Prospects for the development of epigenetic drugs for CNS conditions

DNMT3A dysfunction promotes neuroinflammation and exacerbates acute ischemic stroke

Somatic mutations related to clonal hematopoiesis of indeterminate potential (CHIP) are risk factors for stroke. The impact of DNMT3A, the most mutated gene in CHIP, on clinical functional outcomes of acute ischemic stroke (AIS) remains unclear. In a well-characterized cohort of 8524 ischemic stroke patients, we demonstrated that DNMT3A-driven CHIP was significantly associated with neurological disability in these patients. With a stroke mouse model of transient middle cerebral artery occlusion (tMCAO), we demonstrated that DNMT3A protein levels in the brain penumbra increased. The DNMT3A inhibitor RG108 administration amplified neutrophil proliferation in the blood, promoted neutrophil infiltration into the brain penumbra, and exaggerated proinflammatory activation in tMCAO male mice. DNMT3A inhibition also significantly increased infarct volume and worsened neurobehavioral function in tMCAO male mice. In conclusion, DNMT3A somatic mutations are associated with worsened neurological disability in some patients with AIS, potentially through increased neutrophil proliferation and infiltration in the ischemic brain region. These findings suggest a possible mechanism for proinflammatory activation and tissue damage in the affected brain tissue, highlighting the need for further research in this area.

Rethinking neurodegenerative diseases: neurometabolic concept linking lipid oxidation to diseases in the central nervous system

ABSTRACT

Currently, there is a lack of effective medicines capable of halting or reversing the progression of neurodegenerative disorders, including amyotrophic lateral sclerosis, Parkinson's disease, multiple sclerosis, or Alzheimer's disease. Given the unmet medical need, it is necessary to reevaluate the existing paradigms of how to target these diseases. When considering neurodegenerative diseases from a systemic neurometabolic perspective, it becomes possible to explain the shared pathological features. This innovative approach presented in this paper draws upon extensive research conducted by the authors and researchers worldwide. In this review, we highlight the importance of metabolic mitochondrial dysfunction in the context of neurodegenerative diseases. We provide an overview of the risk factors associated with developing neurodegenerative disorders, including genetic, epigenetic, and environmental factors. Additionally, we examine pathological mechanisms implicated in these diseases such as oxidative stress, accumulation of misfolded proteins, inflammation, demyelination, death of neurons, insulin resistance, dysbiosis, and neurotransmitter disturbances. Finally, we outline a proposal for the restoration of mitochondrial metabolism, a crucial aspect that may hold the key to facilitating curative therapeutic interventions for neurodegenerative disorders in forthcoming advancements.

Methylation Patterns of the FKBP5 Gene in Association with Childhood Maltreatment and Depressive Disorders

Childhood maltreatment is an important risk factor for adult depression and has been associated with changes in the hypothalamic pituitary adrenal (HPA) axis, including cortisol secretion and methylation of the FKBP5 gene. Furthermore, associations between depression and HPA changes have been reported. This study investigated the associations of whole-blood FKBP5 mRNA levels, serum cortisol levels, childhood maltreatment, and depressive symptoms with the whole-blood methylation status (assessed via target bisulfite sequencing) of 105 CpGs at the FKBP5 locus using data from the general population-based Study of Health in Pomerania (SHIP) (N = 203). Both direct and interaction effects with the rs1360780 single-nucleotide polymorphism were investigated. Nominally significant associations of main effects on methylation of a single CpG site were observed at intron 3, intron 7, and the 3'-end of the gene. Additionally, methylation at two clusters at the 3'-end and intron 7 were nominally associated with childhood maltreatment × rs1360780 and depressive symptoms × rs1360780, respectively. The results add to the understanding of molecular mechanisms underlying the emergence of depression and could aid the development of personalised depression therapy and drug development.

Drug Discovery Targeting Nuclear Receptor Binding SET Domain Protein 2 (NSD2)

Nuclear receptor binding SET domain proteins (NSDs) catalyze the mono- or dimethylation of histone 3 lysine 36 (H3K36me1 and H3K36me2), using S-adenosyl-l-methionine (SAM) as a methyl donor. As a key member of the NSD family of proteins, NSD2 plays an important role in the pathogenesis and progression of various diseases such as cancers, inflammations, and infectious diseases, serving as a promising drug target. Developing potent and specific NSD2 inhibitors may provide potential novel therapeutics. Several NSD2 inhibitors and degraders have been discovered while remaining in the early stage of drug development. Excitingly, KTX-1001, a selective NSD2 inhibitor, has entered clinical trials. In this Perspective, the structures and functions of NSD2, its roles in various human diseases, and the recent advances in drug discovery strategies targeting NSD2 have been summarized. The challenges, opportunities, and future directions for developing NSD2 inhibitors and degraders are also discussed.

SARS-CoV-2 (COVID-19) as a possible risk factor for neurodevelopmental disorders

Pregnant women constitute one of the most vulnerable populations to be affected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the cause of coronavirus disease 2019. SARS-CoV-2 infection during pregnancy could negatively impact fetal brain development via multiple mechanisms. Accumulating evidence indicates that mother to fetus transmission of SARS-CoV-2 does occur, albeit rarely. When it does occur, there is a potential for neuroinvasion via immune cells, retrograde axonal transport, and olfactory bulb and lymphatic pathways. In the absence of maternal to fetal transmission, there is still the potential for negative neurodevelopmental outcomes as a consequence of disrupted placental development and function leading to preeclampsia, preterm birth, and intrauterine growth restriction. In addition, maternal immune activation may lead to hypomyelination, microglial activation, white matter damage, and reduced neurogenesis in the developing fetus. Moreover, maternal immune activation can disrupt the maternal or fetal hypothalamic-pituitary-adrenal (HPA) axis leading to altered neurodevelopment. Finally, pro-inflammatory cytokines can potentially alter epigenetic processes within the developing brain. In this review, we address each of these potential mechanisms. We propose that SARS-CoV-2 could lead to neurodevelopmental disorders in a subset of pregnant women and that long-term studies are warranted.

Advancement of epigenetics in stroke

A wide plethora of intervention procedures, tissue plasminogen activators, mechanical thrombectomy, and several neuroprotective drugs were reported in stroke research over the last decennium. However, against this vivid background of newly emerging pieces of evidence, there is little to no advancement in the overall functional outcomes. With the advancement of epigenetic tools and technologies associated with intervention medicine, stroke research has entered a new fertile. The stroke involves an overabundance of inflammatory responses arising in part due to the body's immune response to brain injury. Neuroinflammation contributes to significant neuronal cell death and the development of functional impairment and even death in stroke patients. Recent studies have demonstrated that epigenetics plays a key role in post-stroke conditions, leading to inflammatory responses and alteration of the microenvironment within the injured tissue. In this review, we summarize the progress of epigenetics which provides an overview of recent advancements on the emerging key role of secondary brain injury in stroke. We also discuss potential epigenetic therapies related to clinical practice.

A Network-Guided Approach to Discover Phytochemical-Based Anticancer Therapy: Targeting MARK4 for Hepatocellular Carcinoma

MAP/microtubule affinity-regulating kinase 4 (MARK4) is associated with various biological functions, including neuronal migration, cell polarity, microtubule dynamics, apoptosis, and cell cycle regulation, specifically in the G1/S checkpoint, cell signaling, and differentiation. It plays a critical role in different types of cancers. Hepatocellular carcinoma (HCC) is the one of the most common forms of liver cancer caused due to mutations, epigenetic aberrations, and altered gene expression patterns. Here, we have applied an integrated network biology approach to see the potential links of MARK4 in HCC, and subsequently identified potential herbal drugs. This work focuses on the naturally-derived compounds from medicinal plants and their properties, making them targets for potential anti-hepatocellular treatments. We further analyzed the HCC mutated genes from the TCGA database by using cBioPortal and mapped out the MARK4 targets among the mutated list. MARK4 and Mimosin, Quercetin, and Resveratrol could potentially interact with critical cancer-associated proteins. A set of the hepatocellular carcinoma altered genes is directly the part of infection, inflammation, immune systems, and cancer pathways. Finally, we conclude that among all these drugs, Gingerol and Fisetin appear to be the highly promising drugs against MARK4-based targets, followed by Quercetin, Resveratrol, and Apigenin.

SAMe, Choline, and Valproic Acid as Possible Epigenetic Drugs: Their Effects in Pregnancy with a Special Emphasis on Animal Studies

In this review, we discuss the functions and main effects on pregnancy outcomes of three agents that have the ability to induce epigenetic modifications: valproic acid (VPA), a well-known teratogen that is a histone deacetylase inhibitor; S-adenosylmethionine (SAMe), the most effective methyl donor; and choline, an important micronutrient involved in the one methyl group cycle and in the synthesis of SAMe. Our aim was to describe the possible effects of these compounds when administered during pregnancy on the developing embryo and fetus or, if administered postnatally, their effects on the developing child. These substances are able to modify gene expression and possibly alleviate neurobehavioral changes in disturbances that have epigenetic origins, such as autism spectrum disorder (ASD), depression, Rett syndrome, and fetal alcohol spectrum disorder (FASD). Valproic acid and SAMe are antagonistic epigenetic modulators whether administered in utero or postnatally. However, VPA is a major human teratogen and, whenever possible, should not be used by pregnant women. Most currently relevant data come from experimental animal studies that aimed to explore the possibility of using these substances as epigenetic modifiers and possible therapeutic agents. In experimental animals, each of these substances was able to alleviate the severity of several well-known diseases by inducing changes in the expression of affected genes or by other yet unknown mechanisms. We believe that additional studies are needed to further explore the possibility of using these substances, and similar compounds, for the treatment of ”epigenetic human diseases”.

Epigenetic Basis of Psychiatric Disorders: A Narrative Review

BACKGROUND

Psychiatric disorders are complex, multifactorial illnesses with a demonstrated biological component in their etiopathogenesis. Epigenetic modifications, through the modulation of DNA methylation, histone modifications and RNA interference, tune tissue-specific gene expression patterns and play a relevant role in the etiology of psychiatric illnesses.

OBJECTIVE

This review aims to discuss the epigenetic mechanisms involved in psychiatric disorders, their modulation by environmental factors and their interactions with genetic variants, in order to provide a comprehensive picture of their mutual crosstalk.

METHODS

In accordance with the PRISMA guidelines, systematic searches of Medline, EMBASE, PsycINFO, Web of Science, Scopus, and the Cochrane Library were conducted.

RESULTS

Exposure to environmental factors, such as poor socio-economic status, obstetric complications, migration, and early life stressors, may lead to stable changes in gene expression and neural circuit function, playing a role in the risk of psychiatric diseases. The most replicated genes involved by studies using different techniques are discussed. Increasing evidence indicates that these sustained abnormalities are maintained by epigenetic modifications in specific brain regions and they interact with genetic variants in determining the risk of psychiatric disorders.

CONCLUSION

An increasing amount of evidence suggests that epigenetics plays a pivotal role in the etiopathogenesis of psychiatric disorders. New therapeutic approaches may work by reversing detrimental epigenetic changes that occurred during the lifespan.

Associations of age, sex, sexual abuse, and genotype with monoamine oxidase a gene methylation

Epigenome-wide studies report higher methylation among women than men with decreasing levels with age. Little is known about associations of sex and age with methylation of monoamine oxidase A (MAOA). Methylation of the first exonic and partial first intronic region of MAOA has been shown to strengthen associations of interactions of MAOA-uVNTR genotypes and adversity with aggression and substance misuse. Our study examined associations of sex and age with MAOA first exon and intron methylation levels in 252 women and 157 men aged 14–73 years. Participants included adolescents recruited at a substance misuse clinic, their siblings and parents, and healthy women. Women showed ~ 50% higher levels of exonic, and ~ 15% higher intronic, methylation than men. Methylation levels were similar between younger (M = 22.7 years) and older (M = 46.1 years) participants, and stable across age. Age modified few associations of methylation levels with sex. MAOA genotypes modified few associations of methylation with sex and age. Higher methylation levels among women were not explained by genotype, nor interaction of genotype and sexual abuse. Findings were similar after adjusting for lifetime diagnoses of substance dependence (women = 24.3%; men = 34.2%). Methylation levels were higher among women who experienced sexual abuse than women who did not. Results extend on prior studies by showing that women display higher levels of methylation than men within first intronic/exonic regions of MAOA, which did not decrease with age in either sex. Findings were not conditioned by genotype nor interactions of genotype and trauma, and indicate X-chromosome inactivation.

Urine metabolic phenotyping in children with nocturnal enuresis and comorbid neurobehavioral disorders

Nocturnal enuresis (NE) is a common problem among 10% school-aged children. The etiologies underlying childhood NE is complex and not fully understood nowadays. Nevertheless, increasing evidence suggests a potential link between neurobehavioral disorders and enuresis in children. In this study, we aimed to explore novel metabolomic insights into the pathophysiology of NE and also, its association with pediatric psychiatric problems. Urine collected from 41 bedwetting children and 27 healthy control children was analyzed by using ¹H-nuclear magnetic resonance spectroscopy from August 2017 to December 2018. At regular follow-up, there were 14 children with refractory NE having a diagnosis of attention deficient hyperactivity disorder (ADHD) or anxiety. Eventually, we identified eight significantly differential urinary metabolites and particularly increased urinary excretion of betaine, creatine and guanidinoacetate linked to glycine, serine and threonine metabolism were associated with a comorbidity of neurobehavioral disorders in refractory bedwetting children. Notably, based on physiological functions of betaine acting as a renal osmolyte and methyl group donor, we speculated its potential role in modulation of renal and/or central circadian clock systems, becoming a useful urinary metabolic marker in diagnosis of treatment-resistant NE in children affected by these two disorders.

Fundamental and clinical neuropharmacology, a terra incognita with constantly expanding frontiers

Neuropharmacology is the science that studies the effects of drugs on the central nervous system. Examining the recent history of neuropharmacology allows us to identify future challenges and to project into the future. The contemporary history of neuropharmacology begins with the empirical use of psychotropic alkaloids in barbiturate preparations. Then the discovery of neuroleptics in the 1950s truly opened up the field of pharmacological science, with psychopharmacological clinical exploration in psychiatry, complemented by the contributions of neurochemists and biochemists discovering and exploring neurotransmission. These studies also contributed to the development of dopaminergic and serotonergic drugs used in neurology. The more recent period brought the advent of neuropsychopharmacology, sharing therapeutic targets in neurology and psychiatry on the one hand, and a translational research approach on the other. Moreover, the pharmacology of brain drugs is still a growing discipline in 2020. Despite emerging pharmacological concepts (biased agonists, glial targeting, epigenetic therapeutics, etc.), entire areas of brain-based therapeutics need to be renewed, particularly in psychiatry, offering great challenges to a new generation of pharmacologists and clinicians.

The Role of Butyric Acid in Treatment Response in Drug-Naïve First Episode Schizophrenia

Background: Butyric acid, a major short-chain fatty acid (SCFA), has an important role in the microbiota-gut-brain axis and brain function. This study investigated the role of butyric acid in treatment response in drug-naïve first episode schizophrenia. Methods: The study recruited 56 Chinese Han schizophrenia inpatients with normal body weight and 35 healthy controls. Serum levels of butyric acid were measured using Gas Chromatography-Mass Spectrometer (GC-MS) analysis at baseline (for all participants) and 24 weeks after risperidone treatment (for patients). Clinical symptoms were measured using the Positive and Negative Syndrome Scale (PANSS) for patients at both time points. Results: At baseline, there was no significant difference in serum levels of butyric acid between patients and healthy controls (p = 0.206). However, there was a significant increase in serum levels of butyric acid in schizophrenia patients after 24-week risperidone treatment (p = 0.030). The PANSS total and subscale scores were decreased significantly after 24-week risperidone treatment (p's < 0.001). There were positive associations between baseline serum levels of butyric acid and the reduction ratio of the PANSS total and subscale scores after controlling for age, sex, education, and duration of illness (p's < 0.05). Further, there was a positive association between the increase in serum levels of butyric acid and the reduction of the PANSS positive symptoms subscale scores (r = 0.38, p = 0.019) after controlling for potential confounding factors. Conclusions: Increased serum levels of butyric acid might be associated with a favorable treatment response in drug-naïve, first episode schizophrenia. The clinical implications of our findings were discussed.

Neurogenetic and Neuroepigenetic Mechanisms in Cognitive Health and Disease

Over the last two decades, the explosion of experimental, computational, and high-throughput technologies has led to critical insights into how the brain functions in health and disease. It has become increasingly clear that the vast majority of brain activities result from the complex entanglement of genetic factors, epigenetic changes, and environmental stimuli, which, when altered, can lead to neurodegenerative and neuropsychiatric disorders. Nevertheless, a complete understanding of the molecular mechanisms underlying neuronal activities and higher-order cognitive processes continues to elude neuroscientists. Here, we provide a concise overview of how the interaction between the environment and genetic as well as epigenetic mechanisms shapes complex neuronal processes such as learning, memory, and synaptic plasticity. We then consider how this interaction contributes to the development of neurodegenerative and psychiatric disorders, and how it can be modeled to predict phenotypic variability and disease risk. Finally, we outline new frontiers in neurogenetic and neuroepigenetic research and highlight the challenges these fields will face in their quest to decipher the molecular mechanisms governing brain functioning.

Cognitive Improvement by Vorinostat through Modulation of Endoplasmic Reticulum Stress in a Corticosterone-Induced Chronic Stress Model in Mice

Chronic stress is the leading cause of memory impairment today. Various stress-based models are being developed for studying cognitive impairment. Repurposing of existing drugs in a new pharmacology class is the safest and cheapest option for treatment instead of new drug discovery. Vorinostat (VOR) is the first histone deacetylase (HDAC) inhibitor approved for the treatment of cutaneous T-cell lymphoma by the U.S. FDA. VOR follows the rule of five and is reported to cross the blood-brain barrier. Therefore, we aimed to evaluate the procognitive potential of VOR (25 mg/kg) administered by intraperitoneal (ip) route in a stress-based model of chronic corticosterone (CORT) injections (20 mg/kg, subcutaneously (sc)). The study comprised six groups. Normal mice were administered vehicle (VEH) (days 1-21, sc) in the first group, VOR (days 8-21, 25 mg/kg, ip) in the second group, and fluoxetine (FLX) (days 8-21, 15 mg/kg, oral) in the third group. Mice in the remaining three groups were given 20 mg/kg (sc) CORT for 21 days, and VOR (days 8-21, 25 mg/kg, ip) or FLX (days 8-21, 15 mg/kg, oral) was additionally administered to the treatment groups. Behavioral tests such as Morris water maze test, novel object recognition test, and object in place test were performed at the end of the dosing schedule to assess cognition. After behavior tests, mice were sacrificed, and hippocampus was separated from brain tissue for reverse transcriptase polymerase chain reaction (RT-PCR), Western blot, and immunohistochemistry studies. VOR treatment attenuated endoplasmic reticulum (ER) stress in CORT mice as evident from the reduction in DNA damage-inducible transcript 3 (Ddit3) (gene encoding CHOP), caspase 12 (Casp12), and calpain-2 (Capn2) mRNA levels, and cleaved caspase 3 (CASP3) protein expression. Bax inhibitor-1 (BI-1) was significantly increased in VOR-treated CORT mice. VOR also reversed CORT induced increase in HDAC2 level in the CA3 region. The protective effects of VOR were comparable to that of FLX in CORT mice. Thus, VOR has the potential to reverse cognitive dysfunction via modulation of ER stress markers and HDAC2.

The epigenetics of perinatal stress

Early life adversity is associated with long-term effects on physical and mental health later in life, but the mechanisms are yet unclear. Epigenetic mechanisms program cell-type-specific gene expression during development, enabling one genome to be programmed in many ways, resulting in diverse stable profiles of gene expression in different cells and organs in the body. DNA methylation, an enzymatic covalent modification of DNA, has been one of the principal epigenetic mechanisms investigated. Emerging evidence is consistent with the idea that epigenetic processes are involved in embedding the impact of early-life experience in the genome and mediating between social environments and later behavioral phenotypes. Whereas there is evidence supporting this hypothesis in animal studies, human studies have been less conclusive. A major problem is the fact that the brain is inaccessible to epigenetic studies in humans and the relevance of DNA methylation in peripheral tissues to behavioral phenotypes has been questioned. In addition, human studies are usually confounded with genetic and environmental heterogeneity and it is very difficult to derive causality. The idea that epigenetic mechanisms mediate the life-long effects of perinatal adversity has attractive potential implications for early detection, prevention, and intervention in mental health disorders will be discussed.


S-Adenosine Methionine (SAMe) and Valproic Acid (VPA) as Epigenetic Modulators: Special Emphasis on their Interactions Affecting Nervous Tissue during Pregnancy

S-adenosylmethionine (SAMe) is involved in many transmethylation reactions in most living organisms and is also required in the synthesis of several substances such as monoamine neurotransmitters and the N-methyl-D-aspartate (NMDA) receptor. Due to its important role as an epigenetic modulator, we discuss in some length the process of DNA methylation and demethylation and the critical periods of epigenetic modifications in the embryo, fetus, and thereafter. We also discuss the effects of SAMe deficiency and the attempts to use SAMe for therapeutic purposes such as the treatment of major depressive disorder, Alzheimer disease, and other neuropsychiatric disorders. SAMe is an approved food additive and as such is also used during pregnancy. Yet, there seems to scanty data on the possible effects of SAMe on the developing embryo and fetus. Valproic acid (VPA) is a well-tolerated and effective antiepileptic drug that is also used as a mood stabilizer. Due to its high teratogenicity, it is contraindicated in pregnancy. A major mechanism of its action is histone deacetylase inhibition, and therefore, it acts as an epigenetic modulator, mainly on the brain. This prompted clinical trials using VPA for additional indications i.e., treating degenerative brain disease such as Alzheimer disease, dementia, HIV, and even cancer. Therefore, we discuss the possible effects of VPA and SAMe on the conceptus and early postnatally, during periods of susceptibility to epigenetic modifications. VPA is also used as an inducer of autistic-like behavior in rodents and was found by us to modify gene expression when administered during the first postnatal week but not when administered to the pregnant dams on day 12 of gestation. In contrast, SAMe modified gene expression when administered on day 12 of pregnancy but not postnatally. If administered together, VPA prevented the changes in gene expression induced by prenatal SAMe administration, and SAMe prevented the gene expression changes and autistic-like behavior induced by early postnatal VPA. It is concluded that both VPA and SAMe are powerful epigenetic modifiers with antagonistic actions on the brain that will probably be used in the future more extensively for the treatment of a variety of epigenetic diseases of the nervous system.

Epimimetics: Novel Therapeutics Targeting Epigenetic Mediators and Modulators

Epigenetic alterations have been associated with a wide range of diseases. Furthermore, many therapeutic interventions modelling environmental exposures appear to involve epigenetic mechanisms. Recent progress has been made in developing drugs targeting specific epigenetic components. Here, I propose developing 'epimimetics', novel drugs that mimic or enhance therapeutic effects of epigenetic modifications.

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.

Designer epigenome modifiers enable robust and sustained gene silencing in clinically relevant human cells

Targeted modulation of gene expression represents a valuable approach to understand the mechanisms governing gene regulation. In a therapeutic context, it can be exploited to selectively modify the aberrant expression of a disease-causing gene or to provide the target cells with a new function. Here, we have established a novel platform for achieving precision epigenome editing using designer epigenome modifiers (DEMs). DEMs combine in a single molecule a DNA binding domain based on highly specific transcription activator-like effectors (TALEs) and several effector domains capable of inducing DNA methylation and locally altering the chromatin structure to silence target gene expression. We designed DEMs to target two human genes, CCR5 and CXCR4, with the aim of epigenetically silencing their expression in primary human T lymphocytes. We observed robust and sustained target gene silencing associated with reduced chromatin accessibility, increased promoter methylation at the target sites and undetectable changes in global gene expression. Our results demonstrate that DEMs can be successfully used to silence target gene expression in primary human cells with remarkably high specificity, paving the way for the establishment of a potential new class of therapeutics.

Epigenetic therapy of Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a complex and multisystem neurobehavioral disorder. The molecular mechanism of PWS is deficiency of paternally expressed gene gene or genes from the chromosome 15q11-q13. Due to imprinted gene regulation, the same genes in the maternal chromosome 15q11-q13 are structurally intact but transcriptionally repressed by an epigenetic mechanism. The unique molecular defect underlying PWS renders an exciting opportunity to explore epigenetic-based therapy to reactivate the expression of repressed PWS genes from the maternal chromosome. Inactivation of H3K9m3 methyltransferase SETDB1 and zinc finger protein ZNF274 results in reactivation of SNRPN and SNORD116 cluster from the maternal chromosomes in PWS patient iPSCs and iPSC-derived neurons, respectively. High content screening of small molecule libraries using cells derived from transgenic mice carrying the SNRPN-EGFP fusion protein has discovered that inhibitors of EHMT2/G9a, a histone 3 lysine 9 methyltransferase, are capable of reactivating expression of paternally expressed SNRPN and SNORD116 from the maternal chromosome, both in cultured PWS patient-derived fibroblasts and in a PWS mouse model. Treatment with an EMHT2/G9a inhibitor also rescues perinatal lethality and failure to thrive phenotypes in a PWS mouse model. These findings present the first evidence to support a proof-of-principle for epigenetic-based therapy for the PWS in humans.

Brain, behavior and the journey towards neuroepigenetic therapeutics

Epigenetics has brought about a major shift in our understanding of biological mechanisms and their associated health effects. Strong epigenetic components have been found to be involved in the progression of many diseases. In several human diseases, including debilitating psychiatric disorders, altered epigenetic status has been found as one of the main causes. With continuous progress on drug development, researchers are enthusiastic toward epigenetic therapeutics which could possibly reverse epigenetic modifications. In this article certain developments in epigenetic therapeutics are highlighted, the indiscriminate use of which could also be associated with potential risk. These risks may partly be due to our limited knowledge on genes and the mechanisms underlying epigenetic involvement in different diseases. Epigenetic changes are fundamentally important for a large number of bodily functions; nonspecific usage of therapeutics could be potentially harmful therefore there is a need to harness epigenetics positively.

Histone Deacetylase Inhibitors as Multitarget Ligands: New Players in Alzheimer's Disease Drug Discovery?

Histone deacetylase inhibitors (HDACIs) are responsible for controlling gene expression by modulating the acetylation status of histone proteins. Furthermore, they modulate the activity of cytoplasmic non-histone proteins. Due to the involvement of HDACs in neurodevelopment, memory formation, and cognitive processes, HDACIs have been suggested as innovative agents for the treatment of neurodegenerative disorders such as Alzheimer's disease (AD). Given their mechanisms of action and the complex nature of AD, HDACIs have been proposed for the design of novel multitarget ligands (MTLs). To this aim, the fragment responsible for HDAC inhibition has been coupled with other structures that are able to provide additional biological actions, such as antioxidant activity or the inhibition of phosphodiesterase 5, transglutaminase 2, and glycogen synthase kinase 3β. Herein we discuss recent efforts to design HDACI-based MTLs as potential disease-modifying entities.

Selective and nonselective HDAC8 inhibitors: a therapeutic patent review

Histone deacetylase 8 (HDAC8) is one of the attractive therapeutic anticancer targets. HDAC8 has been overexpressed in a variety of human cancers. Therefore, HDAC8 inhibitors offer beneficial effects in the treatment of solid and hematological tumors. Different HDAC inhibitors entered into different phases of clinical studies. However, selectivity towards specific HDAC8 enzyme is still demanding. In this patent review, a number of patented selective and nonselective HDAC8 inhibitors along with their implication as anticancer agents have been discussed in details. Molecules should possess modified fish-like structural arrangement to impart potency and selectivity towards HDAC8. This comprehensive patent analysis will surely provide newer aspects of designing selective HDAC8 inhibitors targeted to anticancer therapy in future.

Temporal Integrative Analysis of mRNA and microRNAs Expression Profiles and Epigenetic Alterations in Female SAMP8, a Model of Age-Related Cognitive Decline

A growing body of research shows that epigenetic mechanisms are critically involved in normal and pathological aging. The Senescence-Accelerated Mouse Prone 8 (SAMP8) can be considered a useful tool to better understand the dynamics of the global epigenetic landscape during the aging process since its phenotype is not fully explained by genetic factors. Here we investigated dysfunctional age-related transcriptional profiles and epigenetic programming enzymes in the hippocampus of 2- and 9-month-old SAMP8 female mice using the Senescent-Accelerated Resistant 1 (SAMR1) mouse strain as control. SAMP8 mice presented 1,062 genes dysregulated at 2 months of age, and 1,033 genes at 9 months, with 92 genes concurrently dysregulated at both ages compared to age-matched SAMR1. SAMP8 mice showed a significant decrease in global DNA methylation (5-mC) at 2 months while hydroxymethylation (5-hmC) levels were increased in SAMP8 mice at 2 and 9 months of age compared to SAMR1. These changes were accompanied by changes in the expression of several enzymes that regulate 5-mC and methylcytosine oxidation. Acetylated H3 and H4 histone levels were significantly diminished in SAMP8 mice at 2-month-old compared to SAMR1 and altered Histone DeACetylase (HDACs) profiles were detected in both young and old SAMP8 mice. We analyzed 84 different mouse miRNAs known to be altered in neurological diseases or involved in neuronal development. Compared with SAMR1, SAMP8 mice showed 28 and 17 miRNAs differentially expressed at 2 and 9 months of age, respectively; 6 of these miRNAs overlapped at both ages. We used several bioinformatic approaches to integrate our data in mRNA:miRNA regulatory networks and functional predictions for young and aged animals. In sum, our study reveals interplay between epigenetic mechanisms and gene networks that seems to be relevant for the progression toward a pathological aging and provides several potential markers and therapeutic candidates for Alzheimer's Disease (AD) and age-related cognitive impairment.

DRD4 methylation as a potential biomarker for physical aggression: An epigenome-wide, cross-tissue investigation

Epigenetic processes that regulate gene expression, such as DNA methylation (DNAm), have been linked to individual differences in physical aggression. Yet, it is currently unclear whether: (a) DNAm patterns in humans associate with physical aggression independently of other co-occurring psychiatric and behavioral symptoms; (b) whether these patterns are observable across multiple tissues; and (c) whether they may function as a causal versus noncausal biomarker of physical aggression. Here, we used a multisample, cross-tissue design to address these questions. First, we examined genome-wide DNAm patterns (buccal swabs; Illumina 450k) associated with engagement in physical fights in a sample of high-risk youth (n = 119; age = 16-24 years; 53% female). We identified one differentially methylated region in DRD4, which survived genome-wide correction, associated with physical aggression above and beyond co-occurring symptomatology (e.g., ADHD, substance use), and showed strong cross-tissue concordance with both blood and brain. Second, we found that DNAm sites within this region were also differentially methylated in an independent sample of young adults, between individuals with a history of chronic-high versus low physical aggression (peripheral T cells; ages 26-28). Finally, we ran a Mendelian randomization analysis using GWAS data from the EAGLE consortium to test for a causal association of DRD4 methylation with physical aggression. Only one genetic instrument was eligible for the analysis, and results provided no evidence for a causal association. Overall, our findings lend support for peripheral DRD4 methylation as a potential biomarker of physically aggressive behavior, with no evidence yet of a causal relationship.

Association of Childhood Adversity With Differential Susceptibility of Transdiagnostic Psychopathology to Environmental Stress in Adulthood

IMPORTANCE

Multivariable comorbidity research indicates that childhood adversity increases the risk for the development of common mental disorders. This risk is explained by underlying internalizing and externalizing transdiagnostic constructs that are amplified by environmental stressors. The differential susceptibility model suggests that this interaction of risk and environment is bidirectional: at-risk individuals will have worse outcomes in high-stress environments but better outcomes in in low-stress environments.

OBJECTIVE

To test the differential susceptibility model by examining how a history of adverse childhood experiences moderates the association between life stress and transdiagnostic psychopathology.

DESIGN, SETTING, AND PARTICIPANTS

Data came from the US National Epidemiological Survey on Alcohol and Related Conditions (NESARC), a population-based observational longitudinal survey administered to adults (≥18 years of age). Participants completed the survey at wave 1 (from 2001 through 2002) and wave 2 (from 2004 through 2005). Responses from 34 458 participants were used for the analyses from March 3, 2017, through October 8, 2018.

MAIN OUTCOMES AND MEASURES

Latent variables for internalizing-fear, internalizing-distress, externalizing, and general psychopathology were created to represent continuous levels of psychopathology in each wave. Latent variables were also created to represent continuous levels of life stress at each wave. Level of childhood adversity was characterized based on the number of types of childhood adversity experienced (no [0 types], low [1-2 types], and high [≥3 types] exposure). Analyses examined how the interaction between level of childhood adversity and adult life stress was associated with change in adult transdiagnostic psychopathology factors.

RESULTS

Of the 34 458 participants included in the analysis (58.0% women and 42.0% men; mean [SD] age, 46.0 [17.4] years at wave 1 and 49.0 [17.3] years at wave 2), 40.5% had no adverse childhood experiences, 34.6% had 1 to 2, and 24.9% had 3 or more. At wave 1, 61.5% of the sample endorsed at least 1 stressful life event and 27.2% met criteria for at least 1 mental disorder; at wave 2, these figures were 64.7% and 29.7%, respectively. Childhood adversity moderated the association between changes in adult life stress and changes in all transdiagnostic psychopathology factors. Specifically, higher levels of childhood adversity had a stronger association between adult life stress and adult transdiagnostic psychopathology factors. Further, significant differences between childhood adversity groups occurred in the mean scores of all transdiagnostic psychopathology factors for both increases and decreases in life stress, providing preliminary evidence of differential susceptibility.

CONCLUSIONS AND RELEVANCE

Results provide empirical support for childhood adversity as a differential susceptibility factor engendering heightened functional and dysfunctional reactivity to later stress.

FABP3 in the Anterior Cingulate Cortex Modulates the Methylation Status of the Glutamic Acid Decarboxylase67 Promoter Region

Polyunsaturated fatty acids (PUFAs) are essential for brain development and function. Increasing evidence has shown that an imbalance of PUFAs is associated with various human psychiatric disorders, including autism and schizophrenia. Fatty acid-binding proteins (FABPs), cellular chaperones of PUFAs, are involved in PUFA intracellular trafficking, signal transduction, and gene transcription. In this study, we show that FABP3 is strongly expressed in the GABAergic inhibitory interneurons of the male mouse anterior cingulate cortex (ACC), which is a component of the limbic cortex and is important for the coordination of cognitive and emotional behaviors. Interestingly, Fabp3 KO male mice show an increase in the expression of the gene encoding the GABA-synthesizing enzyme glutamic acid decarboxylase 67 (Gad67) in the ACC. In the ACC of Fabp3 KO mice, Gad67 promoter methylation and the binding of methyl-CpG binding protein 2 (MeCP2) and histone deacetylase 1 (HDAC1) to the Gad67 promoter are significantly decreased compared with those in WT mice. The abnormal cognitive and emotional behaviors of Fabp3 KO mice are restored by methionine administration. Notably, methionine administration normalizes Gad67 promoter methylation and its mRNA expression in the ACC of Fabp3 KO mice. These findings demonstrate that FABP3 is involved in the control of DNA methylation of the Gad67 promoter and activation of GABAergic neurons in the ACC, thus suggesting the importance of PUFA homeostasis in the ACC for cognitive and emotional behaviors.SIGNIFICANCE STATEMENT The ACC is important for emotional and cognitive processing. However, the mechanisms underlying its involvement in the control of behavioral responses are largely unknown. We show the following new observations: (1) FABP3, a PUFA cellular chaperone, is exclusively expressed in GABAergic interneurons in the ACC; (2) an increase in Gad67 expression is detected in the ACC of Fabp3 KO mice; (3) the Gad67 promoter is hypomethylated and the binding of transcriptional repressor complexes is decreased in the ACC of Fabp3 KO mice; and (4) elevated Gad67 expression and abnormal behaviors seen in Fabp3 KO mice are mostly recovered by methionine treatment. These suggest that FABP3 regulates GABA synthesis through transcriptional regulation of Gad67 in the ACC.

[Social environment, biological embedding and social inequalities in health]

The social gradient in health refers to the fact that the higher individuals rise in the social hierarchy, the better is their health. Understanding the construction of this gradient is a major challenge in social epidemiology. An original approach consists in looking at how the different exposures (chemical, physical, behavioural, psychosocial…) associated with the social environment are ultimately expressed at the biological level influencing health positively or negatively, referring to the concept of biological embedding. Data from animal models and life course epidemiology have shed new light on the biological mechanisms potentially at play. Recent discoveries from the field of epigenetics provide a better understanding of how the social environment, especially the early environment, can influence biological functioning over the long term or even over several generations. The work on the biological embedding of the social environment in connection with epigenetics still needs to be very largely consolidated, but could constitute a change of perspective in human biology, particularly by reconsidering the influence of the environment on biological functioning, which is not without consequences in terms of public health interventions.

A Methylome-Wide Association Study of Trajectories of Oppositional Defiant Behaviors and Biological Overlap With Attention Deficit Hyperactivity Disorder

In 671 mother-child (49% male) pairs from an epidemiological birth cohort, we investigated (a) prospective associations between DNA methylation (at birth) and trajectories (ages 7-13) of oppositional defiant disorder (ODD), and the ODD subdimensions of irritable and headstrong; (b) common biological pathways, indexed by DNA methylation, between ODD trajectories and attention deficit hyperactivity disorder (ADHD); (c) genetic influence on DNA methylation; and (d) prenatal risk exposure associations. Methylome-wide significant associations were identified for the ODD and headstrong, but not for irritable. Overlap analysis indicated biological correlates between ODD, headstrong, and ADHD. DNA methylation in ODD and headstrong was (to a degree) genetically influenced. DNA methylation associated with prenatal risk exposures of maternal anxiety (headstrong) and cigarette smoking (ODD and headstrong).

A brief tour of epidemiologic epigenetics and mental health

The epidemiologic study of DNA methylation (DNAm) and mental health is a burgeoning area, but confounding and reverse causation remain important to know about. Whether use of non-brain tissues is appropriate when investigating brain phenotypes depends on the hypothesis and whether the goal is causality or to identify biomarkers. Look-ups of the correspondence between DNAm in blood and brain and use of Mendelian randomization (MR) can be done to follow-up, to some degree, on the causal nature of some findings. Social scientists, health methodologists (epidemiologists), and basic scientists-thinkers who view epigenetics and mental health from different perspectives-can come together in the design and framing of findings to avoid pitfalls and innovate beyond what each could do alone.

GABAergic inhibitory neurons as therapeutic targets for cognitive impairment in schizophrenia

Schizophrenia is considered primarily as a cognitive disorder. However, functional outcomes in schizophrenia are limited by the lack of effective pharmacological and psychosocial interventions for cognitive impairment. GABA (gamma-aminobutyric acid) interneurons are the main inhibitory neurons in the central nervous system (CNS), and they play a critical role in a variety of pathophysiological processes including modulation of cortical and hippocampal neural circuitry and activity, cognitive function-related neural oscillations (eg, gamma oscillations) and information integration and processing. Dysfunctional GABA interneuron activity can disrupt the excitatory/inhibitory (E/I) balance in the cortex, which could represent a core pathophysiological mechanism underlying cognitive dysfunction in schizophrenia. Recent research suggests that selective modulation of the GABAergic system is a promising intervention for the treatment of schizophrenia-associated cognitive defects. In this review, we summarized evidence from postmortem and animal studies for abnormal GABAergic neurotransmission in schizophrenia, and how altered GABA interneurons could disrupt neuronal oscillations. Next, we systemically reviewed a variety of up-to-date subtype-selective agonists, antagonists, positive and negative allosteric modulators (including dual allosteric modulators) for α5/α3/α2 GABA_A and GABA_B receptors, and summarized their pro-cognitive effects in animal behavioral tests and clinical trials. Finally, we also discuss various representative histone deacetylases (HDAC) inhibitors that target GABA system through epigenetic modulations, GABA prodrug and presynaptic GABA transporter inhibitors. This review provides important information on current potential GABA-associated therapies and future insights for development of more effective treatments.

Annual Research Review: DNA methylation as a mediator in the association between risk exposure and child and adolescent psychopathology

BACKGROUND

DNA methylation (DNAm) is a potential mechanism for propagating the effects of environmental exposures on child and adolescent mental health. In recent years, this field has experienced steady growth.

METHODS

We provide a strategic review of the current child and adolescent literature to evaluate evidence for a mediating role of DNAm in the link between environmental risks and psychopathological outcomes, with a focus on internalising and externalising difficulties.

RESULTS

Based on the studies presented, we conclude that there is preliminary evidence to support that (a) environmental factors, such as diet, neurotoxic exposures and stress, influence offspring DNAm, and that (b) variability in DNAm, in turn, is associated with child and adolescent psychopathology. Overall, very few studies have examined DNAm in relation to both exposures and outcomes, and almost all analyses have been correlational in nature.

CONCLUSIONS

DNAm holds potential as a biomarker indexing both environmental risk exposure and vulnerability for child psychopathology. However, the extent to which it may represent a causal mediator is not clear. In future, collection of prospective risk exposure, DNAm and outcomes - as well as functional characterisation of epigenetic findings - will assist in determining the role of DNAm in the link between risk exposure and psychopathology.

Associations of monoamine oxidase A gene first exon methylation with sexual abuse and current depression in women

Childhood physical abuse (PA) and sexual abuse (SA) interact with monoamine oxidase A (MAOA) gene polymorphism to modify risk for mental disorders. In addition, PA and SA may alter gene activity through epigenetic mechanisms such as DNA methylation, thereby further modifying risk for disorders. We investigated whether methylation in a region spanning the MAOA first exon and part of the first intron was associated with PA and/or SA, MAOA genotype, alcohol dependence, drug dependence, depression disorders, anxiety disorders, and conduct disorder. 114 Swedish women completed standardized diagnostic interviews and questionnaires to report PA and SA, and provided saliva samples for DNA extraction. DNA was genotyped for MAOA-uVNTR polymorphisms, and methylation of a MAOA region of interest (chrX: 43,515,544–43,515,991) was measured. SA, not PA, was associated with hypermethylation of the MAOA first exon relative to no-abuse, and the association was robust to adjustment for psychoactive medication, alcohol and drug dependence, and current substance use. SA and MAOA-uVNTR genotype, but not their interaction, was associated with MAOA methylation. SA associated with all measured mental disorders. Hypermethylation of MAOA first exon mediated the association of SA with current depression, and both methylation levels and SA independently predicted lifetime depression. Much remains to be learned about the independent effects of SA and MAOA-uVNTR genotypes on methylation of the MAOA first exon.

Advances in Drug Discovery and Development in Geriatric Psychiatry

PURPOSE OF REVIEW

This article reviews recent advances in drug discovery and development for geriatric psychiatry. Drug discovery for disorders of the central nervous system is a long and challenging process, with a high attrition rate from the preclinical stages through to marketing a compound. Developing drugs for geriatric neuropsychiatric conditions presents additional challenges, due to the complexity of the symptoms, comorbid diagnoses, and the variability of the population. Despite there being limited success over the past two decades, a number of new approaches have identified potential targets for preclinical development and ultimately clinical testing.

RECENT FINDINGS

Recent approaches have tried to address specific mechanisms that relate to the disease progression. These approaches include combining a number of ligands into to multi-target compounds, or targeting specific types of cells such as protein kinases or myeloid cells. In addition, the increased use of induced pluripotent stem cell cultures has enabled new compounds to be tested on disease-specific tissues, increasing the success rate of the lead compounds going through the preclinical stages. New pharmacological agents designed with advanced screening techniques and the shift towards systems pharmacology is changing the landscape of drug discovery in geriatric psychiatry. There is potential for these new agents to produce targeted effects in the framework of disorders that have long been untreatable.

Epigenetics, Early Adversity and Child and Adolescent Mental Health

Epigenetic modification, such as DNA methylation (DNAm), is a mechanism that can help explain how early adversities can engender long-term vulnerability for mental health problems. At present, there is preliminary evidence to support the possibility of epigenetic mediation: environmental factors are reported to influence offspring DNAm, which in turn associate with child and adolescent psychopathology. However, all analyses have been correlational in nature and, as these studies have focussed on children and adolescents, DNAm has been based on peripheral tissue (cord blood, whole blood, buccal cells). Therefore, the extent to which DNAm could represent a causal mechanism (e.g., a surrogate of central nervous system function) or a biomarker (i.e., an indicator of the pathological process leading to disease) is unclear. This short report has 2 main components. First, 2 studies are summarized, one a candidate gene study and the other an epigenome-wide association study in which DNAm was reported to (partially) mediate the link between adversity and child development. Second, there is a discussion of (1) the "tissue issue," (2) maximizing the interpretability of candidate gene and epigenome-wide approaches, and (3) the need for examining DNAm as a potential biomarker for mental health. It is argued that advances within these 3 areas will make clearer the role of DNAm in the link between adversity and child and adolescent mental health.

Epigenetic Advances in Behavioral and Brain Sciences have Relevance for Public Policy

Nature and nurture work together to drive development, behavior, and health. Behavioral epigenetics research has uncovered the underlying mechanisms for how this happens. Children's early years in development may offer the greatest opportunity for environmental and experiential factors to influence epigenome (chemical compounds telling our genes what to do), but evidence suggests it is never too late. The policy implications of this research are vast, including relevance for child development, health, and disease intervention and prevention.

Behavioral phenotypes and neurobiological mechanisms in the Shank1 mouse model for autism spectrum disorder: A translational perspective

Autism spectrum disorder (ASD) is a heterogeneous group of neurodevelopmental disorders, characterized by early-onset deficits in social behavior and communication across multiple contexts, together with restricted, repetitive patterns of behavior, interests, or activities. ASD is among the most heritable neuropsychiatric conditions with heritability estimates higher than 80%, and while available evidence points to a complex set of genetic factors, the SHANK (also known as ProSAP) gene family has emerged as one of the most promising candidates. Several genetic Shank mouse models for ASD were generated, including Shank1 knockout mice. Behavioral studies focusing on the Shank1 knockout mouse model for ASD included assays for detecting ASD-relevant behavioral phenotypes in the following domains: (I) social behavior, (II) communication, and (III) repetitive and stereotyped patterns of behavior. In addition, assays for detecting behavioral phenotypes with relevance to comorbidities in ASD were performed, including but not limited to (IV) cognitive functioning. Here, we summarize and discuss behavioral and neuronal findings obtained in the Shank1 knockout mouse model for ASD. We identify open research questions by comparing such findings with the symptoms present in humans diagnosed with ASD and carrying SHANK1 deletions. We conclude by discussing the implications of the behavioral and neuronal phenotypes displayed by the Shank1 knockout mouse model for the development of future pharmacological interventions in ASD.

CDYL suppresses epileptogenesis in mice through repression of axonal Nav1.6 sodium channel expression

Impairment of intrinsic plasticity is involved in a range of neurological disorders such as epilepsy. However, how intrinsic excitability is regulated is still not fully understood. Here we report that the epigenetic factor Chromodomain Y-like (CDYL) protein is a critical regulator of the initiation and maintenance of intrinsic neuroplasticity by regulating voltage-gated ion channels in mouse brains. CDYL binds to a regulatory element in the intron region of SCN8A and mainly recruits H3K27me3 activity for transcriptional repression of the gene. Knockdown of CDYL in hippocampal neurons results in augmented Nav1.6 currents, lower neuronal threshold, and increased seizure susceptibility, whereas transgenic mice over-expressing CDYL exhibit higher neuronal threshold and are less prone to epileptogenesis. Finally, examination of human brain tissues reveals decreased CDYL and increased SCN8A in the temporal lobe epilepsy group. Together, our findings indicate CDYL is a critical player for experience-dependent gene regulation in controlling intrinsic excitability.

Alterations in intrinsic plasticity are important in epilepsy. Here the authors show that the epigenetic factor CDYL regulates the gene expression of the voltage gated sodium channel, Nav1.6, which contributes to seizures in a rat model of epilepsy.

Aberrant cognitive phenotypes and altered hippocampal BDNF expression related to epigenetic modifications in mice lacking the post-synaptic scaffolding protein SHANK1: Implications for autism spectrum disorder

Autism spectrum disorder (ASD) is a class of neurodevelopmental disorders characterized by persistent deficits in social communication/interaction, together with restricted/repetitive patterns of behavior. ASD is among the most heritable neuropsychiatric conditions, and while available evidence points to a complex set of genetic factors, the SHANK gene family has emerged as one of the most promising candidates. Here, we assessed ASD-related phenotypes with particular emphasis on social behavior and cognition in Shank1 mouse mutants in comparison to heterozygous and wildtype littermate controls across development in both sexes. While social approach behavior was evident in all experimental conditions and social recognition was only mildly affected by genotype, Shank1^-/- null mutant mice were severely impaired in object recognition memory. This effect was particularly prominent in juveniles, not due to impairments in object discrimination, and replicated in independent mouse cohorts. At the neurobiological level, object recognition deficits were paralleled by increased brain-derived neurotrophic factor (BDNF) protein expression in the hippocampus of Shank1^-/- mice; yet BDNF levels did not differ under baseline conditions. We therefore investigated changes in the epigenetic regulation of hippocampal BDNF expression and detected an enrichment of histone H3 acetylation at the Bdnf promoter1 in Shank1^-/- mice, consistent with increased learning-associated BDNF. Together, our findings indicate that Shank1 deletions lead to an aberrant cognitive phenotype characterized by severe impairments in object recognition memory and increased hippocampal BDNF levels, possibly due to epigenetic modifications. This result supports the link between ASD and intellectual disability, and suggests epigenetic regulation as a potential therapeutic target.

Epigenetic and transgenerational mechanisms in infection-mediated neurodevelopmental disorders

Prenatal infection is an environmental risk factor for various brain disorders with neurodevelopmental components, including autism spectrum disorder and schizophrenia. Modeling this association in animals shows that maternal immune activation negatively affects fetal brain development and leads to the emergence of behavioral disturbances later in life. Recent discoveries in these preclinical models suggest that epigenetic modifications may be a critical molecular mechanism by which prenatal immune activation can mediate changes in brain development and functions, even across generations. This review discusses the potential epigenetic mechanisms underlying the effects of prenatal infections, thereby highlighting how infection-mediated epigenetic reprogramming may contribute to the transgenerational transmission of pathological traits. The identification of epigenetic and transgenerational mechanisms in infection-mediated neurodevelopmental disorders appears relevant to brain disorders independently of existing diagnostic classifications and may help identifying complex patterns of transgenerational disease transmission beyond genetic inheritance. The consideration of ancestral infectious histories may be of great clinical interest and may be pivotal for developing new preventive treatment strategies against infection-mediated neurodevelopmental disorders.

Genome-wide DNA Methylation Changes in a Mouse Model of Infection-Mediated Neurodevelopmental Disorders

BACKGROUND

Prenatal exposure to infectious or inflammatory insults increases the risk of neurodevelopmental disorders. Using a well-established mouse model of prenatal viral-like immune activation, we examined whether this pathological association involves genome-wide DNA methylation differences at single nucleotide resolution.

METHODS

Prenatal immune activation was induced by maternal treatment with the viral mimetic polyriboinosinic-polyribocytidylic acid in middle or late gestation. Following behavioral and cognitive characterization of the adult offspring (n = 12 per group), unbiased capture array bisulfite sequencing was combined with subsequent matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and quantitative real-time polymerase chain reaction analyses to quantify DNA methylation changes and transcriptional abnormalities in the medial prefrontal cortex of immune-challenged and control offspring. Gene ontology term enrichment analysis was used to explore shared functional pathways of genes with differential DNA methylation.

RESULTS

Adult offspring of immune-challenged mothers displayed hyper- and hypomethylated CpGs at numerous loci and at distinct genomic regions, including genes relevant for gamma-aminobutyric acidergic differentiation and signaling (e.g., Dlx1, Lhx5, Lhx8), Wnt signaling (Wnt3, Wnt8a, Wnt7b), and neural development (e.g., Efnb3, Mid1, Nlgn1, Nrxn2). Altered DNA methylation was associated with transcriptional changes of the corresponding genes. The epigenetic and transcriptional effects were dependent on the offspring's age and were markedly influenced by the precise timing of prenatal immune activation.

CONCLUSIONS

Prenatal viral-like immune activation is capable of inducing stable DNA methylation changes in the medial prefrontal cortex. These long-term epigenetic modifications are a plausible mechanism underlying the disruption of prefrontal gene transcription and behavioral functions in subjects with prenatal infectious histories.

Epigenetics in epilepsy

Approximately 50 million people have epilepsy, making it the most common chronic and severe neurological disease worldwide, with increased risk of mortality and psychological and socioeconomic consequences impairing quality of life. More than 30% of patients with epilepsy have inadequate control of their seizures with drug therapy. Any structural brain lesion can provoke epilepsy. However, progression of seizure activity as well as the development of drug-resistance remains difficult to predict, irrespective of the underlying epileptogenic condition, i.e., traumatic brain injury, developmental brain lesions, brain tumors or genetic inheritance. Mutated DNA sequences in genes encoding for ion channels or neurotransmitter receptors have been identified in hereditary focal or generalized epilepsies, but genotype-phenotype correlations are poor, arguing for additional factors determining the effect of a genetic predisposition. The dynamics of epigenetic mechanisms (e.g. DNA methylation, histone modifications, chromatin remodelling, and non-coding RNAs) provide likely explanations for common features in epilepsy and other complex diseases, including late onset, parent-of-origin effects, discordance of monozygotic twins, and fluctuation of symptoms. In addition, many focal epilepsies, including focal cortical dysplasias (FCDs), glio-neuronal tumors (e.g. ganglioglioma), or temporal lobe epilepsy with hippocampal sclerosis (TLE-HS), do not seem to primarily associate with hereditary traits, suggesting other pathogenic mechanisms. Herein we will discuss the many faces of the epigenetic machinery, which provides powerful tools and mechanisms to propagate epileptogenicity and likely also contribute to the epileptogenic memory in chronic and difficult-to-treat epilepsies.