Genome wide association studies (GWAS) and copy number variation (CNV) studies of the major psychoses: what have we learnt?

PPP3CC gene: a putative modulator of antidepressant response through the B-cell receptor signaling pathway

Antidepressant pharmacogenetics represents a stimulating, but often discouraging field. The present study proposes a combination of several methodologies across three independent samples. Genes belonging to monoamine, neuroplasticity, circadian rhythm and transcription factor pathways were investigated in two samples (n=369 and 88) with diagnosis of major depression who were treated with antidepressants. Phenotypes were response, remission and treatment-resistant depression. Logistic regression including appropriate covariates was performed. Genes associated with outcomes were investigated in the STAR*D (Sequenced Treatment Alternatives to Relieve Depression) genome-wide study (n=1861). Top genes were further studied through a pathway analysis. In both original samples, markers associated with outcomes were concentrated in the PPP3CC gene. Other interesting findings were particularly in the HTR2A gene in one original sample and the STAR*D. The B-cell receptor signaling pathway proved to be the putative mediator of PPP3CC's effect on antidepressant response (P=0.03). Among innovative candidates, PPP3CC, involved in the regulation of immune system and synaptic plasticity, seems promising for further investigation.

Genome-wide association study of bipolar disorder in Canadian and UK populations corroborates disease loci including SYNE1 and CSMD1

BACKGROUND

Recently, genome-wide association studies (GWAS) for cases versus controls using single nucleotide polymorphism microarray data have shown promising findings for complex neuropsychiatric disorders, including bipolar disorder (BD).

METHODS

Here we describe a comprehensive genome-wide study of bipolar disorder (BD), cross-referencing analysis from a family-based study of 229 small families with association analysis from over 950 cases and 950 ethnicity-matched controls from the UK and Canada. Further, loci identified in these analyses were supported by pathways identified through pathway analysis on the samples.

RESULTS

Although no genome-wide significant markers were identified, the combined GWAS findings have pointed to several genes of interest that support GWAS findings for BD from other groups or consortia, such as at SYNE1 on 6q25, PPP2R2C on 4p16.1, ZNF659 on 3p24.3, CNTNAP5 (2q14.3), and CDH13 (16q23.3). This apparent corroboration across multiple sites gives much confidence to the likelihood of genetic involvement in BD at these loci. In particular, our two-stage strategy found association in both our combined case/control analysis and the family-based analysis on 1q21.2 (closest gene: sphingosine-1-phosphate receptor 1 gene, S1PR1) and on 1q24.1 near the gene TMCO1, and at CSMD1 on 8p23.2, supporting several previous GWAS reports for BD and for schizophrenia. Pathway analysis suggests association of pathways involved in calcium signalling, neuropathic pain signalling, CREB signalling in neurons, glutamate receptor signalling and axonal guidance signalling.

CONCLUSIONS

The findings presented here show support for a number of genes previously implicated genes in the etiology of BD, including CSMD1 and SYNE1, as well as evidence for previously unreported genes such as the brain-expressed genes ADCY2, NCALD, WDR60, SCN7A and SPAG16.

How might ZNF804A variants influence risk for schizophrenia and bipolar disorder? A literature review, synthesis, and bioinformatic analysis

The gene that encodes zinc finger protein 804A (ZNF804A) became a candidate risk gene for schizophrenia (SZ) after surpassing genome-wide significance thresholds in replicated genome-wide association scans and meta-analyses. Much remains unknown about this reported gene expression regulator; however, preliminary work has yielded insights into functional and biological effects of ZNF804A by targeting its regulatory activities in vitro and by characterizing allele-specific interactions with its risk-conferring single nucleotide polymorphisms (SNPs). There is now strong epidemiologic evidence for a role of ZNF804A polymorphisms in both SZ and bipolar disorder (BD); however, functional links between implicated variants and susceptible biological states have not been solidified. Here we briefly review the genetic evidence implicating ZNF804A polymorphisms as genetic risk factors for both SZ and BD, and discuss the potential functional consequences of these variants on the regulation of ZNF804A and its downstream targets. Empirical work and predictive bioinformatic analyses of the alternate alleles of the two most strongly implicated ZNF804A polymorphisms suggest they might alter the affinity of the gene sequence for DNA- and/or RNA-binding proteins, which might in turn alter expression levels of the gene or particular ZNF804A isoforms. Future work should focus on clarifying the critical periods and cofactors regulating these genetic influences on ZNF804A expression, as well as the downstream biological consequences of an imbalance in the expression of ZNF804A and its various mRNA isoforms.

Integrative biological analysis for neuropsychopharmacology

Although advances in psychotherapy have been made in recent years, drug discovery for brain diseases such as schizophrenia and mood disorders has stagnated. The need for new biomarkers and validated therapeutic targets in the field of neuropsychopharmacology is widely unmet. The brain is the most complex part of human anatomy from the standpoint of number and types of cells, their interconnections, and circuitry. To better meet patient needs, improved methods to approach brain studies by understanding functional networks that interact with the genome are being developed. The integrated biological approaches--proteomics, transcriptomics, metabolomics, and glycomics--have a strong record in several areas of biomedicine, including neurochemistry and neuro-oncology. Published applications of an integrated approach to projects of neurological, psychiatric, and pharmacological natures are still few but show promise to provide deep biological knowledge derived from cells, animal models, and clinical materials. Future studies that yield insights based on integrated analyses promise to deliver new therapeutic targets and biomarkers for personalized medicine.

Effects of the neurogranin variant rs12807809 on thalamocortical morphology in schizophrenia

Although the genome wide supported psychosis susceptibility neurogranin (NRGN) gene is expressed in human brains, it is unclear how it impacts brain morphology in schizophrenia. We investigated the influence of NRGN rs12807809 on cortical thickness, subcortical volumes and shapes in patients with schizophrenia. One hundred and fifty six subjects (91 patients with schizophrenia and 65 healthy controls) underwent structural MRI scans and their blood samples were genotyped. A brain mapping algorithm, large deformation diffeomorphic metric mapping, was used to perform group analysis of subcortical shapes and cortical thickness. Patients with risk TT genotype were associated with widespread cortical thinning involving frontal, parietal and temporal cortices compared with controls with TT genotype. No volumetric difference in subcortical structures (hippocampus, thalamus, amygdala, basal ganglia) was observed between risk TT genotype in patients and controls. However, patients with risk TT genotype were associated with thalamic shape abnormalities involving regions related to pulvinar and medial dorsal nuclei. Our results revealed the influence of the NRGN gene on thalamocortical morphology in schizophrenia involving widespread cortical thinning and thalamic shape abnormalities. These findings help to clarify underlying NRGN mediated pathophysiological mechanisms involving cortical-subcortical brain networks in schizophrenia.

The "DGPPN-Cohort": A national collaboration initiative by the German Association for Psychiatry and Psychotherapy (DGPPN) for establishing a large-scale cohort of psychiatric patients

The German Association for Psychiatry and Psychotherapy (DGPPN) has committed itself to establish a prospective national cohort of patients with major psychiatric disorders, the so-called DGPPN-Cohort. This project will enable the scientific exploitation of high-quality data and biomaterial from psychiatric patients for research. It will be set up using harmonised data sets and procedures for sample generation and guided by transparent rules for data access and data sharing regarding the central research database. While the main focus lies on biological research, it will be open to all kinds of scientific investigations, including epidemiological, clinical or health-service research.

Comparison of gene expression profiles in the blood, hippocampus and prefrontal cortex of rats

Background

The comparability of gene expression between blood and brain tissues is a central issue in neuropsychiatric research where the analysis of molecular mechanisms in the brain is of high importance for the understanding of the diseases and the discovery of biomarkers. However, the accessibility of brain tissue is limited. Therefore, knowledge about how easily accessible peripheral tissue, e. g. blood, is comparable to and reflects gene expression of brain regions will help to advance neuropsychiatric research.

Description

Gene expression in the blood, hippocampus (HC) and prefrontal cortex (PFC) of genetically identical rats was compared using a genome-wide Affymetrix gene expression microarray covering 29,215 expressed genes. A total of 56.8% of 15,717 expressed genes were co-expressed in blood and at least one brain tissue, while 55.3% of all genes were co-expressed in all three tissues simultaneously. The overlapping genes included a set of genes of relevance to neuropsychiatric diseases, in particular bipolar disorder, schizophrenia and alcohol addiction. These genes included CLOCK, COMT, FAAH, NPY, NR3C1, NRGN, PBRM1, TCF4, and SYNE.

Conclusions

This study provides baseline data on absolute gene expression and differences between gene expression in the blood, HC and PFC brain tissue of genetically identical rats. The present data represents a valuable resource for future studies as it might be used for first information on gene expression levels of genes of interest in blood and brain under baseline conditions. Limitations of our study comprise possible contamination of brain tissue with blood and the non-detection of genes with very low expression levels. Genes that are more highly expressed in the brain than in the blood are of particular interest since changes in their expression, e.g. due to disease status, or treatment, are likely to be detected in an experiment. In contrast, genes with higher expression in the blood than in the brain are less informative since their higher baseline levels could superimpose variation in brain.

New findings in the genetics of schizophrenia

New findings in schizophrenia genetics are based on genome-wide association studies (GWAS), research into DNA copy number variations (CNVs), and endophenotypes. More than 70 genes have recently been suspected to be involved in the genetic background of schizophrenia based on the GWAS´s results. They are typically related to neurodevelopment/neuroplasticity, immunology and neuroendocrinology. Nevertheless, for many detected genes their possible relationship to schizophrenia etiopathogenesis is still unknown. The CNVs at genome loci 1q21.1 (candidate gene e.g., PRKAB2), 2p16.3 (candidate gene e.g., NRXN1), 3q29 (candidate genes e.g., BDH1, DLG1, PAK2 or TFRC), 15q11.2 (candidate gene e.g., CYFIP1), 15q13.3 (candidate gene e.g., CHRNA7), 16p13.1 (candidate genes e.g.,NTAN1 or NDE1) and 22q11.2 (candidate genes e.g., COMT, GSTT2 or PRODH) were associated with schizophrenia most frequently. Genetic research of schizophrenia endophenotypes, usually neurophysiological, neuromotoric, neurocognitive, neuroanatomical, neurological or personality-related, will help us to discover the role of relevant genes in the pathogenesis of schizophrenia. It is also necessary to integrate knowledge from other research platforms in schizophrenia, like epigenetics, studies of gene-environment interactions, transcriptomics, proteomics, metabolomics, neuroimaging and psychopathology. A better knowledge of the genetic background of schizophrenia can lead to changes in the treatment, prevention and genetic counselling. It may also reduce stigma in this severe mental disorder.

Neurodevelopment in schizophrenia: the role of the wnt pathways

OBJECTIVES

To review the role of Wnt pathways in the neurodevelopment of schizophrenia.

METHODS

SYSTEMATIC PUBMED SEARCH, USING AS KEYWORDS ALL THE TERMS RELATED TO THE WNT PATHWAYS AND CROSSING THEM WITH EACH OF THE FOLLOWING AREAS: normal neurodevelopment and physiology, neurodevelopmental theory of schizophrenia, schizophrenia, and antipsychotic drug action.

RESULTS

Neurodevelopmental, behavioural, genetic, and psychopharmacological data point to the possible involvement of Wnt systems, especially the canonical pathway, in the pathophysiology of schizophrenia and in the mechanism of antipsychotic drug action. The molecules most consistently found to be associated with abnormalities or in antipsychotic drug action are Akt1, glycogen synthase kinase3beta, and beta-catenin. However, the extent to which they contribute to the pathophysiology of schizophrenia or to antipsychotic action remains to be established.

CONCLUSIONS

The study of the involvement of Wnt pathway abnormalities in schizophrenia may help in understanding this multifaceted clinical entity; the development of Wnt-related pharmacological targets must await the collection of more data.

Parental age and risk of bipolar disorder in offspring

We investigated prospectively documented parental age and bipolar disorder (BD) in a multi-ethnic birth cohort. The study was based on a nested case-control design from the Child Health and Development Study (CHDS) birth cohort from 1959 to 1966. Potential cases with BD were ascertained by database linkages between CHDS, Kaiser Permanente Medical Care Plan (KPNC), and Alameda County Behavioral Health Care Services, and mailed questionnaires. Consensus diagnoses with the SCID for DSM-IV-TR were made. The total number of BD cases was 94. Controls (N=746) were selected from the birth cohort and matched on date of birth, sex, and KPNC membership or residence in Alameda County. For every 10-year increment of paternal age, there was no significant association with BD, adjusting for maternal age. There was also no significant association between maternal age, modeled in 10-year increments, and risk of BD after adjustment for paternal age and maternal race, although there was a suggestion for a protective relationship between increasing maternal age and BD with psychotic features. These findings suggest that if advanced paternal age is a risk factor for BD, the strength of the relationship is small.

Automated design of paralogue ratio test assays for the accurate and rapid typing of copy number variation

Motivation: Genomic copy number variation (CNV) can influence susceptibility to common diseases. High-throughput measurement of gene copy number on large numbers of samples is a challenging, yet critical, stage in confirming observations from sequencing or array Comparative Genome Hybridization (CGH). The paralogue ratio test (PRT) is a simple, cost-effective method of accurately determining copy number by quantifying the amplification ratio between a target and reference amplicon. PRT has been successfully applied to several studies analyzing common CNV. However, its use has not been widespread because of difficulties in assay design.

Results: We present PRTPrimer (www.prtprimer.org) software for automated PRT assay design. In addition to stand-alone software, the web site includes a database of pre-designed assays for the human genome at an average spacing of 6 kb and a web interface for custom assay design. Other reference genomes can also be analyzed through local installation of the software. The usefulness of PRTPrimer was tested within known CNV, and showed reproducible quantification. This software and database provide assays that can rapidly genotype CNV, cost-effectively, on a large number of samples and will enable the widespread adoption of PRT.

Availability: PRTPrimer is available in two forms: a Perl script (version 5.14 and higher) that can be run from the command line on Linux systems and as a service on the PRTPrimer web site (www.prtprimer.org).

Contact:cjt14@le.ac.uk

Supplementary Information:Supplementary data are available at Bioinformatics online.

Increased density of AKAP5-expressing neurons in the anterior cingulate cortex of subjects with bipolar disorder

Brain anatomical abnormalities as well as cognitive and emotional processing deficits have been reported for the prefrontal cortex in bipolar disorder, which are in part attributable to cellular and laminar abnormalities in postsynaptic protein expression. A kinase anchoring protein (AKAP) 5/79 plays a key role in postsynaptic signalling of excitatory synapses. We aimed to reveal if the cellular expression of AKAP5/79 protein is altered in the anterior cingulate cortex and the dorsolateral prefrontal cortex in bipolar disorder. Ten subjects with bipolar disorder and ten control cases were investigated by use of immunohistochemical and morphometric techniques. Compared with controls in subjects with bipolar disorder, the numerical density of AKAP5-expressing neurons was significantly increased in the left (p = 0.002) and right (p = 0.008) anterior cingulate cortex. Layer-specific counting revealed that left side layers II (p = 0.000), III (p = 0.001) and V (p = 0.005) as well as right side layers III (p = 0.007), IV (p = 0.007) and V (p = 0.004) had significantly increased AKAP5-positive cell densities in bipolar disorder. In contrast, no statistically significant differences were found for the dorsolateral prefrontal cortex. However, we observed a more intense intraneuronal immunostaining in both prefrontal areas in bipolar disorder patients. Elevated cell numbers and increased intracellular expression of AKAP, together with the altered expression patterns of most intracellular interaction partners of this protein in bipolar disorder as known from the literature, might point to disease-related abnormalities of the AKAP-associated signalosome in prefrontal cortex neurons.

Myosin Vb gene is associated with schizophrenia in Chinese Han population

Myosin Vb (MYO5B) has recently been implicated in the etiology of bipolar disorder in a genome-wide association study (GWAS). This gene is involved in amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunit glutamate receptor 1 (GluR1) recycling and plays an important role in the primary excitatory neurotransmission. Dysfunction of the brain glutamate system has been postulated to be involved in the pathophysiology in schizophrenia. To further investigate the association between MYO5B polymorphisms and schizophrenia, we genotyped nine single nucleotide polymorphisms (SNPs) in an independent sample of 1463 individuals with schizophrenia and 1563 healthy control subjects, and detected three SNPs and two haplotype blocks which displayed significant association with schizophrenia. This association was further strengthened by the results of meta-analysis. Our data strongly supported that the MYO5B gene might be associated with schizophrenia in the Chinese Han population and they have implications for understanding the glutamate hypothesis of schizophrenia.

Informing DSM-5: biological boundaries between bipolar I disorder, schizoaffective disorder, and schizophrenia

BACKGROUND

The fifth version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) opted to retain existing diagnostic boundaries between bipolar I disorder, schizoaffective disorder, and schizophrenia. The debate preceding this decision focused on understanding the biologic basis of these major mental illnesses. Evidence from genetics, neuroscience, and pharmacotherapeutics informed the DSM-5 development process. The following discussion will emphasize some of the key factors at the forefront of the debate.

DISCUSSION

Family studies suggest a clear genetic link between bipolar I disorder, schizoaffective disorder, and schizophrenia. However, large-scale genome-wide association studies have not been successful in identifying susceptibility genes that make substantial etiological contributions. Boundaries between psychotic disorders are not further clarified by looking at brain morphology. The fact that symptoms of bipolar I disorder, but not schizophrenia, are often responsive to medications such as lithium and other anticonvulsants must be interpreted within a larger framework of biological research.

SUMMARY

For DSM-5, existing nosological boundaries between bipolar I disorder and schizophrenia were retained and schizoaffective disorder preserved as an independent diagnosis since the biological data are not yet compelling enough to justify a move to a more neurodevelopmentally continuous model of psychosis.

Opportunities for bioinformatics in the classification of behavior and psychiatric disorders

A bioinformatics approach to behavioral neuroscience provides both unique opportunities and challenges for research on behavior. A major challenge has been to describe, define, and discriminate among abstract behavioral processes, in large part by distinguishing among the biological mechanisms of unique but not entirely discrete, entities of behavior. Understanding the complexity of neurobiology and behavior requires integration of data across diverse biological systems, types of data, and levels of scale. With the perspective and application of bioinformatics, we can uncover the relationships among these systems and take steps forward in realizing the common and distinct bases of psychiatric disease.

Major channels involved in neuropsychiatric disorders and therapeutic perspectives

Voltage-gated ion channels are important mediators of physiological functions in the central nervous system. The cyclic activation of these channels influences neurotransmitter release, neuron excitability, gene transcription, and plasticity, providing distinct brain areas with unique physiological and pharmacological response. A growing body of data has implicated ion channels in the susceptibility or pathogenesis of psychiatric diseases. Indeed, population studies support the association of polymorphisms in calcium and potassium channels with the genetic risk for bipolar disorders (BPDs) or schizophrenia. Moreover, point mutations in calcium, sodium, and potassium channel genes have been identified in some childhood developmental disorders. Finally, antibodies against potassium channel complexes occur in a series of autoimmune psychiatric diseases. Here we report recent studies assessing the role of calcium, sodium, and potassium channels in BPD, schizophrenia, and autism spectrum disorders, and briefly summarize promising pharmacological strategies targeted on ion channels for the therapy of mental illness and related genetic tests.

How Nox2-containing NADPH oxidase affects cortical circuits in the NMDA receptor antagonist model of schizophrenia

SIGNIFICANCE

Schizophrenia is a complex neuropsychiatric disorder affecting around 1% of the population worldwide. Its mode of inheritance suggests a multigenic neurodevelopmental disorder with symptoms appearing during late adolescence/early adulthood, with its onset strongly influenced by environmental stimuli. Many neurotransmitter systems, including dopamine, glutamate, and gamma-aminobutyric acid, show alterations in affected individuals, and the behavioral and physiological characteristics of the disease can be mimicked by drugs that produce blockade of N-methyl-d-aspartate glutamate receptors (NMDARs).

RECENT ADVANCES

Mounting evidence suggests that drugs that block NMDARs specifically impair the inhibitory capacity of parvalbumin-expressing (PV+) fast-spiking neurons in adult and developing rodents, and alterations in these inhibitory neurons is one of the most consistent findings in the schizophrenic postmortem brain. Disruption of the inhibitory capacity of PV+ inhibitory neurons will alter the functional balance between excitation and inhibition in prefrontal cortical circuits producing impairment of working memory processes such as those observed in schizophrenia.

CRITICAL ISSUES

Mechanistically, the effect of NMDAR antagonists can be attributed to the activation of the Nox2-dependent reduced form of nicotinamide adenine dinucleotide phosphate oxidase pathway in cortical neurons, which is consistent with the emerging role of oxidative stress in the pathogenesis of mental disorders, specifically schizophrenia. Here we review the mechanisms by which NMDAR antagonists produce lasting impairment of the cortical PV+ neuronal system and the roles played by Nox2-dependent oxidative stress mechanisms.

FUTURE DIRECTIONS

The discovery of the pathways by which oxidative stress leads to unbalanced excitation and inhibition in cortical neural circuits opens a new perspective toward understanding the biological underpinnings of schizophrenia.

The ANK3 bipolar disorder gene regulates psychiatric-related behaviors that are modulated by lithium and stress

BACKGROUND

Ankyrin 3 (ANK3) has been strongly implicated as a risk gene for bipolar disorder (BD) by recent genome-wide association studies of patient populations. However, the genetic variants of ANK3 contributing to BD risk and their pathological function are unknown.

METHODS

To gain insight into the potential disease relevance of ANK3, we examined the function of mouse Ank3 in the regulation of psychiatric-related behaviors using genetic, neurobiological, pharmacological, and gene-environment interaction (G×E) approaches. Ank3 expression was reduced in mouse brain either by viral-mediated RNA interference or through disruption of brain-specific Ank3 in a heterozygous knockout mouse.

RESULTS

RNA interference of Ank3 in hippocampus dentate gyrus induced a highly specific and consistent phenotype marked by decreased anxiety-related behaviors and increased activity during the light phase, which were attenuated by chronic treatment with the mood stabilizer lithium. Similar behavioral alterations of reduced anxiety and increased motivation for reward were also exhibited by Ank3+/- heterozygous mice compared with wild-type Ank3+/+ mice. Remarkably, the behavioral traits of Ank3+/- mice transitioned to depression-related features after chronic stress, a trigger of mood episodes in BD. Ank3+/- mice also exhibited elevated serum corticosterone, suggesting that reduced Ank3 expression is associated with elevated stress reactivity.

CONCLUSIONS

This study defines a new role for Ank3 in the regulation of psychiatric-related behaviors and stress reactivity that lends support for its involvement in BD and establishes a general framework for determining the disease relevance of genes implicated by patient genome-wide association studies.

Association of rs1006737 in CACNA1C with alterations in prefrontal activation and fronto-hippocampal connectivity

BACKGROUND

Genome-wide association studies have identified the rs1006737 single nucleotide polymorphism (SNP) in the CACNA1C gene as a susceptibility locus for schizophrenia and bipolar disorder. On the neural systems level this association is explained by altered functioning of the dorsolateral prefrontal cortex (DLPFC) and the hippocampal formation (HF), brain regions also affected by mental illness. In the present study we investigated the association of rs1006737 genotype with prefrontal activation and fronto-hippocampal connectivity.

METHODS

We used functional magnetic resonance imaging to measure neural activation during an n-back working memory task in 94 healthy subjects. All subjects were genotyped for the SNP rs1006737. We tested associations of the rs1006737 genotype with changes in working-memory-related DLPFC activation and functional integration using a seed region functional connectivity approach.

RESULTS

Rs1006737 genotype was associated with altered right-hemispheric DLPFC activation. The homozygous A (risk) group showed decreased activation compared to G-allele carriers. Further, the functional connectivity analysis revealed a positive association of fronto-hippocampal connectivity with rs1006737 A alleles.

CONCLUSIONS

We did not replicate the previous findings of increased right DLPFC activation in CACNA1C rs1006737 A homozygotes. In fact, we found the opposite effect, thus questioning prefrontal inefficiency as rs1006737 genotype-related intermediate phenotype. On the other hand, our results indicate that alterations in the functional coupling between the prefrontal cortex and the medial temporal lobe could represent a neural system phenotype that is mediated by CACNA1C rs1006737 and other genetic susceptibility loci for schizophrenia and bipolar disorder.

Neurocognitive Functioning in Schizophrenia and Bipolar Disorder: Clarifying Concepts of Diagnostic Dichotomy vs. Continuum

The Kraepelinian dichotomy posits that patients with schizophrenia (SCZ) and bipolar disorder (BD) present as two separate psychotic entities such that they differ in terms of clinical severity including neurocognitive functioning. Our study aimed to specifically compare and contrast the level of neurocognitive functioning between SCZ and BD patients and identify predictors of their poor neurocognitive functioning. We hypothesized that patients with SCZ had a similar level of neurocognitive impairment compared with BD. About 49 healthy controls (HC), 72 SCZ, and 42 BD patients who were matched for age, gender, and premorbid IQ were administered the Brief Assessment of Cognition battery (BAC). Severity of psychopathology and socio-occupational functioning were assessed for both patients groups. Both BD and SCZ groups demonstrated similar patterns of neurocognitive deficits across several domains (verbal memory, working memory, semantic fluency, processing speed) compared with HC subjects. However, no significant difference was found in neurocognitive functioning between BD and SCZ patients, suggesting that both patient groups suffer the same degree of neurocognitive impairment. Patients with lower level of psychosocial functioning [F (1,112) = 2.661, p = 0.009] and older age [F (1,112) = -2.625, p = 0.010], not diagnosis or doses of psychotropic medications, predicted poorer overall neurocognitive functioning as measured by the lower BAC composite score. Our findings of comparable neurocognitive impairments between SCZ and BD affirm our hypothesis and support less the Kraepelinian concept of dichotomy but more of a continuum of psychotic spectrum conditions. This should urge clinicians to investigate further the underlying neural basis of these neurocognitive deficits, and be attentive to the associated socio-demographic and clinical profile in order to recognize and optimize early the management of the widespread neurocognitive deficits in patients with SCZ and BD.

Personalized medicine in psychiatry: new technologies and approaches

Psychiatric patients tend to exhibit significant interindividual variability in their responses to psychoactive drugs, as well as an irregular clinical course. For these (and other) reasons, increasing numbers of psychiatrists are turning to genotyping for help in selecting the psychopharmacologic agents best suited to an individual patient's distinctive metabolic characteristics and clinical presentation. Fortunately, routine genotyping is already available for gene variations that code for proteins involved in neurotransmission, and for drug-metabolizing enzymes involved in the elimination of many medications. Thus, genotyping-based personalized psychiatry is now in sight. Increasing numbers of clinically useful DNA microarrays are in the development stage, including a simplified procedure for genotyping patients for CYP2D6, which metabolizes a high proportion of the currently prescribed antidepressants and antipsychotics. It has been pointed out that psychiatric disease is rarely a consequence of an abnormality in a single gene, but reflects the perturbations of complex intracellular networks in the brain. Thus, analysis of functional neuronal networks is becoming an essential component of drug development strategies. The integrated use of technologies such as electroencephalography, magnetoencephalography, functional magnetic resonance imaging (fMRI), and diffusion tensor imaging (DTI), in combination with pharmacogenetics, promises to transform our understanding of the mechanisms of psychiatric disorders and their treatment. The concept of network medicine envisions a time to come when drugs will be used to target a neural network rather than simply components within the network. Personalized medicine in psychiatry is still at an early stage, but it has a very promising future.

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

Neurodevelopmental disorders (NDDs) are characterized by aberrant and delayed early-life development of the brain, leading to deficits in language, cognition, motor behaviour and other functional domains, often accompanied by somatic symptoms. Environmental factors like perinatal infection, malnutrition and trauma can increase the risk of the heterogeneous, multifactorial and polygenic disorders, autism and schizophrenia. Conversely, discrete genetic anomalies are involved in Down, Rett and Fragile X syndromes, tuberous sclerosis and neurofibromatosis, the less familiar Phelan-McDermid, Sotos, Kleefstra, Coffin-Lowry and "ATRX" syndromes, and the disorders of imprinting, Angelman and Prader-Willi syndromes. NDDs have been termed "synaptopathies" in reference to structural and functional disturbance of synaptic plasticity, several involve abnormal Ras-Kinase signalling ("rasopathies"), and many are characterized by disrupted cerebral connectivity and an imbalance between excitatory and inhibitory transmission. However, at a different level of integration, NDDs are accompanied by aberrant "epigenetic" regulation of processes critical for normal and orderly development of the brain. Epigenetics refers to potentially-heritable (by mitosis and/or meiosis) mechanisms controlling gene expression without changes in DNA sequence. In certain NDDs, prototypical epigenetic processes of DNA methylation and covalent histone marking are impacted. Conversely, others involve anomalies in chromatin-modelling, mRNA splicing/editing, mRNA translation, ribosome biogenesis and/or the regulatory actions of small nucleolar RNAs and micro-RNAs. Since epigenetic mechanisms are modifiable, this raises the hope of novel therapy, though questions remain concerning efficacy and safety. The above issues are critically surveyed in this review, which advocates a broad-based epigenetic framework for understanding and ultimately treating a diverse assemblage of NDDs ("epigenopathies") lying at the interface of genetic, developmental and environmental processes. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Molecular characteristics of Human Endogenous Retrovirus type-W in schizophrenia and bipolar disorder

Epidemiological and genome-wide association studies of severe psychiatric disorders such as schizophrenia (SZ) and bipolar disorder (BD), suggest complex interactions between multiple genetic elements and environmental factors. The involvement of genetic elements such as Human Endogenous Retroviruses type 'W' family (HERV-W) has consistently been associated with SZ. HERV-W envelope gene (env) is activated by environmental factors and encodes a protein displaying inflammation and neurotoxicity. The present study addressed the molecular characteristics of HERV-W env in SZ and BD. Hundred and thirty-six patients, 91 with BD, 45 with SZ and 73 healthy controls (HC) were included. HERV-W env transcription was found to be elevated in BD (P<10-4) and in SZ (P=0.012) as compared with HC, but with higher values in BD than in SZ group (P<0.01). The corresponding DNA copy number was paradoxically lower in the genome of patients with BD (P=0.0016) or SZ (P<0.0003) than in HC. Differences in nucleotide sequence of HERV-W env were found between patients with SZ and BD as compared with HC, as well as between SZ and BD. The molecular characteristics of HERV-W env also differ from what was observed in Multiple Sclerosis (MS) and may represent distinct features of the genome of patients with BD and SZ. The seroprevalence for Toxoplasma gondii yielded low but significant association with HERV-W transcriptional level in a subgroup of BD and SZ, suggesting a potential role in particular patients. A global hypothesis of mechanisms inducing such major psychoses is discussed, placing HERV-W at the crossroads between environmental, genetic and immunological factors. Thus, particular infections would act as activators of HERV-W elements in earliest life, resulting in the production of an HERV-W envelope protein, which then stimulates pro-inflammatory and neurotoxic cascades. This hypothesis needs to be further explored as it may yield major changes in our understanding and treatment of severe psychotic disorders.

Ankyrin 3: genetic association with bipolar disorder and relevance to disease pathophysiology

Bipolar disorder (BD) is a multi-factorial disorder caused by genetic and environmental influences. It has a large genetic component, with heritability estimated between 59-93%. Recent genome-wide association studies (GWAS) using large BD patient populations have identified a number of genes with strong statistical evidence for association with susceptibility for BD. Among the most significant and replicated genes is ankyrin 3 (ANK3), a large gene that encodes multiple isoforms of the ankyrin G protein. This article reviews the current evidence for genetic association of ANK3 with BD, followed by a comprehensive overview of the known biology of the ankyrin G protein, focusing on its neural functions and their potential relevance to BD. Ankyrin G is a scaffold protein that is known to have many essential functions in the brain, although the mechanism by which it contributes to BD is unknown. These functions include organizational roles for subcellular domains in neurons including the axon initial segment and nodes of Ranvier, through which ankyrin G orchestrates the localization of key ion channels and GABAergic presynaptic terminals, as well as creating a diffusion barrier that limits transport into the axon and helps define axo-dendritic polarity. Ankyrin G is postulated to have similar structural and organizational roles at synaptic terminals. Finally, ankyrin G is implicated in both neurogenesis and neuroprotection. ANK3 and other BD risk genes participate in some of the same biological pathways and neural processes that highlight several mechanisms by which they may contribute to BD pathophysiology. Biological investigation in cellular and animal model systems will be critical for elucidating the mechanism through which ANK3 confers risk of BD. This knowledge is expected to lead to a better understanding of the brain abnormalities contributing to BD symptoms, and to potentially identify new targets for treatment and intervention approaches.

White matter pathology--an endophenotype for bipolar disorder?

BACKGROUND

Neuroimaging investigations of white matter abnormalities in subjects at genetic risk for bipolar disorders (BD) potentially predating the onset of BD offer several advantages. They are not confounded by the presence of illness duration or previous treatment with medication and may ultimately inform evaluation of risk for subsequent development of BD and subsequent therapeutic intervention.

DISCUSSION

Although a number of imaging studies in subjects at genetic risk for BD are available the results are conflicting and no reliable structural markers of genetic liability to bipolar disorders have been proposed. We debate that white matter pathology may be central to the genetic risk to develop BD. Thus, white matter abnormalities detectable in HR subjects but not in controls may reflect genetically driven trait markers. Similar abnormalities may be also evident both in the HR and in BD, suggesting the possibility of genetic risk factors shared by both groups. Conversely, white matter alterations observed in BD patients but not in HR and controls can be interpreted as state markers.

SUMMARY

We suggest that white matter alterations may represent endophenotypes and neurobiological markers intermediate between the underlying susceptibility genes and the clinical expression of BD.

Genome-wide association study in a Swedish population yields support for greater CNV and MHC involvement in schizophrenia compared with bipolar disorder

Schizophrenia (SCZ) and bipolar disorder (BD) are highly heritable psychiatric disorders with overlapping susceptibility loci and symptomatology. We conducted a genome-wide association study (GWAS) of these disorders in a large Swedish sample. We report a new and independent case-control analysis of 1507 SCZ cases, 836 BD cases and 2093 controls. No single-nucleotide polymorphisms (SNPs) achieved significance in these new samples; however, combining new and previously reported SCZ samples (2111 SCZ and 2535 controls) revealed a genome-wide significant association in the major histocompatibility complex (MHC) region (rs886424, P=4.54 × 10(-8)). Imputation using multiple reference panels and meta-analysis with the Psychiatric Genomics Consortium SCZ results underscored the broad, significant association in the MHC region in the full SCZ sample. We evaluated the role of copy number variants (CNVs) in these subjects. As in prior reports, deletions were enriched in SCZ, but not BD cases compared with controls. Singleton deletions were more frequent in both case groups compared with controls (SCZ: P=0.003, BD: P=0.013), whereas the largest CNVs (>500 kb) were significantly enriched only in SCZ cases (P=0.0035). Two CNVs with previously reported SCZ associations were also overrepresented in this SCZ sample: 16p11.2 duplications (P=0.0035) and 22q11 deletions (P=0.03). These results reinforce prior reports of significant MHC and CNV associations in SCZ, but not BD.

Neural stem cells: mechanisms and modeling

In the adult brain, neural stem cells have been found in two major niches: the dentate gyrus and the subventricular zone [corrected]. Neurons derived from these stem cells contribute to learning, memory, and the autonomous repair of the brain under pathological conditions. Hence, the physiology of adult neural stem cells has become a significant component of research on synaptic plasticity and neuronal disorders. In addition, the recently developed induced pluripotent stem cell technique provides a powerful tool for researchers engaged in the pathological and pharmacological study of neuronal disorders. In this review, we briefly summarize the research progress in neural stem cells in the adult brain and in the neuropathological application of the induced pluripotent stem cell technique.

Genome-wide association studies of schizophrenia: does bigger lead to better results?

PURPOSE OF REVIEW

Numerous genome-wide association studies (GWAS) of schizophrenia have been published in the past 6 years, with a number of key reports published in the last year. The studies have evolved in scale from small individual samples to large collaborative endeavors. This review aims to critically assess whether the results have improved as the sample size and scale of genetic association studies have grown.

RECENT FINDINGS

Genomic genotyping and increasing sample sizes for schizophrenia association studies have led to parallel increases in the number of risk genes discovered with high statistical confidence. Nearly 20 genes or loci have surpassed the genome-wide significance threshold (P = 5 × 10) in a single study, and several have been replicated in more than one GWAS.

SUMMARY

Identifying the genetic underpinnings of complex diseases offers insight into the etiological mechanisms leading to manifestation of the disease. New and more effective treatments for schizophrenia are desperately needed, and the ability to target the relevant biological processes grows with our understanding of the genes involved. As the size of GWAS samples has increased, more genes have been identified with high confidence that have begun to provide insight into the etiological and pathophysiological foundations of this disorder.