Effects of a Functional COMT Polymorphism on Prefrontal Cognitive Function in Patients With 22q11.2 Deletion Syndrome

Children's Hospital of Philadelphia, Department of Child Development, USA.
American Journal of Psychiatry (Impact Factor: 12.3). 10/2004; 161(9):1700-2. DOI: 10.1176/appi.ajp.161.9.1700
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The 22q11.2 deletion syndrome (DiGeorge/velocardiofacial syndrome) is associated with attentional problems and executive dysfunction, and is one of the highest known risk factors for schizophrenia. These behavioral manifestations of 22q11.2 deletion syndrome could result from haploinsufficiency of the catechol O-methyltransferase (COMT) gene, located within the 22q11 region. The goal of the present study was to examine COMT genotype as a predictor of prefrontal cognitive function in patients with 22q11.2 deletion syndrome.
Patients with confirmed 22q11.2 deletions (N=44) underwent neurocognitive testing following Val(158)Met genotyping (Met hemizygous: N=16; Val hemizygous: N=28).
Analyses of covariance revealed that Met-hemizygous patients performed significantly better on a composite measure of executive function (comprising set-shifting, verbal fluency, attention, and working memory) than did Val-hemizygous patients.
These data are consistent with those of previous studies in normal individuals, suggesting that a functional genetic polymorphism in the 22q11 region may influence prefrontal cognition in individuals with COMT haploinsufficiency.

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Available from: Abbas F Jawad, Oct 06, 2015
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    • "Previous studies of COMT genotype in 22q11.2DS have yielded differential results, with some studies reporting Met hemizygosity of COMT to be related to poorer outcome on tasks requiring executive control (Baker et al., 2005; Takarae et al., 2009), and others reporting better outcomes (Bearden et al., 2004; Shashi et al., 2006). Additional studies have found no relationship between COMT genotype and measures of cognitive control in 22q11.2DS "
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    ABSTRACT: Chromosome 22q11.2 Deletion Syndrome (22q11.2DS) is caused by the most common human microdeletion, and it is associated with cognitive impairments across many domains. While impairments in cognitive control have been described in children with 22q11.2DS, the nature and development of these impairments are not clear. Children with 22q11.2DS and typically developing children (TD) were tested on four well-validated tasks aimed at measuring specific foundational components of cognitive control: response inhibition, cognitive flexibility, and working memory. Molecular assays were also conducted in order to examine genotype of catechol-O-methyltransferase (COMT), a gene located within the deleted region in 22q11.2DS and hypothesized to play a role in cognitive control. Mixed model regression analyses were used to examine group differences, as well as age-related effects on cognitive control component processes in a cross-sectional analysis. Regression models with COMT genotype were also conducted in order to examine potential effects of the different variants of the gene. Response inhibition, cognitive flexibility, and working memory were impaired in children with 22q11.2DS relative to TD children, even after accounting for global intellectual functioning (as measured by full-scale IQ). When compared with TD individuals, children with 22q11.2DS demonstrated atypical age-related patterns of response inhibition and cognitive flexibility. Both groups demonstrated typical age-related associations with working memory. The results of this cross-sectional analysis suggest a specific aberration in the development of systems mediating response inhibition in a sub-set of children with 22q11.2DS. It will be important to follow up with longitudinal analyses to directly examine these developmental trajectories, and correlate neurocognitive variables with clinical and adaptive outcome measures.
    Frontiers in Psychology 06/2014; 5:566. DOI:10.3389/fpsyg.2014.00566 · 2.80 Impact Factor
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    • "Similar results were reported by Shashi et al. (2006) and Bearden et al. (2004): Met-hemizygous 22q11.2DS children outperformed Val carriers on a composite measure of EF. "
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    ABSTRACT: The 22q11.2 deletion syndrome (22q11.2DS) carries the highest genetic risk factor for the development of schizophrenia. We investigated the association of genetic variants in two schizophrenia candidate genes with executive function (EF) and IQ in 22q11.2DS individuals. Ninety two individuals with 22q11.2 deletion were studied for the genetic association between COMT and PRODH variants and EF and IQ. Subjects were divided into children (under 12 years old), adolescents (between 12 and 18 years old) and adults (older than 18 years), and genotyped for the COMT Val158Met (rs4680) and PRODH Arg185Trp (rs4819756) polymorphisms. The participants underwent psychiatric evaluation and EF assessment. Our main finding is a significant influence of the COMT Val158Met polymorphism on both IQ and EF performance. Specifically, 22q11.2DS subjects with Met allele displayed higher IQ scores in all age groups compared to Val carriers, reaching significance in both adolescents and adults. The Met allele carriers performed better than Val carriers in EF tasks, being statistically significant in the adult group. PRODH Arg185Trp variant did not affect IQ or EF in our 22q11.2DS cohort. In conclusion, functional COMT variant, but not PRODH, affects IQ and EF in 22q11.2DS subjects during neurodevelopment with a maximal effect at adulthood. Future studies should monitor the cognitive performance of the same individuals from childhood to old age.
    Journal of Psychiatric Research 05/2014; 56(1). DOI:10.1016/j.jpsychires.2014.04.019 · 3.96 Impact Factor
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    • "The COMT gene is located on chromosome 22q11.2, in the 1.5 Mb microdeletion region and encodes for a postsynaptic enzyme implicated in dopamine degradation,61 especially in the prefrontal cortex (PFC), where wide neuronal expression is found, particularly within layers II, III, and IV of the PFC.5,62,63 Here, COMT catalyzes the transfer of a methyl group from S-adenosylmethionine to a hydroxyl group on a catechol nucleus (such as dopamine, norepinephrine, or catechol estrogen).64 "
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    ABSTRACT: The 22q11.2 deletion syndrome (22q11DS) is caused by an autosomal dominant microdeletion of chromosome 22 at the long arm (q) 11.2 band. The 22q11DS is among the most clinically variable syndromes, with more than 180 features related with the deletion, and is associated with an increased risk of psychiatric disorders, accounting for up to 1%-2% of schizophrenia cases. In recent years, several genes located on chromosome 22q11 have been linked to schizophrenia, including those encoding catechol-O-methyltransferase and proline dehydrogenase, and the interaction between these and other candidate genes in the deleted region is an important area of research. It has been suggested that haploinsufficiency of some genes within the 22q11.2 region may contribute to the characteristic psychiatric phenotype and cognitive functioning of schizophrenia. Moreover, an extensive literature on neuroimaging shows reductions of the volumes of both gray and white matter, and these findings suggest that this reduction may be predictive of increased risk of prodromal psychotic symptoms in 22q11DS patients. Experimental and standardized cognitive assessments alongside neuroimaging may be important to identify one or more endophenotypes of schizophrenia, as well as a predictive prodrome that can be preventively treated during childhood and adolescence. In this review, we summarize recent data about the 22q11DS, in particular those addressing the neuropsychiatric and cognitive phenotypes associated with the deletion, underlining the recent advances in the studies about the genetic architecture of the syndrome.
    Neuropsychiatric Disease and Treatment 12/2013; 9:1873-1884. DOI:10.2147/NDT.S52188 · 1.74 Impact Factor
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