HapMap tag-SNP analysis confirms a role for COMT in schizophrenia risk and reveals a novel association

The inconsistent mediating effect of catechol O methyl transferase Val158Met polymorphism on the sex difference of cognitive impairment in schizophrenia patients

OBJECTIVE

Schizophrenia is a multifaceted mental disorder characterized by heterogeneous positive/negative symptoms and cognitive deficits. Sex differences have been reported in various aspects of the disease. However, the underlying genetic reasons remain unelucidated. Recent studies show that the influence of COMT Val158Met (rs4680) variation is sexually dimorphic. Thus, this study aims to explore whether there is an effect of the interaction between COMT Val158Met (rs4680) polymorphism and sex on patients' clinical characteristics and cognitive function.

MATERIALS AND METHODS

We recruited 367 in patients with chronic schizophrenia (246 males and 121 females) and 419 healthy controls (172 males and 247 females). The cognitive performance was assessed by Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and the COMT Val158Met (rs4680) polymorphism is genotyped. The psychopathological symptoms of the patients were assessed by the Positive and Negative Syndrome Scale (PANSS).

RESULTS

We find that male patients had a significantly higher proportion of carrying the Val allele and Val/Val carriers exhibited more severe positive symptoms and cognitive impairment than Met carriers. COMT Val158Met (rs4680) polymorphism inconsistently mediated the relationship between sex and cognitive performance in schizophrenia patients.

CONCLUSION

These findings suggest that COMT Val158Met (rs4680) polymorphism is associated with the risk and severity of schizophrenia in a sexually dimorphic way and contributes more to the clinical symptoms and cognitive impairment in male patients with schizophrenia.

Schizophrenia spectrum and other psychotic disorders

Since its earliest conceptualization, schizophrenia has been considered a disorder of "young men." Contemporary research suggests that there are sex differences in schizophrenia that are both transdiagnostic and representative of general sex/gender differences across the psychopathology spectrum. This chapter selectively summarizes representative sex/gender differences in clinical expression, epidemiology, risk factors, treatment, as well as course and outcome in schizophrenia. The consistent sex differences found, such as onset age, generic brain anomalies, and hormonal involvement, are not specific to schizophrenia or necessarily to psychopathology. It is suggested that in working with those diagnosed as meeting the current criteria for schizophrenia, clinicians adopt a transdiagnostic framework informed by sex and gender role processes.

Depressive symptoms in schizophrenia and dopamine and serotonin gene polymorphisms

Although depressive symptoms seem to be frequent in schizophrenia they have received significantly less attention than other symptom domains. As impaired serotonergic and dopaminergic neurotransmission is implicated in the pathogenesis of depression and schizophrenia this study sought to investigate the putative association between several functional gene polymorphisms (SERT 5-HTTLPR, MAO-A VNTR, COMT Val158Met and DAT VNTR) and schizophrenia. Other objectives of this study were to closely examine schizophrenia symptom domains by performing factor analysis of the two most used instruments in this setting (Positive and negative syndrome scale - PANSS and Calgary depression rating scale - CDSS) and to examine the influence of investigated gene polymorphisms on the schizophrenia symptom domains, focusing on depressive scores. A total of 591 participants were included in the study (300 schizophrenic patients and 291 healthy volunteers). 192 (64%) of schizophrenic patients had significant depressive symptoms. Genotype distribution revealed no significant differences regarding all investigated polymorphisms except the separate gender analysis for MAO-A gene polymorphism which revealed significantly more allele 3 carriers in schizophrenic males. Factor analysis of the PANSS scale revealed the existence of five separate factors (symptom domains), while the CDSS scale revealed two distinct factors. Several investigated gene polymorphisms (mostly SERT and MAO-A, but also COMT) significantly influenced two factors from the PANSS (aggressive/impulsive and negative symptoms) and one from the CDSS scale (suicidality), respectively. Depressive symptoms in schizophrenic patients may be influenced by functional gene polymorphisms, especially those implicated in serotonergic neurotransmission.

Interaction of multiple gene variants and their effects on schizophrenia phenotypes

BACKGROUND

Schizophrenia is a clinically heterogeneous disorder and may be explained by its complex genetic architecture. Many schizophrenia susceptibility genes were identified but the picture remains unclear due to inconsistent or contradictory genetic association studies. This confusion may, in part, be because symptoms result from the combined interaction of many genes and these interacting genes are associated with specific sub-phenotypes of schizophrenia rather than schizophrenia as a whole. This study investigates the relationship between schizophrenia susceptibility genes and schizophrenia sub-phenotypes by identifying multiple gene variant interactions.

MATERIALS AND METHODS

Fifty SNPs from 21 genes were genotyped in 235 Australian participants with schizophrenia screened for various phenotypes. Schizophrenia participants were grouped into relevant phenotype clusters using cluster analysis and normalized phenotype cluster scores were calculated for each patient. The relationship between genotypes and normalized phenotype cluster scores were analyzed by linear regression analysis.

RESULTS

Three phenotype clusters were identified. There was some overlap in symptoms between phenotype clusters, particularly for depression. However, cluster 1 appears to be characterized by speech disorder and affective behavior symptoms, cluster 2 has predominantly hallucination symptoms and cluster 3 has mainly delusion symptoms. Interaction of five SNPs was found to have an effect on cluster 1 symptoms; ten SNPs on cluster 2 symptoms; and eight SNPs on cluster 3 symptoms.

CONCLUSION

The interaction of specific susceptibility genes is likely to lead to specific clinical sub-phenotypes of schizophrenia. Larger patient cohorts with more extensive clinical data will improve the detection of gene interactions and the resultant schizophrenia clinical phenotypes.

Stress, COMT Polymorphisms, and Depressive Symptoms in Older Australian Women: An Exploratory Study

OBJECTIVES

This exploratory study examined the association between exposure to stressful life events, polymorphisms (rs165774 and rs4680) in the catechol-O-methyltransferase (COMT) gene, and risk of depression in women.

MATERIALS AND METHODS

A cross-sectional design gathered information from 150 Australia women, aged 60-70 years, on sociodemographics, stressful life events, and depressive symptoms. Participants also provided buccal cell swabs for genetic analysis.

RESULTS

Among women exposed to stressful life events, the odds of depressive symptoms increased by 18% with each additional exposure (95% confidence interval [95% CI] 1.04-1.33, p = 0.007). Women who carried at least one "A" allele (AA/AG) for both rs165774 and rs4680 single nucleotide polymorphisms were less likely to report depressive symptoms (compared with women with the GG genotype; p = 0.019 and p = 0.037, respectively), although moderation analysis did not support the hypotheses of an interaction with stressful life events (rs165774: odds ratio [OR] = 1.13, 95% CI 0.87-1.46, p = 0.347; rs4680: OR = 1.15, 95% CI 0.91-1.44, p = 0.238).

CONCLUSION

Our research suggests that women with polymorphisms in COMT were less susceptible to depressive symptoms but these polymorphisms do not appear to influence susceptibility to depression in those exposed to life stressors. Further research should consider other genetic variants in catecholamine pathways and their potential impact on women's mental health.

Proinflammatory genotype is associated with the frailty phenotype in the English Longitudinal Study of Ageing

Background

Frailty is a state of increased vulnerability to poor resolution of homeostasis after a stressor event, which increases the risk of adverse outcomes including falls, disability and death. The underlying pathophysiological pathways of frailty are not known but the hypothalamic–pituitary–adrenal axis and heightened chronic systemic inflammation appear to be major contributors.

Methods

We used the English Longitudinal Study of Ageing dataset of 3160 individuals over the age of 50 and assessed their frailty status according to the Fried-criteria. We selected single nucleotide polymorphisms in genes involved in the steroid hormone or inflammatory pathways and performed linear association analysis using age and sex as covariates. To support the biological plausibility of any genetic associations, we selected biomarker levels for further analyses to act as potential endophenotypes of our chosen genetic loci.

Results

The strongest association with frailty was observed in the Tumor Necrosis Factor (TNF) (rs1800629, P = 0.001198, β = 0.0894) and the Protein Tyrosine Phosphatase, Receptor type, J (PTPRJ) (rs1566729, P = 0.001372, β = 0.09397) genes. Rs1800629 was significantly associated with decreased levels of high-density lipoprotein (HDL) (P = 0.00949) and cholesterol levels (P = 0.00315), whereas rs1566729 was associated with increased levels of HDL (P = 0.01943). After correcting for multiple testing none of the associations remained significant.

Conclusions

We provide potential evidence for the involvement of a multifunctional proinflammatory cytokine gene (TNF) in the frailty phenotype. The implication of this gene is further supported by association with the endophenotype biomarker results.

Electronic supplementary material

The online version of this article (doi:10.1007/s40520-015-0419-z) contains supplementary material, which is available to authorized users.

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.

Effect of polymorphisms of three genes mediating monoamine signalling on brain morphometry in schizophrenia and healthy subjects

OBJECTIVE

We examined the effect of risk alleles of polymorphisms of three schizophrenia risk genes that mediate monoamine signalling in the brain on regional brain volumes of schizophrenia and healthy control subjects. The risk alleles and the gene polymorphisms studied were: Val allele of catechol o-methyltransferase (COMT) rs4680 polymorphism; short allele of 5-hydroxy tryptamine transporter linked polymorphic region (5HTTLPR) polymorphism; and T allele of 5-hydroxy tryptamine 2A (5HT2A) rs6314 polymorphism.

METHODS

The study was carried out on patients with recent onset schizophrenia (n=41) recruited from the outpatient department of National Institute of Mental Health and Neurosciences, Bangalore, India and healthy control subjects (n=39), belonging to South Indian Dravidian ethnicity. Individual and additive effects of risk alleles of the above gene polymorphisms on brain morphometry were explored using voxel-based morphometry.

RESULTS

Irrespective of phenotypes, individuals with the risk allele T of the rs6314 polymorphism of 5HT2A gene showed greater (at cluster-extent equivalent to family wise error-correction [FWEc] p<0.05) regional brain volumes in the left inferior temporal and left inferior occipital gyri. Those with the risk alleles of the other two polymorphisms showed a trend (at p<0.001, uncorrected) towards lower regional brain volumes. A trend (at p<0.001, uncorrected) towards additive effects of the above 3 risk alleles (subjects with 2 or 3 risk alleles vs. those with 1 or no risk alleles) on brain morphology was also noted.

CONCLUSIONS

The findings of the present study have implications in understanding the role of individual and additive effects of genetic variants in mediating regional brain morphometry in health and disease.

Association of histamine N-methyltransferase Thr105Ile polymorphism with Parkinson's disease and schizophrenia in Han Chinese: a case-control study

Parkinson’s disease (PD) and schizophrenia (SCZ) are frequent central nervous disorders that have unclear etiologies but that show similarities in their pathogenesis. Since elevated histamine levels in the brain have been associated with PD and SCZ, we wanted to explore whether the Thr105Ile substitution in the histamine N-methyltransferase gene (HNMT-Thr105Ile), which impairs histamine degradation, is associated with either disease. We used the ligase detection reaction to genotype a case-control cohort of Han Chinese patients with PD or SCZ and healthy controls at the HNMT-Thr105Ile locus. The Ile allele was associated with reduced risk of PD (OR 0.516, 95%CI 0.318 to 0.838, p = 0.007) and of SCZ (OR 0.499, 95%CI 0.288 to 0.865, p = 0.011). Genotype frequencies and minor allele frequencies were similar between patients and controls when we compared males with females or early-onset patients with late-onset ones. Genotype and allele frequencies were not significantly different between PD patients with dyskinesia and PD patients without dyskinesia. Our results suggest that the heterozygous Thr/Ile genotype at the HNMT-Thr105Ile locus and the minor Ile105 allele protect against PD and SCZ in Han Chinese.

Subclinical psychotic experiences in healthy young adults: associations with stress and genetic predisposition

Stress has been identified as a common trigger for psychosis. Dopamine pathways are suggested to be affected by chronic and severe stress and to play an important role in psychosis. This pilot study investigates the potential relationship of stress and psychosis in subclinical psychotic experiences. It was hypothesized that single-nucleotide polymorphisms (SNPs) previously found to be associated with psychiatric disorders would be associated with both stress and subclinical psychotic experiences. University students (N=182) were genotyped for 17 SNPs across 11 genes. Higher stress reporting was associated with rs4680 COMT, rs13211507 HLA region, and rs13107325 SLC39A8. Reports of higher subclinical psychotic experiences were associated with DRD2 SNPs rs17601612 and rs658986 and an AKT1 SNP rs2494732. Replication studies are recommended to further pursue this line of research for identification of markers of psychosis for early diagnosis and intervention.

Polymorphisms in genes implicated in dopamine, serotonin and noradrenalin metabolism suggest association with cerebrospinal fluid monoamine metabolite concentrations in psychosis

BACKGROUND

Homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) are the major monoamine metabolites in the central nervous system (CNS). Their cerebrospinal fluid (CSF) concentrations, reflecting the monoamine turnover rates in CNS, are partially under genetic influence and have been associated with schizophrenia. We have hypothesized that CSF monoamine metabolite concentrations represent intermediate steps between single nucleotide polymorphisms (SNPs) in genes implicated in monoaminergic pathways and psychosis.

METHODS

We have searched for association between 119 SNPs in genes implicated in monoaminergic pathways [tryptophan hydroxylase 1 (TPH1), TPH2, tyrosine hydroxylase (TH), DOPA decarboxylase (DDC), dopamine beta-hydroxylase (DBH), catechol-O-methyltransferase (COMT), monoamine oxidase A (MAOA) and MAOB] and monoamine metabolite concentrations in CSF in 74 patients with psychotic disorder.

RESULTS

There were 42 nominally significant associations between SNPs and CSF monoamine metabolite concentrations, which exceeded the expected number (20) of nominal associations given the total number of tests performed. The strongest association (p = 0.0004) was found between MAOB rs5905512, a SNP previously reported to be associated with schizophrenia in men, and MHPG concentrations in men with psychotic disorder. Further analyses in 111 healthy individuals revealed that 41 of the 42 nominal associations were restricted to patients with psychosis and were absent in healthy controls.

CONCLUSIONS

The present study suggests that altered monoamine turnover rates in CNS reflect intermediate steps in the associations between SNPs and psychosis.

Gene-sex interactions in schizophrenia: focus on dopamine neurotransmission

Schizophrenia is a severe mental disorder, with a highly complex and heterogenous clinical presentation. Our current perspectives posit that the pathogenic mechanisms of this illness lie in complex arrays of gene × environment interactions. Furthermore, several findings indicate that males have a higher susceptibility for schizophrenia, with earlier age of onset and overall poorer clinical prognosis. Based on these premises, several authors have recently begun exploring the possibility that the greater schizophrenia vulnerability in males may reflect specific gene × sex (G×S) interactions. Our knowledge on such G×S interactions in schizophrenia is still rudimentary; nevertheless, the bulk of preclinical evidence suggests that the molecular mechanisms for such interactions are likely contributed by the neurobiological effects of sex steroids on dopamine (DA) neurotransmission. Accordingly, several recent studies suggest a gender-specific association of certain DAergic genes with schizophrenia. These G×S interactions have been particularly documented for catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO), the main enzymes catalyzing DA metabolism. In the present review, we will outline the current evidence on the interactions of DA-related genes and sex-related factors, and discuss the potential molecular substrates that may mediate their cooperative actions in schizophrenia pathogenesis.

Genome-wide DNA methylation analysis of human brain tissue from schizophrenia patients

Recent studies suggest that genetic and environmental factors do not account for all the schizophrenia risk, and epigenetics also has a role in disease susceptibility. DNA methylation is a heritable epigenetic modification that can regulate gene expression. Genome-wide DNA methylation analysis was performed on post-mortem human brain tissue from 24 patients with schizophrenia and 24 unaffected controls. DNA methylation was assessed at over 485,000 CpG sites using the Illumina Infinium HumanMethylation450 Bead Chip. After adjusting for age and post-mortem interval, 4641 probes corresponding to 2929 unique genes were found to be differentially methylated. Of those genes, 1291 were located in a CpG island and 817 were in a promoter region. These include NOS1, AKT1, DTNBP1, DNMT1, PPP3CC and SOX10, which have previously been associated with schizophrenia. More than 100 of these genes overlap with a previous DNA methylation study of peripheral blood from schizophrenia patients in which 27,000 CpG sites were analysed. Unsupervised clustering analysis of the top 3000 most variable probes revealed two distinct groups with significantly more people with schizophrenia in cluster one compared with controls (P=1.74 × 10(-4)). The first cluster composed of 88% of patients with schizophrenia and only 12% controls, whereas the second cluster composed of 27% of patients with schizophrenia and 73% controls. These results strongly suggest that differential DNA methylation is important in schizophrenia etiology and add support for the use of DNA methylation profiles as a future prognostic indicator of schizophrenia.

No association between catechol-o-methyltransferase Val108/158Met polymorphism and schizophrenia or its clinical symptomatology in a Mexican population

The gene coding for catecol-o-methyltransferase (COMT), participant in the metabolism of catecholamines, has long been implicated as a candidate gene for schizophrenia. We determined the relation of the COMT Val108/158Met polymorphism with schizophrenia or its symptomatology (negative, disorganized and psychotic dimension). We conducted a case–control study comprising 186 patients with schizophrenia and 247 controls. The diagnosis of schizophrenia was established using the DSM-IV criteria for this illness. The clinical symptomatology was assessed through the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms. No significant differences were found in the distribution of alleles (χ2 = 0.01, df = 1, p = 0.90) or genotypes (χ2 = 1.66, df = 2, p = 0.43) between schizophrenic patients and the control group. Multivariate analysis showed that the COMT Val108/158Met polymorphism has no influence in the clinical symptomatology of schizophrenia. Our results showed no association between COMT Val108/158Met and schizophrenia or evidence for an association between COMT and the clinical symptomatology of this illness. This suggests that the COMT gene may not contribute to the risk for schizophrenia among the Mexican population.

A novel SNP in COMT is associated with alcohol dependence but not opiate or nicotine dependence: a case control study

BACKGROUND

It is well established that COMT is a strong candidate gene for substance use disorder and schizophrenia. Recently we identified two SNPs in COMT (rs4680 and rs165774) that are associated with schizophrenia in an Australian cohort. Individuals with schizophrenia were more than twice as likely to carry the GG genotype compared to the AA genotype for both the rs165774 and rs4680 SNPs. Association of both rs4680 and rs165774 with substance dependence, a common comorbidity of schizophrenia has not been investigated.

METHODS

To determine whether COMT is important in substance dependence, rs165774 and rs4680 were genotyped and haplotyped in patients with nicotine, alcohol and opiate dependence.

RESULTS

The rs165774 SNP was associated with alcohol dependence. However, it was not associated with nicotine or opiate dependence. Individuals with alcohol dependence were more than twice as likely to carry the GG or AG genotypes compared to the AA genotype, indicating a dominant mode of inheritance. The rs4680 SNP showed a weak association with alcohol dependence at the allele level that did not reach significance at the genotype level but it was not associated with nicotine or opiate dependence. Analysis of rs165774/rs4680 haplotypes also revealed association with alcohol dependence with the G/G haplotype being almost 1.5 times more common in alcohol-dependent cases.

CONCLUSIONS

Our study provides further support for the importance of the COMT in alcohol dependence in addition to schizophrenia. It is possible that the rs165774 SNP, in combination with rs4680, results in a common molecular variant of COMT that contributes to schizophrenia and alcohol dependence susceptibility. This is potentially important for future studies of comorbidity. As our participant numbers are limited our observations should be viewed with caution until they are independently replicated.