Erythrocyte catechol O-methyltransferase activity in schizophrenia: analysis of family data

Variation in catechol-o-methyltransferase val158 met genotype associated with schizotypy but not cognition: a population study in 543 young men

BACKGROUND

Increased catechol-O-methyltransferase activity associated with variation in catechol-O-methyltransferase valine158 methionine genotypes may result in reduced dopamine neurotransmission in the prefrontal cortex and thus contribute to the poor performance of frontally mediated cognitive tasks and the occurrence of associated negative symptoms observed in patients with schizophrenia; however, reported associations between catechol-O-methyltransferase valine158 methionine genotypes and measures of cognition have not been consistent.

METHODS

Catechol-O-methyltransferase genotyping, measures of schizotypy, cognitive measures of memory and attention, as well as the antisaccade eye movement task, a measure sensitive to prefrontal cortical function, were obtained in a sample of 543 young men representative for that age group (mean age 21 years).

RESULTS

None of the cognitive measures was associated with catechol-O-methyltransferase valine158 methionine genotypes; however, there was an effect of high-activity allele loading on schizotypy, in particular the negative and disorganization dimensions.

CONCLUSIONS

Previously reported inconsistencies in the relationship between catechol-O-methyltransferase valine158 methionine genotypes and cognition were not resolved; however, catechol-O-methyltransferase genotype may affect expression of negative schizotypy by direct or indirect effects on central dopamine neurotransmitter signaling.

Higher scores of self reported schizotypy in healthy young males carrying the COMT high activity allele

The gene for COMT is located on chromosome 22q11, an area that has been implicated in the pathogenesis of schizophrenia through linkage studies and through the detection of deletions in schizophrenics and velocardiofacial syndrome patients that often present psychotic symptomatology. Additionally catechol-O-methyl transferase activity has been found increased in schizophrenia and a functional polymorphism in the COMT gene itself has been associated with the disease, as well as with aggression in patients. We tested the hypothesis that COMT genotype for the functional Val158Met might contribute to the variance of self reported schizotypy and aggression scores in the normal population. We genotyped 379 healthy 18- to 24-year-old male individuals who had completed the PAS, SPQ and AQ questionnaires. Our results showed that self-reported schizotypy scores in both questionnaires were significantly related to COMT genotype (P = 0.028 for the PAS and P = 0.015 for the SPQ) with individuals homozygous for the high activity allele showing the highest scores. No significant differences were detected for AQ scores. We conclude that the COMT genotype for the functional Val158Met polymorphism is correlated to self-reported schizotypy in healthy males. This finding is in the same direction as reported findings on schizophrenia and it adds to the list of evidence that COMT or a nearby gene in linkage disequilibrium is involved in the pathogenesis of the disease.

Family-based linkage disequilibrium mapping using SNP marker haplotypes: application to a potential locus for schizophrenia at chromosome 22q11

Family-based linkage disequilibrium mapping using SNP markers is expected to be a major route to the identification of susceptibility alleles for complex diseases. However there are a number of methodological issues yet to be resolved, including the handling of extended haplotype data and analysis of haplotype transmission in sib-pair or family trio samples. In the present study, we have analysed two dinucleotide repeat and six SNP markers at the COMT locus at chromosome 22q11, a region implicated in psychosis, for transmission distortion in 198 Chinese schizophrenic family trios. When individual markers were analysed using the TDT, two showed modest evidence of transmission distortion (186C/T, P = 0.04; Val158Met, P = 0.01). Using haplotypes of paired markers analysed by the program TRANSMIT, the most significant P value was 0.001, for the Met158Val and 900ins/delC polymorphisms in the COMT gene. The global P value for the haplotypes of all six SNP markers tested was 0.004, largely a result of the excess transmission of two extended haplotypes which differed at the marker 408C/G. The exclusion of this marker from the analysis gave a global P value of 0.002 and produced a five marker haplotype system which was significant at P = 0.0006. This haplotype consisted of the alleles -287G:186C:Val158:900insC:ARVCF930C, which may represent a background haplotype for the transmission of a schizophrenia susceptibility allele at chromosome 22q11. Our results support the hypotheses that either COMT is itself a susceptibility gene, or more likely that this region of chromosome 22 contains a susceptibility gene that is in linkage disequilibrium with COMT alleles. Molecular Psychiatry (2000) 5, 77-84.

Identification of sequence variants and analysis of the role of the catechol-O-methyl-transferase gene in schizophrenia susceptibility

BACKGROUND

Deletions of 1.5-2 MB of chromosome 22q11 have been previously associated with schizophrenia. The deleted region includes proximally the region harboring genes involved in DiGeorge and velocardiofacial syndromes. Distally, it includes the gene for catechol-O-methyl-transferase (COMT), an enzyme that catalyzes the O-methylation of catecholamine neurotransmitters, including dopamine, and which therefore is considered a candidate gene for schizophrenia.

METHODS

We address the issue of a direct involvement of the COMT gene in the development of schizophrenia by employing the first extensive mutational analysis of this gene in a sample of 157 schizophrenia patients and 129 healthy controls, using single-strand conformation polymorphism and chemical cleavage methodologies.

RESULTS

No mutations were found, but several sequence variants were identified, including the genetic polymorphism that underlies the high/low activity of the enzyme (a Val158-->Met change, which results in the creation of an NlaIII restriction site in the low-activity allele). The distribution of the NlaIII genotypes among subsets of schizophrenia patients was analyzed.

CONCLUSIONS

The results presented here argue against a major role of COMT in schizophrenia in general (although a minor effect could not be excluded) and represent a first step toward a more refined delineation of the phenotype/genotype relationship between 22q11 microdeletions and schizophrenia susceptibility.

Association study of a functional catechol-O-methyltransferase gene polymorphism in Japanese schizophrenics

Catechol-O-methyltransferase (COMT) is an enzyme which inactivates catecholamine neurotransmitters by methylation, and is considered a candidate for involvement in schizophrenia. A functional COMT gene polymorphism influencing the enzyme activities, the high activity (val-108) and the low activity allele (met-108), was recently confirmed. We investigated a genetic association between schizophrenia and the COMT gene polymorphism in 150 Japanese schizophrenics and controls. We detected the low activity met-108 allele more frequently in schizophrenics than in the controls, and found that subjects sharing the met-108 allele (val/met and met/met) are significantly more common in the patients than in the controls. The results suggest that the low activity met-108 allele may be involved in susceptibility for schizophrenia.

Genetics of schizophrenia: II. Vulnerability traits and gene markers

The author reviews research strategies for identifying biological vulnerability traits and gene markers. The application of these methods to schizophrenia are discussed. He concludes that, based on the available evidence, none of the proposed biological traits qualifies as a major factor in the genetic susceptibility to schizophrenia. Some of these traits (such as attentional, neurophysiological, and brain morphology measures) appear promising, but the data are inadequate to arrive at a firm conclusion. Studies with gene markers have not produced consistent results. The author presents the methodological issues that concern this area of research and offers recommendations for future studies.

beta-phenylethylamine effect on brain and blood catechol-O-methyltransferase activity

A significant decrease in catechol-o-methyltransferase (COMT) activity has been found in the striatum (77% of control) and hippocampus (63% of control) of gerbils treated with daily injections of beta-phenylethylamine (50 mg/kg) for 10 days. This treatment group also exhibited increased (204% above control) COMT activity in a lysed red blood cell preparation. There were no changes in COMT activity in groups receiving 10 mg/kg beta-phenylethylamine or haloperidol (0.5 mg/kg). In vitro beta-phenylethylamine has no demonstrable effect on COMT activity.