Abnormal behavior associated with a point mutation in the structural gene for monoamine oxidase A

Regulation of impulsive and aggressive behaviours by a novel lncRNA

High impulsive and aggressive traits associate with poor behavioural self-control. Despite their importance in predicting behavioural negative outcomes including suicide, the molecular mechanisms underlying the expression of impulsive and aggressive traits remain poorly understood. Here, we identified and characterized a novel long noncoding RNA (lncRNA), acting as a regulator of the monoamine oxidase A (MAOA) gene in the brain, and named it MAOA-associated lncRNA (MAALIN). Our results show that in the brain of suicide completers, MAALIN is regulated by a combination of epigenetic mechanisms including DNA methylation and chromatin modifications. Elevated MAALIN in the dentate gyrus of impulsive-aggressive suicides was associated with lower MAOA expression. Viral overexpression of MAALIN in neuroprogenitor cells decreased MAOA expression while CRISPR-mediated knock out resulted in elevated MAOA expression. Using viral-mediated gene transfer, we confirmed that MAALIN in the hippocampus significantly decreases MAOA expression and exacerbates the expression of impulsive-aggressive behavioural traits in CD1 aggressive mice. Overall, our findings suggest that variations in DNA methylation mediate the differential expression of a novel lncRNA that acts on MAOA expression to regulate impulsive-aggressive behaviours.

State v. Yepez: Admissibility and Relevance of Behavioral Genetic Evidence in a Criminal Trial

The New Mexico Supreme Court recently considered whether a trial court had erred in excluding behavioral genetic evidence of a murder defendant's low-activity monoamine oxidase A (MAOA) gene, which the defendant argued had predisposed him-along with his history of childhood maltreatment-to "maladaptive or violent behavior." After an extensive analysis of the underlying science and its relevance to the case, the supreme court held unanimously that the trial judge had the discretion to exclude the MAOA evidence. The court's analysis provides insights into how other courts are likely to rule on the relevance of behavioral genetic evidence.

Sex-dependent monoamine oxidase isoforms expression patterns during human brain ageing

Human behavior is influenced by both genetic and environmental factors. Monoamine oxidase A (MAOA) is among the most investigated genetic determinants of violent behaviors, while the monoamine oxidase B (MAOB) is explored in Parkinson's disease. We collected twenty-four post-mortem brain tissue datasets of 3871 and 1820 non-demented males and females, respectively, who died from causes not attributable to neurodegenerative diseases. The gene expressions of MAOA and MAOB (MAO genes) were analyzed in these subjects, who were further stratified according to age into eleven groups ranging from late Infancy (5-9 months) to centenarians (>100 years). MAO genes were differently expressed in brains during the entire life span. In particular, maximal and minimal expression levels were found in early life and around the teen years. Females tended to have higher MAO gene levels throughout their lives than those found in age-matched males, even when expressions were separately measured in different brain regions. We demonstrated the existence of age- and sex- related variations in the MAO transcript levels in defined brain regions. More in-depth protein studies are needed to confirm our preliminary results obtained only on messenger RNAs in order to establish the role played by MAO genes in human development.

Metabolomics and computational analysis of the role of monoamine oxidase activity in delirium and SARS-COV-2 infection

Delirium is an acute change in attention and cognition occurring in ~ 65% of severe SARS-CoV-2 cases. It is also common following surgery and an indicator of brain vulnerability and risk for the development of dementia. In this work we analyzed the underlying role of metabolism in delirium-susceptibility in the postoperative setting using metabolomic profiling of cerebrospinal fluid and blood taken from the same patients prior to planned orthopaedic surgery. Distance correlation analysis and Random Forest (RF) feature selection were used to determine changes in metabolic networks. We found significant concentration differences in several amino acids, acylcarnitines and polyamines linking delirium-prone patients to known factors in Alzheimer's disease such as monoamine oxidase B (MAOB) protein. Subsequent computational structural comparison between MAOB and angiotensin converting enzyme 2 as well as protein-protein docking analysis showed that there potentially is strong binding of SARS-CoV-2 spike protein to MAOB. The possibility that SARS-CoV-2 influences MAOB activity leading to the observed neurological and platelet-based complications of SARS-CoV-2 infection requires further investigation.

Minimally invasive brain injections for viral-mediated transgenesis: New tools for behavioral genetics in sticklebacks

Behavioral genetics in non-model organisms is currently gated by technological limitations. However, with the growing availability of genome editing and functional genomic tools, complex behavioral traits such as social behavior can now be explored in diverse organisms. Here we present a minimally invasive neurosurgical procedure for a classic behavioral, ecological and evolutionary system: threespine stickleback (Gasterosteus aculeatus). Direct brain injection enables viral-mediated transgenesis and pharmaceutical delivery which bypasses the blood-brain barrier. This method is flexible, fast, and amenable to statistically powerful within-subject experimental designs, making it well-suited for use in genetically diverse animals such as those collected from natural populations. Developing this minimally invasive neurosurgical protocol required 1) refining the anesthesia process, 2) building a custom surgical rig, and 3) determining the normal recovery pattern allowing us to clearly identify warning signs of failure to thrive. Our custom-built surgical rig (publicly available) and optimized anesthetization methods resulted in high (90%) survival rates and quick behavioral recovery. Using this method, we detected changes in aggression from the overexpression of either of two different genes, arginine vasopressin (AVP) and monoamine oxidase (MAOA), in outbred animals in less than one month. We successfully used multiple promoters to drive expression, allowing for tailored expression profiles through time. In addition, we demonstrate that widely available mammalian plasmids work with this method, lowering the barrier of entry to the technique. By using repeated measures of behavior on the same fish before and after transfection, we were able to drastically reduce the necessary sample size needed to detect significant changes in behavior, making this a viable approach for examining genetic mechanisms underlying complex social behaviors.

Targeting monoamine oxidase A for T cell-based cancer immunotherapy

Monoamine oxidase A (MAO-A) is an enzyme best known for its function in the brain, where it breaks down neurotransmitters and thereby influences mood and behavior. Small-molecule MAO inhibitors (MAOIs) have been developed and are clinically used for treating depression and other neurological disorders. However, the involvement of MAO-A in antitumor immunity has not been reported. Here, we observed induction of the Maoa gene in tumor-infiltrating immune cells. Maoa knockout mice exhibited enhanced antitumor T cell immunity and suppressed tumor growth. MAOI treatment significantly suppressed tumor growth in preclinical mouse syngeneic and human xenograft tumor models in a T cell-dependent manner. Combining MAOI and anti-PD-1 treatments generated synergistic tumor suppression effects. Clinical data correlation studies associated intratumoral MAOA expression with T cell dysfunction and decreased patient survival in a broad range of cancers. We further demonstrated that MAO-A restrains antitumor T cell immunity through controlling intratumoral T cell autocrine serotonin signaling. Together, these data identify MAO-A as an immune checkpoint and support repurposing MAOI antidepressants for cancer immunotherapy.

The role of monoamine oxidase enzymes in the pathophysiology of neurological disorders

Monoamine oxidase enzymes are responsible for the degredation of serotonin, dopamine, and norepinephrine in the central neurvous system. Although it has been nearly 100 years since they were first described, we are still learning about their role in the healthy brain and how they are altered in various disease states. The present review provides a survey of our current understanding of monoamine oxidases, with a focus on their contributions to neuropsychiatric, neurodevelopmental, and neurodegenerative disease. Important species differences in monoamine oxidase function and development in the brain are highlighted. Sex-specific monoamine oxidase regulatory mechanisms and their implications for various neurological disorders are also discussed. While our understanding of these critical enzymes has expanded over the last century, gaps exist in our understanding of sex and species differences and the roles monoamine oxidases may play in conditions often comorbid with neurological disorders.

The neurobiology of human aggressive behavior: Neuroimaging, genetic, and neurochemical aspects

In modern societies, there is a strive to improve the quality of life related to risk of crimes which inevitably requires a better understanding of brain determinants and mediators of aggression. Neurobiology provides powerful tools to achieve this end. Pre-clinical and clinical studies show that changes in regional volumes, metabolism-function and connectivity within specific neural networks are related to aggression. Subregions of prefrontal cortex, insula, amygdala, basal ganglia and hippocampus play a major role within these circuits and have been consistently implicated in biology of aggression. Genetic variations in proteins regulating the synthesis, degradation, and transport of serotonin and dopamine as well as their signal transduction have been found to mediate behavioral variability observed in aggression. Gene-gene and gene-environment interactions represent additional important risk factors for aggressiveness. Considering the social burden of pathological forms of aggression, more basic and translational studies should be conducted to accelerate applications to clinical practice, justice courts, and policy making.

Monoamine oxidase A activity in fibroblasts as a functional confirmation of MAOA variants

Monoamine oxidase A (MAO‐A) deficiency is a rare inborn error of metabolism with impaired degradation of biogenic amines including 5‐hydroxytryptamine (5‐HT), resulting in borderline intellectual disability and behavioral abnormalities. Genetic variants in MAOA need functional confirmation to enable a definite diagnosis. To this end, we developed an inexpensive, simple and nonradioactive MAO‐A activity assay based on the conversion of 5‐HT into 5‐hydroxyindoleacetic acid (5‐HIAA). Fibroblast cell lysates were incubated with 5‐HT and aldehyde dehydrogenase to allow 5‐HIAA production. 5‐HIAA was quantified using high‐performance liquid chromatography with fluorimetric detection. We optimized reaction mixture components, pH, and substrate concentration and tested linearity and specificity of the assay. We verified the functional validity of the enzyme assay using fibroblasts of controls, female mutation carriers and MAO‐A deficient patients. This included a newly described patient with a novel MAOA variant (c.1336G>A, p.(Glu446Lys)), who represents the fifth MAO‐A deficiency family so far. The optimized enzyme assay showed good linearity and specificity. Application to clinical samples showed a 100% differentiation of affected patients (with negligible MAO‐A enzyme activity) and controls or mutation carriers. In conclusion, the described MAO‐A activity assay is easy to implement and can readily be used to test the pathogenicity of variants in the MAOA gene in a clinical setting. Especially in this era of whole‐exome (and whole‐genome) sequencing, this functional assay fulfills a clinical need for functional confirmation of a suspected diagnosis of MAO‐A deficiency.

From warrior genes to translational solutions: novel insights into monoamine oxidases (MAOs) and aggression

The pervasive and frequently devastating nature of aggressive behavior calls for a collective effort to understand its psychosocial and neurobiological underpinnings. Regarding the latter, diverse brain areas, neural networks, neurotransmitters, hormones, and candidate genes have been associated with antisocial and aggressive behavior in humans and animals. This review focuses on the role of monoamine oxidases (MAOs) and the genes coding for them, in the modulation of aggression. During the past 20 years, a substantial number of studies using both pharmacological and genetic approaches have linked the MAO system with aggressive and impulsive behaviors in healthy and clinical populations, including the recent discovery of MAALIN, a long noncoding RNA (lncRNA) regulating the MAO-A gene in the human brain. Here, we first provide an overview of the MAOs and their physiological functions, we then summarize recent key findings linking MAO-related enzymatic and gene activity and aggressive behavior, and, finally, we offer novel insights into the mechanisms underlying this association. Using the existing experimental evidence as a foundation, we discuss the translational implications of these findings in clinical practice and highlight what we believe are outstanding conceptual and methodological questions in the field. Ultimately, we propose that unraveling the specific role of MAO in aggression requires an integrated approach, where this question is pursued by combining psychological, radiological, and genetic/genomic assessments. The translational benefits of such an approach include the discovery of novel biomarkers of aggression and targeting the MAO system to modulate pathological aggression in clinical populations.

mRNA Levels of MAOA and 5-HT 2 A Receptor in Patients With Pathological Internet Use: Correlations With Comorbid Symptoms

Objective: Uncontrolled internet use may lead to the emergence of pathological internet use (PIU). PIU has become a global public health concern that can cause a range of psychotic symptoms, including anxiety, depression, and impulse control disorder. To date, we know very little about the principal biological factors related to PIU. Monoamine oxidase type A (MAOA) and serotonin (5-HT) 5-HT_2A receptor (5-HT_2AR) play critical roles in the development of behavioural and drug addictions. Thus, the aim of this study was to measure the relative expression of mRNA of MAOA and 5-HT_2AR in peripheral blood mononuclear cells (PBMCs) of patients with PIU and to determine the correlations between these biological indicators and the comorbid symptoms of patients with PIU. Methods: In this study, the mRNA of MAOA and 5-HT_2AR was detected using real-time PCR in PBMCs of the patients with PIU (n = 24) and healthy controls (HCs, n = 25). The relationship between the mRNA levels of MAOA and 5-HT_2AR and clinical symptoms in patients with PIU was further investigated. Results: MAOA mRNA in PBMCs was significantly upregulated in patients with PIU compared with that in HCs. mRNA levels of 5-HT_2AR were not found to differ significantly between HCs and patients with PIU. Correlation analyses further revealed a significant positive correlation between the relative expression of MAOA mRNA in PBMCs of patients with PIU and the Young's Internet Addiction Test and Self-Rating Depression Scale scores. Conclusion: The present study revealed upregulated expression of MAOA mRNA in patients with PIU and an association between the expression of MAOA mRNA and clinical symptoms of PIU, suggesting that the neurobiological changes may be similar between PIU and substance addiction. Additionally, this study demonstrated a potential association between comorbid symptoms and mRNA levels of MAOA.

The role of monoamine oxidase A in the neurobiology of aggressive, antisocial, and violent behavior: A tale of mice and men

Over the past two decades, research has revealed that genetic factors shape the propensity for aggressive, antisocial, and violent behavior. The best-documented gene implicated in aggression is MAOA (Monoamine oxidase A), which encodes the key enzyme for the degradation of serotonin and catecholamines. Congenital MAOA deficiency, as well as low-activity MAOA variants, has been associated with a higher risk for antisocial behavior (ASB) and violence, particularly in males with a history of child maltreatment. Indeed, the interplay between low MAOA genetic variants and early-life adversity is the best-documented gene × environment (G × E) interaction in the pathophysiology of aggression and ASB. Additional evidence indicates that low MAOA activity in the brain is strongly associated with a higher propensity for aggression; furthermore, MAOA inhibition may be one of the primary mechanisms whereby prenatal smoke exposure increases the risk of ASB. Complementary to these lines of evidence, mouse models of Maoa deficiency and G × E interactions exhibit striking similarities with clinical phenotypes, proving to be valuable tools to investigate the neurobiological mechanisms underlying antisocial and aggressive behavior. Here, we provide a comprehensive overview of the current state of the knowledge on the involvement of MAOA in aggression, as defined by preclinical and clinical evidence. In particular, we show how the convergence of human and animal research is proving helpful to our understanding of how MAOA influences antisocial and violent behavior and how it may assist in the development of preventative and therapeutic strategies for aggressive manifestations.

How Monoamine Oxidase A Decomposes Serotonin: An Empirical Valence Bond Simulation of the Reactive Step

The enzyme-catalyzed degradation of the biogenic amine serotonin is an essential regulatory mechanism of its level in the human organism. In particular, monoamine oxidase A (MAO A) is an important flavoenzyme involved in the metabolism of monoamine neurotransmitters. Despite extensive research efforts, neither the catalytic nor the inhibition mechanisms of MAO enzymes are currently fully understood. In this article, we present the quantum mechanics/molecular mechanics simulation of the rate-limiting step for the serotonin decomposition, which consists of hydride transfer from the serotonin methylene group to the N5 atom of the flavin moiety. Free-energy profiles of the reaction were computed by the empirical valence bond method. Apart from the enzymatic environment, the reference reaction in the gas phase was also simulated, facilitating the estimation of the catalytic effect of the enzyme. The calculated barrier for the enzyme-catalyzed reaction of 14.82 ± 0.81 kcal mol-1 is in good agreement with the experimental value of 16.0 kcal mol-1, which provides strong evidence for the validity of the proposed hydride-transfer mechanism. Together with additional experimental and computational work, the results presented herein contribute to a deeper understanding of the catalytic mechanism of MAO A and flavoenzymes in general, and in the long run, they should pave the way toward applications in neuropsychiatry.

Genetics of Equine Behavioral Traits

Behavior is a valuable quantitative trait in the horse because of its impact on performance, work, recreation, and prerequisite close interactions with humans. This article reviews what is known about the genetics of behavior in horses with an emphasis on the genetic basis for temperament traits, neuroendocrine function, and stereotypic behavior. The importance of using modern molecular genetic techniques to the study of equine behavior and recommendations for future research are also discussed. Ultimately, these studies enhance the understanding of the biology of behavior in the horse, improve handler and rider safety, and benefit horse welfare.

Re-wiring Guilt: How Advancing Neuroscience Encourages Strategic Interventions Over Retributive Justice

The increasing visibility of neuroscience employed in legal contexts has rightfully prompted critical discourse regarding the boundaries of its utility. High profile debates include some extreme positions that either undermine the relevance of neuroscience or overstate its role in determining legal responsibility. Here we adopt a conciliatory attitude, reaffirming the current value of neuroscience in jurisprudence and addressing its role in shifting normative attitudes about culpability. Adopting a balanced perspective about the interaction between two dynamic fields (science and law) allows for more fruitful consideration of practical changes likely to improve the way we engage in legal decision-making. Neuroscience provides a useful platform for addressing nuanced and multifaceted deterministic factors promoting antisocial behavior. Ultimately, we suggest that shifting normative attitudes about culpability vis-à-vis advancing neuroscience are not likely to promote major changes in the way we assign legal responsibility. Rather, it helps us to shed our harshest retributivist instincts in favor of more pragmatic strategies for combating the most conspicuous patterns promoting mass incarceration and recidivism.

Dysregulation of amino acids and lipids metabolism in schizophrenia with violence

BACKGROUND

Many studies have related biochemical characteristics to violence and have reported schizophrenia could elevated the risk of violent behaviour. However, the metabolic characteristics of schizophrenia patients with violence (V.SC) are unclear.

METHODS

To explore the metabolic characteristics of schizophrenia with violence and to identify potential biomarkers, untargeted metabolomics was performed by using gas chromatography time-of-flight mass spectrometry to analyse the plasma metabolites of fifty-three V.SC and twenty-four schizophrenia patients without violence (NV.SC). Multivariate and univariate analyses were performed to identify differential metabolites and biomarkers. Violence was assessed by the MacArthur Violence Assessment Study method. Psychiatric symptoms were assessed by the Positive and Negative Syndrome Scale.

RESULTS

Multivariate analysis was unable to distinguish V.SC from NV.SC. Glycerolipid metabolism and phenylalanine, tyrosine and tryptophan biosynthesis were the differential metabolic pathways between V.SC and NV.SC. We confirmed ten metabolites and five metabolites as metabolic biomarkers of V.SC by random forest and support vector machine analysis, respectively. The biomarker panel, including the ratio of L-asparagine to L-aspartic acid, vanillylmandelic acid and glutaric acid, yielded an area under the receiver operating characteristic curve of 0.808.

CONCLUSIONS

This study gives a holistic view of the metabolic phenotype of schizophrenia with violence which is characterized by the dysregulation of lipids and amino acids. These results might provide information for the aetiological understanding and management of violence in schizophrenia; however, this is a preliminary metabolomics study about schizophrenia with violence, which needs to be repeated in future studies.

Genomics of human aggression: current state of genome-wide studies and an automated systematic review tool

There are substantial differences, or variation, between humans in aggression, with its molecular genetic basis mostly unknown. This review summarizes knowledge on the genetic contribution to variation in aggression with the following three foci: (1) a comprehensive overview of reviews on the genetics of human aggression, (2) a systematic review of genome-wide association studies (GWASs), and (3) an automated tool for the selection of literature based on supervised machine learning. The phenotype definition 'aggression' (or 'aggressive behaviour', or 'aggression-related traits') included anger, antisocial behaviour, conduct disorder, and oppositional defiant disorder. The literature search was performed in multiple databases, manually and using a novel automated selection tool, resulting in 18 reviews and 17 GWASs of aggression. Heritability estimates of aggression in children and adults are around 50%, with relatively small fluctuations around this estimate. In 17 GWASs, 817 variants were reported as suggestive (P ≤ 1.0E), including 10 significant associations (P ≤ 5.0E). Nominal associations (P ≤ 1E) were found in gene-based tests for genes involved in immune, endocrine, and nervous systems. Associations were not replicated across GWASs. A complete list of variants and their position in genes and chromosomes are available online. The automated literature search tool produced literature not found by regular search strategies. Aggression in humans is heritable, but its genetic basis remains to be uncovered. No sufficiently large GWASs have been carried out yet. With increases in sample size, we expect aggression to behave like other complex human traits for which GWAS has been successful.

Nitric oxide interacts with monoamine oxidase to modulate aggression and anxiety-like behaviour

Nitric oxide (NO) is a gaseous neurotransmitter that has important behavioural functions in the vertebrate brain. In this study we compare the impact of decreased nitric NO signalling upon behaviour and neurobiology using both zebrafish and mouse. nitric oxide synthase mutant (nos1^-/-) zebrafish show significantly reduced aggression and an increase in anxiety-like behaviour without altered production of the stress hormone cortisol. Nos1^-/- mice also exhibit decreased aggression and are hyperactive in an open field test. Upon reduction of NO signalling, monoamine neurotransmitter metabolism is reduced as a consequence of decreased Monoamine oxidase activity. Treatment of nos1^-/- zebrafish with the 5-HT receptor 1A agonist 8-OH-DPAT rescues aggression and some aspects of anxiety-like behaviour. Taken together, the interplay between NO and 5-HT appears to be critical to control behaviour. Our cross-species approach challenges the previous notion that reduced neuronal NOS leads to increased aggression. Rather, Nos1 knock-out can also lead to decreased aggression in some situations, a finding that may have implications for future translational research.

Prediction of schizophrenia using MAOA-uVNTR polymorphism: A case-control study

CONTEXT

Schizophrenia has been associated with disorder of the dopamine system, which is downregulated by projections of the serotonin pathway. Dopamine and serotonin levels are regulated by a system of transporters and enzymes. In this research, dopamine transporter polymorphism (DAT-VNTR), serotonin transporter polymorphism (5-HTTLPR), monoamine oxidase A (MAOA-uVNTR), and catechol-o-methyl transferase (COMT Val158Met) polymorphisms have been investigated.

AIMS

The aim of this study was to asses frequencies of these polymorphisms in the healthy control group and patients and to asses association with schizophrenia.

SETTINGS AND DESIGN

Three hundred and fourteen healthy volunteers and 306 schizophrenia patients were included. Schizophrenia was diagnosed by Diagnostic and Statistical Manual-IV of the American Psychiatric Association, and mini international neuropsychiatric interview questionnaire was used for screening of healthy population.

MATERIALS AND METHODS

Genotyping was performed using polymerase chain reaction (PCR) reaction followed by gel electrophoresis and PCR-restriction fragment length polymorphism.

STATISTICAL ANALYSIS

Categorical data were analyzed using the Chi-square test, age between subgroups was compared using the Mann-Whitney test, and all polymorphisms were tested for Hardy-Weinberg equilibrium. Logistic regression analysis was used to set the prediction model of schizophrenia.

RESULTS

Difference in genotype distribution was observed for COMT Val158Met in female and DAT-VNTR polymorphism in overall sample P = 0.021 and P = 0.028, respectively. Statistically significant association of MAOA-uVNTR and schizophrenia was observed after adjustment for anamnestic predictors of disease. P = 0.010, 80.45% participants were correctly classified.

CONCLUSION

Our results suggest an association of MAOA-uVNTR polymorphism with schizophrenia. The difference in the distribution of COMT Val158Met and DAT-VNTR polymorphism support the involvement of dopamine system components in the pathogenesis of schizophrenia.

Nuclear quantum effects in enzymatic reactions: simulation of the kinetic isotope effect of phenylethylamine oxidation catalyzed by monoamine oxidase A

By using computational techniques for quantizing nuclear motion one can accurately reproduce kinetic isotope effect of enzymatic reactions, as demonstrated for phenylethylamine oxidation catalyzed by the monoamine oxidase A enzyme.

A systematic review and meta-analysis examining the interrelationships between chemical and non-chemical stressors and inherent characteristics in children with ADHD

Children may be more vulnerable to the combined interactions of chemical and non-chemical stressors from their built, natural, and social environments when compared to adults. Attention deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed childhood neurodevelopmental disorder and is considered a major public health issue, as 75% of childhood cases persist into adulthood. ADHD is characterized by developmentally inappropriate levels of hyperactivity, impulsivity, and inattention, with the neurotransmitter serotonin regulating these symptoms. Monoamine oxidase A (MAOA) aids in serotonin uptake and is often implicated in behavioral and emotional disorders, including ADHD. When children are exposed to cigarette smoke, bisphenol A (BPA), or organophosphate pesticides, MAOA activity is inhibited. Non-chemical stressors, such as traumatic childhood experiences, and lifestyle factors, complicate the relationship between genotype and exposures to chemical stressors. But the co-occurrence among outcomes between exposures to chemical stressors, non-chemical stressors, and the low activity MAOA genotype suggest that mental illness in children may be influenced by multiple interacting factors. In this systematic review, we examine the existing literature that combines exposures to chemical and non-chemical stressors (specifically childhood trauma), MAOA characteristics, and ADHD diagnosis to investigate the interrelationships present. We observe that chemical (lead [Pb], phthalates/plasticizers, persistent organic pollutants, and cigarette smoke) exposure is significantly related to ADHD in children. We also observed that existing literature examining the interaction between MAOA, exposures to chemical stressors, and traumatic experiences and their effect on ADHD outcomes is sparse. We recommend that future studies investigating childhood ADHD include chemical and non-chemical stressors and inherent characteristics to gain a holistic understanding of childhood mental health outcomes.

Monoamine and neuroendocrine gene-sets associate with frustration-based aggression in a gender-specific manner

Investigating phenotypic heterogeneity in aggression and understanding the molecular biological basis of aggression subtypes may lead to new prevention and treatment options. In the current study, we evaluated the taxonomy of aggression and examined specific genetic mechanisms underlying aggression subtypes in healthy males and females. Confirmatory Factor Analysis (CFA) was used to replicate a recently reported three-factor model of the Reactive Proactive Questionnaire (RPQ) in healthy adults (n = 661; median age 24.0 years; 41% male). Gene-set association analysis, aggregating common genetic variants within (a combination of) three molecular pathways previously implicated in aggression, i.e. serotonergic, dopaminergic, and neuroendocrine signaling, was conducted with MAGMA software in males and females separately (total n = 395) for aggression subtypes. We replicate the three-factor CFA model of the RPQ, and found males to score significantly higher on one of these factors compared to females: proactive aggression. The genetic association analysis showed a female-specific association of genetic variation in the combined gene-set with a different factor of the RPQ; reactive aggression due to internal frustration. Both the neuroendocrine and serotonergic gene-sets contributed significantly to this association. Our genetic findings are subtype- and sex-specific, stressing the value of efforts to reduce heterogeneity in research of aggression etiology. Importantly, subtype- and sex-differences in the underlying pathophysiology of aggression suggest that optimal treatment options will have to be tailored to the individual patient. Male and female needs of intervention might differ, stressing the need for sex-specific further research of aggression. Our work highlights opportunities for sample size maximization offered by population-based studies of aggression.

Human Dermal Fibroblast: A Promising Cellular Model to Study Biological Mechanisms of Major Depression and Antidepressant Drug Response

BACKGROUND

Human dermal fibroblasts (HDF) can be used as a cellular model relatively easily and without genetic engineering. Therefore, HDF represent an interesting tool to study several human diseases including psychiatric disorders. Despite major depressive disorder (MDD) being the second cause of disability in the world, the efficacy of antidepressant drug (AD) treatment is not sufficient and the underlying mechanisms of MDD and the mechanisms of action of AD are poorly understood.

OBJECTIVE

The aim of this review is to highlight the potential of HDF in the study of cellular mechanisms involved in MDD pathophysiology and in the action of AD response.

METHODS

The first part is a systematic review following PRISMA guidelines on the use of HDF in MDD research. The second part reports the mechanisms and molecules both present in HDF and relevant regarding MDD pathophysiology and AD mechanisms of action.

RESULTS

HDFs from MDD patients have been investigated in a relatively small number of works and most of them focused on the adrenergic pathway and metabolism-related gene expression as compared to HDF from healthy controls. The second part listed an important number of papers demonstrating the presence of many molecular processes in HDF, involved in MDD and AD mechanisms of action.

CONCLUSION

The imbalance in the number of papers between the two parts highlights the great and still underused potential of HDF, which stands out as a very promising tool in our understanding of MDD and AD mechanisms of action.

22q11.2 duplication: a review of neuropsychiatric correlates and a newly observed case of prototypic sociopathy

Callous-unemotional (CU) traits are highly disabling behavioral characteristics, common predictors of delinquency and criminality, and pathognomonic for antisocial personality disorder. They are highly heritable, but their specific molecular genetic causes are unknown. Here, we briefly review the literature on neuropsychiatric correlates of 22q11.2 duplication and describe a newly identified case of a 737-kb microduplication within the low copy repeat (LCR) B-D region, involving a 13-yr-old early adoptee with mild developmental delay and severe, chronic antisocial behavior of early childhood onset. When psychiatric symptoms have been reported in relation to duplications in this specific region, 19% of the reports feature aggression—but never previously CU traits—as a component of the phenotype. We discuss the potential implications of gain of function in this chromosomal region for heritable origins of sociopathy and their possible relation to genetic influences on aggression.

Novel Diels-Alder Type Adducts from Morus alba Root Bark Targeting Human Monoamine Oxidase and Dopaminergic Receptors for the Management of Neurodegenerative Diseases

In this study, we delineate the human monoamine oxidase (hMAO) inhibitory potential of natural Diels–Alder type adducts, mulberrofuran G (1), kuwanon G (2), and albanol B (3), from Morus alba root bark to characterize their role in Parkinson’s disease (PD) and depression, focusing on their ability to modulate dopaminergic receptors (D₁R, D_2LR, D₃R, and D₄R). In hMAO-A inhibition, 1–3 showed mild effects (50% inhibitory concentration (IC₅₀): 54‒114 μM). However, 1 displayed moderate inhibition of the hMAO-B isozyme (IC₅₀: 18.14 ± 1.06 μM) followed by mild inhibition by 2 (IC₅₀: 57.71 ± 2.12 μM) and 3 (IC₅₀: 90.59 ± 1.72 μM). Our kinetic study characterized the inhibition mode, and the in silico docking predicted that the moderate inhibitor 1 would have the lowest binding energy. Similarly, cell-based G protein-coupled receptors (GPCR) functional assays in vector-transfected cells expressing dopamine (DA) receptors characterized 1–3 as D₁R/D_2LR antagonists and D₃R/D₄R agonists. The half-maximum effective concentration (EC₅₀) of 1–3 on DA D₃R/D₄R was 15.13/17.19, 20.18/21.05, and 12.63/‒ µM, respectively. Similarly, 1–3 inhibited 50% of the DA response on D₁R/D_2LR by 6.13/2.41, 16.48/31.22, and 7.16/18.42 µM, respectively. A computational study revealed low binding energy for the test ligands. Interactions with residues Asp110, Val111, Tyr365, and Phe345 at the D₃R receptor and Asp115 and His414 at the D₄R receptor explain the high agonist effect. Likewise, Asp187 at D₁R and Asp114 at D_2LR play a crucial role in the antagonist effects of the ligand binding. Our overall results depict 1–3 from M. alba root bark as good inhibitors of hMAO and potent modulators of DA function as D₁R/D_2LR antagonists and D₃R/D₄R agonists. These active constituents in M. alba deserve in-depth study for their potential to manage neurodegenerative disorders (NDs), particularly PD and psychosis.

Identification of Single Nucleotide Polymorphisms in Porcine MAOA Gene Associated with Aggressive Behavior of Weaned Pigs after Group Mixing

Simple Summary

Monoamine Oxidase A (MAOA) gene had been reported as a candidate gene of aggressive behavior in several species. In the present study, the most aggressive and docile weaned pigs in each pen after group mixing were selected to identify single nucleotide polymorphisms in porcine MAOA gene associated with aggressive behavior. Constructs containing variable lengths of truncated porcine MAOA promoter were used to determine the promoter activity by a dual luciferase reporter system. The core promoter region of porcine MAOA was located at −679 bp to −400 bp. A total of nine single nucleotide polymorphisms (SNPs) in the MAOA gene were genotyped, of which six SNPs had significant differences in allele frequency between the aggressive and docile pigs. Four linked SNPs in porcine MAOA gene were associated with aggressive behavior in weaned pigs after mixing, which can be used as candidate molecular markers for aggressive behavior in pigs.

Abstract

Understanding the genetic background underlying the expression of behavioral traits has the potential to fasten the genetic progress for reduced aggressive behavior of pigs. The monoamine oxidase A (MAOA) gene is known as the “warrior” gene, as it has been previously linked to aggressive behavior in humans and livestock animals. To identify single nucleotide polymorphisms in porcine MAOA gene associated with aggressive behavior of pigs, a total of 500 weaned pigs were selected and mixed in 51 pens. In each pen, two aggressive and two docile pigs (a total of 204 pigs) were selected based on their composite aggressive score (CAS). Ear tissue was sampled to extract genomic DNA. Constructs containing variable lengths of truncated porcine MAOA promoter were used to determine the promoter activity by a dual luciferase reporter system. The core promoter region was located at −679 bp to −400 bp. A total of nine single nucleotide polymorphisms (SNPs) in MAOA gene were genotyped, of which six SNPs had significant differences (p < 0.05) in allele frequency between the aggressive and docile pigs. Linkage disequilibrium and association analyses showed that the pigs inherited the wild genotypes showed more aggressive behavior (p < 0.05) than pigs with the mutant genotypes of the four linked SNPs, rs321936011, rs331624976, rs346245147, and rs346324437. In addition, pigs of GCAA haplotype were more (p < 0.05) aggressive than the pigs with GCGA or ATGG haplotype. The construct containing the wild genotype GG of rs321936011 had lower (p = 0.031) promoter activity compared to the mutant genotype AA. These results suggest that the four linked SNPs in MAOA gene could be considered as a molecular marker for behavioral trait selection in pigs.

Epigenetic Modifications in Stress Response Genes Associated With Childhood Trauma

Adverse childhood experiences (ACEs) may be referred to by other terms (e.g., early life adversity or stress and childhood trauma) and have a lifelong impact on mental and physical health. For example, childhood trauma has been associated with posttraumatic stress disorder (PTSD), anxiety, depression, bipolar disorder, diabetes, and cardiovascular disease. The heritability of ACE-related phenotypes such as PTSD, depression, and resilience is low to moderate, and, moreover, is very variable for a given phenotype, which implies that gene by environment interactions (such as through epigenetic modifications) may be involved in the onset of these phenotypes. Currently, there is increasing interest in the investigation of epigenetic contributions to ACE-induced differential health outcomes. Although there are a number of studies in this field, there are still research gaps. In this review, the basic concepts of epigenetic modifications (such as methylation) and the function of the hypothalamic-pituitary-adrenal (HPA) axis in the stress response are outlined. Examples of specific genes undergoing methylation in association with ACE-induced differential health outcomes are provided. Limitations in this field, e.g., uncertain clinical diagnosis, conceptual inconsistencies, and technical drawbacks, are reviewed, with suggestions for advances using new technologies and novel research directions. We thereby provide a platform on which the field of ACE-induced phenotypes in mental health may build.

Mitochondrial dysfunction in rheumatoid arthritis: A comprehensive analysis by integrating gene expression, protein-protein interactions and gene ontology data

Several studies have reported mitochondrial dysfunction in rheumatoid arthritis (RA). Many nuclear DNA (nDNA) encoded proteins translocate to mitochondria, but their participation in the dysfunction of this cell organelle during RA is quite unclear. In this study, we have carried out an integrative analysis of gene expression, protein-protein interactions (PPI) and gene ontology data. The analysis has identified potential implications of the nDNA encoded proteins in RA mitochondrial dysfunction. Firstly, by analysing six synovial microarray datasets of RA patients and healthy controls obtained from the gene expression omnibus (GEO) database, we found differentially expressed nDNA genes that encode mitochondrial proteins. We uncovered some of the roles of these genes in RA mitochondrial dysfunction using literature search and gene ontology analysis. Secondly, by employing gene co-expression from microarrays and collating reliable PPI from seven databases, we created the first mitochondrial PPI network that is specific to the RA synovial joint tissue. Further, we identified hubs of this network, and moreover, by integrating gene expression and network analysis, we found differentially expressed neighbours of the hub proteins. The results demonstrate that nDNA encoded proteins are (i) crucial for the elevation of mitochondrial reactive oxygen species (ROS) and (ii) involved in membrane potential, transport processes, metabolism and intrinsic apoptosis during RA. Additionally, we proposed a model relating to mitochondrial dysfunction and inflammation in the disease. Our analysis presents a novel perspective on the roles of nDNA encoded proteins in mitochondrial dysfunction, especially in apoptosis, oxidative stress-related processes and their relation to inflammation in RA. These findings provide a plethora of information for further research.

Aggressive behavior in cattle is associated with a polymorphism in the MAOA gene promoter

Molecular mechanisms underlying aggressive behavior are primitive and similar among the subphylum Vertebrata. In humans, a primary goal in the study of aggression is to determine the neurobehavioral molecular factors triggering violence. Although several species have been used to study agonistic responses, researchers are limited by the difficulty of artificially inducing aggression in animals not selected for it. Conversely, the Lidia cattle breed has been selected since the eighteenth century to display agonistic responses based on traits such as aggressiveness, ferocity and mobility, all of them showing significant heritability values. This intensive selection may have driven shifts in specific allele frequencies. In a previous analysis across the autosomes, we revealed long-term selection regions including genes involved in behavioral development. In the present study, we focus on mapping recent signatures of selection associated with aggressiveness at chromosome X, by comparing Lidia cattle samples with two non-specialized Spanish breeds showing tamed behavior. The most significant markers peaked around the monoamine oxidase A (MAOA) gene, and thus the associations of three functionally important regions located near the promoter of this gene were further investigated. A polymorphism consisting of a variable number of tandem repeats of the nucleotide 'C' (BTX:105,462,494) and displaying lower number of repetitions in the Lidia breed when compared with the tamed breeds was detected. In silico analyses predicted that the g.105,462,494delsinsC variant may code for the Sp1 binding motif, one of the major transcription factors controlling the core promoter and expression of the MAOA gene in humans.

Neuroscientific and Genetic Evidence in Criminal Cases: A Double-Edged Sword in Germany but Not in the United States?

Aim of the Study

The study examines how neurobiological and genetic explanations of psychopathy influence decision-making of German law students about legal and moral responsibility and sentencing of a defendant in a case of manslaughter. Previous studies from the United States and Germany have been criticized because they partly contradict legal analyses of real-world criminal cases. With a modified design, which integrates the main criticism, we re-examined the impact of biological explanations for psychopathy on decision-making in the courtroom.

Methods

We developed an improved quasi-experimental design to probe three case vignettes presenting different explanations of psychopathy in a criminal case of manslaughter. All three vignettes present the same information about a forensic expert's testimony that is said to report compelling evidence for the diagnosis of "psychopathy." The independent variable being manipulated is the type of information supporting the expert diagnosis: either no biological explanation of "psychopathy" versus a neurological explanation (brain injury) versus a genetic explanation (MAOA gene). The outcome measure is a questionnaire on legal and moral responsibility, free will, the type of custody, and the duration of the sentence. The study is adequately powered. We openly publish the data and all statistical analyses as reproducible R scripts.

Results

The answers of German law students (n = 317) indicate that the omission of a neurobiological explanation is significantly associated with higher ratings of legal responsibility while compared to no biological explanation. However, there was no significant difference on the prison sentencing and type of custody assigned. Furthermore, there was no difference in the self-reported impact of the explanation of psychopathy on the participants' decision-making.

Conclusion

Our findings from German law students corroborates previous research on German judges but is markedly distinct from studies on United States judges. Whereas in the United States, biological information seems to have a mitigating effect, it seems to increase the rate of involuntary commitment to forensic psychiatric hospitals in Germany.

Role of monoamine-oxidase-A-gene variation in the development of glioblastoma in males: a case control study

Background

The Mono-amine oxidase-A (MAO-A) enzyme is involved in the degradation and regulation of catecholamines such as serotonin, dopamine, epinephrine and nor-epinephrine. Preclinical studies suggest that this enzyme may contribute to an environment favorable for growth of malignant glioma. The MAO-A gene is located on the X-chromosome and has at least one functional genetic polymorphism. The aim of the present study was to explore possible effects of MAO-A genotype on development of glioblastoma in males.

Methods

Genotypes for 437 glioma cases and 876 population-based controls from the Swedish Glioma International Case–Control study (GICC) were compared. We analyzed the germline DNA using the Illumina Oncoarray. We selected seven single nucleotide polymorphisms (SNPs) located in the MAO-A gene, and imputed genotypes based on data from the 1000 genomes project. We used 1579 male glioblastoma cases and 1875 controls comprising the whole GICC cohort for subsequent validation of findings.

Results

The rs144551722 SNP was a significant predictor of development of glioblastoma in males (p-value = 0.0056) but not in females even after correction for multiple testing. We conducted haplotype analysis to confirm an association between MAO-A gene and risk of glioblastoma (p-value = 0.016). We found similar results in the validation sample.

Conclusions

These results suggest the possibility of a role for the MAO-A enzyme and the MAO-A gene in the development of glioblastoma in males.

Venlafaxine plus melatonin ameliorate reserpine-induced depression-like behavior in zebrafish

Venlafaxine (VEN) is one of the first clinical drugs for the treatment of depression. Long-term use may cause a potentially life-threatening serotonin syndrome. Melatonin (MT) could ameliorate depression behavior. Therefore, the aim of this study was to investigate the antidepressant effects of venlafaxine in combination with melatonin on zebrafish. Reserpine was used to induce depression-like behavioral zebrafish. To explore the effects of combined use of venlafaxine and melatonin on depression-like zebrafish induced by reserpine. We tested the depressive behavior of adult zebrafish through a novel tank test, and evaluated the levels of serotonin (5-HT), dopamine (DA) and noradrenaline (NA) in zebrafish brain using enzyme-linked immunosorbent assay (ELISA), besides that the gene expression of serotonin transporters a (serta), dopamine transporters (dat) and norepinephrine transporters (net), vesicular monoamine transporter2 (vmat2) and monoamine oxidase (mao) were evaluated by qRT-PCR. The results showed that, compared with reserpine-only group, venlafaxine (VEN, 0.025 mg/L) and melatonin (MT, 1 μM) increased the parameters of exploration in the top of the tank and decreased freezing behavior significantly. Compared with reserpine-only group, the use of VEN combined with MT increased serotonin and norepinephrine levels significantly, while there was no obvious difference in dopamine content. The results of qRT-PCR showed that the use of VEN combined with MT significantly reduced the expression of serta and promoted the expression of vmat2, but had no significant effect on the expression of net, dat and mao. The results indicated that venlafaxine combined with melatonin showed more effective role to remedy the depressive symptoms in zebrafish, providing a reference for the clinical application of antidepressants.

Emotional stability is associated with the MAOA promoter uVNTR polymorphism in women

BACKGROUND

Neuroticism is associated with low emotional stability, and it is characterized by a tendency to perceive ordinary situations as threatening and difficult to manage. This personality trait has been associated with psychological distress and predicts some mental disorders. Previous studies have shown that women tend to be more neurotic than men and, in general, females have also a higher incidence of anxious and depressive disorders.

METHODS

We analyzed in a sample of 99 female university students (from 18 to 26 years old) if emotional stability, measured using the Big Five Questionnaire, was linked to polymorphic variants in candidate genes related to dopaminergic and serotonergic systems, and other personality variables.

RESULTS

We found that emotional stability and its subdimensions are genetically associated with MAOA-uVNTR polymorphism. Thus, women carriers of the 3-repeat allele (lower MAO-A expression) showed higher levels of emotional stability. No associations were found with other polymorphisms analyzed, including COMT Val¹⁵⁸ Met, 5-HTTLPR, and DAT 3'UTR VNTR. Furthermore, our results showed a negative correlation between emotional stability and depression, state anxiety, and trait anxiety. In fact, MAOA-uVNTR and trait anxiety also explained emotional stability and its subdimensions. We also found that other genetic characteristic, phenylthiocarbamide tasting, explained impulsivity, specifically tasters controlled impulses better than nontasters.

CONCLUSION

Our results indicate that neuroticism might be regulated by MAOA and could be a common factor between different phenotypes, such as aggressive behaviors or personality disorders, observed in women with higher activity genotype who had been exposed to negative environments during childhood. This study could lead to a better understanding of the basis of emotional stability and could lead to future projects for this purpose.

MAOA-VNTR genotype affects structural and functional connectivity in distributed brain networks

Previous studies have linked the low expression variant of a variable number of tandem repeat polymorphism in the monoamine oxidase A gene (MAOA‐L) to the risk for impulsivity and aggression, brain developmental abnormalities, altered cortico‐limbic circuit function, and an exaggerated neural serotonergic tone. However, the neurobiological effects of this variant on human brain network architecture are incompletely understood. We studied healthy individuals and used multimodal neuroimaging (sample size range: 219–284 across modalities) and network‐based statistics (NBS) to probe the specificity of MAOA‐L‐related connectomic alterations to cortical‐limbic circuits and the emotion processing domain. We assessed the spatial distribution of affected links across several neuroimaging tasks and data modalities to identify potential alterations in network architecture. Our results revealed a distributed network of node links with a significantly increased connectivity in MAOA‐L carriers compared to the carriers of the high expression (H) variant. The hyperconnectivity phenotype primarily consisted of between‐lobe (“anisocoupled”) network links and showed a pronounced involvement of frontal‐temporal connections. Hyperconnectivity was observed across functional magnetic resonance imaging (fMRI) of implicit emotion processing (p_FWE = .037), resting‐state fMRI (p_FWE = .022), and diffusion tensor imaging (p_FWE = .044) data, while no effects were seen in fMRI data of another cognitive domain, that is, spatial working memory (p_FWE = .540). These observations are in line with prior research on the MAOA‐L variant and complement these existing data by novel insights into the specificity and spatial distribution of the neurogenetic effects. Our work highlights the value of multimodal network connectomic approaches for imaging genetics.

Sex, age, or genetic differences related to play behaviors in Japanese Black calves

Play behavior in young animals has been used to evaluate the condition (health) of livestock. We investigated age, sex, and genetic differences of Japanese Black calves in relation to frequency of play behaviors (galloping, leaping, turning, bucking, head butting objects, and head shaking) and examined how these relationships might affect growth during the suckling stage. Locomotor play behaviors (galloping, leaping, turning, and bucking) and head butting objects gradually declined with the age for both sexes. The frequency of head butting was significantly higher in males than females. We found that significant interaction effects (age × MAOA polymorphism) in play behaviors (except head shaking) and the frequencies of locomotor play in calves without the wild-type allele were significantly higher than those in younger calves (2 and 6 weeks of age). Weight gain was significantly correlated with the frequency of locomotor play in females, but not in males. This study suggests that play in Japanese Black calves gradually declines as they mature and that play may be controlled by variations in the MAOA gene. In addition, the frequency of locomotor play may be an indicator of health in female calves.

The influence of genetic factors on personality and coping with stress among healthy late reproductive age women

Background

Psychological stress is a factor which predisposes people to many somatic and mental disorders. Women are at a significantly higher risk of stress than men, and their reactions to stress are stronger. Personality traits are thought to play a special role in the psychology of stress and may be crucial for the choice of a stress-coping strategy. Considering that stress is so common in everyday life, an attempt to understand how stress-coping styles are related to personality and genetic factors acquires special significance.

Purpose

The aim of this study was to analyze stress-coping styles and personality traits in healthy late reproductive age women with regard to genetic factors.

Patients and methods

The study involved 345 healthy late reproductive age women from northwest Poland, whose mean age was 42.3±4.5 years. The study was conducted using The Coping Inventory for Stressful Situations, The Neuroticism-Extraversion-Openness Five--Factor Inventory, and genetic testing.

Results

There were neither statistically significant relationships between personality traits and the genotype distribution of the 30-bp VNTR polymorphism in the MAO-A promoter region, nor between stress-coping styles and the genotype distribution of the 30-bp VNTR polymorphism in the MAO-A promoter region.

Conclusion

Based on the results, all personality traits statistically significantly correlated with the choice of task-oriented coping and emotion-oriented coping. Some of personality traits are genetically determined. The choice of a stress-coping style was significantly related to personality traits. A direct influence of genetic factors on the choice of a stress-coping style was not confirmed in our study.

Association of MAOA genetic variants and resilience with psychosocial stress: A longitudinal study of Syrian refugees

Early childhood trauma can have profound and lifelong effects on adult mental health and psychosocial wellbeing. Nevertheless, responses to trauma are highly variable. Genetic variants may help explain variation in responses to trauma by identifying alleles that associate with changes in mental health measures. Protective factors, such as resilience, likely also play an important role in responses to trauma. The effects of genetic variants, in combination with protective factors, on psychosocial health are not well understood, particularly in non-Western contexts. In this study, we test the relative influence of genetic variants of monoamine oxidase A (MAOA, a gene proposed to influence the impact of childhood trauma on adult violence and antisocial behavior), levels of resilience, and exposure to traumatic events on psychosocial stress and mental health trajectories over time. We use data from a cohort of 12-18-year-old Syrian refugees who were forcibly displaced to neighboring Jordan (n = 399). DNA samples and survey data on trauma exposure, resilience (CYRM-12), and psychosocial stress were collected at three time points: baseline, ~13 weeks, and ~48 weeks. Using multilevel models, we identified an association of MAOA variant, in males only, with symptom scores of psychosocial stress on the Perceived Stress Scale (PSS) over time (p = 8.1 x 10⁻⁴). We also found that resilience is strongly associated with PSS (p = 7.9 x 10⁻⁹), underscoring the importance of protective factors in influencing levels of psychosocial stress. Furthermore, there was an additive effect wherein the sharpest reductions in perceived psychosocial stress are seen in low-activity MAOA males with low trauma exposure or high resilience levels. Our results highlight the value of studies that integrate genetic and psychosocial factors to better understand complex phenotypes, such as responses to trauma in contexts of high trauma exposure.

Conduct disorder

Conduct disorder (CD) is a common and highly impairing psychiatric disorder that usually emerges in childhood or adolescence and is characterized by severe antisocial and aggressive behaviour. It frequently co-occurs with attention-deficit/hyperactivity disorder (ADHD) and often leads to antisocial personality disorder in adulthood. CD affects ~3% of school-aged children and is twice as prevalent in males than in females. This disorder can be subtyped according to age at onset (childhood-onset versus adolescent-onset) and the presence or absence of callous-unemotional traits (deficits in empathy and guilt). The aetiology of CD is complex, with contributions of both genetic and environmental risk factors and different forms of interplay among the two (gene-environment interaction and correlation). In addition, CD is associated with neurocognitive impairments; smaller grey matter volume in limbic regions such as the amygdala, insula and orbitofrontal cortex, and functional abnormalities in overlapping brain circuits responsible for emotion processing, emotion regulation and reinforcement-based decision-making have been reported. Lower hypothalamic-pituitary-adrenal axis and autonomic reactivity to stress has also been reported. Management of CD primarily involves parent-based or family-based psychosocial interventions, although stimulants and atypical antipsychotics are sometimes used, especially in individuals with comorbid ADHD.

Structure-Based Specific Detection and Inhibition of Monoamine Oxidases and Their Applications in Central Nervous System Diseases

Monoamine oxidases (MAOs) are the enzymes that catalyze the oxidation of monoamines, such as dopamine, norepinephrine, and serotonin, which serve as key neurotransmitters in the central nervous system (CNS). MAOs play important roles in maintaining the homeostasis of monoamines, and the aberrant expression or activation of MAOs underlies the pathogenesis of monoamine neurotransmitter disorders, including neuropsychiatric and neurodegenerative diseases. Clearly, detecting and inhibiting the activities of MAOs is of great value for the diagnosis and therapeutics of these diseases. Accordingly, many specific detection probes and inhibitors have been developed and substantially contributed to basic and clinical studies of these diseases. In this review, progress in the detecting and inhibiting of MAOs and their applications in mechanism exploration and treatment of neurotransmitter-related disorders is summarized. Notably, how the detection probes and inhibitors of MAOs were developed has been specifically addressed. It is hoped that this review will benefit the design of more effective and sensitive probes and inhibitors for MAOs, and eventually the treatment of monoamine neurotransmitter disorders.

Single nucleotide polymorphisms, variable number tandem repeats and allele influence on serotonergic enzyme modulators for aggressive and suicidal behaviors: A review

The serotonergic system plays key regulatory roles in cognition and emotion. Several lines of evidence suggest that genetic variation is associated with aggressive and suicidal behaviors. Genetic studies have largely focused on three types of variations: single nucleotide polymorphisms (SNPs), variable number tandem repeats (VNTRs), and alleles. 95 published papers (49 papers for aggression and 46 for suicide) were reviewed to summarize the impact of SNPs, VNTRs, and alleles of tryptophan hydroxylase (TPH, the rate-limiting enzyme in serotonin [5-HT] synthesis), 5-HT transporter (5-HTT), serotonergic receptors, monoamine oxidase (an enzyme that catalyzes 5-HT degradation) on aggression and suicidal behaviors. These study samples include healthy controls, psychiatric disease patients, and animal models. This article mainly reviews studies on the relationship between 5-HT transmissions and genetic variations involved in aggression (particularly impulsive aggression) or suicide in people with different ethnicities and psychiatric disorders. We found that most SNPs, VNTRs, and alleles exerted influences on aggression or suicide. Only A128C in TPH1, A138G in 5-HT2A, and L type in the VNTR of monoamine oxidase A (MAOA) affected both aggression and suicide. The associations between some genetic variations and aggression/suicide may be influenced by gender, age, ethnicity, psychiatric disease, and even parenting or prenatal stress. These findings may help clarify how genetic and environmental factors influence the development of aggressive and suicidal behaviors.

MAOA variants differ in oscillatory EEG & ECG activities in response to aggression-inducing stimuli

Among the genetic variations in the monoamine oxidase A (MAOA) gene, upstream variable number tandem repeats (uVNTRs) of the promoter have been associated with individual differences in human physiology and aggressive behaviour. However, the evidence for a molecular or neural link between MAOA uVNTRs and aggression remains ambiguous. Additionally, the use of inconsistent promoter constructs in previous studies has added to the confusion. Therefore, it is necessary to demonstrate the genetic function of MAOA uVNTR and its effects on multiple aspects of aggression. Here, we identified three MAOA alleles in Koreans: the predominant 3.5R and 4.5R alleles, as well as the rare 2.5R allele. There was a minor difference in transcriptional efficiency between the 3.5R and 4.5R alleles, with the greatest value for the 2.5R allele, in contrast to existing research. Psychological indices of aggression did not differ among MAOA genotypes. However, our electroencephalogram and electrocardiogram results obtained under aggression-related stimulation revealed oscillatory changes as novel phenotypes that vary with the MAOA genotype. In particular, we observed prominent changes in frontal γ power and heart rate in 4.5R carriers of men. Our findings provide genetic insights into MAOA function and offer a neurobiological basis for various socio-emotional mechanisms in healthy individuals.

Serotonergic Contributions to Human Brain Aggression Networks

Aggressive behavior is associated with dysfunctional frontolimbic emotion regulation circuits. Recent findings suggest serotonin as a primary transmitter for prefrontal amygdala control. However, the association between serotonin levels, amygdala regulation, and aggression is still a matter of debate. Neurobehavioral models furthermore suggest a possible mediating influence of the monoamine oxidase A gene (MAOA) on this brain-behavior relationship, with carriers of low expressing allele varieties being a risk group for aggression. In the present study, we investigated the influence of brain serotonin modulation and MAOA genotype on functional amygdala connectivity during aggressive behavior. Modulation of serotonergic neurotransmission with acute tryptophan depletion (ATD) and placebo were administered in a double-blind, cross-over design in 38 healthy male participants. Aggressive behavior was modeled in a violent video game during simultaneous assessment of brain activation with functional magnetic resonance imaging (fMRI). Trait aggression was measured with the Buss-Perry Aggression Questionnaire (BP-AQ), and MAOA genotypes were assessed from blood samples. Voxel-wise functional connectivity with anatomically defined amygdala was calculated from the functional data. Tryptophan depletion with ATD reduced aggression-specific amygdala connectivity with bilateral supramarginal gyrus. Moreover, ATD impact was associated with trait aggression and MAOA genotype in prefrontal cortex regions. In summary, serotonergic corticolimbic projections contribute to aggressive behavior. Genotype-specific vulnerability of frontolimbic projections may underlie the elevated risk in low expressing allele carriers.