101
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Ramos EM, Gillis T, Mysore JS, Lee J, Gögele M, D'Elia Y, Pichler I, Sequeiros J, Pramstaller PP, Gusella JF, MacDonald ME, Alonso I. Haplotype analysis of the 4p16.3 region in Portuguese families with Huntington's disease. Am J Med Genet B Neuropsychiatr Genet 2015; 168B:135-43. [PMID: 25656686 PMCID: PMC5006842 DOI: 10.1002/ajmg.b.32289] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 11/25/2014] [Indexed: 12/12/2022]
Abstract
Huntington's disease (HD) is a neurodegenerative disorder characterized by involuntary choreic movements, cognitive impairment, and behavioral changes, caused by the expansion of an unstable CAG repeat in HTT. We characterized the genetic diversity of the HD mutation by performing an extensive haplotype analysis of ∼1Mb region flanking HTT in over 300 HD families of Portuguese origin. We observed that haplotype A, marked by HTT delta2642, was enriched in HD chromosomes and carried the two largest expansions reported in the Portuguese population. However, the most frequent HD haplotype B carried one of the largest (+12 CAGs) expansions, which resulted in an allele class change to full penetrance. Despite having a normal CAG distribution skewed to the higher end of the range, these two core haplotypes had similar expanded CAG repeat sizes compared to the other major core haplotypes (C and D) and there was no statistical difference in transmitted repeat instability across haplotypes. We observed a diversity of HTT region haplotypes in both normal and expanded chromosomes, representative of more than one ancestral chromosome underlying HD in Portugal, where multiple independent events on distinct chromosome 4 haplotypes have given rise to expansion into the pathogenic range.
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Affiliation(s)
- Eliana Marisa Ramos
- Center for Human Genetic ResearchMassachusetts General HospitalBostonMassachusettsUSA,UnIGENeIBMC–Institute for Molecular and Cell BiologyUniversity of PortoPortoPortugal
| | - Tammy Gillis
- Center for Human Genetic ResearchMassachusetts General HospitalBostonMassachusettsUSA
| | - Jayalakshmi S. Mysore
- Center for Human Genetic ResearchMassachusetts General HospitalBostonMassachusettsUSA
| | - Jong‐Min Lee
- Center for Human Genetic ResearchMassachusetts General HospitalBostonMassachusettsUSA
| | - Martin Gögele
- Center for BiomedicineEuropean Academy of Bozen/Bolzano (EURAC)BolzanoItaly
| | - Yuri D'Elia
- Center for BiomedicineEuropean Academy of Bozen/Bolzano (EURAC)BolzanoItaly
| | - Irene Pichler
- Center for BiomedicineEuropean Academy of Bozen/Bolzano (EURAC)BolzanoItaly
| | - Jorge Sequeiros
- UnIGENeIBMC–Institute for Molecular and Cell BiologyUniversity of PortoPortoPortugal,CGPPIBMC–Institute for Molecular and Cell BiologyUniversity of PortoPortoPortugal,ICBAS–Instituto de Ciências Biomédicas Abel SalazarUniversity of PortoPortoPortugal
| | - Peter P. Pramstaller
- Center for BiomedicineEuropean Academy of Bozen/Bolzano (EURAC)BolzanoItaly,Department of NeurologyCentral HospitalBolzanoItaly,Department of NeurologyUniversity of LübeckLübeckGermany
| | - James F. Gusella
- Center for Human Genetic ResearchMassachusetts General HospitalBostonMassachusettsUSA
| | - Marcy E. MacDonald
- Center for Human Genetic ResearchMassachusetts General HospitalBostonMassachusettsUSA
| | - Isabel Alonso
- UnIGENeIBMC–Institute for Molecular and Cell BiologyUniversity of PortoPortoPortugal,CGPPIBMC–Institute for Molecular and Cell BiologyUniversity of PortoPortoPortugal,ICBAS–Instituto de Ciências Biomédicas Abel SalazarUniversity of PortoPortoPortugal
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102
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Usdin K, House NCM, Freudenreich CH. Repeat instability during DNA repair: Insights from model systems. Crit Rev Biochem Mol Biol 2015; 50:142-67. [PMID: 25608779 DOI: 10.3109/10409238.2014.999192] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The expansion of repeated sequences is the cause of over 30 inherited genetic diseases, including Huntington disease, myotonic dystrophy (types 1 and 2), fragile X syndrome, many spinocerebellar ataxias, and some cases of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Repeat expansions are dynamic, and disease inheritance and progression are influenced by the size and the rate of expansion. Thus, an understanding of the various cellular mechanisms that cooperate to control or promote repeat expansions is of interest to human health. In addition, the study of repeat expansion and contraction mechanisms has provided insight into how repair pathways operate in the context of structure-forming DNA, as well as insights into non-canonical roles for repair proteins. Here we review the mechanisms of repeat instability, with a special emphasis on the knowledge gained from the various model systems that have been developed to study this topic. We cover the repair pathways and proteins that operate to maintain genome stability, or in some cases cause instability, and the cross-talk and interactions between them.
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Affiliation(s)
- Karen Usdin
- Laboratory of Cell and Molecular Biology, NIDDK, NIH , Bethesda, MD , USA
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103
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Epidemiology of Huntington's disease in Finland. Parkinsonism Relat Disord 2015; 21:46-9. [DOI: 10.1016/j.parkreldis.2014.10.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 09/22/2014] [Accepted: 10/27/2014] [Indexed: 11/24/2022]
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104
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Southwell AL, Skotte NH, Kordasiewicz HB, Østergaard ME, Watt AT, Carroll JB, Doty CN, Villanueva EB, Petoukhov E, Vaid K, Xie Y, Freier SM, Swayze EE, Seth PP, Bennett CF, Hayden MR. In vivo evaluation of candidate allele-specific mutant huntingtin gene silencing antisense oligonucleotides. Mol Ther 2014; 22:2093-2106. [PMID: 25101598 PMCID: PMC4429695 DOI: 10.1038/mt.2014.153] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 07/23/2014] [Indexed: 11/08/2022] Open
Abstract
Huntington disease (HD) is a dominant, genetic neurodegenerative disease characterized by progressive loss of voluntary motor control, psychiatric disturbance, and cognitive decline, for which there is currently no disease-modifying therapy. HD is caused by the expansion of a CAG tract in the huntingtin (HTT) gene. The mutant HTT protein (muHTT) acquires toxic functions, and there is significant evidence that muHTT lowering would be therapeutically efficacious. However, the wild-type HTT protein (wtHTT) serves vital functions, making allele-specific muHTT lowering strategies potentially safer than nonselective strategies. CAG tract expansion is associated with single nucleotide polymorphisms (SNPs) that can be targeted by gene silencing reagents such as antisense oligonucleotides (ASOs) to accomplish allele-specific muHTT lowering. Here we evaluate ASOs targeted to HD-associated SNPs in acute in vivo studies including screening, distribution, duration of action and dosing, using a humanized mouse model of HD, Hu97/18, that is heterozygous for the targeted SNPs. We have identified four well-tolerated lead ASOs that potently and selectively silence muHTT at a broad range of doses throughout the central nervous system for 16 weeks or more after a single intracerebroventricular (ICV) injection. With further validation, these ASOs could provide a therapeutic option for individuals afflicted with HD.
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Affiliation(s)
- Amber L Southwell
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Niels H Skotte
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | | | - Jeffrey B Carroll
- Behavioral Neuroscience Program, Department of Psychology, Western Washington University, Bellingham, Washington, USA
| | - Crystal N Doty
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Erika B Villanueva
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Eugenia Petoukhov
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kuljeet Vaid
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yuanyun Xie
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | | | | | - Michael R Hayden
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada.
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105
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Semaka A, Kay C, Belfroid RDM, Bijlsma EK, Losekoot M, van Langen IM, van Maarle MC, Oosterloo M, Hayden MR, van Belzen MJ. A new mutation for Huntington disease following maternal transmission of an intermediate allele. Eur J Med Genet 2014; 58:28-30. [PMID: 25464109 DOI: 10.1016/j.ejmg.2014.11.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 11/12/2014] [Indexed: 10/24/2022]
Abstract
New mutations for Huntington disease (HD) originate from CAG repeat expansion of intermediate alleles (27-35 CAG). Expansions of such alleles into the pathological range (≥ 36 CAG) have been exclusively observed in paternal transmission. We report the occurrence of a new mutation that defies the paternal expansion bias normally observed in HD. A maternal intermediate allele with 33 CAG repeats expanded in transmission to 48 CAG repeats causing a de novo case of HD in the family. Retrospectively, the mother presented with cognitive decline, but HD was never considered in the differential diagnosis. She was diagnosed with dementia and testing for HD was only performed after her daughter had been diagnosed. This observation of an intermediate allele expanding into the full penetrance HD range after maternal transmission has important implications for genetic counselling of females with intermediate repeats.
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Affiliation(s)
- Alicia Semaka
- Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Chris Kay
- Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada
| | - René D M Belfroid
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Emilia K Bijlsma
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Monique Losekoot
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Irene M van Langen
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Merel C van Maarle
- Department of Clinical Genetics, Academic Medical Center, Amsterdam, The Netherlands
| | - Mayke Oosterloo
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands; Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Michael R Hayden
- Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Martine J van Belzen
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands.
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106
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Skotte NH, Southwell AL, Østergaard ME, Carroll JB, Warby SC, Doty CN, Petoukhov E, Vaid K, Kordasiewicz H, Watt AT, Freier SM, Hung G, Seth PP, Bennett CF, Swayze EE, Hayden MR. Allele-specific suppression of mutant huntingtin using antisense oligonucleotides: providing a therapeutic option for all Huntington disease patients. PLoS One 2014; 9:e107434. [PMID: 25207939 PMCID: PMC4160241 DOI: 10.1371/journal.pone.0107434] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 08/11/2014] [Indexed: 01/10/2023] Open
Abstract
Huntington disease (HD) is an inherited, fatal neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin gene. The mutant protein causes neuronal dysfunction and degeneration resulting in motor dysfunction, cognitive decline, and psychiatric disturbances. Currently, there is no disease altering treatment, and symptomatic therapy has limited benefit. The pathogenesis of HD is complicated and multiple pathways are compromised. Addressing the problem at its genetic root by suppressing mutant huntingtin expression is a promising therapeutic strategy for HD. We have developed and evaluated antisense oligonucleotides (ASOs) targeting single nucleotide polymorphisms that are significantly enriched on HD alleles (HD-SNPs). We describe our structure-activity relationship studies for ASO design and find that adjusting the SNP position within the gap, chemical modifications of the wings, and shortening the unmodified gap are critical for potent, specific, and well tolerated silencing of mutant huntingtin. Finally, we show that using two distinct ASO drugs targeting the two allelic variants of an HD-SNP could provide a therapeutic option for all persons with HD; allele-specifically for roughly half, and non-specifically for the remainder.
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Affiliation(s)
- Niels H. Skotte
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Amber L. Southwell
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Jeffrey B. Carroll
- Behavioral Neuroscience Program, Department of Psychology, Western Washington University, Bellingham, Washington, United States of America
| | - Simon C. Warby
- Center for Advanced Research in Sleep Medicine, Department of Psychiatry, University of Montréal, Montréal, Quebec, Canada
| | - Crystal N. Doty
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Eugenia Petoukhov
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kuljeet Vaid
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Andrew T. Watt
- ISIS Pharmaceuticals, Carlsbad, California, United States of America
| | - Susan M. Freier
- ISIS Pharmaceuticals, Carlsbad, California, United States of America
| | - Gene Hung
- ISIS Pharmaceuticals, Carlsbad, California, United States of America
| | - Punit P. Seth
- ISIS Pharmaceuticals, Carlsbad, California, United States of America
| | - C. Frank Bennett
- ISIS Pharmaceuticals, Carlsbad, California, United States of America
| | - Eric E. Swayze
- ISIS Pharmaceuticals, Carlsbad, California, United States of America
| | - Michael R. Hayden
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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107
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Drouet V, Ruiz M, Zala D, Feyeux M, Auregan G, Cambon K, Troquier L, Carpentier J, Aubert S, Merienne N, Bourgois-Rocha F, Hassig R, Rey M, Dufour N, Saudou F, Perrier AL, Hantraye P, Déglon N. Allele-specific silencing of mutant huntingtin in rodent brain and human stem cells. PLoS One 2014; 9:e99341. [PMID: 24926995 PMCID: PMC4057216 DOI: 10.1371/journal.pone.0099341] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 05/14/2014] [Indexed: 12/11/2022] Open
Abstract
Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder resulting from polyglutamine expansion in the huntingtin (HTT) protein and for which there is no cure. Although suppression of both wild type and mutant HTT expression by RNA interference is a promising therapeutic strategy, a selective silencing of mutant HTT represents the safest approach preserving WT HTT expression and functions. We developed small hairpin RNAs (shRNAs) targeting single nucleotide polymorphisms (SNP) present in the HTT gene to selectively target the disease HTT isoform. Most of these shRNAs silenced, efficiently and selectively, mutant HTT in vitro. Lentiviral-mediated infection with the shRNAs led to selective degradation of mutant HTT mRNA and prevented the apparition of neuropathology in HD rat's striatum expressing mutant HTT containing the various SNPs. In transgenic BACHD mice, the mutant HTT allele was also silenced by this approach, further demonstrating the potential for allele-specific silencing. Finally, the allele-specific silencing of mutant HTT in human embryonic stem cells was accompanied by functional recovery of the vesicular transport of BDNF along microtubules. These findings provide evidence of the therapeutic potential of allele-specific RNA interference for HD.
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Affiliation(s)
- Valérie Drouet
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
| | - Marta Ruiz
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
| | - Diana Zala
- Institut Curie, Orsay, France
- UMR3306, Centre National de Recherché Scientifique (CNRS), Orsay, France
- U1005, Institut National de la Santé et de la Recherche Médicale (INSERM), Orsay France
| | - Maxime Feyeux
- U861, Institut National de la Santé et de la Recherche Médicale (INSERM), AFM, Evry, France
- UEVE U861, I-STEM, AFM, Evry, France
| | - Gwennaëlle Auregan
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
| | - Karine Cambon
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
| | - Laetitia Troquier
- Department of Clinical Neurosciences (DNC), Lausanne University Hospital (CHUV), Lausanne, Switzerland
| | - Johann Carpentier
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
| | | | - Nicolas Merienne
- Department of Clinical Neurosciences (DNC), Lausanne University Hospital (CHUV), Lausanne, Switzerland
| | - Fany Bourgois-Rocha
- U861, Institut National de la Santé et de la Recherche Médicale (INSERM), AFM, Evry, France
- UEVE U861, I-STEM, AFM, Evry, France
| | - Raymonde Hassig
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
| | - Maria Rey
- Department of Clinical Neurosciences (DNC), Lausanne University Hospital (CHUV), Lausanne, Switzerland
| | - Noëlle Dufour
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
| | - Frédéric Saudou
- Institut Curie, Orsay, France
- UMR3306, Centre National de Recherché Scientifique (CNRS), Orsay, France
- U1005, Institut National de la Santé et de la Recherche Médicale (INSERM), Orsay France
| | - Anselme L. Perrier
- U861, Institut National de la Santé et de la Recherche Médicale (INSERM), AFM, Evry, France
- UEVE U861, I-STEM, AFM, Evry, France
| | - Philippe Hantraye
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
| | - Nicole Déglon
- Institute of Biomedical Imaging (I2BM) and Molecular Imaging Research Center (MIRCen), Atomic Energy Commission (CEA), Fontenay-aux-Roses, France
- URA2210, Centre National de Recherché Scientifique (CNRS), Fontenay-aux-Roses, France
- Department of Clinical Neurosciences (DNC), Lausanne University Hospital (CHUV), Lausanne, Switzerland
- * E-mail:
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108
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Fiszer A, Krzyzosiak WJ. Oligonucleotide-based strategies to combat polyglutamine diseases. Nucleic Acids Res 2014; 42:6787-810. [PMID: 24848018 PMCID: PMC4066792 DOI: 10.1093/nar/gku385] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Considerable advances have been recently made in understanding the molecular aspects of pathogenesis and in developing therapeutic approaches for polyglutamine (polyQ) diseases. Studies on pathogenic mechanisms have extended our knowledge of mutant protein toxicity, confirmed the toxicity of mutant transcript and identified other toxic RNA and protein entities. One very promising therapeutic strategy is targeting the causative gene expression with oligonucleotide (ON) based tools. This straightforward approach aimed at halting the early steps in the cascade of pathogenic events has been widely tested for Huntington's disease and spinocerebellar ataxia type 3. In this review, we gather information on the use of antisense oligonucleotides and RNA interference triggers for the experimental treatment of polyQ diseases in cellular and animal models. We present studies testing non-allele-selective and allele-selective gene silencing strategies. The latter include targeting SNP variants associated with mutations or targeting the pathologically expanded CAG repeat directly. We compare gene silencing effectors of various types in a number of aspects, including their design, efficiency in cell culture experiments and pre-clinical testing. We discuss advantages, current limitations and perspectives of various ON-based strategies used to treat polyQ diseases.
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Affiliation(s)
- Agnieszka Fiszer
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Wlodzimierz J Krzyzosiak
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
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109
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Kay C, Skotte N, Southwell A, Hayden M. Personalized gene silencing therapeutics for Huntington disease. Clin Genet 2014; 86:29-36. [DOI: 10.1111/cge.12385] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 03/17/2014] [Accepted: 03/17/2014] [Indexed: 01/14/2023]
Affiliation(s)
- C. Kay
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute; University of British Columbia; Vancouver Canada
| | - N.H. Skotte
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute; University of British Columbia; Vancouver Canada
| | - A.L. Southwell
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute; University of British Columbia; Vancouver Canada
| | - M.R. Hayden
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute; University of British Columbia; Vancouver Canada
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110
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Jiang H, Sun YM, Hao Y, Yan YP, Chen K, Xin SH, Tang YP, Li XH, Jun T, Chen YY, Liu ZJ, Wang CR, Li H, Pei Z, Shang HF, Zhang BR, Gu WH, Wu ZY, Tang BS, Burgunder JM. Huntingtin gene CAG repeat numbers in Chinese patients with Huntington's disease and controls. Eur J Neurol 2014; 21:637-42. [PMID: 24471773 DOI: 10.1111/ene.12366] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Accepted: 12/17/2013] [Indexed: 02/05/2023]
Affiliation(s)
- H. Jiang
- Department of Neurology; Xiangya Hospital; Central South University; Changsha China
- Key Laboratory of Hunan Province in Neurodegenerative Disorders; State Key Laboratory of Medical Genetics of China; Central South University; Changsha China
| | - Y. M. Sun
- Department of Neurology; Institute of Neurology; Huashan Hospital; Shanghai Medical College; Fudan University; Shanghai China
| | - Y. Hao
- Department of Neurology; China−Japan Friendship Hospital; Beijing China
| | - Y. P. Yan
- Department of Neurology; Second Affiliated Hospital; College of Medicine; Zhejiang University; Hangzhou China
| | - K. Chen
- Department of Neurology; West China Hospital; Sichuan University; Chengdu China
| | - S. H. Xin
- First Affiliated Hospital of Sun Yat-Sen University; Guangzhou China
| | - Y. P. Tang
- Department of Medical Genetics; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
| | - X. H. Li
- First Affiliated Hospital of Sun Yat-Sen University; Guangzhou China
| | - T. Jun
- Department of Neurology; Second Affiliated Hospital; College of Medicine; Zhejiang University; Hangzhou China
| | - Y. Y. Chen
- Department of Neurology; China−Japan Friendship Hospital; Beijing China
| | - Z. J. Liu
- Department of Neurology; Institute of Neurology; Huashan Hospital; Shanghai Medical College; Fudan University; Shanghai China
| | - C. R. Wang
- Department of Neurology; Xiangya Hospital; Central South University; Changsha China
| | - H. Li
- Department of Medical Genetics; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
| | - Z. Pei
- First Affiliated Hospital of Sun Yat-Sen University; Guangzhou China
| | - H. F. Shang
- Department of Neurology; West China Hospital; Sichuan University; Chengdu China
| | - B. R. Zhang
- Department of Neurology; Second Affiliated Hospital; College of Medicine; Zhejiang University; Hangzhou China
| | - W. H. Gu
- Department of Neurology; China−Japan Friendship Hospital; Beijing China
| | - Z. Y. Wu
- Department of Neurology; Institute of Neurology; Huashan Hospital; Shanghai Medical College; Fudan University; Shanghai China
| | - B. S. Tang
- Department of Neurology; Xiangya Hospital; Central South University; Changsha China
| | - J.-M. Burgunder
- Department of Neurology; Xiangya Hospital; Central South University; Changsha China
- Department of Neurology; West China Hospital; Sichuan University; Chengdu China
- First Affiliated Hospital of Sun Yat-Sen University; Guangzhou China
- Swiss Huntington's Disease Centre; Department of Neurology; University of Bern; NeuroBu Clinics; Bern Switzerland
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111
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Pulkes T, Papsing C, Wattanapokayakit S, Mahasirimongkol S. CAG-Expansion Haplotype Analysis in a Population with a Low Prevalence of Huntington's Disease. J Clin Neurol 2014; 10:32-6. [PMID: 24465260 PMCID: PMC3896646 DOI: 10.3988/jcn.2014.10.1.32] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 08/07/2013] [Accepted: 08/07/2013] [Indexed: 11/23/2022] Open
Abstract
Background and Purpose The prevalence of Huntington's disease (HD) among East Asians is less than one-tenth of that among Caucasians. Such a low prevalence may be attributable to a lack of carriers of specific predisposing haplogroups associated with the high instability of the Huntingtin gene (HTT). The aim of this study was to evaluate the association between specific HTT haplogroups and the occurrence of HD in a Thai population. Methods CAG-repeat sizes and HTT haplotypes were analyzed in 18 Thai HD patients and 215 control subjects. Twenty-two tagging single-nucleotide polymorphisms (tSNPs) were genotyped. Results Only 18 patients from 15 unrelated families were identified over the last 17 years. Pathological CAG-repeat alleles ranged from 39 to 48 repeats (43.5±3.0, mean±SD), and normal alleles ranged from 9 to 24 repeats (16.49±1.74). Only two of the chromosomes studied comprised intermediate alleles. Unlike the Caucasian data, all but 1 of the 22 tSNPs were not associated with the occurrence of HD. The predisposing haplogroups for Caucasian HD (haplogroups A1 and A2) are very rare in Thai patients (<4%). Both HD and normal chromosomes are commonly haplogroups A5 and C, in contrast to the case for Chinese and Japanese patients, in whom only haplogroup C was common in HD chromosomes. The frequency of CAG-repeat sizes of haplogroup A5 and C were also similarly distributed. Conclusions HD chromosomes of Thai patients may arise randomly from each haplogroup, with a similar mutation rate. This rate is much lower than the CAG expansions from Caucasian HD haplogroups. These data suggest that the different mechanisms underlie CAG expansion in Thai and Caucasian patients.
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Affiliation(s)
- Teeratorn Pulkes
- Department of Neurology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Chutima Papsing
- Department of Neurology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Sukanya Wattanapokayakit
- Department of Medical Sciences, Medical Genetic Section, National Institute of Health, Ministry of Public Health, Nonthaburi, Thailand
| | - Surakameth Mahasirimongkol
- Department of Medical Sciences, Medical Genetic Section, National Institute of Health, Ministry of Public Health, Nonthaburi, Thailand
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112
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Semaka A, Hayden M. Evidence-based genetic counselling implications for Huntington disease intermediate allele predictive test results. Clin Genet 2014; 85:303-11. [DOI: 10.1111/cge.12324] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 11/18/2013] [Accepted: 11/18/2013] [Indexed: 11/29/2022]
Affiliation(s)
- A. Semaka
- Centre for Molecular Medicine and Therapeutics; University of British Columbia; Vancouver British Columbia Canada
| | - M.R. Hayden
- Centre for Molecular Medicine and Therapeutics; University of British Columbia; Vancouver British Columbia Canada
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113
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Melamed O, Behar DM, Bram C, Magal N, Pras E, Reznik-Wolf H, Borochowitz ZU, Davidov B, Mor-Cohen R, Baris HN. Founder mutation for Huntington disease in Caucasus Jews. Clin Genet 2014; 87:167-72. [PMID: 24405192 DOI: 10.1111/cge.12344] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 01/05/2014] [Accepted: 01/06/2014] [Indexed: 11/29/2022]
Abstract
Huntington disease (HD), an autosomal dominant disorder involving HTT, is characterized by chorea, psychiatric illness and cognitive decline. Diagnosis and age of onset depend on the degree of expansion of the trinucleotide CAG repeat within the gene. The prevalence of HD is known for Europeans but has not been studied in the Israeli population. Between 2006 and 2011 we diagnosed in our adult genetics clinic ten HD probands, nine of whom were Caucasus Jews (CJ) (Azerbaijani), and one Ashkenazi Jewish. We performed haplotype analysis to look for evidence of a founder mutation, and found that of the nine CJ, eight shared the same haplotype that was compatible with the A1 haplogroup. We calculated the coalescence age of the mutation to be between 80 and 150 years. Ninety percent of our HD patients are CJ, as are 27% of the HD patients in Israel, although the CJ comprise only 1.4% of the Israeli population. Our findings suggest a higher prevalence of HD among CJ compared to the general Israeli population and are consistent with a recent founder mutation. We recommend a higher degree of suspicion for HD in CJ with subtle clinical findings.
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Affiliation(s)
- O Melamed
- The Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Hospital, Petah Tikva, Israel
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114
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Abstract
Of the neurodegenerative diseases presented in this book, Huntington's disease (HD) stands as the archetypal autosomal dominantly inherited neurodegenerative disorder. Its occurrence through generations of affected families was noted long before the basic genetic underpinnings of hereditary diseases was understood. The early classification of HD as a distinct hereditary neurodegenerative disorder allowed the study of this disease to lead the way in the development of our understanding of the mechanisms of human genetic disorders. Following its clinical and pathologic characterization, the causative genetic mutation in HD was subsequently identified as a trinucleotide (CAG) repeat expansion in the huntingtin (HTT) gene, and consequently, the HTT gene and huntingtin protein have been studied in great detail. Despite this concentrated effort, there is still much about the function of huntingtin that still remains unknown. Presented in this chapter is an overview of the current knowledge on the normal function of huntingtin and some of the potential neurobiologic mechanisms by which the mutant HTT gene may mediate neurodegeneration in HD.
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Affiliation(s)
- Rebecca A G De Souza
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, Child and Family Research Institute, University of British Columbia, 950 West 28th Avenue, Room 2020, Vancouver, BC, V5Z 4H4, Canada
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115
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Evers MM, Tran HD, Zalachoras I, Meijer OC, den Dunnen JT, van Ommen GJB, Aartsma-Rus A, van Roon-Mom WMC. Preventing formation of toxic N-terminal huntingtin fragments through antisense oligonucleotide-mediated protein modification. Nucleic Acid Ther 2013; 24:4-12. [PMID: 24380395 DOI: 10.1089/nat.2013.0452] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Huntington's disease (HD) is a progressive autosomal dominant disorder, caused by a CAG repeat expansion in the HTT gene, which results in expansion of a polyglutamine stretch at the N-terminal end of the huntingtin protein. Several studies have implicated the importance of proteolytic cleavage of mutant huntingtin in HD pathogenesis and it is generally accepted that N-terminal huntingtin fragments are more toxic than full-length protein. Important cleavage sites are encoded by exon 12 of HTT. Here we report proof of concept using antisense oligonucleotides to induce skipping of exon 12 in huntingtin pre-mRNA, thereby preventing the formation of a 586 amino acid N-terminal huntingtin fragment implicated in HD toxicity. In vitro studies showed successful exon skipping and appearance of a shorter huntingtin protein. Cleavage assays showed reduced 586 amino acid N-terminal huntingtin fragments in the treated samples. In vivo studies revealed exon skipping after a single injection of antisense oligonucleotides in the mouse striatum. Recent advances to inhibit the formation of mutant huntingtin using oligonucleotides seem promising therapeutic strategies for HD. Nevertheless, huntingtin is an essential protein and total removal has been shown to result in progressive neurodegeneration in vivo. Our proof of concept shows a completely novel approach to reduce mutant huntingtin toxicity not by reducing its expressing levels, but by modifying the huntingtin protein.
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Affiliation(s)
- Melvin M Evers
- 1 Department of Human Genetics, Leiden University Medical Center , The Netherlands
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116
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Martí E, Estivill X. Small non-coding RNAs add complexity to the RNA pathogenic mechanisms in trinucleotide repeat expansion diseases. Front Mol Neurosci 2013; 6:45. [PMID: 24348326 PMCID: PMC3848198 DOI: 10.3389/fnmol.2013.00045] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 11/12/2013] [Indexed: 12/02/2022] Open
Abstract
Trinucleotide-repeat expansion diseases (TREDs) are a group of inherited human genetic disorders normally involving late-onset neurological/neurodegenerative affectation. Trinucleotide-repeat expansions occur in coding and non-coding regions of unique genes that typically result in protein and RNA toxic gain of function, respectively. In polyglutamine (polyQ) disorders caused by an expanded CAG repeat in the coding region of specific genes, neuronal dysfunction has been traditionally linked to the long polyQ stretch. However, a number of evidences suggest a detrimental role of the expanded/mutant mRNA, which may contribute to cell function impairment. In this review we describe the mechanisms of RNA-induced toxicity in TREDs with special focus in small-non-coding RNA pathogenic mechanisms and we summarize and comment on translational approaches targeting the expanded trinucleotide-repeat for disease modifying therapies.
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Affiliation(s)
- Eulàlia Martí
- Genomics and Disease, Bioinformatics and Genomics Programme, Centre for Genomic Regulation Barcelona, Spain ; Universitat Pompeu Fabra Barcelona, Spain
| | - Xavier Estivill
- Genomics and Disease, Bioinformatics and Genomics Programme, Centre for Genomic Regulation Barcelona, Spain ; Universitat Pompeu Fabra Barcelona, Spain
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117
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Vázquez-Mojena Y, Laguna-Salvia L, Laffita-Mesa JM, González-Zaldívar Y, Almaguer-Mederos LE, Rodríguez-Labrada R, Almaguer-Gotay D, Zayas-Feria P, Velázquez-Pérez L. Genetic features of Huntington disease in Cuban population: Implications for phenotype, epidemiology and predictive testing. J Neurol Sci 2013; 335:101-4. [DOI: 10.1016/j.jns.2013.08.037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 08/22/2013] [Accepted: 08/26/2013] [Indexed: 10/26/2022]
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118
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Semaka A, Kay C, Doty CN, Collins JA, Tam N, Hayden MR. High frequency of intermediate alleles on Huntington disease-associated haplotypes in British Columbia's general population. Am J Med Genet B Neuropsychiatr Genet 2013; 162B:864-71. [PMID: 24038799 DOI: 10.1002/ajmg.b.32193] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 07/11/2013] [Indexed: 11/08/2022]
Abstract
Intermediate alleles (27-35 CAG, IAs) for Huntington disease (HD) usually do not confer the disease phenotype but are prone to CAG repeat instability. Consequently, offspring are at-risk of inheriting an expanded allele in the HD range (≥36 CAG). IAs that expand into a new mutation have been hypothesized to be more susceptible to instability compared to IAs identified on the non-HD side of a family from the general population. Frequency estimates for IAs are limited and have largely been determined using clinical samples of HD or related disorders, which may result in an ascertainment bias. This study aimed to establish the frequency of IAs in a sample of a British Columbia's (B.C.) general population with no known association to HD and examine the haplotype of new mutation and general population IAs. CAG sizing was performed on 1,600 DNA samples from B.C.'s general population. Haplotypes were determined using 22 tagging SNPs across the HTT gene. 5.8% of individuals were found to have an IA, of which 60% were on HD-associated haplotypes. There was no difference in the haplotype distribution of new mutation and general population IAs. These findings suggest that IAs are relatively frequent in the general population and are often found on haplotypes associated with expanded CAG lengths. There is likely no difference in the propensity of new mutation and general population IAs to expand into the disease range given that they are both found on disease-associated haplotypes. These findings have important implications for clinical practice.
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Affiliation(s)
- Alicia Semaka
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada
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119
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Nielsen TT, Nielsen JE. Antisense gene silencing: therapy for neurodegenerative disorders? Genes (Basel) 2013; 4:457-84. [PMID: 24705213 PMCID: PMC3924827 DOI: 10.3390/genes4030457] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 07/11/2013] [Accepted: 08/13/2013] [Indexed: 01/17/2023] Open
Abstract
Since the first reports that double-stranded RNAs can efficiently silence gene expression in C. elegans, the technology of RNA interference (RNAi) has been intensively exploited as an experimental tool to study gene function. With the subsequent discovery that RNAi could also be applied to mammalian cells, the technology of RNAi expanded from being a valuable experimental tool to being an applicable method for gene-specific therapeutic regulation, and much effort has been put into further refinement of the technique. This review will focus on how RNAi has developed over the years and how the technique is exploited in a pre-clinical and clinical perspective in relation to neurodegenerative disorders.
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Affiliation(s)
- Troels T Nielsen
- Danish Dementia Research Centre, Neurogenetics Clinic, Department of Neurology, Section 6702, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, DK-2100, Copenhagen Ø, Denmark.
| | - Jørgen E Nielsen
- Danish Dementia Research Centre, Neurogenetics Clinic, Department of Neurology, Section 6702, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, DK-2100, Copenhagen Ø, Denmark
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120
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Houge G, Bruland O, Bjørnevoll I, Hayden MR, Semaka A. De novo Huntington disease caused by 26-44 CAG repeat expansion on a low-risk haplotype. Neurology 2013; 81:1099-100. [PMID: 23946314 DOI: 10.1212/wnl.0b013e3182a4a4af] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Gunnar Houge
- From the Center for Medical Genetics and Molecular Medicine (G.H., O.B.), Haukeland University Hospital, Bergen; Section for Medical Genetics (I.B.), Department of Pathology, St. Olavs Hospital, Trondheim, Norway; Centre for Molecular Medicine and Therapeutics (M.R.H., A.S.), Vancouver; and University of British Columbia (M.R.H., A.S.), Vancouver, Canada
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121
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Semaka A, Kay C, Doty C, Collins JA, Bijlsma EK, Richards F, Goldberg YP, Hayden MR. CAG size-specific risk estimates for intermediate allele repeat instability in Huntington disease. J Med Genet 2013; 50:696-703. [PMID: 23896435 DOI: 10.1136/jmedgenet-2013-101796] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION New mutations for Huntington disease (HD) occur due to CAG repeat instability of intermediate alleles (IA). IAs have between 27 and 35 CAG repeats, a range just below the disease threshold of 36 repeats. While they usually do not confer the HD phenotype, IAs are prone to paternal germline CAG repeat instability. Consequently, they may expand into the HD range upon transmission to the next generation, producing a new mutation. Quantified risk estimates for IA repeat instability are extremely limited but needed to inform clinical practice. METHODS Using small-pool PCR of sperm DNA from Caucasian men, we examined the frequency and magnitude of CAG repeat instability across the entire range of intermediate CAG sizes. The CAG size-specific risk estimates generated are based on the largest sample size ever examined, including 30 IAs and 18 198 sperm. RESULTS Our findings demonstrate a significant risk of new mutations. While all intermediate CAG sizes demonstrated repeat expansion into the HD range, alleles with 34 and 35 CAG repeats were associated with the highest risk of a new mutation (2.4% and 21.0%, respectively). IAs with ≥33 CAG repeats showed a dramatic increase in the frequency of instability and a switch towards a preponderance of repeat expansions over contractions. CONCLUSIONS These data provide novel insights into the origins of new mutations for HD. The CAG size-specific risk estimates inform clinical practice and provide accurate risk information for persons who receive an IA predictive test result.
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Affiliation(s)
- Alicia Semaka
- Department of Medical Genetics, Centre for Molecular Medicine & Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
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122
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Cruz-Mariño T, Laffita-Mesa JM, Gonzalez-Zaldivar Y, Velazquez-Santos M, Aguilera-Rodriguez R, Estupinan-Rodriguez A, Vazquez-Mojena Y, Macleod P, Paneque M, Velazquez-Perez L. Large normal and intermediate alleles in the context of SCA2 prenatal diagnosis. J Genet Couns 2013; 23:89-96. [PMID: 23813298 DOI: 10.1007/s10897-013-9615-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Accepted: 05/22/2013] [Indexed: 12/22/2022]
Abstract
In 2001 a program for predictive testing of Spinocerebellar Ataxia type 2 was developed in Cuba, based on the detection of an abnormal CAG trinucleotide repeat expansion in the ATXN2 gene. A descriptive study was designed to assess the implications of ATXN2 large normal and intermediate alleles in the context of the SCA2 Prenatal Diagnosis Program. Four clinical scenarios were selected based upon the behaviour of large normal and intermediate alleles when passing from one generation to the next, showing expansions, contractions, or stability in the CAG repeat size. In some populations, traditional Mendelian risk figures of 0 % or 50 % may not be applicable due to the high frequency of unstable large normal alleles. Couples with no family history of SCA2 may have a >0 % risk of having an affected offspring. Similarly, couples in which there is both an expanded and a large normal allele may have a recurrence risk >50 %. It is imperative that these issues be addressed with these couples during genetic counseling. These recurrence risks have to be carefully estimated in the presence of such alleles (particularly alleles ≥27 CAG repeats), carriers need to be aware of the potential risk for their descendants, and programs for prenatal diagnosis must be available for them.
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Affiliation(s)
- Tania Cruz-Mariño
- Predictive Genetics Department, Center for the Research and Rehabilitation of Hereditary Ataxias, Reparto Edecio Pérez, Carretera Vía Habana, Holguín, Cuba, 80100,
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123
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Clabough EBD. Huntington's disease: the past, present, and future search for disease modifiers. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2013; 86:217-33. [PMID: 23766742 PMCID: PMC3670441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Huntington's disease (HD) is an autosomal dominant genetic disorder that specifically causes neurodegeneration of striatal neurons, resulting in a triad of symptoms that includes emotional, cognitive, and motor disturbances. The HD mutation causes a polyglutamine repeat expansion within the N-terminal of the huntingtin (Htt) protein. This expansion causes aggregate formation within the cytosol and nucleus due to the presence of misfolded mutant Htt, as well as altered interactions with Htt's multiple binding partners, and changes in post-translational Htt modifications. The present review charts efforts toward a therapy that delays age of onset or slows symptom progression in patients affected by HD, as there is currently no effective treatment. Although silencing Htt expression appears promising as a disease modifying treatment, it should be attempted with caution in light of Htt's essential roles in neural maintenance and development. Other therapeutic targets include those that boost aggregate dissolution, target excitotoxicity and metabolic issues, and supplement growth factors.
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Affiliation(s)
- Erin B D Clabough
- Randolph-Macon College, Department of Biology, Ashland, Virginia 23005, USA.
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124
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Baine FK, Kay C, Ketelaar ME, Collins JA, Semaka A, Doty CN, Krause A, Greenberg LJ, Hayden MR. Huntington disease in the South African population occurs on diverse and ethnically distinct genetic haplotypes. Eur J Hum Genet 2013; 21:1120-7. [PMID: 23463025 DOI: 10.1038/ejhg.2013.2] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 12/12/2012] [Accepted: 12/28/2012] [Indexed: 11/09/2022] Open
Abstract
Huntington disease (HD) is a neurodegenerative disorder resulting from the expansion of a CAG trinucleotide repeat in the huntingtin (HTT) gene. Worldwide prevalence varies geographically with the highest figures reported in populations of European ancestry. HD in South Africa has been reported in Caucasian, black and mixed subpopulations, with similar estimated prevalence in the Caucasian and mixed groups and a lower estimate in the black subpopulation. Recent studies have associated specific HTT haplotypes with HD in distinct populations. Expanded HD alleles in Europe occur predominantly on haplogroup A (specifically high-risk variants A1/A2), whereas in East Asian populations, HD alleles are associated with haplogroup C. Whether specific HTT haplotypes associate with HD in black Africans and how these compare with haplotypes found in European and East Asian populations remains unknown. The current study genotyped the HTT region in unaffected individuals and HD patients from each of the South African subpopulations, and haplotypes were constructed. CAG repeat sizes were determined and phased to haplotype. Results indicate that HD alleles from Caucasian and mixed patients are predominantly associated with haplogroup A, signifying a similar European origin for HD. However, in black patients, HD occurs predominantly on haplogroup B, suggesting several distinct origins of the mutation in South Africa. The absence of high-risk variants (A1/A2) in the black subpopulation may also explain the reported low prevalence of HD. Identification of haplotypes associated with HD-expanded alleles is particularly relevant to the development of population-specific therapeutic targets for selective suppression of the expanded HTT transcript.
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Affiliation(s)
- Fiona K Baine
- 1] Division of Human Genetics, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa [2] Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
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125
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Tomé S, Manley K, Simard JP, Clark GW, Slean MM, Swami M, Shelbourne PF, Tillier ERM, Monckton DG, Messer A, Pearson CE. MSH3 polymorphisms and protein levels affect CAG repeat instability in Huntington's disease mice. PLoS Genet 2013; 9:e1003280. [PMID: 23468640 PMCID: PMC3585117 DOI: 10.1371/journal.pgen.1003280] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 12/12/2012] [Indexed: 01/21/2023] Open
Abstract
Expansions of trinucleotide CAG/CTG repeats in somatic tissues are thought to contribute to ongoing disease progression through an affected individual's life with Huntington's disease or myotonic dystrophy. Broad ranges of repeat instability arise between individuals with expanded repeats, suggesting the existence of modifiers of repeat instability. Mice with expanded CAG/CTG repeats show variable levels of instability depending upon mouse strain. However, to date the genetic modifiers underlying these differences have not been identified. We show that in liver and striatum the R6/1 Huntington's disease (HD) (CAG)∼100 transgene, when present in a congenic C57BL/6J (B6) background, incurred expansion-biased repeat mutations, whereas the repeat was stable in a congenic BALB/cByJ (CBy) background. Reciprocal congenic mice revealed the Msh3 gene as the determinant for the differences in repeat instability. Expansion bias was observed in congenic mice homozygous for the B6 Msh3 gene on a CBy background, while the CAG tract was stabilized in congenics homozygous for the CBy Msh3 gene on a B6 background. The CAG stabilization was as dramatic as genetic deficiency of Msh2. The B6 and CBy Msh3 genes had identical promoters but differed in coding regions and showed strikingly different protein levels. B6 MSH3 variant protein is highly expressed and associated with CAG expansions, while the CBy MSH3 variant protein is expressed at barely detectable levels, associating with CAG stability. The DHFR protein, which is divergently transcribed from a promoter shared by the Msh3 gene, did not show varied levels between mouse strains. Thus, naturally occurring MSH3 protein polymorphisms are modifiers of CAG repeat instability, likely through variable MSH3 protein stability. Since evidence supports that somatic CAG instability is a modifier and predictor of disease, our data are consistent with the hypothesis that variable levels of CAG instability associated with polymorphisms of DNA repair genes may have prognostic implications for various repeat-associated diseases. The genetic instability of repetitive DNA sequences in particular genes can lead to numerous neurodegenerative, neurological, and neuromuscular diseases. These diseases show progressively increasing severity of symptoms through the life of the affected individual, a phenomenon that is linked with increasing instability of the repeated sequences as the person ages. There is variability in the levels of this instability between individuals—the source of this variability is unknown. We have shown in a mouse model of repeat instability that small differences in a certain DNA repair gene, MSH3, whose protein is known to fix broken DNA, can lead to variable levels of repeat instability. These DNA repair variants lead to different repair protein levels, where lower levels lead to reduced repeat instability. Our findings reveal that such naturally occurring variations in DNA repair genes in affected humans may serve as a predictor of disease progression. Moreover, our findings support the concept that pharmacological reduction of MSH3 protein should reduce repeat instability and disease progression.
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Affiliation(s)
- Stéphanie Tomé
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Kevin Manley
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, University at Albany, SUNY, Albany, New York, United States of America
| | - Jodie P. Simard
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Greg W. Clark
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - Meghan M. Slean
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Meera Swami
- Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Peggy F. Shelbourne
- Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Elisabeth R. M. Tillier
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - Darren G. Monckton
- Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Anne Messer
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, University at Albany, SUNY, Albany, New York, United States of America
| | - Christopher E. Pearson
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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126
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Nielsen TT, Mizielinska S, Hasholt L, Isaacs AM, Nielsen JE. Reversal of pathology in CHMP2B-mediated frontotemporal dementia patient cells using RNA interference. J Gene Med 2013; 14:521-9. [PMID: 22786763 DOI: 10.1002/jgm.2649] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Frontotemporal dementia is the second most common form of young-onset dementia after Alzheimer's disease, and several genetic forms of frontotemporal dementia are known. A rare genetic variant is caused by a point mutation in the CHMP2B gene. CHMP2B is a component of the ESCRT-III complex, which is involved in endosomal trafficking of proteins targeted for degradation in lysosomes. Mutations in CHMP2B result in abnormal endosomal structures in patient fibroblasts and patient brains, probably through a gain-of-function mechanism, suggesting that the endosomal pathway plays a central role in the pathogenesis of the disease. METHODS In the present study, we used lentiviral vectors to efficiently knockdown CHMP2B by delivering microRNA embedded small hairpin RNAs. RESULTS We show that CHMP2B can be efficiently knocked down in patient fibroblasts using an RNA interference approach and that the knockdown causes reversal of the abnormal endosomal phenotype observed in patient fibroblasts. CONCLUSIONS This is the first description of a treatment that reverses the cellular pathology caused by mutant CHMP2B and suggests that RNA interference might be a feasible therapeutic strategy. Furthermore, it provides the first proof of a direct link between the disease-causing mutation and the cellular phenotype in cells originating from CHMP2B mutation patients.
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Affiliation(s)
- Troels Tolstrup Nielsen
- Danish Dementia Research Centre, Department of Neurology, Rigshospitalet, Copenhagen University Hospital, Denmark.
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127
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Kaplan A, Stockwell BR. Therapeutic approaches to preventing cell death in Huntington disease. Prog Neurobiol 2012; 99:262-80. [PMID: 22967354 PMCID: PMC3505265 DOI: 10.1016/j.pneurobio.2012.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 07/20/2012] [Accepted: 08/17/2012] [Indexed: 12/01/2022]
Abstract
Neurodegenerative diseases affect the lives of millions of patients and their families. Due to the complexity of these diseases and our limited understanding of their pathogenesis, the design of therapeutic agents that can effectively treat these diseases has been challenging. Huntington disease (HD) is one of several neurological disorders with few therapeutic options. HD, like numerous other neurodegenerative diseases, involves extensive neuronal cell loss. One potential strategy to combat HD and other neurodegenerative disorders is to intervene in the execution of neuronal cell death. Inhibiting neuronal cell death pathways may slow the development of neurodegeneration. However, discovering small molecule inhibitors of neuronal cell death remains a significant challenge. Here, we review candidate therapeutic targets controlling cell death mechanisms that have been the focus of research in HD, as well as an emerging strategy that has been applied to developing small molecule inhibitors-fragment-based drug discovery (FBDD). FBDD has been successfully used in both industry and academia to identify selective and potent small molecule inhibitors, with a focus on challenging proteins that are not amenable to traditional high-throughput screening approaches. FBDD has been used to generate potent leads, pre-clinical candidates, and has led to the development of an FDA approved drug. This approach can be valuable for identifying modulators of cell-death-regulating proteins; such compounds may prove to be the key to halting the progression of HD and other neurodegenerative disorders.
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Affiliation(s)
- Anna Kaplan
- Department of Biological Sciences, Columbia University, Northwest Corner Building, MC4846, 550 West 120 Street, New York, NY 10027, USA
| | - Brent R. Stockwell
- Howard Hughes Medical Institute, Columbia University, Northwest Corner Building, MC4846, 550 West 120 Street, New York, NY 10027, USA
- Department of Chemistry, Columbia University, Northwest Corner Building, MC4846, 550 West 120 Street, New York, NY 10027, USA
- Department of Biological Sciences, Columbia University, Northwest Corner Building, MC4846, 550 West 120 Street, New York, NY 10027, USA
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128
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Southwell AL, Skotte NH, Bennett CF, Hayden MR. Antisense oligonucleotide therapeutics for inherited neurodegenerative diseases. Trends Mol Med 2012; 18:634-43. [PMID: 23026741 DOI: 10.1016/j.molmed.2012.09.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 08/25/2012] [Accepted: 09/07/2012] [Indexed: 12/12/2022]
Abstract
The rising median age of our population and the age-dependent risk of neurodegeneration translate to exponentially increasing numbers of afflicted individuals in the coming years. Although symptomatic treatments are available for some neurodegenerative diseases, most are only moderately efficacious and are often associated with significant side effects. The development of small molecule, disease-modifying drugs has been hindered by complex pathogenesis and a failure to clearly define the rate-limiting steps in disease progression. An alternative approach is to directly target the mutant gene product or a defined causative protein. Antisense oligonucleotides (ASOs) - with their diverse functionality, high target specificity, and relative ease of central nervous system (CNS) delivery - are uniquely positioned as potential therapies for neurological diseases. Here we review the development of ASOs for the treatment of inherited neurodegenerative diseases.
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Affiliation(s)
- Amber L Southwell
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, V5Z 4H4, Canada.
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129
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Squitieri F, Jankovic J. Huntington's disease: how intermediate are intermediate repeat lengths? Mov Disord 2012; 27:1714-7. [PMID: 23008174 DOI: 10.1002/mds.25172] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 07/31/2012] [Accepted: 08/03/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Huntington's disease (HD) is a devastating heredoneurodegenerative disorder associated with a wide variety of neurological and psychiatric symptoms caused by an expanded CAG repeat in the HTT gene. The expansion mutation in HTT is dominantly transmitted and codes for a protein named huntingtin (htt). HYPOTHESIS One hypothesis, according to a multistep mechanism, is that the intergenerational transmission of the normal repeat size causes small, progressive CAG stretch elongations in the general population from one generation to another, until a critical pathological CAG repeat threshold is reached. Mutations may originate in the offspring from paternally transmitted CAG repeats, falling within an intermediate alleles (IA) range of 27 to 35 in repeat length. CONCLUSIONS There has been emerging evidence that some individuals with IAs might develop an HD phenotype. This presents a challenge for genetic counseling, because these individuals are often reassured that they are "disease free." However, there are many unanswered questions related to the role of IAs in the development of the HD phenotype and in the pathogenesis of HD.
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130
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Southwell AL, Warby SC, Carroll JB, Doty CN, Skotte NH, Zhang W, Villanueva EB, Kovalik V, Xie Y, Pouladi MA, Collins JA, Yang XW, Franciosi S, Hayden MR. A fully humanized transgenic mouse model of Huntington disease. Hum Mol Genet 2012; 22:18-34. [PMID: 23001568 DOI: 10.1093/hmg/dds397] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Silencing the mutant huntingtin gene (muHTT) is a direct and simple therapeutic strategy for the treatment of Huntington disease (HD) in principle. However, targeting the HD mutation presents challenges because it is an expansion of a common genetic element (a CAG tract) that is found throughout the genome. Moreover, the HTT protein is important for neuronal health throughout life, and silencing strategies that also reduce the wild-type HTT allele may not be well tolerated during the long-term treatment of HD. Several HTT silencing strategies are in development that target genetic sites in HTT that are outside of the CAG expansion, including HD mutation-linked single-nucleotide polymorphisms and the HTT promoter. Preclinical testing of these genetic therapies has required the development of a new mouse model of HD that carries these human-specific genetic targets. To generate a fully humanized mouse model of HD, we have cross-bred BACHD and YAC18 on the Hdh(-/-) background. The resulting line, Hu97/18, is the first murine model of HD that fully genetically recapitulates human HD having two human HTT genes, no mouse Hdh genes and heterozygosity of the HD mutation. We find that Hu97/18 mice display many of the behavioral changes associated with HD including motor, psychiatric and cognitive deficits, as well as canonical neuropathological abnormalities. This mouse line will be useful for gaining additional insights into the disease mechanisms of HD as well as for testing genetic therapies targeting human HTT.
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Affiliation(s)
- Amber L Southwell
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada V5Z 4H4
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131
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Yu D, Pendergraff H, Liu J, Kordasiewicz HB, Cleveland DW, Swayze EE, Lima WF, Crooke ST, Prakash TP, Corey DR. Single-stranded RNAs use RNAi to potently and allele-selectively inhibit mutant huntingtin expression. Cell 2012; 150:895-908. [PMID: 22939619 PMCID: PMC3444165 DOI: 10.1016/j.cell.2012.08.002] [Citation(s) in RCA: 218] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 05/31/2012] [Accepted: 08/01/2012] [Indexed: 01/23/2023]
Abstract
Mutant huntingtin (HTT) protein causes Huntington disease (HD), an incurable neurological disorder. Silencing mutant HTT using nucleic acids would eliminate the root cause of HD. Developing nucleic acid drugs is challenging, and an ideal clinical approach to gene silencing would combine the simplicity of single-stranded antisense oligonucleotides with the efficiency of RNAi. Here, we describe RNAi by single-stranded siRNAs (ss-siRNAs). ss-siRNAs are potent (>100-fold more than unmodified RNA) and allele-selective (>30-fold) inhibitors of mutant HTT expression in cells derived from HD patients. Strategic placement of mismatched bases mimics micro-RNA recognition and optimizes discrimination between mutant and wild-type alleles. ss-siRNAs require Argonaute protein and function through the RNAi pathway. Intraventricular infusion of ss-siRNA produced selective silencing of the mutant HTT allele throughout the brain in a mouse HD model. These data demonstrate that chemically modified ss-siRNAs function through the RNAi pathway and provide allele-selective compounds for clinical development.
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Affiliation(s)
- Dongbo Yu
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center, 6001 Forest Park Road, Dallas, Texas, USA, 75390-9041
| | - Hannah Pendergraff
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center, 6001 Forest Park Road, Dallas, Texas, USA, 75390-9041
| | - Jing Liu
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center, 6001 Forest Park Road, Dallas, Texas, USA, 75390-9041
| | - Holly B. Kordasiewicz
- Department of Cellular and Molecular Medicine, Univ. of California, San Diego 9500 Gilman Drive, La Jolla, CA 92093-0670
- Isis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, California, USA, 92010
| | - Don W. Cleveland
- Department of Cellular and Molecular Medicine, Univ. of California, San Diego 9500 Gilman Drive, La Jolla, CA 92093-0670
| | - Eric E. Swayze
- Isis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, California, USA, 92010
| | - Walt F. Lima
- Isis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, California, USA, 92010
| | - Stanley T. Crooke
- Isis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, California, USA, 92010
| | - Thazha P. Prakash
- Isis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, California, USA, 92010
| | - David R. Corey
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center, 6001 Forest Park Road, Dallas, Texas, USA, 75390-9041
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132
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Pringsheim T, Wiltshire K, Day L, Dykeman J, Steeves T, Jette N. The incidence and prevalence of Huntington's disease: a systematic review and meta-analysis. Mov Disord 2012; 27:1083-91. [PMID: 22692795 DOI: 10.1002/mds.25075] [Citation(s) in RCA: 344] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 04/20/2012] [Accepted: 05/09/2012] [Indexed: 01/21/2023] Open
Abstract
Huntington's disease (HD) is a rare, neurodegenerative disorder characterized by chorea, behavioral manifestations, and dementia. The aim of this study was to estimate the incidence and prevalence of HD through a systematic review of the literature. Medline and Embase databases were searched using terms specific to HD as well as studies of incidence, prevalence, and epidemiology. All studies reporting the incidence and/or prevalence of HD were included. Twenty original research articles were included. Eight studies examined incidence, and 17 studies examined prevalence. Meta-analysis of data from four incidence studies revealed an incidence of 0.38 per 100,000 per year (95% confidence interval [CI]: 0.16, 0.94). Lower incidence was reported in the Asian studies (n = 2), compared to the studies performed in Europe, North America, and Australia (n = 6). The worldwide service-based prevalence of HD, based on a meta-analysis (n = 13 studies), was 2.71 per 100,000 (95% CI: 1.55-4.72). Eleven studies were conducted in Europe, North American, and Australia, with an overall prevalence of 5.70 per 100,000 (95% CI: 4.42-7.35). Three studies were conducted in Asia, with an overall prevalence of 0.40 per 100,000 (95% CI: 0.26-0.61). Metaregression revealed a significantly lower prevalence of HD in Asia, compared to European, North American, and Australian populations. HD is a devastating neurodegenerative disorder with a higher prevalence in Europe, North America, and Australia than in Asia. The difference in prevalence of this genetic disorder can be largely explained by huntingtin gene haplotypes.
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Affiliation(s)
- Tamara Pringsheim
- Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
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133
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Pellegrini M, Renda ME, Vecchio A. Tandem repeats discovery service (TReaDS) applied to finding novel cis-acting factors in repeat expansion diseases. BMC Bioinformatics 2012; 13 Suppl 4:S3. [PMID: 22536970 PMCID: PMC3303744 DOI: 10.1186/1471-2105-13-s4-s3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Background Tandem repeats are multiple duplications of substrings in the DNA that occur contiguously, or at a short distance, and may involve some mutations (such as substitutions, insertions, and deletions). Tandem repeats have been extensively studied also for their association with the class of repeat expansion diseases (mostly affecting the nervous system). Comparative studies on the output of different tools for finding tandem repeats highlighted significant differences among the sets of detected tandem repeats, while many authors pointed up how critical it is the right choice of parameters. Results In this paper we present TReaDS - Tandem Repeats Discovery Service, a tandem repeat meta search engine. TReaDS forwards user requests to several state of the art tools for finding tandem repeats and merges their outcome into a single report, providing a global, synthetic, and comparative view of the results. In particular, TReaDS allows the user to (i) simultaneously run different algorithms on the same data set, (ii) choose for each algorithm a different setting of parameters, and (iii) obtain a report that can be downloaded for further, off-line, investigations. We used TReaDS to investigate sequences associated with repeat expansion diseases. Conclusions By using the tool TReaDS we discover that, for 27 repeat expansion diseases out of a currently known set of 29, long fuzzy tandem repeats are covering the expansion loci. Tests with control sets confirm the specificity of this association. This finding suggests that long fuzzy tandem repeats can be a new class of cis-acting elements involved in the mechanisms leading to the expansion instability. We strongly believe that biologists can be interested in a tool that, not only gives them the possibility of using multiple search algorithm at the same time, with the same effort exerted in using just one of the systems, but also simplifies the burden of comparing and merging the results, thus expanding our capabilities in detecting important phenomena related to tandem repeats.
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Affiliation(s)
- Marco Pellegrini
- Istituto di Informatica e Telematica, Consiglio Nazionale delle Ricerche, Pisa I-56124, Italy
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134
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Lee JM, Gillis T, Mysore J, Ramos E, Myers R, Hayden M, Morrison P, Nance M, Ross C, Margolis R, Squitieri F, Griguoli A, Di Donato S, Gomez-Tortosa E, Ayuso C, Suchowersky O, Trent R, McCusker E, Novelletto A, Frontali M, Jones R, Ashizawa T, Frank S, Saint-Hilaire MH, Hersch S, Rosas H, Lucente D, Harrison M, Zanko A, Abramson R, Marder K, Sequeiros J, MacDonald M, Gusella J. Common SNP-based haplotype analysis of the 4p16.3 Huntington disease gene region. Am J Hum Genet 2012; 90:434-44. [PMID: 22387017 DOI: 10.1016/j.ajhg.2012.01.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 12/24/2011] [Accepted: 01/09/2012] [Indexed: 02/08/2023] Open
Abstract
Age at the onset of motor symptoms in Huntington disease (HD) is determined largely by the length of a CAG repeat expansion in HTT but is also influenced by other genetic factors. We tested whether common genetic variation near the mutation site is associated with differences in the distribution of expanded CAG alleles or age at the onset of motor symptoms. To define disease-associated single-nucleotide polymorphisms (SNPs), we compared 4p16.3 SNPs in HD subjects with population controls in a case:control strategy, which revealed that the strongest signals occurred at a great distance from the HD mutation as a result of "synthetic association" with SNP alleles that are of low frequency in population controls. Detailed analysis delineated a prominent ancestral haplotype that accounted for ∼50% of HD chromosomes and extended to at least 938 kb on about half of these. Together, the seven most abundant haplotypes accounted for ∼83% of HD chromosomes. Neither the extended shared haplotype nor the individual local HTT haplotypes were associated with altered CAG-repeat length distribution or residual age at the onset of motor symptoms, arguing against modification of these disease features by common cis-regulatory elements. Similarly, the 11 most frequent control haplotypes showed no trans-modifier effect on age at the onset of motor symptoms. Our results argue against common local regulatory variation as a factor influencing HD pathogenesis, suggesting that genetic modifiers be sought elsewhere in the genome. They also indicate that genome-wide association analysis with a small number of cases can be effective for regional localization of genetic defects, even when a founder effect accounts for only a fraction of the disorder.
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135
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Fiszer A, Olejniczak M, Switonski PM, Wroblewska JP, Wisniewska-Kruk J, Mykowska A, Krzyzosiak WJ. An evaluation of oligonucleotide-based therapeutic strategies for polyQ diseases. BMC Mol Biol 2012; 13:6. [PMID: 22397573 PMCID: PMC3359213 DOI: 10.1186/1471-2199-13-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Accepted: 03/07/2012] [Indexed: 01/16/2023] Open
Abstract
Background RNA interference (RNAi) and antisense strategies provide experimental therapeutic agents for numerous diseases, including polyglutamine (polyQ) disorders caused by CAG repeat expansion. We compared the potential of different oligonucleotide-based strategies for silencing the genes responsible for several polyQ diseases, including Huntington's disease and two spinocerebellar ataxias, type 1 and type 3. The strategies included nonallele-selective gene silencing, gene replacement, allele-selective SNP targeting and CAG repeat targeting. Results Using the patient-derived cell culture models of polyQ diseases, we tested various siRNAs, and antisense reagents and assessed their silencing efficiency and allele selectivity. We showed considerable allele discrimination by several SNP targeting siRNAs based on a weak G-G or G-U pairing with normal allele and strong G-C pairing with mutant allele at the site of RISC-induced cleavage. Among the CAG repeat targeting reagents the strongest allele discrimination is achieved by miRNA-like functioning reagents that bind to their targets and inhibit their translation without substantial target cleavage. Also, morpholino analog performs well in mutant and normal allele discrimination but its efficient delivery to cells at low effective concentration still remains a challenge. Conclusions Using three cellular models of polyQ diseases and the same experimental setup we directly compared the performance of different oligonucleotide-based treatment strategies that are currently under development. Based on the results obtained by us and others we discussed the advantages and drawbacks of these strategies considering them from several different perspectives. The strategy aimed at nonallele-selective inhibiting of causative gene expression by targeting specific sequence of the implicated gene is the easiest to implement but relevant benefits are still uncertain. The gene replacement strategy that combines the nonallele-selective gene silencing with the expression of the exogenous normal allele is a logical extension of the former and it deserves to be explored further. Both allele-selective RNAi approaches challenge cellular RNA interference machinery to show its ability to discriminate between similar sequences differing in either single base substitutions or repeated sequence length. Although both approaches perform well in allele discrimination most of our efforts are focused on repeat targeting due to its potentially higher universality.
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Affiliation(s)
- Agnieszka Fiszer
- Laboratory of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
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136
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Zhang Y, Friedlander RM. Using non-coding small RNAs to develop therapies for Huntington's disease. Gene Ther 2012; 18:1139-49. [PMID: 22158031 DOI: 10.1038/gt.2011.170] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Huntington's disease (HD) is caused by an expansion of CAG triplets at the 5' end of the HD gene, which encodes a pathologically elongated polyglutamine stretch near the N-terminus of huntingtin. HD is an incurable autosomal-dominant neurodegenerative disease characterized by movement disorder, as well as emotional distress and dementia. The newly discovered roles of the non-coding small RNAs in specific degradation or translational suppression of the targeted mRNAs suggest a potential therapeutic approach of post-transcriptional gene silencing that targets the underlying disease etiology rather than the downstream pathological consequences. From pre-clinical trials in different HD animal models to cells from HD patients, small RNA interference has been applied to 'allele-non-specifically or allele-specifically' silence the mutant HD transgene or endogenous mutant HD allele. Silencing the mutant HD transgene significantly inhibits neurodegeneration, improves motor control, and extends survival of HD mice. With future improvement of mutant allele selectivity (preserving the expression of the neuroprotective wild-type allele), target specificity, efficacy and safety, as well as optimization of delivery methods, small non-coding RNA-based therapeutic applications will be a promising approach to treat HD.
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Affiliation(s)
- Y Zhang
- Department of Neurological Surgery, UPMC Presbyterian Hospital, University of Pittsburgh Medical Center, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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137
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Nopoulos P, Epping EA, Wassink T, Schlaggar BL, Perlmutter J. Correlation of CAG repeat length between the maternal and paternal allele of the Huntingtin gene: evidence for assortative mating. Behav Brain Funct 2011; 7:45. [PMID: 22008211 PMCID: PMC3219594 DOI: 10.1186/1744-9081-7-45] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 10/18/2011] [Indexed: 11/10/2022] Open
Abstract
Triplet repeats contribute to normal variation in behavioral traits and when expanded, cause brain disorders. While Huntington's Disease is known to be caused by a CAG triplet repeat in the gene Huntingtin, the effect of CAG repeats on brain function below disease threshold has not been studied. The current study shows a significant correlation between the CAG repeat length of the maternal and paternal allele in the Huntingtin gene among healthy subjects, suggesting assortative mating.
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Affiliation(s)
- Peg Nopoulos
- Department of Psychiatry, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
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138
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Carroll JB, Warby SC, Southwell AL, Doty CN, Greenlee S, Skotte N, Hung G, Bennett CF, Freier SM, Hayden MR. Potent and selective antisense oligonucleotides targeting single-nucleotide polymorphisms in the Huntington disease gene / allele-specific silencing of mutant huntingtin. Mol Ther 2011; 19:2178-85. [PMID: 21971427 DOI: 10.1038/mt.2011.201] [Citation(s) in RCA: 211] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Huntington disease (HD) is an autosomal dominant neurodegenerative disorder caused by CAG-expansion in the huntingtin gene (HTT) that results in a toxic gain of function in the mutant huntingtin protein (mHTT). Reducing the expression of mHTT is therefore an attractive therapy for HD. However, wild-type HTT protein is essential for development and has critical roles in maintaining neuronal health. Therapies for HD that reduce wild-type HTT may therefore generate unintended negative consequences. We have identified single-nucleotide polymorphism (SNP) targets in the human HD population for the disease-specific targeting of the HTT gene. Using primary cells from patients with HD and the transgenic YAC18 and BACHD mouse lines, we developed antisense oligonucleotide (ASO) molecules that potently and selectively silence mHTT at both exonic and intronic SNP sites. Modification of these ASOs with S-constrained-ethyl (cET) motifs significantly improves potency while maintaining allele selectively in vitro. The developed ASO is potent and selective for mHTT in vivo after delivery to the mouse brain. We demonstrate that potent and selective allele-specific knockdown of the mHTT protein can be achieved at therapeutically relevant SNP sites using ASOs in vitro and in vivo.
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Affiliation(s)
- Jeffrey B Carroll
- Program in Neuroscience, Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
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139
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Abstract
RNA interference (RNAi) is a powerful approach for reducing expression of endogenously expressed proteins. It is widely used for biological applications and is being harnessed to silence mRNAs encoding pathogenic proteins for therapy. Various methods - including delivering RNA oligonucleotides and expressing RNAi triggers from viral vectors - have been developed for successful RNAi in cell culture and in vivo. Recently, RNAi-based gene silencing approaches have been demonstrated in humans, and ongoing clinical trials hold promise for treating fatal disorders or providing alternatives to traditional small molecule therapies. Here we describe the broad range of approaches to achieve targeted gene silencing for therapy, discuss important considerations when developing RNAi triggers for use in humans, and review the current status of clinical trials.
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Affiliation(s)
- Beverly L Davidson
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
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140
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Cheng TM, Lee TC, Tseng SH, Chu HL, Pan JP, Chang CC. Human haptoglobin phenotypes and concentration determination by nanogold-enhanced electrochemical impedance spectroscopy. NANOTECHNOLOGY 2011; 22:245105. [PMID: 21543834 DOI: 10.1088/0957-4484/22/24/245105] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Haptoglobin (Hp) is an acute phase protein that binds free hemoglobin (Hb), preventing Hb-induced oxidative damage in the vascular system. There are three phenotypes in human Hp, whose heterogeneous polymorphic structures and varying concentrations in plasma have been attributed to the cause of diseases and outcome of clinical treatments. Different phenotypes of Hp may be composed of the same subunits but different copy numbers, rendering their determination difficult by a single procedure. In this study, we have developed a simple, fast, reliable and sensitive method, using label-free nanogold-modified bioprobes coupled with self-development electrochemical impedance spectroscopy (EIS). By this method, probe surface charge transfer resistance is detected. The relative charge transfer resistance ratios for Hp 1-1, Hp 2-1 and Hp 2-2 were characterized. We were able to determine protein size difference within 3 nm, and the linear region of the calibration curve for Hp levels in the range of 90 pg ml(-1) and 90 µg ml(-1) (∼1 fM to 1 pM). We surmise that similar approaches can be used to investigate protein polymorphism and altered protein-protein interaction associated with diseases.
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Affiliation(s)
- Tsai-Mu Cheng
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan, Republic of China
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141
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Sierant M, Paduszynska A, Kazmierczak-Baranska J, Nacmias B, Sorbi S, Bagnoli S, Sochacka E, Nawrot B. Specific Silencing of L392V PSEN1 Mutant Allele by RNA Interference. Int J Alzheimers Dis 2011; 2011:809218. [PMID: 21559198 PMCID: PMC3090069 DOI: 10.4061/2011/809218] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2010] [Accepted: 02/07/2011] [Indexed: 01/07/2023] Open
Abstract
RNA interference (RNAi) technology provides a powerful molecular tool to reduce an expression of selected genes in eukaryotic cells. Short interfering RNAs (siRNAs) are the effector molecules that trigger RNAi. Here, we describe siRNAs that discriminate between the wild type and mutant (1174 C→G) alleles of human Presenilin1 gene (PSEN1). This mutation, resulting in L392V PSEN1 variant, contributes to early onset familial Alzheimer's disease. Using the dual fluorescence assay, flow cytometry and fluorescent microscopy we identified positions 8th–11th, within the central part of the antisense strand, as the most sensitive to mismatches. 2-Thiouridine chemical modification introduced at the 3′-end of the antisense strand improved the allele discrimination, but wobble base pairing adjacent to the mutation site abolished the siRNA activity. Our data indicate that siRNAs can be designed to discriminate between the wild type and mutant alleles of genes that differ by just a single nucleotide.
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Affiliation(s)
- Malgorzata Sierant
- Department of Bioorganic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, 90-363 Lodz, Sienkiewicza 112, Poland
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142
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Fiszer A, Mykowska A, Krzyzosiak WJ. Inhibition of mutant huntingtin expression by RNA duplex targeting expanded CAG repeats. Nucleic Acids Res 2011; 39:5578-85. [PMID: 21427085 PMCID: PMC3141264 DOI: 10.1093/nar/gkr156] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The specific silencing of the gene of interest is the major objective of RNA interference technology; therefore, unique sequences but not abundant sequence repeats are targeted by silencing reagents. Here, we describe the targeting of expanded CAG repeats that occur in transcripts derived from the mutant allele of the gene implicated in Huntington’s disease (HD) in the presence of the normal allele and other human mRNAs containing CAG and CUG repeat tracts. We show that a high degree of silencing selectivity may be achieved between the repeated sequences. We demonstrate preferential suppression of the mutant huntingtin allele and concomitant activation of the normal huntingtin allele in cell lines derived from HD patients that were transfected with short RNA duplexes composed of CAG and CUG repeats containing mutations at specific positions. These effects may lead to promising therapeutic modalities for HD, a condition for which no therapy presently exists.
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Affiliation(s)
- Agnieszka Fiszer
- Laboratory of Cancer Genetics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704, Poznan, Poland
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143
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López-Sendón JL, Royuela A, Trigo P, Orth M, Lange H, Reilmann R, Keylock J, Rickards H, Piacentini S, Squitieri F, Landwehrmeyer B, Witjes-Ane MN, Jurgens CK, Roos RAC, Abraira V, de Yébenes JG. What is the impact of education on Huntington's disease? Mov Disord 2011; 26:1489-95. [PMID: 21432905 DOI: 10.1002/mds.23385] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 05/18/2010] [Accepted: 07/09/2010] [Indexed: 11/05/2022] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disease caused by a cytosine adenosine guanine (CAG) expansion in the huntingtin gene. The length of the triplet repeat is the most important factor in determining age of onset and the severity of the disease, but substantial variability of these parameters is attributed to other factors. To investigate the relationship between the years of education and the age at onset and the severity of the phenotype in patients with HD, we applied multiple linear regression analysis to examine the impact of education on the age at onset and the severity of the clinical scores assessed by the Unified Huntington's Disease Rating Scale (UHDRS) of 891 patients with HD from the multinational observational study "Registry" conducted by the European Huntintgton's Disease Network. The model was adjusted for CAG repeat length and age at the time of assessment. Patients with lengthier education exhibited earlier estimated age at onset but less severe clinical scores (motor = -3.6, P = 0.006; cognitive = 27.0, P < 0.001; behavioral = -3.0, P < 0.001; and functional capacity = 1.1 points, P < 0.001) than those with shorter education, after controlling for age and number of CAG repeats. These differences persisted throughout all quartiles of disease severity. An earlier recognition of symptoms and manifestations among the more educated patients could explain the earlier estimated age at onset in this group. The link between better clinical UHDRS scores and higher education might reflect a beneficial effect of education or its covariates on the course of HD.
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Ma M, Yang Y, Shang H, Su D, Zhang H, Ma Y, Liu Y, Tao D, Zhang S. Evidence for a predisposing background for CAG expansion leading to HTT mutation in a Chinese population. J Neurol Sci 2011; 298:57-60. [PMID: 20864123 DOI: 10.1016/j.jns.2010.08.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 08/17/2010] [Accepted: 08/23/2010] [Indexed: 02/05/2023]
Abstract
OBJECTIVE To investigate the predisposing background for the instability of CAG expansions of the HTT gene in a Chinese population. METHODS Genotyping and haplotyping of CAG and CCG repeats of the HTT gene were carried out in 32 unrelated HD patients and 95 non-HD control individuals of Han origin, using capillary electrophoresis and DNA sequencing. The frequencies of different CCG repeats were compared between mutant and wild-type HTT genes. In controls, the comparison of the mean CAG repeat size was performed among different CCG repeats. RESULTS A total of five alleles of CCG repeats were distinguished, in which four were present in HD chromosomes. In the CCG alleles, (CCG)10 showed a higher frequency in mutant HTT genes relative to wild-type ones, and the highest mean CAG repeat size was observed in the (CCG)10 background. Additionally, a haplotype of (CAG)32-(CCG)10 was found in the control group. CONCLUSION Our findings indicate that HTT mutation is likely of multiple origins in the Chinese population. Among the origins, more new HTT mutations may arise from the (CCG)10 than from other CCG alleles, which suggests that the (CCG)10 allele may represent a predisposing background for CAG expansion in Chinese populations. Therefore, in comparison with Europeans, the significantly lower prevalence of Huntington's disease in Chinese individuals may not be due to the absence of the predisposing background for CAG expansion but instead may partly result from the lower frequency of the predisposing haplotype for CAG instability in the population.
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Affiliation(s)
- Mingyi Ma
- Department of Medical Genetics, West China Hospital and State Key Laboratory of Biotherapy, Sichuan University, Gaopeng street, Keyuan Road 4, Chengdu, Sichuan 610041, China
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HTT haplotypes contribute to differences in Huntington disease prevalence between Europe and East Asia. Eur J Hum Genet 2011; 19:561-6. [PMID: 21248742 DOI: 10.1038/ejhg.2010.229] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Huntington disease (HD) results from CAG expansion in the huntingtin (HTT) gene. Although HD occurs worldwide, there are large geographic differences in its prevalence. The prevalence in populations derived from Europe is 10-100 times greater than in East Asia. The European general population chromosomes can be grouped into three major haplogroups (group of similar haplotypes): A, B and C. The majority of HD chromosomes in Europe are found on haplogroup A. However, in the East-Asian populations of China and Japan, we find the majority of HD chromosomes are associated with haplogroup C. The highest risk HD haplotypes (A1 and A2), are absent from the general and HD populations of China and Japan, and therefore provide an explanation for why HD prevalence is low in East Asia. Interestingly, both East-Asian and European populations share a similar low level of HD on haplogroup C. Our data are consistent with the hypothesis that different HTT haplotypes have different mutation rates, and geographic differences in HTT haplotypes explain the difference in HD prevalence. Further, the bias for expansion on haplogroup C in the East-Asian population cannot be explained by a higher average CAG size, as haplogroup C has a lower average CAG size in the general East-Asian population compared with other haplogroups. This finding suggests that CAG-tract size is not the only factor important for CAG instability. Instead, the expansion bias may be because of genetic cis-elements within the haplotype that influence CAG instability in HTT, possibly through different mutational mechanisms for the different haplogroups.
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Reiner A, Dragatsis I, Dietrich P. Genetics and neuropathology of Huntington's disease. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2011; 98:325-72. [PMID: 21907094 PMCID: PMC4458347 DOI: 10.1016/b978-0-12-381328-2.00014-6] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Huntington's disease (HD) is an autosomal dominant progressive neurodegenerative disorder that prominently affects the basal ganglia, leading to affective, cognitive, behavioral and motor decline. The basis of HD is a CAG repeat expansion to >35 CAG in a gene that codes for a ubiquitous protein known as huntingtin, resulting in an expanded N-terminal polyglutamine tract. The size of the expansion is correlated with disease severity, with increasing CAG accelerating the age of onset. A variety of possibilities have been proposed as to the mechanism by which the mutation causes preferential injury to the basal ganglia. The present chapter provides a basic overview of the genetics and pathology of HD.
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Affiliation(s)
- Anton Reiner
- Department of Anatomy & Neurobiology, The University of Tennessee Health Science Center, 855 Monroe Ave. Memphis, TN 38163, USA
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Abstract
Huntington disease (HD) is a dominantly inherited neurodegenerative disorder that usually presents in adulthood with characteristic motor and cognitive features and with variable and diverse psychiatric disturbances. Following the discovery of the causative defect in the HTT gene in 1993, great advances in understanding the pathogenesis of HD have been made, yet no effective disease-modifying therapy has been identified. In this new era of HD research, we have seen the emergence of a number of large clinical trials, the systematic search for novel biomarkers and the recent initiation of the first pre-manifest HD clinical studies. In this review, we seek to provide an overview of the clinical and genetic features of HD together with a summary of clinical research at this time.
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Affiliation(s)
- Aaron Sturrock
- Department of Medical Genetics, University of British Columbia (UBC), Vancouver, British Columbia, Canada.
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Abstract
Huntington Disease (HD) is a relatively common inherited neuropathy with characteristic cognitive and behavioral features. HD usually has a late onset and often is not recognized until the third or fourth decades of life. Transmitted as an autosomal dominant trait, HD has become a prototype for understanding a group of neurogenetic disorders. As a class, HD and the others are manifestations of the expansion of a trinucleotide repeat within the gene coding or structural region. In HD expansion of the (CAG)(n) repeat in the first exon from an average of 18 (normal) to a median of 44 is the underlying molecular biologic change. In affected individuals, the mutant HD protein (Huntingtin, mHtt) thus contains an extended polyglutamine repeat. Clinical and neuropathic changes in the caudate and putamen nuclei occur relatively early with other brain regions being affected later. Mitochondrial structure, altered electron transport and increased brain lactate levels have implicated mitochondria in HD pathophysiology. There is also evidence that reduced transcription of the peroxisome proliferator-activated receptor-gamma coactivator (PGC-1 alpha) leads to altered downstream gene regulation. Further evidence for mitochondrial involvement is presented in the following reviews. Clarifying mitochondrial derangements has led to some possibilities for therapeutic intervention.
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Sequeiros J, Ramos EM, Cerqueira J, Costa MC, Sousa A, Pinto-Basto J, Alonso I. Large normal and reduced penetrance alleles in Huntington disease: instability in families and frequency at the laboratory, at the clinic and in the population. Clin Genet 2010; 78:381-7. [DOI: 10.1111/j.1399-0004.2010.01388.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Johnson CD, Davidson BL. Huntington's disease: progress toward effective disease-modifying treatments and a cure. Hum Mol Genet 2010; 19:R98-R102. [PMID: 20421366 DOI: 10.1093/hmg/ddq148] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Huntington's disease (HD) is caused by a dominant mutation in HTT, the HD gene. This discovery opens possibilities for treatment based on silencing of the disease-causing allele or with compounds that reduce the production of disease-causing mRNA and/or protein. Although additional developments are needed related to the delivery of gene silencing and discovery and development of drugs that reduce disease-causing gene products, these treatments are predicted to be effective since they act by reducing the source of toxicity. The identification of therapies that act by blocking toxicity is conceptually more complicated, as this requires an accurate understanding of the cellular location and the specific molecular dysfunctions that cause the phenotypes of HD, which is not yet available. Though challenges remain, significant progress has been made. Effective disease-modifying treatments will soon be tested and may lead to disease-altering therapies.
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