Friedreich’s Ataxia Induced Pluripotent Stem Cells Recapitulate GAA•TTC Triplet-Repeat Instability
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE22651 | GEO | 2010/07/02
SECONDARY ACCESSION(S): PRJNA128015
REPOSITORIES: GEO
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Project description:The inherited neurodegenerative disease Friedreichâ??s ataxia (FRDA) is caused by hyperexpansion of GAAâ?¢TTC trinucleotide repeats within the first intron of the FXN gene, encoding the mitochondrial protein frataxin. Long GAAâ?¢TTC repeats causes heterochromatin-mediated silencing and loss of frataxin in affected individuals. We report the derivation of induced pluripotent stem cells (iPSCs) from FRDA patient fibroblasts through retroviral transduction of transcription factors. FXN gene repression is maintained in the iPSCs, as are the mRNA and miRNA global expression signatures reflecting the human disease. GAAâ?¢TTC repeats uniquely in FXN in the iPSCs exhibit repeat instability similar to patient families, where they expand and/or contract with discrete changes in length between generations. The mismatch repair enzyme Msh2, implicated in repeat instability in other triplet repeat diseases, is highly expressed in the iPSCs, occupies FXN intron 1, and shRNA silencing of Msh2 impedes repeat expansion, providing a possible molecular explanation for repeat expansion in FRDA. 65 samples from various number of tissue, primary cell lines undifferenatiated human embryonic stem cell lines, induces pluripotent stem cell lines have been run on Illumina HT12 v3 chips.
2010-07-30 | E-GEOD-22651 | biostudies-arrayexpress
Project description:Expansion of triplex-forming GAA/TTC repeats in the first intron of FRDA gene is known to cause Friedreich’s ataxia. Besides FRDA, there are a number of other highly polymorphic GAA/TTC loci in the human genome where the size variations so far were considered to be a neutral event. Using yeast as a model system, we demonstrate that expanded GAA/TTC repeats represent a threat to eukaryotic genome integrity by triggering double-strand breaks and gross chromosomal rearrangements. The fragility potential strongly depends on the length of the track and orientation of the repeats relative to the replication origin which correlates with their propensity to adopt secondary structure and to block replication progression. We show that fragility is mediated by mismatch repair machinery and requires the MutS(beta) and endonuclease activity of MutL(alpha). We suggest that the mechanism of GAA/TTC-induced chromosome aberrations defined in yeast can also operate in human carriers with expanded tracks. Keywords: CGH-array
2008-05-14 | GSE11425 | GEO
Project description:Friedreich's ataxia (FRDA) is an autosomal-recessive neurodegenerative and cardiac disorder which occurs when transcription of the FXN gene is silenced due to an excessive expansion of GAA repeats into its first intron. Herein, we generate dorsal root ganglia organoids (DRGOs) by in vitro differentiation of human iPSCs. Bulk and single-cell RNA sequencing show that DRGOs present a close transcriptional signature with native DRGs and display the main peripheral sensory neuronal and glial cell subtypes. Furthermore, when co-cultured with human intrafusal muscle fibers, DRGO sensory neurons contact their peripheral targets and reconstitute the muscle spindle proprioceptive receptors. FRDA DRGOs recapitulate key molecular and cellular deficits of the disease that are extensively rescued only when the entire FXN intron 1 is removed and not with the excision of merely the expanded GAA tract. These results strongly suggest that removal of the repressed chromatin flanking the GAA tract might be necessary to obtain a complete rescue of FXN expression and fully revert the pathological hallmarks of FRDA DRG neurons.
2020-07-27 | GSE148212 | GEO
Project description:Expansion of triplex-forming GAA/TTC repeats in the first intron of FRDA gene is known to cause Friedreich’s ataxia. Besides FRDA, there are a number of other highly polymorphic GAA/TTC loci in the human genome where the size variations so far were considered to be a neutral event. Using yeast as a model system, we demonstrate that expanded GAA/TTC repeats represent a threat to eukaryotic genome integrity by triggering double-strand breaks and gross chromosomal rearrangements. The fragility potential strongly depends on the length of the track and orientation of the repeats relative to the replication origin which correlates with their propensity to adopt secondary structure and to block replication progression. We show that fragility is mediated by mismatch repair machinery and requires the MutS(beta) and endonuclease activity of MutL(alpha). We suggest that the mechanism of GAA/TTC-induced chromosome aberrations defined in yeast can also operate in human carriers with expanded tracks. Keywords: CGH-array Genomic DNA from each of 15 strains was competitively hybridized to DNA from the parent diploid strain (Cy3/green). Gains of genomic segments in the survivors were detected as continuous regions of positive Log2 Red:Green ratios, while losses were detected as negative Log2 Red:Green ratios.
2008-05-14 | E-GEOD-11425 | biostudies-arrayexpress
Project description:Friedreich's ataxia (FRDA) is an autosomal-recessive neurodegenerative and cardiac disorder which occurs when transcription of the frataxin (FXN) gene is silenced due to the expansion of GAA·TTC repeats in intron 1 of the same gene, leading loss of the essential mitochondrial protein frataxin with several impairment in iron metabolism and respiration, primarily affects the sensory DRG neurons. A major limitation in the study of FRDA is the lack of robust animal and cellular models. To fill this gap, this study presents a novel 3D protocol to generate dorsal root ganglia-like organoids (DRGOs) from human iPSCs in which to model Friedreich's ataxia. DRGOs show a robust expression pattern of peripheral markers, are electro-physiologically active and out-perform peripheral sensory neurons generated with a traditional 2D protocol. Furthermore, when co-cultured with human stretch receptor intrafusal muscle fibers, DRGOs contact their peripheral target and form an in vitro muscle spindle. DRGOs generated from FRDA patient-derived iPSCs recapitulate several aspects of FRDA pathology including reduced expression of FXN and TCA-cycle components and mitochondrial fragmentation. We present also the recovery of this pathological signs, achieved by a new CRISPR-Cas9 mediated deletion of the GAA·TTC tract along with the majority of the affected intron. FRDA patient edited DRGOs with the long deletion boast normalized markers of oxidative stress, as well as recovered mitochondrial defect, particularly in the axonal compartment.
2020-07-27 | GSE133755 | GEO
Project description:Friedreich’s ataxia (FRDA) is an autosomal recessive neurodegenerative disease usually caused by large homozygous expansions of GAA repeat sequences in intron 1 of the frataxin (FXN) gene. FRDA patients have low FXN mRNA and frataxin protein levels when compared with heterozygous carriers or healthy controls. Presently, there is no effective treatment for FRDA, and biomarkers to measure therapeutic trial outcomes and/or to gauge disease progression are lacking. Peripheral tissues, including blood cells, buccal cells, and skin fibroblasts, can readily be isolated from FRDA patients and used to define molecular hallmarks of disease pathogenesis. However, because these tissues are not directly involved in disease pathogenesis, their relevance as models of the molecular aspects of the disease is yet to be decided. Transcriptome profiling of FRDA skin fibroblasts revealed significantly upregulated expression of genes encoding plasma membrane solute carrier proteins. Conversely, the expression of genes encoding accessory factors and enzymes involved in cytoplasmic and mitochondrial protein synthesis was consistently decreased in the FRDA cells. Finally, comparison of genes differentially expressed in FRDA fibroblasts to 3 previously published gene expression signatures defined for FRDA blood cells showed substantial overlap between the independent datasets, including correspondingly deficient expression of antioxidant defense genes. Together, these results indicate that gene expression profiling of cells derived from peripheral tissues can, in fact, consistently reveal novel molecular pathways of the disease.
2017-09-27 | GSE104288 | GEO
Project description:The molecular mechanisms of reduced frataxin (FXN) expression in Friedreich's ataxia (FRDA) are linked to epigenetic modification of the FXN locus caused by the disease-associated GAA expansion. Here, we identify that SUV4-20 histone methyltransferases, specifically SUV4-20 H1, play an important role in the regulation of FXN expression and represent a novel therapeutic target. Using a human FXN-GAA-Luciferase repeat expansion genomic DNA reporter model of FRDA, we screened the Structural Genomics Consortium epigenetic probe collection. We found that pharmacological inhibition of the SUV4-20 methyltransferases by the tool compound A-196 increased the expression of FXN by ∼1.5-fold in the reporter cell line. In several FRDA cell lines and patient-derived primary peripheral blood mononuclear cells, A-196 increased FXN expression by up to 2-fold, an effect not seen in WT cells. SUV4-20 inhibition was accompanied by a reduction in H4K20me2 and H4K20me3 and an increase in H4K20me1, but only modest (1.4-7.8%) perturbation in genome-wide expression was observed. Finally, based on the structural activity relationship and crystal structure of A-196, novel small molecule A-196 analogs were synthesized and shown to give a 20-fold increase in potency for increasing FXN expression. Overall, our results suggest that histone methylation is important in the regulation of FXN expression and highlight SUV4-20 H1 as a potential novel therapeutic target for FRDA.
2020-10-08 | GSE145115 | GEO
Project description:Friedreich ataxia (FRDA) is a multisystemic, autosomal recessive disorder caused by a homozygous GAA expansion mutation in the first intron of frataxin (FXN) gene. FXN is a mitochondrial protein critical for iron-sulfur cluster biosynthesis and deficiency impairs mitochondrial electron transport chain functions and iron homeostasis within the organelle. Currently, there is no effective treatment for FRDA. We have previously demonstrated that a single infusion of wild-type hematopoietic stem and progenitor cells (HSPCs) resulted in the prevention of the neurologic and cardiac complications of FRDA in YG8R mice, and the rescue was mediated by FXN transfer from tissue engrafted HSPC-derived microglia/macrophages to diseased neurons/myocytes. For a future clinical translation of this approach, we developed an autologous stem cell transplantation approach using CRISPR/Cas9 for the excision of the GAA repeats in FRDA patients’ CD34+ HSPCs; this strategy leading to increased FXN expression and improved mitochondrial functions in the cells. The aim of the current study is to validate the efficiency and safety of our gene editing approach in a disease-relevant model. To this end, we generated a cohort of FRDA patient-derived iPSCs and isogenic lines that were gene edited with our CRISPR/Cas9 approach. FRDA neurons generated from these iPSCs displayed characteristic apoptotic and mitochondrial phenotype of the disease, such as non-homogenous microtubule staining in neurites, increased caspase-3 expression, mitochondrial superoxide levels, mitochondrial fragmentation, and partial degradation of the cristae compared to healthy controls. These defects were fully prevented in the gene edited neurons. RNASeq analysis of FRDA and gene edited neurons demonstrated striking improvement in gene clusters associated with endoplasmic reticulum (ER) stress in the isogenic lines. These results were validated by molecular and functional studies, and gene edited neurons demonstrated improved ER-calcium release, normalization of ER stress response gene, XBP-1, and significantly increased ER-mitochondrial contacts that are critical for functional homeostasis of both organelles, as compared to FRDA neurons. Ultrastructural analysis for these contact sites displayed severe structural damage to the ER in FRDA neurons, that was undetected in gene edited neurons. Taken together, these results represent a novel finding for disease pathogenesis showing dramatic ER structural damage and function in FRDA. In addition, these results validate the efficacy profile of our FXN gene editing approach, in a disease relevant model improving mitochondrial and cellular, and supporting our approach as an effective strategy for therapeutic intervention for Friedreich’s ataxia.
2024-01-29 | GSE244886 | GEO
Project description:Friedreich's Ataxia (FRDA), a rare, inherited, progressive degenerative disease, is caused by a defective expression of mitochondrial protein frataxin (FXN), due to homozygous hyper-expansion of GAA triplets in the gene which severely reduce its transcription. FXN is crucial for cell survival and its deficiency in humans critically affects viability of neurons, cardiomyocytes and pancreatic beta cells. Around two thirds of individuals with FRDA show typical manifestation of hypertrophic cardiomyopathy, that can progress in heart failure and death. Except for FXN, very few genes have been correlated with ataxia and cardiac disease in FRDA. To identify other genes involved in pathogenesis of FRDA, a microarray analysis on FRDA patient's lymphoblastoid cells stably reconstituted with FXN was performed. HS-1 associated protein X-1 (HAX-1), a family of proteins playing important roles in the protection of cardiomyocytes from apoptosis, is the highest up-regulated transcript (FC=+2, p<0.0006). HAX-1 is highly expressed in heart and HAX-1 heterozygous-deficient hearts exhibit increases in infarct size. The microarray result was further assessed with qRT-PCR and western blot analysis performed on HEK293 stably transfected with empty vector or FXN-vector and lymphoblasts from FRDA patients compared to clinically unaffected heterozygous parents, confirming a strong co-expression of HAX-1 and FXN both at mRNA and protein level. Moreover, analysis of FXN and HAX-1 in peripheral blood mononuclear cells (PBMCs) of FRDA patients (n=13), heterozygous parents (n=6) and non-correlated healthy controls (n=13) revealed that their expressions are correlated. The positive correlation is more significant in FRDA patients showing a cardiac disease (10/13). The positive correlation between frataxin and HAX-1 expression level suggests a potential link of HAX-1 expression to pro-survival or protective cellular pathways related to frataxin. Thus, HAX-1 may be considered a specific biomarker of cardiomyopathy in FRDA and may represent a prognostic implement in these patients. Moreover, the discovery of novel genetic "risk" or "protective" factors in cardiomyopathy is crucial to improve risk stratification strategies and to identify new therapeutic targets.
2019-12-31 | GSE108200 | GEO
Project description:Background: Friedreich ataxia, an autosomal recessive neurodegenerative and cardiac disease, is caused by abnormally low levels of frataxin, an essential mitochondrial protein. All Friedreich ataxia patients carry a GAA/TTC repeat expansion in the first intron of the frataxin gene, either in the homozygous state or in compound heterozygosity with other loss-of-function mutations. The GAA expansion inhibits frataxin expression through a heterochromatin-mediated repression mechanism. Histone modifications that are characteristic of silenced genes in heterochromatic regions occur at expanded alleles in cells from Friedreich ataxia patients, including increased trimethylation of histone H3 at lysine 9 and hypoacetylation of histones H3 and H4. Methodology/Principal Findings: By chromatin immunoprecipitation, we detected the same heterochromatin marks in homozygous mice carrying a (GAA)230 repeat in the first intron of the mouse frataxin gene (KIKI mice). These animals have decreased frataxin levels and, by microarray analysis, show significant gene expression changes in several tissues. We treated KIKI mice with a novel histone deacetylase inhibitor, compound 106, which substantially increases frataxin mRNA levels in cells from Friedreich ataxia individuals. Treatment increased histone H3 and H4 acetylation in chromatin near the GAA repeat and restored wild-type frataxin levels in the nervous system and heart, as determined by quantitative RT-PCR and semiquantitative western blot analysis. No toxicity was observed. Furthermore, most of the differentially expressed genes in KIKI mice reverted towards wild-type levels. Conclusions/Significance: Lack of acute toxicity, normalization of frataxin levels and of the transcription profile changes resulting from frataxin deficiency provide strong support to a possible efficacy of this or related compounds in reverting the pathological process in Friedreich ataxia, a so far incurable neurodegenerative disease. Keywords: drug response
2008-03-08 | GSE10745 | GEO