COMT Genetic Reduction Produces Sexually Divergent Effects on Cortical Anatomy and Working Memory in Mice and Humans

The Influence of Genetic Polymorphic Variability of the Catechol-O-methyltransferase Gene in a Group of Patients with a Diagnosis of Behavioural Addiction, including Personality Traits

Gambling Disorder (GD) is characterised by a harmful, enduring, and recurrent involvement in betting-related behaviours. Therefore, GD shares similar biological mechanisms and symptoms to substance use disorders (SUD). Therefore, in this study, we chose the behavioural addictions group. During the examination and recruitment to the study, it turned out that all the people undergoing treatment for gambling addiction were also addicted to amphetamines, which is consistent with the biological mechanism related to cerebral neurotransmission. The aim of the study was to investigate the association of the COMT gene polymorphism with behavioral addiction. The study group consisted of 307 participants: 107 men with gambling disorder and amphetamine dependency (mean age = 27.51, SD = 5.25) and 200 non-addicted, nor dependent, free from neuro-psychiatric disorders control group men (mean age = 20.20, SD = 4.51). Both groups were subjected to psychometric evaluation using the State-Trait Anxiety Inventory and the NEO Five-Factor Personality Inventory. Genomic DNA was extracted from venous blood following standard protocols. Determination of the rs4680 polymorphism in the COMT gene was performed using the real-time PCR technique. Statistically significant differences in the frequency of rs4680 genotypes were found in the tested sample of subjects compared with the control group (p = 0.03543). Subjects with gambling disorder and amphetamine use disorder compared to the control group obtained higher scores in the assessment of the STAI trait scale (p = 0.0019), state scale (p < 0.0000), and NEO-FFI Neuroticism scale (p < 0.0000). Significantly lower results were obtained for the NEO-FFI Agreeability scale (p < 0.0000). Additionally, a significant statistical impact of gambling disorder and amphetamine use disorder, and the COMT rs4680 genotype was demonstrated for the score of the STAI trait (p = 0.0351) and state (p = 0.0343) and the NEO-FFI Conscientiousness scale (p = 0.0018). We conclude that COMT and its polymorphic variant influence the development of addiction. Still, considering its multifactorial and polygenic nature, it should be combined with other factors such as personality.

Sex-dependent differences in animal cognition

The differences in cognitive processes driven by biological sex are the issues that have gotten growing attention recently. Considering the increasing population suffering from various cognitive impairments and the development of therapeutic strategies, it is essential that we recognize the mechanisms responsible for discrepancies observed in male and female learning and memory functions. In this review, we discuss recent reports from preclinical studies on rodents regarding selected cognitive domains to explore the state of knowledge on sex-dependent differences and point to challenges encountered during such research. We focus on spatial, recognition, and emotional memory, as well as on executive functions, such as attention, cognitive flexibility, and working memory. This review will help to acknowledge sex-related differences in cognition and indicate some fields that lack sufficient data.

Dopaminergic signalling and behavioural alterations by Comt-Dtnbp1 genetic interaction and their clinical relevance

BACKGROUND AND PURPOSE

Cognitive and motor functions are modulated by dopaminergic signalling, which is shaped by several genetic factors. The biological effects of single genetic variants might differ depending on epistatic interactions that can be functionally multi-directional and non-linear.

EXPERIMENTAL APPROACH

We performed behavioural and neurochemical assessments in genetically modified mice and behavioural assessments and genetic screening in human patients with 22q11.2 deletion syndrome (22q11.2DS).

KEY RESULTS

Here, we confirm a genetic interaction between the Comt (catechol-O-methyltransferase, human orthologue: COMT) and Dtnbp1 (dystrobrevin binding protein 1, alias dysbindin, human orthologue: DTNBP1) genes that modulate cortical and striatal dopaminergic signalling in a manner not predictable by the effects of each single gene. In mice, Comt-by-Dtnbp1 concomitant reduction leads to a hypoactive mesocortical and a hyperactive mesostriatal dopamine pathway, associated with specific cognitive abnormalities. Like mice, in subjects with the 22q11.2DS (characterized by COMT hemideletion and dopamine alterations), COMT-by-DTNBP1 concomitant reduction was associated with analogous cognitive disturbances. We then developed an easy and inexpensive colourimetric kit for the genetic screening of common COMT and DTNBP1 functional genetic variants for clinical application.

CONCLUSIONS AND IMPLICATIONS

These findings illustrate an epistatic interaction of two dopamine-related genes and their functional effects, supporting the need to address genetic interaction mechanisms at the base of complex behavioural traits.

The COMT gene modulates the relationship between bilingual adaptation in executive function and decision-making: an EEG study

Bilingual adaptive control mechanisms appear to be linked to congenital genetic factors such as dopamine (DA) genes. However, it is unclear as to whether acquired cognitive exercise can vanquish innate influences that allow bilingual executive advantages to be shown in other cognitive areas. In the present study, we examine the relationship between gene-dependent executive control and decision-making by targeting the enzyme catecholamine-O-methyltransferase (COMT) and employing electroencephalography (EEG). Chinese-English bilinguals (N = 101) participated in a language switching task and the Iowa Gambling Task (IGT). The findings showed that COMT Val158Met polymorphism played a complex role in decision-making and bilingual executive control processing: Bilinguals with Valine (Val) homozygotes had poorer performance in the IGT, while Methionine (Met) carriers had larger switch costs in the language switching task. Second, the cross-task relationships varied among bilinguals with different COMT genotypes: Bilinguals with Met allele genotypes showed larger switch costs and better performance on the IGT. These findings suggest that bilinguals who carry Met allele are equipped with more efficient adaptive mechanisms of executive functions that are generalized to other cognitive domains.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-022-09867-2.

Genetic bases of language control in bilinguals: Evidence from an EEG study

Previous studies have debated whether the ability for bilinguals to mentally control their languages is a consequence of their experiences switching between languages or whether it is a specific, yet highly-adaptive, cognitive ability. The current study investigates how variations in the language-related gene FOXP2 and executive function-related genes COMT, BDNF, and Kibra/WWC1 affect bilingual language control during two phases of speech production, namely the language schema phase (i.e., the selection of one language or another) and lexical response phase (i.e., utterance of the target). Chinese-English bilinguals (N = 119) participated in a picture-naming task involving cued language switches. Statistical analyses showed that both genes significantly influenced language control on neural coding and behavioral performance. Specifically, FOXP2 rs1456031 showed a wide-ranging effect on language control, including RTs, F(2, 113) = 4.00, FDR p = .036, and neural coding across three-time phases (N2a: F(2, 113) = 4.96, FDR p = .014; N2b: F(2, 113) = 4.30, FDR p = .028, LPC: F(2, 113) = 2.82, FDR p = .060), while the COMT rs4818 (ts >2.69, FDR ps < .05), BDNF rs6265 (Fs >5.31, FDR ps < .05), and Kibra/WWC1 rs17070145 (ts > -3.29, FDR ps < .05) polymorphisms influenced two-time phases (N2a and N2b). Time-resolved correlation analyses revealed that the relationship between neural coding and cognitive performance is modulated by genetic variations in all four genes. In all, these findings suggest that bilingual language control is shaped by an individual's experience switching between languages and their inherent genome.

Gender divergent effect of COMT gene rs4680 polymorphism on the association between executive dysfunction and psychotic-like experiences

AIM

Premorbid cognitive impairments are observed prior to the onset of schizophrenia. Catechol-O-methyltransferase (COMT) rs4680 is associated with psychosis and plays a crucial role in the development of the executive function. In addition, genetic COMT variations and gender affect its enzymatic activity. Therefore, the aim of this study was to evaluate the impact of COMT rs4680 on the relationship between executive dysfunction and psychotic-like experiences (PLEs) in college students, with the additional investigation of the gender difference.

METHODS

A total of 463 students provided biological samples for DNA analysis and the COMT gene rs4680 polymorphism was discriminated by the improved multiplex ligase detection reaction method. They also completed the Prodromal Questionnaire and the Dysexecutive Questionnaire.

RESULTS

Executive dysfunction significantly predicted positive PLEs in the total, male and female population (β = 0.515, 0.508 and 0.512, p < 0.001). The results of moderated analysis revealed that COMT rs4680 recessive genetic model ('AA genotype' versus 'G carrier') moderated the relationship between executive dysfunction and psychotic-like experience in the total and females (p = 0.002 and p <0.001, respectively), but not in males.

CONCLUSION

These findings revealed a female-specific effect of COMT rs4680 on the relationship between executive dysfunction and PLEs in young adults.

Catechol-O-Methyltransferase Effects on Smoking: A Review and Proof of Concept of Sex-Sensitive Effects

Purpose of Review

This article reviews recent research on how catechol-O-methyltransferase (COMT) may impact cigarette smoking behavior, and how effects may be sex-sensitive. Preliminary data are presented on sex-sensitive effects of COMT on response to short-term abstinence in individuals who smoke.

Recent Findings

Although research is mixed, functional variants in the COMT gene have been linked with smoking behavior, cessation outcomes and nicotine abstinence-related symptoms. Our proof-of-concept preliminary data from a human laboratory study of individuals who smoke cigarettes found that those with the high COMT enzyme activity genotype (Val/Val) reported more severe smoking urges and withdrawal symptoms following overnight abstinence than Met carriers. These effects were present in women, but not in men and were abstinent-dependent, in that they dissipated following nicotine administration.

Summary

The preliminary data showing sex-sensitive pharmacogenetic effects may shed light on mechanisms contributing to sex differences in barriers to smoking cessation or potential sex-specific treatment options.

The inconsistent mediating effect of catechol O methyl transferase Val158Met polymorphism on the sex difference of cognitive impairment in schizophrenia patients

OBJECTIVE

Schizophrenia is a multifaceted mental disorder characterized by heterogeneous positive/negative symptoms and cognitive deficits. Sex differences have been reported in various aspects of the disease. However, the underlying genetic reasons remain unelucidated. Recent studies show that the influence of COMT Val158Met (rs4680) variation is sexually dimorphic. Thus, this study aims to explore whether there is an effect of the interaction between COMT Val158Met (rs4680) polymorphism and sex on patients' clinical characteristics and cognitive function.

MATERIALS AND METHODS

We recruited 367 in patients with chronic schizophrenia (246 males and 121 females) and 419 healthy controls (172 males and 247 females). The cognitive performance was assessed by Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and the COMT Val158Met (rs4680) polymorphism is genotyped. The psychopathological symptoms of the patients were assessed by the Positive and Negative Syndrome Scale (PANSS).

RESULTS

We find that male patients had a significantly higher proportion of carrying the Val allele and Val/Val carriers exhibited more severe positive symptoms and cognitive impairment than Met carriers. COMT Val158Met (rs4680) polymorphism inconsistently mediated the relationship between sex and cognitive performance in schizophrenia patients.

CONCLUSION

These findings suggest that COMT Val158Met (rs4680) polymorphism is associated with the risk and severity of schizophrenia in a sexually dimorphic way and contributes more to the clinical symptoms and cognitive impairment in male patients with schizophrenia.

mTOR-related synaptic pathology causes autism spectrum disorder-associated functional hyperconnectivity

Postmortem studies have revealed increased density of excitatory synapses in the brains of individuals with autism spectrum disorder (ASD), with a putative link to aberrant mTOR-dependent synaptic pruning. ASD is also characterized by atypical macroscale functional connectivity as measured with resting-state fMRI (rsfMRI). These observations raise the question of whether excess of synapses causes aberrant functional connectivity in ASD. Using rsfMRI, electrophysiology and in silico modelling in Tsc2 haploinsufficient mice, we show that mTOR-dependent increased spine density is associated with ASD -like stereotypies and cortico-striatal hyperconnectivity. These deficits are completely rescued by pharmacological inhibition of mTOR. Notably, we further demonstrate that children with idiopathic ASD exhibit analogous cortical-striatal hyperconnectivity, and document that this connectivity fingerprint is enriched for ASD-dysregulated genes interacting with mTOR or Tsc2. Finally, we show that the identified transcriptomic signature is predominantly expressed in a subset of children with autism, thereby defining a segregable autism subtype. Our findings causally link mTOR-related synaptic pathology to large-scale network aberrations, revealing a unifying multi-scale framework that mechanistically reconciles developmental synaptopathy and functional hyperconnectivity in autism.

Interacting Roles of COMT and GAD1 Genes in Patients with Treatment-Resistant Schizophrenia: a Genetic Association Study of Schizophrenia Patients and Healthy Controls

The projection from dopaminergic neurons to gamma-aminobutyric acid (GABA) interneurons in the prefrontal cortex is involved in the etiology of schizophrenia. The impact of interacting effects between dopamine signals and the expression of GABA on the clinical phenotypes of schizophrenia has not been studied. Since these interactions could be closely involved in prefrontal cortex functions, patients with specific alleles of these relevant molecules (which lead to lower or vulnerable genetic functions) may develop treatment-refractory symptoms. We conducted a genetic association study focusing on COMT and GAD1 genes for a treatment-resistant schizophrenia (TRS) group (n=171), a non-TRS group (n=592), and healthy controls (HC: n=447), and we examined allelic combinations specific to TRS. The results revealed that the percentage of subjects with Met allele of rs4680 on the COMT gene and C/C homozygote of rs3470934 on the GAD1 gene was significantly higher in the TRS group than the other two groups. There was no significant difference between the non-TRS group and HC groups. Considering the direction of functions of these single-nucleotide polymorphisms revealed by previous studies, we speculate that subjects with the Met/CC allelic combination could have a higher dopamine level and a lower expression of GABA in the prefrontal cortex. Our results suggest that an interaction between the dopaminergic signal and GABA signal intensities could differ between TRS patients and patients with other types of schizophrenia and healthy subjects.

The interactive effect of genetic polymorphisms of IL-10 and COMT on cognitive function in schizophrenia

Dopaminergic and inflammatory systems have been proven to play an important role in the cognitive deficits of schizophrenia. Although increasing evidence indicates two systems have strong interaction, the relevant research on this interaction is still limited. Catechol-o-methyltransferase (COMT) and Interleukin-10 (IL-10) play critical functions in dopaminergic and inflammatory systems respectively, and their genetic polymorphisms are both associated with cognitive function. However, the interactive effect of their genetic polymorphisms has not been investigated. In this study, COMT Val158Met (rs4680) and IL-10 -592A/C (rs1800872) polymorphisms were measured in patients with chronic schizophrenia (n = 244) and healthy controls (n = 396), and their cognitive functions were assessed using the "Repeatable Battery for the Assessment of Neuropsychological Status" (RBANS). We found that IL-10 alone had no effect on cognitive function, while COMT affected language ability and interacted with the schizophrenia (case vs control) or sex in multiple RBANS indexes. Additionally, we found there was a significant interactive effect between IL-10 and COMT polymorphisms on multiple cognitive indexes of RBANS. In detail, the analysis showed that the IL-10 polymorphism had opposite effects on cognitive function in different COMT genotype carriers; meanwhile, the polymorphism of COMT only had a significant effect on cognitive function in IL-10 C carriers. And this interaction was more significant in schizophrenia than in controls. Our study discovered for the first time, there is an interactive effect between IL-10 and COMT genetic polymorphisms on cognitive function, which is valuable for further investigations and drug administrations associated with both systems.

The epistatic interaction between the dopamine D3 receptor and dysbindin-1 modulates higher-order cognitive functions in mice and humans

The dopamine D2 and D3 receptors are implicated in schizophrenia and its pharmacological treatments. These receptors undergo intracellular trafficking processes that are modulated by dysbindin-1 (Dys). Indeed, Dys variants alter cognitive responses to antipsychotic drugs through D2-mediated mechanisms. However, the mechanism by which Dys might selectively interfere with the D3 receptor subtype is unknown. Here, we revealed an interaction between functional genetic variants altering Dys and D3. Specifically, both in patients with schizophrenia and in genetically modified mice, concomitant reduction in D3 and Dys functionality was associated with improved executive and working memory abilities. This D3/Dys interaction produced a D2/D3 imbalance favoring increased D2 signaling in the prefrontal cortex (PFC) but not in the striatum. No epistatic effects on the clinical positive and negative syndrome scale (PANSS) scores were evident, while only marginal effects on sensorimotor gating, locomotor functions, and social behavior were observed in mice. This genetic interaction between D3 and Dys suggests the D2/D3 imbalance in the PFC as a target for patient stratification and procognitive treatments in schizophrenia.

Platelet MAO activity and COMT Val158Met genotype interaction predicts visual working memory updating efficiency

The exact mechanism how serotonergic and dopaminergic systems relate to one another in working memory (WM) updating is unknown. Platelet monoamine oxidase (MAO) has been used as a marker for central serotonergic capacity, and catechol-O-methyltransferase (COMT) as a marker for central dopaminergic capacity. This study aimed to describe the interaction of platelet MAO activity and COMT Val158Met genotype in visual working memory updating: the ability to replace old information with new within hundreds of milliseconds. Previous studies suggest that platelet MAO activity and COMT Val158Met genotype could have an interaction effect on working memory. However, there are no studies that have directly examined the interaction of these biomarkers in WM updating. We used a 2-back updating task with facial expressions and defined updating efficiency as response times for correct responses. 455 subjects from a population representative sample were included. Mixed models were used for data analysis with an aim to study the interaction of COMT Val158Met genotype (Val/Val, Val/Met and Met/Met) and the level of MAO activity (high vs low). Education, IQ, sex, simple reaction times, and overall updating accuracy were included as covariates. We found that the effect of COMT Val158Met on updating efficiency depends on the level of platelet MAO activity. Low MAO in contrast to high MAO was associated with an increase in updating efficiency in Val/Met but a decrease in Met/Met. The results are discussed in the context of serotonin and dopamine functions in brain regions related to WM. The findings support the view that serotonin modulates dopaminergic activation in updating and contribute to understanding the role of serotonin in PFC, top-down inhibitory signals, and its interactions with dopamine in WM processes.

Female-specific effects of the catechol-O-methyl transferase Val158Met gene polymorphism on working memory-related brain function

The catechol-O-methyltransferase (COMT) Val¹⁵⁸Met polymorphism has been associated with working memory (WM) in many studies, but the results have not been consistent. One plausible explanation is sex-specific effects of this polymorphism as reported in several studies. The current study aimed to explore the sex-specific effects of the COMT Val¹⁵⁸Met polymorphism on WM-related brain function in an elderly sample. We found that Val homozygotes outperformed Met allele carriers on the backward digit span subtest for both males and females. The triangular part of the left inferior frontal gyrus and the left inferior temporal gyrus exhibited higher activation in Met allele carriers compared with Val homozygotes during the n-back task, while the background functional connectivity (bFC) between the left angular gyrus (ANG) and the right ANG was enhanced in Val homozygotes as compared to Met allele carriers. Finally, the associations between brain activation, bFC (among various regions), and WM performance were identified only in specific genotype groups of the female participants. These findings provide new insights into the role of COMT Val¹⁵⁸Met gene polymorphism in brain function, particularly its female-specific nature.

The Effects of COMT Polymorphism on Cortical Thickness and Surface Area Abnormalities in Children with ADHD

The catechol-O-methyltransferase (COMT) gene is associated with frontal cortex development and the pathophysiology of attention-deficit/hyperactivity disorder (ADHD). However, how the COMT gene impacts brain structure and behavior in ADHD remains unknown. In the present study, we identify the effect of COMT on cortical thickness and surface area in children with ADHD and children with typically developing (TD) using a machine learning approach. In a sample of 39 children with ADHD and 34 age- and IQ-matched TD children, we found that cortical thickness and surface area differences were predominantly observed in the frontal cortex. Furthermore, a path analysis revealed that a COMT genotype affected abnormal development of the frontal cortex in terms of both cortical thickness and surface area and was associated with working memory changes in children with ADHD. Our study confirms that the role of COMT in ADHD is not restricted to the development of behavior but may also affect the cortical thickness and surface area. Thus, our findings may help to improve the understanding of the neuroanatomic basis for the relationship between the COMT genotype and ADHD pathogenesis.

Novel, non-nitrocatechol catechol-O-methyltransferase inhibitors modulate dopamine neurotransmission in the frontal cortex and improve cognitive flexibility

RATIONALE

Cognitive impairment is a primary feature of many neuropsychiatric disorders and there is a need for new therapeutic options. Catechol-O-methyltransferase (COMT) inhibitors modulate cortical dopaminergic function and have been proposed as potential cognitive enhancers. Unfortunately, currently available COMT inhibitors are not good candidates due to either poor blood-brain barrier penetration or severe toxicity.

OBJECTIVES

To address the need for safe, brain-penetrant COMT inhibitors, we tested multiple novel compounds in a set of preclinical in vivo efficacy assays in rats to determine their ability to inhibit COMT function and viability as potential clinical candidates.

METHODS

We measured the change in concentration of dopamine (DA) metabolites in cerebrospinal fluid (CSF) from the cisterna magna and extracellular fluid (ECF) from the frontal cortex produced by our novel compounds. Additionally, we tested the effects of our brain-penetrant COMT inhibitors in an attentional set-shifting assay (ASST). We benchmarked the performance of the novel COMT inhibitors to the effects produced by the known COMT inhibitor tolcapone.

RESULTS

We found that multiple COMT inhibitors, exemplified by LIBD-1 and LIBD-3, significantly modulated dopaminergic function measured as decreases in homovanillic acid (HVA) and increases in 3,4-Dihydroxyphenylacetic acid (DOPAC), two DA metabolites, in CSF and the frontal cortex. Additionally, we found that LIBD-1 significantly improved cognitive flexibility in the ASST, an effect previously reported following tolcapone administration.

CONCLUSIONS

These results demonstrate that LIBD-1 is a novel COMT inhibitor with promising in vivo activity and the potential to serve as a new therapy for cognitive impairment.

Interaction between catechol-O-methyltransferase polymorphism and childhood trauma in suicidal ideation of patients with post-traumatic stress disorder

INTRODUCTION

Suicidal behavior of post-traumatic stress disorder (PTSD) patients is influenced by genetic and environmental factors. The catechol-O-methyltransferase (COMT) gene has been known to be associated with suicidal ideation. The present study aimed to explore the relationship of COMT polymorphism, childhood trauma, and suicidal ideation in patients with PTSD.

METHODS

Fifty patients with PTSD and 62 healthy controls (HCs) were recruited, and COMT variants rs4680 and rs4633 were genotyped through peripheral blood. Psychological assessments such as the childhood trauma questionnaire (CTQ), the scale for suicidal ideation, the clinician-administered PTSD scale for DSM-5, and a PTSD checklist were administered. A regression analysis, the Johnson-Neyman technique, and a two-way analysis of covariance were conducted.

RESULTS

Interaction of COMT polymorphism (rs4680, rs4633) and childhood emotional abuse (subscale of CTQ) predicted suicidal ideation in patients with PTSD. Patients with the rs4680 Val/Val genotype, compared to Met carriers genotype, showed higher suicidal ideation when childhood emotional abuse was high. Patients with the rs4633 CC genotype, compared to T carriers genotype, showed higher suicidal ideation when childhood emotional abuse was high.

CONCLUSION

Our results suggest that vulnerability to suicide could be increased in the Val/Val genotype of COMT rs4680 and the CC genotype of rs4633 in patients with PTSD. Moreover, PTSD group with high childhood emotional abuse demonstrated a significantly higher suicidal ideation than did those with low childhood emotional abuse.

Sex-dimorphic effects of biogenesis of lysosome-related organelles complex-1 deficiency on mouse perinatal brain development

The function(s) of the Biogenesis of Lysosome-related Organelles Complex-1 (BLOC-1) during brain development is to date largely unknown. Here, we investigated how its absence alters the trajectory of postnatal brain development using as model the pallid mouse. Most of the defects observed early postnatally in the mutant mice were more prominent in males than in females and in the hippocampus. Male mutant mice, but not females, had smaller brains as compared to sex-matching wild types at postnatal day 1 (P1), this deficit was largely recovered by P14 and P45. An abnormal cytoarchitecture of the pyramidal cell layer of the hippocampus was observed in P1 pallid male, but not female, or juvenile mice (P45), along with severely decreased expression levels of the radial glial marker Glutamate-Aspartate Transporter. Transcriptomic analyses showed that the overall response to the lack of functional BLOC-1 was more pronounced in hippocampi at P1 than at P45 or in the cerebral cortex. These observations suggest that absence of BLOC-1 renders males more susceptible to perinatal brain maldevelopment and although most abnormalities appear to have been resolved in juvenile animals, still permanent defects may be present, resulting in faulty neuronal circuits, and contribute to previously reported cognitive and behavioral phenotypes in adult BLOC-1-deficient mice.

Enhancing cognition through pharmacological and environmental interventions: Examples from preclinical models of neurodevelopmental disorders

In this review we discuss the role of environmental and pharmacological treatments to enhance cognition with special regards to neurodevelopmental related disorders and aging. How the environment influences brain structure and function, and the interactions between rearing conditions and gene expression, are fundamental questions that are still poorly understood. We propose a model that can explain some of the discrepancies in findings for effects of environmental enrichment on outcome measures. Evidence of a direct causal correlation of nootropics and treatments that enhanced cognition also will be presented, and possible molecular mechanisms that include neurotrophin signaling and downstream pathways underlying these processes are discussed. Finally we review recent findings achieved with a wide set of behavioral and cognitive tasks that have translational validity to humans, and should be useful for future work on devising appropriate therapies. As will be discussed, the collective findings suggest that a combinational therapeutic approach of environmental enrichment and nootropics could be particularly successful for improving learning and memory in both developmental disorders and normal aging.

Neurobiological perspective of 22q11.2 deletion syndrome

22q11.2 deletion syndrome is characterised by a well defined microdeletion that is associated with a high risk of neuropsychiatric disorders, including intellectual disability, schizophrenia, attention-deficit hyperactivity disorder, autism spectrum disorder, anxiety disorders, seizures and epilepsy, and early-onset Parkinson's disease. Preclinical and clinical data reveal substantial variability of the neuropsychiatric phenotype despite the shared underlying deletion in this genetic model. Factors that might explain this variability include genetic background effects, additional rare pathogenic variants, and potential regulatory functions of some genes in the 22q11.2 deletion region. These factors might also be relevant to the pathophysiology of these neuropsychiatric disorders in the general population. We review studies that might provide insight into pathophysiological mechanisms underlying the expression of neuropsychiatric disorders in 22q11.2 deletion syndrome, and potential implications for these common disorders in the general (non-deleted) population. The recurrent hemizygous 22q11.2 deletion, associated with 22q11.2 deletion syndrome, has attracted attention as a genetic model for common neuropsychiatric disorders because of its association with substantially increased risk of such disorders.¹ Studying such a model has many advantages. First, 22q11.2 deletion has been genetically well characterised.² Second, most genes present in the region typically deleted at the 22q11.2 locus are expressed in the brain.^3-5 Third, genetic diagnosis might be made early in life, long before recognisable neuropsychiatric disorders have emerged. Thus, this genetic condition offers a unique opportunity for early intervention, and monitoring individuals with 22q11.2 deletion syndrome throughout life could provide important information on factors contributing to disease risk and protection. Despite the commonly deleted region being shared by about 90% of individuals with 22q11.2 deletion syndrome, neuropsychiatric outcomes are highly variable between individuals and across the lifespan. A clear link remains to be established between genotype and phenotype.^3,5 In this Review, we summarise preclinical and clinical studies investigating biological mechanisms in 22q11.2 deletion syndrome, with a focus on those that might provide insight into mechanisms underlying neuropsychiatric disorders in 22q11.2 deletion syndrome and in the general population.

Meta-Analysis of the Effects of the Catechol-O-Methyltransferase Val158/108Met Polymorphism on Parkinson's Disease Susceptibility and Cognitive Dysfunction

Background: There is a continued debate and inconsistent findings in previous literature about the relationship of catechol-O-methyltransferase (COMT) and Parkinson’s disease (PD) susceptibility as well as cognitive dysfunction. To substantiate this existing gap, we comprehensively examine COMT genotype effects on the development of PD and test the hypothesis that the Met158 allele of the COMT gene is associated with cognitive dysfunction by conducting a meta-analysis review.

Methods: PubMed/MEDLINE, Embase, Cochrane databases search (18/30/08) yielded 49 included studies. Data were extracted by two reviewers and included COMT genotype, publication year, diagnostic status, ancestry, the proportion of male participants, and whether genotype frequencies were consistent with Hardy–Weinberg equilibrium. Unadjusted odds ratios (ORs) were used to derive pooled estimates of PD risk overall and in subgroups defined by ethnicity, gender, and onset of disease. Moreover, the association of certain cognitive domains in PD and COMT gene type was explored. Meta-analyses were performed using random-effect models and p value–based methods. All statistical tests were two-sided. The present study was registered with PROSPERO (CRD42018087323).

Results: In the current studies, we found no association between COMT Val158/108Met polymorphism and PD susceptibility. However, the gender-stratified analyses revealed marginally significant effects in heterozygote model analyses in women (P = 0.053). In addition, stratification according to onset of PD also shows significant effects of COMT Val158/108Met polymorphism on late-onset population both in recessive (P = 0.017) and allelic (P = 0.017) genetic models. For the intelligence quotient (IQ) score and Unified Parkinson Disease Rating Scale III (UPDRS III), there was no evidence for genetic association, except in subgroup analyses in Asian populations (IQ score, P = 0.016; UPDRS III, P < 0.001).

Conclusion: The COMT Val158/108Met polymorphism is associated with the risk for PD in female or late-onset PD. Methionine/methionine carriers of Asian population performed significantly worse than the valine allele carriers in IQ score and UPDRS III.

Identification of a de novo FOXP1 mutation and incidental discovery of inherited genetic variants contributing to a case of autism spectrum disorder and epilepsy

Background

Autism spectrum disorder is commonly co‐diagnosed intellectual disability, language disorder, anxiety, and epilepsy, however, symptom management is difficult due to the complex genetic nature of ASD.

Methods

We present a next‐generation sequencing‐based case study with both de novo and inherited genetic variants and highlight the impact of structural variants on post‐translational regulation of protein expression. Since management of symptoms has classically been through pharmaceutical therapies, a pharmacogenomics screen was also utilized to determine possible drug/gene interactions.

Results

A de novo variant was identified within the FOXP1 3′ untranslated regulatory region using exome sequencing. Additionally, inherited variants that likely contribute to the current and potential future traits were identified within the COMT, SLC6A4, CYP2C19, and CYP2D6 genes.

Conclusion

This study aims to elucidate how a collection of variant genotypes could potentially impact neural development resulting in a unique phenotype including ASD and epilepsy. Each gene's contribution to neural development is assessed, and the interplay of these genotypes is discussed. The results highlight the utility of exome sequencing in conjunction with pharmacogenomics screening when evaluating possible causes of and therapeutic treatments for ASD‐related symptoms.

Deletion of Autism Risk Gene Shank3 Disrupts Prefrontal Connectivity

Mutations in the synaptic scaffolding protein SHANK3 are a major cause of autism and are associated with prominent intellectual and language deficits. However, the neural mechanisms whereby SHANK3 deficiency affects higher-order socio-communicative functions remain unclear. Using high-resolution functional and structural MRI in adult male mice, here we show that loss of Shank3 (Shank3B ^-/-) results in disrupted local and long-range prefrontal and frontostriatal functional connectivity. We document that prefrontal hypoconnectivity is associated with reduced short-range cortical projections density, and reduced gray matter volume. Finally, we show that prefrontal disconnectivity is predictive of social communication deficits, as assessed with ultrasound vocalization recordings. Collectively, our results reveal a critical role of SHANK3 in the development of prefrontal anatomy and function, and suggest that SHANK3 deficiency may predispose to intellectual disability and socio-communicative impairments via dysregulation of higher-order cortical connectivity.SIGNIFICANCE STATEMENT Mutations in the synaptic scaffolding protein SHANK3 are commonly associated with autism, intellectual, and language deficits. Previous research has linked SHANK3 deficiency to basal ganglia dysfunction, motor stereotypies, and social deficits. However, the neural mechanism whereby Shank3 gene mutations affects cortical functional connectivity and higher-order socio-communicative functions remain unclear. Here we show that loss of SHANK3 in mice results in largely disrupted functional connectivity and abnormal gray matter anatomy in prefrontal areas. We also show that prefrontal connectivity disruption is tightly linked to socio-communicative deficits. Our findings suggest that SHANK3 is a critical orchestrator of frontocortical function, and that disrupted connectivity of prefrontal areas may underpin socio-communicative impairments observed in SHANK3 mutation carriers.

Frontoparietal cortical thickness mediates the effect of COMT Val158Met polymorphism on age-associated executive function

Proper dopamine (DA) signaling is likely necessary for maintaining optimal cognitive performance as we age, particularly in prefrontal-parietal networks and in fronto-striatal networks. Thus, reduced DA availability is a salient risk factor for accelerated cognitive aging. A common polymorphism that affects DA D1 receptor dopamine availability, COMT Val158Met (rs4680), influences enzymatic breakdown of DA, with COMT Val carriers having a 3- to 4-fold reduction in synaptic DA compared to COMT Met carriers. Furthermore, dopamine receptors and postsynaptic availability are drastically reduced with aging, as is executive function performance that ostensibly relies on these pathways. Here, we investigated in 176 individuals aged 20-94 years whether: (1) COMT Val carriers differ from their Met counterparts in thickness of regional cortices receiving D1 receptor pathways: prefrontal, parietal, cingulate cortices; (2) this gene-brain association differs across the adult lifespan; and (3) COMT-related regional thinning evidences cognitive consequences. We found that COMT Val carriers evidenced thinner cortex in prefrontal, parietal, and posterior cingulate cortices than COMT Met carriers and this effect was not age-dependent. Further, we demonstrate that thickness of these regions significantly mediates the effect of COMT genotype on an executive function composite measure. These results suggest that poorer executive function performance is due partly to thinner association cortex in dopaminergic-rich regions, and particularly so in individuals who are genetically predisposed to lower postsynaptic dopamine availability, regardless of age.

The COMT Val158Met Polymorphism and Reaction to a Transgression: Findings of Genetic Associations in Both Chinese and German Samples

After a transgression, people often either tend to avoid the transgressor or seek revenge. These tendencies can be investigated via a trait approach and surprisingly little is known about their biological underpinnings. One promising candidate gene polymorphism, which may influence individual differences in avoidance of a transgressor and vengefulness, is the COMT Val158Met (rs4680) polymorphism known to affect dopaminergic signaling and among others brain activity in situations in which people punish others for their behavior. We therefore investigated the molecular genetics of individual differences in Avoidance Motivation and vengefulness with a focus on this polymorphism. Possible genetic associations were first investigated in a sample of N = 730 Chinese participants (n = 196 females) using buccal cells to extract the DNA for genotyping. To replicate the findings we carried out a parallelized investigation in a sample of N = 585 German participants (n = 399 females). Chinese and German versions of the TRIM-12 and the Vengeance Scale were implemented to assess individual differences in tendencies to react to a transgression. Results show that Met allele carriers of the COMT Val158Met polymorphism (Val/Met and Met/Met) score significantly higher on the tendency to avoid a transgressor in the Chinese male and female samples, with an especially pronounced effect in the female subgroup. The same effect could be found in the German sample, again especially in females. Additionally, carrying a Met allele was associated with higher vengefulness in the Chinese sample only, especially in males. The present findings indicate that the COMT Val158Met polymorphism might influence individual differences in the motivation to avoid transgressors across cultures, especially in females. However, its association with vengefulness seems to be more complex and may exhibit some cultural and gender specific effects.

Haplotypic and Genotypic Association of Catechol-O-Methyltransferase rs4680 and rs4818 Polymorphisms and Treatment Resistance in Schizophrenia

Treatment-resistant schizophrenia (TRS) continues to be a challenge. It was related to different factors, including alterations in the activity of brain dopaminergic system, which could be influenced by the dopamine-degrading enzyme, catechol-O-methyltransferase (COMT). Variants of the COMT gene have been extensively studied as risk factors for schizophrenia; however, their association with TRS has been poorly investigated. The aim of the present study was to determine the haplotypic and genotypic association of COMT rs4680 and rs4818 polymorphisms with the presence of TRS. Overall, 931 Caucasian patients diagnosed with schizophrenia (386 females and 545 males) were included, while 270 participants met the criteria for TRS. In males, no significant haplotypic and genotypic associations between COMT rs4680 and rs4818 polymorphisms and TRS were detected. However, genotypic analyses demonstrated higher frequency of COMT rs4680 AA genotype carriers compared to G-allele carriers (p = 0.033) and higher frequency of COMT rs4818 CC genotype carriers than G-allele carriers (p = 0.014) in females with TRS. Haplotype analyses confirmed that the presence of the G allele in females was associated with lower risk of TRS. In women with TRS, the high activity G-G/G-G haplotype was rare, while carriers of other haplotypes were overrepresented (p = 0.009). Such associations of COMT rs4680 and rs4818 high-activity (G variants), as well as G-G/G-G haplotype, with the lower risk of TRS in females, but not in males, suggest significant, but sex-specific influence of COMT variants on the development of treatment-resistance in patients with schizophrenia. However, due to relatively low number of females, those findings require replication in a larger sample.

Remote memories are enhanced by COMT activity through dysregulation of the endocannabinoid system in the prefrontal cortex

The prefrontal cortex (PFC) is a crucial hub for the flexible modulation of recent memories (executive functions) as well as for the stable organization of remote memories. Dopamine in the PFC is implicated in both these processes and genetic variants affecting its neurotransmission might control the unique balance between cognitive stability and flexibility present in each individual. Functional genetic variants in the catechol-O-methyltransferase (COMT) gene result in a different catabolism of dopamine in the PFC. However, despite the established role played by COMT genetic variation in executive functions, its impact on remote memory formation and recall is still poorly explored. Here we report that transgenic mice overexpressing the human COMT-Val gene (COMT-Val-tg) present exaggerated remote memories (>50 days) while having unaltered recent memories (<24 h). COMT selectively and reversibly modulated the recall of remote memories as silencing COMT Val overexpression starting from 30 days after the initial aversive conditioning normalized remote memories. COMT genetic overactivity produced a selective overdrive of the endocannabinoid system within the PFC, but not in the striatum and hippocampus, which was associated with enhanced remote memories. Indeed, acute pharmacological blockade of CB1 receptors was sufficient to rescue the altered remote memory recall in COMT-Val-tg mice and increased PFC dopamine levels. These results demonstrate that COMT genetic variations modulate the retrieval of remote memories through the dysregulation of the endocannabinoid system in the PFC.

The divergent impact of catechol-O-methyltransferase (COMT) Val158Met genetic polymorphisms on executive function in adolescents with discrete patterns of childhood adversity

PURPOSE

Catechol-O-methyltransferase (COMT) Val¹⁵⁸Met functional polymorphisms play a crucial role in the development of executive function (EF), but their effect may be moderated by environmental factors such as childhood adversity. The present study aimed at testing the divergent impact of the COMT Val¹⁵⁸Met genotype on EF in non-clinical adolescents with discrete patterns of childhood adversity.

METHODS

A total of 341 participants completed the Childhood Trauma Questionnaire, the self-reported version of the Behavior Rating Inventory of Executive Function, and self-administered questionnaires on familial function. The participants' COMT Val¹⁵⁸Met genotype was determined. Associations among the variables were explored using latent class analysis and general linear models.

RESULTS

We found that Val/Val homozygotes showed significantly worse performance on behavioral shift, relative to Met allele carriers (F=5.921, p=0.015, Partial η²=0.018). Moreover, three typical patterns of childhood adversity, namely, low childhood adversity (23.5%), childhood neglect (59.8%), and high childhood adversity (16.7%), were found. Both childhood neglect and high childhood adversity had a negative impact on each aspect of EF and on global EF performance. Importantly, these results provided evidence for significant interaction effects, as adolescents with the Val/Val genotype showed inferior behavioral shift performance than Met carriers (F=6.647, p=0.010, Partial η²=0.020) in the presence of high childhood adversity. Furthermore, there were no differences between the genotypes for childhood neglect and low childhood adversity.

CONCLUSIONS

Overall, this is the first study to show that an interaction between the COMT genotype and childhood adversity affects EF in non-clinical adolescents. These results suggest that the COMT genotype may operate as a susceptibility gene vulnerable to an adverse environment.

Sex-specific attenuation of impulsive action by progesterone in a go/no-go task for cocaine in rats

RATIONALE

Previous work indicated that progesterone (PRO) reduced impulsive choice for cocaine in female but not male rats (Smethells et al. Psychopharmacology 233:2999-3008, 2016). Impulsive action, typically measured by responding for a reinforcer during a signaled period of nonavailability of natural reinforcers, predicts initiation and escalation of drug use in animals and humans. The present study examined impulsive action for cocaine using PRO in male and female rats trained on a go/no-go task.

OBJECTIVE

Rats were trained on a go/no-go task to respond for cocaine infusions (0.4 mg/kg/inf). During the "go" component, responding was reinforced on a VI 30-s schedule, whereas during the "no-go" component, withholding a response was reinforced on a differential reinforcement of other behavior (DRO) 30-s schedule. A response during the no-go component resets the DRO timer and served as a measure of impulsive action. After baseline responding was established, rats were pretreated with vehicle (VEH) or PRO (0.5 mg/kg), and DRO resets and responding during the go component for cocaine were compared in males vs. females.

RESULTS

DRO resets were significantly lower following PRO treatment compared to VEH in female, but not male, rats. Response rates and overall infusions during the go component were not significantly altered by PRO in either females or males.

CONCLUSION

Treatment with PRO resulted in a sex-specific reduction in impulsive action for cocaine, while not affecting cocaine self-administration.

Sex-specific effects of COMT Val158Met polymorphism on corpus callosum structure: A whole-brain diffusion-weighted imaging study

BACKGROUND

Genetic polymorphisms play a significant role in determining brain morphology, including white matter structure and may thus influence the development of brain functions. The main objective of this study was to examine the effect of Val158Met (rs4680) polymorphism of Catechol-O-Methyltransferase (COMT) gene on white matter connectivity in healthy adults.

METHODS

We used a whole-brain diffusion-weighted imaging method with Tract-Based Spatial Statistics (TBSS) analysis to examine white matter structural integrity in intrinsic brain networks on a sample of healthy subjects (N = 82).

RESULTS

Results revealed a sex-specific effect of COMT on corpus callosum (CC): in males only, Val homozygotes had significantly higher fractional anisotropy (FA) compared to Met-carriers. Volume-of-interest analysis showed a genotype by sex interaction on FA in genu and rostral midbody of CC, whereby Val males demonstrated higher FA than Met females.

CONCLUSIONS

These results demonstrate the key effect of genes by sex interaction, rather than their individual contribution, on the corpus callosum anatomy.

Genetically-Driven Enhancement of Dopaminergic Transmission Affects Moral Acceptability in Females but Not in Males: A Pilot Study

Moral behavior has been a key topic of debate for philosophy and psychology for a long time. In recent years, thanks to the development of novel methodologies in cognitive sciences, the question of how we make moral choices has expanded to the study of neurobiological correlates that subtend the mental processes involved in moral behavior. For instance, in vivo brain imaging studies have shown that distinct patterns of brain neural activity, associated with emotional response and cognitive processes, are involved in moral judgment. Moreover, while it is well-known that responses to the same moral dilemmas differ across individuals, to what extent this variability may be rooted in genetics still remains to be understood. As dopamine is a key modulator of neural processes underlying executive functions, we questioned whether genetic polymorphisms associated with decision-making and dopaminergic neurotransmission modulation would contribute to the observed variability in moral judgment. To this aim, we genotyped five genetic variants of the dopaminergic pathway [rs1800955 in the dopamine receptor D4 (DRD4) gene, DRD4 48 bp variable number of tandem repeat (VNTR), solute carrier family 6 member 3 (SLC6A3) 40 bp VNTR, rs4680 in the catechol-O-methyl transferase (COMT) gene, and rs1800497 in the ankyrin repeat and kinase domain containing 1 (ANKK1) gene] in 200 subjects, who were requested to answer 56 moral dilemmas. As these variants are all located in genes belonging to the dopaminergic pathway, they were combined in multilocus genetic profiles for the association analysis. While no individual variant showed any significant effects on moral dilemma responses, the multilocus genetic profile analysis revealed a significant gender-specific influence on human moral acceptability. Specifically, those genotype combinations that improve dopaminergic signaling selectively increased moral acceptability in females, by making their responses to moral dilemmas more similar to those provided by males. As females usually give more emotionally-based answers and engage the "emotional brain" more than males, our results, though preliminary and therefore in need of replication in independent samples, suggest that this increase in dopamine availability enhances the cognitive and reduces the emotional components of moral decision-making in females, thus favoring a more rationally-driven decision process.

Distribution, properties, and inhibitor sensitivity of zebrafish catechol-O-methyl transferases (COMT)

Catechol-O-methyltransferase (COMT; EC 2.1.1.6) is an enzyme with multiple functions in vertebrates. COMT methylates and thus inactivates catecholamine neurotransmitters and metabolizes xenobiotic catechols. Gene polymorphism rs4680 that influences the enzymatic activity of COMT affects cognition and behavior in humans. The zebrafish is widely used as an experimental animal in many areas of biomedical research, but most aspects of COMT function in this species have remained uncharacterized. We hypothesized that both comt genes play essential roles in zebrafish. Both comt-a and comt-b were widely expressed in zebrafish tissues, but their relative abundance varied considerably. Homogenates of zebrafish organs, including the brain, showed enzymatic COMT activity that was the highest in the liver and kidney. Treatment of larval zebrafish with the COMT inhibitor Ro41-0960 shifted the balance of catecholamine metabolic pathways towards increased oxidative metabolism. Whole-body concentrations of dioxyphenylacetic acid (DOPAC), a product of dopamine oxidation, were increased in the inhibitor-treated larvae, although the dopamine levels were unchanged. Thus, COMT is likely to participate in the processing of catecholamine neurotransmitters in the zebrafish, but the inhibition of COMT in larval fish is compensated efficiently and does not have pronounced effects on dopamine levels.

Differential Associations between Cortical Thickness and Striatal Dopamine in Treatment-Naïve Adults with ADHD vs. Healthy Controls

Alterations in catecholamine signaling and cortical morphology have both been implicated in the pathophysiology of attention deficit/hyperactivity disorder (ADHD). However, possible links between the two remain unstudied. Here, we report exploratory analyses of cortical thickness and its relation to striatal dopamine transmission in treatment-naïve adults with ADHD and matched healthy controls. All participants had one magnetic resonance imaging (MRI) and two [¹¹C]raclopride positron emission tomography scans. Associations between frontal cortical thickness and the magnitude of d-amphetamine-induced [¹¹C]raclopride binding changes were observed that were divergent in the two groups. In the healthy controls, a thicker cortex was associated with less dopamine release; in the ADHD participants the converse was seen. The same divergence was seen for baseline D2/3 receptor availability. In healthy volunteers, lower D2/3 receptor availability was associated with a thicker cortex, while in the ADHD group lower baseline D2/3 receptor availability was associated with a thinner cortex. Individual differences in cortical thickness in these regions correlated with ADHD symptom severity. Together, these findings add to the evidence of associations between dopamine transmission and cortical morphology, and suggest that these relationships are altered in treatment-naïve adults with ADHD.

A schizophrenia relevant 5-Choice Serial Reaction Time Task for mice assessing broad monitoring, distractibility and impulsivity

The 5-Choice Serial Reaction Time Task (5-CSRTT) is an automated test for rodents allowing the assessment of multiple cognitive measures. Originally designed to assess cognitive deficits relevant to attention deficit hyperactivity disorder, it has been widely used in the investigation of neural systems of attention. In the current study, we have set up a modified version, which reduced the training phase to only 8-9 days with minimal food deprivation and without single-housing. Furthermore, based on evidence that patients with schizophrenia are more impaired in broad monitoring abilities than in sustained attention, we successfully developed a protocol replicating the Spatial Attentional Resource Allocation Task (SARAT), used in humans to assess broad monitoring. During this task, when the target appeared at a single pre-cued location, mice selectively responded faster. Instead, increasing the number of validly cued locations proportionately decreased accuracy. We then validated a protocol which is relevant for neuropsychiatric disorders in which additional irrelevant pre-cue lights selectively disrupted attention (distractibility). Finally, we improved previously used protocols changing inter-trial intervals from 5 to 7 s by randomly presenting this shift only in 20% of the trials. This resulted in a selective effect on premature responses (impulsivity), with important implications for schizophrenia as well as for other mental disorders. Therefore, this revised 5-CSRTT reduced training and stress on the animals while selectively measuring different cognitive functions with translational validity to schizophrenia and other psychiatric disorders.

Adolescence is the starting point of sex-dichotomous COMT genetic effects

The catechol-o-methyltransferase (COMT) genetic variations produce pleiotropic behavioral/neuroanatomical effects. Some of these effects may vary among sexes. However, the developmental trajectories of COMT-by-sex interactions are unclear. Here we found that extreme COMT reduction, in both humans (22q11.2 deletion syndrome COMT Met) and mice (COMT-/-), was associated to cortical thinning only after puberty and only in females. Molecular biomarkers, such as tyrosine hydroxylase, Akt and neuronal/cellular counting, confirmed that COMT-by-sex divergent effects started to appear at the cortical level during puberty. These biochemical differences were absent in infancy. Finally, developmental cognitive assessment in 22q11DS and COMT knockout mice established that COMT-by-sex-dichotomous effects in executive functions were already apparent in adolescence. These findings uncover that genetic variations severely reducing COMT result in detrimental cortical and cognitive development selectively in females after their sexual maturity. This highlights the importance of taking into account the combined effect of genetics, sex and developmental stage.

Dopamine transporter (DAT) genetic hypofunction in mice produces alterations consistent with ADHD but not schizophrenia or bipolar disorder

ADHD, schizophrenia and bipolar disorder are psychiatric diseases with a strong genetic component which share dopaminergic alterations. Dopamine transporter (DAT) genetics might be potentially implicated in all these disorders. However, in contrast to DAT absence, the effects of DAT hypofunction especially in developmental trajectories have been scarcely addressed. Thus, we comprehensively studied DAT hypofunctional mice (DAT+/-) from adolescence to adulthood to disentangle DAT-dependent alterations in the development of psychiatric-relevant phenotypes. From pre-adolescence onward, DAT+/- displayed a hyperactive phenotype, while responses to external stimuli and sensorimotor gating abilities were unaltered. General cognitive impairments in adolescent DAT+/- were partially ameliorated during adulthood in males but not in females. Despite this, attentional and impulsivity deficits were evident in DAT+/- adult males. At the molecular level, DAT+/- mice showed a reduced expression of Homer1a in the prefrontal cortex, while other brain regions as well as Arc and Homer1b expression were mostly unaffected. Amphetamine treatments reverted DAT+/- hyperactivity and rescued cognitive deficits. Moreover, amphetamine shifted DAT-dependent Homer1a altered expression from prefrontal cortex to striatal regions. These behavioral and molecular phenotypes indicate that a genetic-driven DAT hypofunction alters neurodevelopmental trajectories consistent with ADHD, but not with schizophrenia and bipolar disorders.

Modification of COMT-dependent pain sensitivity by psychological stress and sex

Catecholamine-O-methyltransferase (COMT) is a polymorphic gene whose variants affect enzymatic activity and pain sensitivity via adrenergic pathways. Although COMT represents one of the most studied genes in human pain genetics, findings regarding its association with pain phenotypes are not always replicated. Here, we investigated if interactions among functional COMT haplotypes, stress, and sex can modify the effect of COMT genetic variants on pain sensitivity. We tested these interactions in a cross-sectional study, including 2 cohorts, one of 2972 subjects tested for thermal pain sensitivity (Orofacial Pain: Prospective Evaluation and Risk Assessment) and one of 948 subjects with clinical acute pain after motor vehicle collision (post-motor vehicle collision). In both cohorts, the COMT high-pain sensitivity (HPS) haplotype showed robust interaction with stress and number of copies of the HPS haplotype was positively associated with pain sensitivity in nonstressed individuals, but not in stressed individuals. In the post-motor vehicle collision cohort, there was additional modification by sex: the HPS-stress interaction was apparent in males, but not in females. In summary, our findings indicate that stress and sex should be evaluated in association studies aiming to investigate the effect of COMT genetic variants on pain sensitivity.

Influence of COMT Val158Met polymorphism on emotional decision-making: A sex-dependent relationship?

The biological underpinnings of sex-related differences in decision-making are still under-explored. The COMT gene is related to sexual dimorphism and with different choices made under uncertainty, albeit no study has specifically investigated a moderation effect of sex on the association between the COMT gene and the performance on decision-making paradigms. In this study, we investigated the influence of the COMT Val¹⁵⁸Met polymorphism on Iowa Gambling Task (IGT) performance depending on sex in a healthy adult sample. Participants were 192 healthy adults (84 men and 108 women). The first 40 choices in the IGT were considered decisions under ambiguity and the last 60 choices decisions under risk. To test our moderation hypothesis we used a separate regressions approach. The results revealed a sex-dependent effect of COMT Va l¹⁵⁸Met polymorphism on decision-making as measured by the IGT. Val/Val women showed the best performance in the last trials of the IGT. Therefore, the COMT Val¹⁵⁸Met polymorphism may be considered a genetic marker underlying sex differences in decision-making.

Effects of Omega-3 Fatty Acid Supplementation on Cognitive Functions and Neural Substrates: A Voxel-Based Morphometry Study in Aged Mice

Human and experimental studies have revealed putative neuroprotective and pro-cognitive effects of omega-3 polyunsaturated fatty acids (n-3 PUFA) in aging, evidencing positive correlations between peripheral n-3 PUFA levels and regional grey matter (GM) volume, as well as negative correlations between dietary n-3 PUFA levels and cognitive deficits. We recently showed that n-3 PUFA supplemented aged mice exhibit better hippocampal-dependent mnesic functions, along with enhanced cellular plasticity and reduced neurodegeneration, thus supporting a role of n-3 PUFA supplementation in preventing cognitive decline during aging. To corroborate these initial results and develop new evidence on the effects of n-3 PUFA supplementation on brain substrates at macro-scale level, here we expanded behavioral analyses to the emotional domain (anxiety and coping skills), and carried out a fine-grained regional GM volumetric mapping by using high-resolution MRI-based voxel-based morphometry. The behavioral effects of 8 week n-3 PUFA supplementation were measured on cognitive (discriminative, spatial and social) and emotional (anxiety and coping) abilities of aged (19 month-old at the onset of study) C57B6/J mice. n-3 PUFA supplemented mice showed better mnesic performances as well as increased active coping skills. Importantly, these effects were associated with enlarged regional hippocampal, retrosplenial and prefrontal GM volumes, and with increased post mortem n-3 PUFA brain levels. These findings indicate that increased dietary n-3 PUFA intake in normal aging can improve fronto-hippocampal GM structure and function, an effect present also when the supplementation starts at late age. Our data are consistent with a protective role of n-3 PUFA supplementation in counteracting cognitive decline, emotional dysfunctions and brain atrophy.

Modulative effects of COMT haplotype on age-related associations with brain morphology

Catechol-O-methyltransferase (COMT), located on chromosome 22q11.2, encodes an enzyme critical for dopamine flux in the prefrontal cortex. Genetic variants of COMT have been suggested to functionally manipulate prefrontal morphology and function in healthy adults. This study aims to investigate modulative roles of individuals COMT SNPs (rs737865, val158met, rs165599) and its haplotypes in age-related brain morphology using an Asian sample with 174 adults aged from 21 to 80 years. We showed an age-related decline in cortical thickness of the dorsal visual pathway, including the left dorsolateral prefrontal cortex, bilateral angular gyrus, right superior frontal cortex, and age-related shape compression in the basal ganglia as a function of the genotypes of the individual COMT SNPs, especially COMT val158met. Using haplotype trend regression analysis, COMT haplotype probabilities were estimated and further revealed an age-related decline in cortical thickness in the default mode network (DMN), including the posterior cingulate, precuneus, supramarginal and paracentral cortex, and the ventral visual system, including the occipital cortex and left inferior temporal cortex, as a function of the COMT haplotype. Our results provided new evidence on an antagonistic pleiotropic effect in COMT, suggesting that genetically programmed neural benefits in early life may have a potential bearing towards neural susceptibility in later life. Hum Brain Mapp 37:2068-2082, 2016. © 2016 Wiley Periodicals, Inc.

Sex-dichotomous effects of functional COMT genetic variations on cognitive functions disappear after menopause in both health and schizophrenia

Different genetic variations in the catechol-O-methyltransferase (COMT) gene have been indicated to functionally regulate the encoded enzyme. Despite the vast literature on the single nucleotide COMT ValMet polymorphism, the impact of complex haplotypes on cognitive functions has been overlooked. Here we contrasted the effects of complex COMT haplotypes with the ValMet polymorphism on cognitive functions and their interaction with menopause, in healthy subjects and patients with schizophrenia. Healthy adults (N=229) as well as patients with schizophrenia (N=172) underwent a comprehensive cognitive assessment taking into account the menopausal state. Functional COMT variations selectively modulated working memory and executive functions. Strikingly, these effects were present only in adult men but not in women before menopause, in both healthy subjects and patients with schizophrenia. Importantly, the same pattern of COMT-dependent effects present in men reappeared in women after menopause. Thus, functional COMT mutations seem to modulate cognitive functions depending on the hormonal status. These data clarify the importance of taking into account the combined effect of sex, hormonal status and genetics.

The impact of Val108/158Met polymorphism of catechol-O-methyltransferase on brain oscillations during working memory

This study investigated whether catechol-O-methyltransferase (COMT) Val/Met polymorphism was associated with variation in event-related desynchronization/synchronization (ERD/ERS) of responses during working memory (WM). 11 Val/Val and 11 Met/Met homozygous participants underwent magnetoencephalography (MEG) while performing a WM task. In contrast to small effects behaviourally, during the delay period Val/Val individuals showed lower ERS in the gamma band (Hz 30-50) in frontal regions, increased ERS in the alpha band (Hz 8-12) in the right frontal and parietal regions and increased ERD in the beta band (Hz 14-30) in the left fronto-temporal regions as compared with Met/Met homozygous individuals. During the response period Val/Val participants showed greater beta ERD in the prefrontal and parietotemporal regions. These results demonstrate that COMT genotype has a strong impact on brain responses (oscillatory activity) during WM performance likely a consequence of compensatory activity during the delay and response periods.

Both the COMT Val158Met single-nucleotide polymorphism and sex-dependent differences influence response inhibition

Reactive and proactive controls of actions are cognitive abilities that allow one to deal with a continuously changing environment by adjusting already programmed actions. They also set forthcoming actions by evaluating the outcome of the previous ones. Earlier studies highlighted sex-related differences in the strategies and in the pattern of brain activation during cognitive tasks involving reactive and proactive control. To further identify sex-dependent characteristics in the cognitive control of actions, in this study, we have assessed whether/how differences in performance are modulated by the COMT Val158Met single-nucleotide polymorphism (SNP), a genetic factor known to influence the functionality of the dopaminergic system-in particular, at the level of the prefrontal cortex. Two groups of male and female participants were sorted according to their genotype (Val/Val, Val/Met, and Met/Met) and tested in a stop signal task, a consolidated tool for measuring executive control in experimental and clinical settings. In each group of participants, we estimated both a measure of the capacity to react to unexpected events and the ability to monitor their performance. The between-group comparison of these measures indicated a poorer ability of male individuals and Val/Val subjects in error-monitoring. These observations suggest that sex differences in inhibitory control could be influenced by the efficiency of COMT and that other sex-specific factors have to be considered. Understanding the inter-group variability of behavioral and physiological correlates of cognitive control could provide more accurate diagnostic tools for predicting the incidence and/or the development of pathologies, like ADHD, or deviant behaviors, such as drug or alcohol abuse.

Modulating effect of COMT Val(158)Met polymorphism on interference resolution during a working memory task

Genetic variability related to the catechol-O-methyltransferase (COMT) gene has received increasing attention in the last 15years, in particular as a potential modulator of the neural substrates underlying inhibitory processes and updating in working memory (WM). In an event-related functional magnetic resonance imaging (fMRI) study, we administered a modified version of the Sternberg probe recency task (Sternberg, 1966) to 43 young healthy volunteers, varying the level of interference across successive items. The task was divided into two parts (high vs. low interference) to induce either proactive or reactive control processes. The participants were separated into three groups according to their COMT Val(158)Met genotype [Val/Val (VV); Val/Met (VM); Met/Met (MM)]. The general aim of the study was to determine whether COMT polymorphism has a modulating effect on the neural substrates of interference resolution during WM processing. Results indicate that interfering trials were associated with greater involvement of frontal cortices (bilateral medial frontal gyrus, left precentral and superior frontal gyri, right inferior frontal gyrus) in VV homozygous subjects (by comparison to Met allele carriers) only in the proactive condition of the task. In addition, analysis of peristimulus haemodynamic responses (PSTH) revealed that the genotype-related difference observed in the left SFG was specifically driven by a larger increase in activity from the storage to the recognition phase of the interfering trials in VV homozygous subjects. These results confirm the impact of COMT genotype on inhibitory processes during a WM task, with an advantage for Met allele carriers. Interestingly, this impact on frontal areas is present only when the level of interference is high, and especially during the transition from storage to recognition in the left superior frontal gyrus.