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

Several lines of evidence have placed the catechol-O-methyltransferase (COMT) gene in the limelight as a candidate gene for schizophrenia. One of these is its biochemical function in metabolism of catecholamine neurotransmitters; another is the microdeletion, on chromosome 22q11, that includes the COMT gene and causes velocardiofacial syndrome, a syndrome associated with a high rate of psychosis, particularly schizophrenia. The interest in the COMT gene as a candidate risk factor for schizophrenia has led to numerous linkage and association analyses. These, however, have failed to produce any conclusive result. Here we report an efficient approach to gene discovery. The approach consists of (i) a large sample size-to our knowledge, the present study is the largest case-control study performed to date in schizophrenia; (ii) the use of Ashkenazi Jews, a well defined homogeneous population; and (iii) a stepwise procedure in which several single nucleotide polymorphisms (SNPs) are scanned in DNA pools, followed by individual genotyping and haplotype analysis of the relevant SNPs. We found a highly significant association between schizophrenia and a COMT haplotype (P=9.5x10-8). The approach presented can be widely implemented for the genetic dissection of other common diseases.
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PMID:A highly significant association between a COMT haplotype and schizophrenia. 1240 17

Haploinsufficiency syndromes, such as the deletion 22q11, the velo-cardio-facial or DiGeorge/Shprintzen syndrome characterised by chromosome 22q11 deletion, show marked variability in the clinical features. This variability may be due to chance fluctuations in expression of genes in the deleted segment, which tend to have more impact if only one copy of the gene is present. The apparent association between deletion 22q11 and schizophrenia indicates a role for a gene within the deletion in signal transduction in the brain.
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PMID:[Phenotypic variability: genetics and chance--deletion 22q11 and schizophrenia]. 1242 63

We examined whether variation within six genes from the VCFS critical region at 22q11 (DGSC, Stk22A1, DGSI, Gscl, Slc25A1 and Znf74) confers susceptibility to schizophrenia. We screened the exons and flanking intronic sequence of each gene for mutations in 14 individuals with DSM-IV schizophrenia using DHPLC. All polymorphisms identified were characterised and genotyped in a sample of 184 schizophrenics and matched controls, using novel DNA pooling methods. Of the polymorphisms identified, 17 were located within exons, six were within coding sequence, and two were non-synonymous. Pooled genotyping revealed no differences in the allele frequencies for any polymorphism between cases and controls that met our pre-defined criterion (P < or = 0.1). In a complementary approach we also attempted to define the location of a schizophrenia susceptibility locus more precisely by performing association mapping using seven microsatellites spanning the VCFS region with an average inter-marker distance of 450 kb. Conventional chi(2) analysis of genotypes in 368 cases and 368 controls revealed that none of the markers was significantly associated (P < 0.05) with schizophrenia. However, evidence for significant association (P = 0.003) was obtained for D22S944 when alleles were combined. TDT analysis of D22S944 genotyped in a further 278 cases of schizophrenia and their parents failed to find any overall allele-wise significant transmission disequilibrium (chi(2) = 18.3, P = 0.17). However, individual analysis of the alleles revealed that allele 12 was excessively non-transmitted and that this almost reached significance when corrected for multiple alleles (chi(2) = 7.35, P = 0.006, P = 0.078 corrected for 13 alleles).
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PMID:Mutation screening and LD mapping in the VCFS deleted region of chromosome 22q11 in schizophrenia using a novel DNA pooling approach. 1247 24

Schizophrenia or schizoaffective disorders are quite common features in patients with DiGeorge/velocardiofacial syndrome (DGS/VCFS) as a result of hemizygosity of chromosome 22q11.2. We evaluated the PCQAP gene, which maps within the DGS/VCFS interval, as a potential candidate for schizophrenia susceptibility. PCQAP encodes for a subunit of the large multiprotein complex PC2, which exhibits a coactivator function in RNA polymerase II mediated transcription. Using a case-control study, we searched association between schizophrenia and the intragenic coding trinucleotide polymorphism. The distribution of the CAG repeat alleles was significantly different between patients and controls with the Mann-Whitney test (z = -2.5694, P = 0.0051; schizophrenics: n = 378, W = 161,002.5, Mean rank = 425.9325; controls: n = 444, W = 177,250.5, Mean rank = 399.2128). This result may indicate a possible involvement of the multiprotein complex PC2 in schizophrenia susceptibility.
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PMID:Association study between CAG trinucleotide repeats in the PCQAP gene (PC2 glutamine/Q-rich-associated protein) and schizophrenia. 1249 10

The gene encoding catechol-O-methyltransferase (COMT) is a strong candidate for schizophrenia susceptibility, owing to the role of COMT in dopamine metabolism, and the location of the gene within the deleted region in velocardiofacial syndrome, a disorder associated with high rates of schizophrenia. Recently, a highly significant association was reported between schizophrenia and a COMT haplotype in a large case-control sample (Shifman et al. 2002). In addition to a functional valine-->methionine (Val/Met) polymorphism, this haplotype included two noncoding single-nucleotide polymorphisms (SNPs) at either end of the COMT gene. Given the role of COMT in dopamine catabolism and that deletion of 22q11 (containing COMT) is associated with schizophrenia, we postulated that the susceptibility COMT haplotype is associated with low COMT expression. To test this hypothesis, we have applied quantitative measures of allele-specific expression using mRNA from human brain. We demonstrate that COMT is subject to allelic differences in expression in human brain and that the COMT haplotype implicated in schizophrenia (Shifman et al. 2002) is associated with lower expression of COMT mRNA. We also show that the 3' flanking region SNP that gave greatest evidence for association with schizophrenia in that study is transcribed in human brain and exhibits significant differences in allelic expression, with lower relative expression of the associated allele. Our results indicate that COMT variants other than the Val/Met change are of functional importance in human brain and that the haplotype implicated in schizophrenia susceptibility is likely to exert its effect, directly or indirectly, by down-regulating COMT expression.
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PMID:A haplotype implicated in schizophrenia susceptibility is associated with reduced COMT expression in human brain. 1280 84

Deletions at 22q11.2 are linked to DiGeorge or velocardiofacial syndrome (VCFS), whose hallmarks include heart, limb, and craniofacial anomalies, as well as learning disabilities and increased incidence of schizophrenia. To assess the potential contribution of 22q11 genes to cognitive and psychiatric phenotypes, we determined the CNS expression of 32 mouse orthologs of 22q11 genes, primarily in the 1.5-Mb minimal critical region consistently deleted in VCFS. None are uniquely expressed in the developing or adult mouse brain. Instead, 27 are localized in the embryonic forebrain as well as aortic arches, branchial arches, and limb buds. Each continues to be expressed at apparently constant levels in the fetal, postnatal, and adult brain, except for Tbx1, ProDH2, and T10, which increase in adolescence and decline in maturity. At least six 22q11 proteins are seen primarily in subsets of neurons, including some in forebrain regions thought to be altered in schizophrenia. Thus, 22q11 deletion may disrupt expression of multiple genes during development and maturation of neurons and circuits compromised by cognitive and psychiatric disorders associated with VCFS.
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PMID:A comprehensive analysis of 22q11 gene expression in the developing and adult brain. 1461 46

The hypothesis of the existence of one or more schizophrenia susceptibility loci on chromosome 22q is supported by reports of genetic linkage and association, meta-analyses of linkage, and the observation of elevated risk for psychosis in people with velocardiofacial syndrome, caused by 22q11 microdeletions. We tested this hypothesis by evaluating 10 microsatellite markers spanning 22q in a multicenter sample of 779 pedigrees. We also incorporated age at onset and sex into the analysis as covariates. No significant evidence for linkage to schizophrenia or for linkage associated with earlier age at onset, gender, or heterogeneity across sites was observed. We interpret these findings to mean that the population-wide effects of putative 22q schizophrenia susceptibility loci are too weak to detect with linkage analysis even in large samples.
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PMID:Multicenter linkage study of schizophrenia loci on chromosome 22q. 1500 91

Acute phencyclidine induces schizophrenia-like symptoms in healthy humans and psychotic episodes in schizophrenics. Although phencyclidine is known as a N-methyl d-aspartate receptor antagonist (NMDA-R), the molecular events underlying the behavioral symptoms remain largely unknown. Statistical analysis of oligonucleotide microarray data was used to identify phencyclidine-induced alterations in rat cortical gene expression. Acute phencyclidine produced a statistically significant change in 477 genes in rat prefrontal cortex (PFC), a brain area associated with cognitive dysfunction in schizophrenics. Real-time quantitative PCR (RTQ-PCR) confirmed a subset of these changes ranging from -59% to 255% (smallest confirmation: -19%). Subsequent time-course and dose-response studies using RTQ-PCR confirmed and extended the original microarray results. At the molecular level, genes altered by phencyclidine are related to diverse biological processes including stress, inflammatory response, growth and development, neural plasticity and signal transduction. Further analysis, aimed at assessing the relevance of our results to schizophrenia, revealed dysregulation of genes related to: (i) thalamocortical projections, (ii) neurotransmission and neuromodulation, (iii) thyroid hormone activity, (iv) oligodendrocyte linage, (v) brain lipid metabolism, (vi) sleep architecture and (viii) the velocardiofacial syndrome.
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PMID:Phencyclidine-induced changes in rat cortical gene expression identified by microarray analysis: implications for schizophrenia. 1520 79

Segmental aneusomy, which includes chromosome 22 deletion syndrome (del(22)(q11.2q11.2)), has been associated with DiGeorge syndrome (DGS), velocardiofacial syndrome (VCFS), conotruncal anomaly face (CAF) syndrome, cat-eye syndrome (CES), der(22) syndrome, and duplication of the del(22)(q11.2q11.2) syndrome's typically deleted region. Adults with del(22)(q11.2q11.2) may develop psychiatric illnesses, including schizophrenia, schizoaffective disorder, and bipolar disorder, suggesting that lower gene dosage leads to a predisposition to these illnesses. In a bid to identify important regulatory polymorphisms (SNPs) that may emulate changes in gene dosage of the genes within the common deletion, we have analyzed the promoter region of 47 genes (44 of which encode a protein with known function) encoding proteins in and around 22q11 for sequence variants. A total of 33 of the promoters contained polymorphisms. Of those, 25 were cloned into a reporter gene vector, pGL3. The relative ability of each promoter haplotype to promote transcription of the luciferase gene was tested in each of two human cell lines (HEK293t and TE671), using a cotransfected CMV-SPAP plasmid as an internal control. Five genes (PRODH, DGCR14, GSTT2, SERPIND1, and a gene tentatively called DKFZP434P211) showed activity differences between haplotypes of greater than 1.5-fold. Of those, PRODH, which encodes proline dehydrogenase, has previously been highlighted in relation to schizophrenia, and the functional promoter polymorphism reported here may be involved in pathogenic mechanisms.
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PMID:Functional analysis of polymorphisms in the promoter regions of genes on 22q11. 1522 87

This study investigated the morphology of the frontal lobe and the caudate nucleus in velocardiofacial syndrome, a neurogenetic disorder caused by a microdeletion at chromosome 22q11.2 and frequently associated with severe psychiatric disturbances. Volumes of the caudate nucleus and subregions of the frontal lobe were compared on magnetic resonance images of 10 children with velocardiofacial syndrome and 10 age- and gender-matched controls. Frontal deep white matter was reduced significantly (by about 23%) in subjects with velocardiofacial syndrome relative to controls. Frontal and prefrontal volumes were also reduced in subjects with velocardiofacial syndrome, although not disproportionately to whole brain volume. The volume of the right caudate nucleus was increased in children with velocardiofacial syndrome. Associations between right caudate and right frontal regions were noted in controls but not in children with velocardiofacial syndrome. These findings suggest frontostriatal dysfunction in children with velocardiofacial syndrome. Insofar as up to 30% of adults with velocardiofacial syndrome (also known as chromosome 22q11 deletion syndrome) develop schizophrenia and frontostriatal dysfunction has been noted in schizophrenia, the findings support the hypothesis that velocardiofacial syndrome might represent a neurodevelopmental model of schizophrenia.
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PMID:Frontal and caudate alterations in velocardiofacial syndrome (deletion at chromosome 22q11.2). 1522 7


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