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Abstract
At fifteen different genomic locations, the expansion of a CAG/CTG repeat causes a neurodegenerative or neuromuscular disease, the most common being Huntington's disease and myotonic dystrophy type 1. These disorders are characterized by germline and somatic instability of the causative CAG/CTG repeat mutations. Repeat lengthening, or expansion, in the germline leads to an earlier age of onset or more severe symptoms in the next generation. In somatic cells, repeat expansion is thought to precipitate the rate of disease. The mechanisms underlying repeat instability are not well understood. Here we review the mammalian model systems that have been used to study CAG/CTG repeat instability, and the modifiers identified in these systems. Mouse models have demonstrated prominent roles for proteins in the mismatch repair pathway as critical drivers of CAG/CTG instability, which is also suggested by recent genome-wide association studies in humans. We draw attention to a network of connections between modifiers identified across several systems that might indicate pathway crosstalk in the context of repeat instability, and which could provide hypotheses for further validation or discovery. Overall, the data indicate that repeat dynamics might be modulated by altering the levels of DNA metabolic proteins, their regulation, their interaction with chromatin, or by direct perturbation of the repeat tract. Applying novel methodologies and technologies to this exciting area of research will be needed to gain deeper mechanistic insight that can be harnessed for therapies aimed at preventing repeat expansion or promoting repeat contraction.
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Affiliation(s)
- 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,Correspondence to: Vanessa C. Wheeler, Center for Genomic Medicine, Massachusetts Hospital, Boston MAA 02115, USA. E-mail: . and Vincent Dion, UK Dementia Research Institute at Cardiff University, Hadyn Ellis Building, Maindy Road, CF24 4HQ Cardiff, UK. E-mail:
| | - Vincent Dion
- UK Dementia Research Institute at Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, UK,Correspondence to: Vanessa C. Wheeler, Center for Genomic Medicine, Massachusetts Hospital, Boston MAA 02115, USA. E-mail: . and Vincent Dion, UK Dementia Research Institute at Cardiff University, Hadyn Ellis Building, Maindy Road, CF24 4HQ Cardiff, UK. E-mail:
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Pattamatta A, Nguyen L, Olafson HR, Scotti MM, Laboissonniere LA, Richardson J, Berglund JA, Zu T, Wang ET, Ranum LPW. Repeat length increases disease penetrance and severity in C9orf72 ALS/FTD BAC transgenic mice. Hum Mol Genet 2020; 29:3900-3918. [PMID: 33378537 DOI: 10.1093/hmg/ddaa279] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/14/2020] [Accepted: 12/23/2020] [Indexed: 12/12/2022] Open
Abstract
C9orf72 ALS/FTD patients show remarkable clinical heterogeneity, but the complex biology of the repeat expansion mutation has limited our understanding of the disease. BAC transgenic mice were used to better understand the molecular mechanisms and repeat length effects of C9orf72 ALS/FTD. Genetic analyses of these mice demonstrate that the BAC transgene and not integration site effects cause ALS/FTD phenotypes. Transcriptomic changes in cell proliferation, inflammation and neuronal pathways are found late in disease and alternative splicing changes provide early molecular markers that worsen with disease progression. Isogenic sublines of mice with 800, 500 or 50 G4C2 repeats generated from the single-copy C9-500 line show longer repeats result in earlier onset, increased disease penetrance and increased levels of RNA foci and dipeptide RAN protein aggregates. These data demonstrate G4C2 repeat length is an important driver of disease and identify alternative splicing changes as early biomarkers of C9orf72 ALS/FTD.
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Affiliation(s)
- Amrutha Pattamatta
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Lien Nguyen
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Hailey R Olafson
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Marina M Scotti
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Lauren A Laboissonniere
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Jared Richardson
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA.,McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - J Andrew Berglund
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Biochemistry and Molecular Biology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,RNA Institute and Department of Biological Sciences, University at Albany, Albany, NY 12222, USA
| | - Tao Zu
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Eric T Wang
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA.,McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Laura P W Ranum
- Center for NeuroGenetics, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, Colllege of Medicine, University of Florida, Gainesville, FL 32610, USA.,University of Florida Genetics Institute, University of Florida, Gainesville, FL 32610, USA.,McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA.,Fixel Institute, University of Florida, Gainesville, FL 32610, USA
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Malbec R, Chami B, Aeschbach L, Ruiz Buendía GA, Socol M, Joseph P, Leïchlé T, Trofimenko E, Bancaud A, Dion V. µLAS: Sizing of expanded trinucleotide repeats with femtomolar sensitivity in less than 5 minutes. Sci Rep 2019; 9:23. [PMID: 30631115 PMCID: PMC6328573 DOI: 10.1038/s41598-018-36632-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 11/23/2018] [Indexed: 11/09/2022] Open
Abstract
We present µLAS, a lab-on-chip system that concentrates, separates, and detects DNA fragments in a single module. µLAS speeds up DNA size analysis in minutes using femtomolar amounts of amplified DNA. Here we tested the relevance of µLAS for sizing expanded trinucleotide repeats, which cause over 20 different neurological and neuromuscular disorders. Because the length of trinucleotide repeats correlates with the severity of the diseases, it is crucial to be able to size repeat tract length accurately and efficiently. Expanded trinucleotide repeats are however genetically unstable and difficult to amplify. Thus, the amount of amplified material to work with is often limited, making its analysis labor-intensive. We report the detection of heterogeneous allele lengths in 8 samples from myotonic dystrophy type 1 and Huntington disease patients with up to 750 CAG/CTG repeats in five minutes or less. The high sensitivity of the method allowed us to minimize the number of amplification cycles and thus reduce amplification artefacts without compromising the detection of the expanded allele. These results suggest that µLAS can speed up routine molecular biology applications of repetitive sequences and may improve the molecular diagnostic of expanded repeat disorders.
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Affiliation(s)
- Rémi Malbec
- LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, 31031, France
| | - Bayan Chami
- LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, 31031, France
| | - Lorène Aeschbach
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Bâtiment Génopode, Lausanne, 1015, Switzerland
| | - Gustavo A Ruiz Buendía
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Bâtiment Génopode, Lausanne, 1015, Switzerland
| | - Marius Socol
- LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, 31031, France
| | - Pierre Joseph
- LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, 31031, France
| | - Thierry Leïchlé
- LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, 31031, France
| | - Evgeniya Trofimenko
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Bâtiment Génopode, Lausanne, 1015, Switzerland
- Department of Physiology, University of Lausanne, Rue du Bugnon 7, Lausanne, 1005, Switzerland
| | - Aurélien Bancaud
- LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, 31031, France.
| | - Vincent Dion
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Bâtiment Génopode, Lausanne, 1015, Switzerland.
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