COMT Val158Met polymorphism in schizophrenia with obsessive-compulsive disorder: a case-control study

Genetic and epigenetic architecture of Obsessive-Compulsive Disorder: In search of possible diagnostic and prognostic biomarkers

Obsessive-Compulsive Disorder (OCD) is a prevalent and severe clinical condition whose hallmarks are excessive, unwanted thoughts (obsessions) and repetitive behaviors (compulsions). The onset of symptoms generally occurs during pre-adult life and typically affects subjects in different aspects of their life's, compromising social and professional relationships. Although robust evidence suggests a genetic component in the etiopathogenesis of OCD, the causes of the disorder are still not completely understood. It is thus of relevance to take into account how genes interact with environmental risk factors, thought to be mediated by epigenetic mechanisms. We here provide an overview of genetic and epigenetic mechanisms of OCD, focusing on the modulation of key central nervous system genes, in the attempt to suggest possible disease biomarkers.

Catechol-O-methyltransferase gene Val158Met polymorphism and obsessive compulsive disorder susceptibility: a meta-analysis

Obsessive-compulsive disorder (OCD) is a common psychiatric disorder that affects approximately 1-3% of the general population. It is characterized by disabling obsessions (intrusive unwanted thoughts) and/or compulsions (ritualized repetitive behaviors). Catechol-O-methyltransferase (COMT) enzyme has an important role in inactivation of dopamine and higher dopamine levels may be implicated in OCD, hence COMT gene is a suitable candidate for OCD. Several case-control studies have evaluated the role of COMT Val 158Met (rs4680;472G- > A) polymorphism as a risk factor for OCD but the results remained inconclusive, hence present meta-analysis was designed to find out correct assessment. All studies that investigated the association of COMT gene Val158Met polymorphism with OCD risk, were considered in the present meta-analysis. Statistical analysis was performed with the software program MetaAnalyst. In the current meta-analysis, 14 case-control studies with 1435 OCD cases and 2753 healthy controls were included. The results indicated significant association between COMT Val158Met polymorphism and OCD risk using allele contrast, homozygote and dominant models (OR_{A vs G} = 1.14; 95% CI = 1.02-1.27; p = 0.01; OR_AAvs.GG = 1.33; 95% CI = 1.09-1.62, p = 0.004; OR_{AA + AGvs.GG} = 1.14; 95% CI = 1.0-1.32; p = 0.04). In subgroup analysis based on case gender, meta-analysis of male cases showed significant association using all five genetic models (OR_AAvsGG = 1.99; 95%CI = 1.42-2.59; p = <0.001; OR_{AA + AGvs.GG} = 1.59; 95% CI = 1.20-2.10; p = 0.001), but did not show any association between COMT Val 158Met polymorphism and OCD risk in females. In conclusion, results of present meta-analysis supports that the COMT Val158Met polymorphism is a risk factor for OCD especially for males.

Genetics of sex differences in neuroanatomy and function

Sex differences are observed at many distinct biologic levels, such as in the anatomy and functioning of the brain, behavior, and susceptibility to neuropsychiatric disorders. Previously, these differences were believed to entirely result from the secretion of gonadal hormones; however, recent research has demonstrated that differences are also the consequence of direct or nonhormonal effects of genes located on the sex chromosomes. This chapter reviews the four core genotype model that separates the effects of hormones and sex chromosomes and highlights a few genes that are believed to be partly responsible for sex dimorphism of the brain, in particular, the Sry gene. Genetics of the brain's neurochemistry is discussed and the susceptibility to certain neurologic and psychiatric disorders is reviewed. Lastly, we discuss the sex-specific genetic contribution in disorders of sexual development. The precise molecular mechanisms underlying these differences are currently not entirely known. An increased knowledge and understanding of the role of candidate genes will undeniably be of great aid in elucidating the molecular basis of sex-biased disorders and potentially allow for more sex-specific therapies.

Haplotypic and Genotypic Association of Catechol-O-Methyltransferase rs4680 and rs4818 Polymorphisms and Treatment Resistance in Schizophrenia

Treatment-resistant schizophrenia (TRS) continues to be a challenge. It was related to different factors, including alterations in the activity of brain dopaminergic system, which could be influenced by the dopamine-degrading enzyme, catechol-O-methyltransferase (COMT). Variants of the COMT gene have been extensively studied as risk factors for schizophrenia; however, their association with TRS has been poorly investigated. The aim of the present study was to determine the haplotypic and genotypic association of COMT rs4680 and rs4818 polymorphisms with the presence of TRS. Overall, 931 Caucasian patients diagnosed with schizophrenia (386 females and 545 males) were included, while 270 participants met the criteria for TRS. In males, no significant haplotypic and genotypic associations between COMT rs4680 and rs4818 polymorphisms and TRS were detected. However, genotypic analyses demonstrated higher frequency of COMT rs4680 AA genotype carriers compared to G-allele carriers (p = 0.033) and higher frequency of COMT rs4818 CC genotype carriers than G-allele carriers (p = 0.014) in females with TRS. Haplotype analyses confirmed that the presence of the G allele in females was associated with lower risk of TRS. In women with TRS, the high activity G-G/G-G haplotype was rare, while carriers of other haplotypes were overrepresented (p = 0.009). Such associations of COMT rs4680 and rs4818 high-activity (G variants), as well as G-G/G-G haplotype, with the lower risk of TRS in females, but not in males, suggest significant, but sex-specific influence of COMT variants on the development of treatment-resistance in patients with schizophrenia. However, due to relatively low number of females, those findings require replication in a larger sample.

No association between the COMT Val158Met polymorphism and the long-term clinical response in obsessive-compulsive disorder in the Japanese population

OBJECTIVE

Catechol-O-methyltransferase (COMT) is an enzyme that participates in the metabolic inactivation of dopamine and norepinephrine, and the Met allele of the COMT Val158Met polymorphism is associated with lower enzymatic activity. The purpose of the present study was to investigate whether this functional variant is associated with obsessive-compulsive disorder (OCD) and the clinical responses in OCD.

METHODS

We first performed a case-control association study between the COMT Val158Met polymorphism and OCD (171 cases and 944 controls). Then, we examined the association between this polymorphism and the clinical responses in 91 of the OCD patients.

RESULTS

Our study did not find a significant association between the Met allele and OCD risk or between the Met allele and clinical responses (p > 0.05).

CONCLUSION

The present case-control/pharmacogenetic study did not provide clear evidence that the COMT Val158Met polymorphism is a predictor of OCD or of OCD patients' clinical responses.

Physicochemical evolution and molecular adaptation of the cetacean osmoregulation-related gene UT-A2 and implications for functional studies

Cetaceans have an enigmatic evolutionary history of re-invading aquatic habitats. One of their essential adaptabilities that has enabled this process is their homeostatic strategy adjustment. Here, we investigated the physicochemical evolution and molecular adaptation of the cetacean urea transporter UT-A2, which plays an important role in urine concentration and water homeostasis. First, we cloned UT-A2 from the freshwater Yangtze finless porpoise, after which bioinformatics analyses were conducted based on available datasets (including freshwater baiji and marine toothed and baleen whales) using MEGA, PAML, DataMonkey, TreeSAAP and Consurf. Our findings suggest that the UT-A2 protein shows folding similar to that of dvUT and UT-B, whereas some variations occurred in the functional So and Si regions of the selectivity filter. Additionally, several regions of the cetacean UT-A2 protein have experienced molecular adaptations. We suggest that positive-destabilizing selection could contribute to adaptations by influencing its biochemical and conformational character. The conservation of amino acid residues within the selectivity filter of the urea conduction pore is likely to be necessary for urea conduction, whereas the non-conserved amino acid replacements around the entrance and exit of the conduction pore could potentially affect the activity, which could be interesting target sites for future mutagenesis studies.

Association of the catechol-O-methyltransferase val158met polymorphism and anxiety-related traits: a meta-analysis

OBJECTIVES

The aims of this study were (i) to examine genotypic association of the catechol-O-methyltransferase (COMT) val158met polymorphism with anxiety-related traits with a meta-analysis; (ii) to examine sex and ethnicity as moderators of the association; and (iii) to evaluate whether the association differed by particular anxiety traits.

METHODS

Association studies of the COMT val158met polymorphism and anxiety traits were identified from the PubMed or PsycInfo databases, conference abstracts, and listserv postings. Exclusion criteria were (a) pediatric samples, (b) exclusively clinical samples, and (c) samples selected for a nonanxiety phenotype. Standardized mean differences in anxiety between genotypes were aggregated to produce mean effect sizes across all available samples, and for subgroups stratified by sex and ethnicity (Whites vs. Asians). Construct-specific analysis was conducted to evaluate the association of COMT with neuroticism, harm avoidance, and behavioral inhibition.

RESULTS

Twenty-seven eligible studies (N=15 979) with available data were identified. Overall findings indicate sex-specific and ethnic-specific effects: valine homozygotes had higher neuroticism than methionine homozygotes in studies of White males [mean effect size(Equation is included in full-text article.)=0.13; 95% CI 0.02, 0.25; P=0.03], and higher harm avoidance in studies of Asian males ((Equation is included in full-text article.)=0.43; 95% CI 0.14, 0.72; P=0.004). No significant associations were found in women and effect sizes were diminished when studies were aggregated across ethnicity or anxiety traits.

CONCLUSION

This meta-analysis provides evidence for sex and ethnic differences in the association of the COMT val158met polymorphism with anxiety traits. Our findings contribute to current knowledge on the relation between prefrontal dopaminergic transmission and anxiety.

Genetics of obsessive–compulsive disorder: a research update

The genetic study of obsessive-compulsive disorder (OCD) has made significant gains in the past decade. However, etiological gene findings are still elusive. Epidemiological studies, including family and twin studies, strongly support a genetic component for OCD. In addition, complex segregation analyses suggest the presence of at least one major gene. The neurobiology of OCD also lends support to the notion that programmed CNS-based biological processes underlie OCD symptom expression, with mapping of brain circuits to fronto-subcortical circuits in a consistent manner. Genetic linkage studies of OCD, using families with multiple affected relatives, have generated several suggestive linkage peaks, regions that may harbor a gene or genes for OCD. However, the presence of multiple linkage peaks has added to the complexity of OCD genetics, suggesting that the exploration of gene-gene interactions and gene-environment interactions, in addition to the exploration of alternate phenotypes based on symptom expression, age at onset or comorbid conditions, may be key in locating etiologic genes. Finally, candidate gene studies, while promising, are not yet associated with linkage regions, except in the case of the glutamate transporter gene SLC1A1 in 9p24. While OCD appears to have a genetic component, additional innovative research is needed to unravel the genetic influences in the disorder.

Molecular genetics of obsessive-compulsive disorder: a comprehensive meta-analysis of genetic association studies

Twin studies indicate that obsessive-compulsive disorder (OCD) is strongly influenced by additive genetic factors. Yet, molecular genetic association studies have yielded inconsistent results, possibly because of differences across studies in statistical power. Meta-analysis can yield greater power. This study reports the first comprehensive meta-analysis of the relationship between OCD and all previously examined polymorphisms for which there was sufficient information in the source studies to compute odds ratios (ORs). A total of 230 polymorphisms from 113 genetic association studies were identified. A full meta-analysis was conducted for 20 polymorphisms that were examined in 5 or more data sets, and a secondary meta-analysis (limited to the computation of mean effect sizes) was conducted for 210 polymorphisms that were examined in fewer than 5 data sets. In the main meta-analysis, OCD was associated with serotonin-related polymorphisms (5-HTTLPR and HTR2A) and, in males only, with polymorphisms involved in catecholamine modulation (COMT and MAOA). Nonsignificant trends were identified for two dopamine-related polymorphisms (DAT1 and DRD3) and a glutamate-related polymorphism (rs3087879). The secondary meta-analysis identified another 18 polymorphisms with significant ORs that merit further investigation. This study demonstrates that OCD is associated with multiple genes, with most having a modest association with OCD. This suggests a polygenic model of OCD, consistent with twin studies, in which multiple genes make small, incremental contributions to the risk of developing the disorder. Future studies, with sufficient power to detect small effects, are needed to investigate the genetic basis of OCD subtypes, such as early vs late onset OCD.

The Val158Met COMT polymorphism is a modifier of the age at onset in Parkinson's disease with a sexual dimorphism

The catechol-O-methyltranferase (COMT) is one of the main enzymes that metabolise dopamine in the brain. The Val158Met polymorphism in the COMT gene (rs4680) causes a trimodal distribution of high (Val/Val), intermediate (Val/Met) and low (Met/Met) enzyme activity. We tested whether the Val158Met polymorphism is a modifier of the age at onset (AAO) in Parkinson's disease (PD). The rs4680 was genotyped in a total of 16 609 subjects from five independent cohorts of European and North American origin (5886 patients with PD and 10 723 healthy controls). The multivariate analysis for comparing PD and control groups was based on a stepwise logistic regression, with gender, age and cohort origin included in the initial model. The multivariate analysis of the AAO was a mixed linear model, with COMT genotype and gender considered as fixed effects and cohort and cohort-gender interaction as random effects. COMT genotype was coded as a quantitative variable, assuming a codominant genetic effect. The distribution of the COMT polymorphism was not significantly different in patients and controls (p=0.22). The Val allele had a significant effect on the AAO with a younger AAO in patients with the Val/Val (57.1±13.9, p=0.03) than the Val/Met (57.4±13.9) and the Met/Met genotypes (58.3±13.5). The difference was greater in men (1.9 years between Val/Val and Met/Met, p=0.007) than in women (0.2 years, p=0.81). Thus, the Val158Met COMT polymorphism is not associated with PD in the Caucasian population but acts as a modifier of the AAO in PD with a sexual dimorphism: the Val allele is associated with a younger AAO in men with idiopathic PD.

The role of the catechol-O-methyltransferase (COMT) gene in personality and related psychopathological disorders

This review provides a short overview of the most significant biologically oriented theories of human personality. Personality concepts of Eysenck, Gray and McNaughton, Cloninger and Panksepp will be introduced and the focal evidence for the heritability of personality will be summarized. In this context, a synopsis of a large number of COMT genetic association studies (with a focus on the COMT Val158Met polymorphism) in the framework of the introduced biologically oriented personality theories will be given. In line with the theory of a continuum model between healthy anxious behavior and related psychopathological behavior, the role of the COMT gene in anxiety disorders will be discussed. A final outlook considers new research strategies such as genetic imaging and epigenetics for a better understanding of human personality.

Association of catechol-O-methyl transferase (COMT) gene -287A/G polymorphism with susceptibility to obsessive-compulsive disorder in Chinese Han population

Several studies suggested a genetic component in the etiology of obsessive-compulsive disorder (OCD). COMT involves in the degradation of dopamine and norepinephrin. As another functional SNP locus, COMT -287A/G polymorphism showed an effect on enzyme activity, suggesting that it may influence brain dopamine levels. To identify association of COMT -287A/G polymorphism with susceptibility to OCD in Chinese Han population. We evaluate the genetic contribution of the COMT -287A/G polymorphism in 200 OCD patients and 403 OCD-free control of Chinese Han population by PCR-RFLP. In addition, we investigate whether COMT -287A/G polymorphism is associated with one or more of these symptom dimensions or other characteristics such as sex, age of onset, and tic-relatedness and evaluate the association of the factorial structure of OCD symptoms from the Y-BOCS checklist with the COMT -287A/G polymorphism. A statistical difference was found in the genotypic frequencies of COMT -287A/G between the OCD and control groups (χ(2)  = 13.99, DF = 2, P = 0.00091) and in the genotypic frequencies of GG genotype versus AA and AG genotypes of COMT -287 (χ(2)  = 13.49, DF = 1, P = 0.00024, OR = 3.43, 95% CI = 1.78-6.62). There was a trend for an association in the genotypic distributions of COMT -287A/G polymorphism of males (χ(2)  = 27.81; DF = 2; P < 0.001) and females (χ(2)  = 7.31; DF = 2; P = 0.026) between the OCD patients and the controls. Using principal component analysis, we derived 5 factors from 12 main contents of OCD symptoms from the Y-BOCS checklist and found no association with COMT -287A/G polymorphism. Our study supports the involvement of the COMT -287A/G polymorphism in the genetic susceptibility to OCD in Chinese Han population.

Heterozygosity at catechol-O-methyltransferase Val158Met and schizophrenia: new data and meta-analysis

Catechol-O-methyltransferase (COMT) has been largely studied in relation to schizophrenia susceptibility. Most studies focused on the functional single nucleotide polymorphism (SNP) rs4680 that causes a substitution of Val by Met at codon 158 of the COMT protein. Recent meta-analyses do not support an association between allelic variants at rs4680 and schizophrenia. However, the putative role of overdominance has not been tested in meta-analyses, despite its biological plausibility. In this work, we tested the overdominant model in two Spanish samples (from Valencia and Santiago de Compostela), representing a total of 762 schizophrenic patients and 1042 controls, and performed a meta-analysis of the available studies under this model. A total of 51 studies comprising 13,894 schizophrenic patients and 16,087 controls were included in the meta-analysis, that revealed a small but significant protective effect for heterozygosity at rs4680 (pooled OR=0.947, P=0.023). Post-hoc analysis on southwestern European samples suggested a stronger effect in these populations (pooled OR=0.813, P=0.0009). Thus, the COMT functional polymorphism rs4680 contributes to schizophrenia genetic susceptibility under an overdominant model, indicating that both too high and too low levels of dopamine (DA) signalling may be risk factors. This effect can be modulated by genetic background.

The genetics of obsessive-compulsive disorder and Tourette syndrome: an epidemiological and pathway-based approach for gene discovery

OBJECTIVE

To provide a contemporary perspective on genetic discovery methods applied to obsessive-compulsive disorder (OCD) and Tourette syndrome (TS).

METHOD

A review of research trends in genetics research in OCD and TS is conducted, with emphasis on novel approaches.

RESULTS

Genome-wide association studies (GWAS) are now in progress in OCD and TS and will provide a platform for future discovery of common gene variants. Optimally, newer next-generation genome sequencing methods can also be used to detect larger effect genes (rare gene variants), taking advantage of pedigrees. Studies of gene networks or sets rather than individual genes will be required to elucidate biological etiology, as neural systems appear to act redundantly. Newer phenotyping strategies, such as symptom-based subtypes, cross-disorder latent class types, and intermediate phenotypes (endophenotypes) will need to be developed and tested to better align clinical and physiological measures with genetic architecture.

CONCLUSION

Although genetics research has made significant advances based on computational strength and bioinformatics advances, newer approaches to phenotyping and judicious study of gene etiological networks will be needed to uncover the genetic etiology of OCD and TS.

The role of the COMT Val(158)Met polymorphism in the phenotypic expression of obsessive-compulsive disorder

Obsessive-Compulsive Disorder (OCD) is characterized by the presence of obsessions and compulsions, and shows considerable phenotypic variability. Family and twin studies have indicated a genetic component in the etiology of OCD, and the catechol-O-methyl transferase (COMT) gene is an important candidate gene for OCD. This study investigates the influence of the functional COMT Val158Met polymorphism on the phenotypic expression of OCD, using an item-level factor-analytic approach in a large sample. The COMT Val158Met variant was genotyped in 373 patients and 462 controls. It was tested whether there was an association between the COMT Val158Met polymorphism and OCD or dimensional phenotypes such as YBOCS severity score, age of onset of obsessive-compulsive symptoms and six symptom dimensions recently found in a large item-level factor-analytic study [Katerberg et al., submitted]. We further investigated possible sex-specific associations between the COMT Val158Met polymorphism and OCD or dimensional phenotypes. There was a trend for an association of the COMT 158Met allele with OCD in males, and an interaction between the COMT Val158Met genotype and sex on the somatic and sensory phenomena symptom dimension, with females showing lower scores. In conclusion, a dimensional approach seems fruitful in detecting genes of importance for OCD.

Importance of the COMT gene for sex differences in brain function and predisposition to psychiatric disorders

As outlined elsewhere in this volume, sex differences can affect brain function and its dysfunction in psychiatric disorders. It is known that genetic factors contribute to these sex dimorphisms, but the individual genes have rarely been identified. The catechol-O-methyltransferase (COMT) gene, which encodes an enzyme that metabolises catechol compounds, including dopamine, is a leading candidate in this regard. COMT's enzyme activity, and the neurochemistry and behaviour of COMT knockout mice are both markedly sexually dimorphic. Furthermore, genetic associations between COMT and psychiatric phenotypes frequently show differences between men and women. Although many of these differences are unconfirmed or minor, some appear to be of reasonable robustness and magnitude and are reviewed in this chapter. Sexually dimorphic effects of COMT are usually attributed to transcriptional regulation by oestrogens; however, a careful examination of the literature suggests that additional mechanisms are likely to be at least as important. Here, we review the evidence for a sexually dimorphic influence of COMT upon psychiatric phenotypes and brain function, and discuss potential mechanisms by which this may occur. We conclude that despite the evidence being incomplete, there are accumulating and in places compelling data showing that COMT has markedly sexually dimorphic effects on brain function and its dysfunction in psychiatric disorders. Although oestrogenic regulation of COMT is probably partially responsible for these sex differences, other mechanisms are likely also involved. Since sex differences in the genetic architecture of brain function and psychiatric disorders are the rule not the exception, we anticipate that additional evidence will emerge for sexual dimorphisms, not only in COMT but also in many other autosomal genes.

Overview of genetics and obsessive-compulsive disorder

This paper reviews the current state of research into the genetics of obsessive-compulsive disorder (OCD). Heredity has a major role in OCD etiology. This evidence comes from several methodological approaches such as family, twin, and segregation analysis studies. A major single gene effect as well as a polygenic hypothesis has been suggested based on segregation studies. In addition, candidate gene association and linkage analyses have shown not only one gene, but a few interesting genes and areas of the genome that may be relevant in OCD. In this search for genes, new definitions of the OCD phenotype have emerged, and some of them may be considered intermediate phenotypes between the gene effect and OCD-DSM-IV diagnosis. The phenotypic and genetic heterogeneity of OCD magnifies the challenge of locating susceptibility genes; at the same time, the identification of vulnerability genes will elucidate the identification of subtypes or dimensions of the disorder. Therefore research strategies that take advantage of clinical subtyping and that redefine the OCD phenotype in the context of genetic studies may potentially contribute to the nosology of OCD and ultimately pathophysiology. There is a lack of understanding about how genes and environment interact in OCD. However, there are some reports that will be discussed, which have attempted to evaluate how the environment contributes to OCD.

Gonadectomy and hormone replacement exert region- and enzyme isoform-specific effects on monoamine oxidase and catechol-O-methyltransferase activity in prefrontal cortex and neostriatum of adult male rats

Sex differences and gonadal hormone influences are well known for diverse aspects of forebrain amine and indolamine neurotransmitter systems, the cognitive and affective functions they govern and their malfunction in mental illness. This study explored whether hormone regulation/dysregulation of these systems could be related to gonadal steroid effects on catechol-O-methyltransferase and monoamine oxidase which are principal enzymatic controllers of forebrain dopamine, serotonin and norepinephrine levels. Driven by male over female differences in cortical enzyme activities, by male-specific associations between monoamine oxidase and catechol-O-methyltransferase gene polymorphisms and cognitive and dysfunction in disease and by male-specific consequences of gene knockouts in mice, the question of hormone sensitivity was addressed here using a male rat model where prefrontal dopamine levels and related behaviors are also known to be affected. Specifically, quantitative O-methylation and oxidative deamination assays were used to compare the activities of catechol-O-methyltransferase's soluble and membrane-bound isoforms and of monoamine oxidase's A and B isoforms in the pregenual medial prefrontal cortex and dorsal striatum of male rats that were sham operated, gonadectomized or gonadectomized and supplemented with testosterone propionate or with estradiol for 28 days. These studies revealed significant effects of hormone replacement but not gonadectomy on the soluble but not the membrane-bound isorfom of catechol-O-methyltransferase in both striatum and cortex. A significant, cortex-specific testosterone-but not estradiol-attenuated effect (increase) of gonadectomy on monoamine oxidase's A but not B isoform was also observed. Although none of these actions suggest potential roles in the regulation/dysregulation of prefrontal dopamine, the suppressive effects of testosterone on cortical monoamine oxidase-A that were observed could have bearing on the increased incidence of cognitive deficits and symptoms of depression and anxiety that are repeatedly observed in males in conditions of hypogonadalism related to aging, other biological factors or in prostate cancer where androgen deprivation is used as a neoadjuvant treatment.

Meta-analysis of association between genetic variants in COMT and schizophrenia: an update

A common functional polymorphism, Val108/158Met (rs4680), and haplotypes rs737865-rs4680-rs165599 in the Catechol-O-methyltransferase gene (COMT) have been extensively examined for association to schizophrenia; however, results of replication studies have been inconsistent. The aim of this study was to comprehensively evaluate the genetic risk of COMT for schizophrenia. First, we performed a mutation scan to detect the existence of potent functional variants in the 5'-flanking and exon regions. Second, we conducted a gene-based case-control study between tagging single nucleotide polymorphisms (SNPs) in COMT [19 SNPs including six possible functional SNPs (rs2075507, rs737865, rs4680, rs165599, rs165849)] and schizophrenia in large Japanese samples (schizophrenics 1118, controls 1100). Lastly, we carried out a meta-analysis of 5 functional SNPs and haplotypes (rs737865-rs4680-rs165599). No novel functional variant was detected in the mutation scan. There is no association between these tagging SNPs in COMT and Japanese schizophrenia. In this updated meta-analysis, no evidence was found for an association between Val108/158Met polymorphisms, rs6267, rs165599, and haplotypes (rs7378655-rs4680-rs165599) and schizophrenia, although rs2075507 and rs737865 showed trends for significance in allele-wise analyses (P=0.039 in a multiplicative model, P=0.025 in a recessive model for rs2075507, P=0.018 in a dominant model for rs737865, uncorrected). This significance did not remain, however, after correcting the P-values using a false discovery rate controlling procedure. Our results suggest that the COMT is unlikely to contribute to susceptibility to schizophrenia.

Psychiatric comorbidities and schizophrenia

Psychiatric comorbidities are common among patients with schizophrenia. Substance abuse comorbidity predominates. Anxiety and depressive symptoms are also very common throughout the course of illness, with an estimated prevalence of 15% for panic disorder, 29% for posttraumatic stress disorder, and 23% for obsessive-compulsive disorder. It is estimated that comorbid depression occurs in 50% of patients, and perhaps (conservatively) 47% of patients also have a lifetime diagnosis of comorbid substance abuse. This article chronicles these associations, examining whether these comorbidities are "more than chance" and might represent (distinct) phenotypes of schizophrenia. Among the anxiety disorders, the evidence at present is most abundant for an association with obsessive-compulsive disorder. Additional studies in newly diagnosed antipsychotic-naive patients and their first-degree relatives and searches for genetic and environmental risk factors are needed to replicate preliminary findings and further investigate these associations.

Catechol-O-methyltransferase (COMT): a gene contributing to sex differences in brain function, and to sexual dimorphism in the predisposition to psychiatric disorders

Sex differences in the genetic epidemiology and clinical features of psychiatric disorders are well recognized, but the individual genes contributing to these effects have rarely been identified. Catechol-O-methyltransferase (COMT), which metabolizes catechol compounds, notably dopamine, is a leading candidate. COMT enzyme activity, and the neurochemistry and behavior of COMT null mice, are both markedly sexually dimorphic. Genetic associations between COMT and various psychiatric phenotypes frequently show differences between men and women. Many of these differences are unconfirmed or minor, but some appear to be of reasonable robustness and magnitude; eg the functional Val(158)Met polymorphism in COMT is associated with obsessive-compulsive disorder in men, with anxiety phenotypes in women, and has a greater impact on cognitive function in boys than girls. Sex-specific effects of COMT are usually attributed to transcriptional regulation by estrogens; however, additional mechanisms are likely to be at least as important. Here we review the evidence for a sexually dimorphic influence of COMT upon psychiatric phenotypes, and discuss its potential basis. We conclude that despite the evidence being incomplete, and lacking a unifying explanation, there are accumulating and in places compelling data showing that COMT differentially impacts on brain function and dysfunction in men and women. Since sex differences in the genetic architecture of quantitative traits are the rule not the exception, we anticipate that additional evidence will emerge for sexual dimorphisms, not only in COMT but also in many other autosomal genes.

Neurobiology confirms psychopathology. On the antagonism of psychosis and obsessive-compulsive syndromes

BACKGROUND

Psychopathological concepts of the 19th and early 20th century postulated an antagonism between psychotic and obsessive-compulsive disorders, assuming obsessions and compulsions to have protective effects on psychotic disintegration. Although both disorders have been subject to intense multimodal research, their pathogeneses are yet to be fully understood.

METHODS

Here, we discuss recent neurobiological findings pointing towards opposite directions which are strongly reminiscent of the historical psychopathological antagonism.

RESULTS

Obsessive-compulsive syndromes (OCS) are efficiently treated with serotonergic substances, while on the other hand modern antipsychotic drugs exert antiserotonergic effects. Especially these atypical antipsychotic substances, however, were found to involve the risk of inducing second-onset OCS. Dopamine antagonists are potent antipsychotic substances, whereas the partial dopamine agonist aripiprazole has been associated with an antiobsessive potency. Within the glutamatergic system, reduced NMDA-dependent glutamatergic neurotransmission is discussed to be one major pathomechanism of psychotic disorders, whilst NMDA antagonists have proven to be effective in improving treatment-resistant OCS. While neurogenetic findings seem to separate the populations in heterogeneous samples, detailed neuroimaging studies suggest that both disorders affect similar neurocircuits in different manners.

CONCLUSIONS

With regard to these findings, future research on schizo-obsessive syndromes will have to be multimodal, integrating psychopathology, neuropsychology, functional imaging, neurogenetics and psychopharmacology. Prospective trials involving these methods might be able to elucidate the dysbalances of neurotransmission and to locate the neuroanatomical and neuropsychological correlates. In particular, this might contribute to defining schizophrenic patients at risk for developing second-onset OCS and to evaluating new treatment strategies in patients suffering from both psychosis and OCS.

The met(158) allele of catechol-O-methyltransferase (COMT) is associated with obsessive-compulsive disorder in men: case-control study and meta-analysis

Existing data suggest a genetic association between the met(158) allele of catechol-O-methyltransferase (COMT) and obsessive-compulsive disorder (OCD). However, the results are inconclusive and complicated by possible gender differences. We sought to resolve the question in two ways. First, we carried out a new case-control study in 87 adults with OCD and 327 healthy comparison subjects. The study replicated reports of an increased met(158) allele frequency in men with OCD (odds ratio (OR)=1.91, 95% confidence interval (CI) 1.07-3.40, P=0.026), with no effect in women (OR=1.13, 95% CI 0.74-1.72, P=0.56). Second, we performed a meta-analysis of all published case-control data (n=1908 subjects). This revealed an association of COMT met(158) with OCD (OR=1.23, 95% CI 1.06-1.42, P=0.005) and an interaction with gender (z=4.27, P<0.0001). The association between COMT met(158) and OCD was present in men (OR=1.88, 95% CI 1.45-2.44, P<0.001) but not in women (OR=0.98, 95% CI 0.78-1.22, P=0.83). We conclude that COMT may play a role in the genetic aetiology of OCD in men. The biological plausibility of the association is increased by the functionality of the val(158)met polymorphism in terms of its effect on COMT enzyme activity, and by the role of COMT in cortical dopamine signalling and information processing. The finding also extends the evidence for sexual dimorphism in COMT and in OCD.

The catechol-O-methyl transferase (COMT) gene as a candidate for psychiatric phenotypes: evidence and lessons

The enzyme catechol-O-methyl transferase (COMT), identified in the 1950s, is involved in catabolism of monoamines that are influenced by psychotropic medications, including neuroleptics and antidepressants. The COMT gene lies in a chromosomal region of interest for psychosis and bipolar spectrum disorder and a common polymorphism within the gene alters the activity of the enzyme. As a consequence, COMT has been one of the most studied genes for psychosis. On the basis of prior probabilities it would seem surprising if functional variation at COMT did not have some influence either on susceptibility to psychiatric phenotypes, modification of the course of illness or moderation of response to treatment. There is now robust evidence that variation at COMT influences frontal lobe function. However, despite considerable research effort, it has not proved straightforward to demonstrate and characterise a clear relationship between genetic variation at COMT and psychiatric phenotypes. It is of course, possible that COMT will turn out to be an unusually intractable case but it seems more likely that the experiences with this gene will provide a foretaste of the complexity of genotype-phenotype relationships that will be found for psychiatric traits. In this review, we consider the current state of evidence and the implications both for further studies of COMT and more generally for studies of other genes.

Estudos de associação entre transtorno obsessivo-compulsivo e genes candidatos: uma revisão

OBJETIVO: Nos últimos anos, o papel dos genes dos sistemas serotoninérgicos e dopaminérgicos tem sido sistematicamente investigado em pacientes com transtorno obsessivo-compulsivo (TOC), uma vez que esses neurotransmissores apresentam uma provável implicação na fisiopatologia do TOC. Este artigo objetiva revisar os principais resultados de estudos de associação entre genes candidatos e TOC. MÉTODOS: Revisão da literatura na base de dados Medline até agosto de 2006, utilizando as palavras-chave obsessive-compulsive disorder (OCD) e/ou gene(s), polymorphism(s), genetics. RESULTADOS: Inúmeros estudos têm apresentado resultados negativos ao compararem pacientes com TOC e controles, entretanto resultados positivos têm sido observados em pacientes com TOC com características clínicas particulares (sexo, idade de início, dimensão ou gravidade dos sintomas obsessivos ou compulsivos e presença de tiques). CONCLUSÃO: Para garantir a continuidade do avanço de estudos genéticos, é necessária a identificação de subgrupos homogêneos de pacientes com TOC. Diante desses grupos, será possível delinear endofenótipos confiáveis que permitam explorar de forma mais específica a contribuição dos diferentes genes na patogênese da doença.