Effects of COMT genotype on behavioral symptomatology in the 22q11.2 Deletion Syndrome

Genetics of child aggression, a systematic review

Excessive and persistent aggressiveness is the most common behavioral problem that leads to psychiatric referrals among children. While half of the variance in childhood aggression is attributed to genetic factors, the biological mechanism and the interplay between genes and environment that results in aggression remains elusive. The purpose of this systematic review is to provide an overview of studies examining the genetics of childhood aggression irrespective of psychiatric diagnosis. PubMed, PsycINFO, and MEDLINE databases were searched using predefined search terms for aggression, genes and the specific age group. From the 652 initially yielded studies, eighty-seven studies were systematically extracted for full-text review and for further quality assessment analyses. Findings show that (i) investigation of candidate genes, especially of MAOA (17 studies), DRD4 (13 studies), and COMT (12 studies) continue to dominate the field, although studies using other research designs and methods including genome-wide association and epigenetic studies are increasing, (ii) the published articles tend to be moderate in sizes, with variable methods of assessing aggressive behavior and inconsistent categorizations of tandem repeat variants, resulting in inconclusive findings of genetic main effects, gene-gene, and gene-environment interactions, (iii) the majority of studies are conducted on European, male-only or male-female mixed, participants. To our knowledge, this is the first study to systematically review the effects of genes on youth aggression. To understand the genetic underpinnings of childhood aggression, more research is required with larger, more diverse sample sets, consistent and reliable assessments and standardized definition of the aggression phenotypes. The search for the biological mechanisms underlying child aggression will also benefit from more varied research methods, including epigenetic studies, transcriptomic studies, gene system and genome-wide studies, longitudinal studies that track changes in risk/ameliorating factors and aggression-related outcomes, and studies examining causal mechanisms.

Neuroinflammation and Oxidative Stress in Individuals Affected by DiGeorge Syndrome

DiGeorge syndrome (DGS) is a rare genetic disease caused by microdeletions of the 22q11.2 region (DGS1). A haploinsufficiency at 10p level has been proposed also as a DGS cause (DGS2). Clinical manifestations are variable. The most frequent features are thymic hypoplasia or aplasia with consequent immune deficiency, cardiac malformations, hypoparathyroidism, facial and palatine abnormalities, variable degrees of cognitive impairment and psychiatric disorders. The specific aim of this descriptive report is to discuss the correlation between oxidative stress and neuroinflammation in DGS patients with microdeletions of the 22q11.2 region. The deleted chromosomic region maps various genes involved in mitochondrial metabolisms, such as DGCR8 and TXNRD2, that could lead to reactive oxygen species (ROS) increased production and antioxidant depletion. Furthermore, increased levels of ROS in mitochondria would lead to the destruction of the projection neurons in the cerebral cortex with consequent neurocognitive impairment. Finally, the increase in modified protein belonging to the family of sulfoxide compounds and hexoses, acting as inhibitors of the IV and V mitochondria complex, could result in direct ROS overproduction. Neuroinflammation in DGS individuals could be directly related to the development of the syndrome's characteristic psychiatric and cognitive disorders. In patients with psychotic disorders, the most frequent psychiatric manifestation in DGS, Th-17, Th-1 and Th-2 cells are increased with consequent elevation of proinflammatory cytokine IL-6 and IL1β. In patients with anxiety disorders, both CD3 and CD4 are increased. Some patients with autism spectrum disorders (ASDs) have an augmented level of proinflammatory cytokines IL-12, IL-6 and IL-1β, while IFNγ and the anti-inflammatory cytokine IL-10 seem to be reduced. Other data proposed that altered synaptic plasticity could be directly involved in DGS cognitive disorders. In conclusion, the use of antioxidants for restoring mitochondrial functionality in DGS could be a useful tool to protect cortical connectivity and cognitive behavior.

COMT Val/Met and Psychopathic Traits in Children and Adolescents: A Systematic Review and New Evidence of a Developmental Trajectory toward Psychopathy

Psychopathic traits in youth may lead to adult criminal behaviors/psychopathy. The Val158Met polymorphism of catechol-O-methyltransferase (COMT) may influence the risk for psychopathy-related behaviors, while acting as a biomarker for predicting treatment response to dopaminergic medications. The literature shows inconsistent findings, making the interpretation of COMT's role difficult. The aims of this article are (i) to conduct a systematic review to analyze the effects of COMT Val158Met on psychopathic traits in children and adolescents, and (ii) to present new evidence on the developmental trajectory of the association of Val158Met and youth psychopathic traits. For the systematic review, a literature search was conducted using PubMed, EMBASE, OVID Medline and PsychINFO with the search terms for psychopathic traits, Val158Met and age of interest. In our genotype study, the COMT Val158Met genotype of 293 youth with European ancestry was analyzed in association with the psychopathy-related behavior scores from the Child Behavior Checklist and the Psychopathy Screening Device. To examine the potential influence of developmental changes, the sample was split into at or above and below age 13, and analyses were performed in males and females separately. The literature search yielded twenty-eight articles to be included in the systematic review, which demonstrated mixed results on the association depending on environmental factors, sex ratios, age groups and behavioral disorder diagnoses. The results from our genotype study revealed that Met homozygous youth in the below age 13 group and conversely Val carrier youth in the above age 13 group were more likely to display psychopathic traits. To our knowledge, this is the first study to systematically review the effects of COMT Val158Met on psychopathic traits in childhood and adolescence, and to provide new evidence on the changing effects of Val158Met on psychopathy-related behaviors with development. Elucidating the role of the COMT genotype in conjunction with the child versus adolescent stage of development for psychopathic traits may help predict treatment response, and may lead to early intervention and prevention strategies.

Social behavior in 16p11.2 and 22q11.2 copy number variations: Insights from mice and humans

Genetic 16p11.2 and 22q11.2 deletions and duplications in humans may alter behavioral developmental trajectories increasing the risk of autism and schizophrenia spectrum disorders, and of attention-deficit/hyperactivity disorder. In this review, we will concentrate on 16p11.2 and 22q11.2 deletions' effects on social functioning, beyond diagnostic categorization. We highlight diagnostic and social sub-constructs discrepancies. Notably, we contrast evidence from human studies with social profiling performed in several mouse models mimicking 16p11.2 and 22q11.2 deletion syndromes. Given the complexity of social behavior, there is a need to assess distinct social processes. This will be important to better understand the biology underlying such genetic-dependent dysfunctions, as well as to give perspective on how therapeutic strategies can be improved. Bridges and divergent points between human and mouse studies are highlighted. Overall, we give challenges and future perspectives to sort the genetics of social heterogeneity.

Various Psychiatric Manifestation in DiGeorge Syndrome (22q11.2 Deletion Syndrome): A Case Report

This case report aimed to describe various psychiatric manifestation and treatment course in a patient with DiGeorge syndrome. Psychiatric symptoms and treatment course in a female patient with DiGeorge syndrome were described. This patient showed psychotic symptoms, mood symptoms, and intellectual disability. As well as various psychiatric symptoms, treatment response and sensitivity of side effect by antipsychotics were different from typical characteristics in psychiatric disorders. This case suggests that the genetic defect in DiGeorge syndrome might have a great association with psychiatric problems and response of antipsychotics.

The Role of the Catechol-o-Methyltransferase (COMT) GeneVal158Met in Aggressive Behavior, a Review of Genetic Studies

Aggressive behaviors have become a major public health problem, and early-onset aggression can lead to outcomes such as substance abuse, antisocial personality disorder among other issues. In recent years, there has been an increase in research in the molecular and genetic underpinnings of aggressive behavior, and one of the candidate genes codes for the catechol-O-methyltransferase (COMT). COMT is involved in catabolizing catecholamines such as dopamine. These neurotransmitters appear to be involved in regulating mood which can contribute to aggression. The most common gene variant studied in the COMT gene is the Valine (Val) to Methionine (Met) substitution at codon 158. We will be reviewing the current literature on this gene variant in aggressive behavior.

Aspectos da fluência em tarefa de narrativa oral na síndrome del22q11.2

RESUMO Objetivo Investigar os aspectos da fluência em tarefa de narrativa oral na síndrome del22q11.2 e comparar com indivíduos com desenvolvimento típico de linguagem. Método Participaram deste estudo 15 indivíduos com diagnóstico da síndrome del22q11.2, de ambos os gêneros, com idade cronológica de sete a 17 anos, que foram comparados a 15 indivíduos com desenvolvimento típico de linguagem, semelhantes quanto ao gênero e à idade cronológica. A narrativa oral foi eliciada com o livro Frog Where Are You?, e os aspectos da fluência foram analisados quanto ao tipo e frequência de disfluência (comum e gaga) e velocidade de fala. Foram analisados também o número e a duração das pausas. Os achados foram analisados estatisticamente. Resultados O grupo com a síndrome del22q11.2 apresentou média superior em relação ao grupo sem a síndrome, para a porcentagem de disfluências comuns, principalmente hesitação e revisão. O grupo com a síndrome também apresentou média superior para disfluências gagas, sendo a pausa a disfluência mais frequente. Quanto à velocidade de fala, o grupo com a síndrome apresentou média inferior para o número de palavras e sílabas por minuto. Assim sendo, conclui-se que os indivíduos com a síndrome del22q11.2 apresentaram mais dificuldades para narrar do que os seus pares. Conclusão Os aspectos da fluência investigados foram semelhantes entre os grupo com a síndrome del22q11.2 e com desenvolvimento típico de linguagem quanto à presença de hesitação, revisão e pausa na narrativa oral, porém distinto quanto à frequência dessas disfluências, que foi superior para os indivíduos com a síndrome.

Cognitive phenotype and psychiatric disorder in 22q11.2 deletion syndrome: A review

The behavioural phenotype of 22q11.2 deletion syndrome syndrome (22q11DS), one of the most common human multiple anomaly syndromes, frequently includes intellectual disability (ID) together with high risk of diagnosis of psychotic disorders including schizophrenia. Candidate cognitive endophenotypes include problems with retrieval of contextual information from memory and in executive control and focussing of attention. 22q11DS may offer a model of the relationship between ID and risk of psychiatric disorder. This paper reviews research on the relationship between the cognitive phenotype and the development of psychiatric disorders in 22q11DS. Aspects of cognitive function including verbal I.Q., visual memory, and executive function, are associated with mental health outcome in people with 22q11DS. This relationship may result from a common neurobiological basis for the cognitive difficulties and psychiatric disorders. Some of the cognitive difficulties experienced by people with 22q11DS, especially in attention, memory retrieval, and face processing, may, however, in themselves constitute risk factors for development of hallucinations and paranoid delusions. Future research into factors leading to psychiatric disorder in people with 22q11DS should include assessment of social and psychological factors including life events, symptoms associated with trauma, attachment, and self-esteem, which together with cognitive risk factors may mediate mental health outcome.

Mother-Child Interaction as a Window to a Unique Social Phenotype in 22q11.2 Deletion Syndrome and in Williams Syndrome

Mother-child interactions in 22q11.2 Deletion syndrome (22q11.2DS) and Williams syndrome (WS) were coded for maternal sensitivity/intrusiveness, child's expression of affect, levels of engagement, and dyadic reciprocity. WS children were found to express more positive emotions towards their mothers compared to 22q11.2DS children and those with developmental delay in a conflict interaction. During the same interaction, dyads of 22q11.2DS children were characterized by higher levels of maternal intrusiveness, lower levels of child's engagement and reduced reciprocity compared to dyads of typically developing children. Finally, 22q11.2DS children with the COMT Met allele showed less adaptive behaviors than children with the Val allele. Dyadic behaviors partially coincided with the distinct social phenotypes in these syndromes and are potential behavioral markers of psychopathological trajectory.

COMT and MAO-A polymorphisms and obsessive-compulsive disorder: a family-based association study

Objective

Obsessive-compulsive disorder (OCD) is a common and debilitating psychiatric illness. Although a genetic component contributes to its etiology, no single gene or mechanism has been identified to the OCD susceptibility. The catechol-O-methyltransferase (COMT) and monoamine oxidase A (MAO-A) genes have been investigated in previous OCD studies, but the results are still unclear. More recently, Taylor (2013) in a comprehensive meta-analysis of genetic association studies has identified COMT and MAO-A polymorphisms involved with OCD. In an effort to clarify the role of these two genes in OCD vulnerability, a family-based association investigation was performed as an alternative strategy to the classical case-control design.

Methods

Transmission disequilibrium analyses were performed after genotyping 13 single-nucleotide polymorphisms (eight in COMT and five in MAO-A) in 783 OCD trios (probands and their parents). Four different OCD phenotypes (from narrow to broad OCD definitions) and a SNP x SNP epistasis were also analyzed.

Results

OCD, broad and narrow phenotypes,were not associated with any of the investigated COMT and MAO-A polymorphisms. In addition, the analyses of gene-gene interaction did not show significant epistatic influences on phenotype between COMT and MAO-A.

Conclusions

The findings do not support an association between DSM-IV OCD and the variants of COMT or MAO-A. However, results from this study cannot exclude the contribution of these genes in the manifestation of OCD. The evaluation of broader spectrum phenotypes could help to understand the role of these and other genes in the pathophysiology of OCD and its spectrum disorders.

An fMRI study of facial emotion processing in children and adolescents with 22q11.2 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11DS, velo-cardio-facial syndrome [VCFS]) is a genetic disorder associated with interstitial deletions of chromosome 22q11.2. In addition to high rates of neuropsychiatric disorders, children with 22q11DS have impairments of face processing, as well as IQ-independent deficits in visuoperceptual function and social and abstract reasoning. These face-processing deficits may contribute to the social impairments of 22q11DS. However, their neurobiological basis is poorly understood.

METHODS

We used event-related functional magnetic resonance imaging (fMRI) to examine neural responses when children with 22q11DS (aged 9-17 years) and healthy controls (aged 8-17 years) incidentally processed neutral expressions and mild (50%) and intense (100%) expressions of fear and disgust. We included 28 right-handed children and adolescents: 14 with 22q11DS and 14 healthy (including nine siblings) controls.

RESULTS

Within groups, contrasts showed that individuals significantly activated 'face responsive' areas when viewing neutral faces, including fusiform-extrastriate cortices. Further, within both groups, there was a significant positive linear trend in activation of fusiform-extrastriate cortices and cerebellum to increasing intensities of fear. There were, however, also between-group differences. Children with 22q11DS generally showed reduced activity as compared to controls in brain regions involved in social cognition and emotion processing across emotion types and intensities, including fusiform-extrastriate cortices, anterior cingulate cortex (Brodmann area (BA) 24/32), and superomedial prefrontal cortices (BA 6). Also, an exploratory correlation analysis showed that within 22q11DS children reduced activation was associated with behavioural impairment-social difficulties (measured using the Total Difficulties Score from the Strengths and Difficulties Questionnaire [SDQ]) were significantly negatively correlated with brain activity during fear and disgust processing (respectively) in the left precentral gyrus (BA 4) and in the left fusiform gyrus (FG, BA 19), right lingual gyrus (BA 18), and bilateral cerebellum.

CONCLUSIONS

Regions involved in face processing, including fusiform-extrastriate cortices, anterior cingulate gyri, and superomedial prefrontal cortices (BA 6), are activated by facial expressions of fearful, disgusted, and neutral expressions in children with 22q11DS but generally to a lesser degree than in controls. Hypoactivation in these regions may partly explain the social impairments of children with 22q11DS.

Converging levels of analysis on a genomic hotspot for psychosis: insights from 22q11.2 deletion syndrome

Schizophrenia is a devastating neurodevelopmental disorder that, despite extensive research, still poses a considerable challenge to attempts to unravel its heterogeneity, and the complex biochemical mechanisms by which it arises. While the majority of cases are of unknown etiology, accumulating evidence suggests that rare genetic mutations, such as 22q11.2 Deletion Syndrome (22qDS), can play a significant role in predisposition to the illness. Up to 25% of individuals with 22qDS eventually develop schizophrenia; conversely, this deletion is estimated to account for 1-2% of schizophrenia cases overall. This locus of Chromosome 22q11.2 contains genes that encode for proteins and enzymes involved in regulating neurotransmission, neuronal development, myelination, microRNA processing, and post-translational protein modifications. As a consequence of the deletion, affected individuals exhibit cognitive dysfunction, structural and functional brain abnormalities, and neurodevelopmental anomalies that parallel many of the phenotypic characteristics of schizophrenia. As an illustration of the value of rare, highly penetrant genetic subtypes for elucidating pathological mechanisms of complex neuropsychiatric disorders, we provide here an overview of the cellular, network, and systems-level anomalies found in 22qDS, and review the intriguing evidence for this disorder's association with schizophrenia. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Social skills and associated psychopathology in children with chromosome 22q11.2 deletion syndrome: implications for interventions

BACKGROUND

Although distinctive neuropsychological impairments have been delineated in children with chromosome 22q11 deletion syndrome (22q11DS), social skills and social cognition remain less well-characterised.

OBJECTIVE

To examine social skills and social cognition and their relationship with neuropsychological function/behaviour and psychiatric diagnoses in children with 22q11DS.

METHODS

Sixty-six children with 22q11DS and 54 control participants underwent neuropsychological testing and were administered the Diagnostic Analysis of Non-Verbal Accuracy (DANVA) for face and auditory emotion recognition, a measure of social cognition: their parents/guardians were administered the Social Skills Rating System (SSRS) - parent version, Child Behavior Checklist (CBCL) - parent version and the Computerised Diagnostic Interview Schedule for Children (C-DISC).

RESULTS

The 22q11DS group exhibited significantly lower social skills total score and more problem social behaviours, lower neurocognitive functioning, higher rates of anxiety disorders and more internalising symptoms than the control group. Participants with 22q11DS also exhibited significant deficits in their ability to read facial expressions compared with the control group, but performed no differently than the control participants in the processing of emotions by tone of voice. Within the 22q11DS group, higher social competency was correlated with higher global assessment of functioning and parental socio-economic status. Social competency was worse in those with anxiety disorders, attention deficit hyperactivity disorder, more than two psychiatric diagnoses on the C-DISC and higher internalising symptoms. No significant correlations of SSRS scores were seen with IQ, executive functions, attention, or verbal learning and memory. No correlations were found between social cognition and social skill scores.

CONCLUSION

Our results indicate that social skills in children with 22q11DS are associated with behaviour/emotional functioning and not with neurocognition. Thus, treating the behaviour or emotional problems such as attention deficit hyperactivity disorder and anxiety disorders may provide a pathway for improving social skills in these children.

Preliminary structure and predictive value of attenuated negative symptoms in 22q11.2 deletion syndrome

Current research in schizophrenia suggests that negative symptoms cannot be considered a unitary construct and should be divided in two dimensions: lack of motivation and impoverishment of expression. In addition, negative symptoms are particularly related to decreased daily-life functioning. In the present study, we aimed to replicate these results in a sample of participants with 22q11.2 deletion syndrome (22q11DS), a neurogenetic condition associated with high risk of developing schizophrenia. We also expected to observe an association between the COMT Val/Met polymorphism and negative symptoms. We examined the factorial structure of negative symptoms in a sample of 47 individuals with 22q11DS using the Structured Interview for Prodromal Symptoms (SIPS) and the Positive and Negative Syndrome Scale (PANSS). We also performed stepwise regression analyses to investigate the associations between negative symptoms, adaptive skills and the COMT Val/Met polymorphism. Negative symptoms were explained by a two-factor solution, namely the "amotivation and social withdrawal" and the "emotional withdrawal and expression" dimensions. The motivational dimension was significantly associated with daily-life functioning. Met carriers were rated as experiencing significantly more symptoms of amotivation. The results are interpreted in the light of existing cognitive models in the field of motivation and schizophrenia.

Comprehensive neurocognitive endophenotyping strategies for mouse models of genetic disorders

There is a need for refinement of the current behavioral phenotyping methods for mouse models of genetic disorders. The current approach is to perform a behavioral screen using standardized tasks to define a broad phenotype of the model. This phenotype is then compared to what is known concerning the disorder being modeled. The weakness inherent in this approach is twofold: First, the tasks that make up these standard behavioral screens do not model specific behaviors associated with a given genetic mutation but rather phenotypes affected in various genetic disorders; secondly, these behavioral tasks are insufficiently sensitive to identify subtle phenotypes. An alternate phenotyping strategy is to determine the core behavioral phenotypes of the genetic disorder being studied and develop behavioral tasks to evaluate specific hypotheses concerning the behavioral consequences of the genetic mutation. This approach emphasizes direct comparisons between the mouse and human that facilitate the development of neurobehavioral biomarkers or quantitative outcome measures for studies of genetic disorders across species.

Cognitive phenotype of velocardiofacial syndrome: a review

The behavioural phenotype of velocardiofacial syndrome (VCFS), one of the most common human multiple anomaly syndromes, includes developmental disabilities, frequently including intellectual disability (ID) and high risk of diagnosis of psychotic disorders including schizophrenia. VCFS may offer a model of the relationship between ID and risk of major mental health difficulties. This paper reviews literature on the cognitive phenotype and its relationship with a polymorphism of the gene coding for catechol O-methyltransferase (COMT), a gene haploinsufficient in VCFS which modulates prefrontal dopamine levels. Principal features of the variable cognitive phenotype of VCFS in young people are ID, superiority of verbal over performance I.Q. and verbal over visuospatial memory, and difficulties with number and object magnitude comparisons, time perception and memory for serial order, and orienting of attention. Despite some improvements with age, problems with higher order attentional tasks involving planning persist, possibly modulated by COMT activity levels. Candidate cognitive endophenotypes include problems with retrieval of contextual information from memory and in executive control and focussing of attention. Longitudinal research using common core batteries of psychometric assessments, and experimental measures of cognitive function capable of direct translation for use with animal models, will further advance understanding of the developmental dynamics of VCFS.

Association between polymorphisms in catechol-O-methyltransferase (COMT) and cocaine-induced paranoia in European-American and African-American populations

Catechol-O-methyltransferase (genetic locus, COMT) is a major enzyme involved in catecholamine metabolism and has been associated with numerous psychiatric phenotypes. We studied COMT SNPs and haplotypes in cocaine-induced paranoia (CIP) in African-American (AA) and European-American (EA) populations. We genotyped 17 SNPs across the COMT locus in 319 AA pedigrees (848 individuals) and 302 EA pedigrees (707 individuals). Family-controlled association analyses were conducted using FBAT. We found SNP rs737865 to be nominally significantly associated in the AA family population (P = 0.05). In EAs, the best-known marker, rs4680 (Val158Met), was nominally significant in additive models (P = 0.03). SNP rs174696 also showed nominal significance in additive models (P = 0.02). We considered the three SNPs (rs737866-rs4680-rs174696) together in haplotype analysis in both family populations, using HBAT. The A-A-T haplotype was significantly associated with CIP in EAs (Z = 2.845; P = 0.0044, global P = 0.020). We then studied COMT SNPs in an additional 738 AA and 404 EA unrelated cocaine dependent individuals with and without paranoia. The A-A-T haplotype was significantly associated to CIP in the AA unrelated population (P = 0.0015). Two haplotypes, A-G-C and A-A-C, were significant in the EA unrelated population (P = 0.001 and 0.0003). We also identified rs4680 and three other SNPs, rs933271, rs5993883, and rs740603, as potentially functional variants, as predicted by a signature of positive selection in unrelated EAs and AAs. Based on our robust family-controlled and unrelated-affected analyses, we conclude that COMT is associated with CIP, possibly as a result of its role in the metabolism of dopamine and norepinephrine.

Genetic influence on the working memory circuitry: behavior, structure, function and extensions to illness

Working memory is a highly heritable complex cognitive trait that is critical for a number of higher-level functions. However, the neural substrates of this behavioral phenotype are intricate and it is unknown through what precise biological mechanism variation in working memory is transmitted. In this review we explore different functional and structural components of the working memory circuitry, and the degree to which each of them is contributed to by genetic factors. Specifically, we consider dopaminergic function, glutamatergic function, white matter integrity and gray matter structure all of which provide potential mechanisms for the inheritance of working memory deficits. In addition to discussing the overall heritability of these measures we also address specific genes that may play a role. Each of these heritable components has the potential to uniquely contribute to the working memory deficits observed in genetic disorders, including 22q deletion syndrome, fragile X syndrome, phenylketonuria (PKU), and schizophrenia. By observing the individual contributions of disruptions in different components of the working memory circuitry to behavioral performance, we highlight the concept that there may be many routes to a working memory deficit; even though the same cognitive measure may be a valid endophenotype across different disorders, the underlying cause of, and treatment for, the deficit may differ. This has implications for our understanding of the transmission of working memory deficits in both healthy and disordered populations.

Behavior, brain, and genome in genomic disorders: finding the correspondences

OBJECTIVE

Within the last decade or so, there has been an acceleration of research attempting to connect specific genetic lesions to the patterns of brain structure and activation. This article comments on observations that have been made based on these recent data and discusses their importance for the field of investigations into developmental disorders.

METHODS

In making these observations, the authors focus on one specific genomic lesion, the well-studied, yet still incompletely understood, 22q11.2 deletion syndrome.

RESULTS

The authors demonstrate the degree of variability in the phenotype that occurs at both the brain and behavioral levels of genomic disorders and describe how this variability is, on close inspection, represented at the genomic level.

CONCLUSION

The authors emphasize the importance of combining genetic/genomic analyses and neuroimaging for research and for future clinical diagnostic purposes and for the purposes of developing individualized, patient-tailored treatment and remediation approaches.

COMT and anxiety and cognition in children with chromosome 22q11.2 deletion syndrome

The COMT gene is thought to contribute to the cognitive/psychiatric phenotypes in 22q11.2 deletion syndrome. We measured these manifestations against the Val/Met alleles of the COMT gene, in 40 nonpsychotic 22q11DS children. The Val allele was associated with poor IQ, processing speed, executive function and a higher frequency of anxiety disorders, underscoring the importance of the COMT gene in the childhood psychopathology in 22q11DS.

Executive functions and memory abilities in children with 22q11.2 deletion syndrome

OBJECTIVE

Velo-cardio-facial syndrome or 22q11.2 deletion syndrome (22q11DS) is the most common known microdeletion syndrome. One of the genes in the deleted region is the catechol-O-methyltransferase (COMT) gene, which is thought to have significant effects on cognition through its influence on dopamine metabolism. The aim of the present study was to better characterize the cognitive phenotype in a large cohort children with 22q11DS compared with sibling controls and to investigate if the cognitive deficits in 22q11DS were modulated by COMT expression.

METHOD

The memory, executive function and attentional abilities of children with 22q11DS (n = 50) compared to sibling controls (n = 31), were measured. Also, within children with 22q11DS, a preliminary exploration was carried out of the relationship between cognitive ability and COMT genotype.

RESULTS

Overall, the 22q11DS group had significantly reduced scores on tests of memory (especially in visual memory) and executive function (particularly in planning, working memory, and motor organization) compared with sibling controls. No association, however, was identified between COMT genotype and cognitive function.

CONCLUSIONS

Although 22q11DS children have specific cognitive deficits, differences in COMT do not account for these findings.

Sex differences in the behavior of children with the 22q11 deletion syndrome

High rates of psychiatric impairment in adults with 22q11 deletion syndrome (22q11DS, also referred to as DiGeorge or velocardiofacial syndrome) suggest that behavioral trajectories of children with 22q11DS may provide critical etiologic insights. Past findings that report Diagnostic and Statistical Manual (DSM) diagnoses are extremely variable; moreover, sex differences in behavior have not yet been examined. Child Behavior Checklist (CBCL) ratings from 82 children, including 51 with the 22q11DS and 31 control siblings, were analyzed. Strikingly consistent with rates of psychiatric impairment among affected adults, 25% of children with 22q11DS had high CBCL scores for Total Impairment, and 20% had high CBCL Internalizing Scale scores. Males accounted for 90% of high Internalizing scores and 67% of high Total Impairment scores. Attention and Social Problems were ubiquitous; more affected males than females (23% vs. 4%) scored high on Thought Problems. With regard to CBCL/DSM overlap, 20% of affected males as compared with 0 affected females had one or more high CBCL ratings in the absence of a DSM diagnosis. Behaviors of children with 22q11DS are characterized by marked sex differences when rated dimensionally, with significantly more males experiencing Internalizing and Thought Problems. Categorical diagnoses do not reflect behavioral differences between male and female children with 22q11DS, and may miss significant behavior problems in 20% of affected males.

Neural phenotypes of common and rare genetic variants

Neuroimaging methods offer a powerful way to bridge the gaps between genes, neurobiology and behavior. Such investigations may be further empowered by complementary strategies involving chromosomal abnormalities associated with particular neurobehavioral phenotypes, which can help to localize causative genes and better understand the genetics of complex traits in the general population. Here we review the evidence from studies using these convergent approaches to investigate genetic influences on brain structure: (1) studies of common genetic variations associated with particular neuroanatomic phenotypes, and (2) studies of possible 'genetic subtypes' of neuropsychiatric disorders with very high penetrance, with a focus on neuroimaging studies using novel computational brain mapping algorithms. Finally, we discuss the contribution of behavioral neurogenetics research to our understanding of the genetic basis of neuropsychiatric disorders in the broader population.

Deletion 22q11: spectrum of associated disorders

Velocardiofacial syndrome, also called Shprintzen syndrome or DiGeorge sequence, is one of the most common genetic disorders in humans. Caused by a microdeletion on chromosome 22, it manifests in a remarkable variety of symptoms in multiple systems. The most frequent anomalies involve palatal function, facial features and congenital cardiac defects. In addition, learning disabilities and psychiatric issues are common. The aim of this article is to provide a concise review of the clinical characteristics of this complex disorder. Recognition of the features associated with velocardiofacial syndrome allows for an inclusive diagnosis and more comprehensive care.

Relationship of catechol-O-methyltransferase to schizophrenia and its correlates: evidence for associations and complex interactions

Converging lines of evidence suggest that the gene that codes for catechol-O-methyltransferase (COMT) may play a role in the etiology, neurodevelopment, and expression of schizophrenia. Dopamine dysregulation has long been implicated in schizophrenia pathogenesis, and COMT appears to play a role in dopamine functioning, especially in prefrontal cortex. Additionally, the COMT gene maps to the commonly deleted region on chromosome 22q11 in 22q11 deletion syndrome (22q11DS), a disorder associated with a highly elevated risk for the development of psychosis. An amino acid polymorphism (Val158Met) in the COMT gene affects the activity level of COMT, which affects the levels of available catecholamines in the brain. Val158Met has been found to predict performance on dopamine-mediated prefrontal tasks in healthy adults and patients with schizophrenia. While association and linkage studies have failed to provide conclusive evidence of a strong link between COMT genotype and schizophrenia, evidence linking neural functioning and behavioral output has been somewhat more promising. The present work examines evidence for the role of COMT in schizophrenia pathogenesis, and associations between COMT and cognitive and behavioral correlates of schizophrenia and related disorders. Additionally, evidence for complex interactions involving COMT is examined, including the utility of haplotype analysis and evidence for gene-by-gene and gene-by-environment interactions.

Catechol-O-methyl transferase and expression of schizophrenia in 73 adults with 22q11 deletion syndrome

BACKGROUND

Catechol-O-methyl transferase (COMT) is a candidate gene for schizophrenia with a role in dopamine metabolism, particularly in frontal cortex. COMT is within the region commonly deleted in 22q11 deletion syndrome (22q11DS), a syndrome with high prevalence of schizophrenia. We examined the role of COMT in schizophrenia-related expression in 22q11DS.

METHODS

We genotyped the COMT functional Val(158/108)Met allele in 73 Caucasian adults with 22q11DS (36 men, 37 women; aged 33.8, SD 10.1 years; 37 Met, 36 Val hemizygosity) blind to clinical data and assessed effects on symptoms and frontal functioning.

RESULTS

The lower activity Met allele was not significantly more prevalent than the Val allele in 33 subjects with schizophrenia. Excitement symptoms were more severe, however, and three frontal cognitive tests (theory of mind, Trails B, and olfactory identification), communication, and social functioning measures showed significantly worse performance with Met allele hemizygosity, even after accounting for effects of schizophrenia.

CONCLUSIONS

The results suggest that hemizygosity of the COMT functional allele exerts an effect on some measures of frontal functioning in 22q11DS. Elevated levels of tonic dopamine activation associated with the COMT Met allele may underlie these aspects of expression. We must look elsewhere for causes of the high prevalence of schizophrenia in 22q11DS, however.

Manic symptoms and behavioral dysregulation in youth with velocardiofacial syndrome (22q11.2 deletion syndrome)

Mania and bipolar disorder have been reported in adolescents and adults with velocardiofacial syndrome (VCFS; also known as 22q11.2 deletion syndrome). Children with VCFS have a high prevalence of attention-deficit/hyperactivity disorder (ADHD), which may constitute a risk factor for the eventual development of bipolar disorder in this population. Therefore, we sought to determine whether children with VCFS exhibit more manic symptoms than community controls that also may have learning disorders and ADHD. The study population consisted of 86 children with VCFS and 36 community controls from ages 9 to 15 years, using measures of Young Mania Rating Scale-Parent Version, Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (K-SADS-PL), Child Behavior Checklist (CBCL), and Wechsler Intelligence Scale for Children-3rd edition (WISC-III). The results indicate that manic symptoms were not more prevalent in VCFS than in a community sample of children with learning disorders and ADHD. However, after accounting for symptoms of depression and ADHD, we found that manic symptoms in VCFS predicted uniquely to scores on four Child Behavior Checklist (CBCL) subscales, including anxiety, somatization, thought, and conduct problems. In contrast, manic symptoms in controls predicted uniquely to conduct problems only. Accordingly, our findings of severe behavioral impairment in youth with VCFS and manic symptoms suggest that these children may warrant more intensive monitoring and treatment relative to youth with VCFS and ADHD only.

Animal Models and Human Neuropsychiatric Disorders

Humans have long distinguished themselves from other living organisms. Therefore, to make use of animal models for neuropsychiatric disorders, it is important to acknowledge what has changed historically. Darwin argued that there was continuity in mind between humans and nonhuman species, and animal experimental psychologists and others have debated the existence of consciousness and mentality in animals ever since. Those trained in the associationist tradition sought to eliminate the concept of mind in favor of an empiricial, behavioral approach; others trained in the introspectionist tradition sought to include mental abilities as an integral part of comparative animal psychology. The waning of behaviorism and ascendance of cognitive psychology in the mid-twentieth century renewed interest in the notion of consciousness and mind in nonhuman organisms, particularly as they related to learning impairment and neurobehavioral disorders. Moreover, advances in molecular genetics and technology facilitated development of genetically modified mouse strains that could be used to examine cognitive deficits and psychopathology. However, genetic modifications to individual genes that produce behavioral dysfunction in the mouse have not always provided clear results. In part, this is likely due to the influence of genes in addition to the targeted gene, sometimes resulting in paradoxical effects. I also examine other issues created by the use of nonhuman models of human disorders, including: language, the effect of background genetic strains, genetic-environmental interactions, and the problems associated with the complex genetics needed to produce similarly complex behavioral phenotypes.

A multilevel analysis of cognitive dysfunction and psychopathology associated with chromosome 22q11.2 deletion syndrome in children

We present a multilevel approach to developing potential explanations of cognitive impairments and psychopathologies common to individuals with chromosome 22q11.2 deletion syndrome. Results presented support our hypothesis of posterior parietal dysfunction as a central determinant of characteristic visuospatial and numerical cognitive impairments. Converging data suggest that brain development anomalies, primarily tissue reductions in the posterior brain and changes to the corpus callosum, may affect parietal connectivity. Further findings indicate that dysfunction in "frontal" attention systems may explain some executive cognition impairments observed in affected children, and that there may be links between these domains of cognitive function and some of the serious psychiatric conditions, such as attention-deficit/hyperactivity disorder, autism, and schizophrenia, that have elevated incidence rates in the syndrome. Linking the neural structure and the cognitive processing levels in this way enabled us to develop an elaborate structure/function mapping hypothesis for the impairments that are observed. We show also, that in the case of the catechol-O-methyltransferase gene, a fairly direct relationship between gene expression, cognitive function, and psychopathology exists in the affected population. Beyond that, we introduce the idea that variation in other genes may further explain the phenotypic variation in cognitive function and possibly the anomalies in brain development.