Antipsychotic subtypes can be characterized by differences in their ability to modify GABAergic promoter methylation

Risperidone response in patients with schizophrenia drives DNA methylation changes in immune and neuronal systems

Background: The choice of efficient antipsychotic therapy for schizophrenia relies on a time-consuming trial-and-error approach, whereas the social and economic burdens of the disease call for faster alternatives. Material & methods: In a search for predictive biomarkers of antipsychotic response, blood methylomes of 28 patients were analyzed before and 4 weeks into risperidone therapy. Results: Several CpGs exhibiting response-specific temporal dynamics were identified in otherwise temporally stable methylomes and noticeable global response-related differences were observed between good and bad responders. These were associated with genes involved in immunity, neurotransmission and neuronal development. Polymorphisms in many of these genes were previously linked with schizophrenia etiology and antipsychotic response. Conclusion: Antipsychotic response seems to be shaped by both stable and medication-induced methylation differences.

Molecular windows into the human brain for psychiatric disorders

Delineating the pathophysiology of psychiatric disorders has been extremely challenging but technological advances in recent decades have facilitated a deeper interrogation of molecular processes in the human brain. Initial candidate gene expression studies of the postmortem brain have evolved into genome wide profiling of the transcriptome and the epigenome, a critical regulator of gene expression. Here, we review the potential and challenges of direct molecular characterization of the postmortem human brain, and provide a brief overview of recent transcriptional and epigenetic studies with respect to neuropsychiatric disorders. Such information can now be leveraged and integrated with the growing number of genome-wide association databases to provide a functional context of trait-associated genetic variants linked to psychiatric illnesses and related phenotypes. While it is clear that the field is still developing and challenges remain to be surmounted, these recent advances nevertheless hold tremendous promise for delineating the neurobiological underpinnings of mental diseases and accelerating the development of novel medication strategies.

Schizophrenia: A review of potential biomarkers

OBJECTIVES

Understanding the biological process and progression of schizophrenia is the first step to developing novel approaches and new interventions. Research on new biomarkers is extremely important when the goal is an early diagnosis (prediction) and precise theranostics. The objective of this review is to understand the research on biomarkers and their effects in schizophrenia to synthesize the role of these new advances.

METHODS

In this review, we search and review publications in databases in accordance with established limits and specific objectives. We look at particular endpoints such as the category of biomarkers, laboratory techniques and the results/conclusions of the selected publications.

RESULTS

The investigation of biomarkers and their potential as a predictor, diagnosis instrument and therapeutic orientation, requires an appropriate methodological strategy. In this review, we found different laboratory techniques to identify biomarkers and their function in schizophrenia.

CONCLUSION

The consolidation of this information will provide a large-scale application network of schizophrenia biomarkers.

DNA methylation signatures of mood stabilizers and antipsychotics in bipolar disorder

Aim: In view of the potential effects of psychiatric drugs on DNA methylation, we investigated whether medication use in bipolar disorder is associated with DNA methylation signatures. Experimental procedures: Blood-based DNA methylation patterns of six frequently used psychotropic drugs (lithium, quetiapine, olanzapine, lamotrigine, carbamazepine, and valproic acid) were examined in 172 bipolar disorder patients. After adjustment for cell type composition, we investigated gene networks, principal components, hypothesis-driven genes and epigenome-wide individual loci. Results: Valproic acid and quetiapine were significantly associated with altered methylation signatures after adjustment for drug-related changes on celltype composition. Conclusion: Psychiatric drugs influence DNA methylation patterns over and above cell type composition in bipolar disorder. Drug-related changes in DNA methylation are therefore not only an important confounder in psychiatric epigenetics but may also inform on the biological mechanisms underlying drug efficacy.

Epigenetic Basis of Mental Illness

Psychiatric disorders are complex multifactorial illnesses involving chronic alterations in neural circuit structure and function as well as likely abnormalities in glial cells. While genetic factors are important in the etiology of most mental disorders, the relatively high rates of discordance among identical twins, particularly for depression and other stress-related syndromes, clearly indicate the importance of additional mechanisms. Environmental factors such as stress are known to play a role in the onset of these illnesses. Exposure to such environmental insults induces stable changes in gene expression, neural circuit function, and ultimately behavior, and these maladaptations appear distinct between developmental versus adult exposures. Increasing evidence indicates that these sustained abnormalities are maintained by epigenetic modifications in specific brain regions. Indeed, transcriptional dysregulation and the aberrant epigenetic regulation that underlies this dysregulation is a unifying theme in psychiatric disorders. Here, we provide a progress report of epigenetic studies of the three major psychiatric syndromes, depression, schizophrenia, and bipolar disorder. We review the literature derived from animal models of these disorders as well as from studies of postmortem brain tissue from human patients. While epigenetic studies of mental illness remain at early stages, understanding how environmental factors recruit the epigenetic machinery within specific brain regions to cause lasting changes in disease susceptibility and pathophysiology is revealing new insight into the etiology and treatment of these conditions.

DNA methylation in psychosis: insights into etiology and treatment

Evidence for involvement of DNA methylation in psychosis forms the focus of this perspective. Of interest are results from two independent sets of experiments including rats treated with antipsychotic drugs and monozygotic twins discordant for schizophrenia. The results show that DNA methylation is increased in rats treated with antipsychotic drugs, reflecting the global effect of the drugs. Some of these changes are also seen in affected schizophrenic twins that were treated with antipsychotics. The genes and pathways identified in the unrelated experiments are relevant to neurodevelopment and psychiatric disorders. The common cause is hypothesized to be aberrations resulting from medication use. However, this needs to be established by future studies that address the origin of methylation changes in psychosis.

How animal models inform child and adolescent psychiatry

OBJECTIVE

Every available approach should be used to advance the field of child and adolescent psychiatry. Biological systems are important for the behavioral problems of children. Close examination of nonhuman animals and the biology and behavior that they share with humans is an approach that must be used to advance the clinical work of child psychiatry.

METHOD

We review here how model systems are used to contribute to significant insights into childhood psychiatric disorders. Model systems have not only demonstrated causality of risk factors for psychiatric pathophysiology, but have also allowed child psychiatrists to think in different ways about risks for psychiatric disorders and multiple levels that might be the basis of recovery and prevention.

RESULTS

We present examples of how animal systems are used to benefit child psychiatry, including through environmental, genetic, and acute biological manipulations. Animal model work has been essential in our current thinking about childhood disorders, including the importance of dose and timing of risk factors, specific features of risk factors that are significant, neurochemistry involved in brain functioning, molecular components of brain development, and the importance of cellular processes previously neglected in psychiatric theories.

CONCLUSION

Animal models have clear advantages and disadvantages that must be considered for these systems to be useful. Coupled with increasingly sophisticated methods for investigating human behavior and biology, animal model systems will continue to make essential contributions to our field.

Genomics and epigenomics in novel schizophrenia drug discovery: translating animal models to clinical research and back

INTRODUCTION

Schizophrenia is a major psychiatric disorder that afflicts about 1% of the world's population, falling into the top 10 medical disorders causing disability. Existing therapeutic strategies have had limited success; they have poor effects on core cognitive impairment and long-term disability. They are also burdened by relevant side effects. Although new antipsychotic medications have been launched in the past decades, there has been a general lack of significant innovation over the past 60 years. This lack of significant progress in the pharmacotherapy of schizophrenia is a reflection of the complexity and heterogeneity of its etiopathogenetic mechanisms.

AREAS COVERED

In this article, the authors briefly review genetic models of schizophrenia, focusing on examples of how new therapeutic strategies have been developed from them. They report on the evidence of epigenetic alterations in schizophrenia and their relevance to pharmacological studies. Further, they describe the implications of epigenetic mechanisms in the etiopathogenesis of the disease and the effects of current antipsychotic drugs on epigenetic processes. Finally, they provide their perspective of using epigenetic drugs for treating schizophrenia.

EXPERT OPINION

Current genetic and epigenetic studies are finally shedding light on the biomolecular mechanisms linked to the core pathogenetic alterations in schizophrenia, rather than just their symptoms. These advancements in the understanding of the physiopathology of schizophrenia provide exciting new perspectives for treatments. Indeed, the possibility of looking directly at the biomolecular level allows us to bypass the age-old issues of animal studies pertaining to their questionable validity as behavioral models.

Identifying novel interventional strategies for psychiatric disorders: integrating genomics, 'enviromics' and gene-environment interactions in valid preclinical models

Psychiatric disorders affect a substantial proportion of the population worldwide. This high prevalence, combined with the chronicity of the disorders and the major social and economic impacts, creates a significant burden. As a result, an important priority is the development of novel and effective interventional strategies for reducing incidence rates and improving outcomes. This review explores the progress that has been made to date in establishing valid animal models of psychiatric disorders, while beginning to unravel the complex factors that may be contributing to the limitations of current methodological approaches. We propose some approaches for optimizing the validity of animal models and developing effective interventions. We use schizophrenia and autism spectrum disorders as examples of disorders for which development of valid preclinical models, and fully effective therapeutics, have proven particularly challenging. However, the conclusions have relevance to various other psychiatric conditions, including depression, anxiety and bipolar disorders. We address the key aspects of construct, face and predictive validity in animal models, incorporating genetic and environmental factors. Our understanding of psychiatric disorders is accelerating exponentially, revealing extraordinary levels of genetic complexity, heterogeneity and pleiotropy. The environmental factors contributing to individual, and multiple, disorders also exhibit breathtaking complexity, requiring systematic analysis to experimentally explore the environmental mediators and modulators which constitute the 'envirome' of each psychiatric disorder. Ultimately, genetic and environmental factors need to be integrated via animal models incorporating the spatiotemporal complexity of gene-environment interactions and experience-dependent plasticity, thus better recapitulating the dynamic nature of brain development, function and dysfunction.

The effects of olanzapine on genome-wide DNA methylation in the hippocampus and cerebellum

Background

The mechanism of action of olanzapine in treating schizophrenia is not clear. This research reports the effects of a therapeutic equivalent treatment of olanzapine on DNA methylation in a rat model in vivo.

Genome-wide DNA methylation was assessed using a MeDIP-chip analysis. All methylated DNA immunoprecipitation (MeDIP), sample labelling, hybridization and processing were performed by Arraystar Inc (Rockville, MD, USA). The identified gene promoters showing significant alterations to DNA methylation were then subjected to Ingenuity Pathway Analysis (Ingenuity System Inc, CA, USA).

Results

The results show that olanzapine causes an increase in methylation in 1,140, 1,294 and 1,313 genes and a decrease in methylation in 633, 565 and 532 genes in the hippocampus, cerebellum and liver, respectively. Most genes affected are tissue specific. Only 41 affected genes (approximately 3%) showed an increase and no gene showed a decrease in methylation in all three tissues. Further, the two brain regions shared 123 affected genes (approximately 10%). The affected genes are enriched in pathways affecting dopamine signalling, molecular transport, nervous system development and functions in the hippocampus; ephrin receptor signalling and synaptic long-term potentiation in the cerebellum; and tissue morphology, cellular assembly and organization in the liver. Also, the affected genes included those previously implicated in psychosis.

Conclusions

The known functions of affected genes suggest that the observed epigenetic changes may underlie the amelioration of symptoms as well as accounting for certain adverse effects including the metabolic syndrome. The results give insights into the mechanism of action of olanzapine, therapeutic effects and the side effects of antipsychotics.

The dynamics of DNA methylation in schizophrenia and related psychiatric disorders

Major psychiatric disorders such as schizophrenia (SZ) and bipolar disorder (BP) with psychosis (BP+) express a complex symptomatology characterized by positive symptoms, negative symptoms, and cognitive impairment. Postmortem studies of human SZ and BP+ brains show considerable alterations in the transcriptome of a variety of cortical structures, including multiple mRNAs that are downregulated in both inhibitory GABAergic and excitatory pyramidal neurons compared with non-psychiatric subjects (NPS). Several reports show increased expression of DNA methyltransferases in telencephalic GABAergic neurons. Accumulating evidence suggests a critical role for altered DNA methylation processes in the pathogenesis of SZ and related psychiatric disorders. The establishment and maintenance of CpG site methylation is essential during central nervous system differentiation and this methylation has been implicated in synaptic plasticity, learning, and memory. Atypical hypermethylation of candidate gene promoters expressed in GABAergic neurons is associated with transcriptional downregulation of the corresponding mRNAs, including glutamic acid decarboxylase 67 (GAD67) and reelin (RELN). Recent reports indicate that the methylation status of promoter proximal CpG dinucleotides is in a dynamic balance between DNA methylation and DNA hydroxymethylation. Hydroxymethylation and subsequent DNA demethylation is more complex and involves additional proteins downstream of 5-hydroxymethylcytosine, including members of the base excision repair (BER) pathway. Recent advances in our understanding of altered CpG methylation, hydroxymethylation, and active DNA demethylation provide a framework for the identification of new targets, which may be exploited for the pharmacological intervention of the psychosis associated with SZ and possibly BP+.

miRNAs as mediators of drug resistance

Chemoresistance of tumors is often reported to be due to overexpression of efflux transporters or genetic alterations of signaling pathways. More recently, there is increasing evidence that epigenetic modification contributes to the phenomenon of drug resistance. Despite alteration of DNA methylation or histone modifications, deregulated miRNA expression patterns of tumor cells have been identified as interfering with drug response. Attempts to modify the expression of selected miRNAs have partly led to intriguing improvements of chemotherapy response. This review focuses on the major epigenetic mechanisms, including the role of miRNA expression contributing to drug resistance and the role of epigenetic drugs to overcome nonresponse arising under conventional chemotherapy.

Advancing drug discovery for schizophrenia

Sponsored by the New York Academy of Sciences and with support from the National Institute of Mental Health, the Life Technologies Foundation, and the Josiah Macy Jr. Foundation, "Advancing Drug Discovery for Schizophrenia" was held March 9-11 at the New York Academy of Sciences in New York City. The meeting, comprising individual talks and panel discussions, highlighted basic, clinical, and translational research approaches, all of which contribute to the overarching goal of enhancing the pharmaceutical armamentarium for treating schizophrenia. This report surveys work by the vanguard of schizophrenia research in such topics as genetic and epigenetic approaches; small molecule therapeutics; and the relationships between target genes, neuronal function, and symptoms of schizophrenia.

A neurochemical basis for an epigenetic vision of psychiatric disorders (1994-2009)

In 1996, Dr. Costa was invited by Prof. Boris Astrachan, Chairman of the Department of Psychiatry at the University of Illinois at Chicago, to direct the research of the "Psychiatric Institute, Department of Psychiatry, School of Medicine, at the University of Illinois at Chicago." He was asked to develop a seminal research program on psychiatric disorders. Viewed in retrospect, Dr. Costa met and surpassed the challenge, as was usual for him. To elucidate the molecular mechanisms whereby nurture (epigenetic factors) and nature (genetic factors) interact to cause major psychiatric disorders was at the center of Dr. Costa's mission for the last 15 years of his research at the Psychiatric Institute. The challenge for Dr. Costa and his colleagues (Auta, Caruncho, Davis, Grayson, Guidotti, Impagnatiello, Kiedrowski, Larson, Manev, Pappas, Pesold, Pinna, Sharma, Smalheiser, Sugaya, Tueting, Veldic [1-111]) had always been to find new ways to prevent and treat psychiatric disorders with pharmacological agents that failed to have major unwanted side effects. In this list, we have quoted the first authors of the papers pertaining to the field of research highlighted in the title. As you know, Dr. Costa was an eclectic scientist and in his 15 years of studies at UIC, he touched many other aspects of neuroscience research that are not discussed in this overview.