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)

The expansion of a (CAG)n trinucleotide repeat has been associated with at least eight neurological disorders in which the repeats code for polyglutamine in the protein. To identify additional genes that possess (CAG)n repeats, single-stranded cDNA clones derived from adult human brain were screened using biotinylated oligonucleotide (CAG)8, and the hybridizing complexes were isolated with strepavidin-coated paramagnetic beads. A total of 119 cDNA clones were isolated and initially characterized by end sequencing. BLAST homology searches were used to reduce redundancies with overlapping clones and to eliminate those that show sequence identity with previously published cDNAs with triplet repeats. Only cDNA clones with more than five CAG repeats were pursued for analysis. A total of 19 novel cDNAs were further characterized by determining chromosomal assignments using the Stanford G3 and Genebridge radiation-reduced hybrid mapping panels. Transcript sizes and tissue expression patterns were determined by Northern blot analysis. Two of 19 clones showed specific or high expression in brain. These cDNAs are ideal candidate genes for other neurodegenerative disorders, such as spinocerebellar ataxia types 5 and 7, and may also be implicated in psychiatric diseases such as bipolar affected disorder and schizophrenia.
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PMID:Mapping and characterization of novel (CAG)n repeat cDNAs from adult human brain derived by the oligo capture method. 941 4

Trinucleotide repeat expansions have been shown to cause a number of neurodegenerative diseases. A hallmark of most of these diseases is the presence of anticipation, a decrease in the age at onset in consecutive generations due to the tendency of the unstable trinucleotide repeat to lengthen when passed from one generation to the next. The involvement of trinucleotide repeat expansions in a number of other diseases--including familial spastic paraplegia, schizophrenia, bipolar affective disorder and spinocerebellar ataxia type 7 (SCA7; ref. 10)--is suggested both by the presence of anticipation and by repeat expansion detection (RED) analysis of genomic DNA samples. The involvement of trinucleotide expansions in these diseases, however, can be conclusively confirmed only by the isolation of the expansions present in these populations and detailed analysis to assess each expansion as a possible pathogenic mutation. We describe a novel procedure for quick isolation of expanded trinucleotide repeats and the corresponding flanking nucleotide sequence directly from small amounts of genomic DNA by a process of Repeat Analysis, Pooled Isolation and Detection of individual clones containing expanded trinucleotide repeats (RAPID cloning). We have used this technique to clone the pathogenic SCA7 CAG expansion from an archived DNA sample of an individual affected with ataxia and retinal degeneration.
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PMID:Rapid cloning of expanded trinucleotide repeat sequences from genomic DNA. 942 5

Unstable (CAG)n trinucleotide repeat microsatellites are hypothesized to cause schizophrenia. The (CAG)n microsatellite of dominant spinal cerebellar ataxia type 1 (SCA1) is a candidate schizophrenia gene. Autism results from expansions of (CGG)n and (GAA)n trinucleotide repeat stretches at fragile X syndrome (FRAXA), and the recessive Friedreich's ataxia (FA). Dominant ataxia genes may cause schizophrenia and recessive ataxia genes may cause autism. Syndromes with autism show purine synthesis defects (PSDs) and/or pigmentation defects (PDs). Autism is caused by very lengthy expansions of (CAG)n, (CGG)n and (GAA)n repeats, while schizophrenia results from much smaller (CAG)n and (CGG)n repeat expansions.
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PMID:Expanded (CAG)n, (CGG)n and (GAA)n trinucleotide repeat microsatellites, and mutant purine synthesis and pigmentation genes cause schizophrenia and autism. 979

A combination of clozapine and lithium can be used in the treatment of refractory schizophrenia, schizoaffective disorder and bipolar disorder with rapid cycling. We report a patient with refractory bipolar disorder who developed side-effects after combination therapy with clozapine and lithium at usual therapeutic dosages. Reversible neurotoxicity developed twice during the therapeutic course, once with the restarting of lithium, the other with increasing the dose of lithium, despite the lithium concentrations being less than 0.5 mEq/l. Neurotoxicity manifested as ataxia, coarse tremor, myoclonus, facial spasm and increased deep tendon reflex. While the mechanism causing toxicity is not clear, interaction between the serotonergic effect of clozapine and lithium may be the cause. This report is evidence that a combination of clozapine and lithium may increase the risk of neurotoxicity. We suggest the need to keep clozapine and lithium at lower dosages and closely monitor their side-effects as necessary when these drugs are used concomitantly.
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PMID:Reversible neurotoxicity induced by a combination of clozapine and lithium: a case report. 1022 8

The gene for spinocerebellar ataxia type 1 (SCA1) is a potential candidate gene for schizophrenia because of previous positive linkage findings in this region (6p22-24), and because the reported correlation between SCA1 onset and the number of CAG repeats suggests anticipation. To test the involvement of this gene in the development of schizophrenia, we examined genotypes of the SCA1 CAG repeat polymorphism for 49 Caucasian patients with schizophrenia, and 88 Caucasian controls. We found a significant association between the frequencies of alleles of this gene and schizophrenia (chi 2 = 18.40, df = 8, P = 0.018). Among 13 alleles, one allele (31 trinucleotide repeat) was significantly more frequent in patients with schizophrenia than in controls (chi 2 = 9.57, df = 1, P = 0.002). This association was sustained after applying a Bonferroni correction for multiple testing (P = 0.05/13 = 0.004), and the chi-square results were shown to be robust through Monte Carlo simulation. We observed no allelic association with three flanking microsatellite markers (D6S288, D6S1605, and D6S337), suggesting that our result was not due to population stratification. Further studies of this locus are needed to confirm this finding, and to determine a potential role for this gene in the development of schizophrenia.
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PMID:Possible association between schizophrenia and a CAG repeat polymorphism in the spinocerebellar ataxia type 1 (SCA1) gene on human chromosome 6p23. 1033 46

The P/Q type Ca2+ channel alpha 1-subunit (CACN1A4) gene on chromosome 19p13 is a promising candidate susceptibility locus for schizophrenia. Point mutations in CACN1A4 cause familial hemiplegic migraine and episodic ataxia. Expansion in a coding 3' CAG repeat causes spino-cerebellar ataxia type 6 (SCA6). The mouse mutant phenotype totterer has a form of petit-mal epilepsy. These are neurological conditions, all of which exhibit features in common with schizophrenia. The 19p13 area is also paralogous to other genomic regions of interest in schizophrenia genetics. For these reasons, we performed an association study with the CAG repeat and schizophrenia using 225 Scottish schizophrenia and 198 unrelated Scottish controls. The repeat was not associated with the disorder (P = 0.72) and neither did the schizophrenics have significantly longer alleles than the controls (P = 0.45). We conclude that the SCA6 CAG repeat is not associated with schizophrenia susceptibility. However, it remains possible that other variants in the region could be involved.
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PMID:Association study of the CACN1A4 (SCA6) triplet repeat and schizophrenia. 1041 93

We herein report the findings of an autopsy case of spinocerebellar ataxia type 6 (SCA6) which revealed a mild CAG-repeat expansion in the alpha1A voltage-dependent calcium channel (CACNL1A4) gene on chromosome 19p13. A 39-year-old man who showed slowly progressive mental disorders and gait ataxia was clinically diagnosed to have cortical cerebellar atrophy (CCA) and schizophrenia. None of his relatives revealed any symptoms such as spinocerebellar disease, however, his younger brother had shown some mental disorders. The patient eventually died at 52 years of age, and an autopsy was thus performed. The main histopathological findings included a severe neuronal cell loss of Purkinje cells and inferior olivary nuclei. The number of Purkinje cells in our case had decreased severely in comparison to that in either OPCA or age-matched control cases, and the Purkinje cells in the cerebellar hemisphere were more affected than those in the cerebellar vermis. The neurons of the dentate nucleus and pontine nuclei were well-preserved, and no pathological changes were seen in cerebral cortices or basal ganglia. The clinicopathological findings were similar to those of late cortical cerebellar atrophy (LCCA), Holmes' cortical cerebellar atrophy (Holmes type) or SCA6 cases reported previously. Using genomic DNA extracted from archival paraffin-embedded sections in the frontal lobe, cerebral basal ganglia and cerebellum, the identical mild CAG-repeat expansions in the CACNL1A4/SCA6 gene were revealed in all samples examined. These findings suggest that in cases with LCCA or Holmes type atrophy, we should thus examine the CAG-repeat expansions in the SCA6 gene, and the genomic DNA extracted from paraffin-embedded sections was thus found to be useful in diagnosing SCA6 retrospectively.
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PMID:An autopsy case of spinocerebellar ataxia type 6 with mental symptoms of schizophrenia and dementia. 1044 62

Larger CAG/CTG trinucleotide-repeat tracts in individuals affected with schizophrenia (SCZ) and bipolar affective disorder (BPAD) in comparison with control individuals have previously been reported, implying a possible etiological role for trinucleotide repeats in these diseases. Two unstable CAG/CTG repeats, SEF2-1B and ERDA1, have recently been cloned, and studies indicate that the majority of individuals with large repeats as detected by repeat-expansion detection (RED) have large repeat alleles at these loci. These repeats do not show association of large alleles with either BPAD or SCZ. Using RED, we have identified a BPAD individual with a very large CAG/CTG repeat that is not due to expansion at SEF2-1B or ERDA1. From this individual's DNA, we have cloned a highly polymorphic trinucleotide repeat consisting of (CTA)n (CTG)n, which is very long ( approximately 1,800 bp) in this patient. The repeat region localizes to chromosome 13q21, within 1.2 cM of fragile site FRA13C. Repeat alleles in our sample were unstable in 13 (5.6%) of 231 meioses. Large alleles (>100 repeats) were observed in 14 (1. 25%) of 1,120 patients with psychosis, borderline personality disorder, or juvenile-onset depression and in 5 (.7%) of 710 healthy controls. Very large alleles were also detected for Centre d'Etude Polymorphisme Humaine (CEPH) reference family 1334. This triplet expansion has recently been reported to be the cause of spinocerebellar ataxia type 8 (SCA8); however, none of our large alleles above the disease threshold occurred in individuals either affected by SCA or with known family history of SCA. The high frequency of large alleles at this locus is inconsistent with the much rarer occurrence of SCA8. Thus, it seems unlikely that expansion alone causes SCA8; other genetic mechanisms may be necessary to explain SCA8 etiology.
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PMID:An unstable trinucleotide-repeat region on chromosome 13 implicated in spinocerebellar ataxia: a common expansion locus. 1071 98

New hopes for cloning susceptibility genes for schizophrenia and bipolar affective disorder followed the discovery of a novel type of DNA mutation, namely unstable DNA. One class of unstable DNA, trinucleotide repeat expansion, is the causal mutation in myotonic dystrophy, fragile X mental retardation, Huntington disease and a number of other rare Mendelian neurological disorders. This finding has led researchers in psychiatric genetics to search for unstable DNA sites as susceptibility factors for schizophrenia and bipolar affective disorder. Increased severity and decreased age at onset of disease in successive generations, known as genetic anticipation, was reported for undifferentiated psychiatric diseases and for myotonic dystrophy early in the twentieth century, but was initially dismissed as the consequence of ascertainment bias. Because unstable DNA was demonstrated to be a molecular substrate for genetic anticipation in the majority of trinucleotide repeat diseases including myotonic dystrophy, many recent studies looking for genetic anticipation have been performed for schizophrenia and bipolar affective disorder with surprisingly consistent positive results. These studies are reviewed, with particular emphasis placed on relevant sampling and statistical considerations, and concerns are raised regarding the interpretation of such studies. In parallel, molecular genetic investigations looking for evidence of trinucleotide repeat expansion in both schizophrenia and bipolar disorder are reviewed. Initial studies of genome-wide trinucleotide repeats using the repeat expansion detection technique suggested possible association of large CAG/CTG repeat tracts with schizophrenia and bipolar affective disorder. More recently, three loci have been identified that contain large, unstable CAG/CTG repeats that occur frequently in the population and seem to account for the majority of large products identified using the repeat expansion detection method. These repeats localize to an intron in transcription factor gene SEF2-1B at 18q21, a site named ERDA1 on 17q21 with no associated coding region, and the 3' end of a gene on 13q21, SCA8, that is believed to be responsible for a form of spinocerebellar ataxia. At present no strong evidence exists that large repeat alleles at either SEF2-1B or ERDA1 are involved in the etiology of schizophrenia or bipolar disorder. Preliminary evidence suggests that large repeat alleles at SCA8 that are non-penetrant for ataxia may be a susceptibility factor for major psychosis. A fourth, but much more infrequently unstable CAG/CTG repeat has been identified within the 5' untranslated region of the gene, MAB21L1, on 13q13. A fifth CAG/CTG repeat locus has been identified within the coding region of an ion transporter, KCNN3 (hSKCa3), on 1q21. Although neither large alleles nor instability have been observed at KCNN3, this repeat locus has been extensively analyzed in association and family studies of major psychosis, with conflicting findings. Studies of polyglutamine containing genes in major psychosis have also shown some intriguing results. These findings, reviewed here, suggest that, although a major role for unstable trinucleotides in psychosis is unlikely, involvement at a more modest level in a minority of cases cannot be excluded, and warrants further investigation.
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PMID:The unstable trinucleotide repeat story of major psychosis. 1081 8

1. Phencyclidine (PCP) is widely used as an animal model of schizophrenia. The aim of this study was to better understand the role of nitric oxide (NO) in the mechanism of action of PCP and to determine whether positive NO modulators may provide a new approach to the treatment of schizophrenia. 2. The effects of the NO donor, sodium nitroprusside (SNP), were studied in PCP-treated rats. Following drug administration, behavioural changes and the expression of c-fos, a metabolic marker of functional pathways in the brain, were simultaneously monitored. 3. Acute PCP (5 mg kg(-1), i. p.) treatment induced a complex behavioural syndrome, consisting of hyperlocomotion, stereotyped behaviours and ataxia. Treatment with SNP (2 - 6 mg kg(-1), i.p.) by itself produced no effect on any behaviour studied but completely abolished PCP-induced behaviour in a dose- and time-dependent manner. 4. PCP had differential regional effects on c-fos expression in rat brain, suggesting regionally different patterns of neuronal activity. The most prominent immunostaining was observed in the cortical regions. Pre-treatment with SNP blocked PCP-induced c-fos expression at doses similar to those that suppress PCP-induced behavioural effects. 5. These results implicate the NO system in the mechanism of action of PCP. The fact that SNP abolished effects of PCP suggests that drugs targeting the glutamate-NO system may represent a novel approach to the treatment of PCP-induced psychosis and schizophrenia.
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PMID:Blockade of phencyclidine-induced effects by a nitric oxide donor. 1088 84


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