reported neuroanatomical changes are an effect of the stereotypy rather than a cause.

Cell-type-specific epigenetic effects of early life stress on the brain

Early life stress (ELS) induces long-term phenotypic adaptations that contribute to increased vulnerability to a host of neuropsychiatric disorders. Epigenetic mechanisms, including DNA methylation, histone modifications and non-coding RNA, are a proposed link between environmental stressors, alterations in gene expression, and phenotypes. Epigenetic modifications play a primary role in shaping functional differences between cell types and can be modified by environmental perturbations, especially in early development. Together with contributions from genetic variation, epigenetic mechanisms orchestrate patterns of gene expression within specific cell types that contribute to phenotypic variation between individuals. To date, many studies have provided insights into epigenetic changes resulting from ELS. However, most of these studies have examined heterogenous brain tissue, despite evidence of cell-type-specific epigenetic modifications in phenotypes associated with ELS. In this review, we focus on rodent and human studies that have examined epigenetic modifications induced by ELS in select cell types isolated from the brain or associated with genes that have cell-type-restricted expression in neurons, microglia, astrocytes, and oligodendrocytes. Although significant challenges remain, future studies using these approaches can enable important mechanistic insight into the role of epigenetic variation in the effects of ELS on brain function.

NSD1 mutations deregulate transcription and DNA methylation of bivalent developmental genes in Sotos syndrome

Sotos syndrome (SS), the most common overgrowth with intellectual disability (OGID) disorder, is caused by inactivating germline mutations of NSD1, which encodes a histone H3 lysine 36 methyltransferase. To understand how NSD1 inactivation deregulates transcription and DNA methylation (DNAm), and to explore how these abnormalities affect human development, we profiled transcription and DNAm in SS patients and healthy control individuals. We identified a transcriptional signature that distinguishes individuals with SS from controls and was also deregulated in NSD1-mutated cancers. Most abnormally expressed genes displayed reduced expression in SS; these downregulated genes consisted mostly of bivalent genes and were enriched for regulators of development and neural synapse function. DNA hypomethylation was strongly enriched within promoters of transcriptionally deregulated genes: overexpressed genes displayed hypomethylation at their transcription start sites while underexpressed genes featured hypomethylation at polycomb binding sites within their promoter CpG island shores. SS patients featured accelerated molecular aging at the levels of both transcription and DNAm. Overall, these findings indicate that NSD1-deposited H3K36 methylation regulates transcription by directing promoter DNA methylation, partially by repressing polycomb repressive complex 2 (PRC2) activity. These findings could explain the phenotypic similarity of SS to OGID disorders that are caused by mutations in PRC2 complex-encoding genes.

The Yin and Yang of epigenetics in the field of nanoparticles

Nanoparticles (NPs) have become a very exciting research avenue, with multitudinous applications in various fields, including the biomedical one, whereby they have been gaining considerable interest as drug carriers able to increase bioavailability, therapeutic efficiency and specificity of drugs. Epigenetics, a complex network of molecular mechanisms involved in gene expression regulation, play a key role in mediating the effect of environmental factors on organisms and in the etiology of several diseases (e.g., cancers, neurological disorders and cardiovascular diseases). For many of these diseases, epigenetic therapies have been proposed, whose application is however limited by the toxicity of epigenetic drugs. In this review, we will analyze two aspects of epigenetics in the field of NPs: the first is the role that epigenetics play in mediating nanotoxicity, and the second is the possibility of using NPs for delivery of "epi-drugs" to overcome their limitations. We aim to stimulate discussion among specialists, specifically on the potential contribution of epigenetics to the field of NPs, and to inspire newcomers to this exciting technology.

Autism Symptoms in Children and Young Adults With Fragile X Syndrome, Angelman Syndrome, Tuberous Sclerosis Complex, and Neurofibromatosis Type 1: A Cross-Syndrome Comparison

OBJECTIVE

The etiology of autism spectrum disorder (ASD) remains unclear, due to genetic heterogeneity and heterogeneity in symptoms across individuals. This study compares ASD symptomatology between monogenetic syndromes with a high ASD prevalence, in order to reveal syndrome specific vulnerabilities and to clarify how genetic variations affect ASD symptom presentation.

METHODS

We assessed ASD symptom severity in children and young adults (aged 0-28 years) with Fragile X Syndrome (FXS, n = 60), Angelman Syndrome (AS, n = 91), Neurofibromatosis Type 1 (NF1, n = 279) and Tuberous Sclerosis Complex (TSC, n = 110), using the Autism Diagnostic Observation Schedule and Social Responsiveness Scale. Assessments were part of routine clinical care at the ENCORE expertise center in Rotterdam, the Netherlands. First, we compared the syndrome groups on the ASD classification prevalence and ASD severity scores. Then, we compared individuals in our syndrome groups with an ASD classification to a non-syndromic ASD group (nsASD, n = 335), on both ASD severity scores and ASD symptom profiles. Severity scores were compared using MANCOVAs with IQ and gender as covariates.

RESULTS

Overall, ASD severity scores were highest for the FXS group and lowest for the NF1 group. Compared to nsASD, individuals with an ASD classification in our syndrome groups showed less problems on the instruments' social domains. We found a relative strength in the AS group on the social cognition, communication and motivation domains and a relative challenge in creativity; a relative strength of the NF1 group on the restricted interests and repetitive behavior scale; and a relative challenge in the FXS and TSC groups on the restricted interests and repetitive behavior domain.

CONCLUSION

The syndrome-specific strengths and challenges we found provide a frame of reference to evaluate an individual's symptoms relative to the larger syndromic population and to guide treatment decisions. Our findings support the need for personalized care and a dimensional, symptom-based diagnostic approach, in contrast to a dichotomous ASD diagnosis used as a prerequisite for access to healthcare services. Similarities in ASD symptom profiles between AS and FXS, and between NF1 and TSC may reflect similarities in their neurobiology. Deep phenotyping studies are required to link neurobiological markers to ASD symptomatology.

Inhibition of BET Proteins during Adolescence Affects Prefrontal Cortical Development: Relevance to Schizophrenia

Background: The present study investigated the role of proteins from the bromodomain and extra-terminal (BET) family in schizophrenia-like abnormalities in a neurodevelopmental model of schizophrenia induced by prenatal methylazoxymethanol (MAM) administration (MAM-E17). Methods: An inhibitor of BET proteins, JQ1, was administered during adolescence on postnatal days (P) 23–P29, and behavioural responses (sensorimotor gating, recognition memory) and prefrontal cortical (mPFC) function (long-term potentiation (LTP), molecular and proteomic analyses) studies were performed in adult males and females. Results: Deficits in sensorimotor gating and recognition memory were observed only in MAM-treated males. However, adolescent JQ1 treatment affected animals of both sexes in the control but not MAM-treated groups and reduced behavioural responses in both sexes. An electrophysiological study showed LTP impairments only in male MAM-treated animals, and JQ1 did not affect LTP in the mPFC. In contrast, MAM did not affect activity-dependent gene expression, but JQ1 altered gene expression in both sexes. A proteomic study revealed alterations in MAM-treated groups mainly in males, while JQ1 affected both sexes. Conclusions: MAM-induced schizophrenia-like abnormalities were observed only in males, while adolescent JQ1 treatment affected memory recognition and altered the molecular and proteomic landscape in the mPFC of both sexes. Thus, transient adolescent inhibition of the BET family might prompt permanent alterations in the mPFC.

Patients with PWS and related syndromes display differentially methylated regions involved in neurodevelopmental and nutritional trajectory

Background

Prader–Willi syndrome is a rare genetic neurodevelopmental disorder caused by a paternal deficiency of maternally imprinted gene expression located in the chromosome 15q11–q13 region. Previous studies have demonstrated that several classes of neurodevelopmental disorders can be attributed to either over- or under-expression of specific genes that may lead to impairments in neuronal generation, differentiation, maturation and growth. Epigenetic changes that modify gene expression have been highlighted in these disorders. One recent study focused on epigenetic analysis and compared patients with PWS with patients with other imprinting disorders. No study, however, has yet focused on epigenetics in patients with PWS specifically by comparing the mutations associated with this syndrome.

Objective

This study investigated the epigenetic modifications in patients with PWS and patients with PWS-related disorders caused by inactivation of two genes of the PWS chromosomal region, SNORD116 and MAGEL2. Our approach also aimed to compare the epigenetic modifications in PWS and PWS-related disorders.

Methods

We compared genome-wide methylation analysis (GWAS) in seven blood samples from patients with PWS phenotype (five with deletions of the PWS locus, one with a microdeletion of SNORD116 and one with a frameshift mutation of MAGEL2 presenting with Schaaf–Yang syndrome), as well as two control patients. Controls were infants that had been studied for suspicion of genetic diseases that was not confirmed by the genetic analysis and the clinical follow-up.

Results

The analysis identified 29,234 differentially methylated cytosines, corresponding to 5,308 differentially methylated regions (DMRs), which matched with 2,280 genes. The DMRs in patients with PWS were associated with neurodevelopmental pathways, endocrine dysfunction and social and addictive processes consistent with the key features of the PWS phenotype. In addition, the separate analysis for the SNORD116 and MAGEL2 deletions revealed that the DMRs associated with the SNORD116 microdeletion were found in genes implicated in metabolic pathways and nervous system development, whereas MAGEL2 mutations mostly concerned genes involved in macromolecule biosynthesis.

Conclusion

The PWS is associated with epigenetic modifications with differences in SNORD116 and MAGEL2 mutations, which seem to be relevant to the different associated phenotypes.

DNA methylation at birth potentially mediates the association between prenatal lead (Pb) exposure and infant neurodevelopmental outcomes

Early-life lead (Pb) exposure has been linked to adverse neurodevelopmental outcomes. Recent evidence has indicated a critical role of DNA methylation (DNAm) in cognition, and Pb exposure has also been shown to alter DNAm. However, it is unknown whether DNAm is part of the mechanism of Pb neurotoxicity. This longitudinal study investigated the associations between trimester-specific (T1, T2, and T3) maternal blood Pb concentrations, gene-specific DNAm in umbilical cord blood, and infant neurodevelopmental outcomes at 12 and 24 months of age (mental development index, psychomotor development index, and behavioral rating scale of orientation/engagement and emotional regulation) among 85 mother-infant pairs from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) study. In the mediation analysis for this pilot study, P < 0.1 was considered significant. DNAm at a locus in CCSER1 (probe ID cg02901723) mediated the association between T2 Pb on 24-month orientation/engagement [indirect effect estimate 4.44, 95% confidence interval (-0.09, 10.68), P = 0.06] and emotional regulation [3.62 (-0.05, 8.69), P = 0.05]. Cg18515027 (GCNT1) DNAm mediated the association of T1 Pb [-4.94 (-10.6, -0.77), P = 0.01] and T2 Pb [-3.52 (-8.09, -0.36), P = 0.02] with 24-month EMOCI, but there was a positive indirect effect estimate between T2 Pb and 24-month psychomotor development index [1.25 (-0.11, 3.32), P = 0.09]. The indirect effect was significant for cg19703494 (TRAPPC6A) DNAm in the association between T2 Pb and 24-month mental development index [1.54 (0, 3.87), P = 0.05]. There was also an indirect effect of cg23280166 (VPS11) DNAm on T3 Pb and 24-month EMOCI [2.43 (-0.16, 6.38), P = 0.08]. These associations provide preliminary evidence for gene-specific DNAm as mediators between prenatal Pb and adverse cognitive outcomes in offspring.

Negotiating Novelty: Constructing the Novel within Scientific Accounts of Epigenetics

Epigenetics is regarded by many as a compelling domain of biomedicine. The purported novelty of epigenetics has begun to have various societal ramifications, particularly in relation to processes of responsibilisation. Within sociology, it has stimulated hopeful debate about conceptual rapprochements between the biomedical and social sciences. This article is concerned with how novelty is socially produced and negotiated. The article engages directly with scientists' talk and writings about epigenetics (as process and field of study). I aim to advance an explicitly sociological analysis about the novelty of epigenetics that underscores its social production rather than an account which participates in its reification. I attend to definitional skirmishes, comparisons with genetics, excitement and intrigue, and considerations of the ethical dimensions of epigenetics. Any assertions that epigenetics is exciting or important should not inadvertently elide reflexive consideration of how such characterisations might be part of the machinery by which they become real.

Understanding the Link Between Allergy and Neurodevelopmental Disorders: A Current Review of Factors and Mechanisms

Both allergic diseases and neurodevelopmental disorders are non-communicable diseases (NCDs) that not only impact on the quality of life and but also result in substantial economic burden. Immune dysregulation and inflammation are typical hallmarks in both allergic and neurodevelopmental disorders, suggesting converging pathophysiology. Epidemiological studies provided convincing evidence for the link between allergy and neurodevelopmental diseases such as attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Possible factors influencing the development of these disorders include maternal depression and anxiety, gestational diabetes mellitus, maternal allergic status, diet, exposure to environmental pollutants, microbiome dysbiosis, and sleep disturbances that occur early in life. Moreover, apart from inflammation, epigenetics, gene expression, and mitochondrial dysfunction have emerged as possible underlying mechanisms in the pathogenesis of these conditions. The exploration and understanding of these shared factors and possible mechanisms may enable us to elucidate the link in the comorbidity.

Targeted Delivery for Neurodegenerative Disorders Using Gene Therapy Vectors: Gene Next Therapeutic Goals

The technique of gene therapy, ever since its advent nearly fifty years ago, has been utilized by scientists as a potential treatment option for various disorders. This review discusses some of the major neurodegenerative diseases (NDDs) like Alzheimer's disease (AD), Parkinson's Disease (PD), Motor neuron diseases (MND), Spinal Muscular Atrophy (SMA), Huntington's Disease (HD), Multiple Sclerosis (MS), etc. and their underlying genetic mechanisms along with the role that gene therapy can play in combating them. The pathogenesis and the molecular mechanisms specifying the altered gene expression of each of these NDDs have also been discussed in elaboration. The use of gene therapy vectors can prove to be an effective tool in the field of curative modern medicine for the generations to come. Therefore, consistent efforts and progressive research towards its implementation can provide us with powerful treatment options for disease conditions that have so far been considered as incurable.

Impaired Regulation of Histone Methylation and Acetylation Underlies Specific Neurodevelopmental Disorders

Epigenetic processes are critical for governing the complex spatiotemporal patterns of gene expression in neurodevelopment. One such mechanism is the dynamic network of post-translational histone modifications that facilitate recruitment of transcription factors or even directly alter chromatin structure to modulate gene expression. This is a tightly regulated system, and mutations affecting the function of a single histone-modifying enzyme can shift the normal epigenetic balance and cause detrimental developmental consequences. In this review, we will examine select neurodevelopmental conditions that arise from mutations in genes encoding enzymes that regulate histone methylation and acetylation. The methylation-related conditions discussed include Wiedemann-Steiner, Kabuki, and Sotos syndromes, and the acetylation-related conditions include Rubinstein-Taybi, KAT6A, genitopatellar/Say-Barber-Biesecker-Young-Simpson, and brachydactyly mental retardation syndromes. In particular, we will discuss the clinical/phenotypic and genetic basis of these conditions and the model systems that have been developed to better elucidate cellular and systemic pathological mechanisms.

DNA methylation epi-signature is associated with two molecularly and phenotypically distinct clinical subtypes of Phelan-McDermid syndrome

Background

Phelan-McDermid syndrome is characterized by a range of neurodevelopmental phenotypes with incomplete penetrance and variable expressivity. It is caused by a variable size and breakpoint microdeletions in the distal long arm of chromosome 22, referred to as 22q13.3 deletion syndrome, including the SHANK3 gene. Genetic defects in a growing number of neurodevelopmental genes have been shown to cause genome-wide disruptions in epigenomic profiles referred to as epi-signatures in affected individuals.

Results

In this study we assessed genome-wide DNA methylation profiles in a cohort of 22 individuals with Phelan-McDermid syndrome, including 11 individuals with large (2 to 5.8 Mb) 22q13.3 deletions, 10 with small deletions (< 1 Mb) or intragenic variants in SHANK3 and one mosaic case. We describe a novel genome-wide DNA methylation epi-signature in a subset of individuals with Phelan-McDermid syndrome.

Conclusion

We identified the critical region including the BRD1 gene as responsible for the Phelan-McDermid syndrome epi-signature. Metabolomic profiles of individuals with the DNA methylation epi-signature showed significantly different metabolomic profiles indicating evidence of two molecularly and phenotypically distinct clinical subtypes of Phelan-McDermid syndrome.

Association analysis of potentially functional variants within 8p12 with schizophrenia in the Han Chinese population

OBJECTIVES

Chromosome 8p12 was first identified as a schizophrenia (SCZ) risk locus in Chinese populations and replicated in European populations. However, the underlying functional variants still need to be further explored. In this study, we sought to identify plausible causal variants within this locus.

METHODS

A total of 386 potentially functional variants from 29 genes within the 8p12 locus were analysed in 2403 SCZ cases and 2594 control subjects in the Han Chinese population using Affymetrix customised genotyping assays. SHEsisplus was used for association analysis. A multiple testing corrected p value (false discovery rate (FDR)) < .05 was considered significant, and an unadjusted p value < .05 was considered nominal evidence of an association.

RESULTS

We did not find significant associations between the tested variants and SCZ. However, nominal associations were found for rs201292574 (unadjusted p = .033, FDR p = .571; 95% confidence interval (CI): 0.265-0.945; TACC1, NP_006274.2:p.Ala211Thr) and rs45563241 (unadjusted p = .039, FDR p = .571; 95% CI: 1.023-1.866; a synonymous mutation in ADRB3).

CONCLUSIONS

Our results provide limited evidence for the associations between variants from protein coding regions in 8p12 and SCZ in the Chinese population. Analyses of both coding and regulatory variants in larger sample sizes are required to further clarify the causal variants for SCZ with this risk locus.

Individual Differences in Intrinsic Brain Networks Predict Symptom Severity in Autism Spectrum Disorders

The neurobiology of heterogeneous neurodevelopmental disorders such as Autism Spectrum Disorders (ASD) is still unknown. We hypothesized that differences in subject-level properties of intrinsic brain networks were important features that could predict individual variation in ASD symptom severity. We matched cases and controls from a large multicohort ASD dataset (ABIDE-II) on age, sex, IQ, and image acquisition site. Subjects were matched at the individual level (rather than at group level) to improve homogeneity within matched case-control pairs (ASD: n = 100, mean age = 11.43 years, IQ = 110.58; controls: n = 100, mean age = 11.43 years, IQ = 110.70). Using task-free functional magnetic resonance imaging, we extracted intrinsic functional brain networks using projective non-negative matrix factorization. Intrapair differences in strength in subnetworks related to the salience network (SN) and the occipital-temporal face perception network were robustly associated with individual differences in social impairment severity (T = 2.206, P = 0.0301). Findings were further replicated and validated in an independent validation cohort of monozygotic twins (n = 12; 3 pairs concordant and 3 pairs discordant for ASD). Individual differences in the SN and face-perception network are centrally implicated in the neural mechanisms of social deficits related to ASD.

Network and Evolutionary Analysis of Human Epigenetic Regulators to Unravel Disease Associations

We carried out a system-level analysis of epigenetic regulators (ERs) and detailed the protein–protein interaction (PPI) network characteristics of disease-associated ERs. We found that most diseases associated with ERs can be clustered into two large groups, cancer diseases and developmental diseases. ER genes formed a highly interconnected PPI subnetwork, indicating a high tendency to interact and agglomerate with one another. We used the disease module detection (DIAMOnD) algorithm to expand the PPI subnetworks into a comprehensive cancer disease ER network (CDEN) and developmental disease ER network (DDEN). Using the transcriptome from early mouse developmental stages, we identified the gene co-expression modules significantly enriched for the CDEN and DDEN gene sets, which indicated the stage-dependent roles of ER-related disease genes during early embryonic development. The evolutionary rate and phylogenetic age distribution analysis indicated that the evolution of CDEN and DDEN genes was mostly constrained, and these genes exhibited older evolutionary age. Our analysis of human polymorphism data revealed that genes belonging to DDEN and Seed-DDEN were more likely to show signs of recent positive selection in human history. This finding suggests a potential association between positive selection of ERs and risk of developmental diseases through the mechanism of antagonistic pleiotropy.

Novel PET Biomarkers to Disentangle Molecular Pathways across Age-Related Neurodegenerative Diseases

There is a need to disentangle the etiological puzzle of age-related neurodegenerative diseases, whose clinical phenotypes arise from known, and as yet unknown, pathways that can act distinctly or in concert. Enhanced sub-phenotyping and the identification of in vivo biomarker-driven signature profiles could improve the stratification of patients into clinical trials and, potentially, help to drive the treatment landscape towards the precision medicine paradigm. The rapidly growing field of neuroimaging offers valuable tools to investigate disease pathophysiology and molecular pathways in humans, with the potential to capture the whole disease course starting from preclinical stages. Positron emission tomography (PET) combines the advantages of a versatile imaging technique with the ability to quantify, to nanomolar sensitivity, molecular targets in vivo. This review will discuss current research and available imaging biomarkers evaluating dysregulation of the main molecular pathways across age-related neurodegenerative diseases. The molecular pathways focused on in this review involve mitochondrial dysfunction and energy dysregulation; neuroinflammation; protein misfolding; aggregation and the concepts of pathobiology, synaptic dysfunction, neurotransmitter dysregulation and dysfunction of the glymphatic system. The use of PET imaging to dissect these molecular pathways and the potential to aid sub-phenotyping will be discussed, with a focus on novel PET biomarkers.

Epigenetic landscape of stress surfeit disorders: Key role for DNA methylation dynamics

Chronic exposure to stress throughout lifespan alters brain structure and function, inducing a maladaptive response to environmental stimuli, that can contribute to the development of a pathological phenotype. Studies have shown that hypothalamic-pituitary-adrenal (HPA) axis dysfunction is associated with various neuropsychiatric disorders, including major depressive, alcohol use and post-traumatic stress disorders. Downstream actors of the HPA axis, glucocorticoids are critical mediators of the stress response and exert their function through specific receptors, i.e., the glucocorticoid receptor (GR), highly expressed in stress/reward-integrative pathways. GRs are ligand-activated transcription factors that recruit epigenetic actors to regulate gene expression via DNA methylation, altering chromatin structure and thus shaping the response to stress. The dynamic interplay between stress response and epigenetic modifiers suggest DNA methylation plays a key role in the development of stress surfeit disorders.

Certain ortho-hydroxylated brominated ethers are promiscuous kinase inhibitors that impair neuronal signaling and neurodevelopmental processes

The developing nervous system is remarkably sensitive to environmental signals, including disruptive toxins, such as polybrominated diphenyl ethers (PBDEs). PBDEs are an environmentally pervasive class of brominated flame retardants whose neurodevelopmental toxicity mechanisms remain largely unclear. Using dissociated cortical neurons from embryonic Rattus norvegicus, we found here that chronic exposure to 6-OH-BDE-47, one of the most prevalent hydroxylated PBDE metabolites, suppresses both spontaneous and evoked neuronal electrical activity. On the basis of our previous work on mitogen-activated protein kinase (MAPK)/extracellular signal-related kinase (ERK) (MEK) biology and our observation that 6-OH-BDE-47 is structurally similar to kinase inhibitors, we hypothesized that certain hydroxylated PBDEs mediate neurotoxicity, at least in part, by impairing the MEK-ERK axis of MAPK signal transduction. We tested this hypothesis on three experimental platforms: 1) in silico, where modeling ligand-protein docking suggested that 6-OH-BDE-47 is a promiscuous ATP-competitive kinase inhibitor; 2) in vitro in dissociated neurons, where 6-OH-BDE-47 and another specific hydroxylated BDE metabolite similarly impaired phosphorylation of MEK/ERK1/2 and activity-induced transcription of a neuronal immediate early gene; and 3) in vivo in Drosophila melanogaster, where developmental exposures to 6-OH-BDE-47 and a MAPK inhibitor resulted in offspring displaying similarly increased frequency of mushroom-body β-lobe midline crossing, a metric of axonal guidance. Taken together, our results support that certain ortho-hydroxylated PBDE metabolites are promiscuous kinase inhibitors and can cause disruptions of critical neurodevelopmental processes, including neuronal electrical activity, pre-synaptic functions, MEK-ERK signaling, and axonal guidance.

BRD4 inhibition exerts anti-viral activity through DNA damage-dependent innate immune responses

Chromatin dynamics regulated by epigenetic modification is crucial in genome stability and gene expression. Various epigenetic mechanisms have been identified in the pathogenesis of human diseases. Here, we examined the effects of ten epigenetic agents on pseudorabies virus (PRV) infection by using GFP-reporter assays. Inhibitors of bromodomain protein 4 (BRD4), which receives much more attention in cancer than viral infection, was found to exhibit substantial anti-viral activity against PRV as well as a range of DNA and RNA viruses. We further demonstrated that BRD4 inhibition boosted a robust innate immune response. BRD4 inhibition also de-compacted chromatin structure and induced the DNA damage response, thereby triggering the activation of cGAS-mediated innate immunity and increasing host resistance to viral infection both in vitro and in vivo. Mechanistically, the inhibitory effect of BRD4 inhibition on viral infection was mainly attributed to the attenuation of viral attachment. Our findings reveal a unique mechanism through which BRD4 inhibition restrains viral infection and points to its potent therapeutic value for viral infectious diseases.

BRD4 has been well investigated in tumorigenesis for its contribution to chromatin remodeling and gene transcription. BRD4 inhibitors are used as promising chemotherapeutic drugs for cancer therapy. Here, we show a unique mechanism through which BRD4 inhibition broadly inhibits attachment of DNA and RNA viruses through DNA damage-dependent antiviral innate immune activation via the cGAS-STING pathway, in both cell culture and an animal model. STING-associated innate immune signaling has been considered to be a new possibility for cancer therapy, and STING agonists have been tested in early clinical trials. Our data identify BRD4 inhibitors as a potent therapy not only for viral infection but also for cancer immunotherapy.

Grape-Derived Polyphenols Ameliorate Stress-Induced Depression by Regulating Synaptic Plasticity

Major depressive disorder (MDD) is associated with stress-induced immune dysregulation and reduced brain-derived neurotrophic factor (BDNF) levels in sensitive brain regions associated with depression. Elevated levels of proinflammatory cytokines and reduced BDNF levels lead to impaired synaptic plasticity mechanisms that contribute to the pathophysiology of MDD. There is accumulating evidence that the administration of polyphenols at doses ranging from 5 to 180 mg/kg of body weight can normalize elevated levels of proinflammatory cytokines and abnormal levels of BDNF and, thus, restore impaired synaptic plasticity mechanisms that mediate depressive behavior in animal models of stress. This review will focus on the mechanisms by which grape-derived polyphenols normalize impaired synaptic plasticity and reduce depressive behavior in animal models of stress.

Chronic Ethanol Exposure Alters DNA Methylation in Neural Stem Cells: Role of Mouse Strain and Sex

Prenatal alcohol exposure (PAE) is considered as a risk factor for the development of fetal alcohol spectrum disorders (FASD). Evidence indicates that PAE affects epigenetic mechanisms (such as DNA methylation) and alters the normal differentiation and development of neural stem cells (NSC) in the fetal brain. However, PAE effects depend on several factors such as sex and strain of the studied subjects. Here, we investigated whether murine sex and strain contribute to the effects of chronic ethanol exposure on DNA methylation machinery of differentiating NSC. Further, the effects of PAE on glial lineage (including both astrocytes and oligodendrocytes) in a sex- and strain-dependent manner have not been studied yet. To examine the effects of chronic ethanol exposure on gliogenesis, we exposed differentiating NSC to glio-inductive culture conditions. Applying a standard in vitro model system, we treated male and female differentiating NSC (obtained from the forebrain of CD1 and C57BL/6 embryos at embryonic day 14.5) with chronic ethanol exposure (70 mM) for 8 days. We show that ethanol induces global DNA hypomethylation, while altering the expression of DNA methylation-related genes in a sex- and strain-specific manner. The observed change in cellular DNA methylation levels was associated with altered expression of glial markers CNPASE, GFAP, and OLIG2 in CD1 (but not C57BL/6) cells. We conclude that the impact of ethanol effect on DNA methylation is dependent on cellular sex and strain. Also, ethanol impact on neural stem cell fate commitment was only detected in cells isolated from CD1 mouse strain, but not in C57BL/6 cells. The results of the current study provide evidence that sex and strain of rodents (C57BL/6 and CD1) during gestation are important factors, which affect alcohol effects on NSC differentiation and DNA methylation. Results of this study may also help in interpreting data on the developmental toxicity of many compounds during the gestational period.

Consistent Exposure to Psychosocial Stressors and Progressive Intolerance to Stress in Individuals at Clinical High Risk for Psychosis

A body of evidence suggests that exposure to psychosocial stressors and stress sensitivity are involved in psychosis pathogenesis. However, little is known about the temporal course of these domains in those with psychosis-risk syndromes. Furthermore, to date, there have been no studies examining associations between psychosocial stressors and impaired stress tolerance, or how these factors might be implicated in symptom progression prior to psychosis onset. A total of 73 clinical high-risk (CHR) participants and 78 healthy controls (HCs) completed baseline measures of life event (LE) exposure and impaired stress tolerance. Additionally, 54 CHR and 57 HC participants returned to complete the same procedures at a 12-month follow-up assessment. Results indicated that when compared to HCs, CHR individuals exhibited increased LE exposure and impaired stress tolerance at baseline. Longitudinal analyses compared subgroups of CHR participants who exhibited positive symptoms worsening over the 1-year course (CHR-Prog), improved or steady (CHR-Remiss/Persist), and HCs. CHR-Prog individuals showed consistently elevated independent LEs exposure while CHR-Remiss/Persist reported a decline and HCs a steady low level across time. Furthermore, CHR-Prog exhibited increased stress intolerance, while the CHR-Remiss/Persist improved and HCs displayed consistently low levels over time. Analyses examining interrelationships between these domains showed a trend level interaction effect predicting follow-up symptoms. Taken together, results from the present study indicate an important role for exposure to stressors and increasing stress intolerance during psychosis pathogenesis. Additionally, findings indicating that decreases in stress exposure may lead to more favorable outcomes provide a promising target for novel targeted interventions.

Early-life blockade of NMDA receptors induces epigenetic abnormalities in the adult medial prefrontal cortex: possible involvement in memory impairment in trace fear conditioning

RATIONALE

Several findings indicate that early-life dysfunction of N-methyl-D-aspartate (NMDA) receptors might cause schizophrenia-like abnormalities in adulthood that might be induced by impairments in epigenetic regulation.

OBJECTIVES

In the present study, we investigated whether postnatal blockade of NMDA receptors (within the first 3 weeks of life) by the competitive antagonist CGP 37849 (CGP) might affect some epigenetic markers in the adult medial prefrontal cortex (mPFC).

METHODS

Histone H3 phosphorylation at serine 10 (H3S10ph), histone H3 acetylation at lysine 9 or 14 (H3K9ac or H3K14ac, respectively), or expression of histone deacetylase (HDAC) 2, HDAC5, myocyte enhancer factor (MEF) 2D and activity-regulated cytoskeleton-associated protein (Arc) were analysed. Moreover, we also evaluated whether the deacetylase inhibitor sodium butyrate (SB; 1.2 mg/kg, ip) could prevent behavioural and neurochemical changes in the mPFC induced by CGP during memory retrieval in the trace fear conditioning paradigm.

RESULTS

The results showed that CGP administration increased the number of H3S10ph nuclei but did not affect H3K9ac and H3K14ac or HDAC2 protein levels. However, CGP administration altered the HDAC5 mRNA and protein levels and increased the mRNA and protein levels of MEF2D. CGP also increased Arc mRNA, which was correlated with an increase in the amount of Arc DNA bound to MEF2D. SB given 2 h after training prevented impairment of the freezing response and disruption of epigenetic markers (H3S10ph, HDAC5, MEF2D) and Arc expression during memory retrieval induced by CGP administration.

CONCLUSIONS

The early-life blockade of NMDA receptors impairs some epigenetic regulatory processes in the mPFC that are involved in fear memory formation.

Genetic Advance in Depressive Disorder

Major depressive disorder (MDD) and bipolar disorder (BPD) are both chronic, severe mood disorder with high misdiagnosis rate, leading to substantial health and economic burdens to patients around the world. There is a high misdiagnosis rate of bipolar depression (BD) just based on symptomology in depressed patients whose previous manic or mixed episodes have not been well recognized. Therefore, it is important for psychiatrists to identify these two major psychiatric disorders. Recently, with the accumulation of clinical sample sizes and the advances of methodology and technology, certain progress in the genetics of major depression and bipolar disorder has been made. This article reviews the candidate genes for MDD and BD, genetic variation loci, chromosome structural variation, new technologies, and new methods.

Methylmercury Epigenetics

Methylmercury (MeHg) has conventionally been investigated for effects on nervous system development. As such, epigenetic modifications have become an attractive mechanistic target, and research on MeHg and epigenetics has rapidly expanded in the past decade. Although, these inquiries are a recent advance in the field, much has been learned in regards to MeHg-induced epigenetic modifications, particularly in the brain. In vitro and in vivo controlled exposure studies illustrate that MeHg effects microRNA (miRNA) expression, histone modifications, and DNA methylation both globally and at individual genes. Moreover, some effects are transgenerationally inherited, as organisms not directly exposed to MeHg exhibited biological and behavioral alterations. miRNA expression generally appears to be downregulated consequent to exposure. Further, global histone acetylation also seems to be reduced, persist at distinct gene promoters, and is contemporaneous with enhanced histone methylation. Moreover, global DNA methylation appears to decrease in brain-derived tissues, but not in the liver; however, selected individual genes in the brain are hypermethylated. Human epidemiological studies have also identified hypo- or hypermethylated individual genes, which correlated with MeHg exposure in distinct populations. Intriguingly, several observed epigenetic modifications can be correlated with known mechanisms of MeHg toxicity. Despite this knowledge, however, the functional consequences of these modifications are not entirely evident. Additional research will be necessary to fully comprehend MeHg-induced epigenetic modifications and the impact on the toxic response.

Targeted Downregulation of kdm4a Ameliorates Tau-engendered Defects in Drosophila melanogaster

BACKGROUND

Tauopathies, a class of neurodegenerative diseases that includes Alzheimer's disease (AD), are characterized by the deposition of neurofibrillary tangles composed of hyperphosphorylated tau protein in the human brain. As abnormal alterations in histone acetylation and methylation show a cause and effect relationship with AD, we investigated the role of several Jumonji domain-containing histone demethylase (JHDM) genes, which have yet to be studied in AD pathology.

METHODS

To examine alterations of several JHDM genes in AD pathology, we performed bioinformatics analyses of JHDM gene expression profiles in brain tissue samples from deceased AD patients. Furthermore, to investigate the possible relationship between alterations in JHDM gene expression profiles and AD pathology in vivo, we examined whether tissue-specific downregulation of JHDM Drosophila homologs (kdm) can affect tau^R406W-induced neurotoxicity using transgenic flies containing the UAS-Gal4 binary system.

RESULTS

The expression levels of JHDM1A, JHDM2A/2B, and JHDM3A/3B were significantly higher in postmortem brain tissue from patients with AD than from non-demented controls, whereas JHDM1B mRNA levels were downregulated in the brains of patients with AD. Using transgenic flies, we revealed that knockdown of kdm2 (homolog to human JHDM1), kdm3 (homolog to human JHDM2), kdm4a (homolog to human JHDM3A), or kdm4b (homolog to human JHDM3B) genes in the eye ameliorated the tau^R406W-engendered defects, resulting in less severe phenotypes. However, kdm4a knockdown in the central nervous system uniquely ameliorated tau^R406W-induced locomotion defects by restoring heterochromatin.

CONCLUSION

Our results suggest that downregulation of kdm4a expression may be a potential therapeutic target in AD.

Epigenetic Effects of Polybrominated Diphenyl Ethers on Human Health

Disruption of epigenetic regulation by environmental toxins is an emerging area of focus for understanding the latter's impact on human health. Polybrominated diphenyl ethers (PBDEs), one such group of toxins, are an environmentally pervasive class of brominated flame retardants that have been extensively used as coatings on a wide range of consumer products. Their environmental stability, propensity for bioaccumulation, and known links to adverse health effects have evoked extensive research to characterize underlying biological mechanisms of toxicity. Of particular concern is the growing body of evidence correlating human exposure levels to behavioral deficits related to neurodevelopmental disorders. The developing nervous system is particularly sensitive to influence by environmental signals, including dysregulation by toxins. Several major modes of actions have been identified, but a clear understanding of how observed effects relate to negative impacts on human health has not been established. Here, we review the current body of evidence for PBDE-induced epigenetic disruptions, including DNA methylation, chromatin dynamics, and non-coding RNA expression while discussing the potential relationship between PBDEs and neurodevelopmental disorders.

Neuroscience and mental state issues in forensic assessment

Neuroscience has already changed how the law understands an individual's cognitive processes, how those processes shape behavior, and how bio-psychosocial history and neurodevelopmental approaches provide information, which is critical to understanding mental states underlying behavior, including criminal behavior. In this paper, we briefly review the state of forensic assessment of mental conditions in the relative culpability of criminal defendants, focused primarily on the weaknesses of current approaches. We then turn to focus on neuroscience approaches and how they have the potential to improve assessment, but with significant risks and limitations.

Neuroimaging Biomarkers for Alzheimer's Disease

Currently, over five million Americans suffer with Alzheimer’s disease (AD). In the absence of a cure, this number could increase to 13.8 million by 2050. A critical goal of biomedical research is to establish indicators of AD during the preclinical stage (i.e. biomarkers) allowing for early diagnosis and intervention. Numerous advances have been made in developing biomarkers for AD using neuroimaging approaches. These approaches offer tremendous versatility in terms of targeting distinct age-related and pathophysiological mechanisms such as structural decline (e.g. volumetry, cortical thinning), functional decline (e.g. fMRI activity, network correlations), connectivity decline (e.g. diffusion anisotropy), and pathological aggregates (e.g. amyloid and tau PET). In this review, we survey the state of the literature on neuroimaging approaches to developing novel biomarkers for the amnestic form of AD, with an emphasis on combining approaches into multimodal biomarkers. We also discuss emerging methods including imaging epigenetics, neuroinflammation, and synaptic integrity using PET tracers. Finally, we review the complementary information that neuroimaging biomarkers provide, which highlights the potential utility of composite biomarkers as suitable outcome measures for proof-of-concept clinical trials with experimental therapeutics.

Adolescent social isolation affects parvalbumin expression in the medial prefrontal cortex in the MAM-E17 model of schizophrenia

Altered parvalbumin (PV) expression is observed in the prefrontal cortex of subjects with schizophrenia. Environmental context, particularly during adolescence, might regulate PV expression. In the present study, we investigated the effect of adolescent social isolation (SI) on PV expression in the medial prefrontal cortex in a neurodevelopmental model (MAM-E17) of schizophrenia. SI exposure occurred from postnatal day 30 to 40, followed by resocialization until late adolescence or early adulthood. PV mRNA and protein levels, as well as the number of PV cells, were analysed at these ages. Moreover, epigenetic regulation of PV expression by histone methylation was examined by measuring the total and PV gene-bound H3K4me3 levels. MAM only decreased levels of the PV mRNA and protein in adulthood. Decreases in total H3K4me3 levels and its level at the PV gene were also observed at this age. In contrast, in late adolescence, SI induced a decrease in the expression of the PV mRNA in the MAM group that was related to the reduction in total and PV gene-bound H3K4me3 levels. However, at this age, SI increased the levels of the PV protein in both the control and MAM groups. In adulthood, SI did not affect PV mRNA or H3K4me3 levels but decreased levels of the PV protein in both groups. Both MAM and SI failed to change the number of PV cells at any age. The results indicate that adolescent SI accelerated epigenetic impairments of PV expression in MAM-E17 rats; however, subsequent resocialization abolished this dysfunction, but failed to prevent alterations in PV protein.

Epigenetic Factors in Late-Onset Alzheimer's Disease: MTHFR and CTH Gene Polymorphisms, Metabolic Transsulfuration and Methylation Pathways, and B Vitamins

DNA methylation and other epigenetic factors are important in the pathogenesis of late-onset Alzheimer's disease (LOAD). Methylenetetrahydrofolate reductase (MTHFR) gene mutations occur in most elderly patients with memory loss. MTHFR is critical for production of S-adenosyl-l-methionine (SAM), the principal methyl donor. A common mutation (1364T/T) of the cystathionine-γ-lyase (CTH) gene affects the enzyme that converts cystathionine to cysteine in the transsulfuration pathway causing plasma elevation of total homocysteine (tHcy) or hyperhomocysteinemia-a strong and independent risk factor for cognitive loss and AD. Other causes of hyperhomocysteinemia include aging, nutritional factors, and deficiencies of B vitamins. We emphasize the importance of supplementing vitamin B12 (methylcobalamin), vitamin B₉ (folic acid), vitamin B₆ (pyridoxine), and SAM to patients in early stages of LOAD.