COMT: a common susceptibility gene in bipolar disorder and schizophrenia

The interaction between early life complications and a polygenic risk score for schizophrenia is associated with brain activity during emotion processing in healthy participants

BACKGROUND

Previous evidence suggests that early life complications (ELCs) interact with polygenic risk for schizophrenia (SCZ) in increasing risk for the disease. However, no studies have investigated this interaction on neurobiological phenotypes. Among those, anomalous emotion-related brain activity has been reported in SCZ, even if evidence of its link with SCZ-related genetic risk is not solid. Indeed, it is possible this relationship is influenced by non-genetic risk factors. Thus, this study investigated the interaction between SCZ-related polygenic risk and ELCs on emotion-related brain activity.

METHODS

169 healthy participants (HP) in a discovery and 113 HP in a replication sample underwent functional magnetic resonance imaging (fMRI) during emotion processing, were categorized for history of ELCs and genome-wide genotyped. Polygenic risk scores (PRSs) were computed using SCZ-associated variants considering the most recent genome-wide association study. Furthermore, 75 patients with SCZ also underwent fMRI during emotion processing to verify consistency of their brain activity patterns with those associated with risk factors for SCZ in HP.

RESULTS

Results in the discovery and replication samples indicated no effect of PRSs, but an interaction between PRS and ELCs in left ventrolateral prefrontal cortex (VLPFC), where the greater the activity, the greater PRS only in presence of ELCs. Moreover, SCZ had greater VLPFC response than HP.

CONCLUSIONS

These results suggest that emotion-related VLPFC response lies in the path from genetic and non-genetic risk factors to the clinical presentation of SCZ, and may implicate an updated concept of intermediate phenotype considering early non-genetic factors of risk for SCZ.

Logistic ridge regression to predict bipolar disorder using mRNA expression levels in the N-methyl-D-aspartate receptor genes

BACKGROUND

It is hypothesized that demographic variables and mRNA expression levels in the N-methyl-D-aspartate receptor (NMDAR) genes can be employed as potential biomarkers to predict bipolar disorder using artificial intelligence and machine learning approaches.

METHODS

To determine bipolar status, we established a logistic ridge regression model resulting from the analysis of age, gender, and mRNA expression levels in 7 NMDAR genes in the blood of 51 bipolar patients and 139 unrelated healthy individuals in the Taiwanese population. The NMDAR genes encompasses COMT, GCAT, NRG1, PSAT1, SHMT2, SLC1A4, and SRR. We also compared our approach with various state-of-the-art algorithms such as support vector machine and C4.5 decision tree.

RESULTS

The analysis revealed that the mRNA expression levels of COMT, GCAT, NRG1, PSAT1, SHMT2, SLC1A4, and SRR were associated with bipolar disorder. Moreover, the logistic ridge regression model (area under the receiver operating characteristic curve = 0.922) performed maximally among predictive models to infer the complicated relationship between bipolar disorder and biomarkers. Additionally, the results for the age- and gender-matched cohort were similar to those of the unmatched cohort.

LIMITATIONS

The cross-sectional study design limited the predictive value.

CONCLUSION

This is the first study demonstrating that the mRNA expression levels in the NMDAR genes may be altered in patients with bipolar disorder, thereby supporting the NMDAR hypothesis of bipolar disorder. The study also indicates that the mRNA expression levels in the NMDAR genes could serve as potential biomarkers to distinguish bipolar patients from healthy controls using artificial intelligence and machine learning approaches.

Neural anomalies during vigilance in schizophrenia: Diagnostic specificity and genetic associations

Impaired vigilance is a core cognitive deficit in schizophrenia and may serve as an endophenotype (i.e., mark genetic liability). We used a continuous performance task with perceptually degraded stimuli in schizophrenia patients (N = 48), bipolar disorder patients (N = 26), first-degree biological relatives of schizophrenia patients (N = 55) and bipolar disorder patients (N = 28), as well as healthy controls (N = 68) to clarify whether previously reported vigilance deficits and abnormal neural functions were indicative of genetic liability for schizophrenia as opposed to a generalized liability for severe psychopathology. We also examined variation in the Catechol-O-methyltransferase gene to evaluate whether brain responses were related to genetic variation associated with higher-order cognition. Relatives of schizophrenia patients had an increased rate of misidentification of nontarget stimuli as targets when they were perceptually similar, suggestive of difficulties with contour perception. Larger early visual responses (i.e., N1) were associated with better task performance in patients with schizophrenia consistent with enhanced N1 responses reflecting beneficial neural compensation. Additionally, reduced N2 augmentation to target stimuli was specific to schizophrenia. Both patients with schizophrenia and first-degree relatives displayed reduced late cognitive responses (P3b) that predicted worse performance. First-degree relatives of bipolar patients exhibited performance deficits, and displayed aberrant neural responses that were milder than individuals with liability for schizophrenia and dependent on sex. Variation in the Catechol-O-methyltransferase gene was differentially associated with P3b in schizophrenia and bipolar groups. Poor vigilance in schizophrenia is specifically predicted by a failure to enhance early visual responses, weak augmentation of mid-latency brain responses to targets, and limited engagement of late cognitive responses that may be tied to genetic variation associated with prefrontal dopaminergic availability. Experimental results illustrate specific neural functions that distinguish schizophrenia from bipolar disorder and provides evidence for a putative endophenotype that differentiates genetic liability for schizophrenia from severe mental illness more broadly.

Role of the COMT gene Val158Met polymorphism in mental disorders: A review

The Val158Met polymorphism of the COMT gene is functional, easily detectable, and significantly related to metabolism of catecholamines, which underlie pathogenesis of a significant number of mental disorders. Evidence for the role of this polymorphism in schizophrenia, substance dependence, bipolar disorder, obsessive-compulsive disorder, anorexia nervosa and attention deficit hyperactivity disorder is summed up in this review article. The results make it unlikely that the COMT gene plays an important role in these mental disorders, although a minor effect can not be excluded. Future studies on the COMT gene in mentally ill subjects should be stratified by clinical subtypes of the disorder, gender and ethnicity. Studies of endophenotypes instead of the complex disorder seem to be another promising research strategy. Gene-gene and gene-environment interactions should also be considered. The COMT gene is probably not “a gene for” any mental disorder, but the Val158Met polymorphism appears to have pleiotropic effects on human behavior.

Distribution of 1298A > C polymorphism of methylenetetrahydrofolate reductase gene in patients with bipolar disorder and schizophrenia

We investigated the genotype frequency of methylenetetrahydrofolate reductase (MTHFR) 1298A > C polymorphism in the group of patients with bipolar disorder type I (BDI) (n = 200) and schizophrenia (n = 200) and in the control group (n = 300). Odds ratio (OR) for patients with BD and schizophrenia in 1298CC homozygous state was 3.768 (95% CI = 1.752–8.104); P = 0.0003; (P = 0.0006 after Bonferroni correction) and 2.694; (95% CI = 1.207–6.013); P = 0.0123 (P = 0.0246 after Bonferroni correction), respectively. The stratification of patients based on gender revealed significant association of 1298CC genotype with female patients only with BDI (OR = 7.293; 95% CI = 2.017–26.363; P = 0.0005).

Our results confirm association of BD and schizophrenia with the 1p36.3 MTHFR locus and with the methyl group transfer using folate-dependent one-carbon pathway.

Catechol-O-methyltransferase gene expression in stress-induced and non-stress induced schizophrenia

INTRODUCTION

As schizophrenia is a complex mental disorder and the outcome of gene-gene-environmental interactions, there are different possible pathophysiological mechanisms in different schizophrenia subtypes corresponding to various risk factors. This study was aimed at examining the impact of one of the most likely interactions, that is, 'dopamine and stress', in schizophrenia pathogenesis.

METHODS

Here, we investigated the interaction between 'war-related psychological trauma' without brain trauma and catechol-O-methyltransferase gene. Using real-time PCR analysis we measured catechol-O-methyltransferase gene expression level in the blood cells of 66 male subjects in four groups, namely veteran schizophrenia patients as 'stress-exposed schizophrenia' (S-schizophrenia), their healthy brothers as 'their genetically closest relatives' (S-siblings), schizophrenia patients without any history of significant stress as 'non-stress-exposed schizophrenia' (NoS-schizophrenia), and the control group. The results were analyzed by Relative Expression Software Tool 2009 software.

RESULTS

The catechol-O-methyltransferase gene expression was not significantly different between the S-schizophrenia and NoS-schizophrenia groups. However, compared to the control group, the catechol-O-methyltransferase expression was significantly decreased in three groups of S-schizophrenia, their healthy siblings, and NoS-schizophrenia patients.

CONCLUSION

This data supports that reduced blood catechol-O-methyltransferase expression, which may be associated with higher dopamine level, is involved both in stress-induced and non-stress-induced schizophrenia.

Reconstruction and Analysis of Gene Networks of Human Neurotransmitter Systems Reveal Genes with Contentious Manifestation for Anxiety, Depression, and Intellectual Disabilities

Background: The study of the biological basis of anxiety, depression, and intellectual disabilities in humans is one of the most actual problems of modern neurophysiology. Of particular interest is the study of complex interactions between molecular genetic factors, electrophysiological properties of the nervous system, and the behavioral characteristics of people. The neurobiological understanding of neuropsychiatric disorders requires not only the identification of genes that play a role in the molecular mechanisms of the occurrence and course of diseases, but also the understanding of complex interactions that occur between these genes. A systematic study of such interactions obviously contributes to the development of new methods of diagnosis, prevention, and treatment of disorders, as the orientation to allele variants of individual loci is not reliable enough, because the literature describes a number of genes, the same alleles of which can be associated with different, sometimes extremely different variants of phenotypic traits, depending on the genetic background, of their carriers, habitat, and other factors. Results: In our study, we have reconstructed a series of gene networks (in the form of protein–protein interactions networks, as well as networks of transcription regulation) to build a model of the influence of complex interactions of environmental factors and genetic risk factors for intellectual disability, depression, and other disorders in human behavior. Conclusion: A list of candidate genes whose expression is presumably associated with environmental factors and has potentially contentious manifestation for behavioral and neurological traits is identified for further experimental verification.

Genetic Variations of DAOA (rs947267 and rs3918342) and COMT Genes (rs165599 and rs4680) in Schizophrenia and Bipolar I Disorder

Introduction:

Genetic and environmental factors are involved in the incidence of schizophrenia and bipolar disorder. Many reports confirm that several common genes are connected with these two psychotic disorders. Several neurotransmitters may be involved in the molecular mechanisms of schizophrenia and bipolar disorder. We aimed to estimate the role of two talent genes: DAOA in neurotransmission of glutamate and COMT in neurotransmission of dopamine to guide the treatment of schizophrenia and bipolar disorder.

Methods:

Blood samples (n=100 for schizophrenia, n=100 for bipolar I disorder and n=127 for case control) were collected from individuals unrelated in the southwest of Iran. The SNPs (rs947267 and rs3918342 for DAOA gene/rs165599 and rs4680 for COMT gene) were genotyped using the PCR-RFLP method. Our finding was studied by logistic regression and Mantel-Haenszel Chi-square tests.

Results:

We observed an association in rs3918342, rs165599 and rs4680 single nucleotide polymorphisms and schizophrenia and bipolar I disorder. In addition, our data demonstrated that the rs947267 was related to bipolar I disorder but there was no association between this SNP and schizophrenia.

Conclusion:

In conclusion, this result supports the hypothesis that variations in DAOA and COMT genes may play a role in schizophrenia and bipolar disorder.

Mapping the Schizophrenia Genes by Neuroimaging: The Opportunities and the Challenges

Schizophrenia (SZ) is a heritable brain disease originating from a complex interaction of genetic and environmental factors. The genes underpinning the neurobiology of SZ are largely unknown but recent data suggest strong evidence for genetic variations, such as single nucleotide polymorphisms, making the brain vulnerable to the risk of SZ. Structural and functional brain mapping of these genetic variations are essential for the development of agents and tools for better diagnosis, treatment and prevention of SZ. Addressing this, neuroimaging methods in combination with genetic analysis have been increasingly used for almost 20 years. So-called imaging genetics, the opportunities of this approach along with its limitations for SZ research will be outlined in this invited paper. While the problems such as reproducibility, genetic effect size, specificity and sensitivity exist, opportunities such as multivariate analysis, development of multisite consortia for large-scale data collection, emergence of non-candidate gene (hypothesis-free) approach of neuroimaging genetics are likely to contribute to a rapid progress for gene discovery besides to gene validation studies that are related to SZ.

Prospective Memory Performance in Persons With Schizophrenia and Bipolar Disorder and Healthy Persons

PURPOSE

There is a paucity of studies comparing prospective memory (PM) impairment between persons with schizophrenia and bipolar disorder. The aim of this study was to directly compare PM performances of these two groups and healthy controls.

DESIGN AND METHODS

A total of 44 persons with schizophrenia and 76 with bipolar disorder, and 44 healthy controls formed the study sample.

FINDINGS

Patients were found to be impaired in PM relative to controls and the two patient groups showed similar level of PM performance after controlling confounding sociodemographic and clinical variables.

PRACTICE IMPLICATIONS

The findings add to the evidence concerning the neurocognitive similarity between cohorts of schizophrenia and bipolar disorder with respect to PM. Rehabilitative effort in PM remedies for both patient groups is warranted.

Neuroanatomical Abnormalities in Violent Individuals with and without a Diagnosis of Schizophrenia

Several structural brain abnormalities have been associated with aggression in patients with schizophrenia. However, little is known about shared and distinct abnormalities underlying aggression in these subjects and non-psychotic violent individuals. We applied a region-of-interest volumetric analysis of the amygdala, hippocampus, and thalamus bilaterally, as well as whole brain and ventricular volumes to investigate violent (n = 37) and non-violent chronic patients (n = 26) with schizophrenia, non-psychotic violent (n = 24) as well as healthy control subjects (n = 24). Shared and distinct volumetric abnormalities were probed by analysis of variance with the factors violence (non-violent versus violent) and diagnosis (non-psychotic versus psychotic), adjusted for substance abuse, age, academic achievement and negative psychotic symptoms. Patients showed elevated vCSF volume, smaller left hippocampus and smaller left thalamus volumes. This was particularly the case for non-violent individuals diagnosed with schizophrenia. Furthermore, patients had reduction in right thalamus size. With regard to left amygdala, we found an interaction between violence and diagnosis. More specifically, we report a double dissociation with smaller amygdala size linked to violence in non-psychotic individuals, while for psychotic patients smaller size was linked to non-violence. Importantly, the double dissociation appeared to be mostly driven by substance abuse. Overall, we found widespread morphometric abnormalities in subcortical regions in schizophrenia. No evidence for shared volumetric abnormalities in individuals with a history of violence was found. Finally, left amygdala abnormalities in non-psychotic violent individuals were largely accounted for by substance abuse. This might be an indication that the association between amygdala reduction and violence is mediated by substance abuse. Our results indicate the importance of structural abnormalities in aggressive individuals.

Evidence that COMT genotype and proline interact on negative-symptom outcomes in schizophrenia and bipolar disorder

Elevated peripheral proline is associated with psychiatric disorders, and there is evidence that proline is a neuromodulator. The proline dehydrogenase (PRODH) gene, which encodes the enzyme that catalyzes proline catabolism, maps to human chromosome 22q11.2, a region conferring risk of schizophrenia. In the Prodh-null mouse, an interaction between elevated peripheral proline and another 22q11.2 gene, catechol-O-methyltransferase (COMT), on neurotransmission and behavior has been reported. We explored the relationship between fasting plasma proline levels and COMT Val(158)Met genotype on symptoms (positive, negative and total) in schizophrenia patients. In an exploratory study we also examined symptom change in patients with bipolar disorder. There was a significant interaction between peripheral proline and COMT on negative symptoms in schizophrenia (P<0.0001, n=95). In COMT Val/Val patients, high proline was associated with low Scale for the Assessment of Negative Symptom (SANS) scores. In contrast, high proline was associated with high SANS scores in patients carrying a Met allele. The relationship between proline and COMT also appears to modify negative symptoms across psychiatric illness. In bipolar disorder, a significant interaction was also observed on negative-symptom change (P=0.007, n=43). Negative symptoms are intractable and largely unaddressed by current medications. These data indicate a significant interaction between peripheral proline and COMT genotype, influencing negative symptoms in schizophrenia and bipolar disorder. That high proline has converse effects on symptoms by COMT genotype, may have implications for therapeutic decisions.

Association of catechol-O-methyltransferase Val(108/158) Met genetic polymorphism with schizophrenia, P50 sensory gating, and negative symptoms in a Chinese population

Catechol-O-methyltransferase (COMT), an enzyme involved in the degradation and inactivation of the neurotransmitter dopamine, is associated with the sensory gating phenomenon, protecting the cerebral cortex from information overload. The COMT Val(108/158)Met polymorphism is essential for prefrontal cortex processing capacity and efficiency. The current study was designed to investigate the role of COMT Val(108/158)Met polymorphism in development, sensory gating deficit, and symptoms of schizophrenia in Han Chinese population. P50 gating was determined in 139 schizophrenic patients and 165 healthy controls. Positive and Negative Syndrome Scale (PANSS) was used to assess the clinical symptomatology in 370 schizophrenic subjects. COMT Val(108/158)Met polymorphism was genotyped by PCR-restriction fragment length polymorphism (PCR-RFLP). No significant differences in COMT allele and genotype distributions were observed between schizophrenic patients and control groups. Although P50 deficits were present in patients, there was no evidence for an association between COMT Val(108/158)Met polymorphism and the P50 biomarker. Moreover, PANSS negative subscore was significantly higher in Val allele carriers than in Met/Met individuals. The present findings suggest that COMT Val(108/158)Met polymorphism may not contribute to the risk of schizophrenia and to the P50 deficits, but may contribute to the negative symptoms of schizophrenia among Han Chinese.

A Tetra-Primer Amplification Refractory System Technique for the Cost-Effective and Novel Genotyping of Eight Single-Nucleotide Polymorphisms of the Catechol-O-Methyltransferase Gene

AIMS

Catechol-O-methyltransferase (COMT) is an enzyme involved in the degradation of catecholamine neurotransmitters. Due to its role in neurotransmitter flux, multiple COMT variants have been associated with the development of psychiatric disorders. Notably, select single-nucleotide polymorphisms (SNPs) of the COMT gene have been implicated in schizophrenia risk, severity, and treatment response. In recognition of the value of a streamlined genotyping method for COMT SNP detection, this study was designed to develop a simple and economical tetra-primer amplification refractory mutation system (T-ARMS) assay for the concurrent detection of eight COMT SNPs: rs4680, rs737865, rs165599, rs2075507, rs4633, rs4818, rs6269, and rs165774.

MATERIALS AND METHODS

T-ARMS is a genotyping method that uses polymerase chain reaction (PCR) to amplify a multiplex reaction consisting of two primer pairs. T-ARMS primers are customized to each SNP and designed to generate different-sized allele-specific amplicons. This assay was applied to a total of 39 genomic DNA samples. Genotypic designations across the panel of SNPs were subsequently validated by Sanger sequencing.

RESULTS

T-ARMS reliably and unambiguously detected all three genotypes (homozygous wild type, heterozygous, and homozygous mutant) for each of the eight COMT SNPs.

CONCLUSIONS

Compared to traditional low-throughput methods that require post-PCR modification or high-throughput technologies that require sophisticated equipment, T-ARMS is a cost-effective and efficient assay that can be easily adapted by any standard molecular diagnostics laboratory. This T-ARMS assay provides a practical and robust method for COMT SNP detection.

From Linkage Studies to Epigenetics: What We Know and What We Need to Know in the Neurobiology of Schizophrenia

Schizophrenia is a complex psychiatric disorder characterized by the presence of positive, negative, and cognitive symptoms that lacks a unifying neuropathology. In the present paper, we will review the current understanding of molecular dysregulation in schizophrenia, including genetic and epigenetic studies. In relation to the latter, basic research suggests that normal cognition is regulated by epigenetic mechanisms and its dysfunction occurs upon epigenetic misregulation, providing new insights into missing heritability of complex psychiatric diseases, referring to the discrepancy between epidemiological heritability and the proportion of phenotypic variation explained by DNA sequence difference. In schizophrenia the absence of consistently replicated genetic effects together with evidence for lasting changes in gene expression after environmental exposures suggest a role of epigenetic mechanisms. In this review we will focus on epigenetic modifications as a key mechanism through which environmental factors interact with individual's genetic constitution to affect risk of psychotic conditions throughout life.

Working memory genetics in schizophrenia and related disorders: An RDoC perspective

Improved classification of mental disorders through neurobiological measures will require a set of traits that map to transdiagnostic subgroups of patients and align with heritable, core psychopathological processes at the center of the disorders of interest. A promising candidate is working memory (WM) function, for which deficits have been reported across multiple diagnostic entities including schizophrenia, bipolar disorder, ADHD, autism, and major depressive disorder. Here we review genetic working memory associations and their brain functional correlates from the perspective of identifying patient subgroups across conventional diagnostic boundaries, explore the utility of multimodal investigations integrating functional information at the neural systems level and explore potential limitations as well as future directions for research.

Association of the COMT synonymous polymorphism Leu136Leu and missense variant Val158Met with mood disorders

BACKGROUND

Major depressive disorder (MDD) and bipolar disorder (BD) are the two most common mood disorders. Given the recognized involvement of catecholamines in depression, genetic research focused on the evaluation of polymorphisms in genes coding for proteins that regulate neurotransmitter release, transport and degradation. Here we aimed at evaluating the distribution of two genetic variants of catechol-O-methyltransferase (COMT), namely the well characterized missense polymorphism G1947A (Val158Met) and the recently reported synonymous polymorphism C1886G (Leu136Leu), in MDD and BD patients compared with healthy subjects.

METHODS

Genotyping for COMT polymorphisms was carried out by DNA direct sequencing in 112 patients (54 MDD and 58 BD) and 58 healthy subjects.

RESULTS

We did not find significant differences in the Val158Met variant distribution between patients and controls. Instead, we found that the C1886 major allele and the CC1886 wild-type genotype frequencies were significantly higher in controls than in both groups of patients. On the contrary, the G1886 minor allele and the heterozygous CG1886 genotype were significantly more present in both MDD and BD patients than in healthy subjects. When looking at combined polymorphisms, we found a significantly higher frequency of the double heterozygous diplotype CG/GAVal/Met158 in both MDD and BD patients than in controls. Instead, the diplotype CC/GAVal/Met158 showed a significantly higher frequency in controls than in BD patients.

LIMITATIONS

The small size of our study cohort may limit the generalizability of the present findings.

CONCLUSIONS

This work first showed the association of combined Leu136Leu and Val158Met variants of COMT gene with MDD and BD.

COMT and MAO-A polymorphisms and obsessive-compulsive disorder: a family-based association study

Objective

Obsessive-compulsive disorder (OCD) is a common and debilitating psychiatric illness. Although a genetic component contributes to its etiology, no single gene or mechanism has been identified to the OCD susceptibility. The catechol-O-methyltransferase (COMT) and monoamine oxidase A (MAO-A) genes have been investigated in previous OCD studies, but the results are still unclear. More recently, Taylor (2013) in a comprehensive meta-analysis of genetic association studies has identified COMT and MAO-A polymorphisms involved with OCD. In an effort to clarify the role of these two genes in OCD vulnerability, a family-based association investigation was performed as an alternative strategy to the classical case-control design.

Methods

Transmission disequilibrium analyses were performed after genotyping 13 single-nucleotide polymorphisms (eight in COMT and five in MAO-A) in 783 OCD trios (probands and their parents). Four different OCD phenotypes (from narrow to broad OCD definitions) and a SNP x SNP epistasis were also analyzed.

Results

OCD, broad and narrow phenotypes,were not associated with any of the investigated COMT and MAO-A polymorphisms. In addition, the analyses of gene-gene interaction did not show significant epistatic influences on phenotype between COMT and MAO-A.

Conclusions

The findings do not support an association between DSM-IV OCD and the variants of COMT or MAO-A. However, results from this study cannot exclude the contribution of these genes in the manifestation of OCD. The evaluation of broader spectrum phenotypes could help to understand the role of these and other genes in the pathophysiology of OCD and its spectrum disorders.

Do premorbid and post-onset cognitive functioning differ between schizophrenia and bipolar disorder? A systematic review and meta-analysis

BACKGROUND

Schizophrenia (SZ) is characterized by a broad global cognitive impairment that precedes the onset of the disease. By contrast, some studies suggest that premorbid deficits are absent, or even reversed, in bipolar disorder (BD). However, studies have shown impairments in cognitive functioning after the illness onset in both disorders. The aim of this study was to systematically review and meta-analyze those studies that compared premorbid and/or post-onset global cognitive function between SZ and BD.

METHOD

We searched Medline (PubMed), EMBASE and PsycINFO for studies where information on cognitive functioning was collected in both SZ and BD within the same study or using the same methods.

RESULTS

Compared to healthy comparison groups, SZ patients showed a significant premorbid cognitive impairment [standardized mean difference (SMD) -0.597, 95% confidence interval (CI) -0.707 to -0.487, p < 0.0001] and a large post-onset impairment (SMD -1.369, 95% CI -1.578 to -1.160, p < 0.0001). We found small significant deficits in premorbid intellectual function in the BD group when this was assessed retrospectively (-0.147, 95% CI -0.238 to -0.056, p = 0.001) but not prospectively (-0.029, 95% CI -0.199 to + 0.142, p = 0.744), and moderate cognitive impairment after onset (SMD -0.623, 95% CI -0.717 to -0.529, p < 0.0001).

CONCLUSIONS

SZ is characterized by significant deficits in premorbid intellectual function but the evidence regarding premorbid function in BD is equivocal. After illness onset, patients with both disorders seem to suffer a further decline in cognitive function but the magnitude of the impairment remains greater in SZ than in BD.

Stimulants for treating bipolar disorder: pro and con

The role of stimulants for treating severe depression remains controversial, especially when it comes to bipolar depression. Potential benefits have to be weighed against risks, including addictive potential and treatment-emergent mania. But not all stimulants are the same. Modafinil and its R-enantiomer armodafinil seem to have positive augmentation effects when coupled with standard treatment of bipolar depression, while also having a relative low risk of addiction and manic switches. A recent hypothesis derived from the observation of hypovigilance in manic patients postulates that modafinil may also have a beneficial effect in reducing manic behaviors. Further controlled studies are needed to clarify the benefits and risks of stimulants, both in bipolar depression and mania.

The neurobiology of bipolar disorder: identifying targets for specific agents and synergies for combination treatment

Bipolar disorder (BD) is a chronic psychiatric illness described by severe changes in mood. Extensive research has been carried out to understand the aetiology and pathophysiology of BD. Several hypotheses have been postulated, including alteration in genetic factors, protein expression, calcium signalling, neuropathological alteration, mitochondrial dysfunction and oxidative stress in BD. In the following paper, we will attempt to integrate these data in a manner which is to understand targets of treatment and how they may be, in particular, relevant to combination treatment. In summary, the data suggested that BD might be associated with neuronal and glial cellular impairment in specific brain areas, including the prefrontal cortex. From molecular and genetics: (1) alterations in dopaminergic system, through catechol-O-aminotransferase; (2) decreased expression and polymorphism on brain-derived neurotrophic factor; (3) alterations cyclic-AMP responsive element binding; (4) dysregulation of calcium signalling, including genome-wide finding for voltage-dependent calcium channel α-1 subunit are relevant findings in BD. Future studies are now necessary to understand how these molecular pathways interact and their connection to the complex clinical manifestations observed in BD.

Resting-state fMRI connectivity impairment in schizophrenia and bipolar disorder

BACKGROUND

Schizophrenia and bipolar disorder share aspects of phenomenology and neurobiology and thus may represent a continuum of disease. Few studies have compared connectivity across the brain in these disorders or investigated their functional correlates.

METHODS

We used resting-state functional magnetic resonance imaging to evaluate global and regional connectivity in 32 healthy controls, 19 patients with bipolar disorder, and 18 schizophrenia patients. Patients also received comprehensive neuropsychological and clinical assessments. We computed correlation matrices among 266 regions of interest within the brain, with the primary dependent measure being overall global connectivity strength of each region with every other region.

RESULTS

Patients with schizophrenia had significantly lower global connectivity compared with healthy controls, whereas patients with bipolar disorder had global connectivity intermediate to and significantly different from those of patients with schizophrenia and healthy controls. Post hoc analyses revealed that compared with healthy controls, both patient groups had significantly lower connectivity in the paracingulate gyrus and right thalamus. Patients with schizophrenia also had significantly lower connectivity in the temporal occipital fusiform cortex, left caudate nucleus, and left thalamus compared with healthy controls. There were no significant differences among the patient groups in any of these regions. Lower global connectivity among all patients was associated with worse neuropsychological and clinical functioning, but these effects were not specific to any patient group.

CONCLUSIONS

These findings are consistent with the hypothesis that schizophrenia and bipolar disorder may represent a continuum of global disconnectivity in the brain but that regional functional specificity may not be evident.

The CACNA1C risk allele selectively impacts on executive function in bipolar type I disorder

OBJECTIVE

Calcium channels are important for converting electrical activity into biochemical events. A single nucleotide polymorphism (SNP) (rs1006737) in the CACNA1C gene has been strongly associated with increased risk for Bipolar disorder (BD) in genome-wide association studies. Recently, this same SNP has been reported to influence executive function in schizophrenia and controls, but it remains unclear whether this SNP affects behaviour, especially cognition in subjects with BD.

METHOD

A total of 109 BD type I subjects and 96 controls were genotyped for CACNA1C rs1006737 and assessed with an executive function tests battery [Wechsler Adult Intelligence Scale III (WAIS-III) Letter-Number Sequence subtest (WAIS-LNS), digit span (WAISDS), trail making test (TMT), and WCST (Wisconsin Card Sorting Test)].

RESULTS

In patients with BD, the CACNA1C genotype Met/Met was associated with worse performance on all four executive function tests compared to Val/Val. No influence of CACNA1C was observed in the cognitive performance of healthy controls.

CONCLUSION

Our data indicate for the first time that the CACNA1C risk allele is likely associated with executive dysfunction as a trait in BD, as this association was found regardless the presence of mood symptoms. Larger studies should evaluate the potential influence of CACNA1C on other cognitive domains in BD.

Overlapping and distinct gray and white matter abnormalities in schizophrenia and bipolar I disorder

OBJECTIVES

Schizophrenia and bipolar disorder may share common neurobiological mechanisms, but few studies have directly compared gray and white matter structure in these disorders. We used diffusion-weighted magnetic resonance imaging and a region of interest based analysis to identify overlapping and distinct gray and white matter abnormalities in 35 patients with schizophrenia and 20 patients with bipolar I disorder in comparison to 56 healthy volunteers.

METHODS

We examined fractional anisotropy within the white matter and mean diffusivity within the gray matter in 42 regions of interest defined on a probabilistic atlas following non-linear registration of the images to atlas space.

RESULTS

Patients with schizophrenia had significantly lower fractional anisotropy in temporal (superior temporal and parahippocampal) and occipital (superior and middle occipital) white matter compared to patients with bipolar disorder and healthy volunteers. By contrast, both patient groups demonstrated significantly higher mean diffusivity in frontal (inferior frontal and lateral orbitofrontal) and temporal (superior temporal and parahippocampal) gray matter compared to healthy volunteers, but did not differ from each other.

CONCLUSIONS

Our study implicates overlapping gray matter frontal and temporal lobe structural alterations in the neurobiology of schizophrenia and bipolar I disorder, but suggests that temporal and occipital lobe white matter deficits may be an additional risk factor for schizophrenia. Our findings may have relevance for future diagnostic classification systems and the identification of susceptibility genes for these disorders.

Patients with bipolar disorders share similar but attenuated prospective memory impairments with patients with schizophrenia

BACKGROUND

Prospective memory (PM) refers to the ability to remember to carry out an intended action in the future. PM is consistently found to be impaired in individuals with schizophrenia. Bipolar disorder and schizophrenia may represent conditions along a continuum, and share similar neurocognitive and genetic architecture. This study aimed to compare the nature and extent of PM impairment in individuals with schizophrenia and bipolar disorder.

METHOD

Participants were 38 out-patients with schizophrenia and 40 out-patients with bipolar disorder in an early psychosis intervention programme, and 37 healthy controls. Time-, event- and activity-based PMs were assessed using a dual-task laboratory paradigm. Self-reported PM performance was gauged using the Prospective and Retrospective Memory Questionnaire. Analysis of covariance (ANCOVA), with intelligence quotient (IQ) and education included as covariates, was used to examine group difference on various types of PM. Repeated measures of ANCOVA were used to examine the group × PM type interaction effect. Correspondence between laboratory and self-reported PM measures was examined using correlational analysis.

RESULTS

The group × PM type interaction effect was not significant, but the main effect of group was significant. Patients with schizophrenia and patients with bipolar disorder both performed more poorly than healthy participants in PM. The two clinical groups did not significantly differ in PM. Laboratory and self-reported PM measures did not correlate significantly with each other.

CONCLUSIONS

Patients with bipolar disorder shared a similar PM impairment with those with schizophrenia. Findings of this study extended the similarity in neurocognitive impairments between the two psychiatric disorders to PM.

Cognitive manic symptoms in bipolar disorder associated with polymorphisms in the DAOA and COMT genes

INTRODUCTION

Bipolar disorder is characterized by severe mood symptoms including major depressive and manic episodes. During manic episodes, many patients show cognitive dysfunction. Dopamine and glutamate are important for cognitive processing, thus the COMT and DAOA genes that modulate the expression of these neurotransmitters are of interest for studies of cognitive function.

METHODOLOGY

Focusing on the most severe episode of mania, a factor was found with the combined symptoms of talkativeness, distractibility, and thought disorder, considered a cognitive manic symptoms (CMS) factor. 488 patients were genotyped, out of which 373 (76%) had talkativeness, 269 (55%) distractibility, and 372 (76%) thought disorder. 215 (44%) patients were positive for all three symptoms, thus showing CMS (Table 1). As population controls, 1,044 anonymous blood donors (ABD) were used. Case-case and case-control design models were used to investigate genetic associations between cognitive manic symptoms in bipolar 1 disorder and SNPs in the COMT and DAOA genes. [Table: see text].

RESULTS

The finding of this study was that cognitive manic symptoms in patients with bipolar 1 disorder was associated with genetic variants in the DAOA and COMT genes. Nominal association for DAOA SNPs and COMT SNPs to cognitive symptoms factor in bipolar 1 disorder was found in both allelic (Table 2) and haplotypic (Table 3) analyses. Genotypic association analyses also supported our findings. However, only one association, when CMS patients were compared to ABD controls, survived correction for multiple testing by max (T) permutation. Data also suggested interaction between SNPs rs2391191 in DAOA and rs5993883 in COMT in the case-control model. [Table: see text] [Table: see text].

CONCLUSION

Identifying genes associated with cognitive functioning has clinical implications for assessment of prognosis and progression. Our finding are consistent with other studies showing genetic associations between the COMT and DAOA genes and impaired cognition both in psychiatric disorders and in the general population.

Potential role of membrane-bound COMT gene polymorphisms in female depression vulnerability

BACKGROUND

Several polymorphic variants within the catechol-O-methyltransferase (COMT) gene locus have been associated with a number of diverse psychiatric phenotypes including affective disorders. COMT enzyme participates in metabolic pathways involving brain catecholamines, as well as steroid hormones such as estrogens. Given the suggested mood enhancing role of estrogens and the higher prevalence of depression in women, we set out to investigate the potential impact of functional COMT genetic variants on depression and anxiety symptoms in a homogeneous female community sample.

METHODS

We genotyped three common polymorphisms within the COMT gene in a rural female population isolate (n=391) interviewed for the presence of lifetime major depression episodes and generalized anxiety disorder. Furthermore, well validated self-rated questionnaires were administered evaluating state depressive symptoms and neuroticism personality trait. Single-marker and haplotype association analyses were performed.

RESULTS

Two highly correlated markers located in the membrane-bound (MB) COMT promoter region (rs2020917, rs737865) were significantly associated with both self-rated and clinician-rated depressive symptomatology. We did not detect any robust association with generalized anxiety disorder or neuroticism. Exploratory haplotype analysis examining the two promoter markers in combination with the extensively studied val 158met polymorphism (rs4680) did not provide any further support for the contribution of this variant in depressive mood.

LIMITATIONS

The relative small sample size should be considered a limitation of this study.

CONCLUSIONS

Our results provide promising evidence that MB-COMT specific genetic variation may represent an as yet unrecognized genetic factor that influences predisposition to depression amongst females.

Genetic and neurocognitive foundations of emotion abnormalities in bipolar disorder

INTRODUCTION

Bipolar Disorder (BD) is a serious mood disorder, the aetiology of which is still unclear. The disorder is characterised by extreme mood variability in which patients fluctuate between markedly euphoric, irritable, and elevated states to periods of severe depression. The current research literature shows that BD patients demonstrate compromised neurocognitive ability in addition to these mood symptoms. Viable candidate genes implicated in neurocognitive and socioemotional processes may explain the development of these core emotion abnormalities. Additionally, links between faulty neurocognition and impaired socioemotional ability complement genetic explanations of BD pathogenesis. This review examines associations between cognition indexing prefrontal neural regions and socioemotional impairments including emotion processing and regulation. A review of the effect of COMT and TPH2 on these functions is also explored.

METHODS

Major computer databases including PsycINFO, Google Scholar, and Medline were consulted in order to conduct a comprehensive review of the genetic and cognitive literature in BD.

RESULTS

This review determines that COMT and TPH2 genetic variants contribute susceptibility to abnormal prefrontal neurocognitive function which oversees the processing and regulation of emotion. This provides for greater understanding of some of the emotional and cognitive symptoms in BD.

CONCLUSIONS

Current findings in this direction show promise, although the literature is still in its infancy and further empirical research is required to investigate these links explicitly.

Interaction between catechol-O-methyltransferase (COMT) Val158Met genotype and genetic vulnerability to schizophrenia during explicit processing of aversive facial stimuli

BACKGROUND

Emotion dysregulation is a key feature of schizophrenia, a brain disorder strongly associated with genetic risk and aberrant dopamine signalling. Dopamine is inactivated by catechol-O-methyltransferase (COMT), whose gene contains a functional polymorphism (COMT Val158Met) associated with differential activity of the enzyme and with brain physiology of emotion processing. The aim of the present study was to investigate whether genetic risk for schizophrenia and COMT Val158Met genotype interact on brain activity during implicit and explicit emotion processing.

METHOD

A total of 25 patients with schizophrenia, 23 healthy siblings of patients and 24 comparison subjects genotyped for COMT Val158Met underwent functional magnetic resonance imaging during implicit and explicit processing of facial stimuli with negative emotional valence.

RESULTS

We found a main effect of diagnosis in the right amygdala, with decreased activity in patients and siblings compared with control subjects. Furthermore, a genotype × diagnosis interaction was found in the left middle frontal gyrus, such that the effect of genetic risk for schizophrenia was evident in the context of the Val/Val genotype only, i.e. the phenotype of reduced activity was present especially in Val/Val patients and siblings. Finally, a complete inversion of the COMT effect between patients and healthy subjects was found in the left striatum during explicit processing.

CONCLUSIONS

Overall, these results suggest complex interactions between genetically determined dopamine signalling and risk for schizophrenia on brain activity in the prefrontal cortex during emotion processing. On the other hand, the effects in the striatum may represent state-related epiphenomena of the disorder itself.

Evidence for single nucleotide polymorphisms and their association with bipolar disorder

Bipolar disorder (BD) is a complex disorder with a number of susceptibility genes and environmental risk factors involved in its pathogenesis. In recent years, huge progress has been made in molecular techniques for genetic studies, which have enabled identification of numerous genomic regions and genetic variants implicated in BD across populations. Despite the abundance of genetic findings, the results have often been inconsistent and not replicated for many candidate genes/single nucleotide polymorphisms (SNPs). Therefore, the aim of the review presented here is to summarize the most important data reported so far in candidate gene and genome-wide association studies. Taking into account the abundance of association data, this review focuses on the most extensively studied genes and polymorphisms reported so far for BD to present the most promising genomic regions/SNPs involved in BD. The review of association data reveals evidence for several genes (SLC6A4/5-HTT [serotonin transporter gene], BDNF [brain-derived neurotrophic factor], DAOA [D-amino acid oxidase activator], DTNBP1 [dysbindin], NRG1 [neuregulin 1], DISC1 [disrupted in schizophrenia 1]) to be crucial candidates in BD, whereas numerous genome-wide association studies conducted in BD indicate polymorphisms in two genes (CACNA1C [calcium channel, voltage-dependent, L type, alpha 1C subunit], ANK3 [ankyrin 3]) replicated for association with BD in most of these studies. Nevertheless, further studies focusing on interactions between multiple candidate genes/SNPs, as well as systems biology and pathway analyses are necessary to integrate and improve the way we analyze the currently available association data.

The impact of the CACNA1C risk allele on limbic structures and facial emotions recognition in bipolar disorder subjects and healthy controls

INTRODUCTION

Impairments in facial emotion recognition (FER) have been reported in bipolar disorder (BD) during all mood states. FER has been the focus of functional magnetic resonance imaging studies evaluating differential activation of limbic regions. Recently, the α1-C subunit of the L-type voltage-gated calcium channel (CACNA1C) gene has been described as a risk gene for BD and its Met allele found to increase CACNA1C mRNA expression. In healthy controls, the CACNA1C risk (Met) allele has been reported to increase limbic system activation during emotional stimuli and also to impact on cognitive function. The aim of this study was to investigate the impact of CACNA1C genotype on FER scores and limbic system morphology in subjects with BD and healthy controls.

MATERIAL AND METHODS

Thirty-nine euthymic BD I subjects and 40 healthy controls were submitted to a FER recognition test battery and genotyped for CACNA1C. Subjects were also examined with a 3D 3-Tesla structural imaging protocol.

RESULTS

The CACNA1C risk allele for BD was associated to FER impairment in BD, while in controls nothing was observed. The CACNA1C genotype did not impact on amygdala or hippocampus volume neither in BD nor controls.

LIMITATIONS

Sample size.

CONCLUSION

The present findings suggest that a polymorphism in calcium channels interferes FER phenotype exclusively in BD and doesn't interfere on limbic structures morphology.

Pharmacophore modeling and virtual screening studies to design potential COMT inhibitors as new leads

Catechol-O-methyltransferase (COMT) catalyzes the methylation of catecholamines, including neurotransmitters like dopamine, epinephrine and norepinephrine, leading to their degradation. COMT has been a subject of study for its implications in numerous neurological disorders like Parkinson's disease (PD), schizophrenia, and depression. The COMT gene is associated with many allelic variants, the Val108Met polymorphism being the most clinically significant. Availability of crystal structure of both 108V and 108M forms of human soluble-COMT (S-COMT) facilitated us to use structure-based virtual screening approach to obtain new hits by screening a library of CNS permeable compounds from ZINC database. In this study, E-pharmacophore was also used to generate pharmacophore models based on a series of known COMT inhibitors. A five-point pharmacophore model consisting of one hydrogen-bond acceptor (A), two hydrogen bond donors (D), and two aromatic rings (R) was generated for both the polymorphic forms of COMT. These models were then used for filtering ZINC-CNS permeable library to obtain new hits. Physicochemical properties were also calculated for all the hits obtained from both the approaches for favorable ADME properties. These identified hits maybe of interest for further structural optimization and biological evaluation assays.

COMT polymorphisms as predictors of cognitive dysfunction during manic and mixed episodes in bipolar I disorder

OBJECTIVE

The dopaminergic system plays an important role in the prefrontal cortex (PFC) and is believed to mediate cognitive dysfunction (CD) in bipolar disorder (BD). The enzyme catechol-O-methyltransferase (COMT) is involved in the catabolism of dopamine in the PFC, and an association between COMT single nucleotide polymorphisms (SNPs) and BD has been reported. COMT SNPs have also been associated with executive and working memory performance in healthy subjects, patients with schizophrenia, and euthymic BD patients. The objective of this study was to investigate the association between COMT SNPs and acute CD during BD mood episodes.

METHODS

Seventy-two symptomatic, medication-free subjects with bipolar I disorder (BD-I) and 76 healthy controls were evaluated using neuropsychological tests, and genotyped for COMT SNPs rs4680 and rs165599.

RESULTS

Patients undergoing mania and mixed episodes carrying the COMT allele G had better performance on executive function, memory, verbal fluency, and intelligence tests. Moreover, an interaction was detected between the COMT allele G and the Young Mania Rating Scale in BD CD.

CONCLUSIONS

Allele G from COMT SNPs rs4680 and rs165599 may represent reliable state-dependent predictors of global CD during manic and mixed episodes in BD. Further studies in larger samples are necessary to confirm these findings.

Molecular genetics of the psychosis phenotype

OBJECTIVE

Relative to recent successes in elucidating the genetic mechanisms associated with complex diseases, including macular degeneration, diabetes mellitus, type 2, heart disease, and cancer, molecular genetic approaches to psychiatric illness have met with more limited success. While factors such as small allelic effects, allelic heterogeneity, and variation in population substructure have received considerable attention in attempt to explain the paucity of significant results in psychiatric genetics, significantly less focus has been directed toward phenotypic factors.

METHOD

Data derived from molecular genetic studies of the psychosis phenotype in patients with a range of psychiatric illnesses are reviewed.

RESULTS

Available data suggest that genes do not respect the boundaries of the current diagnostic system but may confer risk for symptom-based phenotypic variation that traverses those boundaries.

CONCLUSIONS

Molecular genetic studies offer convincing evidence for a relation between genetic variation and symptom-based phenotypic variation within psychiatric illness. These data may provide novel insights into the pathophysiology of schizophrenia and other related disorders. The exploration of relations between genetic variation and symptom variation that traverses traditional diagnostic boundaries may ultimately lead to more refined classification systems that more closely reflect the genetic etiology of psychiatric illness.

Meta-analysis of genetic association studies on bipolar disorder

Numerous candidate gene association studies of bipolar disorder (BP) have been carried out, but the results have been inconsistent. Individual studies are typically underpowered to detect associations with genes of small effect sizes. We conducted a meta-analysis of published candidate gene studies to evaluate the cumulative evidence. We systematically searched for all published candidate gene association studies of BP. We then carried out a random-effects meta-analysis on all polymorphisms that were reported on by three or more case-control studies. The results from meta-analyses of these genes were compared with the findings from a recent mega-analysis of eleven genome-wide association studies (GWAS) in BP performed by the Psychiatric GWAS Consortium (PGC). A total of 487 articles were included in our review. Among these, 33 polymorphisms in 18 genes were reported on by three or more case-control studies and included in the random-effects meta-analysis. Polymorphisms in BDNF, DRD4, DAOA, and TPH1, were found to be nominally significant with a P-value < 0.05. However, none of the findings were significant after correction for multiple testing. Moreover, none of these polymorphisms were nominally significant in the PGC-BP GWAS. A number of plausible candidate genes have been previously associated with BP. However, the lack of robust findings in our review of these candidate genes highlights the need for more atheoretical approaches to study the genetics of BP afforded by GWAS. The results of this meta-analysis and from other on-going genomic experiments in BP are available online at Metamoodics (http://metamoodics.igm.jhmi.edu).

The genetic association of DUSP6 with bipolar disorder and its effect on ERK activity

The dual-specificity phosphatase 6 (DUSP6) gene resides at chromosome location 12q22-23, which is one of the candidate loci for susceptibility to bipolar disorder and which encodes a phosphatase selective for extracellular signal-regulated kinase (ERK). Previously, we reported a positive association between the functional Leu114Val polymorphism (rs2279574) in DUSP6 and bipolar disorder. Given that the association between DUSP6 and the reported down-regulation of DUSP6 transcript in bipolar postmortem brains were sex-dimorphic, showing significance in women but not men, we performed two independent analyses in homogenous samples of male and female Korean patients with bipolar disorder or schizophrenia using samples enlarged from our previous report. Among the examined DUSP6 SNPs, five (rs769700, rs704076, rs770087, rs808820, and rs2279574) showed positive allelic associations, with the frequency of minor alleles (C, T, G, G, and G) in each SNP significantly increased in women with BD. Consequently, the "C-T-G-G-G" haplotype was significantly over-represented (P=0.016; OR=3.242), whereas the "T-G-T-A-T" haplotype was significantly under-represented (P=0.014; OR=0.697). We found no significant associations with DUSP6 SNPs in men with bipolar disorder or schizophrenia. We also investigated the functions of the functional SNPs' positive associations and found that Leu114Val (rs2279574; T/G) and Ser144Ala (rs770087; T/G) mutations in DUSP6 proteins reduced lithium-induced ERK1/2 phosphorylation in vitro, implicating the dominant active functions. Thus, DUSP6 may not only play important roles in the pathogenesis of bipolar disorder, particularly in women, but also affect the therapeutic response to lithium through modulating lithium's effects on intracellular signaling.

A selective review of multimodal fusion methods in schizophrenia

Schizophrenia (SZ) is one of the most cryptic and costly mental disorders in terms of human suffering and societal expenditure (van Os and Kapur, 2009). Though strong evidence for functional, structural, and genetic abnormalities associated with this disease exists, there is yet no replicable finding which has proven accurate enough to be useful in clinical decision making (Fornito et al., 2009), and its diagnosis relies primarily upon symptom assessment (Williams et al., 2010a). It is likely in part that the lack of consistent neuroimaging findings is because most models favor only one data type or do not combine data from different imaging modalities effectively, thus missing potentially important differences which are only partially detected by each modality (Calhoun et al., 2006a). It is becoming increasingly clear that multimodal fusion, a technique which takes advantage of the fact that each modality provides a limited view of the brain/gene and may uncover hidden relationships, is an important tool to help unravel the black box of schizophrenia. In this review paper, we survey a number of multimodal fusion applications which enable us to study the schizophrenia macro-connectome, including brain functional, structural, and genetic aspects and may help us understand the disorder in a more comprehensive and integrated manner. We also provide a table that characterizes these applications by the methods used and compare these methods in detail, especially for multivariate models, which may serve as a valuable reference that helps readers select an appropriate method based on a given research question.

Placebo-controlled adjunctive trial of pramipexole in patients with bipolar disorder: targeting cognitive dysfunction

OBJECTIVE

Patients with bipolar disorder suffer from significant cognitive impairment that contributes directly to functional disability, yet few studies have targeted these symptoms for treatment, and the optimal study design remains unclear. We evaluated the effects of the dopamine D₂/D₃ receptor agonist pramipexole on cognition in bipolar disorder.

METHOD

Fifty stable outpatients with DSM-IV-diagnosed bipolar I or bipolar II disorder enrolled in an 8-week, double-blind, randomized, placebo-controlled cognitive enhancement trial between July 2006 and April 2010. Patients completed neurocognitive testing at baseline and at week 8, and the primary outcome measures were change scores calculated for each of the 11 tasks. Symptoms and side effects were monitored weekly.

RESULTS

Forty-five patients completed the study (placebo, n = 24; pramipexole, n = 21), and groups were well matched on demographic and clinical features. Primary cognitive analyses indicated no compelling cognitive benefit of pramipexole versus placebo; however, secondary analyses highlight several important methodological issues for future trials and identify a subgroup of patients who might benefit more readily from cognitive enhancement strategies. This outcome suggests that the study design played a very important role in the results-implying a failed rather than altogether negative trial. Specifically, we found that even very subtle, subsyndromal mood symptoms at baseline had a significant influence on the degree of improvement due to active drug, with strictly euthymic patients faring best (multivariate analysis of variance, P = .03 in euthymic subgroup). In addition, the extent of baseline cognitive impairment also contributed to the likelihood of treatment response. Finally, concomitant medications may weaken, or in some cases enhance, response to cognitive treatment and should be accounted for in study design.

CONCLUSIONS

Although our results point toward a lack of clear effect of pramipexole on cognition in bipolar patients, our data revealed a potentially beneficial effect of pramipexole in a subgroup, providing some enthusiasm for pursuing this line of research in the future. Moreover, this study emphasizes the importance of rigorous subject selection for cognitive trials in bipolar illness. Future studies will be necessary to determine the possible clinical and functional implications of these results.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00597896.

Minor physical anomalies in patients with bipolar I disorder and normal controls

BACKGROUND

The neurodevelopmental hypothesis is well established in schizophrenia but has received modest empirical support in bipolar disorder. In schizophrenia it is partly based on the higher prevalence of minor physical anomalies (MPAs), established by many well controlled studies. No studies with comparable designs have been performed in bipolar disorder. The present study aims to establish the rate and topographic distribution of MPAs in bipolar I patients.

METHODS

The subjects were 61 patients (25 men, 36 women) with bipolar I disorder and 103 normal subjects (49 men, 54 women) who were examined for MPAs using a modified version of the Waldrop Physical Anomaly Scale.

RESULTS

The bipolar I patients showed significantly higher regional MPA scores in 3 distinct regions - mouth, feet and head, as well as in the overall scores for the craniofacial complex, the periphery and the total MPA score. Differences were statistically significant for 3 anomalies - high/steepled palate, big gap between I and II toes and furrowed tongue that made significant contribution to the prediction of the patient-control status in a discriminant analysis model.

CONCLUSIONS

Our data suggest that aberrant processes of neurodevelopment may contribute to the etiology of bipolar I disorder. The field is open for further research using modern instruments and designs in order to identify potential biological markers for bipolar disorder.

DNA hypomethylation of MB-COMT promoter in the DNA derived from saliva in schizophrenia and bipolar disorder

The failure in the discovery of etiology of psychiatric diseases, despite extensive genetic studies, has directed the attention of neuroscientists to the contribution of epigenetic modulations, which play important roles in fine-tuning of gene expression in response to environmental factors. Previously, we analyzed 115 human post-mortem brain samples from the frontal lobe and reported DNA hypo methylation of the membrane-bound catechol-O-methyltransferase (MB-COMT) gene promoter, associated with an increased gene expression, as a risk factor for schizophrenia (SCZ) and bipolar disorder (BD). Since most epigenetic modifications are tissue specific and the availability of brain tissue to identify epigenetic aberrations in living subjects is limited, detection of epigenetic abnormalities in other tissues that represent the brain epigenetic marks is one of the critical steps to develop diagnostic and therapeutic biomarkers for mental diseases. Here, hypothesizing that; those factors that lead to the brain MB-COMT promoter DNA hypo-methylation may also cause concurrent epigenetic aberrations in peripheral tissues, we analyzed MB-COMT promoter methylation in DNA derived from the saliva in SCZ, BD and their first-degree relatives (20 cases each) as well as 25 control subjects. Using bisulfite DNA sequencing and quantitative methylation specific PCR (qMSP), we found that similar to the brain, MB-COMT promoter was hypo-methylated (∼50%) in DNA derived from the saliva in SCZ and BD compared to the control subjects (p = 0.02 and 0.037, respectively). These studies suggest that DNA methylation analysis of MB-COMT promoter in saliva can potentially be used as an available epigenetic biomarker for disease state in SCZ and BD.

Brain cortical thickness and surface area correlates of neurocognitive performance in patients with schizophrenia, bipolar disorder, and healthy adults

Relationships between cortical brain structure and neurocognitive functioning have been reported in schizophrenia, but findings are inconclusive, and only a few studies in bipolar disorder have addressed this issue. This is the first study to directly compare relationships between cortical thickness and surface area with neurocognitive functioning in patients with schizophrenia (n = 117) and bipolar disorder (n = 121) and healthy controls (n = 192). MRI scans were obtained, and regional cortical thickness and surface area measurements were analyzed for relationships with test scores from 6 neurocognitive domains. In the combined sample, cortical thickness in the right rostral anterior cingulate was inversely related to working memory, and cortical surface area in four frontal and temporal regions were positively related to neurocognitive functioning. A positive relationship between left transverse temporal thickness and processing speed was specific to schizophrenia. A negative relationship between right temporal pole thickness and working memory was specific to bipolar disorder. In conclusion, significant cortical structure/function relationships were found in a large sample of healthy controls and patients with schizophrenia or bipolar disorder. The differences that were found between schizophrenia and bipolar may indicate differential relationship patterns in the two disorders, which may be of relevance for understanding the underlying pathophysiology.

Sensory gating deficit is associated with catechol-O-methyltransferase polymorphisms in bipolar disorder

OBJECTIVES. Recent studies have evidenced that bipolar patients show a sensory gating deficit (P50). Among the neural systems that could be influencing this electrophysiological phenotype, dopamine seems to play an important role. We hypothesize that catechol-O-methyltransferase (COMT), the main metabolizer of dopamine in prefrontal cortex, is related to this deficit. METHODS. We selected three polymorphisms in COMT gene: rs2075507 (Promoter 2 region), Val158Met (rs4680) and rs165599 (3' region). A case-control study was performed in 784 controls and 238 bipolar patients. Besides, 122 euthymic bipolar subjects and 95 healthy subjects carried out a sensory gating task (P50). RESULTS. Polymorphism rs165599 in the COMT gene was associated with susceptibility to bipolar disorder (BD), mainly in women (AG: OR = 1.46; GG: OR = 1.84; P = 0.03). In the female group, haplotype AAG was associated with an OR = 7.6. Subjects who carried Val158 allele evidenced a deficit in suppression (P = 0.046) and rs165599 allele G carriers (mainly in homozygosis) had a bigger S2 amplitude and a higher S2/S1 ratio (1.6(e-5) < P < 0.01). Not a single association was proven in the control group. CONCLUSIONS. Our results support the association of the COMT gene with BD and with one of its potential endophenotypes, auditory sensory gating deficit, measured by the P50 paradigm.

P2RX7 gene is associated consistently with mood disorders and predicts clinical outcome in three clinical cohorts

We investigated the effect of nine candidate genes on risk for mood disorders, hypothesizing that predisposing gene variants not only elevate the risk for mood disorders but also result in clinically significant differences in the clinical course of mood disorders. We genotyped 178 DSM-IV bipolar I and II and 272 major depressive disorder patients from three independent clinical cohorts carefully diagnosed with semistructured interviews and prospectively followed up with life charts for a median of 60 (range 6-83) months. Healthy control subjects (n = 1322) were obtained from the population-based national Health 2000 Study. We analyzed 62 genotyped variants within the selected genes (BDNF, NTRK2, SLC6A4, TPH2, P2RX7, DAOA, COMT, DISC1, and MAOA) against the presence of mood disorder, and in post-hoc analyses, specifically against bipolar disorder or major depressive disorder. Estimates for time ill were based on life charts. The P2RX7 gene variants rs208294 and rs2230912 significantly elevated the risk for a familial mood disorder (OR = 1.35, P = 0.0013, permuted P = 0.06, and OR = 1.44, P = 0.0031, permuted P = 0.17, respectively). The results were consistent in all three cohorts. The same risk alleles predicted more time ill in all cohorts (OR 1.3, 95% CI 1.1-1.6, P = 0.0069 and OR 1.7, 95% CI 1.3-2.3, P = 0.0002 with rs208294 and rs2230912, respectively), so that homozygous carriers spent 12 and 24% more time ill. P2RX7 and its risk alleles predisposed to mood disorders consistently in three independent clinical cohorts. The same risk alleles resulted in clinically significant differences in outcome of patients with major depressive and bipolar disorder.

Do COMT, BDNF and NRG1 polymorphisms influence P50 sensory gating in psychosis?

BACKGROUND

Auditory P50 sensory gating deficits correlate with genetic risk for schizophrenia and constitute a plausible endophenotype for the disease. The well-supported role of catechol-O-methyltransferase (COMT), brain-derived neurotrophic factor (BDNF) and neuregulin 1 (NRG1) genes in neurodevelopment and cognition make a strong theoretical case for their influence on the P50 endophenotype.

METHOD

The possible role of NRG1, COMT Val158Met and BDNF Val66Met gene polymorphisms on the P50 endophenotype was examined in a large sample consisting of psychotic patients, their unaffected relatives and unrelated healthy controls using linear regression analyses.

RESULTS

Although P50 deficits were present in patients and their unaffected relatives, there was no evidence for an association between NRG1, COMT Val158Met or BDNF Val66Met genotypes and the P50 endophenotype.

CONCLUSIONS

The evidence from our large study suggests that any such association between P50 indices and NRG1, COMT Val158Met or BDNF Val66Met genotypes, if present, must be very subtle.

Psychiatric outcomes in young children with a history of institutionalization

Children raised in institutions, considered an extreme example of social deprivation, are one group through which we can better understand the impact of neglect on child health and development. The Bucharest Early Intervention Project (BEIP) is the first randomized, controlled trial of foster care as an intervention for institutionalized children. In this review we describe the mental health outcomes from the BEIP. Specifically, we report findings on attachment styles, attachment disorders, emotional reactivity, and psychiatric symptomatology for children in the BEIP. We describe the impact of the foster care intervention on these outcomes and also describe how outcomes differ by gender and by length of time spent in the institution. In addition, we explore the influence of genetic variation on individual outcomes and recovery from early severe social deprivation, as well as the role of differences in brain development in mediating later psychiatric morbidity. The results from the BEIP confirm and extend the previous findings on the negative sequelae of early institutional care on mental health. The results also underscore the benefit of early family placement for children living in institutions.

Are Bipolar Disorder and Schizophrenia Neuroanatomically Distinct? An Anatomical Likelihood Meta-analysis

Objective: There is renewed debate on whether modern diagnostic classification should adopt a dichotomous or dimensional approach to schizophrenia and bipolar disorder. This study synthesizes data from voxel-based studies of schizophrenia and bipolar disorder to estimate the extent to which these conditions have a common neuroanatomical phenotype. Methods: A post-hoc meta-analytic estimation of the extent to which bipolar disorder, schizophrenia, or both conditions contribute to brain gray matter differences compared to controls was achieved using a novel application of the conventional anatomical likelihood estimation (ALE) method. 19 schizophrenia studies (651 patients and 693 controls) were matched as closely as possible to 19 bipolar studies (540 patients and 745 controls). Result: Substantial overlaps in the regions affected by schizophrenia and bipolar disorder included regions in prefrontal cortex, thalamus, left caudate, left medial temporal lobe, and right insula. Bipolar disorder and schizophrenia jointly contributed to clusters in the right hemisphere, but schizophrenia was almost exclusively associated with additional gray matter deficits (left insula and amygdala) in the left hemisphere. Limitation: The current meta-analytic method has a number of constraints. Importantly, only studies identifying differences between controls and patient groups could be included in this analysis. Conclusion: Bipolar disorder shares many of the same brain regions as schizophrenia. However, relative to neurotypical controls, lower gray matter volume in schizophrenia is more extensive and includes the amygdala. This fresh application of ALE accommodates multiple studies in a relatively unbiased comparison. Common biological mechanisms may explain the neuroanatomical overlap between these major disorders, but explaining why brain differences are more extensive in schizophrenia remains challenging.