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Krasilnikova MM, Humphries CL, Shinsky EM. Friedreich's ataxia: new insights. Emerg Top Life Sci 2023; 7:313-323. [PMID: 37698160 DOI: 10.1042/etls20230017] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 08/09/2023] [Accepted: 08/29/2023] [Indexed: 09/13/2023]
Abstract
Friedreich ataxia (FRDA) is an inherited disease that is typically caused by GAA repeat expansion within the first intron of the FXN gene coding for frataxin. This results in the frataxin deficiency that affects mostly muscle, nervous, and cardiovascular systems with progressive worsening of the symptoms over the years. This review summarizes recent progress that was achieved in understanding of molecular mechanism of the disease over the last few years and latest treatment strategies focused on overcoming the frataxin deficiency.
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Affiliation(s)
- Maria M Krasilnikova
- Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, U.S.A
| | - Casey L Humphries
- Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, U.S.A
| | - Emily M Shinsky
- Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, U.S.A
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Kalef-Ezra E, Edzeamey FJ, Valle A, Khonsari H, Kleine P, Oggianu C, Al-Mahdawi S, Pook MA, Anjomani Virmouni S. A new FRDA mouse model [ Fxn null:YG8s(GAA) > 800] with more than 800 GAA repeats. Front Neurosci 2023; 17:930422. [PMID: 36777637 PMCID: PMC9909538 DOI: 10.3389/fnins.2023.930422] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 01/04/2023] [Indexed: 01/27/2023] Open
Abstract
Introduction Friedreich's ataxia (FRDA) is an inherited recessive neurodegenerative disorder caused by a homozygous guanine-adenine-adenine (GAA) repeat expansion within intron 1 of the FXN gene, which encodes the essential mitochondrial protein frataxin. There is still no effective therapy for FRDA, therefore the development of optimal cell and animal models of the disease is one of the priorities for preclinical therapeutic testing. Methods We obtained the latest FRDA humanized mouse model that was generated on the basis of our previous YG8sR, by Jackson laboratory [YG8JR, Fxn null:YG8s(GAA) > 800]. We characterized the behavioral, cellular, molecular and epigenetics properties of the YG8JR model, which has the largest GAA repeat sizes compared to all the current FRDA mouse models. Results We found statistically significant behavioral deficits, together with reduced levels of frataxin mRNA and protein, and aconitase activity in YG8JR mice compared with control Y47JR mice. YG8JR mice exhibit intergenerational GAA repeat instability by the analysis of parent and offspring tissue samples. Somatic GAA repeat instability was also detected in individual brain and cerebellum tissue samples. In addition, increased DNA methylation of CpG U13 was identified in FXN GAA repeat region in the brain, cerebellum, and heart tissues. Furthermore, we show decreased histone H3K9 acetylation and increased H3K9 methylation of YG8JR cerebellum tissues within the FXN gene, upstream and downstream of the GAA repeat region compared to Y47JR controls. Discussion These studies provide a detailed characterization of the GAA repeat expansion-based YG8JR transgenic mouse models that will help investigations of FRDA disease mechanisms and therapy.
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Affiliation(s)
- Ester Kalef-Ezra
- Ataxia Research Group, Division of Biosciences, Department of Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Fred Jonathan Edzeamey
- Ataxia Research Group, Division of Biosciences, Department of Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Adamo Valle
- Energy Metabolism and Nutrition, Research Institute of Health Sciences (IUNICS), University of Balearic Islands, Palma, Spain,Health Research Institute of Balearic Islands (IdISBa), Palma, Spain,Biomedical Research Networking Center for Physiopathology of Obesity and Nutrition (CIBERobn CB06/03/0043), Instituto de Salud Carlos III, Madrid, Spain
| | - Hassan Khonsari
- Ataxia Research Group, Division of Biosciences, Department of Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Paula Kleine
- Ataxia Research Group, Division of Biosciences, Department of Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Carlo Oggianu
- Ataxia Research Group, Division of Biosciences, Department of Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Sahar Al-Mahdawi
- Ataxia Research Group, Division of Biosciences, Department of Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Mark A. Pook
- Ataxia Research Group, Division of Biosciences, Department of Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Sara Anjomani Virmouni
- Ataxia Research Group, Division of Biosciences, Department of Life Sciences, Brunel University London, Uxbridge, United Kingdom,*Correspondence: Sara Anjomani Virmouni,
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Russell LG, Davis LAK, Hunter JE, Perkins ND, Kenneth NS. Increased migration and motility in XIAP-null cells mediated by the C-RAF protein kinase. Sci Rep 2022; 12:7943. [PMID: 35562367 PMCID: PMC9106734 DOI: 10.1038/s41598-022-11438-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 04/11/2022] [Indexed: 11/18/2022] Open
Abstract
The product encoded by the X-linked inhibitor of apoptosis (XIAP) gene is a multi-functional protein which not only controls caspase-dependent cell death, but also participates in inflammatory signalling, copper homeostasis, response to hypoxia and control of cell migration. Deregulation of XIAP, either by elevated expression or inherited genetic deletion, is associated with several human disease states. Reconciling XIAP-dependent signalling pathways with its role in disease progression is essential to understand how XIAP promotes the progression of human pathologies. In this study we have created a panel of genetically modified XIAP-null cell lines using TALENs and CRISPR/Cas9 to investigate the functional outcome of XIAP deletion. Surprisingly, in our genetically modified cells XIAP deletion had no effect on programmed cell death, but instead the primary phenotype we observed was a profound increase in cell migration rates. Furthermore, we found that XIAP-dependent suppression of cell migration was dependent on XIAPdependent control of C-RAF levels, a protein kinase which controls cell signalling pathways that regulate the cytoskeleton. These results suggest that XIAP is not necessary for control of the apoptotic signalling cascade, however it does have a critical role in controlling cell migration and motility that cannot be compensated for in XIAP-knockout cells.
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Affiliation(s)
- Lauren G Russell
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Lydia A K Davis
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Jill E Hunter
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Neil D Perkins
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Niall S Kenneth
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
- Department of Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK.
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Rodden LN, Gilliam KM, Lam C, Rojsajjakul T, Mesaros C, Dionisi C, Pook M, Pandolfo M, Lynch DR, Blair IA, Bidichandani SI. DNA methylation in Friedreich ataxia silences expression of frataxin isoform E. Sci Rep 2022; 12:5031. [PMID: 35322126 PMCID: PMC8943190 DOI: 10.1038/s41598-022-09002-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 03/14/2022] [Indexed: 11/15/2022] Open
Abstract
Epigenetic silencing in Friedreich ataxia (FRDA), induced by an expanded GAA triplet-repeat in intron 1 of the FXN gene, results in deficiency of the mitochondrial protein, frataxin. A lesser known extramitochondrial isoform of frataxin detected in erythrocytes, frataxin-E, is encoded via an alternate transcript (FXN-E) originating in intron 1 that lacks a mitochondrial targeting sequence. We show that FXN-E is deficient in FRDA, including in patient-derived cell lines, iPS-derived proprioceptive neurons, and tissues from a humanized mouse model. In a series of FRDA patients, deficiency of frataxin-E protein correlated with the length of the expanded GAA triplet-repeat, and with repeat-induced DNA hypermethylation that occurs in close proximity to the intronic origin of FXN-E. CRISPR-induced epimodification to mimic DNA hypermethylation seen in FRDA reproduced FXN-E transcriptional deficiency. Deficiency of frataxin E is a consequence of FRDA-specific epigenetic silencing, and therapeutic strategies may need to address this deficiency.
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Affiliation(s)
- Layne N Rodden
- Department of Pediatrics, University of Oklahoma Health Sciences Center, OU Children's Physician Building, Suite 12100, 1200 Children's Avenue, Oklahoma City, OK, 73104, USA
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Kaitlyn M Gilliam
- Department of Pediatrics, University of Oklahoma Health Sciences Center, OU Children's Physician Building, Suite 12100, 1200 Children's Avenue, Oklahoma City, OK, 73104, USA
| | - Christina Lam
- Department of Pediatrics, University of Oklahoma Health Sciences Center, OU Children's Physician Building, Suite 12100, 1200 Children's Avenue, Oklahoma City, OK, 73104, USA
| | - Teerapat Rojsajjakul
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Clementina Mesaros
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Mark Pook
- Division of Biosciences, Department of Life Sciences, College of Health and Life Sciences, Brunel University London, Uxbridge, UK
| | - Massimo Pandolfo
- Université Libre de Bruxelles (ULB), Brussels, Belgium
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
| | - David R Lynch
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Ian A Blair
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Sanjay I Bidichandani
- Department of Pediatrics, University of Oklahoma Health Sciences Center, OU Children's Physician Building, Suite 12100, 1200 Children's Avenue, Oklahoma City, OK, 73104, USA.
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
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Fei J, Xu J, Li Z, Xu K, Wang D, Kassavetis GA, Kadonaga JT. NDF is a transcription factor that stimulates elongation by RNA polymerase II. Genes Dev 2022; 36:294-299. [PMID: 35273076 PMCID: PMC8973848 DOI: 10.1101/gad.349150.121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 02/17/2022] [Indexed: 11/24/2022]
Abstract
Here, Fei et al. found that NDF, which was identified as a bilaterian nucleosome-destabilizing factor, is also a Pol II transcription factor that stimulates elongation with plain DNA templates in the absence of nucleosomes. Their findings demonstrate that NDF is a Pol II binding transcription elongation factor that is localized over gene bodies and is conserved from yeast to humans. RNA polymerase II (Pol II) elongation is a critical step in gene expression. Here we found that NDF, which was identified as a bilaterian nucleosome-destabilizing factor, is also a Pol II transcription factor that stimulates elongation with plain DNA templates in the absence of nucleosomes. NDF binds directly to Pol II and enhances elongation by a different mechanism than that used by transcription factor TFIIS. Moreover, yeast Pdp3, which is related to NDF, binds to Pol II and stimulates elongation. Thus, NDF is a Pol II binding transcription elongation factor that is localized over gene bodies and is conserved from yeast to humans.
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Affiliation(s)
- Jia Fei
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Jun Xu
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, La Jolla, California 92093, USA
| | - Ziwei Li
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Kevin Xu
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Dong Wang
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, La Jolla, California 92093, USA
| | - George A Kassavetis
- Section of Molecular Biology, University of California at San Diego, La Jolla, California 92093, USA
| | - James T Kadonaga
- Section of Molecular Biology, University of California at San Diego, La Jolla, California 92093, USA
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Schreiber AM, Li Y, Chen YH, Napierala JS, Napierala M. Selected Histone Deacetylase Inhibitors Reverse the Frataxin Transcriptional Defect in a Novel Friedreich's Ataxia Induced Pluripotent Stem Cell-Derived Neuronal Reporter System. Front Neurosci 2022; 16:836476. [PMID: 35281493 PMCID: PMC8904878 DOI: 10.3389/fnins.2022.836476] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 01/12/2022] [Indexed: 11/23/2022] Open
Abstract
Friedreich's ataxia (FRDA) is a neurodegenerative disorder caused by the expansion of guanine-adenine-adenine repeats within the first intron of the frataxin (FXN) gene. The location and nature of the expansion have been proven to contribute to transcriptional repression of FXN by decreasing the rate of polymerase II (RNA polymerase II) progression and increasing the presence of histone modifications associated with a heterochromatin-like state. Targeting impaired FXN transcription appears as a feasible option for therapeutic intervention, while no cure currently exists. We created a novel reporter cell line containing an FXN-Nanoluciferase (FXN-NLuc) fusion in induced pluripotent stem cells (iPSCs) reprogrammed from the fibroblasts of patients with FRDA, thus allowing quantification of endogenous FXN expression. The use of iPSCs provides the opportunity to differentiate these cells into disease-relevant neural progenitor cells (NPCs). NPCs derived from the FXN-NLuc line responded to treatments with a known FXN inducer, RG109. Results were validated by quantitative PCR and Western blot in multiple FRDA NPC lines. We then screened a commercially available library of compounds consisting of molecules targeting various enzymes and pathways critical for silencing or activation of gene expression. Only selected histone deacetylase inhibitors were capable of partial reactivation of FXN expression. This endogenous, FRDA iPSC-derived reporter can be utilized for high-throughput campaigns performed in cells most relevant to disease pathology in search of FXN transcription activators.
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Affiliation(s)
- Anna M. Schreiber
- Department of Biochemistry and Molecular Genetics, Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Yanjie Li
- Department of Biochemistry and Molecular Genetics, Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Yi-Hsien Chen
- Genome Engineering and iPSC Center, Washington University, St. Louis, MO, United States
| | - Jill S. Napierala
- Department of Biochemistry and Molecular Genetics, Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL, United States
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Loureiro JR, Castro AF, Figueiredo AS, Silveira I. Molecular Mechanisms in Pentanucleotide Repeat Diseases. Cells 2022; 11:cells11020205. [PMID: 35053321 PMCID: PMC8773600 DOI: 10.3390/cells11020205] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 02/01/2023] Open
Abstract
The number of neurodegenerative diseases resulting from repeat expansion has increased extraordinarily in recent years. In several of these pathologies, the repeat can be transcribed in RNA from both DNA strands producing, at least, one toxic RNA repeat that causes neurodegeneration by a complex mechanism. Recently, seven diseases have been found caused by a novel intronic pentanucleotide repeat in distinct genes encoding proteins highly expressed in the cerebellum. These disorders are clinically heterogeneous being characterized by impaired motor function, resulting from ataxia or epilepsy. The role that apparently normal proteins from these mutant genes play in these pathologies is not known. However, recent advances in previously known spinocerebellar ataxias originated by abnormal non-coding pentanucleotide repeats point to a gain of a toxic function by the pathogenic repeat-containing RNA that abnormally forms nuclear foci with RNA-binding proteins. In cells, RNA foci have been shown to be formed by phase separation. Moreover, the field of repeat expansions has lately achieved an extraordinary progress with the discovery that RNA repeats, polyglutamine, and polyalanine proteins are crucial for the formation of nuclear membraneless organelles by phase separation, which is perturbed when they are expanded. This review will cover the amazing advances on repeat diseases.
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Affiliation(s)
- Joana R. Loureiro
- Genetics of Cognitive Dysfunction Laboratory, i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; (J.R.L.); (A.F.C.); (A.S.F.)
- Institute for Molecular and Cell Biology, Universidade do Porto, 4200-135 Porto, Portugal
| | - Ana F. Castro
- Genetics of Cognitive Dysfunction Laboratory, i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; (J.R.L.); (A.F.C.); (A.S.F.)
- Institute for Molecular and Cell Biology, Universidade do Porto, 4200-135 Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, 4050-313 Porto, Portugal
| | - Ana S. Figueiredo
- Genetics of Cognitive Dysfunction Laboratory, i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; (J.R.L.); (A.F.C.); (A.S.F.)
- Institute for Molecular and Cell Biology, Universidade do Porto, 4200-135 Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, 4050-313 Porto, Portugal
| | - Isabel Silveira
- Genetics of Cognitive Dysfunction Laboratory, i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; (J.R.L.); (A.F.C.); (A.S.F.)
- Institute for Molecular and Cell Biology, Universidade do Porto, 4200-135 Porto, Portugal
- Correspondence: ; Tel.: +351-2240-8800
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Rodden LN, Gilliam KM, Lam C, Lynch DR, Bidichandani SI. Epigenetic Heterogeneity in Friedreich Ataxia Underlies Variable FXN Reactivation. Front Neurosci 2021; 15:752921. [PMID: 34899161 PMCID: PMC8655727 DOI: 10.3389/fnins.2021.752921] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 11/01/2021] [Indexed: 11/13/2022] Open
Abstract
Friedreich ataxia (FRDA) is typically caused by homozygosity for an expanded GAA triplet-repeat in intron 1 of the FXN gene. The expanded repeat induces repressive histone changes and DNA hypermethylation, which result in epigenetic silencing and FXN transcriptional deficiency. A class I histone deacetylase inhibitor (HDACi-109) reactivates the silenced FXN gene, although with considerable inter-individual variability, which remains etiologically unexplained. Because HDAC inhibitors work by reversing epigenetic silencing, we reasoned that epigenetic heterogeneity among patients may help to explain this inter-individual variability. As a surrogate measure for epigenetic heterogeneity, a highly quantitative measurement of DNA hypermethylation via bisulfite deep sequencing, with single molecule resolution, was used to assess the prevalence of unmethylated, partially methylated, and fully methylated somatic FXN molecules in PBMCs from a prospective cohort of 50 FRDA patients. Treatment of the same PBMCs from this cohort with HDACi-109 significantly increased FXN transcript to levels seen in asymptomatic heterozygous carriers, albeit with the expected inter-individual variability. Response to HDACi-109 correlated significantly with the prevalence of unmethylated and partially methylated FXN molecules, supporting the model that FXN reactivation involves a proportion of genes that are amenable to correction in non-dividing somatic cells, and that heavily methylated FXN molecules are relatively resistant to reactivation. FXN reactivation is a promising therapeutic strategy in FRDA, and inter-individual variability is explained, at least in part, by somatic epigenetic heterogeneity.
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Affiliation(s)
- Layne N Rodden
- Department of Pediatrics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Oklahoma Center for Neuroscience, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Kaitlyn M Gilliam
- Department of Pediatrics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Christina Lam
- Department of Pediatrics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - David R Lynch
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA, United States
| | - Sanjay I Bidichandani
- Department of Pediatrics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Oklahoma Center for Neuroscience, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Department of Biochemistry and Molecular Biology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
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Li Y, Li J, Wang J, Lynch D, Shen X, R. Corey D, Parekh D, Bhat B, Woo C, Cherry J, Napierala J, Napierala M. Targeting 3' and 5' untranslated regions with antisense oligonucleotides to stabilize frataxin mRNA and increase protein expression. Nucleic Acids Res 2021; 49:11560-11574. [PMID: 34718736 PMCID: PMC8599914 DOI: 10.1093/nar/gkab954] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 09/30/2021] [Accepted: 10/04/2021] [Indexed: 12/26/2022] Open
Abstract
Friedreich's ataxia (FRDA) is a severe multisystem disease caused by transcriptional repression induced by expanded GAA repeats located in intron 1 of the Frataxin (FXN) gene encoding frataxin. FRDA results from decreased levels of frataxin; thus, stabilization of the FXN mRNA already present in patient cells represents an attractive and unexplored therapeutic avenue. In this work, we pursued a novel approach based on oligonucleotide-mediated targeting of FXN mRNA ends to extend its half-life and availability as a template for translation. We demonstrated that oligonucleotides designed to bind to FXN 5' or 3' noncoding regions can increase FXN mRNA and protein levels. Simultaneous delivery of oligonucleotides targeting both ends increases efficacy of the treatment. The approach was confirmed in several FRDA fibroblast and induced pluripotent stem cell-derived neuronal progenitor lines. RNA sequencing and single-cell expression analyses confirmed oligonucleotide-mediated FXN mRNA upregulation. Mechanistically, a significant elongation of the FXN mRNA half-life without any changes in chromatin status at the FXN gene was observed upon treatment with end-targeting oligonucleotides, indicating that transcript stabilization is responsible for frataxin upregulation. These results identify a novel approach toward upregulation of steady-state mRNA levels via oligonucleotide-mediated end targeting that may be of significance to any condition resulting from transcription downregulation.
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Affiliation(s)
- Yanjie Li
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd, Birmingham, AL 35294, USA
| | - Jixue Li
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd, Birmingham, AL 35294, USA
| | - Jun Wang
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd, Birmingham, AL 35294, USA
| | - David R Lynch
- Division of Neurology and Pediatrics, Children’s Hospital of Philadelphia, Abramson Research Center, Room 502, Philadelphia, PA 19104, USA
| | - Xiulong Shen
- Department of Pharmacology and Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - David R. Corey
- Department of Pharmacology and Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Darshan Parekh
- Translate Bio, 29 Hartwell Avenue, Lexington, MA 02421, USA
| | | | - Caroline Woo
- Translate Bio, 29 Hartwell Avenue, Lexington, MA 02421, USA
| | | | - Jill S Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd, Birmingham, AL 35294, USA
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd, Birmingham, AL 35294, USA
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Zhu L, Fukunaga R. RNA-binding protein Maca is crucial for gigantic male fertility factor gene expression, spermatogenesis, and male fertility, in Drosophila. PLoS Genet 2021; 17:e1009655. [PMID: 34181646 PMCID: PMC8248703 DOI: 10.1371/journal.pgen.1009655] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 07/01/2021] [Accepted: 06/09/2021] [Indexed: 11/19/2022] Open
Abstract
During spermatogenesis, the process in which sperm for fertilization are produced from germline cells, gene expression is spatiotemporally highly regulated. In Drosophila, successful expression of extremely large male fertility factor genes on Y-chromosome spanning some megabases due to their gigantic intron sizes is crucial for spermatogenesis. Expression of such extremely large genes must be challenging, but the molecular mechanism that allows it remains unknown. Here we report that a novel RNA-binding protein Maca, which contains two RNA-recognition motifs, is crucial for this process. maca null mutant male flies exhibited a failure in the spermatid individualization process during spermatogenesis, lacked mature sperm, and were completely sterile, while maca mutant female flies were fully fertile. Proteomics and transcriptome analyses revealed that both protein and mRNA abundance of the gigantic male fertility factor genes kl-2, kl-3, and kl-5 (kl genes) are significantly decreased, where the decreases of kl-2 are particularly dramatic, in maca mutant testes. Splicing of the kl-3 transcripts was also dysregulated in maca mutant testes. All these physiological and molecular phenotypes were rescued by a maca transgene in the maca mutant background. Furthermore, we found that in the control genetic background, Maca is exclusively expressed in spermatocytes in testes and enriched at Y-loop A/C in the nucleus, where the kl-5 primary transcripts are localized. Our data suggest that Maca increases transcription processivity, promotes successful splicing of gigantic introns, and/or protects transcripts from premature degradation, of the kl genes. Our study identified a novel RNA-binding protein Maca that is crucial for successful expression of the gigantic male fertility factor genes, spermatogenesis, and male fertility.
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Affiliation(s)
- Li Zhu
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ryuya Fukunaga
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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11
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Handal T, Eiges R. Correction of Heritable Epigenetic Defects Using Editing Tools. Int J Mol Sci 2021; 22:ijms22083966. [PMID: 33921346 PMCID: PMC8070094 DOI: 10.3390/ijms22083966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/02/2021] [Accepted: 04/07/2021] [Indexed: 11/21/2022] Open
Abstract
Epimutations refer to mistakes in the setting or maintenance of epigenetic marks in the chromatin. They lead to mis-expression of genes and are often secondary to germline transmitted mutations. As such, they are the cause for a considerable number of genetically inherited conditions in humans. The correction of these types of epigenetic defects constitutes a good paradigm to probe the fundamental mechanisms underlying the development of these diseases, and the molecular basis for the establishment, maintenance and regulation of epigenetic modifications in general. Here, we review the data to date, which is limited to repetitive elements, that relates to the applications of key editing tools for addressing the epigenetic aspects of various epigenetically regulated diseases. For each approach we summarize the efforts conducted to date, highlight their contribution to a better understanding of the molecular basis of epigenetic mechanisms, describe the limitations of each approach and suggest perspectives for further exploration in this field.
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Affiliation(s)
- Tayma Handal
- Stem Cell Research Laboratory, Medical Genetics Institute Shaare Zedek Medical Center, Jerusalem 91031, Israel;
- School of Medicine, The Hebrew University, Campus Ein Kerem, Jerusalem 91120, Israel
| | - Rachel Eiges
- Stem Cell Research Laboratory, Medical Genetics Institute Shaare Zedek Medical Center, Jerusalem 91031, Israel;
- School of Medicine, The Hebrew University, Campus Ein Kerem, Jerusalem 91120, Israel
- Correspondence:
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12
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Vilema-Enríquez G, Quinlan R, Kilfeather P, Mazzone R, Saqlain S, Del Molino Del Barrio I, Donato A, Corda G, Li F, Vedadi M, Németh AH, Brennan PE, Wade-Martins R. Inhibition of the SUV4-20 H1 histone methyltransferase increases frataxin expression in Friedreich's ataxia patient cells. J Biol Chem 2020; 295:17973-17985. [PMID: 33028632 PMCID: PMC7939392 DOI: 10.1074/jbc.ra120.015533] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Indexed: 12/11/2022] Open
Abstract
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.
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Affiliation(s)
| | - Robert Quinlan
- Structural Genomics Consortium, University of Oxford, Oxford, United Kingdom; Alzheimer's Research UK Oxford Drug Discovery Institute, Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Peter Kilfeather
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Roberta Mazzone
- Structural Genomics Consortium, University of Oxford, Oxford, United Kingdom; Alzheimer's Research UK Oxford Drug Discovery Institute, Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Saba Saqlain
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | | | - Annalidia Donato
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Gabriele Corda
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Fengling Li
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Masoud Vedadi
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada; Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
| | - Andrea H Németh
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Oxford Centre for Genomic Medicine, Oxford University Hospitals National Health Service Trust, Oxford, United Kingdom
| | - Paul E Brennan
- Structural Genomics Consortium, University of Oxford, Oxford, United Kingdom; Alzheimer's Research UK Oxford Drug Discovery Institute, Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Richard Wade-Martins
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom.
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13
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Smith FM, Kosman DJ. Molecular Defects in Friedreich's Ataxia: Convergence of Oxidative Stress and Cytoskeletal Abnormalities. Front Mol Biosci 2020; 7:569293. [PMID: 33263002 PMCID: PMC7686857 DOI: 10.3389/fmolb.2020.569293] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 09/10/2020] [Indexed: 01/18/2023] Open
Abstract
Friedreich’s ataxia (FRDA) is a multi-faceted disease characterized by progressive sensory–motor loss, neurodegeneration, brain iron accumulation, and eventual death by hypertrophic cardiomyopathy. FRDA follows loss of frataxin (FXN), a mitochondrial chaperone protein required for incorporation of iron into iron–sulfur cluster and heme precursors. After the discovery of the molecular basis of FRDA in 1996, over two decades of research have been dedicated to understanding the temporal manifestations of disease both at the whole body and molecular level. Early research indicated strong cellular iron dysregulation in both human and yeast models followed by onset of oxidative stress. Since then, the pathophysiology due to dysregulation of intracellular iron chaperoning has become central in FRDA relative to antioxidant defense and run-down in energy metabolism. At the same time, limited consideration has been given to changes in cytoskeletal organization, which was one of the first molecular defects noted. These alterations include both post-translational oxidative glutathionylation of actin monomers and differential DNA processing of a cytoskeletal regulator PIP5K1β. Currently unknown in respect to FRDA but well understood in the context of FXN-deficient cell physiology is the resulting impact on the cytoskeleton; this disassembly of actin filaments has a particularly profound effect on cell–cell junctions characteristic of barrier cells. With respect to a neurodegenerative disorder such as FRDA, this cytoskeletal and tight junction breakdown in the brain microvascular endothelial cells of the blood–brain barrier is likely a component of disease etiology. This review serves to outline a brief history of this research and hones in on pathway dysregulation downstream of iron-related pathology in FRDA related to actin dynamics. The review presented here was not written with the intent of being exhaustive, but to instead urge the reader to consider the essentiality of the cytoskeleton and appreciate the limited knowledge on FRDA-related cytoskeletal dysfunction as a result of oxidative stress. The review examines previous hypotheses of neurodegeneration with brain iron accumulation (NBIA) in FRDA with a specific biochemical focus.
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Affiliation(s)
- Frances M Smith
- Department of Biochemistry, State University of New York at Buffalo, Buffalo, NY, United States
| | - Daniel J Kosman
- Department of Biochemistry, State University of New York at Buffalo, Buffalo, NY, United States
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14
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Li J, Li Y, Wang J, Gonzalez TJ, Asokan A, Napierala JS, Napierala M. Defining Transcription Regulatory Elements in the Human Frataxin Gene: Implications for Gene Therapy. Hum Gene Ther 2020; 31:839-851. [PMID: 32527155 PMCID: PMC7462031 DOI: 10.1089/hum.2020.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 05/26/2020] [Indexed: 12/20/2022] Open
Abstract
Friedreich's ataxia (FRDA) is the most common inherited form of ataxia in humans. It is caused by severe downregulation of frataxin (FXN) expression instigated by hyperexpansion of the GAA repeats located in intron 1 of the FXN gene. Despite numerous studies focused on identifying compounds capable of stimulating FXN expression, current knowledge regarding cis-regulatory elements involved in FXN gene expression is lacking. Using a combination of episomal and genome-integrated constructs, we defined a minimal endogenous promoter sequence required to efficiently drive FXN expression in human cells. We generated 19 constructs varying in length of the DNA sequences upstream and downstream of the ATG start codon. Using transient transfection, we evaluated the capability of these constructs to drive FXN expression. These analyses allowed us to identify a region of the gene indispensable for FXN expression. Subsequently, selected constructs containing the FXN expression control regions of varying lengths were site specifically integrated into the genome of HEK293T and human-induced pluripotent stem cells (iPSCs). FXN expression was detected in iPSCs and persisted after differentiation to neuronal and cardiac cells, indicating lineage independent function of defined regulatory DNA sequences. Finally, based on these results, we generated AAV encoding miniFXN genes and demonstrated in vivo FXN expression in mice. Results of these studies identified FXN sequences necessary to express FXN in human and mouse cells and provided rationale for potential use of endogenous FXN sequence in gene therapy strategies for FRDA.
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Affiliation(s)
- Jixue Li
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Yanjie Li
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Jun Wang
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Trevor J. Gonzalez
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Aravind Asokan
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Surgery, Duke University School of Medicine, Durham, North Carolina, USA
| | - Jill S. Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
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15
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Misiorek JO, Schreiber AM, Urbanek-Trzeciak MO, Jazurek-Ciesiołka M, Hauser LA, Lynch DR, Napierala JS, Napierala M. A Comprehensive Transcriptome Analysis Identifies FXN and BDNF as Novel Targets of miRNAs in Friedreich's Ataxia Patients. Mol Neurobiol 2020; 57:2639-2653. [PMID: 32291635 PMCID: PMC7253519 DOI: 10.1007/s12035-020-01899-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 03/09/2020] [Indexed: 12/13/2022]
Abstract
Friedreich's ataxia (FRDA) is a genetic neurodegenerative disease that is caused by guanine-adenine-adenine (GAA) nucleotide repeat expansions in the first intron of the frataxin (FXN) gene. Although present in the intron, this mutation leads to a substantial decrease in protein expression. Currently, no effective treatment is available for FRDA, and, in addition to FXN, other targets with therapeutic potential are continuously sought. As miRNAs can regulate the expression of a broad spectrum of genes, are used as biomarkers, and can serve as therapeutic tools, we decided to identify and characterize differentially expressed miRNAs and their targets in FRDA cells compared to unaffected control (CTRL) cells. In this study, we performed an integrated miRNAseq and RNAseq analysis using the same cohort of primary FRDA and CTRL cells. The results of the transcriptome studies were supported by bioinformatic analyses and validated by qRT-PCR. miRNA interactions with target genes were assessed by luciferase assays, qRT-PCR, and immunoblotting. In silico analysis identified the FXN transcript as a target of five miRNAs upregulated in FRDA cells. Further studies confirmed that miRNA-224-5p indeed targets FXN, resulting in decreases in mRNA and protein levels. We also validated the ability of miRNA-10a-5p to bind and regulate the levels of brain-derived neurotrophic factor (BDNF), an important modulator of neuronal growth. We observed a significant decrease in the levels of miRNA-10a-5p and increase in the levels of BDNF upon correction of FRDA cells via zinc-finger nuclease (ZFN)-mediated excision of expanded GAA repeats. Our comprehensive transcriptome analyses identified miRNA-224-5p and miRNA-10a-5p as negative regulators of the FXN and BDNF expression, respectively. These results emphasize not only the importance of miRNAs in the pathogenesis of FRDA but also their potential as therapeutic targets for this disease.
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Affiliation(s)
- Julia O. Misiorek
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Anna M. Schreiber
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL USA
| | | | | | - Lauren A. Hauser
- Department of Pediatrics and Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA USA
- Children’s Hospital of Philadelphia, Philadelphia, PA USA
| | - David R. Lynch
- Department of Pediatrics and Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA USA
- Children’s Hospital of Philadelphia, Philadelphia, PA USA
| | - Jill S. Napierala
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL USA
| | - Marek Napierala
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL USA
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16
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McMackin MZ, Durbin-Johnson B, Napierala M, Napierala JS, Ruiz L, Napoli E, Perlman S, Giulivi C, Cortopassi GA. Potential biomarker identification for Friedreich's ataxia using overlapping gene expression patterns in patient cells and mouse dorsal root ganglion. PLoS One 2019; 14:e0223209. [PMID: 31665133 PMCID: PMC6821053 DOI: 10.1371/journal.pone.0223209] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 09/15/2019] [Indexed: 12/22/2022] Open
Abstract
Friedreich's ataxia (FA) is a neurodegenerative disease with no approved therapy that is the result of frataxin deficiency. The identification of human FA blood biomarkers related to disease severity and neuro-pathomechanism could support clinical trials of drug efficacy. To try to identify human biomarkers of neuro-pathomechanistic relevance, we compared the overlapping gene expression changes of primary blood and skin cells of FA patients with changes in the Dorsal Root Ganglion (DRG) of the KIKO FA mouse model. As DRG is the primary site of neurodegeneration in FA, our goal was to identify which changes in blood and skin of FA patients provide a 'window' into the FA neuropathomechanism inside the nervous system. In addition, gene expression in frataxin-deficient neuroglial cells and FA mouse hearts were compared for a total of 5 data sets. The overlap of these changes strongly supports mitochondrial changes, apoptosis and alterations of selenium metabolism. Consistent biomarkers were observed, including three genes of mitochondrial stress (MTIF2, ENO2), apoptosis (DDIT3/CHOP), oxidative stress (PREX1), and selenometabolism (SEPW1). These results prompted our investigation of the GPX1 activity as a marker of selenium and oxidative stress, in which we observed a significant change in FA patients. We believe these lead biomarkers that could be assayed in FA patient blood as indicators of disease severity and progression, and also support the involvement of mitochondria, apoptosis and selenium in the neurodegenerative process.
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Affiliation(s)
- Marissa Z. McMackin
- Department of Molecular Biosciences, University of California, Davis, Davis, California, United States of America
| | - Blythe Durbin-Johnson
- Bioinformatics, University of California, Davis, Davis, California, United States of America
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Jill S. Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Luis Ruiz
- Department of Molecular Biosciences, University of California, Davis, Davis, California, United States of America
| | - Eleonora Napoli
- Department of Molecular Biosciences, University of California, Davis, Davis, California, United States of America
| | - Susan Perlman
- Department of Neurology, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Cecilia Giulivi
- Department of Molecular Biosciences, University of California, Davis, Davis, California, United States of America
| | - Gino A. Cortopassi
- Department of Molecular Biosciences, University of California, Davis, Davis, California, United States of America
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17
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Jasoliya M, Sacca F, Sahdeo S, Chedin F, Pane C, Brescia Morra V, Filla A, Pook M, Cortopassi G. Dimethyl fumarate dosing in humans increases frataxin expression: A potential therapy for Friedreich's Ataxia. PLoS One 2019; 14:e0217776. [PMID: 31158268 PMCID: PMC6546270 DOI: 10.1371/journal.pone.0217776] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 05/18/2019] [Indexed: 11/19/2022] Open
Abstract
Friedreich's Ataxia (FA) is an inherited neurodegenerative disorder resulting from decreased expression of the mitochondrial protein frataxin, for which there is no approved therapy. High throughput screening of clinically used drugs identified Dimethyl fumarate (DMF) as protective in FA patient cells. Here we demonstrate that DMF significantly increases frataxin gene (FXN) expression in FA cell model, FA mouse model and in DMF treated humans. DMF also rescues mitochondrial biogenesis deficiency in FA-patient derived cell model. We further examined the mechanism of DMF's frataxin induction in FA patient cells. It has been shown that transcription-inhibitory R-loops form at GAA expansion mutations, thus decreasing FXN expression. In FA patient cells, we demonstrate that DMF significantly increases transcription initiation. As a potential consequence, we observe significant reduction in both R-loop formation and transcriptional pausing thereby significantly increasing FXN expression. Lastly, DMF dosed Multiple Sclerosis (MS) patients showed significant increase in FXN expression by ~85%. Since inherited deficiency in FXN is the primary cause of FA, and DMF is demonstrated to increase FXN expression in humans, DMF could be considered for Friedreich's therapy.
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Affiliation(s)
- Mittal Jasoliya
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, United States of America
| | - Francesco Sacca
- Department of Neurosciences, Odontostomatological and Reproductive Sciences, University Federico II, Naples, Italy
| | - Sunil Sahdeo
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, United States of America
| | - Frederic Chedin
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
| | - Chiara Pane
- Department of Neurosciences, Odontostomatological and Reproductive Sciences, University Federico II, Naples, Italy
| | - Vincenzo Brescia Morra
- Department of Neurosciences, Odontostomatological and Reproductive Sciences, University Federico II, Naples, Italy
| | - Alessandro Filla
- Department of Neurosciences, Odontostomatological and Reproductive Sciences, University Federico II, Naples, Italy
| | - Mark Pook
- Department of Life Sciences, College of Health & Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Gino Cortopassi
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, United States of America
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18
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Satellite DNA-containing gigantic introns in a unique gene expression program during Drosophila spermatogenesis. PLoS Genet 2019; 15:e1008028. [PMID: 31071079 PMCID: PMC6508621 DOI: 10.1371/journal.pgen.1008028] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 02/18/2019] [Indexed: 11/19/2022] Open
Abstract
Intron gigantism, where genes contain megabase-sized introns, is observed across species, yet little is known about its purpose or regulation. Here we identify a unique gene expression program utilized for the proper expression of genes with intron gigantism. We find that two Drosophila genes with intron gigantism, kl-3 and kl-5, are transcribed in a spatiotemporal manner over the course of spermatocyte differentiation, which spans ~90 hours. The introns of these genes contain megabases of simple satellite DNA repeats that comprise over 99% of the gene loci, and these satellite-DNA containing introns are transcribed. We identify two RNA-binding proteins that specifically localize to kl-3 and kl-5 transcripts and are needed for the successful transcription or processing of these genes. We propose that genes with intron gigantism require a unique gene expression program, which may serve as a platform to regulate gene expression during cellular differentiation. Introns are non-coding elements of eukaryotic genes, often containing important regulatory sequences. Curiously, some genes contain introns so large that more than 99% of the gene locus is non-coding. One of the best-studied large genes, Dystrophin, a causative gene for Duchenne Muscular Dystrophy, spans 2.2Mb, only 11kb of which is coding. This phenomenon, ‘intron gigantism’, is observed across species, yet little is known about its purpose or regulation. Here we identify a unique gene expression program utilized for the proper expression of genes with intron gigantism using Drosophila spermatogenic genes as a model system. We show that the gigantic introns of these genes are transcribed in line with the exons, likely as a single transcript. We identify two RNA-binding proteins that specifically localize to the site of transcription and are needed for the successful transcription or processing of these genes. We propose that genes with intron gigantism require a unique gene expression program, which may serve as a platform to regulate gene expression during cellular differentiation.
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Schreiber AM, Misiorek JO, Napierala JS, Napierala M. Progress in understanding Friedreich's ataxia using human induced pluripotent stem cells. Expert Opin Orphan Drugs 2019; 7:81-90. [PMID: 30828501 DOI: 10.1080/21678707.2019.1562334] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Introduction Friedreich's ataxia (FRDA) is an autosomal recessive multisystem disease mainly affecting the peripheral and central nervous systems, and heart. FRDA is caused by a GAA repeat expansion in the first intron of the frataxin (FXN) gene, that leads to reduced expression of FXN mRNA and frataxin protein. Neuronal and cardiac cells are primary targets of frataxin deficiency and generating models via differentiation of induced pluripotent stem cells (iPSCs) into these cell types is essential for progress towards developing therapies for FRDA. Areas covered This review is focused on modeling FRDA using human iPSCs and various iPSC-differentiated cell types. We emphasized the importance of patient and corrected isogenic cell line pairs to minimize effects caused by biological variability between individuals. Expert opinion The versatility of iPSC-derived cellular models of FRDA is advantageous for developing new therapeutic strategies, and rigorous testing in such models will be critical for approval of the first treatment for FRDA. Creating a well-characterized and diverse set of iPSC lines, including appropriate isogenic controls, will facilitate achieving this goal. Also, improvement of differentiation protocols, especially towards proprioceptive sensory neurons and organoid generation, is necessary to utilize the full potential of iPSC technology in the drug discovery process.
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Affiliation(s)
- Anna M Schreiber
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Julia O Misiorek
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Jill S Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham AL, United States
| | - Marek Napierala
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.,Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham AL, United States
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20
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Role of frataxin protein deficiency and metabolic dysfunction in Friedreich ataxia, an autosomal recessive mitochondrial disease. Neuronal Signal 2018; 2:NS20180060. [PMID: 32714592 PMCID: PMC7373238 DOI: 10.1042/ns20180060] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 10/08/2018] [Accepted: 10/10/2018] [Indexed: 01/04/2023] Open
Abstract
Friedreich ataxia (FRDA) is a progressive neurodegenerative disease with developmental features caused by a genetic deficiency of frataxin, a small, nuclear-encoded mitochondrial protein. Frataxin deficiency leads to impairment of iron–sulphur cluster synthesis, and consequently, ATP production abnormalities. Based on the involvement of such processes in FRDA, initial pathophysiological hypotheses focused on reactive oxygen species (ROS) production as a key component of the mechanism. With further study, a variety of other events appear to be involved, including abnormalities of mitochondrially related metabolism and dysfunction in mitochondrial biogenesis. Consequently, present therapies focus not only on free radical damage, but also on control of metabolic abnormalities and correction of mitochondrial biogenesis. Understanding the multitude of abnormalities in FRDA thus offers possibilities for treatment of this disorder.
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21
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Cobos SN, Bennett SA, Torrente MP. The impact of histone post-translational modifications in neurodegenerative diseases. Biochim Biophys Acta Mol Basis Dis 2018; 1865:1982-1991. [PMID: 30352259 DOI: 10.1016/j.bbadis.2018.10.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 10/05/2018] [Accepted: 10/11/2018] [Indexed: 02/08/2023]
Abstract
Every year, neurodegenerative disorders take more than 5000 lives in the US alone. Cures have not yet been found for many of the multitude of neuropathies. The majority of amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) and Parkinson's disease (PD) cases have no known genetic basis. Thus, it is evident that contemporary genetic approaches have failed to explain the etiology or etiologies of ALS/FTD and PD. Recent investigations have explored the potential role of epigenetic mechanisms in disease development. Epigenetics comprises heritable changes in gene utilization that are not derived from changes in the genome. A main epigenetic mechanism involves the post-translational modification of histones. Increased knowledge of the epigenomic landscape of neurodegenerative diseases would not only further our understanding of the disease pathologies, but also lead to the development of treatments able to halt their progress. Here, we review recent advances on the association of histone post-translational modifications with ALS, FTD, PD and several ataxias.
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Affiliation(s)
- Samantha N Cobos
- Chemistry Department of Brooklyn College, Brooklyn, New York 11210, United States; Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States
| | - Seth A Bennett
- Chemistry Department of Brooklyn College, Brooklyn, New York 11210, United States; Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States
| | - Mariana P Torrente
- Chemistry Department of Brooklyn College, Brooklyn, New York 11210, United States; Ph.D. Programs in Chemistry, Biochemistry, and Biology, The Graduate Center of the City University of New York, New York 10016, United States.
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22
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Parsa JY, Boudoukha S, Burke J, Homer C, Madhani HD. Polymerase pausing induced by sequence-specific RNA-binding protein drives heterochromatin assembly. Genes Dev 2018; 32:953-964. [PMID: 29967291 PMCID: PMC6075038 DOI: 10.1101/gad.310136.117] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 05/18/2018] [Indexed: 01/09/2023]
Abstract
In this study, Parsa et al. investigated the mechanisms underlying RNAi-independent heterochromatin assembly by the CTD–RRM protein Seb1 in S. pombe. They show that Seb1 promotes long-lived RNAPII pauses at pericentromeric repeat regions and that their presence correlates with the heterochromatin-triggering activities of the corresponding dg and dh DNA fragments, providing new insight into Seb1-mediated polymerase stalling as a signal necessary for heterochromatin nucleation. In Schizosaccharomyces pombe, transcripts derived from the pericentromeric dg and dh repeats promote heterochromatin formation via RNAi as well as an RNAi-independent mechanism involving the RNA polymerase II (RNAPII)-associated RNA-binding protein Seb1 and RNA processing activities. We show that Seb1 promotes long-lived RNAPII pauses at pericentromeric repeat regions and that their presence correlates with the heterochromatin-triggering activities of the corresponding dg and dh DNA fragments. Globally increasing RNAPII stalling by other means induces the formation of novel large ectopic heterochromatin domains. Such ectopic heterochromatin occurs even in cells lacking RNAi. These results uncover Seb1-mediated polymerase stalling as a signal necessary for heterochromatin nucleation.
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Affiliation(s)
- Jahan-Yar Parsa
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA
| | - Selim Boudoukha
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA
| | - Jordan Burke
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA
| | - Christina Homer
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA
| | - Hiten D Madhani
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA.,Chan-Zuckerberg Biohub, San Francisco, California 94158, USA
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23
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Napierala JS, Li Y, Lu Y, Lin K, Hauser LA, Lynch DR, Napierala M. Comprehensive analysis of gene expression patterns in Friedreich's ataxia fibroblasts by RNA sequencing reveals altered levels of protein synthesis factors and solute carriers. Dis Model Mech 2018; 10:1353-1369. [PMID: 29125828 PMCID: PMC5719256 DOI: 10.1242/dmm.030536] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 08/21/2017] [Indexed: 12/30/2022] Open
Abstract
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 homozygous for GAA expansions have low FXN mRNA and protein levels when compared with heterozygous carriers or healthy controls. Frataxin is a mitochondrial protein involved in iron–sulfur cluster synthesis, and many FRDA phenotypes result from deficiencies in cellular metabolism due to lowered expression of FXN. 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. For instance, FXN mRNA and protein levels as well as FXN GAA-repeat tract lengths are routinely determined using all of these cell types. 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. Herein, we conducted unbiased RNA sequencing to profile the transcriptomes of fibroblast cell lines derived from 18 FRDA patients and 17 unaffected control individuals. Bioinformatic analyses revealed significantly upregulated expression of genes encoding plasma membrane solute carrier proteins in FRDA fibroblasts. Conversely, the expression of genes encoding accessory factors and enzymes involved in cytoplasmic and mitochondrial protein synthesis was consistently decreased in FRDA fibroblasts. Finally, comparison of genes differentially expressed in FRDA fibroblasts to three 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. When performed on statistically meaningful sample group sizes, unbiased global profiling analyses utilizing peripheral tissues are critical for the discovery and validation of FRDA disease biomarkers. Summary: Transcriptome profiling of Friedreich's ataxia fibroblasts by RNA sequencing reveals that this peripheral tissue can be used as a disease model for gene expression biomarker discovery.
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Affiliation(s)
- Jill Sergesketter Napierala
- University of Alabama at Birmingham, Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, 1825 University Blvd., Birmingham, Alabama 35294, USA
| | - Yanjie Li
- University of Alabama at Birmingham, Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, 1825 University Blvd., Birmingham, Alabama 35294, USA
| | - Yue Lu
- University of Texas MD Anderson Cancer Center, Department of Molecular Carcinogenesis, Center for Cancer Epigenetics, Science Park, Smithville, Texas 78957, USA
| | - Kevin Lin
- University of Texas MD Anderson Cancer Center, Department of Molecular Carcinogenesis, Center for Cancer Epigenetics, Science Park, Smithville, Texas 78957, USA
| | - Lauren A Hauser
- Departments of Neurology and Pediatrics, Children's Hospital of Philadelphia, Abramson Research Center Room 502, Philadelphia, PA 19104, USA
| | - David R Lynch
- Departments of Neurology and Pediatrics, Children's Hospital of Philadelphia, Abramson Research Center Room 502, Philadelphia, PA 19104, USA
| | - Marek Napierala
- University of Alabama at Birmingham, Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, 1825 University Blvd., Birmingham, Alabama 35294, USA .,Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, 61-704, Poland
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24
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Abstract
More than 40 diseases, most of which primarily affect the nervous system, are caused by expansions of simple sequence repeats dispersed throughout the human genome. Expanded trinucleotide repeat diseases were discovered first and remain the most frequent. More recently tetra-, penta-, hexa-, and even dodeca-nucleotide repeat expansions have been identified as the cause of human disease, including some of the most common genetic disorders seen by neurologists. Repeat expansion diseases include both causes of myotonic dystrophy (DM1 and DM2), the most common genetic cause of amyotrophic lateral sclerosis/frontotemporal dementia (C9ORF72), Huntington disease, and eight other polyglutamine disorders, including the most common forms of dominantly inherited ataxia, the most common recessive ataxia (Friedreich ataxia), and the most common heritable mental retardation (fragile X syndrome). Here I review distinctive features of this group of diseases that stem from the unusual, dynamic nature of the underlying mutations. These features include marked clinical heterogeneity and the phenomenon of clinical anticipation. I then discuss the diverse molecular mechanisms driving disease pathogenesis, which vary depending on the repeat sequence, size, and location within the disease gene, and whether the repeat is translated into protein. I conclude with a brief clinical and genetic description of individual repeat expansion diseases that are most relevant to neurologists.
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25
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Erwin GS, Grieshop MP, Ali A, Qi J, Lawlor M, Kumar D, Ahmad I, McNally A, Teider N, Worringer K, Sivasankaran R, Syed DN, Eguchi A, Ashraf M, Jeffery J, Xu M, Park PMC, Mukhtar H, Srivastava AK, Faruq M, Bradner JE, Ansari AZ. Synthetic transcription elongation factors license transcription across repressive chromatin. Science 2017; 358:1617-1622. [PMID: 29192133 PMCID: PMC6037176 DOI: 10.1126/science.aan6414] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 11/15/2017] [Indexed: 12/22/2022]
Abstract
The release of paused RNA polymerase II into productive elongation is highly regulated, especially at genes that affect human development and disease. To exert control over this rate-limiting step, we designed sequence-specific synthetic transcription elongation factors (Syn-TEFs). These molecules are composed of programmable DNA-binding ligands flexibly tethered to a small molecule that engages the transcription elongation machinery. By limiting activity to targeted loci, Syn-TEFs convert constituent modules from broad-spectrum inhibitors of transcription into gene-specific stimulators. Here we present Syn-TEF1, a molecule that actively enables transcription across repressive GAA repeats that silence frataxin expression in Friedreich's ataxia, a terminal neurodegenerative disease with no effective therapy. The modular design of Syn-TEF1 defines a general framework for developing a class of molecules that license transcription elongation at targeted genomic loci.
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Affiliation(s)
- Graham S Erwin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Matthew P Grieshop
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Asfa Ali
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jun Qi
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Matthew Lawlor
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Deepak Kumar
- Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
- Genomics and Molecular Medicine, Council of Scientific and Industrial Research (CSIR)-Institute of Genomics and Integrative Biology (IGIB), New Delhi, India
| | - Istaq Ahmad
- Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
- Genomics and Molecular Medicine, Council of Scientific and Industrial Research (CSIR)-Institute of Genomics and Integrative Biology (IGIB), New Delhi, India
| | - Anna McNally
- Novartis Institutes for BioMedical Research (NIBR), Cambridge, MA 02139, USA
| | - Natalia Teider
- Novartis Institutes for BioMedical Research (NIBR), Cambridge, MA 02139, USA
| | - Katie Worringer
- Novartis Institutes for BioMedical Research (NIBR), Cambridge, MA 02139, USA
| | - Rajeev Sivasankaran
- Novartis Institutes for BioMedical Research (NIBR), Cambridge, MA 02139, USA
| | - Deeba N Syed
- Department of Dermatology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Asuka Eguchi
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Md Ashraf
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Justin Jeffery
- Small Animal Imaging Facility, University of Wisconsin Carbone Cancer Center, Madison, WI 53792, USA
| | - Mousheng Xu
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Paul M C Park
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Hasan Mukhtar
- Department of Dermatology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Achal K Srivastava
- Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
| | - Mohammed Faruq
- Genomics and Molecular Medicine, Council of Scientific and Industrial Research (CSIR)-Institute of Genomics and Integrative Biology (IGIB), New Delhi, India
| | - James E Bradner
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
- Novartis Institutes for BioMedical Research (NIBR), Cambridge, MA 02139, USA
| | - Aseem Z Ansari
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
- The Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI 53706, USA
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26
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Chandran V, Gao K, Swarup V, Versano R, Dong H, Jordan MC, Geschwind DH. Inducible and reversible phenotypes in a novel mouse model of Friedreich's Ataxia. eLife 2017; 6:e30054. [PMID: 29257745 PMCID: PMC5736353 DOI: 10.7554/elife.30054] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 11/20/2017] [Indexed: 12/13/2022] Open
Abstract
Friedreich's ataxia (FRDA), the most common inherited ataxia, is caused by recessive mutations that reduce the levels of frataxin (FXN), a mitochondrial iron binding protein. We developed an inducible mouse model of Fxn deficiency that enabled us to control the onset and progression of disease phenotypes by the modulation of Fxn levels. Systemic knockdown of Fxn in adult mice led to multiple phenotypes paralleling those observed in human patients across multiple organ systems. By reversing knockdown after clinical features appear, we were able to determine to what extent observed phenotypes represent reversible cellular dysfunction. Remarkably, upon restoration of near wild-type FXN levels, we observed significant recovery of function, associated pathology and transcriptomic dysregulation even after substantial motor dysfunction and pathology were observed. This model will be of broad utility in therapeutic development and in refining our understanding of the relative contribution of reversible cellular dysfunction at different stages in disease.
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Affiliation(s)
- Vijayendran Chandran
- Program in Neurogenetics, Department of Neurology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Kun Gao
- Program in Neurogenetics, Department of Neurology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Vivek Swarup
- Program in Neurogenetics, Department of Neurology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Revital Versano
- Program in Neurogenetics, Department of Neurology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Hongmei Dong
- Program in Neurogenetics, Department of Neurology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Maria C Jordan
- Department of Physiology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Daniel H Geschwind
- Program in Neurogenetics, Department of Neurology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
- Department of Human Genetics, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
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27
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Long A, Napierala JS, Polak U, Hauser L, Koeppen AH, Lynch DR, Napierala M. Somatic instability of the expanded GAA repeats in Friedreich's ataxia. PLoS One 2017; 12:e0189990. [PMID: 29261783 PMCID: PMC5736210 DOI: 10.1371/journal.pone.0189990] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 12/06/2017] [Indexed: 12/22/2022] Open
Abstract
Friedreich's ataxia (FRDA) is a genetic neurodegenerative disorder caused by transcriptional silencing of the frataxin gene (FXN) due to expansions of GAA repeats in intron 1. FRDA manifests with multiple symptoms, which may include ataxia, cardiomyopathy and diabetes mellitus. Expanded GAA tracts are genetically unstable, exhibiting both expansions and contractions. GAA length correlates with severity of FRDA symptoms and inversely with age of onset. Thus, tissue-specific somatic instability of long GAA repeats may be implicated in the development of symptoms and disease progression. Herein, we determined the extent of somatic instability of the GAA repeats in heart, cerebral cortex, spinal cord, cerebellar cortex, and pancreatic tissues from 15 FRDA patients. Results demonstrate differences in the lengths of the expanded GAAs among different tissues, with significantly longer GAA tracts detected in heart and pancreas than in other tissues. The expansion bias detected in heart and pancreas may contribute to disease onset and progression, making the mechanism of somatic instability an important target for therapy. Additionally, we detected significant differences in GAA tract lengths between lymphocytes and fibroblast pairs derived from 16 FRDA patients, with longer GAA tracts present in the lymphocytes. This result urges caution in direct comparisons of data obtained in these frequently used FRDA models. Furthermore, we conducted a longitudinal analysis of the GAA repeat length in lymphocytes collected over a span of 7-9 years and demonstrated progressive expansions of the GAAs with maximum gain of approximately 9 repeats per year. Continuous GAA expansions throughout the patient's lifespan, as observed in FRDA lymphocytes, should be considered in clinical trial designs and data interpretation.
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Affiliation(s)
- Ashlee Long
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Jill S. Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Urszula Polak
- Department of Molecular Carcinogenesis, Center for Cancer Epigenetics, University of Texas MD Anderson Cancer Center, Smithville, Texas, United States of America
| | - Lauren Hauser
- Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | | | - David R. Lynch
- Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
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28
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Polyzos AA, McMurray CT. Close encounters: Moving along bumps, breaks, and bubbles on expanded trinucleotide tracts. DNA Repair (Amst) 2017; 56:144-155. [PMID: 28690053 PMCID: PMC5558859 DOI: 10.1016/j.dnarep.2017.06.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Expansion of simple triplet repeats (TNR) underlies more than 30 severe degenerative diseases. There is a good understanding of the major pathways generating an expansion, and the associated polymerases that operate during gap filling synthesis at these "difficult to copy" sequences. However, the mechanism by which a TNR is repaired depends on the type of lesion, the structural features imposed by the lesion, the assembled replication/repair complex, and the polymerase that encounters it. The relationships among these parameters are exceptionally complex and how they direct pathway choice is poorly understood. In this review, we consider the properties of polymerases, and how encounters with GC-rich or abnormal structures might influence polymerase choice and the success of replication and repair. Insights over the last three years have highlighted new mechanisms that provide interesting choices to consider in protecting genome stability.
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Affiliation(s)
- Aris A Polyzos
- MBIB Division, Lawrence Berkeley Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Cynthia T McMurray
- MBIB Division, Lawrence Berkeley Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States.
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29
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Benini M, Fortuni S, Condò I, Alfedi G, Malisan F, Toschi N, Serio D, Massaro DS, Arcuri G, Testi R, Rufini A. E3 Ligase RNF126 Directly Ubiquitinates Frataxin, Promoting Its Degradation: Identification of a Potential Therapeutic Target for Friedreich Ataxia. Cell Rep 2017; 18:2007-2017. [PMID: 28228265 PMCID: PMC5329121 DOI: 10.1016/j.celrep.2017.01.079] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 12/14/2016] [Accepted: 01/29/2017] [Indexed: 12/21/2022] Open
Abstract
Friedreich ataxia (FRDA) is a severe genetic neurodegenerative disease caused by reduced expression of the mitochondrial protein frataxin. To date, there is no therapy to treat this condition. The amount of residual frataxin critically affects the severity of the disease; thus, attempts to restore physiological frataxin levels are considered therapeutically relevant. Frataxin levels are controlled by the ubiquitin-proteasome system; therefore, inhibition of the frataxin E3 ligase may represent a strategy to achieve an increase in frataxin levels. Here, we report the identification of the RING E3 ligase RNF126 as the enzyme that specifically mediates frataxin ubiquitination and targets it for degradation. RNF126 interacts with frataxin and promotes its ubiquitination in a catalytic activity-dependent manner, both in vivo and in vitro. Most importantly, RNF126 depletion results in frataxin accumulation in cells derived from FRDA patients, highlighting the relevance of RNF126 as a new therapeutic target for Friedreich ataxia.
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Affiliation(s)
- Monica Benini
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy; Fratagene Therapeutics Srl, Viale dei Campioni 8, 00144 Rome, Italy
| | - Silvia Fortuni
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy
| | - Ivano Condò
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy
| | - Giulia Alfedi
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy
| | - Florence Malisan
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy
| | - Nicola Toschi
- Medical Physics Section, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy; Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging and Harvard Medical School, Boston, MA 02115, USA
| | - Dario Serio
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy; Fratagene Therapeutics Srl, Viale dei Campioni 8, 00144 Rome, Italy
| | - Damiano Sergio Massaro
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy
| | - Gaetano Arcuri
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy
| | - Roberto Testi
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy; Fratagene Therapeutics Srl, Viale dei Campioni 8, 00144 Rome, Italy
| | - Alessandra Rufini
- Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, 00133 Rome, Italy; Fratagene Therapeutics Srl, Viale dei Campioni 8, 00144 Rome, Italy.
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30
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Madireddy A, Gerhardt J. Replication Through Repetitive DNA Elements and Their Role in Human Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:549-581. [PMID: 29357073 DOI: 10.1007/978-981-10-6955-0_23] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Human cells contain various repetitive DNA sequences, which can be a challenge for the DNA replication machinery to travel through and replicate correctly. Repetitive DNA sequence can adopt non-B DNA structures, which could block the DNA replication. Prolonged stalling of the replication fork at the endogenous repeats in human cells can have severe consequences such as genome instability that includes repeat expansions, contractions, and chromosome fragility. Several neurological and muscular diseases are caused by a repeat expansion. Furthermore genome instability is the major cause of cancer. This chapter describes some of the important classes of repetitive DNA sequences in the mammalian genome, their ability to form secondary DNA structures, their contribution to replication fork stalling, and models for repeat expansion as well as chromosomal fragility. Included in this chapter are also some of the strategies currently employed to detect changes in DNA replication and proteins that could prevent the repeat-mediated disruption of DNA replication in human cells. Additionally summarized are the consequences of repeat-associated perturbation of the DNA replication, which could lead to specific human diseases.
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31
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Polak U, Li Y, Butler JS, Napierala M. Alleviating GAA Repeat Induced Transcriptional Silencing of the Friedreich's Ataxia Gene During Somatic Cell Reprogramming. Stem Cells Dev 2016; 25:1788-1800. [PMID: 27615158 PMCID: PMC5155629 DOI: 10.1089/scd.2016.0147] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 09/09/2016] [Indexed: 12/13/2022] Open
Abstract
Friedreich's ataxia (FRDA) is the most common autosomal recessive ataxia. This severe neurodegenerative disease is caused by an expansion of guanine-adenine-adenine (GAA) repeats located in the first intron of the frataxin (FXN) gene, which represses its transcription. Although transcriptional silencing is associated with heterochromatin-like changes in the vicinity of the expanded GAAs, the exact mechanism and pathways involved in transcriptional inhibition are largely unknown. As major remodeling of the epigenome is associated with somatic cell reprogramming, modulating chromatin modification pathways during the cellular transition from a somatic to a pluripotent state is likely to generate permanent changes to the epigenetic landscape. We hypothesize that the epigenetic modifications in the vicinity of the GAA repeats can be reversed by pharmacological modulation during somatic cell reprogramming. We reprogrammed FRDA fibroblasts into induced pluripotent stem cells (iPSCs) in the presence of various small molecules that target DNA methylation and histone acetylation and methylation. Treatment of FRDA iPSCs with two compounds, sodium butyrate (NaB) and Parnate, led to an increase in FXN expression and correction of repressive marks at the FXN locus, which persisted for several passages. However, prolonged culture of the epigenetically modified FRDA iPSCs led to progressive expansions of the GAA repeats and a corresponding decrease in FXN expression. Furthermore, we uncovered that differentiation of these iPSCs into neurons also results in resilencing of the FXN gene. Taken together, these results demonstrate that transcriptional repression caused by long GAA repeat tracts can be partially or transiently reversed by altering particular epigenetic modifications, thus revealing possibilities for detailed analyses of silencing mechanism and development of new therapeutic approaches for FRDA.
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Affiliation(s)
- Urszula Polak
- Department of Molecular Carcinogenesis, Center for Cancer Epigenetics, University of Texas MD Anderson Cancer Center, Smithville, Texas
| | - Yanjie Li
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jill Sergesketter Butler
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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32
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Gerhardt J, Bhalla AD, Butler JS, Puckett JW, Dervan PB, Rosenwaks Z, Napierala M. Stalled DNA Replication Forks at the Endogenous GAA Repeats Drive Repeat Expansion in Friedreich's Ataxia Cells. Cell Rep 2016; 16:1218-1227. [PMID: 27425605 PMCID: PMC5028224 DOI: 10.1016/j.celrep.2016.06.075] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 05/31/2016] [Accepted: 06/17/2016] [Indexed: 10/21/2022] Open
Abstract
Friedreich's ataxia (FRDA) is caused by the expansion of GAA repeats located in the Frataxin (FXN) gene. The GAA repeats continue to expand in FRDA patients, aggravating symptoms and contributing to disease progression. The mechanism leading to repeat expansion and decreased FXN transcription remains unclear. Using single-molecule analysis of replicated DNA, we detected that expanded GAA repeats present a substantial obstacle for the replication machinery at the FXN locus in FRDA cells. Furthermore, aberrant origin activation and lack of a proper stress response to rescue the stalled forks in FRDA cells cause an increase in 3'-5' progressing forks, which could enhance repeat expansion and hinder FXN transcription by head-on collision with RNA polymerases. Treatment of FRDA cells with GAA-specific polyamides rescues DNA replication fork stalling and alleviates expansion of the GAA repeats, implicating DNA triplexes as a replication impediment and suggesting that fork stalling might be a therapeutic target for FRDA.
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Affiliation(s)
- Jeannine Gerhardt
- Center for Reproductive Medicine, Weill Cornell Medical College, New York, NY 10065, USA.
| | - Angela D Bhalla
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA
| | - Jill Sergesketter Butler
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA
| | - James W Puckett
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Peter B Dervan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Zev Rosenwaks
- Center for Reproductive Medicine, Weill Cornell Medical College, New York, NY 10065, USA
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA; Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61 704, Poland.
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33
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Li Y, Polak U, Clark AD, Bhalla AD, Chen YY, Li J, Farmer J, Seyer L, Lynch D, Butler JS, Napierala M. Establishment and Maintenance of Primary Fibroblast Repositories for Rare Diseases-Friedreich's Ataxia Example. Biopreserv Biobank 2016; 14:324-9. [PMID: 27002638 PMCID: PMC4991587 DOI: 10.1089/bio.2015.0117] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Friedreich's ataxia (FRDA) represents a rare neurodegenerative disease caused by expansion of GAA trinucleotide repeats in the first intron of the FXN gene. The number of GAA repeats in FRDA patients varies from approximately 60 to <1000 and is tightly correlated with age of onset and severity of the disease symptoms. The heterogeneity of Friedreich's ataxia stresses the need for a large cohort of patient samples to conduct studies addressing the mechanism of disease pathogenesis or evaluate novel therapeutic candidates. Herein, we report the establishment and characterization of an FRDA fibroblast repository, which currently includes 50 primary cell lines derived from FRDA patients and seven lines from mutation carriers. These cells are also a source for generating induced pluripotent stem cell (iPSC) lines by reprogramming, as well as disease-relevant neuronal, cardiac, and pancreatic cells that can then be differentiated from the iPSCs. All FRDA and carrier lines are derived using a standard operating procedure and characterized to confirm mutation status, as well as expression of FXN mRNA and protein. Consideration and significance of creating disease-focused cell line and tissue repositories, especially in the context of rare and heterogeneous disorders, are presented. Although the economic aspect of creating and maintaining such repositories is important, the benefits of easy access to a collection of well-characterized cell lines for the purpose of drug discovery or disease mechanism studies overshadow the associated costs. Importantly, all FRDA fibroblast cell lines collected in our repository are available to the scientific community.
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Affiliation(s)
- Yanjie Li
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Urszula Polak
- Department of Molecular Carcinogenesis, Center for Cancer Epigenetics, University of Texas MD Anderson Cancer Center, Smithville, Texas
| | - Amanda D. Clark
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Angela D. Bhalla
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Yu-Yun Chen
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jixue Li
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jennifer Farmer
- Division of Neurology and Pediatrics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Lauren Seyer
- Division of Neurology and Pediatrics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - David Lynch
- Division of Neurology and Pediatrics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Jill S. Butler
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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Abstract
INTRODUCTION Friedreich's ataxia (FRDA) is an autosomal recessive neurodegenerative disease caused by expansion of a GAA·TTC triplet in the first intron of the FXN gene, encoding the essential mitochondrial protein frataxin. Repeat expansion results in transcriptional silencing through an epigenetic mechanism, resulting in significant decreases in frataxin protein in affected individuals. Since the FXN protein coding sequence is unchanged in FRDA, an attractive therapeutic approach for this disease would be to increase transcription of pathogenic alleles with small molecules that target the silencing mechanism. AREAS COVERED We review the evidence that histone postsynthetic modifications and heterochromatin formation are responsible for FXN gene silencing in FRDA, along with efforts to reverse silencing with drugs that target histone modifying enzymes. Chemical and pharmacological properties of histone deacetylase (HDAC) inhibitors, which reverse silencing, together with enzyme target profiles and kinetics of inhibition, are discussed. Two HDAC inhibitors have been studied in human clinical trials and the properties of these compounds are compared and contrasted. Efforts to improve on bioavailability, metabolic stability, and target activity are reviewed. EXPERT OPINION 2-aminobenzamide class I HDAC inhibitors are attractive therapeutic small molecules for FRDA. These molecules increase FXN gene expression in human neuronal cells derived from patient induced pluripotent stem cells, and in two mouse models for the disease, as well as in circulating lymphocytes in patients treated in a phase Ib clinical trial. Medicinal chemistry efforts have identified compounds with improved brain penetration, metabolic stability and efficacy in the human neuronal cell model. A clinical candidate will soon be identified for further human testing.
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Affiliation(s)
- Elisabetta Soragni
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037 USA
| | - Joel M Gottesfeld
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037 USA
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Stevanoni M, Palumbo E, Russo A. The Replication of Frataxin Gene Is Assured by Activation of Dormant Origins in the Presence of a GAA-Repeat Expansion. PLoS Genet 2016; 12:e1006201. [PMID: 27447727 PMCID: PMC4957762 DOI: 10.1371/journal.pgen.1006201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 06/27/2016] [Indexed: 12/17/2022] Open
Abstract
It is well known that DNA replication affects the stability of several trinucleotide repeats, but whether replication profiles of human loci carrying an expanded repeat differ from those of normal alleles is poorly understood in the endogenous context. We investigated this issue using cell lines from Friedreich's ataxia patients, homozygous for a GAA-repeat expansion in intron 1 of the Frataxin gene. By interphase, FISH we found that in comparison to the normal Frataxin sequence the replication of expanded alleles is slowed or delayed. According to molecular combing, origins never fired within the normal Frataxin allele. In contrast, in mutant alleles dormant origins are recruited within the gene, causing a switch of the prevalent fork direction through the expanded repeat. Furthermore, a global modification of the replication profile, involving origin choice and a differential distribution of unidirectional forks, was observed in the surrounding 850 kb region. These data provide a wide-view of the interplay of events occurring during replication of genes carrying an expanded repeat.
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Affiliation(s)
| | - Elisa Palumbo
- Department of Biology, University of Padova, Padova, Italy
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Chutake YK, Lam CC, Costello WN, Anderson MP, Bidichandani SI. Reversal of epigenetic promoter silencing in Friedreich ataxia by a class I histone deacetylase inhibitor. Nucleic Acids Res 2016; 44:5095-104. [PMID: 26896803 PMCID: PMC4914082 DOI: 10.1093/nar/gkw107] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 02/13/2016] [Accepted: 02/15/2016] [Indexed: 12/27/2022] Open
Abstract
Friedreich ataxia, the most prevalent inherited ataxia, is caused by an expanded GAA triplet-repeat sequence in intron 1 of the FXN gene. Repressive chromatin spreads from the expanded GAA triplet-repeat sequence to cause epigenetic silencing of the FXN promoter via altered nucleosomal positioning and reduced chromatin accessibility. Indeed, deficient transcriptional initiation is the predominant cause of transcriptional deficiency in Friedreich ataxia. Treatment with 109, a class I histone deacetylase (HDAC) inhibitor, resulted in increased level of FXN transcript both upstream and downstream of the expanded GAA triplet-repeat sequence, without any change in transcript stability, suggesting that it acts via improvement of transcriptional initiation. Quantitative analysis of transcriptional initiation via metabolic labeling of nascent transcripts in patient-derived cells revealed a >3-fold increase (P < 0.05) in FXN promoter function. A concomitant 3-fold improvement (P < 0.001) in FXN promoter structure and chromatin accessibility was observed via Nucleosome Occupancy and Methylome Sequencing, a high-resolution in vivo footprint assay for detecting nucleosome occupancy in individual chromatin fibers. No such improvement in FXN promoter function or structure was observed upon treatment with a chemically-related inactive compound (966). Thus epigenetic promoter silencing in Friedreich ataxia is reversible, and the results implicate class I HDACs in repeat-mediated promoter silencing.
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Affiliation(s)
- Yogesh K Chutake
- Department of Pediatrics, University of Oklahoma College of Medicine, Oklahoma City, OK 73104, USA
| | - Christina C Lam
- Department of Pediatrics, University of Oklahoma College of Medicine, Oklahoma City, OK 73104, USA
| | - Whitney N Costello
- Department of Pediatrics, University of Oklahoma College of Medicine, Oklahoma City, OK 73104, USA
| | - Michael P Anderson
- Department of Biochemistry & Molecular Biology, University of Oklahoma College of Medicine, Oklahoma City, OK 73104, USA
| | - Sanjay I Bidichandani
- Department of Pediatrics, University of Oklahoma College of Medicine, Oklahoma City, OK 73104, USA Department of Biostatistics & Epidemiology, University of Oklahoma College of Public Health, Oklahoma City, OK 73104, USA
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Bhalla AD, Khodadadi-Jamayran A, Li Y, Lynch DR, Napierala M. Deep sequencing of mitochondrial genomes reveals increased mutation load in Friedreich's ataxia. Ann Clin Transl Neurol 2016; 3:523-36. [PMID: 27386501 PMCID: PMC4931717 DOI: 10.1002/acn3.322] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 05/12/2016] [Indexed: 12/02/2022] Open
Abstract
Objective Friedreich's ataxia (FRDA) is an autosomal recessive trinucleotide repeat expansion disorder caused by epigenetic silencing of the frataxin gene (FXN). Current research suggests that damage and variation of mitochondrial DNA (mtDNA) contribute to the molecular pathogenesis of FRDA. We sought to establish the extent of the mutation burden across the mitochondrial genome in FRDA cells and investigate the molecular mechanisms connecting FXN downregulation and the acquisition of mtDNA damage. Methods Damage and mutation load in mtDNA of a panel of FRDA and control fibroblasts were determined using qPCR and next‐generation MiSeq sequencing, respectively. The capacity of FRDA and control cells to repair oxidative lesions in their mtDNA was measured using a quantitative DNA damage assay. Comprehensive RNA sequencing gene expression analyses were conducted to assess the status of DNA repair and metabolism genes in FRDA cells. Results Acute or prolonged downregulation of FXN expression resulted in a significant increase in mtDNA damage that translated to a significant elevation of mutation load in mtDNA. The predominant mutations identified throughout the mtDNA were C>T, G>A transitions (P = 0.007). Low FXN expression reduced capacity to repair oxidative damage in mtDNA. Downregulation of FXN expression strongly correlated (r = 0.73) with decreased levels of base excision repair (BER) DNA glycosylase NTHL1. Interpretation Downregulation of FXN expression in FRDA cells elevates mtDNA damage, increases mutation load of the mitochondrial genome, and diminishes DNA repair capacity. Progressive accumulation of mtDNA mutations in vulnerable FRDA patient cells reduces mitochondrial fitness ultimately leading to cell death.
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Affiliation(s)
- Angela D Bhalla
- Department of Biochemistry and Molecular Genetics University of Alabama at Birmingham UAB Stem Cell Institute 1825 University Blvd. Birmingham Alabama 35294
| | - Alireza Khodadadi-Jamayran
- Department of Biochemistry and Molecular Genetics University of Alabama at Birmingham UAB Stem Cell Institute 1825 University Blvd. Birmingham Alabama 35294
| | - Yanjie Li
- Department of Biochemistry and Molecular Genetics University of Alabama at Birmingham UAB Stem Cell Institute 1825 University Blvd. Birmingham Alabama 35294
| | - David R Lynch
- Division of Neurology and Pediatrics Children's Hospital of Philadelphia Abramson Research Center Room 502 Philadelphia Pennsylvania 19104
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics University of Alabama at Birmingham UAB Stem Cell Institute 1825 University Blvd. Birmingham Alabama 35294; Department of Molecular Biomedicine Institute of Bioorganic Chemistry Polish Academy of Sciences Poznan 61-704 Poland
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The expanding biology of the C9orf72 nucleotide repeat expansion in neurodegenerative disease. Nat Rev Neurosci 2016; 17:383-95. [PMID: 27150398 DOI: 10.1038/nrn.2016.38] [Citation(s) in RCA: 151] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A nucleotide repeat expansion (NRE) within the chromosome 9 open reading frame 72 (C9orf72) gene was the first of this type of mutation to be linked to multiple neurological conditions, including amyotrophic lateral sclerosis and frontotemporal dementia. The pathogenic mechanisms through which the C9orf72 NRE contributes to these disorders include loss of C9orf72 function and gain-of-function mechanisms of C9orf72 driven by toxic RNA and protein species encoded by the NRE. These mechanisms have been linked to several cellular defects - including nucleocytoplasmic trafficking deficits and nuclear stress - that have been observed in both patients and animal models.
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Li L, Matsui M, Corey DR. Activating frataxin expression by repeat-targeted nucleic acids. Nat Commun 2016; 7:10606. [PMID: 26842135 PMCID: PMC4742999 DOI: 10.1038/ncomms10606] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 01/04/2016] [Indexed: 12/20/2022] Open
Abstract
Friedreich's ataxia is an incurable genetic disorder caused by a mutant expansion of the trinucleotide GAA within an intronic FXN RNA. This expansion leads to reduced expression of frataxin (FXN) protein and evidence suggests that transcriptional repression is caused by an R-loop that forms between the expanded repeat RNA and complementary genomic DNA. Synthetic agents that increase levels of FXN protein might alleviate the disease. We demonstrate that introducing anti-GAA duplex RNAs or single-stranded locked nucleic acids into patient-derived cells increases FXN protein expression to levels similar to analogous wild-type cells. Our data are significant because synthetic nucleic acids that target GAA repeats can be lead compounds for restoring curative FXN levels. More broadly, our results demonstrate that interfering with R-loop formation can trigger gene activation and reveal a new strategy for upregulating gene expression.
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Affiliation(s)
- Liande Li
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center at Dallas, 6001 Forest Park Road, Dallas, Texas 75390-9041, USA
| | - Masayuki Matsui
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center at Dallas, 6001 Forest Park Road, Dallas, Texas 75390-9041, USA
| | - David R. Corey
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center at Dallas, 6001 Forest Park Road, Dallas, Texas 75390-9041, USA
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