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Rajan-Babu IS, Dolzhenko E, Eberle MA, Friedman JM. Sequence composition changes in short tandem repeats: heterogeneity, detection, mechanisms and clinical implications. Nat Rev Genet 2024; 25:476-499. [PMID: 38467784 DOI: 10.1038/s41576-024-00696-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2024] [Indexed: 03/13/2024]
Abstract
Short tandem repeats (STRs) are a class of repetitive elements, composed of tandem arrays of 1-6 base pair sequence motifs, that comprise a substantial fraction of the human genome. STR expansions can cause a wide range of neurological and neuromuscular conditions, known as repeat expansion disorders, whose age of onset, severity, penetrance and/or clinical phenotype are influenced by the length of the repeats and their sequence composition. The presence of non-canonical motifs, depending on the type, frequency and position within the repeat tract, can alter clinical outcomes by modifying somatic and intergenerational repeat stability, gene expression and mutant transcript-mediated and/or protein-mediated toxicities. Here, we review the diverse structural conformations of repeat expansions, technological advances for the characterization of changes in sequence composition, their clinical correlations and the impact on disease mechanisms.
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Affiliation(s)
- Indhu-Shree Rajan-Babu
- Department of Medical Genetics, The University of British Columbia, and Children's & Women's Hospital, Vancouver, British Columbia, Canada.
| | | | | | - Jan M Friedman
- Department of Medical Genetics, The University of British Columbia, and Children's & Women's Hospital, Vancouver, British Columbia, Canada
- BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
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2
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Lin Z, Li J, Luo W. A DLB patient with complicated CAA interruptions and intermediate alleles of 43 CAG/CAA repeats in TBP. Acta Neurol Belg 2024; 124:695-697. [PMID: 37632648 DOI: 10.1007/s13760-023-02351-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 07/10/2023] [Indexed: 08/28/2023]
Affiliation(s)
- Zhiru Lin
- Department of Neurology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310009, Zhejiang, China
| | - Jiaxiang Li
- Department of Neurology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310009, Zhejiang, China
| | - Wei Luo
- Department of Neurology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310009, Zhejiang, China.
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3
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Novis LE, Alavi S, Pellerin D, Della Coleta MV, Raskin S, Spitz M, Cortese A, Houlden H, Teive HA. Unraveling the genetic landscape of undiagnosed cerebellar ataxia in Brazilian patients. Parkinsonism Relat Disord 2024; 119:105961. [PMID: 38145611 DOI: 10.1016/j.parkreldis.2023.105961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 12/12/2023] [Accepted: 12/12/2023] [Indexed: 12/27/2023]
Abstract
INTRODUCTION Hereditary ataxias (HAs) encompass a diverse and genetically intricate group of rare neurodegenerative disorders, presenting diagnostic challenges. Whole-exome sequencing (WES) has significantly improved diagnostic success. This study aimed to elucidate genetic causes of cerebellar ataxia within a diverse Brazilian cohort. METHODS Biological samples were collected from individuals with sporadic or familial cerebellar ataxia, spanning various ages and phenotypes, excluding common SCAs and Friedreich ataxia. RFC1 biallelic AAGGG repeat expansion was screened in all patients. For AAGGG-negative cases, WES targeting 441 ataxia-related genes was performed, followed by ExpansionHunter analysis for repeat expansions, including the recently described GGC-ZFHX3. Variant classification adhered to ClinGen guidelines, yielding definitive or probable diagnoses. RESULTS The study involved 76 diverse Brazilian families. 16 % received definitive diagnoses, and another 16 % received probable ones. RFC1-related ataxia was predominant, with two definitive cases, followed by KIF1A (one definitive and one probable) and SYNE-1 (two probable). Early-onset cases exhibited higher diagnostic rates. ExpansionHunter improved diagnosis by 4 %.We did not detected GGC-ZFHX3 repeat expansion in this cohort. CONCLUSION This study highlights diagnostic complexities in cerebellar ataxia, even with advanced genetic methods. RFC1, KIF1A, and SYNE1 emerged as prevalent mutations. ZFHX3 repeat expansion seem to be rare in Brazilian population. Early-onset cases showed higher diagnostic success. WES coupled with ExpansionHunter holds promise as a primary diagnostic tool, emphasizing the need for broader NGS accessibility in Brazil.
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Affiliation(s)
- Luiz Eduardo Novis
- Pós-graduação em Medicina Interna e Ciências da Saúde, Hospital de Clínicas da Universidade Federal do Paraná, Curitiba, PR, Brazil; Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and the National Hospital for Neurology and Neurosurgery, London, UK.
| | - Shahryar Alavi
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and the National Hospital for Neurology and Neurosurgery, London, UK
| | - David Pellerin
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and the National Hospital for Neurology and Neurosurgery, London, UK; Departments of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Canada
| | | | | | - Mariana Spitz
- Departamento de Especialidades Médicas, Serviço de Neurologia, Universidade Estadual do Rio de Janeiro, RJ, Brazil
| | - Andrea Cortese
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and the National Hospital for Neurology and Neurosurgery, London, UK; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Henry Houlden
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and the National Hospital for Neurology and Neurosurgery, London, UK
| | - Helio Afonso Teive
- Pós-graduação em Medicina Interna e Ciências da Saúde, Hospital de Clínicas da Universidade Federal do Paraná, Curitiba, PR, Brazil
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Kumar M, Tyagi N, Faruq M. The molecular mechanisms of spinocerebellar ataxias for DNA repeat expansion in disease. Emerg Top Life Sci 2023; 7:289-312. [PMID: 37668011 DOI: 10.1042/etls20230013] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 08/01/2023] [Accepted: 08/16/2023] [Indexed: 09/06/2023]
Abstract
Spinocerebellar ataxias (SCAs) are a heterogenous group of neurodegenerative disorders which commonly inherited in an autosomal dominant manner. They cause muscle incoordination due to degeneration of the cerebellum and other parts of nervous system. Out of all the characterized (>50) SCAs, 14 SCAs are caused due to microsatellite repeat expansion mutations. Repeat expansions can result in toxic protein gain-of-function, protein loss-of-function, and/or RNA gain-of-function effects. The location and the nature of mutation modulate the underlying disease pathophysiology resulting in varying disease manifestations. Potential toxic effects of these mutations likely affect key major cellular processes such as transcriptional regulation, mitochondrial functioning, ion channel dysfunction and synaptic transmission. Involvement of several common pathways suggests interlinked function of genes implicated in the disease pathogenesis. A better understanding of the shared and distinct molecular pathogenic mechanisms in these diseases is required to develop targeted therapeutic tools and interventions for disease management. The prime focus of this review is to elaborate on how expanded 'CAG' repeats contribute to the common modes of neurotoxicity and their possible therapeutic targets in management of such devastating disorders.
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Affiliation(s)
- Manish Kumar
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi 110007, India
| | - Nishu Tyagi
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi 110007, India
| | - Mohammed Faruq
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi 110007, India
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Rafehi H, Bennett MF, Bahlo M. Detection and discovery of repeat expansions in ataxia enabled by next-generation sequencing: present and future. Emerg Top Life Sci 2023; 7:349-359. [PMID: 37733280 PMCID: PMC10754322 DOI: 10.1042/etls20230018] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 08/29/2023] [Accepted: 09/12/2023] [Indexed: 09/22/2023]
Abstract
Hereditary cerebellar ataxias are a heterogenous group of progressive neurological disorders that are disproportionately caused by repeat expansions (REs) of short tandem repeats (STRs). Genetic diagnosis for RE disorders such as ataxias are difficult as the current gold standard for diagnosis is repeat-primed PCR assays or Southern blots, neither of which are scalable nor readily available for all STR loci. In the last five years, significant advances have been made in our ability to detect STRs and REs in short-read sequencing data, especially whole-genome sequencing. Given the increasing reliance of genomics in diagnosis of rare diseases, the use of established RE detection pipelines for RE disorders is now a highly feasible and practical first-step alternative to molecular testing methods. In addition, many new pathogenic REs have been discovered in recent years by utilising WGS data. Collectively, genomes are an important resource/platform for further advancements in both the discovery and diagnosis of REs that cause ataxia and will lead to much needed improvement in diagnostic rates for patients with hereditary ataxia.
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Affiliation(s)
- Haloom Rafehi
- Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
| | - Mark F Bennett
- Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
- Epilepsy Research Centre, Department of Medicine, University of Melbourne, Austin Health, Heidelberg, VIC, Australia
| | - Melanie Bahlo
- Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
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Patel N, Alam N, Libohova K, Dulay R, Todi SV, Sujkowski A. Phenotypic defects from the expression of wild-type and pathogenic TATA-binding proteins in new Drosophila models of Spinocerebellar Ataxia Type 17. G3 (BETHESDA, MD.) 2023; 13:jkad180. [PMID: 37551423 PMCID: PMC10542169 DOI: 10.1093/g3journal/jkad180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 01/25/2023] [Accepted: 07/19/2023] [Indexed: 08/09/2023]
Abstract
Spinocerebellar Ataxia Type 17 (SCA17) is the most recently identified member of the polyglutamine (polyQ) family of disorders, resulting from abnormal CAG/CAA expansion in the TATA box-binding protein (TBP), an initiation factor essential for of all eukaryotic transcription. A largely autosomal dominant inherited disease, SCA17, is unique in both its heterogeneous clinical presentation and low incidence of genetic anticipation, the phenomenon in which subsequent generations inherit longer polyQ expansions that yield earlier and more severe symptom onset. Like other polyQ disease family members, SCA17 patients experience progressive ataxia and dementia, and treatments are limited to preventing symptoms and increasing quality of life. Here, we report 2 new Drosophila models that express human TBP with polyQ repeats in either wild-type or SCA17 patient range. We find that TBP expression has age- and tissue-specific effects on neurodegeneration, with polyQ-expanded SCA17 protein expression generally having more severe effects. In addition, SCA17 model flies accumulate more aggregation-prone TBP, with a greater proportion localizing to the nucleus. These new lines provide a new resource for the biochemical characterization of SCA17 pathology and the future identification of therapeutic targets.
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Affiliation(s)
- Nikhil Patel
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Nadir Alam
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Kozeta Libohova
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Ryan Dulay
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Sokol V Todi
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
- Department of Neurology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Alyson Sujkowski
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
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Rossi M, Hamed M, Rodríguez-Antigüedad J, Cornejo-Olivas M, Breza M, Lohmann K, Klein C, Rajalingam R, Marras C, van de Warrenburg BP. Genotype-Phenotype Correlations for ATX-TBP (SCA17): MDSGene Systematic Review. Mov Disord 2023; 38:368-377. [PMID: 36374860 DOI: 10.1002/mds.29278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/31/2022] [Accepted: 10/31/2022] [Indexed: 11/16/2022] Open
Abstract
Spinocerebellar ataxia type 17 or ATX-TBP is a CAG/CAA repeat expansion disorder characterized by marked clinical heterogeneity. Reports of affected carriers with subthreshold repeat expansions and of patients with Parkinson's disease (PD) with expanded repeats have cast doubt on the established cutoff values of the expansions and the phenotypic spectrum of this disorder. The objective of this systematic review was to explore the genotype-phenotype relationships for repeat expansions in TBP to delineate the ATX-TBP phenotype and reevaluate the pathological range of repeat expansions. The International Parkinson and Movement Disorder Society Genetic Mutation Database (MDSGene) standardized data extraction protocol was followed. Clinically affected carriers of reported ATX-TBP expansions were included. Publications that contained repeat sizes in screened cohorts of patients with PD and/or healthy individuals were included for a separate evaluation of cutoff values. Phenotypic and genotypic data for 346 ATX-TBP patients were curated. Overall, 97.7% of the patients had ≥41 repeats, while 99.6% of patients with PD and 99.9% of healthy individuals had ≤42 repeats, with a gray zone of reduced penetrance between 41 and 45 repeats. Pure parkinsonism was more common in ATX-TBP patients with 41 to 45 repeats than in the group with ≥46 repeats, which conversely more often presented with a complex phenotype with mixed movement disorders. An updated genotype-phenotype assessment for ATX-TBP is provided, and new repeat expansion cutoff values of reduced penetrance (41-45 expanded repeats) and full penetrance (46-66 expanded repeats) are proposed. These adjusted cutoff values will have diagnostic and counseling implications and may guide future clinical trial protocol. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Malco Rossi
- Sección de Movimientos Anormales, Departamento de Neurología, Fleni, Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Moath Hamed
- New York-Presbyterian Brooklyn Methodist Hospital, Brooklyn, New York, USA
| | - Jon Rodríguez-Antigüedad
- Movement Disorders Unit, Neurology Department, Sant Pau Hospital, Barcelona, Spain
- Institut d'Investigacions Biomediques-Sant Pau, Barcelona, Spain
| | - Mario Cornejo-Olivas
- Neurogenetics Research Center, Instituto Nacional de Ciencias Neurológicas, Lima, Peru
- Carrera de Medicina, Universidad Científica del Sur, Lima, Peru
| | - Marianthi Breza
- 1st Department of Neurology, School of Medicine, Eginition Hospital, National and Kapodistrian University of Athens, Athens, Greece
- Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, The National Hospital for Neurology and Neurosurgery, London, UK
| | - Katja Lohmann
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Christine Klein
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Rajasumi Rajalingam
- Edmond J. Safra Program in Parkinson's Disease, Morton and Gloria Shulman Movement Disorders Clinic, Toronto Western Hospital, UHN, Toronto, Ontario, Canada
| | - Connie Marras
- Edmond J. Safra Program in Parkinson's Disease, Morton and Gloria Shulman Movement Disorders Clinic, Toronto Western Hospital, UHN, Toronto, Ontario, Canada
| | - Bart P van de Warrenburg
- Department of Neurology, Donders Institute for Brain, Cognition & Behaviour, Radboud University Medical Center, Nijmegen, the Netherlands
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Intermediate repeat expansions of TBP and STUB1: Genetic modifier or pure digenic inheritance in spinocerebellar ataxias? Genet Med 2023; 25:100327. [PMID: 36422518 DOI: 10.1016/j.gim.2022.10.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 10/21/2022] [Accepted: 10/23/2022] [Indexed: 11/25/2022] Open
Abstract
PURPOSE CAG/CAA repeat expansions in TBP>49 are responsible for spinocerebellar ataxia (SCA) type 17 (SCA17). We previously detected cosegregation of STUB1 variants causing SCA48 with intermediate alleles of TBP in 2 families. This cosegregation questions the existence of SCA48 as a monogenic disease. METHODS We systematically sequenced TBP repeats in 34 probands of dominant ataxia families with STUB1 variants. In addition, we searched for pathogenic STUB1 variants in probands with expanded alleles of TBP>49 (n = 2) or intermediate alleles of TBP≥40 (n = 47). RESULTS STUB1 variants were found in half of the TBP40-49 cohort. Mirroring this finding, TBP40-49 alleles were detected in 40% of STUB1 probands. The longer the TBP repeat length, the more likely the occurrence of cognitive impairment (P = .0129) and the faster the disease progression until death (P = .0003). Importantly, 13 STUB1 probands presenting with the full SCA48 clinical phenotype had normal TBP37-39 alleles, excluding digenic inheritance as the sole mode. CONCLUSION We show that intermediate TBP40-49 alleles act as disease modifiers of SCA48 rather than a STUB1/TBP digenic model. This distinction from what has been proposed before has crucial consequences for genetic counseling in SCA48.
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Younger DS. Neurogenetic motor disorders. HANDBOOK OF CLINICAL NEUROLOGY 2023; 195:183-250. [PMID: 37562870 DOI: 10.1016/b978-0-323-98818-6.00003-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
Advances in the field of neurogenetics have practical applications in rapid diagnosis on blood and body fluids to extract DNA, obviating the need for invasive investigations. The ability to obtain a presymptomatic diagnosis through genetic screening and biomarkers can be a guide to life-saving disease-modifying therapy or enzyme replacement therapy to compensate for the deficient disease-causing enzyme. The benefits of a comprehensive neurogenetic evaluation extend to family members in whom identification of the causal gene defect ensures carrier detection and at-risk counseling for future generations. This chapter explores the many facets of the neurogenetic evaluation in adult and pediatric motor disorders as a primer for later chapters in this volume and a roadmap for the future applications of genetics in neurology.
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Affiliation(s)
- David S Younger
- Department of Clinical Medicine and Neuroscience, CUNY School of Medicine, New York, NY, United States; Department of Medicine, Section of Internal Medicine and Neurology, White Plains Hospital, White Plains, NY, United States.
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10
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Molecular and Clinical Implications of Variant Repeats in Myotonic Dystrophy Type 1. Int J Mol Sci 2021; 23:ijms23010354. [PMID: 35008780 PMCID: PMC8745394 DOI: 10.3390/ijms23010354] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/14/2021] [Accepted: 12/18/2021] [Indexed: 12/13/2022] Open
Abstract
Myotonic dystrophy type 1 (DM1) is one of the most variable monogenic diseases at phenotypic, genetic, and epigenetic level. The disease is multi-systemic with the age at onset ranging from birth to late age. The underlying mutation is an unstable expansion of CTG repeats in the DMPK gene, varying in size from 50 to >1000 repeats. Generally, large expansions are associated with an earlier age at onset. Additionally, the most severe, congenital DM1 form is typically associated with local DNA methylation. Genetic variability of DM1 mutation is further increased by its structural variations due to presence of other repeats (e.g., CCG, CTC, CAG). These variant repeats or repeat interruptions seem to confer an additional level of epigenetic variability since local DNA methylation is frequently associated with variant CCG repeats independently of the expansion size. The effect of repeat interruptions on DM1 molecular pathogenesis is not investigated enough. Studies on patients indicate their stabilizing effect on DMPK expansions because no congenital cases were described in patients with repeat interruptions, and the age at onset is frequently later than expected. Here, we review the clinical relevance of repeat interruptions in DM1 and genetic and epigenetic characteristics of interrupted DMPK expansions based on patient studies.
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Deshmukh AL, Caron MC, Mohiuddin M, Lanni S, Panigrahi GB, Khan M, Engchuan W, Shum N, Faruqui A, Wang P, Yuen RKC, Nakamori M, Nakatani K, Masson JY, Pearson CE. FAN1 exo- not endo-nuclease pausing on disease-associated slipped-DNA repeats: A mechanism of repeat instability. Cell Rep 2021; 37:110078. [PMID: 34879276 DOI: 10.1016/j.celrep.2021.110078] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/02/2021] [Accepted: 11/09/2021] [Indexed: 12/19/2022] Open
Abstract
Ongoing inchworm-like CAG and CGG repeat expansions in brains, arising by aberrant processing of slipped DNAs, may drive Huntington's disease, fragile X syndrome, and autism. FAN1 nuclease modifies hyper-expansion rates by unknown means. We show that FAN1, through iterative cycles, binds, dimerizes, and cleaves slipped DNAs, yielding striking exo-nuclease pauses along slip-outs: 5'-C↓A↓GC↓A↓G-3' and 5'-C↓T↓G↓C↓T↓G-3'. CAG excision is slower than CTG and requires intra-strand A·A and T·T mismatches. Fully paired hairpins arrested excision, whereas disease-delaying CAA interruptions further slowed excision. Endo-nucleolytic cleavage is insensitive to slip-outs. Rare FAN1 variants are found in individuals with autism with CGG/CCG expansions, and CGG/CCG slip-outs show exo-nuclease pauses. The slip-out-specific ligand, naphthyridine-azaquinolone, which induces contractions of expanded repeats in vivo, requires FAN1 for its effect, and protects slip-outs from FAN1 exo-, but not endo-, nucleolytic digestion. FAN1's inchworm pausing of slip-out excision rates is well suited to modify inchworm expansion rates, which modify disease onset and progression.
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Affiliation(s)
- Amit Laxmikant Deshmukh
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Marie-Christine Caron
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Québec City, QC G1R 3S3, Canada; Department of Molecular Biology, Medical Biochemistry, and Pathology, Laval University Cancer Research Center, Québec City, QC G1R 3S3, Canada
| | - Mohiuddin Mohiuddin
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Stella Lanni
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Gagan B Panigrahi
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Mahreen Khan
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Worrawat Engchuan
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Natalie Shum
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Aisha Faruqui
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Peixiang Wang
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Ryan K C Yuen
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Masayuki Nakamori
- Department of Neurology, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Kazuhiko Nakatani
- Department of Regulatory Bioorganic Chemistry, the Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047, Japan
| | - Jean-Yves Masson
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Québec City, QC G1R 3S3, Canada; Department of Molecular Biology, Medical Biochemistry, and Pathology, Laval University Cancer Research Center, Québec City, QC G1R 3S3, Canada
| | - Christopher E Pearson
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada.
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Arning L, Nguyen HP. Huntington disease update: new insights into the role of repeat instability in disease pathogenesis. MED GENET-BERLIN 2021; 33:293-300. [PMID: 38835439 PMCID: PMC11006308 DOI: 10.1515/medgen-2021-2101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 11/16/2021] [Indexed: 06/06/2024]
Abstract
The causative mutation for Huntington disease (HD), an expanded trinucleotide repeat sequence in the first exon of the huntingtin gene (HTT) is naturally polymorphic and inevitably associated with disease symptoms above 39 CAG repeats. Although symptomatic medical therapies for HD can improve the motor and non-motor symptoms for affected patients, these drugs do not stop the ongoing neurodegeneration and progression of the disease, which results in severe motor and cognitive disability and death. To date, there is still an urgent need for the development of effective disease-modifying therapies to slow or even stop the progression of HD. The increasing ability to intervene directly at the roots of the disease, namely HTT transcription and translation of its mRNA, makes it necessary to understand the pathogenesis of HD as precisely as possible. In addition to the long-postulated toxicity of the polyglutamine-expanded mutant HTT protein, there is increasing evidence that the CAG repeat-containing RNA might also be directly involved in toxicity. Recent studies have identified cis- (DNA repair genes) and trans- (loss/duplication of CAA interruption) acting variants as major modifiers of age at onset (AO) and disease progression. More and more extensive data indicate that somatic instability functions as a driver for AO as well as disease progression and severity, not only in HD but also in other polyglutamine diseases. Thus, somatic expansions of repetitive DNA sequences may be essential to promote respective repeat lengths to reach a threshold leading to the overt neurodegenerative symptoms of trinucleotide diseases. These findings support somatic expansion as a potential therapeutic target in HD and related repeat expansion disorders.
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Affiliation(s)
- Larissa Arning
- Department of Human Genetics, Medical Faculty, Ruhr-University Bochum, Bochum 44780, Germany
| | - Huu Phuc Nguyen
- Department of Human Genetics, Medical Faculty, Ruhr-University Bochum, Bochum 44780, Germany
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Magri S, Nanetti L, Gellera C, Sarto E, Rizzo E, Mongelli A, Ricci B, Fancellu R, Sambati L, Cortelli P, Brusco A, Bruzzone MG, Mariotti C, Di Bella D, Taroni F. Digenic inheritance of STUB1 variants and TBP polyglutamine expansions explains the incomplete penetrance of SCA17 and SCA48. Genet Med 2021; 24:29-40. [PMID: 34906452 DOI: 10.1016/j.gim.2021.08.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 05/04/2021] [Accepted: 08/10/2021] [Indexed: 02/03/2023] Open
Abstract
PURPOSE This study aimed to unravel the genetic factors underlying missing heritability in spinocerebellar ataxia type 17 (SCA17) caused by polyglutamine-encoding CAG/CAA repeat expansions in the TBP gene. Alleles with >49 CAG/CAA repeats are fully penetrant. Most patients, however, carry intermediate TBP41-49 alleles that show incomplete penetrance. METHODS Using next-generation sequencing approaches, we investigated 40 SCA17/TBP41-54 index patients, their affected (n = 55) and unaffected (n = 51) relatives, and a cohort of patients with ataxia (n = 292). RESULTS All except 1 (30/31) of the index cases with TBP41-46 alleles carried a heterozygous pathogenic variant in the STUB1 gene associated with spinocerebellar ataxias SCAR16 (autosomal recessive) and SCA48 (autosomal dominant). No STUB1 variant was found in patients carrying TBP47-54 alleles. TBP41-46 expansions and STUB1 variants cosegregate in all affected family members, whereas the presence of either TBP41-46 expansions or STUB1 variants individually was never associated with the disease. CONCLUSION Our data reveal an unexpected genetic interaction between STUB1 and TBP in the pathogenesis of SCA17 and raise questions on the existence of SCA48 as a monogenic disease with crucial implications for diagnosis and counseling. They provide a convincing explanation for the incomplete penetrance of intermediate TBP alleles and demonstrate a dual inheritance pattern for SCA17, which is a monogenic dominant disorder for TBP≥47 alleles and a digenic TBP/STUB1 disease (SCA17-DI) for intermediate expansions.
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Affiliation(s)
- Stefania Magri
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Lorenzo Nanetti
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.
| | - Cinzia Gellera
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Elisa Sarto
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Elena Rizzo
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Alessia Mongelli
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Benedetta Ricci
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Roberto Fancellu
- Neurology Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Luisa Sambati
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy; Department of Biomedical and NeuroMotor Sciences (DiBiNeM), University of Bologna, Bologna, Italy
| | - Pietro Cortelli
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy; Department of Biomedical and NeuroMotor Sciences (DiBiNeM), University of Bologna, Bologna, Italy
| | - Alfredo Brusco
- Department of Medical Sciences, University of Turin, Turin, Italy; Medical Genetics Unit, Città della Salute e della Scienza University Hospital, Turin, Italy
| | - Maria Grazia Bruzzone
- Unit of Neuroradiology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Caterina Mariotti
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Daniela Di Bella
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Franco Taroni
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.
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Świtońska-Kurkowska K, Krist B, Delimata J, Figiel M. Juvenile Huntington's Disease and Other PolyQ Diseases, Update on Neurodevelopmental Character and Comparative Bioinformatic Review of Transcriptomic and Proteomic Data. Front Cell Dev Biol 2021; 9:642773. [PMID: 34277598 PMCID: PMC8281051 DOI: 10.3389/fcell.2021.642773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 06/10/2021] [Indexed: 01/18/2023] Open
Abstract
Polyglutamine (PolyQ) diseases are neurodegenerative disorders caused by the CAG repeat expansion mutation in affected genes resulting in toxic proteins containing a long chain of glutamines. There are nine PolyQ diseases: Huntington’s disease (HD), spinocerebellar ataxias (types 1, 2, 3, 6, 7, and 17), dentatorubral-pallidoluysian atrophy (DRPLA), and spinal bulbar muscular atrophy (SBMA). In general, longer CAG expansions and longer glutamine tracts lead to earlier disease presentations in PolyQ patients. Rarely, cases of extremely long expansions are identified for PolyQ diseases, and they consistently lead to juvenile or sometimes very severe infantile-onset polyQ syndromes. In apparent contrast to the very long CAG tracts, shorter CAGs and PolyQs in proteins seems to be the evolutionary factor enhancing human cognition. Therefore, polyQ tracts in proteins can be modifiers of brain development and disease drivers, which contribute neurodevelopmental phenotypes in juvenile- and adult-onset PolyQ diseases. Therefore we performed a bioinformatics review of published RNAseq polyQ expression data resulting from the presence of polyQ genes in search of neurodevelopmental expression patterns and comparison between diseases. The expression data were collected from cell types reflecting stages of development such as iPSC, neuronal stem cell, neurons, but also the adult patients and models for PolyQ disease. In addition, we extended our bioinformatic transcriptomic analysis by proteomics data. We identified a group of 13 commonly downregulated genes and proteins in HD mouse models. Our comparative bioinformatic review highlighted several (neuro)developmental pathways and genes identified within PolyQ diseases and mouse models responsible for neural growth, synaptogenesis, and synaptic plasticity.
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Affiliation(s)
| | - Bart Krist
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Joanna Delimata
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Maciej Figiel
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
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15
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Generation of induced pluripotent stem cell line RCPCMi008-A derived from patient with spinocerebellar ataxia 17. Stem Cell Res 2021; 54:102431. [PMID: 34171784 DOI: 10.1016/j.scr.2021.102431] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 06/10/2021] [Accepted: 06/13/2021] [Indexed: 10/21/2022] Open
Abstract
IPSC line RCPCMi004-8 was generated from skin fibroblasts collected from a male patient with spinocerebellar ataxia 17. The patient has expanded trinucleotide CAG repeats in the TBP (TATA-binding protein) gene on chromosome 6q27. The reprogramming of fibroblasts was performed with Sendai viruses containing Oct-4, Sox-2, Klf-4, and c-Myc. Pluripotency was confirmed by immunofluorescence, RT-PCR, and the formation of embryoid bodies. The RCPCMi008-A cell line carries the same trinucleotide CAG repeats in the TBP gene. The RCPCMi008-A cell line can be used to model Spinocerebellar ataxia in vitro.
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Chintalaphani SR, Pineda SS, Deveson IW, Kumar KR. An update on the neurological short tandem repeat expansion disorders and the emergence of long-read sequencing diagnostics. Acta Neuropathol Commun 2021; 9:98. [PMID: 34034831 PMCID: PMC8145836 DOI: 10.1186/s40478-021-01201-x] [Citation(s) in RCA: 77] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 05/17/2021] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Short tandem repeat (STR) expansion disorders are an important cause of human neurological disease. They have an established role in more than 40 different phenotypes including the myotonic dystrophies, Fragile X syndrome, Huntington's disease, the hereditary cerebellar ataxias, amyotrophic lateral sclerosis and frontotemporal dementia. MAIN BODY STR expansions are difficult to detect and may explain unsolved diseases, as highlighted by recent findings including: the discovery of a biallelic intronic 'AAGGG' repeat in RFC1 as the cause of cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS); and the finding of 'CGG' repeat expansions in NOTCH2NLC as the cause of neuronal intranuclear inclusion disease and a range of clinical phenotypes. However, established laboratory techniques for diagnosis of repeat expansions (repeat-primed PCR and Southern blot) are cumbersome, low-throughput and poorly suited to parallel analysis of multiple gene regions. While next generation sequencing (NGS) has been increasingly used, established short-read NGS platforms (e.g., Illumina) are unable to genotype large and/or complex repeat expansions. Long-read sequencing platforms recently developed by Oxford Nanopore Technology and Pacific Biosciences promise to overcome these limitations to deliver enhanced diagnosis of repeat expansion disorders in a rapid and cost-effective fashion. CONCLUSION We anticipate that long-read sequencing will rapidly transform the detection of short tandem repeat expansion disorders for both clinical diagnosis and gene discovery.
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Affiliation(s)
- Sanjog R. Chintalaphani
- School of Medicine, University of New South Wales, Sydney, 2052 Australia
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW 2010 Australia
| | - Sandy S. Pineda
- Garvan-Weizmann Centre for Cellular Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW 2010 Australia
- Brain and Mind Centre, University of Sydney, Camperdown, NSW 2050 Australia
| | - Ira W. Deveson
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW 2010 Australia
- Faculty of Medicine, St Vincent’s Clinical School, University of New South Wales, Sydney, NSW 2010 Australia
| | - Kishore R. Kumar
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW 2010 Australia
- Molecular Medicine Laboratory and Neurology Department, Central Clinical School, Concord Repatriation General Hospital, University of Sydney, Concord, NSW 2137 Australia
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Ajjugal Y, Tomar K, Rao DK, Rathinavelan T. Spontaneous and frequent conformational dynamics induced by A…A mismatch in d(CAA)·d(TAG) duplex. Sci Rep 2021; 11:3689. [PMID: 33574412 PMCID: PMC7878774 DOI: 10.1038/s41598-021-82669-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 01/20/2021] [Indexed: 01/20/2023] Open
Abstract
Base pair mismatches in DNA can erroneously be incorporated during replication, recombination, etc. Here, the influence of A…A mismatch in the context of 5′CAA·5′TAG sequence is explored using molecular dynamics (MD) simulation, umbrella sampling MD, circular dichroism (CD), microscale thermophoresis (MST) and NMR techniques. MD simulations reveal that the A…A mismatch experiences several transient events such as base flipping, base extrusion, etc. facilitating B–Z junction formation. A…A mismatch may assume such conformational transitions to circumvent the effect of nonisostericity with the flanking canonical base pairs so as to get accommodated in the DNA. CD and 1D proton NMR experiments further reveal that the extent of B–Z junction increases when the number of A…A mismatch in d(CAA)·d(T(A/T)G) increases (1–5). CD titration studies of d(CAA)·d(TAG)n=5 with the hZαADAR1 show the passive binding between the two, wherein, the binding of protein commences with B–Z junction recognition. Umbrella sampling simulation indicates that the mismatch samples anti…+ syn/+ syn…anti, anti…anti & + syn…+ syn glycosyl conformations. The concomitant spontaneous transitions are: a variety of hydrogen bonding patterns, stacking and minor or major groove extrahelical movements (with and without the engagement of hydrogen bonds) involving the mismatch adenines. These transitions frequently happen in anti…anti conformational region compared with the other three regions as revealed from the lifetime of these states. Further, 2D-NOESY experiments indicate that the number of cross-peaks diminishes with the increasing number of A…A mismatches implicating its dynamic nature. The spontaneous extrahelical movement seen in A…A mismatch may be a key pre-trapping event in the mismatch repair due to the accessibility of the base(s) to the sophisticated mismatch repair machinery.
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Affiliation(s)
- Yogeeshwar Ajjugal
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy District, Telangana State, 502285, India
| | - Kripi Tomar
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy District, Telangana State, 502285, India
| | - D Krishna Rao
- Tata Institute of Fundamental Research, 36/P, Gopanpally Mandal, Ranga Reddy District, Hyderabad, Telangana State, 500107, India
| | - Thenmalarchelvi Rathinavelan
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy District, Telangana State, 502285, India.
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Donaldson J, Powell S, Rickards N, Holmans P, Jones L. What is the Pathogenic CAG Expansion Length in Huntington's Disease? J Huntingtons Dis 2021; 10:175-202. [PMID: 33579866 PMCID: PMC7990448 DOI: 10.3233/jhd-200445] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Huntington's disease (HD) (OMIM 143100) is caused by an expanded CAG repeat tract in the HTT gene. The inherited CAG length is known to expand further in somatic and germline cells in HD subjects. Age at onset of the disease is inversely correlated with the inherited CAG length, but is further modulated by a series of genetic modifiers which are most likely to act on the CAG repeat in HTT that permit it to further expand. Longer repeats are more prone to expansions, and this expansion is age dependent and tissue-specific. Given that the inherited tract expands through life and most subjects develop disease in mid-life, this implies that in cells that degenerate, the CAG length is likely to be longer than the inherited length. These findings suggest two thresholds- the inherited CAG length which permits further expansion, and the intracellular pathogenic threshold, above which cells become dysfunctional and die. This two-step mechanism has been previously proposed and modelled mathematically to give an intracellular pathogenic threshold at a tract length of 115 CAG (95% confidence intervals 70- 165 CAG). Empirically, the intracellular pathogenic threshold is difficult to determine. Clues from studies of people and models of HD, and from other diseases caused by expanded repeat tracts, place this threshold between 60- 100 CAG, most likely towards the upper part of that range. We assess this evidence and discuss how the intracellular pathogenic threshold in manifest disease might be better determined. Knowing the cellular pathogenic threshold would be informative for both understanding the mechanism in HD and deploying treatments.
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Affiliation(s)
- Jasmine Donaldson
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Sophie Powell
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Nadia Rickards
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Peter Holmans
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Lesley Jones
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
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19
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I D, Proskokova T, Sikora N, Abramycheva N, Illarioshkin S. Spinocerebellar ataxia 17: full phenotype in a 42 CAG/CAA-repeats carrier. Zh Nevrol Psikhiatr Im S S Korsakova 2021; 121:100-105. [DOI: 10.17116/jnevro2021121121100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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20
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Maiuri T, Hung CL, Suart C, Begeja N, Barba-Bazan C, Peng Y, Savic N, Wong T, Truant R. DNA Repair in Huntington's Disease and Spinocerebellar Ataxias: Somatic Instability and Alternative Hypotheses. J Huntingtons Dis 2021; 10:165-173. [PMID: 33579859 PMCID: PMC7990435 DOI: 10.3233/jhd-200414] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The use of genome wide association studies (GWAS) in Huntington's disease (HD) research, driven by unbiased human data analysis, has transformed the focus of new targets that could affect age at onset. While there is a significant depth of information on DNA damage repair, with many drugs and drug targets, most of this development has taken place in the context of cancer therapy. DNA damage repair in neurons does not rely on DNA replication correction mechanisms. However, there is a strong connection between DNA repair and neuronal metabolism, mediated by nucleotide salvaging and the poly ADP-ribose (PAR) response, and this connection has been implicated in other age-onset neurodegenerative diseases. Validation of leads including the mismatch repair protein MSH3, and interstrand cross-link repair protein FAN1, suggest the mechanism is driven by somatic CAG instability, which is supported by the protective effect of CAA substitutions in the CAG tract. We currently do not understand: how somatic instability is triggered; the state of DNA damage within expanding alleles in the brain; whether this damage induces mismatch repair and interstrand cross-link pathways; whether instability mediates toxicity, and how this relates to human ageing. We discuss DNA damage pathways uncovered by HD GWAS, known roles of other polyglutamine disease proteins in DNA damage repair, and a panel of hypotheses for pathogenic mechanisms.
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Affiliation(s)
- Tamara Maiuri
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Claudia L.K. Hung
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Celeste Suart
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Nola Begeja
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Carlos Barba-Bazan
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Yi Peng
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Natasha Savic
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Timothy Wong
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Ray Truant
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
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21
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Miller JN, van der Plas E, Hamilton M, Koscik TR, Gutmann L, Cumming SA, Monckton DG, Nopoulos PC. Variant repeats within the DMPK CTG expansion protect function in myotonic dystrophy type 1. NEUROLOGY-GENETICS 2020; 6:e504. [PMID: 32851192 PMCID: PMC7428360 DOI: 10.1212/nxg.0000000000000504] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 07/09/2020] [Indexed: 01/10/2023]
Abstract
Objective We tested the hypothesis that variant repeat interruptions (RIs) within the DMPK CTG repeat tract lead to milder symptoms compared with pure repeats (PRs) in myotonic dystrophy type 1 (DM1). Methods We evaluated motor, neurocognitive, and behavioral outcomes in a group of 6 participants with DM1 with RI compared with a case-matched sample of 12 participants with DM1 with PR and a case-matched sample of 12 unaffected healthy comparison participants (UA). Results In every measure, the RI participants were intermediate between UA and PR participants. For muscle strength, the RI group was significantly less impaired than the PR group. For measures of Full Scale IQ, depression, and sleepiness, all 3 groups were significantly different from each other with UA > RI > PR in order of impairment. The RI group was different from unaffected, but not significantly different from PR (UA > RI = PR) in apathy and working memory. Finally, in finger tapping and processing speed, RI did not differ from UA comparisons, but PR had significantly lower scores than the UA comparisons (UA = RI > PR). Conclusions Our results support the notion that patients affected by DM1 with RI demonstrate a milder phenotype with the same pattern of deficits as those with PR indicating a similar disease process.
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Affiliation(s)
- Jacob N Miller
- Department of Psychiatry (J.N.M., E.P., T.R.K., P.C.N.), University of Iowa Hospitals and Clinics; West of Scotland Clinical Genetics Service (M.H.), Queen Elizabeth University Hospital; Institute of Molecular, Cell and Systems Biology (M.H., S.A.C., D.G.M.), College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom; and Department of Neurology (L.G.), University of Iowa Hospitals and Clinics
| | - Ellen van der Plas
- Department of Psychiatry (J.N.M., E.P., T.R.K., P.C.N.), University of Iowa Hospitals and Clinics; West of Scotland Clinical Genetics Service (M.H.), Queen Elizabeth University Hospital; Institute of Molecular, Cell and Systems Biology (M.H., S.A.C., D.G.M.), College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom; and Department of Neurology (L.G.), University of Iowa Hospitals and Clinics
| | - Mark Hamilton
- Department of Psychiatry (J.N.M., E.P., T.R.K., P.C.N.), University of Iowa Hospitals and Clinics; West of Scotland Clinical Genetics Service (M.H.), Queen Elizabeth University Hospital; Institute of Molecular, Cell and Systems Biology (M.H., S.A.C., D.G.M.), College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom; and Department of Neurology (L.G.), University of Iowa Hospitals and Clinics
| | - Timothy R Koscik
- Department of Psychiatry (J.N.M., E.P., T.R.K., P.C.N.), University of Iowa Hospitals and Clinics; West of Scotland Clinical Genetics Service (M.H.), Queen Elizabeth University Hospital; Institute of Molecular, Cell and Systems Biology (M.H., S.A.C., D.G.M.), College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom; and Department of Neurology (L.G.), University of Iowa Hospitals and Clinics
| | - Laurie Gutmann
- Department of Psychiatry (J.N.M., E.P., T.R.K., P.C.N.), University of Iowa Hospitals and Clinics; West of Scotland Clinical Genetics Service (M.H.), Queen Elizabeth University Hospital; Institute of Molecular, Cell and Systems Biology (M.H., S.A.C., D.G.M.), College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom; and Department of Neurology (L.G.), University of Iowa Hospitals and Clinics
| | - Sarah A Cumming
- Department of Psychiatry (J.N.M., E.P., T.R.K., P.C.N.), University of Iowa Hospitals and Clinics; West of Scotland Clinical Genetics Service (M.H.), Queen Elizabeth University Hospital; Institute of Molecular, Cell and Systems Biology (M.H., S.A.C., D.G.M.), College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom; and Department of Neurology (L.G.), University of Iowa Hospitals and Clinics
| | - Darren G Monckton
- Department of Psychiatry (J.N.M., E.P., T.R.K., P.C.N.), University of Iowa Hospitals and Clinics; West of Scotland Clinical Genetics Service (M.H.), Queen Elizabeth University Hospital; Institute of Molecular, Cell and Systems Biology (M.H., S.A.C., D.G.M.), College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom; and Department of Neurology (L.G.), University of Iowa Hospitals and Clinics
| | - Peggy C Nopoulos
- Department of Psychiatry (J.N.M., E.P., T.R.K., P.C.N.), University of Iowa Hospitals and Clinics; West of Scotland Clinical Genetics Service (M.H.), Queen Elizabeth University Hospital; Institute of Molecular, Cell and Systems Biology (M.H., S.A.C., D.G.M.), College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom; and Department of Neurology (L.G.), University of Iowa Hospitals and Clinics
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Mystery of Expansion: DNA Metabolism and Unstable Repeats. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1241:101-124. [PMID: 32383118 DOI: 10.1007/978-3-030-41283-8_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
The mammalian genome mostly contains repeated sequences. Some of these repeats are in the regulatory elements of genes, and their instability, particularly the propensity to change the repeat unit number, is responsible for 36 well-known neurodegenerative human disorders. The mechanism of repeat expansion has been an unsolved question for more than 20 years. There are a few hypotheses describing models of mutation development. Every hypothesis is based on assumptions about unusual secondary structures that violate DNA metabolism processes in the cell. Some models are based on replication errors, and other models are based on mismatch repair or base excision repair errors. Additionally, it has been shown that epigenetic regulation of gene expression can influence the probability and frequency of expansion. In this review, we consider the molecular bases of repeat expansion disorders and discuss possible mechanisms of repeat expansion during cell metabolism.
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23
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Xu P, Pan F, Roland C, Sagui C, Weninger K. Dynamics of strand slippage in DNA hairpins formed by CAG repeats: roles of sequence parity and trinucleotide interrupts. Nucleic Acids Res 2020; 48:2232-2245. [PMID: 31974547 PMCID: PMC7049705 DOI: 10.1093/nar/gkaa036] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 12/11/2019] [Accepted: 01/15/2020] [Indexed: 01/08/2023] Open
Abstract
DNA trinucleotide repeats (TRs) can exhibit dynamic expansions by integer numbers of trinucleotides that lead to neurodegenerative disorders. Strand slipped hairpins during DNA replication, repair and/or recombination may contribute to TR expansion. Here, we combine single-molecule FRET experiments and molecular dynamics studies to elucidate slipping dynamics and conformations of (CAG)n TR hairpins. We directly resolve slipping by predominantly two CAG units. The slipping kinetics depends on the even/odd repeat parity. The populated states suggest greater stability for 5′-AGCA-3′ tetraloops, compared with alternative 5′-CAG-3′ triloops. To accommodate the tetraloop, even(odd)-numbered repeats have an even(odd) number of hanging bases in the hairpin stem. In particular, a paired-end tetraloop (no hanging TR) is stable in (CAG)n = even, but such situation cannot occur in (CAG)n = odd, where the hairpin is “frustrated’’ and slips back and forth between states with one TR hanging at the 5′ or 3′ end. Trinucleotide interrupts in the repeating CAG pattern associated with altered disease phenotypes select for specific conformers with favorable loop sequences. Molecular dynamics provide atomic-level insight into the loop configurations. Reducing strand slipping in TR hairpins by sequence interruptions at the loop suggests disease-associated variations impact expansion mechanisms at the level of slipped hairpins.
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Affiliation(s)
- Pengning Xu
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Feng Pan
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Christopher Roland
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Celeste Sagui
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Keith Weninger
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
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Distribution of the CAG Triplet Repeat in ATXN1, ATXN3, and CACNA1A Loci in Peruvian Population. THE CEREBELLUM 2020; 19:527-535. [PMID: 32285347 DOI: 10.1007/s12311-020-01129-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Spinocerebellar ataxia subtypes 1, 3, and 6 (SCA1, MJD/SCA3, and SCA6) are among the most prevalent autosomal dominant cerebellar ataxias worldwide, but their relative frequencies in Peru are low. Frequency of large normal (LN) alleles at spinocerebellar ataxia-causative genes has been proposed to be associated with disease prevalence. To investigate the allelic distribution of the CAG repeat in ATXN1, ATXN3, and CACNA1A genes in a Peruvian mestizo population and examine their association with the relative frequency of SCA1, MJD/SCA3, and SCA6 across populations. We genotyped 213 healthy mestizo individuals from Northern Lima, Peru, for ATXN1, ATXN3, and CACNA1A using polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis (PAGE). We compared the frequency of LN alleles and relative disease frequency between populations. We also tested 40 samples for CAT repeat interruptions within the CAG tract of ATXN1. We found no association between disease frequency and population frequency of LN alleles at ATXN1 and ATXN3. All 40 ATXN1 samples tested for CAT interruptions were positive. Frequency of LN alleles at CACNA1A correlates with SCA6 frequency across several populations, but this effect was largely driven by data from a single population. Low frequency of SCA1 and MJD/SCA3 in Peru is not explained by frequency of LN alleles at ATXN1 and ATXN3, respectively. The observed correlation between CACNA1A LN alleles and SCA6 frequency requires further assessment.
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25
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Nakamori M, Panigrahi GB, Lanni S, Gall-Duncan T, Hayakawa H, Tanaka H, Luo J, Otabe T, Li J, Sakata A, Caron MC, Joshi N, Prasolava T, Chiang K, Masson JY, Wold MS, Wang X, Lee MYWT, Huddleston J, Munson KM, Davidson S, Layeghifard M, Edward LM, Gallon R, Santibanez-Koref M, Murata A, Takahashi MP, Eichler EE, Shlien A, Nakatani K, Mochizuki H, Pearson CE. A slipped-CAG DNA-binding small molecule induces trinucleotide-repeat contractions in vivo. Nat Genet 2020; 52:146-159. [PMID: 32060489 PMCID: PMC7043212 DOI: 10.1038/s41588-019-0575-8] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Accepted: 12/19/2019] [Indexed: 01/07/2023]
Abstract
In many repeat diseases, such as Huntington's disease (HD), ongoing repeat expansions in affected tissues contribute to disease onset, progression and severity. Inducing contractions of expanded repeats by exogenous agents is not yet possible. Traditional approaches would target proteins driving repeat mutations. Here we report a compound, naphthyridine-azaquinolone (NA), that specifically binds slipped-CAG DNA intermediates of expansion mutations, a previously unsuspected target. NA efficiently induces repeat contractions in HD patient cells as well as en masse contractions in medium spiny neurons of HD mouse striatum. Contractions are specific for the expanded allele, independently of DNA replication, require transcription across the coding CTG strand and arise by blocking repair of CAG slip-outs. NA-induced contractions depend on active expansions driven by MutSβ. NA injections in HD mouse striatum reduce mutant HTT protein aggregates, a biomarker of HD pathogenesis and severity. Repeat-structure-specific DNA ligands are a novel avenue to contract expanded repeats.
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Affiliation(s)
- Masayuki Nakamori
- Department of Neurology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Gagan B Panigrahi
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Stella Lanni
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Terence Gall-Duncan
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Hideki Hayakawa
- Department of Neurology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hana Tanaka
- Department of Neurology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Jennifer Luo
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Takahiro Otabe
- Department of Regulatory Bioorganic Chemistry, The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Jinxing Li
- Department of Regulatory Bioorganic Chemistry, The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Akihiro Sakata
- Department of Regulatory Bioorganic Chemistry, The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Marie-Christine Caron
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Quebec, Quebec, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Quebec, Quebec, Canada
| | - Niraj Joshi
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Quebec, Quebec, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Quebec, Quebec, Canada
| | - Tanya Prasolava
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Karen Chiang
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Jean-Yves Masson
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Quebec, Quebec, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Quebec, Quebec, Canada
| | - Marc S Wold
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Xiaoxiao Wang
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY, USA
| | - Marietta Y W T Lee
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY, USA
| | - John Huddleston
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, USA
| | - Katherine M Munson
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Scott Davidson
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Mehdi Layeghifard
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Lisa-Monique Edward
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Richard Gallon
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | | | - Asako Murata
- Department of Regulatory Bioorganic Chemistry, The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Masanori P Takahashi
- Department of Neurology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Evan E Eichler
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, USA
| | - Adam Shlien
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Kazuhiko Nakatani
- Department of Regulatory Bioorganic Chemistry, The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Hideki Mochizuki
- Department of Neurology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Christopher E Pearson
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada.
- Program of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
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Abstract
Spinocerebellar ataxia type 17 (SCA17) is caused by polyglutamine (polyQ) expansion in the TATA box-binding protein (TBP), which functions as a general transcription factor. Like other polyQ expansion-mediated diseases, SCA17 is characterized by late-onset and selective neurodegeneration, despite the disease protein being ubiquitously expressed in the body. To date, the pathogenesis of polyQ diseases is not fully understood, and there are no effective treatments for these devastating disorders. The well-characterized function of TBP and typical neurodegeneration in SCA17 give us opportunities to understand how polyQ expansion causes selective neurodegeneration and to develop effective therapeutics. In this review, we discuss the molecular mechanisms behind SCA17, focusing on transcriptional dysregulation as its major cause. Mounting evidence suggests that reversing transcriptional alterations induced by mutant TBP and reducing the expression of mutant TBP are promising strategies to treat SCA17.
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Affiliation(s)
- Qiong Liu
- Key Laboratory of Hunan Province in Neurodegenerative Disorders, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
- Guangdong-Hongkong-Macau Institute of CNS Regeneration, Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Jinan University, Guangzhou, China
| | - Yongcheng Pan
- Key Laboratory of Hunan Province in Neurodegenerative Disorders, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
- Guangdong-Hongkong-Macau Institute of CNS Regeneration, Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Jinan University, Guangzhou, China
| | - Xiao-Jiang Li
- Guangdong-Hongkong-Macau Institute of CNS Regeneration, Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Jinan University, Guangzhou, China.
| | - Shihua Li
- Guangdong-Hongkong-Macau Institute of CNS Regeneration, Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Jinan University, Guangzhou, China
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27
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Pešović J, Perić S, Brkušanin M, Brajušković G, Rakočević-Stojanović V, Savić-Pavićević D. Repeat Interruptions Modify Age at Onset in Myotonic Dystrophy Type 1 by Stabilizing DMPK Expansions in Somatic Cells. Front Genet 2018; 9:601. [PMID: 30546383 PMCID: PMC6278776 DOI: 10.3389/fgene.2018.00601] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/15/2018] [Indexed: 12/19/2022] Open
Abstract
CTG expansions in DMPK gene, causing myotonic dystrophy type 1 (DM1), are characterized by pronounced somatic instability. A large proportion of variability of somatic instability is explained by expansion size and patient's age at sampling, while individual-specific differences are attributed to additional factors. The age at onset is extremely variable in DM1, and inversely correlates with the expansion size and individual-specific differences in somatic instability. Three to five percent of DM1 patients carry repeat interruptions and some appear with later age at onset than expected for corresponding expansion size. Herein, we characterized somatic instability of interrupted DMPK expansions and the effect on age at onset in our previously described patients. Repeat-primed PCR showed stable structures of different types and patterns of repeat interruptions in blood cells over time and buccal cells. Single-molecule small-pool PCR quantification of somatic instability and mathematical modeling showed that interrupted expansions were characterized by lower level of somatic instability accompanied by slower progression over time. Mathematical modeling demonstrated that individual-specific differences in somatic instability had greater influence on age at onset in patients with interrupted expansions. Therefore, repeat interruptions have clinical importance for disease course in DM1 patients due to stabilizing effect on DMPK expansions in somatic cells.
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Affiliation(s)
- Jovan Pešović
- Center for Human Molecular Genetics, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Stojan Perić
- School of Medicine, University of Belgrade, Belgrade, Serbia.,Neurology Clinic, Clinical Center of Serbia, Belgrade, Serbia
| | - Miloš Brkušanin
- Center for Human Molecular Genetics, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Goran Brajušković
- Center for Human Molecular Genetics, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Vidosava Rakočević-Stojanović
- School of Medicine, University of Belgrade, Belgrade, Serbia.,Neurology Clinic, Clinical Center of Serbia, Belgrade, Serbia
| | - Dušanka Savić-Pavićević
- Center for Human Molecular Genetics, Faculty of Biology, University of Belgrade, Belgrade, Serbia
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28
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Nethisinghe S, Lim WN, Ging H, Zeitlberger A, Abeti R, Pemble S, Sweeney MG, Labrum R, Cervera C, Houlden H, Rosser E, Limousin P, Kennedy A, Lunn MP, Bhatia KP, Wood NW, Hardy J, Polke JM, Veneziano L, Brusco A, Davis MB, Giunti P. Complexity of the Genetics and Clinical Presentation of Spinocerebellar Ataxia 17. Front Cell Neurosci 2018; 12:429. [PMID: 30532692 PMCID: PMC6265347 DOI: 10.3389/fncel.2018.00429] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 10/30/2018] [Indexed: 12/31/2022] Open
Abstract
Spinocerebellar ataxia type 17 (SCA17) is a rare autosomal dominant neurodegenerative disease caused by a CAG repeat expansion in the TATA-box binding protein gene (TBP). The disease has a varied age at onset and clinical presentation. It is distinct from other SCAs for its association with dementia, psychiatric symptoms, and some patients presenting with chorea. For this reason, it is also called Huntington’s disease-like 4 (HDL-4). Here we examine the distribution of SCA17 allele repeat sizes in a United Kingdom-based cohort with ataxia and find that fully penetrant pathogenic alleles are very rare (5 in 1,316 chromosomes; 0.38%). Phenotype-genotype correlation was performed on 30 individuals and the repeat structure of their TBP genes was examined. We found a negative linear correlation between total CAG repeat length and age at disease onset and, unlike SCA1, there was no correlation between the longest contiguous CAG tract and age at disease onset. We were unable to identify any particular phenotypic trait that segregated with particular CAG/CAA repeat tract structures or repeat lengths. One individual within the cohort was homozygous for variable penetrance range SCA17 alleles. This patient had a similar age at onset to heterozygotes with the same repeat sizes, but also presented with a rapidly progressive dementia. A pair of monozygotic twins within the cohort presented 3 years apart with the sibling with the earlier onset having a more severe phenotype with dementia and chorea in addition to the ataxia observed in their twin. This appears to be a case of variable expressivity, possibly influenced by other environmental or epigenetic factors. Finally, there was an asymptomatic father with a severely affected child with an age at onset in their twenties. Despite this, they share the same expanded allele repeat sizes and sequences, which would suggest that there is marked difference in the penetrance of this 51-repeat allele. We therefore propose that the variable penetrance range extend from 48 repeats to incorporate this allele. This study shows that there is variability in the presentation and penetrance of the SCA17 phenotype and highlights the complexity of this disorder.
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Affiliation(s)
- Suran Nethisinghe
- Ataxia Centre, Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Wei N Lim
- Ataxia Centre, Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Heather Ging
- Ataxia Centre, Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Anna Zeitlberger
- Ataxia Centre, Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Rosella Abeti
- Ataxia Centre, Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Sally Pemble
- Neurogenetics Unit, National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Mary G Sweeney
- Neurogenetics Unit, National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Robyn Labrum
- Neurogenetics Unit, National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Charisse Cervera
- Neurogenetics Unit, National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Henry Houlden
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom.,MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Elisabeth Rosser
- Department of Clinical Genetics, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Patricia Limousin
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Angus Kennedy
- Chelsea and Westminster Hospital, London, United Kingdom
| | - Michael P Lunn
- Department of Neuroimmunology, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Kailash P Bhatia
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Nicholas W Wood
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - John Hardy
- Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, London, United Kingdom.,The Reta Lila Weston Institute of Neurological Studies, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - James M Polke
- Neurogenetics Unit, National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Liana Veneziano
- Istituto di Farmacologia Traslazionale - National Research Council, Rome, Italy
| | - Alfredo Brusco
- Department of Medical Sciences, University of Turin, Turin, Italy.,Medical Genetics Unit, Città della Salute e della Scienza University Hospital, Turin, Italy
| | - Mary B Davis
- Ataxia Centre, Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Paola Giunti
- Ataxia Centre, Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom
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29
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Abstract
This review explores the presence and functions of polyglutamine (polyQ) in viral proteins. In mammals, mutations in polyQ segments (and CAG repeats at the nucleotide level) have been linked to neural disorders and ataxias. PolyQ regions in normal human proteins have documented functional roles, in transcription factors and, more recently, in regulating autophagy. Despite the high frequency of polyQ repeats in eukaryotic genomes, little attention has been given to the presence or possible role of polyQ sequences in virus genomes. A survey described here revealed that polyQ repeats occur rarely in RNA viruses, suggesting that they have detrimental effects on virus replication at the nucleotide or protein level. However, there have been sporadic reports of polyQ segments in potyviruses and in reptilian nidoviruses (among the largest RNA viruses known). Conserved polyQ segments are found in the regulatory control proteins of many DNA viruses. Variable length polyQ tracts are found in proteins that contribute to transmissibility (cowpox A-type inclusion protein (ATI)) and control of latency (herpes viruses). New longer-read sequencing methods, using original biological samples, should reveal more details on the presence and functional role of polyQ in viruses, as well as the nucleotide regions that encode them. Given the known toxic effects of polyQ repeats, the role of these segments in neurovirulent and tumorigenic viruses should be further explored.
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30
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Abstract
Diseases such as Huntington's disease and certain spinocerebellar ataxias are caused by the expansion of genomic cytosine-adenine-guanine (CAG) trinucleotide repeats beyond a specific threshold. These diseases are all characterised by neurological symptoms and central neurodegeneration, but our understanding of how expanded repeats drive neuronal loss is incomplete. Recent human genetic evidence implicates DNA repair pathways, especially mismatch repair, in modifying the onset and progression of CAG repeat diseases. Repair pathways might operate directly on repeat sequences by licensing or inhibiting repeat expansion in neurons. Alternatively, or in addition, because many of the genes containing pathogenic CAG repeats encode proteins that themselves have roles in the DNA damage response, it is possible that repeat expansions impair specific DNA repair pathways. DNA damage could then accrue in neurons, leading to further expansion at repeat loci, thus setting up a vicious cycle of pathology. In this review, we consider DNA damage and repair pathways in postmitotic neurons in the context of disease-causing CAG repeats. Investigating and understanding these pathways, which are clearly relevant in promoting and ameliorating disease in humans, is a research priority, as they are known to modify disease and therefore constitute prevalidated drug targets.
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Affiliation(s)
- Thomas H Massey
- Institute of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, Hadyn Ellis Building, Cardiff University, Cardiff, CF24 4HQ, UK
| | - Lesley Jones
- Institute of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, Hadyn Ellis Building, Cardiff University, Cardiff, CF24 4HQ, UK
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31
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32
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Toyoshima Y, Takahashi H. Spinocerebellar Ataxia Type 17 (SCA17). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1049:219-231. [PMID: 29427105 DOI: 10.1007/978-3-319-71779-1_10] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
In 1999, a polyglutamine expansion was identified in the transcription factor TATA-binding protein (TBP) in a patient with ataxia with negative family history. Subsequently, CAG/CAA repeat expansions in the TBP gene were identified in families with spinocerebellar ataxia (SCA), establishing this repeat expansion as the underlying mutation in SCA type 17 (SCA17). There are several characteristic differences between SCA17 and other polyglutamine diseases. First, SCA17 shows a complex and variable clinical phenotype, in some cases overlapping that of Huntington's disease. Second, compared to the other SCA subtypes caused by expanded trinucleotide repeats, anticipation in SCA17 kindreds is rare because of the characteristic structure of the TBP gene. And thirdly, SCA17 patients often have diagnostic problems that may arise from non-penetrance. Because the gap between normal and abnormal repeat numbers is very narrow, it is difficult to determine a cutoff value for pathologic CAG repeat number in SCA17. Herein, we review the clinical, genetic and pathologic features of SCA17.
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Affiliation(s)
- Yasuko Toyoshima
- Department of Pathology, Brain Research Institute, University of Niigata, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Japan.
| | - Hitoshi Takahashi
- Department of Pathology, Brain Research Institute, University of Niigata, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Japan
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33
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Pešović J, Perić S, Brkušanin M, Brajušković G, Rakočević-Stojanović V, Savić-Pavićević D. Molecular genetic and clinical characterization of myotonic dystrophy type 1 patients carrying variant repeats within DMPK expansions. Neurogenetics 2017; 18:207-218. [DOI: 10.1007/s10048-017-0523-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Accepted: 09/05/2017] [Indexed: 12/22/2022]
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34
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Cui Y, Yang S, Li XJ, Li S. Genetically modified rodent models of SCA17. J Neurosci Res 2017; 95:1540-1547. [PMID: 27859490 PMCID: PMC5508981 DOI: 10.1002/jnr.23984] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 09/21/2016] [Accepted: 10/11/2016] [Indexed: 12/16/2022]
Abstract
Spinocerebellar ataxia type 17 (SCA17) is a type of autosomal dominant cerebellar ataxia (ADCA) characterized by variable manifestations, including cerebellar ataxia, dementia, and psychiatric symptoms. Since the identification of a CAG repeat expansion in the TATA-box binding protein (TBP) gene in a patient with ataxia in 1999 and then verification of this expansion in patients with SCA17 in 2001, several SCA17 rodent models, including both knock-in and transgenic models in mice and rats, have been established to explore the phenotypic features and pathogenesis of SCA17. These animal models revealed different pathological changes and phenotypes that are associated with the expression of mutant TBP protein and the CAG repeat lengths. It is important to understand how mutant TBP can cause differential pathological events in SCA17 animal models. In this review, we summarize and compare these animal models for the nature of transgenes and their expression as well as phenotypical features. We also discuss potential directions for future studies. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Yiting Cui
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, People’s Republic of China
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, Georgia 30322, USA
| | - Su Yang
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, Georgia 30322, USA
| | - Xiao-Jiang Li
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, Georgia 30322, USA
| | - Shihua Li
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, Georgia 30322, USA
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35
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Lindsay E, Storey E. Cognitive Changes in the Spinocerebellar Ataxias Due to Expanded Polyglutamine Tracts: A Survey of the Literature. Brain Sci 2017; 7:brainsci7070083. [PMID: 28708110 PMCID: PMC5532596 DOI: 10.3390/brainsci7070083] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 06/27/2017] [Accepted: 07/06/2017] [Indexed: 12/18/2022] Open
Abstract
The dominantly-inherited ataxias characterised by expanded polyglutamine tracts—spinocere bellar ataxias (SCAs) 1, 2, 3, 6, 7, 17, dentatorubral pallidoluysian atrophy (DRPLA) and, in part, SCA 8—have all been shown to result in various degrees of cognitive impairment. We survey the literature on the cognitive consequences of each disorder, attempting correlation with their published neuropathological, magnetic resonance imaging (MRI) and clinical features. We suggest several psychometric instruments for assessment of executive function, whose results are unlikely to be confounded by visual, articulatory or upper limb motor difficulties. Finally, and with acknowledgement of the inadequacies of the literature to date, we advance a tentative classification of these disorders into three groups, based on the reported severity of their cognitive impairments, and correlated with their neuropathological topography and MRI findings: group 1—SCAs 6 and 8—mild dysexecutive syndrome based on disruption of cerebello-cortical circuitry; group 2—SCAs 1, 2, 3, and 7—more extensive deficits based largely on disruption of striatocortical in addition to cerebello-cerebral circuitry; and group 3—SCA 17 and DRPLA—in which cognitive impairment severe enough to cause a dementia syndrome is a frequent feature.
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Affiliation(s)
- Evelyn Lindsay
- Department of Medicine (Neuroscience), Monash University (Alfred Hospital Campus), Commercial Road, Melbourne, VIC 3004, Australia.
| | - Elsdon Storey
- Department of Medicine (Neuroscience), Monash University (Alfred Hospital Campus), Commercial Road, Melbourne, VIC 3004, Australia.
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36
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Gomes-Pereira M, Monckton DG. Ethidium Bromide Modifies The Agarose Electrophoretic Mobility of CAG•CTG Alternative DNA Structures Generated by PCR. Front Cell Neurosci 2017; 11:153. [PMID: 28611596 PMCID: PMC5447772 DOI: 10.3389/fncel.2017.00153] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 05/10/2017] [Indexed: 12/21/2022] Open
Abstract
The abnormal expansion of unstable simple sequence DNA repeats can cause human disease through a variety of mechanisms, including gene loss-of-function, toxic gain-of-function of the encoded protein and toxicity of the repeat-containing RNA transcript. Disease-associated unstable DNA repeats display unusual biophysical properties, including the ability to adopt non-B-DNA structures. CAG•CTG trinucleotide sequences, in particular, have been most extensively studied and they can fold into slipped-stranded DNA structures, which have been proposed as mutation intermediates in repeat size expansion. Here, we describe a simple assay to detect unusual DNA structures generated by PCR amplification, based on their slow electrophoretic migration in agarose and on the effects of ethidium bromide on the mobility of structural isoforms through agarose gels. Notably, the inclusion of ethidium bromide in agarose gels and running buffer eliminates the detection of additional slow-migrating DNA species, which are detected in the absence of the intercalating dye and may be incorrectly classified as mutant alleles with larger than actual expansion sizes. Denaturing and re-annealing experiments confirmed the slipped-stranded nature of the additional DNA species observed in agarose gels. Thus, we have shown that genuine non-B-DNA conformations are generated during standard PCR amplification of CAG•CTG sequences and detected by agarose gel electrophoresis. In contrast, ethidium bromide does not change the multi-band electrophoretic profiles of repeat-containing PCR products through native polyacrylamide gels. These data have implications for the analysis of trinucleotide repeat DNA and possibly other types of unstable repetitive DNA sequences by standard agarose gel electrophoresis in diagnostic and research protocols. We suggest that proper sizing of CAG•CTG PCR products in agarose gels should be performed in the presence of ethidium bromide.
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Affiliation(s)
- Mário Gomes-Pereira
- Laboratory CTGDM, INSERM UMR1163Paris, France.,Institut Imagine, Université Paris Descartes-Sorbonne Paris CitéParis, France
| | - Darren G Monckton
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgow, United Kingdom
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Zhang N, Ashizawa T. RNA toxicity and foci formation in microsatellite expansion diseases. Curr Opin Genet Dev 2017; 44:17-29. [PMID: 28208060 DOI: 10.1016/j.gde.2017.01.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 01/04/2017] [Accepted: 01/18/2017] [Indexed: 12/11/2022]
Abstract
More than 30 incurable neurological and neuromuscular diseases are caused by simple microsatellite expansions consisted of 3-6 nucleotides. These repeats can occur in non-coding regions and often result in a dominantly inherited disease phenotype that is characteristic of a toxic RNA gain-of-function. The expanded RNA adopts unusual secondary structures, sequesters various RNA binding proteins to form insoluble nuclear foci, and causes cellular defects at a multisystem level. Nuclear foci are dynamic in size, shape and colocalization of RNA binding proteins in different expansion diseases and tissue types. This review sets to provide new insights into the disease mechanisms of RNA toxicity and foci modulation, in light of recent advancement on bi-directional transcription, antisense RNA, repeat-associated non-ATG translation and beyond.
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Affiliation(s)
- Nan Zhang
- Neurosciences Research Program, Houston Methodist Research Institute, Houston, TX 77030, United States; Division of Cell and Molecular Biology, South Kensington Campus, Imperial College London, London SW7 2AZ, UK
| | - Tetsuo Ashizawa
- Neurosciences Research Program, Houston Methodist Research Institute, Houston, TX 77030, United States.
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Ardui S, Race V, Zablotskaya A, Hestand MS, Van Esch H, Devriendt K, Matthijs G, Vermeesch JR. Detecting AGG Interruptions in Male and Female FMR1 Premutation Carriers by Single-Molecule Sequencing. Hum Mutat 2017; 38:324-331. [DOI: 10.1002/humu.23150] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 11/02/2016] [Accepted: 11/17/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Simon Ardui
- Department of Human Genetics; KU Leuven; Leuven Belgium
| | - Valerie Race
- Department of Human Genetics; KU Leuven; Leuven Belgium
| | | | | | | | | | - Gert Matthijs
- Department of Human Genetics; KU Leuven; Leuven Belgium
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Conformational modulation mediated by polyglutamine expansion in CAG repeat expansion disease-associated proteins. Biochem Biophys Res Commun 2016; 478:949-55. [PMID: 27520369 DOI: 10.1016/j.bbrc.2016.08.057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 08/08/2016] [Indexed: 12/26/2022]
Abstract
We have previously reported TR-FRET based immunoassays to detect a conformational change imparted on huntingtin protein by the polyglutamine expansion, which we confirmed using biophysical methodologies. Using these immunoassays, we now report that polyglutamine expansion influences the conformational properties of other polyglutamine disease proteins, exemplified by the androgen receptor (associated with spinal bulbar muscular atrophy) and TATA binding protein (associated with spinocerebellar ataxia 17). Using artificial constructs bearing short or long polyglutamine expansions or a multimerized, unrelated epitope (mimicking the increase in anti-polyglutamine antibody epitopes present in polyglutamine repeats of increasing length) we confirmed that the conformational TR-FRET based immunoassay detects an intrinsic conformational property of polyglutamine repeats. The TR-FRET based conformational immunoassay may represent a rapid, scalable tool to identify modulators of polyglutamine-mediated conformational change in different proteins associated with CAG triplet repeat disorders.
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40
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Zhang R, Chen X, Li P, Lu X, Liu Y, Li Y, Zhang L, Xu M, Cram DS. Molecular characterization of a novel ring 6 chromosome using next generation sequencing. Mol Cytogenet 2016; 9:33. [PMID: 27103944 PMCID: PMC4839136 DOI: 10.1186/s13039-016-0245-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2016] [Accepted: 04/12/2016] [Indexed: 12/24/2022] Open
Abstract
Background Karyotyping is the gold standard cytogenetic method for detection of ring chromosomes. In this study we report the molecular characterization of a novel ring 6 (r6) chromosome in a six-year-old girl with severe mental retardation, congenital heart disease and craniofacial abnormalities. Methods Cytogenetic analysis was performed by conventional karyotyping. Molecular genetic analyses were performed using high-resolution chromosome microarray analysis (CMA) and next generation sequencing (NGS). OMIM, UCSC and PubMed were used as reference databases to determine potential genotype to phenotype associations. Results Peripheral blood and skin fibroblast karyotyping revealed the presence of a dominant cell line, 46,XX,(r6)(p25.3;q27) and a minor cell line 45,XX,-6. Molecular karyotyping using NGS identified 6p25.3 and 6q27 subtelomeric deletions of 1.78 Mb and a 0.56 Mb, respectively. Based on the known genes located within the r6 deletion interval 6q25.3-pter, genotype to phenotype association studies found compelling evidence to suggest that hemizygous expression of disease genes FOXC1, FOXF2, IRF4 and GMDS was the main underlying cause of the patient’s phenotype. We further speculate that the severity of the patient’s symptoms may have been exacerbated by low-level instability of the r6 chromosome. Conclusion This is the first report of a novel r6 chromosome characterized at the molecular level using NGS.
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Affiliation(s)
- Rui Zhang
- Center for Obstetrics and Prenatal Diagnosis, The Second Affiliated Hospital of Harbin Medical University, 150000 Harbin, China
| | - Xuan Chen
- Center for Obstetrics and Prenatal Diagnosis, The Second Affiliated Hospital of Harbin Medical University, 150000 Harbin, China
| | - Peiling Li
- Department of Obstetrics and Gynaecology, The Second Affiliated Hospital of Harbin Medical University, 150000 Harbin, China
| | - Xiumin Lu
- Center for Obstetrics and Prenatal Diagnosis, The Second Affiliated Hospital of Harbin Medical University, 150000 Harbin, China
| | - Yu Liu
- Center for Obstetrics and Prenatal Diagnosis, The Second Affiliated Hospital of Harbin Medical University, 150000 Harbin, China
| | - Yan Li
- Center for Obstetrics and Prenatal Diagnosis, The Second Affiliated Hospital of Harbin Medical University, 150000 Harbin, China
| | - Liang Zhang
- Translational Medicine Center, Guangdong Women and Children's Hospital, Guangzhou, 511400 China
| | - Mengnan Xu
- Berry Genomics Corporation, Building 9, No 6 Court Jingshun East Road, Chaoyang District, Beijing, 100015 China
| | - David S Cram
- Berry Genomics Corporation, Building 9, No 6 Court Jingshun East Road, Chaoyang District, Beijing, 100015 China
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Hekman KE, Gomez CM. The autosomal dominant spinocerebellar ataxias: emerging mechanistic themes suggest pervasive Purkinje cell vulnerability. J Neurol Neurosurg Psychiatry 2015; 86:554-61. [PMID: 25136055 PMCID: PMC6718294 DOI: 10.1136/jnnp-2014-308421] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 07/27/2014] [Indexed: 01/05/2023]
Abstract
The spinocerebellar ataxias are a genetically heterogeneous group of disorders with clinically overlapping phenotypes arising from Purkinje cell degeneration, cerebellar atrophy and varying degrees of degeneration of other grey matter regions. For 22 of the 32 subtypes, a genetic cause has been identified. While recurring themes are emerging, there is no clear correlation between the clinical phenotype or penetrance, the type of genetic defect or the category of the disease mechanism, or the neuronal types involved beyond Purkinje cells. These phenomena suggest that cerebellar Purkinje cells may be a uniquely vulnerable neuronal cell type, more susceptible to a wider variety of genetic/cellular insults than most other neuron types.
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Affiliation(s)
- Katherine E Hekman
- Department of Vascular Surgery, McGaw Medical Center of Northwestern University, Chicago, Illinois, USA
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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: 127] [Impact Index Per Article: 14.1] [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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43
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Subramony S, Moscovich M, Ashizawa T. Genetics and Clinical Features of Inherited Ataxias. Mov Disord 2015. [DOI: 10.1016/b978-0-12-405195-9.00062-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Abstract
Heredoataxias are a group of genetic disorders with a cerebellar syndrome as the leading clinical manifestation. The current classification distinguishes heredoataxias according to the trait of inheritance into autosomal dominant, autosomal recessive, X-linked, and maternally inherited heredoataxias. The autosomal dominant heredoataxias are separated into spinocerebellar ataxias (SCA1-8, 10-15, 17-23, 25-30, and dentato-rubro-pallido-luysian atrophy), episodic ataxias (EA1-7), and autosomal dominant mitochondrial heredoataxias (Leigh syndrome, MIRAS, ADOAD, and AD-CPEO). The autosomal recessive ataxias are separated into Friedreich ataxia, ataxia due to vitamin E deficiency, ataxia due to Abeta-lipoproteinemia, Refsum disease, late-onset Tay-Sachs disease, cerebrotendineous xanthomatosis, spinocerebellar ataxia with axonal neuropathy, ataxia telangiectasia, ataxia telangiectasia-like disorder, ataxia with oculomotor apraxia 1 and 2, spastic ataxia of Charlevoix-Saguenay, Cayman ataxia, Marinesco-Sjögren syndrome, and autosomal recessive mitochondrial ataxias (AR-CPEO, SANDO, SCAE, AHS, IOSCA, MEMSA, LBSL CoQ-deficiency, PDC-deficiency). Only two of the heredoataxias, fragile X/tremor/ataxia syndrome, and XLSA/A are transmitted via an X-linked trait. Maternally inherited heredoataxias are due to point mutations in genes encoding for tRNAs, rRNAs, respiratory chain subunits or single large scale deletions/duplications of the mitochondrial DNA and include MELAS, MERRF, KSS, PS, MILS, NARP, and non-syndromic mitochondrial disorders. Treatment of heredoataxias is symptomatic and supportive and may have a beneficial effect in single patients.**Please see page 424 for abbreviation list.
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Abstract
PURPOSE OF REVIEW The differential diagnosis of chorea syndromes may be complex and includes various genetic disorders such as Huntington's disease and mimicking disorders called Huntington's disease-like (HDL) phenotypes. To familiarize clinicians with these (in some cases very rare) conditions we will summarize the main characteristics. RECENT FINDINGS HDL disorders are rare and account for about 1% of cases presenting with a Huntington's disease phenotype. They share overlapping clinical features, so making the diagnosis purely on clinical grounds may be challenging, however presence of certain characteristics may be a clue (e.g. prominent orofacial involvement in neuroferritinopathy etc.), Information of ethnic descent will also guide genetic work-up [HDL2 in Black Africans; dentatorubral-pallidoluysian atrophy (DRPLA) in Japanese etc.], Huntington's disease, the classical HDL disorders (except HDL3) and DRPLA are repeat disorders with anticipation effect and age-dependent phenotype in some, but genetic underpinnings may be more complicated in the other chorea syndromes. SUMMARY With advances in genetics more and more rare diseases are disentangled, allowing molecular diagnoses in a growing number of choreic patients. Hopefully, with better understanding of their pathophysiology we are moving towards mechanistic therapies.
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46
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Roos RA. Genetic diagnosis of hyperkinetic movement disorders. ACTA ACUST UNITED AC 2013; 6:439-47. [PMID: 23480808 DOI: 10.1517/17530059.2012.704017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION People with hyperkinetic movements have always attracted the attention of the public and professionals. Alert colleagues noticed families in which a disease passed from generation to generation around Lake Maracaibo in Venezuela. This study led in 1993 to the localization of the gene for Huntington disease on chromosome 4. The genetic basis of many other familial and sporadic diseases has been identified on human DNA. AREAS COVERED The clinical presentation of hyperkinesias remains the starting point for diagnosis, but differential diagnosis is a long, difficult process, the first step being to differentiate between inherited and non-inherited forms. The need to know the diagnosis is of major importance for patient and family. Knowledge about the cause limits the number of extra diagnostics. This review of the literature presents the most frequently occurring genetically-determined forms of hyperkinesias, mainly chorea and dystonia and tries to give some practical guidelines. EXPERT OPINION The final part of the review will offer some thoughts and views for future development in a world which probably has more knowledge than we can handle. The drive to find a diagnosis is rewarded by the patient but one also needs to reflect on the use of medical care.
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Affiliation(s)
- Raymund Ac Roos
- Leiden University Medical Centre, Department of Neurology , K5Q 112, LUMC, PO Box 9600, 2300RC Leiden , The Netherlands +0031 71 526 2197 ; +0031 71 524 8253 ;
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Seidel K, Siswanto S, Brunt ERP, den Dunnen W, Korf HW, Rüb U. Brain pathology of spinocerebellar ataxias. Acta Neuropathol 2012; 124:1-21. [PMID: 22684686 DOI: 10.1007/s00401-012-1000-x] [Citation(s) in RCA: 278] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 05/25/2012] [Accepted: 05/25/2012] [Indexed: 12/22/2022]
Abstract
The autosomal dominant cerebellar ataxias (ADCAs) represent a heterogeneous group of neurodegenerative diseases with progressive ataxia and cerebellar degeneration. The current classification of this disease group is based on the underlying genetic defects and their typical disease courses. According to this categorization, ADCAs are divided into the spinocerebellar ataxias (SCAs) with a progressive disease course, and the episodic ataxias (EA) with episodic occurrences of ataxia. The prominent disease symptoms of the currently known and genetically defined 31 SCA types result from damage to the cerebellum and interconnected brain grays and are often accompanied by more specific extra-cerebellar symptoms. In the present review, we report the genetic and clinical background of the known SCAs and present the state of neuropathological investigations of brain tissue from SCA patients in the final disease stages. Recent findings show that the brain is commonly seriously affected in the polyglutamine SCAs (i.e. SCA1, SCA2, SCA3, SCA6, SCA7, and SCA17) and that the patterns of brain damage in these diseases overlap considerably in patients suffering from advanced disease stages. In the more rarely occurring non-polyglutamine SCAs, post-mortem neuropathological data currently are scanty and investigations have been primarily performed in vivo by means of MRI brain imaging. Only a minority of SCAs exhibit symptoms and degenerative patterns allowing for a clear and unambiguous diagnosis of the disease, e.g. retinal degeneration in SCA7, tau aggregation in SCA11, dentate calcification in SCA20, protein depositions in the Purkinje cell layer in SCA31, azoospermia in SCA32, and neurocutaneous phenotype in SCA34. The disease proteins of polyglutamine ataxias and some non-polyglutamine ataxias aggregate as cytoplasmic or intranuclear inclusions and serve as morphological markers. Although inclusions may impair axonal transport, bind transcription factors, and block protein quality control, detailed molecular and pathogenetic consequences remain to be determined.
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Affiliation(s)
- Kay Seidel
- Dr. Senckenbergisches Chronomedizinisches Institut, Goethe University, Theodor-Stern-Kai 7, 60950, Frankfurt/Main, Germany
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Atanesyan L, Günther V, Dichtl B, Georgiev O, Schaffner W. Polyglutamine tracts as modulators of transcriptional activation from yeast to mammals. Biol Chem 2012; 393:63-70. [DOI: 10.1515/bc-2011-252] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 11/09/2011] [Indexed: 11/15/2022]
Abstract
Abstract
Microsatellite repeats are genetically unstable and subject to expansion and shrinkage. A subset of them, triplet repeats, can occur within the coding region and specify homomeric tracts of amino acids. Polyglutamine (polyQ) tracts are enriched in eukaryotic regulatory proteins, notably transcription factors, and we had shown before that they can contribute to transcriptional activation in mammalian cells. Here we generalize this finding by also including evolutionarily divergent organisms, namely, Drosophila and baker’s yeast. In all three systems, Gal4-based model transcription factors were more active if they harbored a polyQ tract, and the activity depended on the length of the tract. By contrast, a polyserine tract was inactive. PolyQs acted from either an internal or a C-terminal position, thus ruling out a merely structural ‘linker’ effect. Finally, a two-hybrid assay in mammalian cells showed that polyQ tracts can interact with each other, supporting the concept that a polyQ-containing transcription factor can recruit other factors with polyQ tracts or glutamine-rich activation domains. The widespread occurrence of polyQ repeats in regulatory proteins suggests a beneficial role; in addition to the contribution to transcriptional activity, their genetic instability might help a species to adapt to changing environmental conditions in a potentially reversible manner.
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Nestor CE, Monckton DG. Correlation of inter-locus polyglutamine toxicity with CAG•CTG triplet repeat expandability and flanking genomic DNA GC content. PLoS One 2011; 6:e28260. [PMID: 22163004 PMCID: PMC3232215 DOI: 10.1371/journal.pone.0028260] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 11/04/2011] [Indexed: 11/19/2022] Open
Abstract
Dynamic expansions of toxic polyglutamine (polyQ)-encoding CAG repeats in ubiquitously expressed, but otherwise unrelated, genes cause a number of late-onset progressive neurodegenerative disorders, including Huntington disease and the spinocerebellar ataxias. As polyQ toxicity in these disorders increases with repeat length, the intergenerational expansion of unstable CAG repeats leads to anticipation, an earlier age-at-onset in successive generations. Crucially, disease associated alleles are also somatically unstable and continue to expand throughout the lifetime of the individual. Interestingly, the inherited polyQ length mediating a specific age-at-onset of symptoms varies markedly between disorders. It is widely assumed that these inter-locus differences in polyQ toxicity are mediated by protein context effects. Previously, we demonstrated that the tendency of expanded CAG•CTG repeats to undergo further intergenerational expansion (their 'expandability') also differs between disorders and these effects are strongly correlated with the GC content of the genomic flanking DNA. Here we show that the inter-locus toxicity of the expanded polyQ tracts of these disorders also correlates with both the expandability of the underlying CAG repeat and the GC content of the genomic DNA flanking sequences. Inter-locus polyQ toxicity does not correlate with properties of the mRNA or protein sequences, with polyQ location within the gene or protein, or steady state transcript levels in the brain. These data suggest that the observed inter-locus differences in polyQ toxicity are not mediated solely by protein context effects, but that genomic context is also important, an effect that may be mediated by modifying the rate at which somatic expansion of the DNA delivers proteins to their cytotoxic state.
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Affiliation(s)
- Colm E Nestor
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
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50
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Yu Z, Zhu Y, Chen-Plotkin AS, Clay-Falcone D, McCluskey L, Elman L, Kalb RG, Trojanowski JQ, Lee VMY, Van Deerlin VM, Gitler AD, Bonini NM. PolyQ repeat expansions in ATXN2 associated with ALS are CAA interrupted repeats. PLoS One 2011; 6:e17951. [PMID: 21479228 PMCID: PMC3066214 DOI: 10.1371/journal.pone.0017951] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Accepted: 02/16/2011] [Indexed: 12/12/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating, rapidly progressive disease leading to paralysis and death. Recently, intermediate length polyglutamine (polyQ) repeats of 27-33 in ATAXIN-2 (ATXN2), encoding the ATXN2 protein, were found to increase risk for ALS. In ATXN2, polyQ expansions of ≥ 34, which are pure CAG repeat expansions, cause spinocerebellar ataxia type 2. However, similar length expansions that are interrupted with other codons, can present atypically with parkinsonism, suggesting that configuration of the repeat sequence plays an important role in disease manifestation in ATXN2 polyQ expansion diseases. Here we determined whether the expansions in ATXN2 associated with ALS were pure or interrupted CAG repeats, and defined single nucleotide polymorphisms (SNPs) rs695871 and rs695872 in exon 1 of the gene, to assess haplotype association. We found that the expanded repeat alleles of 40 ALS patients and 9 long-repeat length controls were all interrupted, bearing 1-3 CAA codons within the CAG repeat. 21/21 expanded ALS chromosomes with 3CAA interruptions arose from one haplotype (GT), while 18/19 expanded ALS chromosomes with <3CAA interruptions arose from a different haplotype (CC). Moreover, age of disease onset was significantly earlier in patients bearing 3 interruptions vs fewer, and was distinct between haplotypes. These results indicate that CAG repeat expansions in ATXN2 associated with ALS are uniformly interrupted repeats and that the nature of the repeat sequence and haplotype, as well as length of polyQ repeat, may play a role in the neurological effect conferred by expansions in ATXN2.
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Affiliation(s)
- Zhenming Yu
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Yongqing Zhu
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Alice S. Chen-Plotkin
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Dana Clay-Falcone
- Center for Neurodegenerative Disease Research, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Leo McCluskey
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Lauren Elman
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Robert G. Kalb
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - John Q. Trojanowski
- Center for Neurodegenerative Disease Research, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Virginia M.-Y. Lee
- Center for Neurodegenerative Disease Research, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Vivianna M. Van Deerlin
- Center for Neurodegenerative Disease Research, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Aaron D. Gitler
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Nancy M. Bonini
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Howard Hughes Medical Institute, Philadelphia, Pennsylvania, United States of America
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