Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The enzyme catechol-O-methyltransferase (COMT) has attracted increasing interest regarding a genetic disposition towards schizophrenias and as a modulator of prefrontal brain function. A common SNP in the COMT gene causes a Val to Met transition at AA158/AA108 (Val158Met), resulting in reduced COMT activity in Met allele carriers. An impact of COMT genotype on cognition has been well established; however, the exact nature of this influence has yet to be elucidated. The aim of this study was to determine whether COMT genotype affects an electrophysiological marker of prefrontal activation and neuropsychological frontal lobe measures in schizophrenia. To this end, 56 acutely psychotic in-patients with schizophrenia spectrum disorders were investigated. Patients with the COMT 1947AA (Met/Met) genotype (n=13) were compared to a carefully matched sample of patients with a G1947A (Val/Met) genotype (n=15); matching criteria included patients' age, handedness, gender distribution, diagnosis, and medication status. A small group of six homozygous Val allele carriers was additionally included to allow an assessment of possible gene-dosage effects. P300 amplitudes and latencies, as well as an electrophysiological marker of prefrontal brain function (NoGo-Anteriorization/NGA) and neuropsychological measures (Stroop Test, Verbal Fluency, Trail Making Test) were regarded. Homozygous Met allele carriers had significantly increased NGA values and fronto-central Nogo amplitudes compared to patients with at least one Val allele. They also tended to perform better in the Stroop task, as compared to the matched group of Val/Met patients. These results indicate that COMT genotype exerts a strong impact on prefrontal functioning and executive control in schizophrenia spectrum disorders.
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PMID:Impact of catechol-O-methyltransferase on prefrontal brain functioning in schizophrenia spectrum disorders. 1682 82

Earlier studies with functional imaging in schizophrenia have demonstrated dysfunction of the dorsolateral prefrontal cortex during working memory. Controlling for behavioral performance and for catechol-O-methyltransferase (COMT) Val158Met genotype, we here demonstrate in a functional magnetic resonance imaging paradigm that patients recruit greater neuronal resources in prefrontal cortex during working memory, suggesting that this phenotype is a core functional trait of the disease. We also replicated earlier findings that the Val allele of the COMT polymorphism is associated with greater engagement of the prefrontal cortex.
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PMID:Prefrontal dysfunction in schizophrenia controlling for COMT Val158Met genotype and working memory performance. 1695 45

The variability in phenotypic presentations and the lack of consistency of genetic associations in mental illnesses remain a major challenge in molecular psychiatry. Recently, it has become increasingly clear that altered promoter DNA methylation could play a critical role in mediating differential regulation of genes and in facilitating short-term adaptation in response to the environment. Here, we report the investigation of the differential activity of membrane-bound catechol-O-methyltransferase (MB-COMT) due to altered promoter methylation and the nature of the contribution of COMT Val158Met polymorphism as risk factors for schizophrenia and bipolar disorder by analyzing 115 post-mortem brain samples from the frontal lobe. These studies are the first to reveal that the MB-COMT promoter DNA is frequently hypomethylated in schizophrenia and bipolar disorder patients, compared with the controls (methylation rate: 26 and 29 versus 60%; P=0.004 and 0.008, respectively), particularly in the left frontal lobes (methylation rate: 29 and 30 versus 81%; P=0.003 and 0.002, respectively). Quantitative gene-expression analyses showed a corresponding increase in transcript levels of MB-COMT in schizophrenia and bipolar disorder patients compared with the controls (P=0.02) with an accompanying inverse correlation between MB-COMT and DRD1 expression. Furthermore, there was a tendency for the enrichment of the Val allele of the COMT Val158Met polymorphism with MB-COMT hypomethylation in the patients. These findings suggest that MB-COMT over-expression due to promoter hypomethylation and/or hyperactive allele of COMT may increase dopamine degradation in the frontal lobe providing a molecular basis for the shared symptoms of schizophrenia and bipolar disorder.
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PMID:Hypomethylation of MB-COMT promoter is a major risk factor for schizophrenia and bipolar disorder. 1698 65

Behavioral phenotypes are generally complex, reflecting the action of multiple different genes. Nevertheless, there is growing evidence that key gene variants can alter activity within specific neuronal circuits and, therefore, influence particular cognitive-affective phenomena. One example is the catechol-O-methyltransferase (COMT) gene, which has a common variant at codon 158. Those with valine (Val158) alleles have increased greater COMT activity and lower prefrontal extracellular dopamine compared with those with the methionine (Met158) substitution. Val158 alleles may be associated with an advantage in the processing of aversive stimuli (warrior strategy), while Met158 alleles may be associated with an advantage in memory and attention tasks (worrier strategy). Under conditions of increased dopamine release (eg, stress), individuals with Val158 alleles may have improved dopaminergic transmission and better performance, while individuals with Met158 alleles may have less efficient neurotransmission and worse performance. Some evidence suggests that Val158 alleles are associated with schizophrenia, while Met158 alleles are associated with anxiety.
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PMID:Warriors versus worriers: the role of COMT gene variants. 1700 17

A number of studies have reported an association between catechol-O-methyltransferase (COMT) gene Val158Met polymorphism and neuropsychological traits in patients with schizophrenia, their relatives and healthy controls, with the Met allele carriers performing better on neurocognitive tasks than those with the Val allele. But the association was not confirmed in all studies. The present paper was aimed at further investigation of the COMT gene relationship with some neurocognitive traits, assessing mainly working and verbal memory, and to P300 event-related potentials (auditory oddball). A total sample of 319 individuals, including schizophrenic patients, their relatives and controls, was studied. No significant differences in performance of neurocognitive tasks were found by Val158Met genotypes. An association was observed between the Met/Met genotype and higher amplitude in centro-parietal area in relatives. Factors that could explain the non-replication of previous studies on the COMT gene polymorphism and neurocognitive traits are discussed. We suggest here that (1) Val158Met polymorphism rather exerts a modifying influence on brain activation in general than impacts directly on performance of the particular neurocognitive test, and (2) P300 amplitude seems to be a correlate of this activation reflecting, along with information processing, the subject's affective and personality features.
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PMID:Association study of COMT gene Val158Met polymorphism with auditory P300 and performance on neurocognitive tests in patients with schizophrenia and their relatives. 1707 44

Preliminary evidence suggests that a single nucleotide polymorphism (SNP), the val108/158met SNP, within the gene that codes for catechol-O-methyltransferase (COMT), a key enzyme involved in regulating dopamine (DA) transmission within the prefrontal cortex (PFC), is related to cognitive function in schizophrenia and cognitive improvement with atypical antipsychotic drugs (APDs). Specifically, several studies have identified an association between working memory and executive functions, and COMT val108/158met genotype in schizophrenia; although there have been several negative findings that are likely related to small sample sizes and, possibly, medication status of patients at the time of testing. The association between COMT val108/158met genotype, cognitive function, and cognitive improvement with clozapine was investigated in a relatively large prospective sample of patients with schizophrenia, most of whom were unmedicated at baseline. Patients were genotyped for the COMT val108/158met SNP after completing a cognitive battery consisting of tests of attention, working memory, verbal learning and memory, executive function, and verbal fluency at baseline and after 6 weeks and 6 months of treatment with clozapine. Consistent with several previous studies, an association between COMT genotype and tests of executive function and working memory was identified at baseline. In addition, a novel interaction between genotype and improvement on tests of attention and verbal fluency was identified. Specifically, met homozygous and val/met heterozygous patients demonstrated significantly greater improvement than val homozygous patients following 6 months of treatment with clozapine. The results are discussed in relation to previous cross-sectional studies and prospective investigations of the associations between COMT genotype, cognition, and cognitive improvement with atypical APDs in schizophrenia.
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PMID:COMT val108/158met genotype, cognitive function, and cognitive improvement with clozapine in schizophrenia. 1712 85

Velocardiofacial syndrome is a genetic disorder associated with a microdeletion on the long arm of chromosome 22, and this segment is responsible for coding catechol-O-methyltransferase, an enzyme involved in dopamine degradation. We submit a case of velocardiofacial syndrome and Madelung deformity of the wrists presenting with hallucinatory phenomena associated with opioid exposure. Overactivity of the dopaminergic system has been postulated to cause schizophrenia in this population, and here we speculate that dysregulation of dopamine metabolism may have predisposed our patient to an increased risk of opioid-induced hallucinations. Further research is necessary to explore this relationship.
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PMID:Does dysregulation of catechol-O-methyltransferase predispose to opioid-induced hallucinations? A report of a patient with microdeletion of chromosome 22 and opioid-associated hallucinations. 1724 8

Diverse strands of evidence suggest that schizophrenia is associated with an excess of left and mixed handedness, reflecting anomalous cerebral lateralization. Genetic studies have indicated a degree of overlap between bipolar disorder (BPD) and schizophrenia. Nevertheless, pattern of handedness and degree of lateralization have not been explicitly tested in BPD. We measured handedness, footedness and relative manual dexterity in a sample of 47 families comprising BPD probands and their bipolar-spectrum and unaffected relatives (N = 240). The BPD I sample (N = 55) was significantly more lateralized on handedness, footedness and relative manual dexterity than their unaffected relatives (N = 66). They were also more lateralized than their relatives with other psychiatric diagnoses. No evidence of excess mixed handedness or footedness was observed in the BPD I sample. We raise the possibility that schizophrenia and BPD I differ in that disproportionate left-hemisphere dominance in BPD I is associated with right-hemisphere dysfunction leading to deficits in emotional regulation. Given our results, we hypothesized that degree of lateralization may be a phenotypic marker or endophenotype for BPD I. We therefore conducted a family-based genetic association analysis with this quantitative trait. Relative hand skill was significantly associated with a functional variant in the catechol-O-methyltransferase gene. We speculate that this polymorphism may influence brain lateralization.
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PMID:Lateralization of hand skill in bipolar affective disorder. 1730 60

The catechol-O-methyltransferase (COMT) Val(158)Met polymorphism is hypothesized to affect executive function in patient and control populations. Studies inconsistently report better performance on the Wisconsin Card Sort Test (WCST) in individuals with one or more Met alleles. We conducted a meta-analysis of studies published until August 2006 that reported WCST perseverative errors from healthy volunteers or patients with schizophrenia-spectrum disorders. Twelve studies met inclusion criteria (total n=1910) providing 10 samples each of patients and controls. In healthy controls, individuals with the Met/Met genotype performed better than those with the Val/Val genotype (d=0.29; 95% confidence interval (CI) 0.02-0.55; P=0.03), but this was not supported in the patient sample (d=-0.07; 95% CI -0.40 to 0.26; P=0.68). Post hoc analyses suggested that Val and Met alleles are codominant in their effects on cognition. Effect size was greater in studies published at an earlier date and may also be larger in non-Caucasian samples. Gender did not affect the results. There was no evidence of publication bias. We conclude that there is small but significant relationship between Val(158)Met genotype and executive function in healthy individuals but not in schizophrenia.
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PMID:Effects of the catechol-O-methyltransferase Val158Met polymorphism on executive function: a meta-analysis of the Wisconsin Card Sort Test in schizophrenia and healthy controls. 1732 17

Genetic variation in the catechol-O-methyltransferase (COMT) gene may influence the susceptibility to schizophrenia and the response to neuroleptic treatment. The authors tested for an association between a COMT haplotype and schizophrenia-spectrum disorders and for an eventual influence of a specific COMT genotype in the clinical outcome and in the response to treatment. The genotypes for single nucleotide polymorphisms rs737865, rs4633, rs6267, rs4680 (Val 158 Met) and rs165599 were determined in 207 patients with schizophrenia-spectrum disorders and 204 paired controls. Statistical tests for linkage disequilibrium and for case-control differences in haplotype frequencies were performed using log-linear modelling embedded within the expectation-maximization algorithm. P-values based on permutations were calculated using the software UNPHASED, and odds ratios were estimated using the SHEsis platform. The response to neuroleptic treatment was assessed by the Global Assessment of Functioning scale and the severity of psychotic symptoms by the positive and negative syndrome scale (PANSS) scale. The overall disease status was significantly associated with the T-G (Val) diplotype for rs4633-rs4680 (P=0.0049). A significant association was observed between schizophrenia, but not other related disorders, and genotypes GG (Val/Val) for rs4680 and TT for rs4633. Val/Val patients with schizophrenia showed a higher severity of the psychotic symptoms and a worse response to the neuroleptic treatment. COMT genetic variation seems to be involved in the psychotic symptomatology of the schizophrenia-spectrum disorders and specifically in the narrow schizophrenia phenotype. Our results show an influence of the Val 158 Met polymorphism on the severity of psychotic symptoms and on the response to treatment.
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PMID:Clinical involvement of catechol-O-methyltransferase polymorphisms in schizophrenia spectrum disorders: influence on the severity of psychotic symptoms and on the response to neuroleptic treatment. 1736 61


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