Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Schizophrenia has complex genetic heritability. It is also genetically heterogeneous. To the extent that genes are associated with symptom constellations in schizophrenia, they do so by affecting the development and function of neural systems that mediate the expression of such diverse behavioral, cognitive and perceptual phenomena. The genetic mechanisms of human brain dysfunction remain to be well understood. "Imaging genetics" is an emerging field that attempts to integrate the basic biology of putative disease mechanisms with physiological correlates from the live human brain. Here, we review recent imaging genetics work on prefrontal brain systems associated with working memory and executive function - heritable traits relevant to schizophrenia. Starting with genetic variation in dopaminergic systems (e.g., COMT), we examined the modulation of prefrontal brain networks during active cognitive processing; there is also evidence that variation in the expression of dopamine-related downstream intra-cellular signaling molecules (e.g., AKT1) are implicated. Moreover, these genetic variants evidence epistasis on neuroimaging measures, lending further support to the conceptualization that non-additive combinations of multiple genes modulate active human cognitive brain mechanisms. The imaging genetics platform therefore could extend understanding of genetic mechanisms of human cognitive brain processes relevant to neuropsychiatric disease.
 ...
PMID:Prefrontal cognitive systems in schizophrenia: towards human genetic brain mechanisms. 1963 31

22q11.2 deletion syndrome (22q11DS) is associated with an increased susceptibility to develop schizophrenia. Despite a large body of literature documenting abnormal brain structure in 22q11DS, cerebral changes associated with brain maturation in 22q11DS remained largely unexplored. To map cortical maturation from childhood to adulthood in 22q11.2 deletion syndrome, we used cerebral MRI from 59 patients with 22q11DS, aged 6 to 40, and 80 typically developing controls; three year follow-up assessments were also available for 32 patients and 31 matched controls. Cross-sectional cortical thickness trajectories during childhood and adolescence were approximated in age bins. Repeated-measures were also conducted with the longitudinal data. Within the group of patients with 22q11DS, exploratory measures of cortical thickness differences related to COMT polymorphism, IQ, and schizophrenia were also conducted. We observed deviant trajectories of cortical thickness changes with age in patients with 22q11DS. In affected preadolescents, larger prefrontal thickness was observed compared to age-matched controls. Afterward, we observed greater cortical loss in 22q11DS with a convergence of cortical thickness values by the end of adolescence. No compelling evidence for an effect of COMT polymorphism on cortical maturation was observed. Within 22q11DS, significant differences in cortical thickness were related to cognitive level in children and adolescents, and to schizophrenia in adults. Deviant trajectories of cortical thickness from childhood to adulthood provide strong in vivo cues for a defect in the programmed synaptic elimination, which in turn may explain the susceptibility of patients with 22q11DS to develop psychosis.
 ...
PMID:Deviant trajectories of cortical maturation in 22q11.2 deletion syndrome (22q11DS): a cross-sectional and longitudinal study. 1983 27

Velo-cardio-facial syndrome (VCFS) is caused by a micro-deletion of over 40 genes at the q11.2 locus of chromosome 22 and is a risk factor for the development of schizophrenia and other psychiatric disorders. COMT, one of the genes located in the deleted region, has been considered as a major candidate gene for genetic susceptibility in psychiatric diseases. Its functional polymorphism Val108/158Met has been shown to affect prefrontal function and working memory and has been associated with emotional dysregulation. We utilized a functional magnetic resonance imaging (fMRI) event-related paradigm to asses COMT genotype and gender-moderated effects on the neural activation that are elicited by viewing emotionally salient images charged with pleasant, unpleasant, and neutral content. Since estrogen down-regulates COMT activity resulting in lower COMT activity in women than men, we hypothesized an allele-by-gender interaction effect on neural activation. Participants included 43 VCFS individuals (Val/male=9, Val/female=17, Met/male=9, Met/female=8). We observed a gender effect on processing positive emotions, in that girls activated the cingulate gyrus more than boys did. We further observed a significant gender-by-allele interaction effect on neural function specific to the frontal lobe during the processing of pleasant stimuli, and specific to limbic regions during the processing of unpleasant stimuli. Our results suggest that in VCFS, the effect of the COMT Val108/158Met polymorphism is moderated by gender during the processing of emotional stimuli and could contribute to the understanding of the way in which this COMT polymorphism affects vulnerability to neuropsychiatric disorders.
 ...
PMID:The effects of gender and catechol O-methyltransferase (COMT) Val108/158Met polymorphism on emotion regulation in velo-cardio-facial syndrome (22q11.2 deletion syndrome): An fMRI study. 2012 31

The 22q11.2 deletion syndrome (22qDS) and schizophrenia have genetic and neuropsychological similarities, but are likely to differ in memory profile. Confirming differences in memory function between the two disorders, and identifying their genetic determinants, can help to define genetic subtypes in both syndromes, identify genetic risk factors for the emergence of psychosis, and develop pharmacological interventions for cognitive dysfunction. However, no study has compared memory function between 22qDS and schizophrenia, while indirect comparisons are confounded by marked differences in IQ between the two populations. We compared verbal and visual memory in 29 children and adolescents with 22qDS and 15 intellectually matched youths with schizophrenia using age-appropriate, directly comparable, Wechsler scales. Verbal memory was markedly superior in the 22qDS group by 21 points. There were no group differences in visual memory. The inherently low COMT activity in 22qDS merits investigation as a potential protective factor for verbal memory.
 ...
PMID:Memory in intellectually matched groups of young participants with 22q11.2 deletion syndrome and those with schizophrenia. 2030 54

The Val158Met polymorphism in the COMT gene has been found to be associated with differences in brain activation in both healthy subjects and patients with schizophrenia. The predominant finding has been increased prefrontal activation associated with the Val allele; however, genotype-related de-activations have not been studied. In this study 42 schizophrenia patients and 31 controls underwent fMRI while performing the n-back task. Brain differences related to presence/absence of disease and presence/absence of the Val/Val genotype were examined. Both disease and Val/Val genotype were associated with failure of de-activation in a cluster centred in the medial prefrontal cortex. There was no interaction between disease and genotype at this location, but clusters where there were significant interactions emerged in the right prefrontal cortex and left temporal/parietal cortex. These findings suggest that Val158Met polymorphism influences task-related de-activations in the default mode network in both healthy subjects and schizophrenia patients to an equivalent extent. However the Val158Met polymorphism also has disease-specific effects on DLPFC activation in schizophrenia.
 ...
PMID:COMT Val158Met polymorphism in relation to activation and de-activation in the prefrontal cortex: A study in patients with schizophrenia and healthy subjects. 2039 74

New models of interaction between genetic and environmental factors have been proposed to explain the pathogenesis of schizophrenia. The Val158Met polymorphism of the COMT (Catechol-O-Methyltransferase) gene, involved in dopamine regulation and related to negative symptoms, has been previously thought to interact with cannabis use in the modulation of risk of psychosis. The aim of the study was to explore the existence of an interaction between COMT genotype and cannabis use in early stages of psychosis and its effects on the age of onset in a representative group of first-episode psychosis patients. Age of onset, DUP (Duration of Untreated Psychosis) and cannabis use (regular user versus sporadic or non-user) were assessed in 169 Caucasian patients with a first-episode schizophrenia spectrum disorder. COMT polymorphism was typed using PCR of the relevant region followed by digestion with NlaIII and electrophoresis. A multivariate ANCOVA was performed with DUP and age of onset as dependent variables, cannabis and the COMT genotype as fixed factors, and gender as a covariate. The MANCOVA was significant for age of onset and DUP. Cannabis users had a significant earlier age of onset. Age of onset was later in the Met homozygote group (non-significant). The cannabis-COMT interaction showed a significant effect on both DUP and age of onset. Post hoc analyses showed that differences between genotypes were only present in the non-users' group. Based on these results, the use of cannabis could exert a modulator effect on the genotype, suppressing the delay effect for the age of onset in the case of the Met allele patients.
 ...
PMID:Catechol-O-Methyltransferase (COMT) Val158Met variations and cannabis use in first-episode non-affective psychosis: clinical-onset implications. 2049 36

The aim of the present study was to investigate possible associations between schizophrenia and 13 SNP markers in COMT. No association was observed in 631 cases, 207 nuclear families, and 776 controls. A cognitive performance phenotype (Trail Marking Test) was available for a subgroup of the patients. No association was found between the 13 markers and this phenotype. Four clinically-defined subgroups (early age at onset, negative symptoms, family history of schizophrenia, and life-time major depressive episode) were also investigated. Associations were observed for 3 of these subgroups, although none withstood correction for multiple testing. COMT does not appear to be a risk factor for schizophrenia in this population.
 ...
PMID:The catechol-O-methyl transferase (COMT) gene and its potential association with schizophrenia: findings from a large German case-control and family-based sample. 2064 32

The primary objective of the current prospective study was to examine developmental patterns of voxel-by-voxel gray and white matter volumes (GMV, WMV, respectively) that would predict psychosis in adolescents with 22q11.2 deletion syndrome (22q11.2DS), the most common known genetic risk factor for schizophrenia. We performed a longitudinal voxel-based morphometry analysis using structural T1 MRI scans from 19 individuals with 22q11.2DS and 18 typically developing individuals. In 22q11.2DS, univariate analysis showed that greater reduction in left dorsal prefrontal cortical (dPFC) GMV over time predicted greater psychotic symptoms at Time2. This dPFC region also showed significantly reduced volumes in 22q11.2DS compared to typically developing individuals at Time1 and 2, greater reduction over time in 22q11.2DS COMT(Met) compared to COMT(Val), and greater reduction in those with greater decline in verbal IQ over time. Leave-one-out Multivariate pattern analysis results (MVPA) on the other hand, showed that patterns of GM and WM morphometric changes over time in regions including but not limited to the dPFC predicted risk for psychotic symptoms (94.7-100% accuracy) significantly better than using univariate analysis (63.1%). Additional predictive brain regions included medial PFC and dorsal cingulum. This longitudinal prospective study shows novel evidence of morphometric spatial patterns predicting the development of psychotic symptoms in 22q11.2DS, and further elucidates the abnormal maturational processes in 22q11.2DS. The use of neuroimaging using MVPA may hold promise to predict outcome in a variety of neuropsychiatric disorders.
 ...
PMID:Developmental changes in multivariate neuroanatomical patterns that predict risk for psychosis in 22q11.2 deletion syndrome. 2081 3

Cannabis use is one of the environmental factors with more solid evidence contributing to schizophrenia risk, especially in genetically susceptible individuals. One of the genes that may interact with cannabis is COMT, although available data are scarce. Here, we present a case-only study of the putative COMT-cannabis interaction in schizophrenia. Two Spanish samples from Santiago de Compostela and Valencia were screened for cannabis use. One hundred and fifty five individuals from a total of 748 patients were identified as cannabis users. Five SNPs in COMT, defining three common functional haplotypes with different enzymatic activities, were genotyped and analyzed for association at the SNP, haplotype and genotype levels. An association was detected between cannabis use and low activity variants (P<0.01) in the joint analysis and results were consistent between the two samples. Schizophrenic subjects homozygous for the Met allele at rs4680 doubled the probability of lifetime prevalence of cannabis use in comparison to Val homozygous (Mantel-Haenszel OR=2.07, 95% CI: 1.27-3.26, P=0.0031, in the combined sample). These data are in contrast to those from Caspi et al. (Biol. Psychiatry 57 (2005)1117-1127) who found association between schizophrenia/schizophreniform disorder and homozygosity at the high activity Val variant of rs4680. The results of our study are discussed in the context of previous findings, suggesting the involvement of COMT polymorphisms in the association between cannabis use and schizophrenia as well as the existence of additional factors mediating this association. However, further research is needed to confirm the COMT-cannabis interaction.
 ...
PMID:Interaction between COMT haplotypes and cannabis in schizophrenia: a case-only study in two samples from Spain. 2131 May 91

Although the etiology of aggression is multifactorial, many studies have associated the Val158Met polymorphism of the COMT with aggression in schizophrenia. This study tests the hypothesis that Met/Met patients display more episodes of aggression and violent behaviour than Val/Val patients in a 6 year follow-up cohort of subjects with schizophrenia in contact with the South-Verona Community-based Mental Health Service. Out of the 141 subjects with an ICD-10 SCAN-confirmed diagnosis of schizophrenia, 115 completed both baseline and follow-up assessments (81.6% of the baseline cohort). Of these, 80 subjects (70%) were genotyped and rated for aggression using the Overt Aggression Scale. Met/Met homozygous patients had higher aggressive behaviour compared to Val/Val homozygous subjects. Antipsychotic dosage, alcohol and drug abuse were taken into account as confounders. The Met/Met genotype of COMT may have an effect on aggressive behaviour in schizophrenia because norepinephrine is less effectively inactivated.
 ...
PMID:Effect of COMT genotype on aggressive behaviour in a community cohort of schizophrenic patients. 2140 25


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>