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Wang N, Zhang S, Langfelder P, Ramanathan L, Plascencia M, Gao F, Vaca R, Gu X, Deng L, Dionisio LE, Prasad BC, Vogt T, Horvath S, Aaronson JS, Rosinski J, Yang XW. Msh3 and Pms1 Set Neuronal CAG-repeat Migration Rate to Drive Selective Striatal and Cortical Pathogenesis in HD Mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.09.602815. [PMID: 39026894 PMCID: PMC11257559 DOI: 10.1101/2024.07.09.602815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Modifiers of Huntington's disease (HD) include mismatch repair (MMR) genes; however, their underlying disease-altering mechanisms remain unresolved. Knockout (KO) alleles for 9 HD GWAS modifiers/MMR genes were crossed to the Q140 Huntingtin (mHtt) knock-in mice to probe such mechanisms. Four KO mice strongly ( Msh3 and Pms1 ) or moderately ( Msh2 and Mlh1 ) rescue a triad of adult-onset, striatal medium-spiny-neuron (MSN)-selective phenotypes: somatic Htt DNA CAG-repeat expansion, transcriptionopathy, and mHtt protein aggregation. Comparatively, Q140 cortex also exhibits an analogous, but later-onset, pathogenic triad that is Msh3 -dependent. Remarkably, Q140/homozygous Msh3-KO lacks visible mHtt aggregates in the brain, even at advanced ages (20-months). Moreover, Msh3 -deficiency prevents striatal synaptic marker loss, astrogliosis, and locomotor impairment in HD mice. Purified Q140 MSN nuclei exhibit highly linear age-dependent mHtt DNA repeat expansion (i.e. repeat migration), with modal-CAG increasing at +8.8 repeats/month (R 2 =0.98). This linear rate is reduced to 2.3 and 0.3 repeats/month in Q140 with Msh3 heterozygous and homozygous alleles, respectively. Our study defines somatic Htt CAG-repeat thresholds below which there are no detectable mHtt nuclear or neuropil aggregates. Mild transcriptionopathy can still occur in Q140 mice with stabilized Htt 140-CAG repeats, but the majority of transcriptomic changes are due to somatic repeat expansion. Our analysis reveals 479 genes with expression levels highly correlated with modal-CAG length in MSNs. Thus, our study mechanistically connects HD GWAS genes to selective neuronal vulnerability in HD, in which Msh3 and Pms1 set the linear rate of neuronal mHtt CAG-repeat migration to drive repeat-length dependent pathogenesis; and provides a preclinical platform for targeting these genes for HD suppression across brain regions. One Sentence Summary Msh3 and Pms1 are genetic drivers of sequential striatal and cortical pathogenesis in Q140 mice by mediating selective CAG-repeat migration in HD vulnerable neurons.
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Drobotenko MI, Lyasota OM, Hernandez-Caceres JL, Labrada RR, Svidlov AA, Dorohova АA, Baryshev MG, Nechipurenko YD, Pérez LV, Dzhimak SS. Abnormal open states patterns in the ATXN2 DNA sequence depends on the CAG repeats length. Int J Biol Macromol 2024; 276:133849. [PMID: 39004246 DOI: 10.1016/j.ijbiomac.2024.133849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 05/04/2024] [Accepted: 07/11/2024] [Indexed: 07/16/2024]
Abstract
Hereditary ataxias are one of the «anticipation diseases» types. Spinocerebral ataxia type 2 occurs when the number of CAG repeats in the coding region of the ATXN2 gene exceeds 34 or more. In healthy people, the CAG repeat region in the ATXN2 gene usually consists of 22-23 CAG trinucleotides. Mutations that increase the length of CAG repeats can cause severe neurodegenerative and neuromuscular disorders known as trinucleotide repeat expansion diseases. The mechanisms causing such diseases are associated with non-canonical configurations that can be formed in the CAG repeat region during replication, transcription or repair. This makes it relevant to study the zones of open states that arise in the region of CAG repeats under torque. The purpose of this work is to study, using mathematical modeling, zones of open states in the region of CAG repeats of the ATXN2 gene, caused by torque. It has been established that the torque effect on the 1st exon of the ATXN2 gene, in addition to the formation of open states in the promoter region, can lead to the formation of additional various sizes open states zones in the CAG repeats region. Moreover, the frequency of additional large zones genesis increases with increasing number of CAG repeats. The inverse of this frequency correlates with the dependence of the disease onset average age on the CAG repeats length. The obtained results will allow us to get closer to understanding the genetic mechanisms that cause trinucleotide repeat diseases.
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Affiliation(s)
- Mikhail I Drobotenko
- Department of Radiophysics and Nanothechnology, Kuban State University, 350040 Krasnodar, Russian Federation
| | - Oksana M Lyasota
- Laboratory of Problems of Stable Isotope Spreading in Living Systems, Southern Scientific Center of the Russian Academy of Sciences, 344006 Rostov-on-Don, Russian Federation
| | | | | | - Alexandr A Svidlov
- Laboratory of Problems of Stable Isotope Spreading in Living Systems, Southern Scientific Center of the Russian Academy of Sciences, 344006 Rostov-on-Don, Russian Federation
| | - Аnna A Dorohova
- Department of Radiophysics and Nanothechnology, Kuban State University, 350040 Krasnodar, Russian Federation; Laboratory of Problems of Stable Isotope Spreading in Living Systems, Southern Scientific Center of the Russian Academy of Sciences, 344006 Rostov-on-Don, Russian Federation
| | - Mikhail G Baryshev
- Laboratory of Problems of Stable Isotope Spreading in Living Systems, Southern Scientific Center of the Russian Academy of Sciences, 344006 Rostov-on-Don, Russian Federation
| | - Yury D Nechipurenko
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russian Federation
| | | | - Stepan S Dzhimak
- Department of Radiophysics and Nanothechnology, Kuban State University, 350040 Krasnodar, Russian Federation; Laboratory of Problems of Stable Isotope Spreading in Living Systems, Southern Scientific Center of the Russian Academy of Sciences, 344006 Rostov-on-Don, Russian Federation.
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3
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Pellerin D, Méreaux JL, Boluda S, Danzi MC, Dicaire MJ, Davoine CS, Genis D, Spurdens G, Ashton C, Hammond JM, Gerhart BJ, Chelban V, Le PU, Safisamghabadi M, Yanick C, Lee H, Nageshwaran SK, Matos-Rodrigues G, Jaunmuktane Z, Petrecca K, Akbarian S, Nussenzweig A, Usdin K, Renaud M, Bonnet C, Ravenscroft G, Saporta MA, Napierala JS, Houlden H, Deveson IW, Napierala M, Brice A, Molina Porcel L, Seilhean D, Zuchner S, Durr A, Brais B. Somatic instability of the FGF14 -SCA27B GAA•TTC repeat reveals a marked expansion bias in the cerebellum. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.07.01.24309777. [PMID: 39006414 PMCID: PMC11245061 DOI: 10.1101/2024.07.01.24309777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Spinocerebellar ataxia 27B (SCA27B) is a common autosomal dominant ataxia caused by an intronic GAA•TTC repeat expansion in FGF14 . Neuropathological studies have shown that neuronal loss is largely restricted to the cerebellum. Although the repeat locus is highly unstable during intergenerational transmission, it remains unknown whether it exhibits cerebral mosaicism and progressive instability throughout life. We conducted an analysis of the FGF14 GAA•TTC repeat somatic instability across 156 serial blood samples from 69 individuals, fibroblasts, induced pluripotent stem cells, and post-mortem brain tissues from six controls and six patients with SCA27B, alongside methylation profiling using targeted long-read sequencing. Peripheral tissues exhibited minimal somatic instability, which did not significantly change over periods of more than 20 years. In post-mortem brains, the GAA•TTC repeat was remarkably stable across all regions, except in the cerebellar hemispheres and vermis. The levels of somatic expansion in the cerebellar hemispheres and vermis were, on average, 3.15 and 2.72 times greater relative to other examined brain regions, respectively. Additionally, levels of somatic expansion in the brain increased with repeat length and tissue expression of FGF14 . We found no significant difference in methylation of wild-type and expanded FGF14 alleles in post-mortem cerebellar hemispheres between patients and controls. In conclusion, our study revealed that the FGF14 GAA•TTC repeat exhibits a cerebellar-specific expansion bias, which may explain the pure and late-onset cerebellar involvement in SCA27B.
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Mroczek M. Comment on: "Somatic CAG repeat instability in intermediate alleles of the HTT gene and its potential association with a clinical phenotype" by Ruiz de Sabando et al. Eur J Hum Genet 2024; 32:745-746. [PMID: 38448560 PMCID: PMC11219756 DOI: 10.1038/s41431-024-01587-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 02/28/2024] [Indexed: 03/08/2024] Open
Affiliation(s)
- Magdalena Mroczek
- Department of Neurology, University Hospital Basel, University of Basel, Basel, Switzerland.
- European Society of Human Genetics-Young Committee, Vienna, Austria.
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5
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Ruiz de Sabando A, Ciosi M, Galbete A, Cumming SA, Monckton DG, Ramos-Arroyo MA. Somatic CAG repeat instability in intermediate alleles of the HTT gene and its potential association with a clinical phenotype. Eur J Hum Genet 2024; 32:770-778. [PMID: 38433266 PMCID: PMC11220145 DOI: 10.1038/s41431-024-01546-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 01/08/2024] [Accepted: 01/17/2024] [Indexed: 03/05/2024] Open
Abstract
Huntington disease (HD) is a neurodegenerative disorder caused by ≥36 CAGs in the HTT gene. Intermediate alleles (IAs) (27-35 CAGs) are not considered HD-causing, but their potential association with neurocognitive symptoms remains controversial. As HTT somatic CAG expansion influences HD onset, we hypothesised that IAs are somatically unstable, and that somatic CAG expansion may drive phenotypic presentation in some IA carriers. We quantified HTT somatic CAG expansions by MiSeq sequencing in the blood DNA of 164 HD subjects and 191 IA (symptomatic and control) carriers, and in the brain DNA of a symptomatic 33 CAG carrier. We also performed genotype-phenotype analysis. The phenotype of symptomatic IA carriers was characterised by motor (85%), cognitive (27%) and/or behavioural (29%) signs, with a late (58.7 ± 18.6 years), but not CAG-dependent, age at onset. IAs displayed somatic expansion that were CAG and age-dependent in blood DNA, with 0.4% and 0.01% of DNA molecules expanding by CAG and year, respectively. Somatic expansions of +1 and +2 CAGs were detected in the brain of the individual with 33 CAGs, with the highest expansion frequency in the putamen (10.3%) and the lowest in the cerebellum (4.8%). Somatic expansion in blood DNA was not different in symptomatic vs. control IA carriers. In conclusion, we show that HTT IAs are somatically unstable, but we found no association with HD-like phenotypes. It is plausible, however, that some IAs, close to the HD pathological threshold and with a predisposing genetic background, could manifest with neurocognitive symptoms.
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Affiliation(s)
- Ainara Ruiz de Sabando
- Department of Medical Genetics, Hospital Universitario de Navarra, IdiSNA, 31008, Pamplona, Spain
- Department of Health Sciences, Universidad Pública de Navarra, IdiSNA, 31008, Pamplona, Spain
- Fundación Miguel Servet-Navarrabiomed, IdiSNA, 31008, Pamplona, Spain
| | - Marc Ciosi
- School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Arkaitz Galbete
- Department of Statistics, Informatics and Mathematics, Universidad Pública de Navarra, IdiSNA, 31006, Pamplona, Spain
| | - Sarah A Cumming
- School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Darren G Monckton
- School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Maria A Ramos-Arroyo
- Department of Medical Genetics, Hospital Universitario de Navarra, IdiSNA, 31008, Pamplona, Spain.
- Fundación Miguel Servet-Navarrabiomed, IdiSNA, 31008, Pamplona, Spain.
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Pengo M, Squitieri F. Beyond CAG Repeats: The Multifaceted Role of Genetics in Huntington Disease. Genes (Basel) 2024; 15:807. [PMID: 38927742 PMCID: PMC11203031 DOI: 10.3390/genes15060807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Revised: 06/11/2024] [Accepted: 06/18/2024] [Indexed: 06/28/2024] Open
Abstract
Huntington disease (HD) is a dominantly inherited neurodegenerative disorder caused by a CAG expansion on the huntingtin (HTT) gene and is characterized by progressive motor, cognitive, and neuropsychiatric decline. Recently, new genetic factors besides CAG repeats have been implicated in the disease pathogenesis. Most genetic modifiers are involved in DNA repair pathways and, as the cause of the loss of CAA interruption in the HTT gene, they exert their main influence through somatic expansion. However, this mechanism might not be the only driver of HD pathogenesis, and future studies are warranted in this field. The aim of the present review is to dissect the many faces of genetics in HD pathogenesis, from cis- and trans-acting genetic modifiers to RNA toxicity, mitochondrial DNA mutations, and epigenetics factors. Exploring genetic modifiers of HD onset and progression appears crucial to elucidate not only disease pathogenesis, but also to improve disease prediction and prevention, develop biomarkers of disease progression and response to therapies, and recognize new therapeutic opportunities. Since the same genetic mechanisms are also described in other repeat expansion diseases, their implications might encompass the whole spectrum of these disorders.
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Affiliation(s)
- Marta Pengo
- Department of Molecular and Translational Medicine, University of Brescia, 25121 Brescia, Italy;
| | - Ferdinando Squitieri
- Centre for Neurological Rare Diseases (CMNR), Fondazione Lega Italiana Ricerca Huntington (LIRH), 00161 Rome, Italy
- Huntington and Rare Diseases Unit, IRCCS Casa Sollievo della Sofferenza, 71013 San Giovanni Rotondo, Italy
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7
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Choi DE, Shin JW, Zeng S, Hong EP, Jang JH, Loupe JM, Wheeler VC, Stutzman HE, Kleinstiver B, Lee JM. Base editing strategies to convert CAG to CAA diminish the disease-causing mutation in Huntington's disease. eLife 2024; 12:RP89782. [PMID: 38869243 PMCID: PMC11175616 DOI: 10.7554/elife.89782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2024] Open
Abstract
An expanded CAG repeat in the huntingtin gene (HTT) causes Huntington's disease (HD). Since the length of uninterrupted CAG repeat, not polyglutamine, determines the age-at-onset in HD, base editing strategies to convert CAG to CAA are anticipated to delay onset by shortening the uninterrupted CAG repeat. Here, we developed base editing strategies to convert CAG in the repeat to CAA and determined their molecular outcomes and effects on relevant disease phenotypes. Base editing strategies employing combinations of cytosine base editors and guide RNAs (gRNAs) efficiently converted CAG to CAA at various sites in the CAG repeat without generating significant indels, off-target edits, or transcriptome alterations, demonstrating their feasibility and specificity. Candidate BE strategies converted CAG to CAA on both expanded and non-expanded CAG repeats without altering HTT mRNA and protein levels. In addition, somatic CAG repeat expansion, which is the major disease driver in HD, was significantly decreased in the liver by a candidate BE strategy treatment in HD knock-in mice carrying canonical CAG repeats. Notably, CAG repeat expansion was abolished entirely in HD knock-in mice carrying CAA-interrupted repeats, supporting the therapeutic potential of CAG-to-CAA conversion strategies in HD and potentially other repeat expansion disorders.
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Affiliation(s)
- Doo Eun Choi
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Neurology, Harvard Medical SchoolBostonUnited States
| | - Jun Wan Shin
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Neurology, Harvard Medical SchoolBostonUnited States
| | - Sophia Zeng
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
| | - Eun Pyo Hong
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Neurology, Harvard Medical SchoolBostonUnited States
- Medical and Population Genetics Program, The Broad Institute of MIT and HarvardCambridgeUnited States
| | - Jae-Hyun Jang
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Neurology, Harvard Medical SchoolBostonUnited States
| | - Jacob M Loupe
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Neurology, Harvard Medical SchoolBostonUnited States
| | - Vanessa C Wheeler
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Neurology, Harvard Medical SchoolBostonUnited States
| | - Hannah E Stutzman
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Pathology, Massachusetts General HospitalBostonUnited States
| | - Ben Kleinstiver
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Pathology, Massachusetts General HospitalBostonUnited States
- Department of Pathology, Harvard Medical SchoolBostonUnited States
| | - Jong-Min Lee
- Center for Genomic Medicine, Massachusetts General HospitalBostonUnited States
- Department of Neurology, Harvard Medical SchoolBostonUnited States
- Medical and Population Genetics Program, The Broad Institute of MIT and HarvardCambridgeUnited States
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8
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Kacher R, Lejeune FX, David I, Boluda S, Coarelli G, Leclere-Turbant S, Heinzmann A, Marelli C, Charles P, Goizet C, Kabir N, Hilab R, Jornea L, Six J, Dommergues M, Fauret AL, Brice A, Humbert S, Durr A. CAG repeat mosaicism is gene specific in spinocerebellar ataxias. Am J Hum Genet 2024; 111:913-926. [PMID: 38626762 PMCID: PMC11080609 DOI: 10.1016/j.ajhg.2024.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 03/25/2024] [Accepted: 03/25/2024] [Indexed: 04/18/2024] Open
Abstract
Expanded CAG repeats in coding regions of different genes are the most common cause of dominantly inherited spinocerebellar ataxias (SCAs). These repeats are unstable through the germline, and larger repeats lead to earlier onset. We measured somatic expansion in blood samples collected from 30 SCA1, 50 SCA2, 74 SCA3, and 30 SCA7 individuals over a mean interval of 8.5 years, along with postmortem tissues and fetal tissues from SCA1, SCA3, and SCA7 individuals to examine somatic expansion at different stages of life. We showed that somatic mosaicism in the blood increases over time. Expansion levels are significantly different among SCAs and correlate with CAG repeat lengths. The level of expansion is greater in individuals with SCA7 who manifest disease compared to that of those who do not yet display symptoms. Brain tissues from SCA individuals have larger expansions compared to the blood. The cerebellum has the lowest mosaicism among the studied brain regions, along with a high expression of ATXNs and DNA repair genes. This was the opposite in cortices, with the highest mosaicism and lower expression of ATXNs and DNA repair genes. Fetal cortices did not show repeat instability. This study shows that CAG repeats are increasingly unstable during life in the blood and the brain of SCA individuals, with gene- and tissue-specific patterns.
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Affiliation(s)
- Radhia Kacher
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - François-Xavier Lejeune
- Sorbonne Université, Paris Brain Institute's Data Analysis Core Facility, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Isabelle David
- Sorbonne Université, Department of Genetics, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Susana Boluda
- Sorbonne Université, Department of Neuropathology Raymond Escourolle, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Giulia Coarelli
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Sabrina Leclere-Turbant
- Sorbonne Université, Biobank Neuro-CEB Biological Resource Platform, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Anna Heinzmann
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Cecilia Marelli
- MMDN, Université Montpellier, EPHE, INSERM, Montpellier, France; Expert Center for Neurogenetic Diseases, CHU, Montpellier, France
| | - Perrine Charles
- Sorbonne Université, Department of Genetics, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Cyril Goizet
- Université Bordeaux, Equipe « Neurogénétique Translationnelle - NRGEN », INCIA CNRS UMR5287 Université Bordeaux and Centre de Reference Maladies Rares « Neurogénétique », Service de Génétique Médicale, Bordeaux University Hospital (CHU Bordeaux), Bordeaux, France
| | - Nisha Kabir
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Rania Hilab
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Ludmila Jornea
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Julie Six
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Marc Dommergues
- Sorbonne Université, Service de Gynécologie Obstetrique, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Anne-Laure Fauret
- Sorbonne Université, Department of Genetics, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Alexis Brice
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Sandrine Humbert
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Alexandra Durr
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France.
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9
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Sampaio C. Huntington disease - Update on ongoing therapeutic developments and a look toward the future. Parkinsonism Relat Disord 2024; 122:106049. [PMID: 38418319 DOI: 10.1016/j.parkreldis.2024.106049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2024] [Accepted: 02/12/2024] [Indexed: 03/01/2024]
Affiliation(s)
- Cristina Sampaio
- CHDI Management, Inc. Advisors to CHDI Foundation, Princeton, USA; Faculdade Medicina da Universidade de Lisboa (FMUL), Portugal.
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10
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McLean ZL, Gao D, Correia K, Roy JCL, Shibata S, Farnum IN, Valdepenas-Mellor Z, Kovalenko M, Rapuru M, Morini E, Ruliera J, Gillis T, Lucente D, Kleinstiver BP, Lee JM, MacDonald ME, Wheeler VC, Mouro Pinto R, Gusella JF. Splice modulators target PMS1 to reduce somatic expansion of the Huntington's disease-associated CAG repeat. Nat Commun 2024; 15:3182. [PMID: 38609352 PMCID: PMC11015039 DOI: 10.1038/s41467-024-47485-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 03/30/2024] [Indexed: 04/14/2024] Open
Abstract
Huntington's disease (HD) is a dominant neurological disorder caused by an expanded HTT exon 1 CAG repeat that lengthens huntingtin's polyglutamine tract. Lowering mutant huntingtin has been proposed for treating HD, but genetic modifiers implicate somatic CAG repeat expansion as the driver of onset. We find that branaplam and risdiplam, small molecule splice modulators that lower huntingtin by promoting HTT pseudoexon inclusion, also decrease expansion of an unstable HTT exon 1 CAG repeat in an engineered cell model. Targeted CRISPR-Cas9 editing shows this effect is not due to huntingtin lowering, pointing instead to pseudoexon inclusion in PMS1. Homozygous but not heterozygous inactivation of PMS1 also reduces CAG repeat expansion, supporting PMS1 as a genetic modifier of HD and a potential target for therapeutic intervention. Although splice modulation provides one strategy, genome-wide transcriptomics also emphasize consideration of cell-type specific effects and polymorphic variation at both target and off-target sites.
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Affiliation(s)
- Zachariah L McLean
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA
| | - Dadi Gao
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA
| | - Kevin Correia
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Jennie C L Roy
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
| | - Shota Shibata
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA
| | - Iris N Farnum
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Zoe Valdepenas-Mellor
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Marina Kovalenko
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Manasa Rapuru
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Elisabetta Morini
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
| | - Jayla Ruliera
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Tammy Gillis
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Diane Lucente
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Benjamin P Kleinstiver
- Center for Genomic Medicine and Department of Pathology, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Pathology, Harvard Medical School, Boston, MA, 02115, USA
| | - Jong-Min Lee
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA
| | - Marcy E MacDonald
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA
| | - Vanessa C Wheeler
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA
| | - Ricardo Mouro Pinto
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA
| | - James F Gusella
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA.
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA.
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, 02115, USA.
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11
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Pressl C, Mätlik K, Kus L, Darnell P, Luo JD, Paul MR, Weiss AR, Liguore W, Carroll TS, Davis DA, McBride J, Heintz N. Selective vulnerability of layer 5a corticostriatal neurons in Huntington's disease. Neuron 2024; 112:924-941.e10. [PMID: 38237588 DOI: 10.1016/j.neuron.2023.12.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 08/18/2023] [Accepted: 12/13/2023] [Indexed: 01/30/2024]
Abstract
The properties of the cell types that are selectively vulnerable in Huntington's disease (HD) cortex, the nature of somatic CAG expansions of mHTT in these cells, and their importance in CNS circuitry have not been delineated. Here, we employed serial fluorescence-activated nuclear sorting (sFANS), deep molecular profiling, and single-nucleus RNA sequencing (snRNA-seq) of motor-cortex samples from thirteen predominantly early stage, clinically diagnosed HD donors and selected samples from cingulate, visual, insular, and prefrontal cortices to demonstrate loss of layer 5a pyramidal neurons in HD. Extensive mHTT CAG expansions occur in vulnerable layer 5a pyramidal cells, and in Betz cells, layers 6a and 6b neurons that are resilient in HD. Retrograde tracing experiments in macaque brains identify layer 5a neurons as corticostriatal pyramidal cells. We propose that enhanced somatic mHTT CAG expansion and altered synaptic function act together to cause corticostriatal disconnection and selective neuronal vulnerability in HD cerebral cortex.
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Affiliation(s)
- Christina Pressl
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA
| | - Kert Mätlik
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA
| | - Laura Kus
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA
| | - Paul Darnell
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA
| | - Ji-Dung Luo
- Bioinformatics Resource Center, The Rockefeller University, New York, NY, USA
| | - Matthew R Paul
- Bioinformatics Resource Center, The Rockefeller University, New York, NY, USA
| | - Alison R Weiss
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, USA
| | - William Liguore
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, USA
| | - Thomas S Carroll
- Bioinformatics Resource Center, The Rockefeller University, New York, NY, USA
| | - David A Davis
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Jodi McBride
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, USA
| | - Nathaniel Heintz
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA.
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12
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Mätlik K, Baffuto M, Kus L, Deshmukh AL, Davis DA, Paul MR, Carroll TS, Caron MC, Masson JY, Pearson CE, Heintz N. Cell-type-specific CAG repeat expansions and toxicity of mutant Huntingtin in human striatum and cerebellum. Nat Genet 2024; 56:383-394. [PMID: 38291334 PMCID: PMC10937393 DOI: 10.1038/s41588-024-01653-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 12/28/2023] [Indexed: 02/01/2024]
Abstract
Brain region-specific degeneration and somatic expansions of the mutant Huntingtin (mHTT) CAG tract are key features of Huntington's disease (HD). However, the relationships among CAG expansions, death of specific cell types and molecular events associated with these processes are not established. Here, we used fluorescence-activated nuclear sorting (FANS) and deep molecular profiling to gain insight into the properties of cell types of the human striatum and cerebellum in HD and control donors. CAG expansions arise at mHTT in striatal medium spiny neurons (MSNs), cholinergic interneurons and cerebellar Purkinje neurons, and at mutant ATXN3 in MSNs from SCA3 donors. CAG expansions in MSNs are associated with higher levels of MSH2 and MSH3 (forming MutSβ), which can inhibit nucleolytic excision of CAG slip-outs by FAN1. Our data support a model in which CAG expansions are necessary but may not be sufficient for cell death and identify transcriptional changes associated with somatic CAG expansions and striatal toxicity.
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Affiliation(s)
- Kert Mätlik
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA
| | - Matthew Baffuto
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA
| | - Laura Kus
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA
| | - Amit Laxmikant Deshmukh
- Program of Genetics & Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - David A Davis
- Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Matthew R Paul
- Bioinformatics Resource Center, The Rockefeller University, New York, NY, USA
| | - Thomas S Carroll
- Bioinformatics Resource Center, The Rockefeller University, New York, NY, USA
| | - Marie-Christine Caron
- CHU de Québec Research Center, Oncology Division, Laval University Cancer Research Center, Quebec City, Quebec, Canada
| | - Jean-Yves Masson
- CHU de Québec Research Center, Oncology Division, Laval University Cancer Research Center, Quebec City, Quebec, Canada
| | - Christopher E Pearson
- Program of Genetics & Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Nathaniel Heintz
- Laboratory of Molecular Biology, The Rockefeller University, New York, NY, USA.
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13
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Hobbs NZ, Papoutsi M, Delva A, Kinnunen KM, Nakajima M, Van Laere K, Vandenberghe W, Herath P, Scahill RI. Neuroimaging to Facilitate Clinical Trials in Huntington's Disease: Current Opinion from the EHDN Imaging Working Group. J Huntingtons Dis 2024; 13:163-199. [PMID: 38788082 DOI: 10.3233/jhd-240016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2024]
Abstract
Neuroimaging is increasingly being included in clinical trials of Huntington's disease (HD) for a wide range of purposes from participant selection and safety monitoring, through to demonstration of disease modification. Selection of the appropriate modality and associated analysis tools requires careful consideration. On behalf of the EHDN Imaging Working Group, we present current opinion on the utility and future prospects for inclusion of neuroimaging in HD trials. Covering the key imaging modalities of structural-, functional- and diffusion- MRI, perfusion imaging, positron emission tomography, magnetic resonance spectroscopy, and magnetoencephalography, we address how neuroimaging can be used in HD trials to: 1) Aid patient selection, enrichment, stratification, and safety monitoring; 2) Demonstrate biodistribution, target engagement, and pharmacodynamics; 3) Provide evidence for disease modification; and 4) Understand brain re-organization following therapy. We also present the challenges of translating research methodology into clinical trial settings, including equipment requirements and cost, standardization of acquisition and analysis, patient burden and invasiveness, and interpretation of results. We conclude, that with appropriate consideration of modality, study design and analysis, imaging has huge potential to facilitate effective clinical trials in HD.
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Affiliation(s)
- Nicola Z Hobbs
- HD Research Centre, UCL Institute of Neurology, UCL, London, UK
| | - Marina Papoutsi
- HD Research Centre, UCL Institute of Neurology, UCL, London, UK
- IXICO plc, London, UK
| | - Aline Delva
- Department of Neurosciences, KU Leuven, Belgium
- Department of Neurology, University Hospitals Leuven, Belgium
| | | | | | - Koen Van Laere
- Department of Imaging and Pathology, Nuclear Medicine and Molecular Imaging, KU Leuven, Belgium
- Division of Nuclear Medicine, University Hospitals Leuven, Belgium
| | - Wim Vandenberghe
- Department of Neurosciences, KU Leuven, Belgium
- Department of Neurology, University Hospitals Leuven, Belgium
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14
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Rajagopal S, Donaldson J, Flower M, Hensman Moss DJ, Tabrizi SJ. Genetic modifiers of repeat expansion disorders. Emerg Top Life Sci 2023; 7:325-337. [PMID: 37861103 PMCID: PMC10754329 DOI: 10.1042/etls20230015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 09/20/2023] [Accepted: 10/09/2023] [Indexed: 10/21/2023]
Abstract
Repeat expansion disorders (REDs) are monogenic diseases caused by a sequence of repetitive DNA expanding above a pathogenic threshold. A common feature of the REDs is a strong genotype-phenotype correlation in which a major determinant of age at onset (AAO) and disease progression is the length of the inherited repeat tract. Over a disease-gene carrier's life, the length of the repeat can expand in somatic cells, through the process of somatic expansion which is hypothesised to drive disease progression. Despite being monogenic, individual REDs are phenotypically variable, and exploring what genetic modifying factors drive this phenotypic variability has illuminated key pathogenic mechanisms that are common to this group of diseases. Disease phenotypes are affected by the cognate gene in which the expansion is found, the location of the repeat sequence in coding or non-coding regions and by the presence of repeat sequence interruptions. Human genetic data, mouse models and in vitro models have implicated the disease-modifying effect of DNA repair pathways via the mechanisms of somatic mutation of the repeat tract. As such, developing an understanding of these pathways in the context of expanded repeats could lead to future disease-modifying therapies for REDs.
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Affiliation(s)
- Sangeerthana Rajagopal
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, U.K
- UK Dementia Research Institute, University College London, London WCC1N 3BG, U.K
| | - Jasmine Donaldson
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, U.K
- UK Dementia Research Institute, University College London, London WCC1N 3BG, U.K
| | - Michael Flower
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, U.K
- UK Dementia Research Institute, University College London, London WCC1N 3BG, U.K
| | - Davina J Hensman Moss
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, U.K
- UK Dementia Research Institute, University College London, London WCC1N 3BG, U.K
- St George's University of London, London SW17 0RE, U.K
| | - Sarah J Tabrizi
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, U.K
- UK Dementia Research Institute, University College London, London WCC1N 3BG, U.K
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15
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Tano V, Utami KH, Yusof NABM, Bégin J, Tan WWL, Pouladi MA, Langley SR. Widespread dysregulation of mRNA splicing implicates RNA processing in the development and progression of Huntington's disease. EBioMedicine 2023; 94:104720. [PMID: 37481821 PMCID: PMC10393612 DOI: 10.1016/j.ebiom.2023.104720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 07/03/2023] [Accepted: 07/03/2023] [Indexed: 07/25/2023] Open
Abstract
BACKGROUND In Huntington's disease (HD), a CAG repeat expansion mutation in the Huntingtin (HTT) gene drives a gain-of-function toxicity that disrupts mRNA processing. Although dysregulation of gene splicing has been shown in human HD post-mortem brain tissue, post-mortem analyses are likely confounded by cell type composition changes in late-stage HD, limiting the ability to identify dysregulation related to early pathogenesis. METHODS To investigate gene splicing changes in early HD, we performed alternative splicing analyses coupled with a proteogenomics approach to identify early CAG length-associated splicing changes in an established isogenic HD cell model. FINDINGS We report widespread neuronal differentiation stage- and CAG length-dependent splicing changes, and find an enrichment of RNA processing, neuronal function, and epigenetic modification-related genes with mutant HTT-associated splicing. When integrated with a proteomics dataset, we identified several of these differential splicing events at the protein level. By comparing with human post-mortem and mouse model data, we identified common patterns of altered splicing from embryonic stem cells through to post-mortem striatal tissue. INTERPRETATION We show that widespread splicing dysregulation in HD occurs in an early cell model of neuronal development. Importantly, we observe HD-associated splicing changes in our HD cell model that were also identified in human HD striatum and mouse model HD striatum, suggesting that splicing-associated pathogenesis possibly occurs early in neuronal development and persists to later stages of disease. Together, our results highlight splicing dysregulation in HD which may lead to disrupted neuronal function and neuropathology. FUNDING This research is supported by the Lee Kong Chian School of Medicine, Nanyang Technological University Singapore Nanyang Assistant Professorship Start-Up Grant, the Singapore Ministry of Education under its Singapore Ministry of Education Academic Research Fund Tier 1 (RG23/22), the BC Children's Hospital Research Institute Investigator Grant Award (IGAP), and a Scholar Award from the Michael Smith Health Research BC.
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Affiliation(s)
- Vincent Tano
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 636921, Singapore
| | - Kagistia Hana Utami
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 636921, Singapore; Translational Laboratory in Genetic Medicine (TLGM), Agency for Science, Technology and Research (A∗STAR), Singapore 138648, Singapore
| | - Nur Amirah Binte Mohammad Yusof
- Translational Laboratory in Genetic Medicine (TLGM), Agency for Science, Technology and Research (A∗STAR), Singapore 138648, Singapore
| | - Jocelyn Bégin
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, British Columbia Children's Hospital Research Institute, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Willy Wei Li Tan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 636921, Singapore
| | - Mahmoud A Pouladi
- Translational Laboratory in Genetic Medicine (TLGM), Agency for Science, Technology and Research (A∗STAR), Singapore 138648, Singapore; Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, British Columbia Children's Hospital Research Institute, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Sarah R Langley
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 636921, Singapore.
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16
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McLean ZL, Gao D, Correia K, Roy JCL, Shibata S, Farnum IN, Valdepenas-Mellor Z, Rapuru M, Morini E, Ruliera J, Gillis T, Lucente D, Kleinstiver BP, Lee JM, MacDonald ME, Wheeler VC, Pinto RM, Gusella JF. PMS1 as a target for splice modulation to prevent somatic CAG repeat expansion in Huntington's disease. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.25.550489. [PMID: 37547003 PMCID: PMC10402039 DOI: 10.1101/2023.07.25.550489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Huntington's disease (HD) is a dominantly inherited neurodegenerative disorder whose motor, cognitive, and behavioral manifestations are caused by an expanded, somatically unstable CAG repeat in the first exon of HTT that lengthens a polyglutamine tract in huntingtin. Genome-wide association studies (GWAS) have revealed DNA repair genes that influence the age-at-onset of HD and implicate somatic CAG repeat expansion as the primary driver of disease timing. To prevent the consequent neuronal damage, small molecule splice modulators (e.g., branaplam) that target HTT to reduce the levels of huntingtin are being investigated as potential HD therapeutics. We found that the effectiveness of the splice modulators can be influenced by genetic variants, both at HTT and other genes where they promote pseudoexon inclusion. Surprisingly, in a novel hTERT-immortalized retinal pigment epithelial cell (RPE1) model for assessing CAG repeat instability, these drugs also reduced the rate of HTT CAG expansion. We determined that the splice modulators also affect the expression of the mismatch repair gene PMS1, a known modifier of HD age-at-onset. Genome editing at specific HTT and PMS1 sequences using CRISPR-Cas9 nuclease confirmed that branaplam suppresses CAG expansion by promoting the inclusion of a pseudoexon in PMS1, making splice modulation of PMS1 a potential strategy for delaying HD onset. Comparison with another splice modulator, risdiplam, suggests that other genes affected by these splice modulators also influence CAG instability and might provide additional therapeutic targets.
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Affiliation(s)
- Zachariah L. McLean
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
| | - Dadi Gao
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
| | - Kevin Correia
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Jennie C. L. Roy
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Shota Shibata
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
| | - Iris N. Farnum
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Zoe Valdepenas-Mellor
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Manasa Rapuru
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Elisabetta Morini
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Jayla Ruliera
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Tammy Gillis
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Diane Lucente
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Benjamin P. Kleinstiver
- Center for Genomic Medicine and Department of Pathology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
| | - Jong-Min Lee
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
| | - Marcy E. MacDonald
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
| | - Vanessa C. Wheeler
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Ricardo Mouro Pinto
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
| | - James F. Gusella
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
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17
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Choi DE, Shin JW, Zeng S, Hong EP, Jang JH, Loupe JM, Wheeler VC, Stutzman HE, Kleinstiver BP, Lee JM. Base editing strategies to convert CAG to CAA diminish the disease-causing mutation in Huntington's disease. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.28.538700. [PMID: 37162872 PMCID: PMC10168301 DOI: 10.1101/2023.04.28.538700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
An expanded CAG repeat in the huntingtin gene ( HTT ) causes Huntington's disease (HD). Since the length of uninterrupted CAG repeat, not polyglutamine, determines the age-at-onset in HD, base editing strategies to convert CAG to CAA are anticipated to delay onset by shortening the uninterrupted CAG repeat. Here, we developed base editing strategies to convert CAG in the repeat to CAA and determined their molecular outcomes and effects on relevant disease phenotypes. Base editing strategies employing combinations of cytosine base editors and gRNAs efficiently converted CAG to CAA at various sites in the CAG repeat without generating significant indels, off-target edits, or transcriptome alterations, demonstrating their feasibility and specificity. Candidate BE strategies converted CAG to CAA on both expanded and non-expanded CAG repeats without altering HTT mRNA and protein levels. In addition, somatic CAG repeat expansion, which is the major disease driver in HD, was significantly decreased by a candidate BE strategy treatment in HD knock-in mice carrying canonical CAG repeats. Notably, CAG repeat expansion was abolished entirely in HD knock-in mice carrying CAA-interrupted repeats, supporting the therapeutic potential of CAG-to-CAA conversion base editing strategies in HD and potentially other repeat expansion disorders.
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18
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Zhang S, Cheng Y, Shang H. The updated development of blood-based biomarkers for Huntington's disease. J Neurol 2023; 270:2483-2503. [PMID: 36692635 PMCID: PMC9873222 DOI: 10.1007/s00415-023-11572-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 01/11/2023] [Accepted: 01/12/2023] [Indexed: 01/25/2023]
Abstract
Huntington's disease is a progressive neurodegenerative disease caused by mutation of the huntingtin (HTT) gene. The identification of mutation carriers before symptom onset provides an opportunity to intervene in the early stage of the disease course. Optimal biomarkers are of great value to reflect neuropathological and clinical progression and are sensitive to potential disease-modifying treatments. Blood-based biomarkers have the merits of minimal invasiveness, low cost, easy accessibility and safety. In this review, we summarized the updated development of blood-based biomarkers for HD from six aspects, including neuronal injuries, oxidative stress, endocrine functions, immune reactions, metabolism and differentially expressed miRNAs. The blood-based biomarkers presented and discussed in this review were close to clinical applicability and might facilitate clinical design as surrogate endpoints. Exploration and validation of robust blood-based biomarkers require further standard and systemic study design in the future.
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Affiliation(s)
- Sirui Zhang
- grid.412901.f0000 0004 1770 1022Laboratory of Neurodegenerative Disorders, Department of Neurology, Rare Disease Center, West China Hospital, Sichuan University, Chengdu, 610041 Sichuan China ,grid.412901.f0000 0004 1770 1022National Clinical Research Center for Geriatric, Laboratory of Neurodegenerative Disorders, West China Hospital, Sichuan University, Chengdu, 610041 China ,grid.412901.f0000 0004 1770 1022West China School of Medicine, West China Hospital, Sichuan University, Chengdu, 610041 China
| | - Yangfan Cheng
- grid.412901.f0000 0004 1770 1022Laboratory of Neurodegenerative Disorders, Department of Neurology, Rare Disease Center, West China Hospital, Sichuan University, Chengdu, 610041 Sichuan China ,grid.412901.f0000 0004 1770 1022National Clinical Research Center for Geriatric, Laboratory of Neurodegenerative Disorders, West China Hospital, Sichuan University, Chengdu, 610041 China
| | - Huifang Shang
- grid.412901.f0000 0004 1770 1022Laboratory of Neurodegenerative Disorders, Department of Neurology, Rare Disease Center, West China Hospital, Sichuan University, Chengdu, 610041 Sichuan China ,grid.412901.f0000 0004 1770 1022National Clinical Research Center for Geriatric, Laboratory of Neurodegenerative Disorders, West China Hospital, Sichuan University, Chengdu, 610041 China
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19
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Heterogeneous migration routes of DNA triplet repeat slip-outs. BIOPHYSICAL REPORTS 2022; 2:None. [PMID: 36299495 PMCID: PMC9586884 DOI: 10.1016/j.bpr.2022.100070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 08/08/2022] [Indexed: 12/02/2022]
Abstract
It is unclear how the length of a repetitive DNA tract determines the onset and progression of repeat expansion diseases, but the dynamics of secondary DNA structures formed by repeat sequences are believed to play an important role. It was recently shown that three-way DNA junctions containing slip-out hairpins of CAG or CTG repeats and contiguous triplet repeats in the adjacent duplex displayed single-molecule FRET (smFRET) dynamics that were ascribed to both local conformational motions and longer-range branch migration. Here we explore these so-called "mobile" slip-out structures through a detailed kinetic analysis of smFRET trajectories and coarse-grained modeling. Despite the apparent structural simplicity, with six FRET states resolvable, most smFRET states displayed biexponential dwell-time distributions, attributed to structural heterogeneity and overlapping FRET states. Coarse-grained modeling for a (GAC)10 repeat slip-out included trajectories that corresponded to a complete round of branch migration; the structured free energy landscape between slippage events supports the dynamical complexity observed by smFRET. A hairpin slip-out with 40 CAG repeats, which is above the repeat length required for disease in several triplet repeat disorders, displayed smFRET dwell times that were on average double those of 3WJs with 10 repeats. The rate of secondary-structure rearrangement via branch migration, relative to particular DNA processing pathways, may be an important factor in the expansion of triplet repeat expansion diseases.
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20
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Warner JH, Long JD, Mills JA, Langbehn DR, Ware J, Mohan A, Sampaio C. Standardizing the CAP Score in Huntington's Disease by Predicting Age-at-Onset. J Huntingtons Dis 2022; 11:153-171. [PMID: 35466943 DOI: 10.3233/jhd-210475] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Huntington's disease (HD) is an autosomal dominant, neurological disease caused by an expanded CAG repeat near the N-terminus of the huntingtin (HTT) gene. A leading theory concerning the etiology of HD is that both onset and progression are driven by cumulative exposure to the effects of mutant (or CAG expanded) huntingtin (mHTT). The CAG-Age-Product (CAP) score (i.e., the product of excess CAG length and age) is a commonly used measure of this cumulative exposure. CAP score has been widely used as a predictor of a variety of disease state variables in HD. The utility of the CAP score has been somewhat diminished, however, by a lack of agreement on its precise definition. The most commonly used forms of the CAP score are highly correlated so that, for purposes of prediction, it makes little difference which is used. However, reported values of CAP scores, based on commonly used definitions, differ substantially in magnitude when applied to the same data. This complicates the process of inter-study comparison. OBJECTIVE In this paper, we propose a standardized definition for the CAP score which will resolve this difficulty. Our standardization is chosen so that CAP = 100 at the expected age of diagnosis. METHODS Statistical methods include novel survival analysis methodology applied to the 13 disease landmarks taken from the Enroll-HD database (PDS 5) and comparisons with the existing, gold standard, onset model. RESULTS Useful by-products of our work include up-to-date, age-at-onset (AO) results and a refined AO model suitable for use in other contexts, a discussion of several useful properties of the CAP score that have not previously been noted in the literature and the introduction of the concept of a toxicity onset model. CONCLUSION We suggest that taking L = 30 and K = 6.49 provides a useful standardization of the CAP score, suitable for use in the routine modeling of clinical data in HD.
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Affiliation(s)
| | - Jeffrey D Long
- Departments of Psychiatry, Biostatistics, University of Iowa, Iowa City, IA, USA
| | - James A Mills
- Departments of Psychiatry, Biostatistics, University of Iowa, Iowa City, IA, USA
| | - Douglas R Langbehn
- Departments of Psychiatry, Biostatistics, University of Iowa, Iowa City, IA, USA
| | | | - Amrita Mohan
- CHDI Management/CHDI Foundation, Princeton, NJ, USA
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21
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Costa MD, Maciel P. Modifier pathways in polyglutamine (PolyQ) diseases: from genetic screens to drug targets. Cell Mol Life Sci 2022; 79:274. [PMID: 35503478 PMCID: PMC11071829 DOI: 10.1007/s00018-022-04280-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 03/14/2022] [Accepted: 03/30/2022] [Indexed: 12/17/2022]
Abstract
Polyglutamine (PolyQ) diseases include a group of inherited neurodegenerative disorders caused by unstable expansions of CAG trinucleotide repeats in the coding region of specific genes. Such genetic alterations produce abnormal proteins containing an unusually long PolyQ tract that renders them more prone to aggregate and cause toxicity. Although research in the field in the last years has contributed significantly to the knowledge of the biological mechanisms implicated in these diseases, effective treatments are still lacking. In this review, we revisit work performed in models of PolyQ diseases, namely the yeast Saccharomyces cerevisiae, the nematode worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster, and provide a critical overview of the high-throughput unbiased genetic screens that have been performed using these systems to identify novel genetic modifiers of PolyQ diseases. These approaches have revealed a wide variety of cellular processes that modulate the toxicity and aggregation of mutant PolyQ proteins, reflecting the complexity of these disorders and demonstrating how challenging the development of therapeutic strategies can be. In addition to the unbiased large-scale genetic screenings in non-vertebrate models, complementary studies in mammalian systems, closer to humans, have contributed with novel genetic modifiers of PolyQ diseases, revealing neuronal function and inflammation as key disease modulators. A pathway enrichment analysis, using the human orthologues of genetic modifiers of PolyQ diseases clustered modifier genes into major themes translatable to the human disease context, such as protein folding and transport as well as transcription regulation. Innovative genetic strategies of genetic manipulation, together with significant advances in genomics and bioinformatics, are taking modifier genetic studies to more realistic disease contexts. The characterization of PolyQ disease modifier pathways is of extreme relevance to reveal novel therapeutic possibilities to delay disease onset and progression in patients.
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Affiliation(s)
- Marta Daniela Costa
- School of Medicine, Life and Health Sciences Research Institute (ICVS), University of Minho, 4710-057, Braga, Portugal
- ICVS/3Bs-PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Patrícia Maciel
- School of Medicine, Life and Health Sciences Research Institute (ICVS), University of Minho, 4710-057, Braga, Portugal.
- ICVS/3Bs-PT Government Associate Laboratory, Braga/Guimarães, Portugal.
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22
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Sharma P, Sonakar AK, Tyagi N, Suroliya V, Kumar M, Kutum R, Asokchandran V, Ambawat S, Shamim U, Anand A, Ahmad I, Shakya S, Uppili B, Mathur A, Parveen S, Jain S, Singh J, Seth M, Zahra S, Joshi A, Goel D, Sahni S, Kamai A, Wadhwa S, Murali A, Saifi S, Chowdhury D, Pandey S, Anand KS, Narasimhan RL, Laskar S, Kushwaha S, Kumar M, Shaji CV, Srivastava MVP, Srivastava AK, Faruq M. Genetics of Ataxias in Indian Population: A Collative Insight from a Common Genetic Screening Tool. ADVANCED GENETICS (HOBOKEN, N.J.) 2022; 3:2100078. [PMID: 36618024 PMCID: PMC9744545 DOI: 10.1002/ggn2.202100078] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Indexed: 01/11/2023]
Abstract
Cerebellar ataxias (CAs) represent a group of autosomal dominant and recessive neurodegenerative disorders affecting cerebellum with or without spinal cord. Overall, CAs have preponderance for tandem nucleotide repeat expansions as an etiological factor (10 TREs explain nearly 30-40% of ataxia cohort globally). The experience of 10 years of common genetic ataxia subtypes for ≈5600 patients' referrals (Pan-India) received at a single center is shared herein. Frequencies (in %, n) of SCA types and FRDA in the sample cohort are observed as follows: SCA12 (8.6%, 490); SCA2 (8.5%, 482); SCA1 (4.8%, 272); SCA3 (2%, 113); SCA7 (0.5%, 28); SCA6 (0.1%, 05); SCA17 (0.1%, 05), and FRDA (2.2%, 127). A significant amount of variability in TRE lengths at each locus is observed, we noted presence of biallelic expansion, co-occurrence of SCA-subtypes, and the presence of premutable normal alleles. The frequency of mutated GAA-FRDA allele in healthy controls is 1/158 (0.63%), thus an expected FRDA prevalence of 1:100 000 persons. The data of this study are relevant not only for clinical decision making but also for guidance in direction of genetic investigations, transancestral comparison of genotypes, and lastly provide insight for policy decision for the consideration of SCAs under rare disease category.
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Affiliation(s)
- Pooja Sharma
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | | | - Nishu Tyagi
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Varun Suroliya
- Neurology DepartmentNeuroscience CentreNew Delhi110029India
| | - Manish Kumar
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Rintu Kutum
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Vivekananda Asokchandran
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Sakshi Ambawat
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Uzma Shamim
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Avni Anand
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Ishtaq Ahmad
- Neurology DepartmentNeuroscience CentreNew Delhi110029India
| | - Sunil Shakya
- Neurology DepartmentNeuroscience CentreNew Delhi110029India
| | - Bharathram Uppili
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Aradhana Mathur
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Shaista Parveen
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Shweta Jain
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Jyotsna Singh
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Neurology DepartmentNeuroscience CentreNew Delhi110029India
| | - Malika Seth
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Sana Zahra
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Aditi Joshi
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Divya Goel
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Shweta Sahni
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Asangla Kamai
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Saruchi Wadhwa
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Aparna Murali
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Sheeba Saifi
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | | | - Sanjay Pandey
- Department of NeurologyGB Pant HospitalDelhi110002India
| | - Kuljeet Singh Anand
- Department of NeurologyPost Graduate Institute of Medical Education and ResearchDr. Ram Manohar Lohia HospitalNew Delhi110001India
| | | | | | - Suman Kushwaha
- Department of NeurologyInstitute of Human Behaviour and Allied SciencesDelhi110095India
| | | | | | | | | | - Mohammed Faruq
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
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23
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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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24
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Mouro Pinto R, Arning L, Giordano JV, Razghandi P, Andrew MA, Gillis T, Correia K, Mysore JS, Grote Urtubey DM, Parwez CR, von Hein SM, Clark HB, Nguyen HP, Förster E, Beller A, Jayadaev S, Keene CD, Bird TD, Lucente D, Vonsattel JP, Orr H, Saft C, Petrasch-Parwez E, Wheeler VC. Patterns of CAG repeat instability in the central nervous system and periphery in Huntington's disease and in spinocerebellar ataxia type 1. Hum Mol Genet 2021; 29:2551-2567. [PMID: 32761094 PMCID: PMC7471505 DOI: 10.1093/hmg/ddaa139] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 06/24/2020] [Accepted: 07/01/2020] [Indexed: 12/23/2022] Open
Abstract
The expanded HTT CAG repeat causing Huntington’s disease (HD) exhibits somatic expansion proposed to drive the rate of disease onset by eliciting a pathological process that ultimately claims vulnerable cells. To gain insight into somatic expansion in humans, we performed comprehensive quantitative analyses of CAG expansion in ~50 central nervous system (CNS) and peripheral postmortem tissues from seven adult-onset and one juvenile-onset HD individual. We also assessed ATXN1 CAG repeat expansion in brain regions of an individual with a neurologically and pathologically distinct repeat expansion disorder, spinocerebellar ataxia type 1 (SCA1). Our findings reveal similar profiles of tissue instability in all HD individuals, which, notably, were also apparent in the SCA1 individual. CAG expansion was observed in all tissues, but to different degrees, with multiple cortical regions and neostriatum tending to have the greatest instability in the CNS, and liver in the periphery. These patterns indicate different propensities for CAG expansion contributed by disease locus-independent trans-factors and demonstrate that expansion per se is not sufficient to cause cell type or disease-specific pathology. Rather, pathology may reflect distinct toxic processes triggered by different repeat lengths across cell types and diseases. We also find that the HTT CAG length-dependent expansion propensity of an individual is reflected in all tissues and in cerebrospinal fluid. Our data indicate that peripheral cells may be a useful source to measure CAG expansion in biomarker assays for therapeutic efforts, prompting efforts to dissect underlying mechanisms of expansion that may differ between the brain and periphery.
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Affiliation(s)
- Ricardo Mouro Pinto
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Larissa Arning
- Department of Human Genetics, Ruhr-University Bochum, Bochum 44780, Germany
| | - James V Giordano
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Pedram Razghandi
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Marissa A Andrew
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Tammy Gillis
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Kevin Correia
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Jayalakshmi S Mysore
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | | | - Constanze R Parwez
- Department of Neuroanatomy and Molecular Brain Research, Institute of Anatomy, Ruhr-University Bochum, Bochum 44780, Germany
| | - Sarah M von Hein
- Department of Neurology, Huntington Centre NRW, St. Josef-Hospital, Ruhr-University Bochum, Bochum 44791, Germany
| | - H Brent Clark
- Department of Laboratory Medicine and Pathology, Institute of Translational Neuroscience, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Huu Phuc Nguyen
- Department of Human Genetics, Ruhr-University Bochum, Bochum 44780, Germany
| | - Eckart Förster
- Department of Neuroanatomy and Molecular Brain Research, Institute of Anatomy, Ruhr-University Bochum, Bochum 44780, Germany
| | - Allison Beller
- Department of Pathology, University of Washington, Seattle, Washington 98195, USA
| | - Suman Jayadaev
- Department of Neurology, University of Washington, Seattle, Washington 98195, USA
| | - C Dirk Keene
- Department of Pathology, University of Washington, Seattle, Washington 98195, USA
| | - Thomas D Bird
- Department of Neurology, University of Washington, Seattle, Washington 98195, USA.,Department of Medicine, University of Washington, Seattle, Washington 98195, USA.,Geriatrics Research Education and Clinical Center, VA Puget Sound Medical Center, Seattle, WA 98108, USA
| | - Diane Lucente
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Jean-Paul Vonsattel
- Department of Pathology and Cell Biology, Columbia University Medical Center and the New York Presbyterian Hospital, New York, NY 10032, USA
| | - Harry Orr
- Department of Laboratory Medicine and Pathology, Institute of Translational Neuroscience, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Carsten Saft
- Department of Neurology, Huntington Centre NRW, St. Josef-Hospital, Ruhr-University Bochum, Bochum 44791, Germany
| | - Elisabeth Petrasch-Parwez
- Department of Neuroanatomy and Molecular Brain Research, Institute of Anatomy, Ruhr-University Bochum, Bochum 44780, Germany
| | - Vanessa C Wheeler
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
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25
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Loupe JM, Pinto RM, Kim KH, Gillis T, Mysore JS, Andrew MA, Kovalenko M, Murtha R, Seong I, Gusella JF, Kwak S, Howland D, Lee R, Lee JM, Wheeler VC, MacDonald ME. Promotion of somatic CAG repeat expansion by Fan1 knock-out in Huntington's disease knock-in mice is blocked by Mlh1 knock-out. Hum Mol Genet 2021; 29:3044-3053. [PMID: 32876667 PMCID: PMC7645713 DOI: 10.1093/hmg/ddaa196] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 07/20/2020] [Accepted: 08/27/2020] [Indexed: 12/13/2022] Open
Abstract
Recent genome-wide association studies of age-at-onset in Huntington’s disease (HD) point to distinct modes of potential disease modification: altering the rate of somatic expansion of the HTT CAG repeat or altering the resulting CAG threshold length-triggered toxicity process. Here, we evaluated the mouse orthologs of two HD age-at-onset modifier genes, FAN1 and RRM2B, for an influence on somatic instability of the expanded CAG repeat in Htt CAG knock-in mice. Fan1 knock-out increased somatic expansion of Htt CAG repeats, in the juvenile- and the adult-onset HD ranges, whereas knock-out of Rrm2b did not greatly alter somatic Htt CAG repeat instability. Simultaneous knock-out of Mlh1, the ortholog of a third HD age-at-onset modifier gene (MLH1), which suppresses somatic expansion of the Htt knock-in CAG repeat, blocked the Fan1 knock-out-induced acceleration of somatic CAG expansion. This genetic interaction indicates that functional MLH1 is required for the CAG repeat destabilizing effect of FAN1 loss. Thus, in HD, it is uncertain whether the RRM2B modifier effect on timing of onset may be due to a DNA instability mechanism. In contrast, the FAN1 modifier effects reveal that functional FAN1 acts to suppress somatic CAG repeat expansion, likely in genetic interaction with other DNA instability modifiers whose combined effects can hasten or delay onset and other CAG repeat length-driven phenotypes.
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Affiliation(s)
- Jacob M Loupe
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Ricardo Mouro Pinto
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Kyung-Hee Kim
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Tammy Gillis
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Jayalakshmi S Mysore
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Marissa A Andrew
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Marina Kovalenko
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Ryan Murtha
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - IhnSik Seong
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - James F Gusella
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA.,Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.,Medical and Population Genetics Program, The Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
| | - Seung Kwak
- CHDI Foundation, Princeton, NJ 08540, USA
| | | | - Ramee Lee
- CHDI Foundation, Princeton, NJ 08540, USA
| | - Jong-Min Lee
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Vanessa C Wheeler
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Marcy E MacDonald
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA.,Medical and Population Genetics Program, The Broad Institute of M.I.T. and Harvard, Cambridge, MA 02142, USA
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26
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Kacher R, Lejeune FX, Noël S, Cazeneuve C, Brice A, Humbert S, Durr A. Propensity for somatic expansion increases over the course of life in Huntington disease. eLife 2021; 10:64674. [PMID: 33983118 PMCID: PMC8118653 DOI: 10.7554/elife.64674] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 04/27/2021] [Indexed: 12/03/2022] Open
Abstract
Recent work on Huntington disease (HD) suggests that somatic instability of CAG repeat tracts, which can expand into the hundreds in neurons, explains clinical outcomes better than the length of the inherited allele. Here, we measured somatic expansion in blood samples collected from the same 50 HD mutation carriers over a twenty-year period, along with post-mortem tissue from 15 adults and 7 fetal mutation carriers, to examine somatic expansions at different stages of life. Post-mortem brains, as previously reported, had the greatest expansions, but fetal cortex had virtually none. Somatic instability in blood increased with age, despite blood cells being short-lived compared to neurons, and was driven mostly by CAG repeat length, then by age at sampling and by interaction between these two variables. Expansion rates were higher in symptomatic subjects. These data lend support to a previously proposed computational model of somatic instability-driven disease.
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Affiliation(s)
- Radhia Kacher
- Sorbonne Université, Paris Brain Institute (ICM Institut du Cerveau), AP-HP, INSERM, CNRS, University Hospital Pitié-Salpêtrière, Paris, France.,Univ. Grenoble Alpes, INSERM, U 1216, Grenoble Institut Neurosciences, Grenoble, France
| | - François-Xavier Lejeune
- Sorbonne Université, Paris Brain Institute (ICM Institut du Cerveau), AP-HP, INSERM, CNRS, University Hospital Pitié-Salpêtrière, Paris, France.,Paris Brain Institute's Data and Analysis Core, University Hospital Pitié-Salpêtrière, Paris, France
| | - Sandrine Noël
- Neurogenetics Laboratory, Department of Genetics, Assistance Publique-Hôpitaux de Paris, University Hospital Pitié-Salpêtrière, Paris, France
| | - Cécile Cazeneuve
- Neurogenetics Laboratory, Department of Genetics, Assistance Publique-Hôpitaux de Paris, University Hospital Pitié-Salpêtrière, Paris, France
| | - Alexis Brice
- Sorbonne Université, Paris Brain Institute (ICM Institut du Cerveau), AP-HP, INSERM, CNRS, University Hospital Pitié-Salpêtrière, Paris, France
| | - Sandrine Humbert
- Univ. Grenoble Alpes, INSERM, U 1216, Grenoble Institut Neurosciences, Grenoble, France
| | - Alexandra Durr
- Sorbonne Université, Paris Brain Institute (ICM Institut du Cerveau), AP-HP, INSERM, CNRS, University Hospital Pitié-Salpêtrière, Paris, France.,Neurogenetics Laboratory, Department of Genetics, Assistance Publique-Hôpitaux de Paris, University Hospital Pitié-Salpêtrière, Paris, France
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27
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Monckton DG. The Contribution of Somatic Expansion of the CAG Repeat to Symptomatic Development in Huntington's Disease: A Historical Perspective. J Huntingtons Dis 2021; 10:7-33. [PMID: 33579863 PMCID: PMC7990401 DOI: 10.3233/jhd-200429] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The discovery in the early 1990s of the expansion of unstable simple sequence repeats as the causative mutation for a number of inherited human disorders, including Huntington’s disease (HD), opened up a new era of human genetics and provided explanations for some old problems. In particular, an inverse association between the number of repeats inherited and age at onset, and unprecedented levels of germline instability, biased toward further expansion, provided an explanation for the wide symptomatic variability and anticipation observed in HD and many of these disorders. The repeats were also revealed to be somatically unstable in a process that is expansion-biased, age-dependent and tissue-specific, features that are now increasingly recognised as contributory to the age-dependence, progressive nature and tissue specificity of the symptoms of HD, and at least some related disorders. With much of the data deriving from affected individuals, and model systems, somatic expansions have been revealed to arise in a cell division-independent manner in critical target tissues via a mechanism involving key components of the DNA mismatch repair pathway. These insights have opened new approaches to thinking about how the disease could be treated by suppressing somatic expansion and revealed novel protein targets for intervention. Exciting times lie ahead in turning these insights into novel therapies for HD and related disorders.
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Affiliation(s)
- Darren G Monckton
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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28
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Hong EP, MacDonald ME, Wheeler VC, Jones L, Holmans P, Orth M, Monckton DG, Long JD, Kwak S, Gusella JF, Lee JM. Huntington's Disease Pathogenesis: Two Sequential Components. J Huntingtons Dis 2021; 10:35-51. [PMID: 33579862 PMCID: PMC7990433 DOI: 10.3233/jhd-200427] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Historically, Huntington's disease (HD; OMIM #143100) has played an important role in the enormous advances in human genetics seen over the past four decades. This familial neurodegenerative disorder involves variable onset followed by consistent worsening of characteristic abnormal movements along with cognitive decline and psychiatric disturbances. HD was the first autosomal disease for which the genetic defect was assigned to a position on the human chromosomes using only genetic linkage analysis with common DNA polymorphisms. This discovery set off a multitude of similar studies in other diseases, while the HD gene, later renamed HTT, and its vicinity in chromosome 4p16.3 then acted as a proving ground for development of technologies to clone and sequence genes based upon their genomic location, with the growing momentum of such advances fueling the Human Genome Project. The identification of the HD gene has not yet led to an effective treatment, but continued human genetic analysis of genotype-phenotype relationships in large HD subject populations, first at the HTT locus and subsequently genome-wide, has provided insights into pathogenesis that divide the course of the disease into two sequential, mechanistically distinct components.
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Affiliation(s)
- Eun Pyo Hong
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA.,Department of Neurology, Harvard Medical School, Boston, MA, USA.,Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, USA
| | - Marcy E MacDonald
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA.,Department of Neurology, Harvard Medical School, Boston, MA, USA.,Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, USA
| | - Vanessa C Wheeler
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA.,Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Lesley Jones
- Medical Research Council (MRC) Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurology, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Peter Holmans
- Medical Research Council (MRC) Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurology, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Michael Orth
- Department of Neurology, University of Ulm, Germany
| | - Darren G Monckton
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Jeffrey D Long
- Department of Psychiatry, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.,Department of Biostatistics, College of Public Health, University of Iowa, Iowa City, IA, USA
| | - Seung Kwak
- CHDI Management/CHDI Foundation, Princeton, NJ, USA
| | - James F Gusella
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA.,Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, USA.,Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Jong-Min Lee
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA.,Department of Neurology, Harvard Medical School, Boston, MA, USA.,Medical and Population Genetics Program, the Broad Institute of M.I.T. and Harvard, Cambridge, MA, USA
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29
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Jung R, Lee Y, Barker D, Correia K, Shin B, Loupe J, Collins RL, Lucente D, Ruliera J, Gillis T, Mysore JS, Rodan L, Picker J, Lee JM, Howland D, Lee R, Kwak S, MacDonald ME, Gusella JF, Seong IS. Mutations causing Lopes-Maciel-Rodan syndrome are huntingtin hypomorphs. Hum Mol Genet 2021; 30:135-148. [PMID: 33432339 DOI: 10.1093/hmg/ddaa283] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 11/18/2020] [Accepted: 12/24/2020] [Indexed: 12/31/2022] Open
Abstract
Huntington's disease pathogenesis involves a genetic gain-of-function toxicity mechanism triggered by the expanded HTT CAG repeat. Current therapeutic efforts aim to suppress expression of total or mutant huntingtin, though the relationship of huntingtin's normal activities to the gain-of-function mechanism and what the effects of huntingtin-lowering might be are unclear. Here, we have re-investigated a rare family segregating two presumed HTT loss-of-function (LoF) variants associated with the developmental disorder, Lopes-Maciel-Rodan syndrome (LOMARS), using whole-genome sequencing of DNA from cell lines, in conjunction with analysis of mRNA and protein expression. Our findings correct the muddled annotation of these HTT variants, reaffirm they are the genetic cause of the LOMARS phenotype and demonstrate that each variant is a huntingtin hypomorphic mutation. The NM_002111.8: c.4469+1G>A splice donor variant results in aberrant (exon 34) splicing and severely reduced mRNA, whereas, surprisingly, the NM_002111.8: c.8157T>A NP_002102.4: Phe2719Leu missense variant results in abnormally rapid turnover of the Leu2719 huntingtin protein. Thus, although rare and subject to an as yet unknown LoF intolerance at the population level, bona fide HTT LoF variants can be transmitted by normal individuals leading to severe consequences in compound heterozygotes due to huntingtin deficiency.
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Affiliation(s)
- Roy Jung
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Yejin Lee
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Douglas Barker
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Kevin Correia
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Baehyun Shin
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Jacob Loupe
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Ryan L Collins
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Medical and Population Genetics Program, The Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA.,Program in Bioinformatics and Integrative Genomics, Division of Medical Sciences, Harvard Medical School, Boston, MA 02114, USA
| | - Diane Lucente
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Jayla Ruliera
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Tammy Gillis
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Jayalakshmi S Mysore
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Lance Rodan
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Neurology, Boston Children's Hospital, Harvard Medical School, MA 02115, USA
| | - Jonathan Picker
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Child and Adolescent Psychiatry, Boston Children's Hospital, Harvard Medical School, MA 02115, USA
| | - Jong-Min Lee
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - David Howland
- CHDI Management/CHDI Foundation Inc., Princeton, NJ 08540, USA
| | - Ramee Lee
- CHDI Management/CHDI Foundation Inc., Princeton, NJ 08540, USA
| | - Seung Kwak
- CHDI Management/CHDI Foundation Inc., Princeton, NJ 08540, USA
| | - Marcy E MacDonald
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA.,Medical and Population Genetics Program, The Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA
| | - James F Gusella
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Medical and Population Genetics Program, The Broad Institute of M.I.T. and Harvard, Cambridge, MA, 02142, USA.,Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, 02115, USA
| | - Ihn Sik Seong
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
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30
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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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31
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Tabrizi SJ, Flower MD, Ross CA, Wild EJ. Huntington disease: new insights into molecular pathogenesis and therapeutic opportunities. Nat Rev Neurol 2020; 16:529-546. [PMID: 32796930 DOI: 10.1038/s41582-020-0389-4] [Citation(s) in RCA: 235] [Impact Index Per Article: 58.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2020] [Indexed: 12/11/2022]
Abstract
Huntington disease (HD) is a neurodegenerative disease caused by CAG repeat expansion in the huntingtin gene (HTT) and involves a complex web of pathogenic mechanisms. Mutant HTT (mHTT) disrupts transcription, interferes with immune and mitochondrial function, and is aberrantly modified post-translationally. Evidence suggests that the mHTT RNA is toxic, and at the DNA level, somatic CAG repeat expansion in vulnerable cells influences the disease course. Genome-wide association studies have identified DNA repair pathways as modifiers of somatic instability and disease course in HD and other repeat expansion diseases. In animal models of HD, nucleocytoplasmic transport is disrupted and its restoration is neuroprotective. Novel cerebrospinal fluid (CSF) and plasma biomarkers are among the earliest detectable changes in individuals with premanifest HD and have the sensitivity to detect therapeutic benefit. Therapeutically, the first human trial of an HTT-lowering antisense oligonucleotide successfully, and safely, reduced the CSF concentration of mHTT in individuals with HD. A larger trial, powered to detect clinical efficacy, is underway, along with trials of other HTT-lowering approaches. In this Review, we discuss new insights into the molecular pathogenesis of HD and future therapeutic strategies, including the modulation of DNA repair and targeting the DNA mutation itself.
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Affiliation(s)
- Sarah J Tabrizi
- Huntington's Disease Centre, University College London, London, UK. .,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London, London, UK. .,UK Dementia Research Institute, University College London, London, UK.
| | - Michael D Flower
- Huntington's Disease Centre, University College London, London, UK.,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute, University College London, London, UK
| | - Christopher A Ross
- Departments of Neurology, Neuroscience and Pharmacology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Edward J Wild
- Huntington's Disease Centre, University College London, London, UK.,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London, London, UK
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32
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Proukakis C. Somatic mutations in neurodegeneration: An update. Neurobiol Dis 2020; 144:105021. [PMID: 32712267 DOI: 10.1016/j.nbd.2020.105021] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 06/12/2020] [Accepted: 07/13/2020] [Indexed: 12/20/2022] Open
Abstract
Mosaicism, the presence of genomic differences between cells due to post-zygotic somatic mutations, is widespread in the human body, including within the brain. A role for this in neurodegenerative diseases has long been hypothesised, and technical developments are now allowing the question to be addressed in detail. The rapidly accumulating evidence is discussed in this review, with a focus on recent developments. Somatic mutations of numerous types may occur, including single nucleotide variants (SNVs), copy number variants (CNVs), and retrotransposon insertions. They could act as initiators or risk factors, especially if they arise in development, although they could also result from the disease process, potentially contributing to progression. In common sporadic neurodegenerative disorders, relevant mutations have been reported in synucleinopathies, comprising somatic gains of SNCA in Parkinson's disease and multiple system atrophy, and in Alzheimer's disease, where a novel recombination mechanism leading to somatic variants of APP, as well as an excess of somatic SNVs affecting tau phosphorylation, have been reported. In Mendelian repeat expansion disorders, mosaicism due to somatic instability, first detected 25 years ago, has come to the forefront. Brain somatic SNVs occur in DNA repair disorders, and there is evidence for a role of several ALS genes in DNA repair. While numerous challenges, and need for further validation, remain, this new, or perhaps rediscovered, area of research has the potential to transform our understanding of neurodegeneration.
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Affiliation(s)
- Christos Proukakis
- Department of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London, UK.
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33
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Khristich AN, Mirkin SM. On the wrong DNA track: Molecular mechanisms of repeat-mediated genome instability. J Biol Chem 2020; 295:4134-4170. [PMID: 32060097 PMCID: PMC7105313 DOI: 10.1074/jbc.rev119.007678] [Citation(s) in RCA: 148] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Expansions of simple tandem repeats are responsible for almost 50 human diseases, the majority of which are severe, degenerative, and not currently treatable or preventable. In this review, we first describe the molecular mechanisms of repeat-induced toxicity, which is the connecting link between repeat expansions and pathology. We then survey alternative DNA structures that are formed by expandable repeats and review the evidence that formation of these structures is at the core of repeat instability. Next, we describe the consequences of the presence of long structure-forming repeats at the molecular level: somatic and intergenerational instability, fragility, and repeat-induced mutagenesis. We discuss the reasons for gender bias in intergenerational repeat instability and the tissue specificity of somatic repeat instability. We also review the known pathways in which DNA replication, transcription, DNA repair, and chromatin state interact and thereby promote repeat instability. We then discuss possible reasons for the persistence of disease-causing DNA repeats in the genome. We describe evidence suggesting that these repeats are a payoff for the advantages of having abundant simple-sequence repeats for eukaryotic genome function and evolvability. Finally, we discuss two unresolved fundamental questions: (i) why does repeat behavior differ between model systems and human pedigrees, and (ii) can we use current knowledge on repeat instability mechanisms to cure repeat expansion diseases?
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Affiliation(s)
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, Massachusetts 02155.
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34
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Lee JM, Correia K, Loupe J, Kim KH, Barker D, Hong EP, Chao MJ, Long JD, Lucente D, Vonsattel JPG, Pinto RM, Abu Elneel K, Ramos EM, Mysore JS, Gillis T, Wheeler VC, MacDonald ME, Gusella JF, McAllister B, Massey T, Medway C, Stone TC, Hall L, Jones L, Holmans P, Kwak S, Ehrhardt AG, Sampaio C, Ciosi M, Maxwell A, Chatzi A, Monckton DG, Orth M, Landwehrmeyer GB, Paulsen JS, Dorsey ER, Shoulson I, Myers RH. CAG Repeat Not Polyglutamine Length Determines Timing of Huntington's Disease Onset. Cell 2019; 178:887-900.e14. [PMID: 31398342 PMCID: PMC6700281 DOI: 10.1016/j.cell.2019.06.036] [Citation(s) in RCA: 267] [Impact Index Per Article: 53.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Revised: 04/08/2019] [Accepted: 06/27/2019] [Indexed: 01/27/2023]
Abstract
Variable, glutamine-encoding, CAA interruptions indicate that a property of the uninterrupted HTT CAG repeat sequence, distinct from the length of huntingtin's polyglutamine segment, dictates the rate at which Huntington's disease (HD) develops. The timing of onset shows no significant association with HTT cis-eQTLs but is influenced, sometimes in a sex-specific manner, by polymorphic variation at multiple DNA maintenance genes, suggesting that the special onset-determining property of the uninterrupted CAG repeat is a propensity for length instability that leads to its somatic expansion. Additional naturally occurring genetic modifier loci, defined by GWAS, may influence HD pathogenesis through other mechanisms. These findings have profound implications for the pathogenesis of HD and other repeat diseases and question the fundamental premise that polyglutamine length determines the rate of pathogenesis in the "polyglutamine disorders."
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35
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Ferreira GC, Oberstaller J, Fonseca R, Keller TE, Adapa SR, Gibbons J, Wang C, Liu X, Li C, Pham M, Dayhoff Ii GW, Duong LM, Reyes LT, Laratelli LE, Franz D, Fatumo S, Bari AG, Freischel A, Fiedler L, Dokur O, Sharma K, Cragun D, Busby B, Jiang RHY. Iron Hack - A symposium/hackathon focused on porphyrias, Friedreich's ataxia, and other rare iron-related diseases. F1000Res 2019; 8:1135. [PMID: 31824661 PMCID: PMC6894363 DOI: 10.12688/f1000research.19140.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/05/2019] [Indexed: 01/14/2023] Open
Abstract
Background: Basic and clinical scientific research at the University of South Florida (USF) have intersected to support a multi-faceted approach around a common focus on rare iron-related diseases. We proposed a modified version of the National Center for Biotechnology Information’s (NCBI) Hackathon-model to take full advantage of local expertise in building “Iron Hack”, a rare disease-focused hackathon. As the collaborative, problem-solving nature of hackathons tends to attract participants of highly-diverse backgrounds, organizers facilitated a symposium on rare iron-related diseases, specifically porphyrias and Friedreich’s ataxia, pitched at general audiences. Methods: The hackathon was structured to begin each day with presentations by expert clinicians, genetic counselors, researchers focused on molecular and cellular biology, public health/global health, genetics/genomics, computational biology, bioinformatics, biomolecular science, bioengineering, and computer science, as well as guest speakers from the American Porphyria Foundation (APF) and Friedreich’s Ataxia Research Alliance (FARA) to inform participants as to the human impact of these diseases. Results: As a result of this hackathon, we developed resources that are relevant not only to these specific disease-models, but also to other rare diseases and general bioinformatics problems. Within two and a half days, “Iron Hack” participants successfully built collaborative projects to visualize data, build databases, improve rare disease diagnosis, and study rare-disease inheritance. Conclusions: The purpose of this manuscript is to demonstrate the utility of a hackathon model to generate prototypes of generalizable tools for a given disease and train clinicians and data scientists to interact more effectively.
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Affiliation(s)
- Gloria C Ferreira
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, MDC 7, Tampa, FL, 33612, USA
| | - Jenna Oberstaller
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Renée Fonseca
- Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa, FL, 33612, USA
| | - Thomas E Keller
- University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Swamy Rakesh Adapa
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Justin Gibbons
- Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa, FL, 33612, USA
| | - Chengqi Wang
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Xiaoming Liu
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Chang Li
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Minh Pham
- Center for Urban Transportation Research, University of South Florida, 4202 E. Fowler Avenue, CUT100, Tampa, FL, 33620, USA
| | - Guy W Dayhoff Ii
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE 205, Tampa, FL, 33620-5250, USA
| | - Linh M Duong
- College of Public Health, University of South Florida, 13201 Bruce B. Downs Blvd., MDC 56, Tampa, FL, 33612, USA.,Moffitt Cancer Center, Tampa, FL, 33612, USA
| | - Luis Tañón Reyes
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Ave, ISA 2015 Tampa, FL, 33620, USA
| | - Luciano Enrique Laratelli
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE 205, Tampa, FL, 33620-5250, USA
| | - Douglas Franz
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE 205, Tampa, FL, 33620-5250, USA
| | - Segun Fatumo
- MRC/UVRI and LSHTM (Uganda Research Unit), Entebbe, Uganda
| | - Atm Golam Bari
- Department of Computer Science and Engineering, University of South Florida, Tampa, FL, USA
| | | | - Lindsey Fiedler
- College of Public Health, University of South Florida, 13201 Bruce B. Downs Blvd., MDC 56, Tampa, FL, 33612, USA
| | - Omkar Dokur
- Department of Computer Science and Engineering, University of South Florida, Tampa, FL, USA
| | | | - Deborah Cragun
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Ben Busby
- National Library of Medicine, 8600 Rockville Pike, Bethesda, MD, 20894-6075, USA
| | - Rays H Y Jiang
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
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Eyk CLV, Samaraweera SE, Scott A, Webber DL, Harvey DP, Mecinger O, O’Keefe LV, Cropley JE, Young P, Ho J, Suter C, Richards RI. Non-self mutation: double-stranded RNA elicits antiviral pathogenic response in a Drosophila model of expanded CAG repeat neurodegenerative diseases. Hum Mol Genet 2019; 28:3000-3012. [DOI: 10.1093/hmg/ddz096] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 04/11/2019] [Accepted: 05/06/2019] [Indexed: 12/16/2022] Open
Abstract
Abstract
Inflammation is activated prior to symptoms in neurodegenerative diseases, providing a plausible pathogenic mechanism. Indeed, genetic and pharmacological ablation studies in animal models of several neurodegenerative diseases demonstrate that inflammation is required for pathology. However, while there is growing evidence that inflammation-mediated pathology may be the common mechanism underlying neurodegenerative diseases, including those due to dominantly inherited expanded repeats, the proximal causal agent is unknown. Expanded CAG.CUG repeat double-stranded RNA causes inflammation-mediated pathology when expressed in Drosophila. Repeat dsRNA is recognized by Dicer-2 as a foreign or ‘non-self’ molecule triggering both antiviral RNA and RNAi pathways. Neither of the RNAi pathway cofactors R2D2 nor loquacious are necessary, indicating antiviral RNA activation. RNA modification enables avoidance of recognition as ‘non-self’ by the innate inflammatory surveillance system. Human ADAR1 edits RNA conferring ‘self’ status and when co-expressed with expanded CAG.CUG dsRNA in Drosophila the pathology is lost. Cricket Paralysis Virus protein CrPV-1A is a known antagonist of Argonaute-2 in Drosophila antiviral defense. CrPV-1A co-expression also rescues pathogenesis, confirming anti-viral-RNA response. Repeat expansion mutation therefore confers ‘non-self’ recognition of endogenous RNA, thereby providing a proximal, autoinflammatory trigger for expanded repeat neurodegenerative diseases.
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Affiliation(s)
- Clare L van Eyk
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Saumya E Samaraweera
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Andrew Scott
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Dani L Webber
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5000, Australia
| | - David P Harvey
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Olivia Mecinger
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Louise V O’Keefe
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Jennifer E Cropley
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Liverpool St, Darlinghurst, Sydney 2010, Australia
- Faculty of Medicine, University of New South Wales, Kensington, New South Wales 2042, Australia
| | - Paul Young
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Liverpool St, Darlinghurst, Sydney 2010, Australia
- Faculty of Medicine, University of New South Wales, Kensington, New South Wales 2042, Australia
| | - Joshua Ho
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Liverpool St, Darlinghurst, Sydney 2010, Australia
- Faculty of Medicine, University of New South Wales, Kensington, New South Wales 2042, Australia
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong
| | - Catherine Suter
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Liverpool St, Darlinghurst, Sydney 2010, Australia
- Faculty of Medicine, University of New South Wales, Kensington, New South Wales 2042, Australia
| | - Robert I Richards
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5000, Australia
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Goold R, Flower M, Moss DH, Medway C, Wood-Kaczmar A, Andre R, Farshim P, Bates GP, Holmans P, Jones L, Tabrizi SJ. FAN1 modifies Huntington's disease progression by stabilizing the expanded HTT CAG repeat. Hum Mol Genet 2019; 28:650-661. [PMID: 30358836 PMCID: PMC6360275 DOI: 10.1093/hmg/ddy375] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 10/15/2018] [Accepted: 10/16/2018] [Indexed: 11/13/2022] Open
Abstract
Huntington's disease (HD) is an inherited neurodegenerative disease caused by an expanded CAG repeat in the huntingtin (HTT) gene. CAG repeat length explains around half of the variation in age at onset (AAO) but genetic variation elsewhere in the genome accounts for a significant proportion of the remainder. Genome-wide association studies have identified a bidirectional signal on chromosome 15, likely underlain by FANCD2- and FANCI-associated nuclease 1 (FAN1), a nuclease involved in DNA interstrand cross link repair. Here we show that increased FAN1 expression is significantly associated with delayed AAO and slower progression of HD, suggesting FAN1 is protective in the context of an expanded HTT CAG repeat. FAN1 overexpression in human cells reduces CAG repeat expansion in exogenously expressed mutant HTT exon 1, and in patient-derived stem cells and differentiated medium spiny neurons, FAN1 knockdown increases CAG repeat expansion. The stabilizing effects are FAN1 concentration and CAG repeat length-dependent. We show that FAN1 binds to the expanded HTT CAG repeat DNA and its nuclease activity is not required for protection against CAG repeat expansion. These data shed new mechanistic insights into how the genetic modifiers of HD act to alter disease progression and show that FAN1 affects somatic expansion of the CAG repeat through a nuclease-independent mechanism. This provides new avenues for therapeutic interventions in HD and potentially other triplet repeat disorders.
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Affiliation(s)
- Robert Goold
- UCL Huntington’s Disease Centre,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London,Queen Square, London WC1N 3BG, UK
| | - Michael Flower
- UCL Huntington’s Disease Centre,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London,Queen Square, London WC1N 3BG, UK
| | - Davina Hensman Moss
- UCL Huntington’s Disease Centre,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London,Queen Square, London WC1N 3BG, UK
| | - Chris Medway
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, CF24 4HQ, UK
| | - Alison Wood-Kaczmar
- UCL Huntington’s Disease Centre,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London,Queen Square, London WC1N 3BG, UK
| | - Ralph Andre
- UCL Huntington’s Disease Centre,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London,Queen Square, London WC1N 3BG, UK
| | - Pamela Farshim
- UCL Huntington’s Disease Centre,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London,Queen Square, London WC1N 3BG, UK
| | - Gill P Bates
- UCL Huntington’s Disease Centre,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London,Queen Square, London WC1N 3BG, UK
- UK Dementia Research Institute, University College London, WC1N 3BG, UK
| | - Peter Holmans
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, CF24 4HQ, UK
| | - Lesley Jones
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, CF24 4HQ, UK
| | - Sarah J Tabrizi
- UCL Huntington’s Disease Centre,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London,Queen Square, London WC1N 3BG, UK
- UK Dementia Research Institute, University College London, WC1N 3BG, UK
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Sawiak SJ, Wood NI, Morton AJ. Similar Progression of Morphological and Metabolic Phenotype in R6/2 Mice with Different CAG Repeats Revealed by In Vivo Magnetic Resonance Imaging and Spectroscopy. J Huntingtons Dis 2017; 5:271-283. [PMID: 27662335 DOI: 10.3233/jhd-160208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Huntington's disease (HD) is caused by an unstable polyglutamine (CAG) repeat in the HD gene, whereby a CAG repeat length greater than ∼36 leads to the disease. In HD patients, longer repeats correlate with more severe disease and earlier death. This is also seen in R6/2 mice carrying repeat lengths up to ∼200. Paradoxically, R6/2 mice with repeat lengths >300 have a less aggressive phenotype and longer lifespan than those with shorter repeats. The mechanism underlying this phenomenon is unknown. OBJECTIVE To investigate the consequences of longer repeat lengths on structural changes in the brains of R6/2 mice, especially with regard to progressive atrophy. METHODS We used longitudinal in vivo magnetic resonance imaging (MRI) and spectroscopy (MRS) to compare pathological changes in two strains of R6/2 mice, one with a rapidly progressing disease (250 CAG repeats), and the other with a less aggressive phenotype (350 CAG repeats). RESULTS We found significant progressive brain atrophy in both 250 and 350 CAG repeat mice, as well as changes in metabolites (glutamine/glutamate, choline and aspartate). Although similar in magnitude, atrophy in the brains of 350 CAG R6/2 mice progressed more slowly than that seen in 250 CAG mice, in line with the milder phenotype and longer lifespan. Interestingly, significant atrophy was detectable in 350 CAG mice as early as 8-12 weeks of age, although behavioural abnormalities in these mice are not apparent before 25-30 weeks. This finding fits well with human data from the PREDICT-HD and TRACK-HD project, where reductions in brain volume were found 10 years in advance of the onset of symptoms. CONCLUSIONS The similar brain atrophy with a mismatch between onset of brain atrophy and behavioural phenotype in HD mice with 350 repeats will make this mouse particularly useful for modelling early stages of HD pathology.
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Affiliation(s)
- Stephen J Sawiak
- Wolfson Brain Imaging Centre, University of Cambridge, Box 65 Addenbrooke's Hospital, Cambridge, UK.,Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK
| | - Nigel I Wood
- Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - A Jennifer Morton
- Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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Bean NG, Elliott R, Eshragh A, Ross JV. On Binomial Observations of Continuous-Time Markovian Population Models. J Appl Probab 2015. [DOI: 10.1239/jap/1437658609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In this paper we consider a class of stochastic processes based on binomial observations of continuous-time, Markovian population models. We derive the conditional probability mass function of the next binomial observation given a set of binomial observations. For this purpose, we first find the conditional probability mass function of the underlying continuous-time Markovian population model, given a set of binomial observations, by exploiting a conditional Bayes' theorem from filtering, and then use the law of total probability to find the former. This result paves the way for further study of the stochastic process introduced by the binomial observations. We utilize our results to show that binomial observations of the simple birth process are non-Markovian.
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Age-, tissue- and length-dependent bidirectional somatic CAG•CTG repeat instability in an allelic series of R6/2 Huntington disease mice. Neurobiol Dis 2015; 76:98-111. [PMID: 25662336 DOI: 10.1016/j.nbd.2015.01.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 11/30/2014] [Accepted: 01/25/2015] [Indexed: 12/11/2022] Open
Abstract
The expansion of simple sequence CAG•CTG repeats is associated with a number of inherited disorders including Huntington disease (HD), myotonic dystrophy type 1 and several of the spinocerebellar ataxias. Inherited disease-associated alleles usually exceed 40 repeats and may be in excess of 1,000 repeats in some disorders. Inherited allele length is inversely proportional to age at onset, and frequent germline expansions account for the striking anticipation observed in affected families. Expanded disease associated alleles are also somatically unstable via a pathway that is age dependent and tissue specific, and also appears to be expansion biased. Somatic expansions are thought to contribute toward both tissue specificity and disease progression. Here we have examined the somatic mutational dynamics in brain and peripheral tissues from an allelic series of R6/2 HD transgenic mice inheriting from 52 to >700 CAG repeats. We found age-dependent, tissue-specific somatic instability, with particularly large expansions observed in the striatum and cortex. We also found a positive increase in somatic instability with increasing allele length. Surprisingly, however, the degree of somatic variation did not increase in a linear fashion, but leveled off with increasing allele length. Most unexpectedly, the almost exclusive bias toward the accumulation of expansions observed in mice inheriting smaller alleles was lost, and a high frequency of large somatic contractions was observed in mice inheriting very large alleles (>500 repeats). These data highlight the bidirectional nature of CAG•CTG repeat instability and the subtle balance that exists between expansion and contraction in vivo. Defining the dynamics and tissue specificity of expansion and contraction is important for understanding the role of genetic instability in pathophysiology and in particular the development of novel therapies based on suppressing expansions and/or promoting contractions.
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Mismatch repair genes Mlh1 and Mlh3 modify CAG instability in Huntington's disease mice: genome-wide and candidate approaches. PLoS Genet 2013; 9:e1003930. [PMID: 24204323 PMCID: PMC3814320 DOI: 10.1371/journal.pgen.1003930] [Citation(s) in RCA: 156] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 09/15/2013] [Indexed: 11/19/2022] Open
Abstract
The Huntington's disease gene (HTT) CAG repeat mutation undergoes somatic expansion that correlates with pathogenesis. Modifiers of somatic expansion may therefore provide routes for therapies targeting the underlying mutation, an approach that is likely applicable to other trinucleotide repeat diseases. Huntington's disease HdhQ111 mice exhibit higher levels of somatic HTT CAG expansion on a C57BL/6 genetic background (B6.HdhQ111) than on a 129 background (129.HdhQ111). Linkage mapping in (B6x129).HdhQ111 F2 intercross animals identified a single quantitative trait locus underlying the strain-specific difference in expansion in the striatum, implicating mismatch repair (MMR) gene Mlh1 as the most likely candidate modifier. Crossing B6.HdhQ111 mice onto an Mlh1 null background demonstrated that Mlh1 is essential for somatic CAG expansions and that it is an enhancer of nuclear huntingtin accumulation in striatal neurons. HdhQ111 somatic expansion was also abolished in mice deficient in the Mlh3 gene, implicating MutLγ (MLH1–MLH3) complex as a key driver of somatic expansion. Strikingly, Mlh1 and Mlh3 genes encoding MMR effector proteins were as critical to somatic expansion as Msh2 and Msh3 genes encoding DNA mismatch recognition complex MutSβ (MSH2–MSH3). The Mlh1 locus is highly polymorphic between B6 and 129 strains. While we were unable to detect any difference in base-base mismatch or short slipped-repeat repair activity between B6 and 129 MLH1 variants, repair efficiency was MLH1 dose-dependent. MLH1 mRNA and protein levels were significantly decreased in 129 mice compared to B6 mice, consistent with a dose-sensitive MLH1-dependent DNA repair mechanism underlying the somatic expansion difference between these strains. Together, these data identify Mlh1 and Mlh3 as novel critical genetic modifiers of HTT CAG instability, point to Mlh1 genetic variation as the likely source of the instability difference in B6 and 129 strains and suggest that MLH1 protein levels play an important role in driving of the efficiency of somatic expansions. The expansion of a CAG repeat underlies Huntington's disease (HD), with longer CAG tracts giving rise to earlier onset and more severe disease. In individuals harboring a CAG expansion the repeat undergoes further somatic expansion over time, particularly in brain cells most susceptible to disease pathogenesis. Preventing this repeat lengthening may delay disease onset and/or slow progression. We are using mouse models of HD to identify the factors that modify the somatic expansion of the HD CAG repeat, as these may provide novel targets for therapeutic intervention. To identify genetic modifiers of somatic expansion in HD mouse models we have used both an unbiased genetic mapping approach in inbred mouse strains that exhibit different levels of somatic expansion, as well as targeted gene knockout approaches. Our results demonstrate that: 1) Mlh1 and Mlh3 genes, encoding components of the DNA mismatch repair pathway, are critical for somatic CAG expansion; 2) in the absence of somatic expansion the pathogenic process in the mouse is slowed; 3) MLH1 protein levels are likely to be a driver of the efficiency of somatic expansion. Together, our data provide new insight into the factors underlying the process of somatic expansion of the HD CAG repeat.
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Jonson I, Ougland R, Larsen E. DNA repair mechanisms in Huntington's disease. Mol Neurobiol 2013; 47:1093-102. [PMID: 23361256 DOI: 10.1007/s12035-013-8409-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Accepted: 01/13/2013] [Indexed: 11/25/2022]
Abstract
The human genome is under continuous attack by a plethora of harmful agents. Without the development of several dedicated DNA repair pathways, the genome would have been destroyed and cell death, inevitable. However, while DNA repair enzymes generally maintain the integrity of the whole genome by properly repairing mutagenic and cytotoxic intermediates, there are cases in which the DNA repair machinery is implicated in causing disease rather than protecting against it. One case is the instability of gene-specific trinucleotides, the causative mutations of numerous disorders including Huntington's disease. The DNA repair proteins induce mutations that are different from the genome-wide mutations that arise in the absence of repair enzymes; they occur at definite loci, they occur in specific tissues during development, and they are age-dependent. These latter characteristics make pluripotent stem cells a suitable model system for triplet repeat expansion disorders. Pluripotent stem cells can be kept in culture for a prolonged period of time and can easily be differentiated into any tissue, e.g., cells along the neural lineage. Here, we review the role of DNA repair proteins in the process of triplet repeat instability in Huntington's disease and also the potential use of pluripotent stem cells to investigate neurodegenerative disorders.
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Affiliation(s)
- Ida Jonson
- Department of Microbiology, University of Oslo, Oslo University Hospital, Rikshospitalet, P. O. Box 4950 Nydalen, 0424 Oslo, Norway
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Chiera NM, Rowinska-Zyrek M, Wieczorek R, Guerrini R, Witkowska D, Remelli M, Kozlowski H. Unexpected impact of the number of glutamine residues on metal complex stability. Metallomics 2013; 5:214-21. [DOI: 10.1039/c3mt20166j] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Morales F, Couto JM, Higham CF, Hogg G, Cuenca P, Braida C, Wilson RH, Adam B, del Valle G, Brian R, Sittenfeld M, Ashizawa T, Wilcox A, Wilcox DE, Monckton DG. Somatic instability of the expanded CTG triplet repeat in myotonic dystrophy type 1 is a heritable quantitative trait and modifier of disease severity. Hum Mol Genet 2012; 21:3558-67. [DOI: 10.1093/hmg/dds185] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Higham CF, Morales F, Cobbold CA, Haydon DT, Monckton DG. High levels of somatic DNA diversity at the myotonic dystrophy type 1 locus are driven by ultra-frequent expansion and contraction mutations. Hum Mol Genet 2012; 21:2450-63. [PMID: 22367968 DOI: 10.1093/hmg/dds059] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Several human genetic diseases are associated with inheriting an abnormally large unstable DNA simple sequence repeat. These sequences mutate, by changing the number of repeats, many times during the lifetime of those affected, with a bias towards expansion. These somatic changes lead not only to the presence of cells with different numbers of repeats in the same tissue, but also produce increasingly longer repeats, contributing towards the progressive nature of the symptoms. Modelling the progression of repeat length throughout the lifetime of individuals has potential for improving prognostic information as well as providing a deeper understanding of the underlying biological process. A large data set comprising blood DNA samples from individuals with one such disease, myotonic dystrophy type 1, provides an opportunity to parameterize a mathematical model for repeat length evolution that we can use to infer biological parameters of interest. We developed new mathematical models by modifying a proposed stochastic birth process to incorporate possible contraction. A hierarchical Bayesian approach was used as the basis for inference, and we estimated the distribution of mutation rates in the population. We used model comparison analysis to reveal, for the first time, that the expansion bias observed in the distributions of repeat lengths is likely to be the cumulative effect of many expansion and contraction events. We predict that mutation events can occur as frequently as every other day, which matches the timing of regular cell activities such as DNA repair and transcription but not DNA replication.
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Affiliation(s)
- Catherine F Higham
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
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47
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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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Goel G, Pal PK, Ravishankar S, Venkatasubramanian G, Jayakumar PN, Krishna N, Purushottam M, Saini J, Faruq M, Mukherji M, Jain S. Gray matter volume deficits in spinocerebellar ataxia: an optimized voxel based morphometric study. Parkinsonism Relat Disord 2011; 17:521-7. [PMID: 21600833 DOI: 10.1016/j.parkreldis.2011.04.008] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 04/18/2011] [Accepted: 04/19/2011] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Spinocerebellar ataxias (SCA) are a group of autosomal dominant ataxias with varied clinical phenotypes. However there are no unique distinguishing features on routine neuroimaging among the various genetically defined SCAs. Voxel-based morphometry (VBM) provides an automated unbiased analysis of structural MRI scans and gives a comprehensive assessment of anatomical differences throughout the brain. OBJECTIVES The aims of this study were to (i) characterize the patterns of atrophy in SCA1, SCA2 and SCA3 using optimized VBM, (ii) demonstrate the characteristic anatomical differences in these genetically distinct SCA subtypes, and (iii) assess the relationship between morphometric measures and the CAG repeat lengths and other attributes of the disease. METHODS Thirty-one genetically confirmed patients suffering from SCA (SCA1 - 12, SCA2 - 9, and SCA3 - 10) were studied. High resolution T1-weighted 3-Dimensional Magnetic Resonance Images of 31 patients were analyzed using the optimized VBM procedure. RESULTS In all the three SCAs there was a significant loss of gray matter in both cerebellar hemispheres and vermis. Vermian atrophy was more pronounced in SCA3, while SCA1 and SCA2 had significant white matter atrophy. Pontine white matter atrophy was more pronounced in SCA2. In SCA1, the severity of ataxia strongly correlated with the degree of gray matter atrophy in cerebellar hemispheres. The duration of symptoms and lengths of CAG repeats had no correlation with the degree of atrophy. CONCLUSIONS This study showed that the different subtypes of SCAs may have morphometric differences in the cerebellum, brainstem and the supratentorial structures.
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Affiliation(s)
- Gaurav Goel
- Department of Neuroimaging and Interventional Radiology, National Institute of Mental Health & Neurosciences, Hosur Road, Bangalore, Karnataka, India
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Abstract
Trinucleotide expansion underlies several human diseases. Expansion occurs during multiple stages of human development in different cell types, and is sensitive to the gender of the parent who transmits the repeats. Repair and replication models for expansions have been described, but we do not know whether the pathway involved is the same under all conditions and for all repeat tract lengths, which differ among diseases. Currently, researchers rely on bacteria, yeast and mice to study expansion, but these models differ substantially from humans. We need now to connect the dots among human genetics, pathway biochemistry and the appropriate model systems to understand the mechanism of expansion as it occurs in human disease.
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Fork stalling and template switching as a mechanism for polyalanine tract expansion affecting the DYC mutant of HOXD13, a new murine model of synpolydactyly. Genetics 2009; 183:23-30. [PMID: 19546318 DOI: 10.1534/genetics.109.104695] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polyalanine expansion diseases are proposed to result from unequal crossover of sister chromatids that increases the number of repeats. In this report we suggest an alternative mechanism we put forward while we investigated a new spontaneous mutant that we named "Dyc" for "Digit in Y and Carpe" phenotype. Phenotypic analysis revealed an abnormal limb patterning similar to that of the human inherited congenital disease synpolydactyly (SPD) and to the mouse mutant model Spdh. Both human SPD and mouse Spdh mutations affect the Hoxd13 gene within a 15-residue polyalanine-encoding repeat in the first exon of the gene, leading to a dominant negative HOXD13. Genetic analysis of the Dyc mutant revealed a trinucleotide expansion in the polyalanine-encoding region of the Hoxd13 gene resulting in a 7-alanine expansion. However, unlike the Spdh mutation, this expansion cannot result from a simple duplication of a short segment. Instead, we propose the fork stalling and template switching (FosTeS) described for generation of nonrecurrent genomic rearrangements as a possible mechanism for the Dyc polyalanine extension, as well as for other polyalanine expansions described in the literature and that could not be explained by unequal crossing over.
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