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Background: The association between childhood maltreatment and subsequent aggressive behaviour is modified by monoamine oxidase A (MAOA) functional polymorphism (MAOA-uVNTR) genotype, MAOA-Long (MAOA-L) in females, MAOA-Short (MAOA-S) in males. Childhood maltreatment is associated with differential DNA methylation in several genes. Consistent with recent proposals, we hypothesized that the association of the interaction of MAOA genotype and maltreatment with aggressive behaviour is further moderated by methylation of a region of interest (ROI) spanning the first exon and partial first intron of MAOA., Method: The sample included 117 women and 77 men who completed interviews and questionnaires to report maltreatment and aggressive behaviour towards others and provided saliva samples for DNA extraction. The MAOA-uVNTR polymorphism was genotyped, and methylation of the MAOA ROI was assessed., Results: Following adjustment for substance misuse, psychoactive medication use, and in males tobacco use, the highest levels of aggressive behaviour were found among maltreated male carriers of MAOA-S with high levels of exonic methylation., Conclusion: Methylation levels within the MAOA ROI further contributed to the interaction of MAOA risk genotypes and maltreatment on aggressive behaviours among men., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Early life stress (ELS) or alcohol consumption can influence DNA methylation and affect gene expression. Monoamine oxidase A (Maoa) encodes the enzyme that metabolizes monoaminergic neurotransmitters crucial for the stress response, alcohol reward, and reinforcement. Previously, we reported lower Maoa expression in the nucleus accumbens and dorsal striatum of male rats exposed to ELS during the first three postnatal weeks, and to voluntary alcohol consumption in adulthood, compared with controls. The present study continued to investigate the effect of ELS and alcohol consumption on Maoa methylation, and its relation to Maoa expression in these animals. We selected candidate CpGs after performing next-generation bisulfite sequencing of the Maoa promoter, intron 1-5, and exons 5 and 6, together composed of 107 CpGs (5'-cytosine-phosphate-guanosine-3'), in a subgroup of rats. Pyrosequencing was used to analyze the methylation of 10 candidate CpGs in the promoter and intron 1 in the entire sample. ELS and alcohol displayed an interactive effect on CpG-specific methylation in the dorsal striatum. CpG-specific methylation correlated with Maoa expression, corticosterone levels, and alcohol consumption in a brain region-specific manner. CpG-specific methylation in the Maoa promoter was a potential moderator of the interaction of ELS with alcohol consumption on Maoa expression in the NAc. However, the findings were sparse, did not survive correction for multiple testing, and the magnitude of differences in methylation levels was small. In conclusion, CpG-specific Maoa methylation in the promoter and intron 1 may associate with ELS, alcohol consumption, and Maoa expression in reward-related brain regions., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Since the pioneering finding of Caspi and co-workers in 2002 that exposure to childhood maltreatment predicted later antisocial behaviour (ASB) in male carriers of the low-activity MAOA-uVNTR allele, frequent replication studies have been published. Two meta-analyses, one in 2006 and the other in 2014, confirmed the original findings by Caspi and co-workers. In the present paper, we review the literature, note some methodological aspects of candidate gene-environment interaction (cG×E) studies and suggest some future directions. Our conclusions are as follows. (1) The direction of the effect in a cG×E model may differ according to the positive and negative environmental background of the population. (2) There is a predictor-intersection problem such that when measuring one type of maltreatment in a person, other kinds of maltreatment often co-occur. Other forms of abuse are implicitly considered in statistical models; therefore, it is difficult to draw conclusions about the effects of timing and the severity of different forms of stressful life events in relation to ASB. (3) There is also an outcome-intersection problem because of the major intersection of ASB and other forms of mental health problems. It is likely that the G×E with MAOA is related to a common unmeasured factor. (4) For the G×E model, in which the effect of the gene on the outcome variable is dependent on other predictor variables, theoretically, hypothesis-driven statistical modelling is needed.

Childhood physical abuse (PA) and sexual abuse (SA) interact with monoamine oxidase A (MAOA) gene polymorphism to modify risk for mental disorders. In addition, PA and SA may alter gene activity through epigenetic mechanisms such as DNA methylation, thereby further modifying risk for disorders. We investigated whether methylation in a region spanning the MAOA first exon and part of the first intron was associated with PA and/or SA, MAOA genotype, alcohol dependence, drug dependence, depression disorders, anxiety disorders, and conduct disorder. 114 Swedish women completed standardized diagnostic interviews and questionnaires to report PA and SA, and provided saliva samples for DNA extraction. DNA was genotyped for MAOA-uVNTR polymorphisms, and methylation of a MAOA region of interest (chrX: 43,515,544-43,515,991) was measured. SA, not PA, was associated with hypermethylation of the MAOA first exon relative to no-abuse, and the association was robust to adjustment for psychoactive medication, alcohol and drug dependence, and current substance use. SA and MAOA-uVNTR genotype, but not their interaction, was associated with MAOA methylation. SA associated with all measured mental disorders. Hypermethylation of MAOA first exon mediated the association of SA with current depression, and both methylation levels and SA independently predicted lifetime depression. Much remains to be learned about the independent effects of SA and MAOA-uVNTR genotypes on methylation of the MAOA first exon.

Background: Epigenetic mechanisms are candidate moderators of the effect of maltreatment on brain and behavior. Interactions between maltreatment and the monoamine oxidase A upstream variable number tandem repeat genotype (MAOA-uVNTR) are associated with alcohol-related problems. However, presently it is not known whether DNA methylation moderates this association. The study focused on 53 young adult males and aimed to determine whether MAOA methylation moderated the association of alcohol-related problems with the interaction of MAOA-uVNTR and maltreatment, and whether alcohol consumption moderated the association of MAOA methylation with the interaction of MAOA-uVNTR and maltreatment., Methods: MAOA-uVNTR genotypes with ≤ 3 and > 3 repeats were categorized as short (S) and long (L), respectively. Data on maltreatment were obtained retrospectively, using self-reported questionnaires. DNA methylation of 16 candidate CpGs within part of the MAOA first exon and intron was assessed and grouped based on principal component analyses. Alcohol-related problems were assessed using the Alcohol Use Disorders Identification Test (AUDIT). Alcohol consumption was measured using AUDIT-C. Moderation effects were assessed and probed using the moderated moderation model and Johnson-Neyman's method, respectively., Results: Carriers of the S allele, who experienced maltreatment and displayed lower Component 1 (mean of CpGs 13-16 in the first intron) MAOA methylation levels, reported higher AUDIT score in contrast to L-allele carriers. Carriers of the S allele, who reported higher AUDIT-C score and experienced maltreatment, displayed lower Component 3 (mean of CpGs 2-6 in the first exon) MAOA methylation levels than L-allele carriers., Conclusions: Intronic methylation moderated the association of alcohol-related problems with the interaction of MAOA-uVNTR and maltreatment. Alcohol consumption moderated the association of exonic methylation with the interaction of MAOA-uVNTR and maltreatment. These results suggest that epigenetic factors as well as genotype and maltreatment play a role in the development of alcohol misuse among young adult males., (Copyright © 2017 by the Research Society on Alcoholism.)

Discordant associations between monoamine oxidase A (MAOA) genotype and high alcohol drinking have been reported in human and non-human primates. Environmental influences likely moderate genetic susceptibility. The biological basis for this interplay remains elusive, and inconsistencies call for translational studies in which conditions can be controlled and brain tissue is accessible. The present study investigated whether early life stress and subsequent adult episodic alcohol consumption affect Maoa expression in stress- and reward-related brain regions in the rat. Outbred Wistar rats were exposed to rearing conditions associated with stress (prolonged maternal separation) or no stress during early life, and given free choice between alcohol and/or water in adulthood. Transcript levels of Maoa were assessed in the ventral tegmental area, nucleus accumbens (NAc), medial prefrontal cortex, cingulate cortex, amygdala and dorsal striatum (DS). Blood was collected to assess corticosterone levels. After alcohol consumption, lower blood corticosterone and Maoa expression in the NAc and DS were found in rats exposed to early life stress compared with control rats. An interaction between early life stress and voluntary alcohol intake was found in the NAc. Alcohol intake before death correlated negatively with Maoa expression in DS in high alcohol-drinking rats exposed to early life stress. Maoa expression is sensitive to adulthood voluntary alcohol consumption in the presence of early life stress in outbred rats. These findings add knowledge of the molecular basis of the previously reported associations between early life stress, MAOA and susceptibility to alcohol misuse.

Background: Previous evidence of gene-by-environment interactions associated with emotional and behavioral disorders is contradictory. Differences in findings may result from variation in valence and dose of the environmental factor, and/or failure to take account of gene-by-gene interactions. The present study investigated interactions between the brain-derived neurotrophic factor gene (BDNF Val66Met), the serotonin transporter gene-linked polymorphic region (5-HTTLPR), the monoamine oxidase A (MAOA-uVNTR) polymorphisms, family conflict, sexual abuse, the quality of the child-parent relationship, and teenage delinquency., Methods: In 2006, as part of the Survey of Adolescent Life in Västmanland, Sweden, 1 337 high-school students, aged 17-18 years, anonymously completed questionnaires and provided saliva samples for DNA analyses., Results: Teenage delinquency was associated with two-, three-, and four-way interactions of each of the genotypes and the three environmental factors. Significant four-way interactions were found for BDNF Val66Met × 5-HTTLPR×MAOA-uVNTR × family conflicts and for BDNF Val66Met × 5-HTTLPR×MAOA-uVNTR × sexual abuse. Further, the two genotype combinations that differed the most in expression levels (BDNF Val66Met Val, 5-HTTLPR LL, MAOA-uVNTR LL [girls] and L [boys] vs BDNF Val66Met Val/Met, 5-HTTLPR S/LS, MAOA-uVNTR S/SS/LS) in interaction with family conflict and sexual abuse were associated with the highest delinquency scores. The genetic variants previously shown to confer vulnerability for delinquency (BDNF Val66Met Val/Met × 5-HTTLPR S × MAOA-uVNTR S) were associated with the lowest delinquency scores in interaction with a positive child-parent relationship., Conclusions: Functional variants of the MAOA-uVNTR, 5-HTTLPR, and BDNF Val66Met, either alone or in interaction with each other, may be best conceptualized as modifying sensitivity to environmental factors that confer either risk or protection for teenage delinquency., (© The Author 2015. Published by Oxford University Press on behalf of CINP.)

Objective: Monoamine oxidase A (MAOA) gene promoter region includes a variable number of tandem repeat (VNTR) associated with antisocial behaviour in adverse environment. We have examined the effect of the MAOA-uVNTR on mental health and academic success by using a population representative sample and a longitudinal design., Methods: The data of the older cohort (n = 593, aged 15 years at the original sampling) of the longitudinal Estonian Children Personality, Behaviour and Health Study (ECPBHS) were used. Follow-ups were conducted at ages 18 and 25 years. Aggressiveness, inattention and hyperactivity were reported by class teachers or, at older age, self-reported. Stressful life events, psychological environment in the family and interactions between family members were self-reported. Data of general mental abilities and education were obtained at the age of 25, and lifetime psychiatric disorder assessment was carried out with the Mini-International Neuropsychiatric Interview (MINI) interview., Results: MAOA-uVNTR genotype had no independent effect on aggressiveness, hyperactive and inattentive symptoms, and neither was there a genotype interaction with adverse life events. Interestingly, the proportion of male subjects with higher education by the age of 25 was significantly larger among those with MAOA low-activity alleles (χ² = 7.13; p = 0.008). Logistic regression revealed that MAOA low-activity alleles, higher mental abilities, occurrence of anxiety disorders and absence of substance-use disorder were significant independent predictors for higher education in male subjects., Conclusions: In a population representative sample of young subjects, the MAOA-uVNTR 'risk genotype' predicted better life outcomes as expressed in higher level of education.

The aim of the present study was to investigate MAOA gene-environment (G*E) interactions in relation to adolescent alcohol consumption. In the county of Västmanland, Sweden, all 17-18-year-old students were asked to complete an anonymous questionnaire and provide a saliva sample during class hours. A total of 2263 students completed the questionnaire (77.4%) and a saliva sample was provided by 2131 participants. Failed MAOA u-variable number of tandem repeats (VNTR) genotype analyses and internal non-responses left 851 boys and 735 girls (total n=1586) to be investigated. Alcohol use disorder identification test was used to measure hazardous alcohol consumption. MAOA u-VNTR was used to measure biological risk in interaction with poor family relations and experience of sexual abuse. The model was also adjusted for non-independent socioeconomic variables, separated parents, type of housing and parental unemployment. Results showed that the MAOA u-VNTR, in interaction with psychosocial risk factors, such as the quality of family relations and sexual abuse, was related to high alcohol consumption among adolescents. Girls, carrying the long MAOA u-VNTR variant showed a higher risk of being high alcohol consumers, whereas among boys, the short allele was related to higher alcohol consumption. The present study supports the hypothesis that there is a relation between MAOA u-VNTR and alcohol consumption and that this relation is modulated by environmental factors. Furthermore, the present study also supports the hypothesis that there is a sex difference in the G*E interaction., (© 2010 The Authors, Addiction Biology © 2010 Society for the Study of Addiction.)

The present study investigated a possible interaction between a functional polymorphism in the MAOA gene promoter (MAOA-VNTR) and childhood maltreatment in the prediction of adolescent male and female delinquency. A cohort of 1,825 high school students, 17-18 years old, completed an anonymous questionnaire during class hours which included questions on childhood maltreatment, sexual abuse, and delinquency. Saliva samples were collected for DNA isolation, and analyzed for the MAOA-VNTR polymorphism. Self-reported maltreatment was a strong risk factor for adolescent delinquent behavior. The MAOA genotype also showed a significant main effect when controlled for maltreatment. Boys with a short variant and girls with one or two long variants of the polymorphism showed a higher risk for delinquency when exposed to maltreatment. Our results confirm previous findings of an interaction between the MAOA-VNTR polymorphism and self-reported maltreatment. Results for boys and girls differ according to MAOA-VNTR genotype and direction of phenotypic expression.

Objective: Postpartum depression (PPD) is an under diagnosed and under treated mood disorder, with negative impact on both the mother and the infant's health. The aim of this study is to examine whether genetic variations in the monoaminergic neurotransmitter system, together with environmental stressors, contribute to the development of PPD symptoms., Methods: This nested case-control study included 275 women from a population-based cohort of delivering women in Sweden. A questionnaire containing the Edinburgh Postnatal Depression Scale was collected at 6 weeks and 6 months postpartum. Three functional polymorphisms were genotyped, catechol-O-methyltransferase (COMT)-Val158Met, monoamine oxidase A (MAOA)-upstream variable number tandem repeat (uVNTR) and serotonin transporter linked polymorphic region (5HTT-LPR). Stressful life events, maternity stressors and previous psychiatric contact were considered as potential risk factors., Results: COMT-Val158Met was significantly associated with PPD symptoms at 6 weeks, but not at 6 months postpartum. A significant gene-gene interaction effect was present between COMT-Val158Met and MAOA-uVNTR. In a gene-environment multivariate model, COMT-Val158Met, psychiatric contact and maternity stressors were significantly associated with PPD symptoms. Among those with history of psychiatric problems, the COMT-Val158Met and 5HTT-LPR risk variants were associated with PPD symptoms, whereas in the absence of previous psychiatric contact only maternity stressors were related to PPD symptoms., Conclusion: The interaction effect between monoaminergic genes and environmental stressors is likely to contribute to vulnerability for PPD. The different patterns of association according to history of psychiatric problems, if replicated, might be helpful in screening strategies.