Gene and pathways affected by CAG-repeat RNA-based toxicity in Drosophila
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ABSTRACT:
ORGANISM(S): Drosophila melanogaster
PROVIDER: GSE31875 | GEO | 2011/11/22
SECONDARY ACCESSION(S): PRJNA145239
REPOSITORIES: GEO
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Project description:Spinocerebellar ataxia type 3 (SCA3) is one of the polyglutamine (polyQ) diseases, which are caused by a CAG repeat expansion within the coding region of the associated genes. The CAG repeat specifies glutamine, and the expanded polyQ domain with mutation confers dominant toxicity on the protein. Traditionally, studies have focused on protein toxicity in polyQ disease mechanisms. Recent findings, however, demonstrate that the CAG repeat RNA, which encodes the toxic polyQ protein, also contributes to the disease in Drosophila. To provide insight into the nature of the RNA toxicity, we extracted brain-enriched RNA from flies expressing a toxic CAG repeat mRNA (CAG100) and a non-toxic interrupted CAA/G mRNA repeat (CAA/G105) for microarray analysis. This approach identified a set of genes that are differentially expressed specifically in CAG100 flies. Four independent replicates of flies expressing CAG0, CAG100, or CAA/G105 by elav-GAL4 were collected at 3 days. The transgenes are DsRed with either (CAG0) no CAG repeat in the 3'UTR, (CAG100) a CAG repeat of 100 CAGs in the 3'UTR, or (CAA/G105) an interrupted CAA CAG repeat in the 3'UTR (ref: Li et al., Nature 453:1107) The transgenes were adjusted to match in mRNA expression such that CAG0 flies had one copy of the transgene, CAG100 flies had 5 copies, and CAA/G105 had two copies. Fly brain tissue (about 20 brains per sample, dissected from head capsule, eyes, lamina and outer medulla removed) was dissected in cold phosphate buffered saline (PBS) and stored in Trizol reagent (Invitrogen Corporation, Carlsbad, CA) at -80Ë?C. Total brain RNA was extracted and purified using TRIzol reagent (Invitrogen) and the RNeasy Mini system (Qiagen), and treated with RNase-free DNase I (Qiagen). To define genes whose expression is altered in response to a toxic CAG repeat RNA, we compared CAG100 flies with age-matched flies expressing CAG0. To exclude transcriptional changes in response to a non-toxic trinucleotide repeat, a second gene list was generated by comparing CAA/G105 flies with age-matched CAG0 flies.
2011-11-22 | E-GEOD-31875 | biostudies-arrayexpress
Project description:Transcription profiles were obtained for 2-month old mice containing an expanded or normal CAG trinucleotide repeat in the coding region for TATA-binding protein (TBP). Three different genotypes were used : TBP-13Q (normal), TBP-71Q (71 repeats), and TBP-105Q (105 repeats). Two lines of TBP-71Q (lines 16 and 27) were used in these experiments. <br><br> The 71Q and 105Q mice express a mutant version of the protein (TBP) and faithfully model the disease SCA17 (spinocerebellar ataxia-17, huntington disease-like 4, HDL4). <br><br> The constructs containing mixed CAG/CAA trinucleotide repeats (and encoding polyglutamine tracts) of variable length were made using a previously described method (Michalik A et al., Biotechniques, 2001). Briefly, synthetic CAG/CAA oligonucleotides were subcloned into a cDNA construct of the normal mouse (13 CAG/CAA) TBP gene. Because of the mixed nature of the repeat, its length is stable in mitotic and meiotic transmission.
2007-11-09 | E-MEXP-1313 | biostudies-arrayexpress
Project description:The neurodegenerative disease spinocerebellar ataxia type 3 (SCA3; also called Machado-Joseph disease, MJD) is a trinucleotide repeat disorder caused by expansion of CAG repeats which encoding an abnormal long polyglutamine (polyQ) tract in ataxin-3 of the ATXN3 gene. Even now the pathogenic mechanism has remained elusive and no cure method is currently available. In this study, we first applied CRISPR/Cas9-mediated approach using homologous recombination to achieve one-step genetic correction in SCA3-specific induced pluripotent stem cells (iPSCs) by adjusting pathological 80 CAG repeats to normal 13 CAG repeats, without detectable off-target based on whole exon sequencing or polyacrylamide gel electrophoresis (PAGE). The correction normalized SCA3 pathogenic signal pathways (like transcription, apoptosis, and ubiquitin-dependent protein catabolic process) and reversed disease-associated phenotypes. Our strategy provides deep insights into pathogenic mechanism of SCA3 disease and suggests potential therapeutic applications of trinucleotide repeat disorders.
2020-01-17 | GSE93713 | GEO
Project description:Spinocerebellar ataxia type 3 (SCA3) is a dominantly inherited neurodegenerative disorder caused by a polyglutamine-encoding CAG repeat expansion in the ATXN3 gene, which encodes a deubiquitinating enzyme, ATXN3, implicated in numerous quality control pathways. Several mechanisms have been proposed to explain the pathogenic role of mutant polyQ-expanded ATXN3 in SCA3 including disease protein aggregation, impairment of ubiquitin-proteasomal degradation and transcriptional dysregulation. A better understanding of the normal functions of this protein may shed light on SCA3 disease pathogenesis. To assess the potential normal role of ATXN3 in regulating transcription, we compared gene expression profiles in wildtype (WT) versus Atxn3 knockout (KO) mouse embryonic fibroblasts (MEFs).
2018-07-13 | GSE117028 | GEO
Project description:Spinocerebellar ataxia type 3 (SCA3) is the most common autosomal dominant inherited ataxia worldwide, caused by a CAG repeat expansion in the Ataxin-3 gene resulting in a polyglutamine (polyQ)-expansion in the corresponding protein. Here we have RNA-sequencing data from the cerebellum of individuals with SCA3 and matched controls.
| EGAD00001009317 | EGA
Project description:Transcription profiles were obtained for 2-month old mice. Three lines (WT, TBP-13Q12, and TBP105Q) were used in these experiments. <br><br> Wild-type and 13Q mice are normal. The 13Q mice overexpress the normal protein on the RNA but not protein level and do not show a phenotype. The 105Q mice express a mutant version of the protein TBP and faithfully model the disease SCA17 (spinocerebellar ataxia-17, huntington disease-like 4, HDL4). <br><br> The constructs containing mixed CAG/CAA trinucleotide repeats (and encoding polyglutamine tracts) of variable length were made using a previously described method (Michalik A et al., Biotechniques, 2001). Briefly, synthetic CAG/CAA oligonucleotides were subcloned into a cDNA construct of the normal mouse (13 CAG/CAA) TBP gene. Because of the mixed nature of the repeat, its length is stable in mitotic and meiotic transmission.
2007-11-09 | E-MEXP-1314 | biostudies-arrayexpress
Project description:Spinocerebellar ataxia type 3 is the most common autosomal dominant inherited ataxia worldwide and caused by a CAG repeat expansion in the Ataxin-3 gene resulting in a polyQ expansion in the corresponding protein. The disease is characterized by neuropathological (aggregate formation, cell loss), phenotypical (gait instability, body weight reduction) and transcriptional changes. So far there is no mouse model available representing all the different aspects of the disease, but a representative model is highly needed to gain a better understanding of the disease pathomechanism. Here we characterized a novel Ataxin-3 knock-in mouse model, expressing an expansion of 304 CAG/CAAs either heterozygous or homozygous in the murine Ataxin-3 locus using biochemical, behavioral and transcriptomic approaches. Further, we correlated the transcriptional changes of the knock-in mice to those found in human SCA3 patients, to prove the comparability of our model. The novel Ataxin-3 knock-in mouse is characterized by the expression of polyQ-expanded Ataxin-3 in the murine protein, leading to massive aggregate formation, especially in brain regions known to be vulnerable in SCA3 patients, and impairment of Purkinje cells. Caused by these neuropathological changes, the mice demonstrated phenotypically reduction in body weight accompanied by gait and balance instability. Transcriptomic analysis of cerebellar tissue revealed downregulation of differentially expressed genes enriched in myelinating oligodendrocytes. Comparing these transcriptional changes with those found in cerebellar tissue of SCA3 patients, we discovered an overlap of differentially expressed genes pointing towards disturbances in the myelin sheaths and myelinating oligodendrocytes.
2022-04-01 | GSE145613 | GEO
Project description:Recent evidence supports a role for RNA as a common pathogenic agent in both the “polyglutamine” and “untranslated” dominant expanded repeat disorders. One feature of all repeat sequences currently associated with disease is their predicted ability to form a hairpin secondary structure at the RNA level. In order to investigate mechanisms by which hairpin forming repeat RNAs could induce neurodegeneration, we have looked for alterations in gene transcripts as hallmarks of the cellular response to toxic hairpin repeat RNAs. Three disease associated repeat sequences - CAG, CUG and AUUCU - were specifically expressed in the neurons of Drosophila and resultant common, early, transcriptional changes assessed by microarray analyses. Transcripts that encode several components of the Akt/Gsk3-β signalling pathway were altered as a consequence of expression of these repeat RNAs, indicating that this pathway is a component of the neuronal response to these pathogenic RNAs and may represent an important common therapeutic target in this class of diseases. The heads from newly eclosed Male Drosophila were used for RNA extraction and profiling on Affymetrix Drosophile Genome 2.0 microarrays. Twenty samples were analysed, representing control and experimental lines. Two independently derived control lines were used in each exeriment, totaling 4 samples. The tri-nucleotide repeats (CAG, CUG, CAA) were represented by three independently derived two transgene insertion lines each in one experiment and two independent four transgene insertion lines each in a second experiment, totaling 15 samples. A single four transgene insertion line was analysed for AUUCU. Candidates were selected from the pool of transcripts which showed a ‘present’ call in either all independent lines for a particular repeat sequence, or in all samples for the elav- GAL4/+ control in that experiment. Where possible, T-tests were performed on raw values to determine samples that showed a significant difference with a P-value < 0.05.
2011-04-28 | E-GEOD-27178 | biostudies-arrayexpress
Project description:Spinocerebellar ataxia type 2 (SCA2) is among the progressive neurodegenerative polyglutamine (polyQ) diseases. It is caused by a CAG repeat expansion in an encoded region of the ATXN2 gene giving rise to an expanded polyQ domain in the encoded ATXN2 protein. SCA2 is an autosomal dominant disorder characterized by symptoms resulting from neurodegeneration of cerebellar Purkinje cells. To molecularly characterize SCA2 disease progression, we analyzed RNA-sequencing data produced using the cerebella of ATXN2Q127 mice collected at three distinct time points. The ATXN2Q127 mouse model contains 127 CAG repeats in the full-length ATXN2 cDNA under the control of the PC targeted Pcp2 promoter.
2017-12-09 | E-MTAB-6293 | biostudies-arrayexpress
Project description:Expanded CAG/CTG repeats underlie thirteen neurological disorders, including myotonic dystrophy type 1 (DM1) and Huntington’s disease (HD). Upon expansion, CAG/CTG repeat loci acquire heterochromatic characteristics. This observation raises the hypothesis that repeat expansion provokes changes to higher-order chromatin conformation and thereby affects both gene expression in cis and the genetic instability of the repeat tract. Here we tested this hypothesis directly by performing 4C sequencing at the DMPK and HTT loci from DM1 and HD patient-derived cells. Surprisingly, chromatin contacts remain unchanged upon repeat expansion at both loci. This was true for expanded alleles with different DNA methylation levels and CTCF binding. Repeat tract sizes ranging from 15 to 1,700 repeats displayed strikingly similar chromatin interaction profiles. Moreover, the ectopic insertion of an expanded CAG repeat tract did not change the three-dimensional chromatin conformation of the surrounding genomic region. Our findings argue that extensive changes in heterochromatic properties are not enough to alter chromatin conformation at expanded CAG/CTG repeat loci. We conclude that 3D chromatin conformation is unlikely to drive repeat expansions or changes in gene expression in expanded CAG/CTG repeat disorders. This SuperSeries is composed of the SubSeries listed below.
2020-04-07 | GSE148185 | GEO