Differences in MB-COMT DNA methylation in monozygotic twins on phenotypic indicators of impulsivity

Epigenetic modifications of the membrane bound catechol-O-methyltransferase (MB-COMT) gene may affect the enzymatic degradation of dopamine, and consequently, human behavior. This study investigated the association between membrane bound catechol-O-methyltransferase DNA methylation (DNAm) differences in 92 monozygotic (MZ) twins with phenotypic manifestations of cognitive, behavioral, and personality indicators associated with reward-related behaviors and lack of control. We used pyrosequencing to determine DNAm of the regulatory region of membrane bound catechol-O-methyltransferase in saliva DNA. Results of intrapair differences in the percentage of membrane bound catechol-O-methyltransferase DNAm at each of five CpG sites show that there are associations between phenotypic indicators of lack of control and membrane bound catechol-O-methyltransferase DNAm differences on CpG1, CpG2 and CpG4, suggesting the common epigenetic patterns for personality traits, cognitive functions, and risk behaviors.

Cataloging recent advances in epigenetic alterations in major mental disorders and autism

During the last two decades, diverse epigenetic modifications including DNA methylation, histone modifications, RNA editing and miRNA dysregulation have been associated with psychiatric disorders. A few years ago, in a review we outlined the most common epigenetic alterations in major psychiatric disorders (e.g., aberrant DNA methylation of DTNBP1, HTR2A, RELN, MB-COMT and PPP3CC, and increased expression of miR-34a and miR-181b). Recent follow-up studies have uncovered other DNA methylation aberrations affecting several genes in mental disorders, in addition to dysregulation of many miRNAs. Here, we provide an update on new epigenetic findings and highlight potential origin of the diversity and inconsistencies, focusing on drug effects, tissue/cell specificity of epigenetic landscape and discuss shortcomings of the current diagnostic criteria in mental disorders.

Delayed O-methylation of l-DOPA in MB-COMT-deficient mice after oral administration of l-DOPA and carbidopa

1. Catechol-O-methyltransferase (COMT) is involved in the O-methylation of l-DOPA, dopamine, and other catechols. The enzyme is expressed in two isoforms: soluble (S-COMT), which resides in the cytoplasm, and membrane-bound (MB-COMT), which is anchored to intracellular membranes. 2. To obtain specific information on the functions of COMT isoforms, we studied how a complete MB-COMT deficiency affects the total COMT activity in the body, peripheral l-DOPA levels, and metabolism after l-DOPA (10 mg kg^-1) plus carbidopa (30 mg kg^-1) administration by gastric tube in wild-type (WT) and MB-COMT-deficient mice. l-DOPA and 3-O-methyl-l-DOPA (3-OMD) levels were assayed in plasma, duodenum, and liver. 3. We showed that the selective lack of MB-COMT did not alter the total COMT activity, COMT enzyme kinetics, l-DOPA levels, or the total O-methylation of l-DOPA but delayed production of 3-OMD in plasma and peripheral tissues.

Methamphetamine-induced psychosis is associated with DNA hypomethylation and increased expression of AKT1 and key dopaminergic genes

Methamphetamine, one of the most frequently used illicit drugs worldwide, can induce psychosis in a large fraction of abusers and it is becoming a major problem for the health care institutions. There is some evidence that genetic and epigenetic factors may play roles in methamphetamine psychosis. In this study, we examined methamphetamine-induced epigenetic and expression changes of several key genes involved in psychosis. RNA and DNA extracted from the saliva samples of patients with methamphetamine dependency with and without psychosis as well as control subjects (each group 25) were analyzed for expression and promoter DNA methylation status of DRD1, DRD2, DRD3, DRD4, MB-COMT, GAD1, and AKT1 using qRT-PCR and q-MSP, respectively. We found statistically significant DNA hypomethylation of the promoter regions of DRD3 (P = 0.032), DRD4 (P = 0.05), MB-COMT (P = 0.009), and AKT1 (P = 0.0008) associated with increased expression of the corresponding genes in patients with methamphetamine psychosis (P = 0.022, P = 0.034, P = 0.035, P = 0.038, respectively), and to a lesser degree in some of the candidate genes in non-psychotic patients versus the control subjects. In general, methamphetamine dependency is associated with reduced DNA methylation and corresponding increase in expression of several key genes involved in the pathogenesis of psychotic disorders. While these epigenetic changes can be useful diagnostic biomarkers for psychosis in methamphetamine abusers, it is also consistent with the use of methyl rich diet for prevention or suppression of psychosis in these patients. However, this needs to be confirmed in future studies. © 2016 Wiley Periodicals, Inc.

Determination of Methylated CpG Sites in the Promoter Region of Catechol-O-Methyltransferase (COMT) and their Involvement in the Etiology of Tobacco Smoking

We previously reported that catechol-O-methyltransferase (COMT) is significantly associated with nicotine dependence (ND) in humans. In this study, we examined whether there exists any difference in the extent of methylation of CpG dinucleotides in the promoter region of COMT in smokers and non-smokers by analyzing the methylation status of cytosines at 33 CpG sites through direct sequencing of bisulfite-treated DNA (N = 50 per group). The cytosine was methylated at 13 of 33 CpG sites, and two of these sites showed significant differences between smokers and matched non-smoker controls. Specifically, in the -193 CpG site, the degree of methylation was 19.1% in smokers and 13.2% in non-smokers (P < 0.01). This finding was confirmed by methylation-specific PCR using an additional 100 smoker and 100 non-smoker control samples, which showed the degree of methylation to be 22.2% in smokers and 18.3% in non-smokers (P < 0.01). For the -39 CpG site, the degree of methylation was 9.2% in smokers, whereas no methylation was found in non-smoker controls. Together, our findings provide the first molecular explanation at the epigenetic level for the association of ND with methylation of the COMT promoter, implying that methylation plays a role in smoking dependence.