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Expression data from early symptomatic Sca1154Q/2Q and Sca7266Q/5Q knock-in cerebellum

ABSTRACT: Comparative analysis of cerebellar gene expression changes occurring in Sca1154Q/2Q and Sca7266Q/5Q knock-in mice Polyglutamine diseases are inherited neurodegenerative disorders caused by expansion of CAG repeats encoding a glutamine tract in the disease-causing proteins. There are nine disorders each having distinct features but also clinical and pathological similarities. In particular, spinocerebellar ataxia type 1 and type 7 (SCA1 and SCA7) patients manifest cerebellar ataxia with degeneration of Purkinje cells. To determine whether the disorders share molecular pathogenic events, we studied two mouse models of SCA1 and SCA7 that express the glutamine-expanded protein from the respective endogenous loci. We found common transcriptional changes, with down-regulation of Insulin-like growth factor binding protein 5 (Igfbp5) representing one of the most robust changes. Igfbp5 down-regulation occurred in granule neurons through a non-cell autonomous mechanism and was concomitant with activation of of the Insulin-like growth factor (IGF) pathway and the type I IGF receptor on Purkinje cells. These data define one common pathogenic response in SCA1 and SCA7 and reveal the importance of intercellular mechanisms in their pathogenesis. Given that SCA1 and SCA7 share a cerebellar degenerative phenotype, we proposed that some shared molecular changes might occur in both diseases, and that common molecular alterations could pinpoint pathways that could be targeted to modulate or monitor the pathogenesis of more than one disease. We focused on transcriptional changes because both ATXN1 and ATXN7 play roles in transcriptional regulation and transcriptional defects can be detected in early-symptomatic stages of both SCA1 and SCA7 mouse models. To test our hypothesis, we examined cerebellar gene expression patterns in SCA1 and SCA7 knock-in (KI) models--Sca1154Q/2Q and Sca7266Q/5Q mice. Keywords: comparative disesae state analysis between Sca1154Q/2Q and Sca7266Q/5Q knock-in cerebellum

ORGANISM(S): Mus musculus

PROVIDER: GSE9914 | GEO | 2007/12/18

SECONDARY ACCESSION(S): PRJNA103907

REPOSITORIES: GEO

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Project description:Comparative analysis of cerebellar gene expression changes occurring in Sca1154Q/2Q and Sca7266Q/5Q knock-in mice; Polyglutamine diseases are inherited neurodegenerative disorders caused by expansion of CAG repeats encoding a glutamine tract in the disease-causing proteins. There are nine disorders each having distinct features but also clinical and pathological similarities. In particular, spinocerebellar ataxia type 1 and type 7 (SCA1 and SCA7) patients manifest cerebellar ataxia with degeneration of Purkinje cells. To determine whether the disorders share molecular pathogenic events, we studied two mouse models of SCA1 and SCA7 that express the glutamine-expanded protein from the respective endogenous loci. We found common transcriptional changes, with down-regulation of Insulin-like growth factor binding protein 5 (Igfbp5) representing one of the most robust changes. Igfbp5 down-regulation occurred in granule neurons through a non-cell autonomous mechanism and was concomitant with activation of of the Insulin-like growth factor (IGF) pathway and the type I IGF receptor on Purkinje cells. These data define one common pathogenic response in SCA1 and SCA7 and reveal the importance of intercellular mechanisms in their pathogenesis. Given that SCA1 and SCA7 share a cerebellar degenerative phenotype, we proposed that some shared molecular changes might occur in both diseases, and that common molecular alterations could pinpoint pathways that could be targeted to modulate or monitor the pathogenesis of more than one disease. We focused on transcriptional changes because both ATXN1 and ATXN7 play roles in transcriptional regulation and transcriptional defects can be detected in early-symptomatic stages of both SCA1 and SCA7 mouse models. To test our hypothesis, we examined cerebellar gene expression patterns in SCA1 and SCA7 knock-in (KI) models--Sca1154Q/2Q and Sca7266Q/5Q mice. Experiment Overall Design: Total cerebellar RNA samples were collected from Sca1154Q/2Q knock-in and wild type mice at the early symptomatic disease stage (4 weeks, n=3 knock-in and 3 wild type; 9-12 weeks, n=3 knock-in and 3 wild type). In parallel experiments, total cerebellar RNA samples were collected from Sca7266Q/5Q knock-in and wild type mice also at the early symptomatic disease stage (5 weeks, n=5 knock-in and 5 wild type).

Project description:Spinocerebellar ataxia type 6 (SCA6) is a dominantly inherited neurodegenerative disease caused by an expansion of a CAG repeat encoding a polyglutamine (PolyQ) tract in the Cav2.1 voltage-gated calcium channel. Pathologically, it is characterized by selective degeneration of cerebellar Purkinje cells (PCs), which are a common target for PolyQ-induced toxicity among several different SCAs. Mutant Cav2.1 confers toxicity mainly through a toxic gain-of-function mechanism, but subcellular site of expanded Cav2.1 toxicity is controversial and it remains elusive whether SCA6 shares pathogenic cascades with other SCAs. To gain insight into these problems, we studied the cerebellar gene expression patterns of young Sca6 MPI 118Q/118Q knockin (KI) mice, which express mutant Cav2.1 from endogenous locus and faithfully models human SCA6. Comparison of transcriptional changes with those of Sca1 154Q/2Q mice, a faithful KI mouse model of SCA1, revealed that transcriptional signatures in the MPI 118Q/118Q were distinct from those of Sca1 154Q/2Q. Examination of temporal profiles of candidate genes showed that upregulation of those associated with microglial activation was initiated before PC degeneration was apparent and augmented as the disease progressed. Histological analysis of the MPI 118Q/118Q cerebellum confirmed the presence of Iba-1 positive activated microglia. Moreover, predominance of M1-like pro-inflammatory microglia was observed and was concomitant with the increased expression of pro-inflammatory cytokines. These results suggest that the unique transcriptional response, which highlights upregulation of neuroinflammatory genes possibly associated with lysosomal involvement, may play a pivotal role in the pathogenesis. Modulation of innate immune system could pave the way for slowing the progression of SCA6. We used MPI 118Q/118Q and MPI 11Q/11Q mice for Sca6 KI model at six weeks old. Statistical analysis of differently expressed genes was performed using the Linear Models for Microarray Data (limma) package in R/Bioconductor.

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Expression data from early symptomatic Sca1154Q/2Q and Sca7266Q/5Q knock-in cerebellum

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