RESUMO
BACKGROUND: Spinocerebellar ataxia type 17 (SCA17) involves the expression of a CAG/CAA expansion mutation in the gene encoding TATA-box binding protein (TBP), a general transcription initiation factor. The spectrum of SCA17 clinical presentation is broad. METHODS: We screened for triplet expansion in the TBP gene in Taiwanese Parkinson's disease (PD), Alzheimer's disease (AD) and atypical parkinsonism and investigated the functional implication of expanded alleles using lymphoblastoid cells as a model. RESULTS: A total of 6 mildly expanded alleles (44-46) were identified in patients group. The frequency of the individuals carrying expanded alleles in PD (3/602 [0.5%]), AD (2/245 [0.8%]) and atypical parkinsonism (1/44 [2.3%]) is not significant as compared to that in the control subjects (0/644 [0.0%]). In lymphoblastoid cells, HSPA5, HSPA8 and HSPB1 expression levels in cells with expanded TBP were significantly lower than that of the control cells. Although not significantly, the levels of PARK7 protein isoforms 6.1 and 6.4 are notably increased in SCA17 lymphoblastoid cells. Treatment of TBH (tert-butyl hydroperoxide) significantly increases cell death in the cells with mildly expanded TBP. CONCLUSIONS: Our findings expand the spectrum of SCA17 phenotype and may contribute to our understanding of the disease.
Assuntos
Doença de Alzheimer/genética , Predisposição Genética para Doença/genética , Doença de Parkinson/genética , Sequências Repetitivas de Ácido Nucleico/genética , Proteína de Ligação a TATA-Box/genética , Expansão das Repetições de Trinucleotídeos/genética , Idoso , Alelos , Doença de Alzheimer/fisiopatologia , Linhagem Celular , Estudos de Coortes , Análise Mutacional de DNA , Chaperona BiP do Retículo Endoplasmático , Feminino , Humanos , Linfócitos/metabolismo , Masculino , Pessoa de Meia-Idade , Mutação , Doença de Parkinson/fisiopatologia , Reação em Cadeia da Polimerase , Sensibilidade e EspecificidadeRESUMO
BACKGROUND: Expansion of the CAG repeat of the TATA-box binding protein (TBP) gene has been identified as the causative mutations in spinocerebellar ataxia 17 (SCA17). TBP is ubiquitously expressed in both central nervous system and peripheral tissues. The underlying molecular changes of SCA17 are rarely explored. METHODS: To study the molecular mechanisms underlying SCA17, we generated stably induced isogenic 293 cells expressing normal TBP-Q(36) and expanded TBP-Q(61) and analyzed the expressed proteins using two-dimensional difference in gel electrophoresis (2D-DIGE), followed by mass spectrometry and immunoblotting. RESULTS: Upon induction with doxycycline, the expanded TBP-Q(61) formed aggregates with significant increase in the cell population at subG1 phase and cleaved caspase-3. Proteomics study identified a total of 16 proteins with expression changes greater than 1.5 fold. Among the 16 proteins, PARK7, GLRX3, HNRNPA1, GINS1, ENO1, HNRPK and NPM1 are increased, and SERPINA5, HSPA5, VCL, KHSRP, HSPA8, HNRPH1, IMMT, VCP and HNRNPL are decreased in cells expressing TBP-Q(61) compared with those expressing TBP-Q(36). The altered expression of HSPA5, HSPA8 and PARK7 were further validated by 2D and Western immunoblot analyses. CONCLUSIONS: The results illustrate the utility of proteomics to identify alterations of proteins which underlie pathogenesis of SCA17, and may serve as potential therapeutic targets.
Assuntos
Fluorescência , Regulação da Expressão Gênica , Proteínas de Choque Térmico HSC70/análise , Proteínas de Choque Térmico/análise , Peptídeos e Proteínas de Sinalização Intracelular/análise , Chaperonas Moleculares/análise , Proteínas Oncogênicas/análise , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismo , Western Blotting , Linhagem Celular , Clonagem Molecular , Eletroforese em Gel Bidimensional , Chaperona BiP do Retículo Endoplasmático , Proteínas de Choque Térmico HSC70/genética , Proteínas de Choque Térmico/genética , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Chaperonas Moleculares/genética , Nucleofosmina , Proteínas Oncogênicas/genética , Fenótipo , Proteína Desglicase DJ-1 , Proteína de Ligação a TATA-Box/genéticaRESUMO
Schizophrenia has a complex and non-Mendelian mode of inheritance. Recently, trinucleotide repeat (TNR)-containing genes have been considered as the candidate genes predisposing to schizophrenia. The purpose of this study was to determine whether a genetic association could be observed between schizophrenia and the TNR polymorphisms within the KLHL1AS/SCA8, PPP2R2B/SCA12, and TBP/SCA17 genes. We studied 100 unrelated schizophrenia patients and 124 controls without evident neurodegenerative or psychiatric disorders. The overall allele frequency distributions of the KLHL1AS/SCA8 and PPP2R2B/SCA12 genes were not significantly different between the schizophrenic patients and the control subjects (P>0.05). The allele frequency distribution in the schizophrenic patients was significantly different from that in the controls at the TBP/SCA17 gene (P=0.0149), with an increased frequency of 36 repeats in the patients and two patients carrying 45 TNR expansions were identified. TBP/SCA17 is the TATA box binding protein gene mapped to chromosome 6q27. The study suggests that TNR expansions of the TBP/SCA17 gene may contribute to the genetic risk of schizophrenia in rare cases.