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Kunoh S, Nakashima H, Nakashima K. Epigenetic Regulation of Neural Stem Cells in Developmental and Adult Stages. EPIGENOMES 2024; 8:22. [PMID: 38920623 PMCID: PMC11203245 DOI: 10.3390/epigenomes8020022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 05/18/2024] [Accepted: 05/31/2024] [Indexed: 06/27/2024] Open
Abstract
The development of the nervous system is regulated by numerous intracellular molecules and cellular signals that interact temporally and spatially with the extracellular microenvironment. The three major cell types in the brain, i.e., neurons and two types of glial cells (astrocytes and oligodendrocytes), are generated from common multipotent neural stem cells (NSCs) throughout life. However, NSCs do not have this multipotentiality from the beginning. During cortical development, NSCs sequentially obtain abilities to differentiate into neurons and glial cells in response to combinations of spatiotemporally modulated cell-intrinsic epigenetic alterations and extrinsic factors. After the completion of brain development, a limited population of NSCs remains in the adult brain and continues to produce neurons (adult neurogenesis), thus contributing to learning and memory. Many biological aspects of brain development and adult neurogenesis are regulated by epigenetic changes via behavioral control of NSCs. Epigenetic dysregulation has also been implicated in the pathogenesis of various brain diseases. Here, we present recent advances in the epigenetic regulation of NSC behavior and its dysregulation in brain disorders.
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Affiliation(s)
| | - Hideyuki Nakashima
- Department of Stem Cell Biology and Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan;
| | - Kinichi Nakashima
- Department of Stem Cell Biology and Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan;
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2
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Calluori S, Stark R, Pearson BL. Gene-Environment Interactions in Repeat Expansion Diseases: Mechanisms of Environmentally Induced Repeat Instability. Biomedicines 2023; 11:515. [PMID: 36831049 PMCID: PMC9953593 DOI: 10.3390/biomedicines11020515] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 02/06/2023] [Accepted: 02/07/2023] [Indexed: 02/12/2023] Open
Abstract
Short tandem repeats (STRs) are units of 1-6 base pairs that occur in tandem repetition to form a repeat tract. STRs exhibit repeat instability, which generates expansions or contractions of the repeat tract. Over 50 diseases, primarily affecting the central nervous system and muscles, are characterized by repeat instability. Longer repeat tracts are typically associated with earlier age of onset and increased disease severity. Environmental exposures are suspected to play a role in the pathogenesis of repeat expansion diseases. Here, we review the current knowledge of mechanisms of environmentally induced repeat instability in repeat expansion diseases. The current evidence demonstrates that environmental factors modulate repeat instability via DNA damage and induction of DNA repair pathways, with distinct mechanisms for repeat expansion and contraction. Of particular note, oxidative stress is a key mediator of environmentally induced repeat instability. The preliminary evidence suggests epigenetic modifications as potential mediators of environmentally induced repeat instability. Future research incorporating an array of environmental exposures, new human cohorts, and improved model systems, with a continued focus on cell-types, tissues, and critical windows, will aid in identifying mechanisms of environmentally induced repeat instability. Identifying environmental modulators of repeat instability and their mechanisms of action will inform preventions, therapies, and public health measures.
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Affiliation(s)
- Stephanie Calluori
- Department of Environmental Health Sciences, Mailman School of Public Health Columbia University, New York, NY 10032, USA
- Barnard College of Columbia University, 3009 Broadway, New York, NY 10027, USA
| | - Rebecca Stark
- Department of Environmental Health Sciences, Mailman School of Public Health Columbia University, New York, NY 10032, USA
| | - Brandon L. Pearson
- Department of Environmental Health Sciences, Mailman School of Public Health Columbia University, New York, NY 10032, USA
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3
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de Pontual L, Tomé S. Overview of the Complex Relationship between Epigenetics Markers, CTG Repeat Instability and Symptoms in Myotonic Dystrophy Type 1. Int J Mol Sci 2022; 23:ijms23073477. [PMID: 35408837 PMCID: PMC8998570 DOI: 10.3390/ijms23073477] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 03/14/2022] [Accepted: 03/16/2022] [Indexed: 02/05/2023] Open
Abstract
Among the trinucleotide repeat disorders, myotonic dystrophy type 1 (DM1) is one of the most complex neuromuscular diseases caused by an unstable CTG repeat expansion in the DMPK gene. DM1 patients exhibit high variability in the dynamics of CTG repeat instability and in the manifestations and progression of the disease. The largest expanded alleles are generally associated with the earliest and most severe clinical form. However, CTG repeat length alone is not sufficient to predict disease severity and progression, suggesting the involvement of other factors. Several data support the role of epigenetic alterations in clinical and genetic variability. By highlighting epigenetic alterations in DM1, this review provides a new avenue on how these changes can serve as biomarkers to predict clinical features and the mutation behavior.
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Affiliation(s)
| | - Stéphanie Tomé
- Correspondence: ; Tel.: +33-1-42-16-57-16; Fax: +33-1-42-16-57-00
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4
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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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5
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Adampourezare M, Dehghan G, Hasanzadeh M, Hosseinpoure Feizi MA. Application of lateral flow and microfluidic bio-assay and biosensing towards identification of DNA-methylation and cancer detection: Recent progress and challenges in biomedicine. Biomed Pharmacother 2021; 141:111845. [PMID: 34175816 DOI: 10.1016/j.biopha.2021.111845] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 06/16/2021] [Accepted: 06/16/2021] [Indexed: 02/06/2023] Open
Abstract
DNA methylation is an important epigenetic alteration that results from the covalent transfer of a methyl group to the fifth carbon of a cytosine residue in CpG dinucleotides by DNA methyltransferase. This modification mostly happens in the promoter region and the first exon of most genes and suppresses gene expression. Therefore, aberrant DNA methylation cause tumor progression, metastasis, and resistance to current anti-cancer therapies. So, the detection of DNA methylation is an important issue in diagnosis and therapy of most diseases. Conventional methods for the assay of DNA methylation and activity of DNA methyltransferases are time consuming. So, we need to multiplex operations and expensive instrumentation. To overcome the limitations of conventional methods, new methods such as microfluidic platforms and lateral flow tests have been developed to evaluate DNA methylation. The microfluidic tests are based on optical and electrical biosensing. These tests able us to can analyze DNA methylation with high efficiency and sensitivity without the need for expensive equipment and skilled people. Lateral flow strip tests are another type of rapid, simple, and sensitive test with advanced technology used to assess DNA methylation. Lateral flow strip tests are based on optical biosensors. This review attempts to evaluate new methods for assessing DNA extraction, DNA methylation and DNA methyltransferase activity as well as recent developments in microfluidic technology application for bisulfite treatment and restriction enzyme (bisulfite free), and lateral flow relying on their application in the field of recognition of DNA methylation in blood and body fluids. Also, the advantages and disadvantages of each test are reviewed. Finally, future prospects for the development of the microfluidics biodevices for the detection of DNA methylation is briefly discussed.
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Affiliation(s)
- Mina Adampourezare
- Department of Animal Biology, Faculty of Natural Science, University of Tabriz, Tabriz, Iran; Pharmaceutical Analysis Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Gholamreza Dehghan
- Department of Animal Biology, Faculty of Natural Science, University of Tabriz, Tabriz, Iran.
| | - Mohammad Hasanzadeh
- Pharmaceutical Analysis Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
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Hyeon JW, Kim AH, Yano H. Epigenetic regulation in Huntington's disease. Neurochem Int 2021; 148:105074. [PMID: 34038804 DOI: 10.1016/j.neuint.2021.105074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 04/23/2021] [Accepted: 05/17/2021] [Indexed: 12/25/2022]
Abstract
Huntington's disease (HD) is a devastating and fatal monogenic neurodegenerative disorder characterized by progressive loss of selective neurons in the brain and is caused by an abnormal expansion of CAG trinucleotide repeats in a coding exon of the huntingtin (HTT) gene. Progressive gene expression changes that begin at premanifest stages are a prominent feature of HD and are thought to contribute to disease progression. Increasing evidence suggests the critical involvement of epigenetic mechanisms in abnormal transcription in HD. Genome-wide alterations of a number of epigenetic modifications, including DNA methylation and multiple histone modifications, are associated with HD, suggesting that mutant HTT causes complex epigenetic abnormalities and chromatin structural changes, which may represent an underlying pathogenic mechanism. The causal relationship of specific epigenetic changes to early transcriptional alterations and to disease pathogenesis require further investigation. In this article, we review recent studies on epigenetic regulation in HD with a focus on DNA and histone modifications. We also discuss the contribution of epigenetic modifications to HD pathogenesis as well as potential mechanisms linking mutant HTT and epigenetic alterations. Finally, we discuss the therapeutic potential of epigenetic-based treatments.
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Affiliation(s)
- Jae Wook Hyeon
- Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Albert H Kim
- Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO, 63110, USA; Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA; Department of Genetics, Washington University School of Medicine, St. Louis, MO, 63110, USA; Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA; Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Hiroko Yano
- Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO, 63110, USA; Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA; Department of Genetics, Washington University School of Medicine, St. Louis, MO, 63110, USA; Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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7
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Kovalenko M, Erdin S, Andrew MA, St Claire J, Shaughnessey M, Hubert L, Neto JL, Stortchevoi A, Fass DM, Mouro Pinto R, Haggarty SJ, Wilson JH, Talkowski ME, Wheeler VC. Histone deacetylase knockouts modify transcription, CAG instability and nuclear pathology in Huntington disease mice. eLife 2020; 9:55911. [PMID: 32990597 PMCID: PMC7581428 DOI: 10.7554/elife.55911] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 09/28/2020] [Indexed: 12/13/2022] Open
Abstract
Somatic expansion of the Huntington’s disease (HD) CAG repeat drives the rate of a pathogenic process ultimately resulting in neuronal cell death. Although mechanisms of toxicity are poorly delineated, transcriptional dysregulation is a likely contributor. To identify modifiers that act at the level of CAG expansion and/or downstream pathogenic processes, we tested the impact of genetic knockout, in HttQ111 mice, of Hdac2 or Hdac3 in medium-spiny striatal neurons that exhibit extensive CAG expansion and exquisite disease vulnerability. Both knockouts moderately attenuated CAG expansion, with Hdac2 knockout decreasing nuclear huntingtin pathology. Hdac2 knockout resulted in a substantial transcriptional response that included modification of transcriptional dysregulation elicited by the HttQ111 allele, likely via mechanisms unrelated to instability suppression. Our results identify novel modifiers of different aspects of HD pathogenesis in medium-spiny neurons and highlight a complex relationship between the expanded Htt allele and Hdac2 with implications for targeting transcriptional dysregulation in HD.
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Affiliation(s)
- Marina Kovalenko
- Center for Genomic Medicine, Harvard Medical School, Boston, United States
| | - Serkan Erdin
- Center for Genomic Medicine, Harvard Medical School, Boston, United States.,Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, United States
| | - Marissa A Andrew
- Center for Genomic Medicine, Harvard Medical School, Boston, United States
| | - Jason St Claire
- Center for Genomic Medicine, Harvard Medical School, Boston, United States
| | | | - Leroy Hubert
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, United States
| | - João Luís Neto
- Center for Genomic Medicine, Harvard Medical School, Boston, United States
| | - Alexei Stortchevoi
- Center for Genomic Medicine, Harvard Medical School, Boston, United States
| | - Daniel M Fass
- Center for Genomic Medicine, Harvard Medical School, Boston, United States
| | - Ricardo Mouro Pinto
- Center for Genomic Medicine, Harvard Medical School, Boston, United States.,Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, United States
| | - Stephen J Haggarty
- Center for Genomic Medicine, Harvard Medical School, Boston, United States.,Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, United States
| | - John H Wilson
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, United States
| | - Michael E Talkowski
- Center for Genomic Medicine, Harvard Medical School, Boston, United States.,Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, United States.,Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, United States
| | - Vanessa C Wheeler
- Center for Genomic Medicine, Harvard Medical School, Boston, United States.,Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, United States
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8
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Cinesi C, Yang B, Dion V. GFP Reporters to Monitor Instability and Expression of Expanded CAG/CTG Repeats. Methods Mol Biol 2020; 2056:255-268. [PMID: 31586353 DOI: 10.1007/978-1-4939-9784-8_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Expanded CAG/CTG repeats are genetically unstable and, upon expression, cause neurological and neuromuscular diseases. The molecular mechanisms of repeat instability and expression remain poorly understood despite their importance for the pathogenesis of a family of 14 devastating human diseases. This is in part because conventional assays are tedious and time-consuming. Recently, however, GFP-based reporters have been designed to provide a rapid and reliable means of assessing these parameters. Here we provide protocols for quantifying repeat instability and expression using a GFP-based chromosomal reporter and the newly developed ParB/ANCHOR-mediated Inducible Targeting (PInT) and how to validate the results.
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Affiliation(s)
- Cinzia Cinesi
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Bin Yang
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Vincent Dion
- Dementia Research Institute, Cardiff University, Cardiff, UK.
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9
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Légaré C, Overend G, Guay SP, Monckton DG, Mathieu J, Gagnon C, Bouchard L. DMPK gene DNA methylation levels are associated with muscular and respiratory profiles in DM1. NEUROLOGY-GENETICS 2019; 5:e338. [PMID: 31334355 PMCID: PMC6568328 DOI: 10.1212/nxg.0000000000000338] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 04/03/2019] [Accepted: 04/04/2019] [Indexed: 12/03/2022]
Abstract
Objective To assess the effects of dystrophia myotonica protein kinase (DMPK) DNA methylation (DNAme) epivariation on muscular and respiratory profiles in patients with myotonic dystrophy type 1 (DM1). Methods Phenotypes were assessed with standardized measures. Pyrosequencing of bisulfite-treated DNA was used to quantify DNAme levels in blood from 90 patients with DM1 (adult form). Modal CTG repeat length was assessed using small-pool PCR. The presence of Acil-sensitive variant repeats was also tested. Results DNAme levels upstream of the CTG expansion (exon and intron 11) were correlated with modal CTG repeat length (rs = −0.224, p = 0.040; rs = −0.317, p = 0.003; and rs = −0.241, p = 0.027), whereas correlations were observed with epivariations downstream of the CTG repeats (rs = 0.227; p = 0.037). The presence of a variant repeat was associated with higher DNAme levels at multiple CpG sites (up to 10% higher; p = 0.001). Stepwise multiple linear regression modeling showed that DNAme contributed significantly and independently to explain phenotypic variability in ankle dorsiflexor (3 CpGs: p = 0.001, 0.013, and 0.001), grip (p = 0.089), and pinch (p = 0.028) strengths and in forced vital capacity (2 CpGs: p = 0.002 and 0.021) and maximal inspiratory pressure (p = 0.012). Conclusions In addition to the CTG repeat length, DMPK epivariations independently explain phenotypic variability in DM1 and could thus improve prognostic accuracy for patients.
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Affiliation(s)
- Cécilia Légaré
- Department of Biochemistry (C.L., S.-P.G., L.B.), Université de Sherbrooke, Sherbrooke; ECOGENE-21 Biocluster (C.L., S.-P.G., L.B.), Chicoutimi, Québec, Canada; Groupe de Recherche interdisciplinaire sur les maladies neuromusculaires (C.L., J.M., C.G., L.B.), Saguenay, Canada; Institute of Molecular (G.O., D.G.M.), Cell and Systems Biology, University of Glasgow, United Kingdom; and Centre de Recherche Charles-Le-Moyne-Saguenay-Lac-StJean sur les innovations en santé (J.M., C.G.), Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
| | - Gayle Overend
- Department of Biochemistry (C.L., S.-P.G., L.B.), Université de Sherbrooke, Sherbrooke; ECOGENE-21 Biocluster (C.L., S.-P.G., L.B.), Chicoutimi, Québec, Canada; Groupe de Recherche interdisciplinaire sur les maladies neuromusculaires (C.L., J.M., C.G., L.B.), Saguenay, Canada; Institute of Molecular (G.O., D.G.M.), Cell and Systems Biology, University of Glasgow, United Kingdom; and Centre de Recherche Charles-Le-Moyne-Saguenay-Lac-StJean sur les innovations en santé (J.M., C.G.), Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
| | - Simon-Pierre Guay
- Department of Biochemistry (C.L., S.-P.G., L.B.), Université de Sherbrooke, Sherbrooke; ECOGENE-21 Biocluster (C.L., S.-P.G., L.B.), Chicoutimi, Québec, Canada; Groupe de Recherche interdisciplinaire sur les maladies neuromusculaires (C.L., J.M., C.G., L.B.), Saguenay, Canada; Institute of Molecular (G.O., D.G.M.), Cell and Systems Biology, University of Glasgow, United Kingdom; and Centre de Recherche Charles-Le-Moyne-Saguenay-Lac-StJean sur les innovations en santé (J.M., C.G.), Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
| | - Darren G Monckton
- Department of Biochemistry (C.L., S.-P.G., L.B.), Université de Sherbrooke, Sherbrooke; ECOGENE-21 Biocluster (C.L., S.-P.G., L.B.), Chicoutimi, Québec, Canada; Groupe de Recherche interdisciplinaire sur les maladies neuromusculaires (C.L., J.M., C.G., L.B.), Saguenay, Canada; Institute of Molecular (G.O., D.G.M.), Cell and Systems Biology, University of Glasgow, United Kingdom; and Centre de Recherche Charles-Le-Moyne-Saguenay-Lac-StJean sur les innovations en santé (J.M., C.G.), Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
| | - Jean Mathieu
- Department of Biochemistry (C.L., S.-P.G., L.B.), Université de Sherbrooke, Sherbrooke; ECOGENE-21 Biocluster (C.L., S.-P.G., L.B.), Chicoutimi, Québec, Canada; Groupe de Recherche interdisciplinaire sur les maladies neuromusculaires (C.L., J.M., C.G., L.B.), Saguenay, Canada; Institute of Molecular (G.O., D.G.M.), Cell and Systems Biology, University of Glasgow, United Kingdom; and Centre de Recherche Charles-Le-Moyne-Saguenay-Lac-StJean sur les innovations en santé (J.M., C.G.), Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
| | - Cynthia Gagnon
- Department of Biochemistry (C.L., S.-P.G., L.B.), Université de Sherbrooke, Sherbrooke; ECOGENE-21 Biocluster (C.L., S.-P.G., L.B.), Chicoutimi, Québec, Canada; Groupe de Recherche interdisciplinaire sur les maladies neuromusculaires (C.L., J.M., C.G., L.B.), Saguenay, Canada; Institute of Molecular (G.O., D.G.M.), Cell and Systems Biology, University of Glasgow, United Kingdom; and Centre de Recherche Charles-Le-Moyne-Saguenay-Lac-StJean sur les innovations en santé (J.M., C.G.), Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
| | - Luigi Bouchard
- Department of Biochemistry (C.L., S.-P.G., L.B.), Université de Sherbrooke, Sherbrooke; ECOGENE-21 Biocluster (C.L., S.-P.G., L.B.), Chicoutimi, Québec, Canada; Groupe de Recherche interdisciplinaire sur les maladies neuromusculaires (C.L., J.M., C.G., L.B.), Saguenay, Canada; Institute of Molecular (G.O., D.G.M.), Cell and Systems Biology, University of Glasgow, United Kingdom; and Centre de Recherche Charles-Le-Moyne-Saguenay-Lac-StJean sur les innovations en santé (J.M., C.G.), Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
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Teijido O, Cacabelos R. Pharmacoepigenomic Interventions as Novel Potential Treatments for Alzheimer's and Parkinson's Diseases. Int J Mol Sci 2018; 19:E3199. [PMID: 30332838 PMCID: PMC6213964 DOI: 10.3390/ijms19103199] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 10/05/2018] [Accepted: 10/08/2018] [Indexed: 12/22/2022] Open
Abstract
Cerebrovascular and neurodegenerative disorders affect one billion people around the world and result from a combination of genomic, epigenomic, metabolic, and environmental factors. Diagnosis at late stages of disease progression, limited knowledge of gene biomarkers and molecular mechanisms of the pathology, and conventional compounds based on symptomatic rather than mechanistic features, determine the lack of success of current treatments, including current FDA-approved conventional drugs. The epigenetic approach opens new avenues for the detection of early presymptomatic pathological events that would allow the implementation of novel strategies in order to stop or delay the pathological process. The reversibility and potential restoring of epigenetic aberrations along with their potential use as targets for pharmacological and dietary interventions sited the use of epidrugs as potential novel candidates for successful treatments of multifactorial disorders involving neurodegeneration. This manuscript includes a description of the most relevant epigenetic mechanisms involved in the most prevalent neurodegenerative disorders worldwide, as well as the main potential epigenetic-based compounds under investigation for treatment of those disorders and their limitations.
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Affiliation(s)
- Oscar Teijido
- EuroEspes Biomedical Research Center, Institute of Medical Science and Genomic Medicine, 15165 La Coruña, Spain.
| | - Ramón Cacabelos
- EuroEspes Biomedical Research Center, Institute of Medical Science and Genomic Medicine, 15165 La Coruña, Spain.
- Chair of Genomic Medicine, Continental University Medical School, Huancayo 12000, Peru.
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11
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Sun N, Zhang J, Zhang C, Zhao B, Jiao A. DNMTs inhibitor SGI-1027 induces apoptosis in Huh7 human hepatocellular carcinoma cells. Oncol Lett 2018; 16:5799-5806. [PMID: 30344731 PMCID: PMC6176375 DOI: 10.3892/ol.2018.9390] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 08/14/2018] [Indexed: 01/14/2023] Open
Abstract
SGI-1027, a novel class of relatively stable, highly lipophilic quinoline-based small-molecule inhibitors of DNA methyltransferase enzymes (DNMTs), is able to inhibit DNMTs activity, and reactivate tumor suppressor genes. However, the potential anticancer mechanisms of SGI-1027 on human hepatocellular carcinoma (HCC) cells are still not clearly understood. Thus, the objective of the present study was to clarify the inhibitory effect of SGI-1027 on the cell cycle and apoptosis of the Huh7 cell line. The results revealed that treatment with SGI-1027 resulted in a significant dose-dependent decrease in cell viability. Flow cytometric analysis identified that a 24 h treatment of SGI-1027 resulted in cell apoptosis, and typical apoptotic nucleic alterations were observed with fluorescence microscopy following terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling staining. Immunoblot analysis further demonstrated that SGI-1027 downregulated the expression of B cell lymphoma-2 and upregulated the expression of Bcl-associated X protein. However, no significant alterations of the cell cycle phases were observed. Overall, it is demonstrated that SGI-1027 causes cell apoptosis via the mitochondrial-mediated pathway, which advances current understanding of the molecular mechanisms of SGI-1027 in HCC management.
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Affiliation(s)
- Ning Sun
- Department of Hepatobiliary and Transplantation Surgery, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Jialin Zhang
- Department of Hepatobiliary and Transplantation Surgery, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Chengshuo Zhang
- Department of Hepatobiliary and Transplantation Surgery, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Bochao Zhao
- Department of Hepatobiliary and Transplantation Surgery, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Ao Jiao
- Department of Hepatobiliary and Transplantation Surgery, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
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12
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Santoro M, Fontana L, Maiorca F, Centofanti F, Massa R, Silvestri G, Novelli G, Botta A. Expanded [CCTG]n repetitions are not associated with abnormal methylation at the CNBP locus in myotonic dystrophy type 2 (DM2) patients. Biochim Biophys Acta Mol Basis Dis 2018; 1864:917-924. [DOI: 10.1016/j.bbadis.2017.12.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 12/21/2017] [Accepted: 12/28/2017] [Indexed: 01/10/2023]
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13
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The Chromatin Remodeler Isw1 Prevents CAG Repeat Expansions During Transcription in Saccharomyces cerevisiae. Genetics 2018; 208:963-976. [PMID: 29305386 PMCID: PMC5844344 DOI: 10.1534/genetics.117.300529] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Accepted: 01/02/2018] [Indexed: 12/23/2022] Open
Abstract
CAG/CTG trinucleotide repeat expansions cause several degenerative neurological and muscular diseases. Koch et al. show that the chromatin remodeling... CAG/CTG trinucleotide repeats are unstable sequences that are difficult to replicate, repair, and transcribe due to their structure-forming nature. CAG repeats strongly position nucleosomes; however, little is known about the chromatin remodeling needed to prevent repeat instability. In a Saccharomyces cerevisiae model system with CAG repeats carried on a YAC, we discovered that the chromatin remodeler Isw1 is required to prevent CAG repeat expansions during transcription. CAG repeat expansions in the absence of Isw1 were dependent on both transcription-coupled repair (TCR) and base-excision repair (BER). Furthermore, isw1∆ mutants are sensitive to methyl methanesulfonate (MMS) and exhibit synergistic MMS sensitivity when combined with BER or TCR pathway mutants. We conclude that CAG expansions in the isw1∆ mutant occur during a transcription-coupled excision repair process that involves both TCR and BER pathways. We observed increased RNA polymerase II (RNAPII) occupancy at the CAG repeat when transcription of the repeat was induced, but RNAPII binding did not change in isw1∆ mutants, ruling out a role for Isw1 remodeling in RNAPII progression. However, nucleosome occupancy over a transcribed CAG tract was altered in isw1∆ mutants. Based on the known role of Isw1 in the reestablishment of nucleosomal spacing after transcription, we suggest that a defect in this function allows DNA structures to form within repetitive DNA tracts, resulting in inappropriate excision repair and repeat-length changes. These results establish a new function for Isw1 in directly maintaining the chromatin structure at the CAG repeat, thereby limiting expansions that can occur during transcription-coupled excision repair.
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14
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Wang C, Peng H, Li J, Ding D, Chen Z, Long Z, Peng Y, Zhou X, Ye W, Li K, Xu Q, Ai S, Song C, Weng L, Qiu R, Xia K, Tang B, Jiang H. Alteration of methylation status in the ATXN3 gene promoter region is linked to the SCA3/MJD. Neurobiol Aging 2017; 53:192.e5-192.e10. [DOI: 10.1016/j.neurobiolaging.2016.12.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 11/14/2016] [Accepted: 12/11/2016] [Indexed: 12/13/2022]
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15
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Wang KY, Chen CC, Tsai SF, Shen CKJ. Epigenetic Enhancement of the Post-replicative DNA Mismatch Repair of Mammalian Genomes by a Hemi- mCpG-Np95-Dnmt1 Axis. Sci Rep 2016; 6:37490. [PMID: 27886214 PMCID: PMC5122852 DOI: 10.1038/srep37490] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 10/26/2016] [Indexed: 01/02/2023] Open
Abstract
DNA methylation at C of CpG dyads (mCpG) in vertebrate genomes is essential for gene regulation, genome stability and development. We show in this study that proper functioning of post-replicative DNA mismatch repair (MMR) in mammalian cells relies on the presence of genomic mCpG, as well as on the maintenance DNA methyltransferase Dnmt1 independently of its catalytic activity. More importantly, high efficiency of mammalian MMR surveillance is achieved through a hemi-mCpG-Np95(Uhrf1)-Dnmt1 axis, in which the MMR surveillance complex(es) is recruited to post-replicative DNA by Dnmt1, requiring its interactions with MutSα, as well as with Np95 bound at the hemi-methylated CpG sites. Thus, efficiency of MMR surveillance over the mammalian genome in vivo is enhanced at the epigenetic level. This synergy endows vertebrate CpG methylation with a new biological significance and, consequently, an additional mechanism for the maintenance of vertebrate genome stability.
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Affiliation(s)
- Keh-Yang Wang
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Chun-Chang Chen
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Shih-Feng Tsai
- Genome Research Center, National Yang-Ming University, Taipei 11221, Taiwan.,Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan.,Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli 35053, Taiwan
| | - Che-Kun James Shen
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 11529, Taiwan
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16
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Grzybek M, Golonko A, Walczak M, Lisowski P. Epigenetics of cell fate reprogramming and its implications for neurological disorders modelling. Neurobiol Dis 2016; 99:84-120. [PMID: 27890672 DOI: 10.1016/j.nbd.2016.11.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 11/03/2016] [Accepted: 11/21/2016] [Indexed: 02/06/2023] Open
Abstract
The reprogramming of human induced pluripotent stem cells (hiPSCs) proceeds in a stepwise manner with reprogramming factors binding and epigenetic composition changes during transition to maintain the epigenetic landscape, important for pluripotency. There arises a question as to whether the aberrant epigenetic state after reprogramming leads to epigenetic defects in induced stem cells causing unpredictable long term effects in differentiated cells. In this review, we present a comprehensive view of epigenetic alterations accompanying reprogramming, cell maintenance and differentiation as factors that influence applications of hiPSCs in stem cell based technologies. We conclude that sample heterogeneity masks DNA methylation signatures in subpopulations of cells and thus believe that beside a genetic evaluation, extensive epigenomic screening should become a standard procedure to ensure hiPSCs state before they are used for genome editing and differentiation into neurons of interest. In particular, we suggest that exploitation of the single-cell composition of the epigenome will provide important insights into heterogeneity within hiPSCs subpopulations to fast forward development of reliable hiPSC-based analytical platforms in neurological disorders modelling and before completed hiPSC technology will be implemented in clinical approaches.
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Affiliation(s)
- Maciej Grzybek
- Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Akademicka 12, 20-950 Lublin, Poland; Department of Molecular Biology, Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzębiec, Postępu 36A, 05-552 Magdalenka, Poland.
| | - Aleksandra Golonko
- Department of Biotechnology, Faculty of Civil and Environmental Engineering, Bialystok University of Technology, Wiejska 45E, 15-351 Bialystok, Poland.
| | - Marta Walczak
- Department of Animal Behavior, Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzębiec, Postępu 36A, 05-552 Magdalenka, Poland.
| | - Pawel Lisowski
- Department of Molecular Biology, Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzębiec, Postępu 36A, 05-552 Magdalenka, Poland; iPS Cell-Based Disease Modelling Group, Max Delbrück Center for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Rössle-Str. 10, 13092 Berlin, Germany.
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17
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Mollica PA, Reid JA, Ogle RC, Sachs PC, Bruno RD. DNA Methylation Leads to DNA Repair Gene Down-Regulation and Trinucleotide Repeat Expansion in Patient-Derived Huntington Disease Cells. THE AMERICAN JOURNAL OF PATHOLOGY 2016; 186:1967-1976. [DOI: 10.1016/j.ajpath.2016.03.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 03/14/2016] [Accepted: 03/16/2016] [Indexed: 12/12/2022]
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18
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Yao B, Christian KM, He C, Jin P, Ming GL, Song H. Epigenetic mechanisms in neurogenesis. Nat Rev Neurosci 2016; 17:537-49. [PMID: 27334043 DOI: 10.1038/nrn.2016.70] [Citation(s) in RCA: 258] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In the embryonic and adult brain, neural stem cells proliferate and give rise to neurons and glia through highly regulated processes. Epigenetic mechanisms - including DNA and histone modifications, as well as regulation by non-coding RNAs - have pivotal roles in different stages of neurogenesis. Aberrant epigenetic regulation also contributes to the pathogenesis of various brain disorders. Here, we review recent advances in our understanding of epigenetic regulation in neurogenesis and its dysregulation in brain disorders, including discussion of newly identified DNA cytosine modifications. We also briefly cover the emerging field of epitranscriptomics, which involves modifications of mRNAs and long non-coding RNAs.
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Affiliation(s)
- Bing Yao
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, Georgia 30322, USA
| | - Kimberly M Christian
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA
| | - Chuan He
- Department of Chemistry, Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA.,Howard Hughes Medical Institute, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA
| | - Peng Jin
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, Georgia 30322, USA
| | - Guo-Li Ming
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA.,The Solomon Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA.,Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA
| | - Hongjun Song
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA.,The Solomon Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA
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19
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Ferlazzo ML, Foray N. Huntington Disease: A Disease of DNA Methylation or DNA Breaks? THE AMERICAN JOURNAL OF PATHOLOGY 2016; 186:1750-1753. [PMID: 27219493 DOI: 10.1016/j.ajpath.2016.05.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 05/05/2016] [Accepted: 05/10/2016] [Indexed: 12/01/2022]
Abstract
This commentary highlights the article by Mollica et al that describes an interesting model for the clinical evolution of Huntington disease.
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Affiliation(s)
- Mélanie L Ferlazzo
- INSERM, UMR 1052, Radiobiology Group, Cancer Research Centre of Lyon, Lyon, France
| | - Nicolas Foray
- INSERM, UMR 1052, Radiobiology Group, Cancer Research Centre of Lyon, Lyon, France.
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20
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Essebier A, Vera Wolf P, Cao MD, Carroll BJ, Balasubramanian S, Bodén M. Statistical Enrichment of Epigenetic States Around Triplet Repeats that Can Undergo Expansions. Front Neurosci 2016; 10:92. [PMID: 27013954 PMCID: PMC4782033 DOI: 10.3389/fnins.2016.00092] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 02/23/2016] [Indexed: 12/18/2022] Open
Abstract
More than 30 human genetic diseases are linked to tri-nucleotide repeat expansions. There is no known mechanism that explains repeat expansions in full, but changes in the epigenetic state of the associated locus has been implicated in the disease pathology for a growing number of examples. A comprehensive comparative analysis of the genomic features associated with diverse repeat expansions has been lacking. Here, in an effort to decipher the propensity of repeats to undergo expansion and result in a disease state, we determine the genomic coordinates of tri-nucleotide repeat tracts at base pair resolution and computationally establish epigenetic profiles around them. Using three complementary statistical tests, we reveal that several epigenetic states are enriched around repeats that are associated with disease, even in cells that do not harbor expansion, relative to a carefully stratified background. Analysis of over one hundred cell types reveals that epigenetic states generally tend to vary widely between genic regions and cell types. However, there is qualified consistency in the epigenetic signatures of repeats associated with disease suggesting that changes to the chromatin and the DNA around an expanding repeat locus are likely to be similar. These epigenetic signatures may be exploited further to develop models that could explain the propensity of repeats to undergo expansions.
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Affiliation(s)
- Alexandra Essebier
- School of Chemistry and Molecular Biosciences, The University of Queensland St Lucia, QLD, Australia
| | - Patricia Vera Wolf
- School of Chemistry and Molecular Biosciences, The University of Queensland St Lucia, QLD, Australia
| | - Minh Duc Cao
- School of Chemistry and Molecular Biosciences, The University of Queensland St Lucia, QLD, Australia
| | - Bernard J Carroll
- School of Chemistry and Molecular Biosciences, The University of Queensland St Lucia, QLD, Australia
| | | | - Mikael Bodén
- School of Chemistry and Molecular Biosciences, The University of Queensland St Lucia, QLD, Australia
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21
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Mirabella AC, Foster BM, Bartke T. Chromatin deregulation in disease. Chromosoma 2016; 125:75-93. [PMID: 26188466 PMCID: PMC4761009 DOI: 10.1007/s00412-015-0530-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 06/30/2015] [Accepted: 07/02/2015] [Indexed: 12/21/2022]
Abstract
The regulation of chromatin by epigenetic mechanisms plays a central role in gene expression and is essential for development and maintenance of cell identity and function. Aberrant chromatin regulation is observed in many diseases where it leads to defects in epigenetic gene regulation resulting in pathological gene expression programmes. These defects are caused by inherited or acquired mutations in genes encoding enzymes that deposit or remove DNA and histone modifications and that shape chromatin architecture. Chromatin deregulation often results in neurodevelopmental disorders and intellectual disabilities, frequently linked to physical and developmental abnormalities, but can also cause neurodegenerative diseases, immunodeficiency, or muscle wasting syndromes. Epigenetic diseases can either be of monogenic origin or manifest themselves as complex multifactorial diseases such as in congenital heart disease, autism spectrum disorders, or cancer in which mutations in chromatin regulators are contributing factors. The environment directly influences the epigenome and can induce changes that cause or predispose to diseases through risk factors such as stress, malnutrition or exposure to harmful chemicals. The plasticity of chromatin regulation makes targeting the enzymatic machinery an attractive strategy for therapeutic intervention and an increasing number of small molecule inhibitors against a variety of epigenetic regulators are in clinical use or under development. In this review, we will give an overview of the molecular lesions that underlie epigenetic diseases, and we will discuss the impact of the environment and prospects for epigenetic therapies.
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Affiliation(s)
- Anne C Mirabella
- Chromatin Biochemistry Group, MRC Clinical Sciences Centre, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Benjamin M Foster
- Chromatin Biochemistry Group, MRC Clinical Sciences Centre, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Till Bartke
- Chromatin Biochemistry Group, MRC Clinical Sciences Centre, Imperial College London, Du Cane Road, London, W12 0NN, UK.
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22
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Engineered Nucleases and Trinucleotide Repeat Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016. [DOI: 10.1007/978-1-4939-3509-3_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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23
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Nageshwaran S, Festenstein R. Epigenetics and Triplet-Repeat Neurological Diseases. Front Neurol 2015; 6:262. [PMID: 26733936 PMCID: PMC4685448 DOI: 10.3389/fneur.2015.00262] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 11/30/2015] [Indexed: 01/15/2023] Open
Abstract
The term "junk DNA" has been reconsidered following the delineation of the functional significance of repetitive DNA regions. Typically associated with centromeres and telomeres, DNA repeats are found in nearly all organisms throughout their genomes. Repetitive regions are frequently heterochromatinized resulting in silencing of intrinsic and nearby genes. However, this is not a uniform rule, with several genes known to require such an environment to permit transcription. Repetitive regions frequently exist as dinucleotide, trinucleotide, and tetranucleotide repeats. The association between repetitive regions and disease was emphasized following the discovery of abnormal trinucleotide repeats underlying spinal and bulbar muscular atrophy (Kennedy's disease) and fragile X syndrome of mental retardation (FRAXA) in 1991. In this review, we provide a brief overview of epigenetic mechanisms and then focus on several diseases caused by DNA triplet-repeat expansions, which exhibit diverse epigenetic effects. It is clear that the emerging field of epigenetics is already generating novel potential therapeutic avenues for this group of largely incurable diseases.
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Affiliation(s)
- Sathiji Nageshwaran
- Division of Brain Sciences and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, Hammersmith Hospital Campus , London , UK
| | - Richard Festenstein
- Division of Brain Sciences and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, Hammersmith Hospital Campus , London , UK
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24
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Chapuis MP, Plantamp C, Streiff R, Blondin L, Piou C. Microsatellite evolutionary rate and pattern in Schistocerca gregaria inferred from direct observation of germline mutations. Mol Ecol 2015; 24:6107-19. [PMID: 26562076 DOI: 10.1111/mec.13465] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/05/2015] [Accepted: 11/06/2015] [Indexed: 01/21/2023]
Abstract
Unravelling variation among taxonomic orders regarding the rate of evolution in microsatellites is crucial for evolutionary biology and population genetics research. The mean mutation rate of microsatellites tends to be lower in arthropods than in vertebrates, but data are scarce and mostly concern accumulation of mutations in model species. Based on parent-offspring segregations and a hierarchical Bayesian model, the mean rate of mutation in the orthopteran insect Schistocerca gregaria was estimated at 2.1e(-4) per generation per untranscribed dinucleotide locus. This is close to vertebrate estimates and one order of magnitude higher than estimates from species of other arthropod orders, such as Drosophila melanogaster and Daphnia pulex. We also found evidence of a directional bias towards expansions even for long alleles and exceptionally large ranges of allele sizes. Finally, at transcribed microsatellites, the mean rate of mutation was half the rate found at untranscribed loci and the mutational model deviated from that usually considered, with most mutations involving multistep changes that avoid disrupting the reading frame. Our direct estimates of mutation rate were discussed in the light of peculiar biological and genomic features of S. gregaria, including specificities in mismatch repair and the dependence of its activity to allele length. Shedding new light on the mutational dynamics of grasshopper microsatellites is of critical importance for a number of research fields. As an illustration, we showed how our findings improve microsatellite application in population genetics, by obtaining a more precise estimation of S. gregaria effective population size from a published data set based on the same microsatellites.
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Affiliation(s)
- M-P Chapuis
- CIRAD, UMR CBGP, Montpellier, F-34398, France
| | - C Plantamp
- Laboratoire de Biométrie et Biologie Evolutive, CNRS, UMR 5558, Université Lyon 1, Villeurbanne, 69622, France
| | - R Streiff
- INRA, UMR CBGP, Montpellier, F-34398, France.,INRA, UMR DGIMI, Montpellier, F-34000, France
| | - L Blondin
- CIRAD, UPR B-AMR, Montpellier, F-34398, France
| | - C Piou
- CIRAD, UMR CBGP, Montpellier, F-34398, France
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25
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Abstract
DNA repair normally protects the genome against mutations that threaten genome integrity and thus cell viability. However, growing evidence suggests that in the case of the Repeat Expansion Diseases, disorders that result from an increase in the size of a disease-specific microsatellite, the disease-causing mutation is actually the result of aberrant DNA repair. A variety of proteins from different DNA repair pathways have thus far been implicated in this process. This review will summarize recent findings from patients and from mouse models of these diseases that shed light on how these pathways may interact to cause repeat expansion.
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Affiliation(s)
- Xiao-Nan Zhao
- Section on Genomic Structure and Function Laboratory of Cell and Molecular Biology National Institute of Diabetes, Digestive and Kidney Diseases National Institutes of Health, Bethesda, MD 20892-0830, USA
| | - Karen Usdin
- Section on Genomic Structure and Function Laboratory of Cell and Molecular Biology National Institute of Diabetes, Digestive and Kidney Diseases National Institutes of Health, Bethesda, MD 20892-0830, USA.
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26
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Usdin K, House NCM, Freudenreich CH. Repeat instability during DNA repair: Insights from model systems. Crit Rev Biochem Mol Biol 2015; 50:142-67. [PMID: 25608779 DOI: 10.3109/10409238.2014.999192] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The expansion of repeated sequences is the cause of over 30 inherited genetic diseases, including Huntington disease, myotonic dystrophy (types 1 and 2), fragile X syndrome, many spinocerebellar ataxias, and some cases of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Repeat expansions are dynamic, and disease inheritance and progression are influenced by the size and the rate of expansion. Thus, an understanding of the various cellular mechanisms that cooperate to control or promote repeat expansions is of interest to human health. In addition, the study of repeat expansion and contraction mechanisms has provided insight into how repair pathways operate in the context of structure-forming DNA, as well as insights into non-canonical roles for repair proteins. Here we review the mechanisms of repeat instability, with a special emphasis on the knowledge gained from the various model systems that have been developed to study this topic. We cover the repair pathways and proteins that operate to maintain genome stability, or in some cases cause instability, and the cross-talk and interactions between them.
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Affiliation(s)
- Karen Usdin
- Laboratory of Cell and Molecular Biology, NIDDK, NIH , Bethesda, MD , USA
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27
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Santillan BA, Moye C, Mittelman D, Wilson JH. GFP-based fluorescence assay for CAG repeat instability in cultured human cells. PLoS One 2014; 9:e113952. [PMID: 25423602 PMCID: PMC4244167 DOI: 10.1371/journal.pone.0113952] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 11/03/2014] [Indexed: 12/13/2022] Open
Abstract
Trinucleotide repeats can be highly unstable, mutating far more frequently than point mutations. Repeats typically mutate by addition or loss of units of the repeat. CAG repeat expansions in humans trigger neurological diseases that include myotonic dystrophy, Huntington disease, and several spinocerebellar ataxias. In human cells, diverse mechanisms promote CAG repeat instability, and in mice, the mechanisms of instability are varied and tissue-dependent. Dissection of mechanistic complexity and discovery of potential therapeutics necessitates quantitative and scalable screens for repeat mutation. We describe a GFP-based assay for screening modifiers of CAG repeat instability in human cells. The assay exploits an engineered intronic CAG repeat tract that interferes with expression of an inducible GFP minigene. Like the phenotypes of many trinucleotide repeat disorders, we find that GFP function is impaired by repeat expansion, in a length-dependent manner. The intensity of fluorescence varies inversely with repeat length, allowing estimates of repeat tract changes in live cells. We validate the assay using transcription through the repeat and engineered CAG-specific nucleases, which have previously been reported to induce CAG repeat instability. The assay is relatively fast and should be adaptable to large-scale screens of chemical and shRNA libraries.
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Affiliation(s)
- Beatriz A. Santillan
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Christopher Moye
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - David Mittelman
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - John H. Wilson
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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28
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Jenkins TG, Aston KI, Pflueger C, Cairns BR, Carrell DT. Age-associated sperm DNA methylation alterations: possible implications in offspring disease susceptibility. PLoS Genet 2014; 10:e1004458. [PMID: 25010591 PMCID: PMC4091790 DOI: 10.1371/journal.pgen.1004458] [Citation(s) in RCA: 199] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 05/09/2014] [Indexed: 11/18/2022] Open
Abstract
Recent evidence demonstrates a role for paternal aging on offspring disease susceptibility. It is well established that various neuropsychiatric disorders (schizophrenia, autism, etc.), trinucleotide expansion associated diseases (myotonic dystrophy, Huntington's, etc.) and even some forms of cancer have increased incidence in the offspring of older fathers. Despite strong epidemiological evidence that these alterations are more common in offspring sired by older fathers, in most cases the mechanisms that drive these processes are unclear. However, it is commonly believed that epigenetics, and specifically DNA methylation alterations, likely play a role. In this study we have investigated the impact of aging on DNA methylation in mature human sperm. Using a methylation array approach we evaluated changes to sperm DNA methylation patterns in 17 fertile donors by comparing the sperm methylome of 2 samples collected from each individual 9-19 years apart. With this design we have identified 139 regions that are significantly and consistently hypomethylated with age and 8 regions that are significantly hypermethylated with age. A representative subset of these alterations have been confirmed in an independent cohort. A total of 117 genes are associated with these regions of methylation alterations (promoter or gene body). Intriguingly, a portion of the age-related changes in sperm DNA methylation are located at genes previously associated with schizophrenia and bipolar disorder. While our data does not establish a causative relationship, it does raise the possibility that the age-associated methylation of the candidate genes that we observe in sperm might contribute to the increased incidence of neuropsychiatric and other disorders in the offspring of older males. However, further study is required to determine whether, and to what extent, a causative relationship exists.
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Affiliation(s)
- Timothy G. Jenkins
- Andrology and IVF Laboratories, Department of Surgery, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
| | - Kenneth I. Aston
- Andrology and IVF Laboratories, Department of Surgery, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
| | - Christian Pflueger
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
| | - Bradley R. Cairns
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- * E-mail: (BRC); (DTC)
| | - Douglas T. Carrell
- Andrology and IVF Laboratories, Department of Surgery, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
- Department of Genetics, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
- Department of Obstetrics and Gynecology, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
- * E-mail: (BRC); (DTC)
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Ronen M, Avrahami D, Gerber D. A sensitive microfluidic platform for a high throughput DNA methylation assay. LAB ON A CHIP 2014; 14:2354-2362. [PMID: 24841578 DOI: 10.1039/c4lc00150h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
DNA methylation is an epigenetic modification essential for normal development and maintenance of somatic biological functions. DNA methylation provides heritable, long-term chromatin regulation and the aberrant methylation pattern is associated with complex diseases including cancer. Discovering novel therapeutic targets demands development of high-throughput, sensitive and inexpensive screening platforms for libraries of chemical or biological matter involved in DNA methylation establishment and maintenance. Here, we present a universal, high-throughput, microfluidic-based fluorometric assay for studying DNA methylation in vitro. The enzymatic activity of bacterial HPAII DNA methyltransferase and its kinetic properties are measured using the assay (K(m)(DNA) = 5.8 nM, K(m)(SAM) = 9.8 nM and Kcat = 0.04 s(-1)). Using the same platform, we then demonstrate a two-step approach for high-throughput in vitro identification and characterization of small molecule inhibitors of methylation. The approach is examined using known non-nucleoside inhibitors, SGI-1027 and RG108, for which we measured IC50 of 4.5 μM and 87.5 nM, respectively. The dual role of the microfluidic-based methylation assay both for the quantitative characterization of enzymatic activity and high-throughput screening of non-nucleoside inhibitors coupled with quantitative characterization of the inhibition potential highlights the advantages of our system for epigenetic studies.
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Affiliation(s)
- Maria Ronen
- The Mina & Everard Goodman Faculty of Life Sciences, The Nanotechnology Institute, Bar-Ilan University, Ramat Gan, 5290002, Israel.
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30
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Lu H, Liu X, Deng Y, Qing H. DNA methylation, a hand behind neurodegenerative diseases. Front Aging Neurosci 2013; 5:85. [PMID: 24367332 PMCID: PMC3851782 DOI: 10.3389/fnagi.2013.00085] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 11/17/2013] [Indexed: 12/13/2022] Open
Abstract
Epigenetic alterations represent a sort of functional modifications related to the genome that are not responsible for changes in the nucleotide sequence. DNA methylation is one of such epigenetic modifications that have been studied intensively for the past several decades. The transfer of a methyl group to the 5 position of a cytosine is the key feature of DNA methylation. A simple change as such can be caused by a variety of factors, which can be the cause of many serious diseases including several neurodegenerative diseases. In this review, we have reviewed and summarized recent progress regarding DNA methylation in four major neurodegenerative diseases: Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). The studies of these four major neurodegenerative diseases conclude the strong suggestion of the important role DNA methylation plays in these diseases. However, each of these diseases has not yet been understood completely as details in some areas remain unclear, and will be investigated in future studies. We hope this review can provide new insights into the understanding of neurodegenerative diseases from the epigenetic perspective.
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Affiliation(s)
| | | | | | - Hong Qing
- School of Life Science, Beijing Institute of TechnologyBeijing, China
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31
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Evans-Galea MV, Hannan AJ, Carrodus N, Delatycki MB, Saffery R. Epigenetic modifications in trinucleotide repeat diseases. Trends Mol Med 2013; 19:655-63. [DOI: 10.1016/j.molmed.2013.07.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Revised: 07/12/2013] [Accepted: 07/22/2013] [Indexed: 12/18/2022]
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Valor LM, Guiretti D. What's wrong with epigenetics in Huntington's disease? Neuropharmacology 2013; 80:103-14. [PMID: 24184315 DOI: 10.1016/j.neuropharm.2013.10.025] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 10/16/2013] [Accepted: 10/21/2013] [Indexed: 12/15/2022]
Abstract
Huntington's disease (HD) can be considered the paradigm of epigenetic dysregulation in neurodegenerative disorders. In this review, we attempted to compile the evidence that indicates, on the one hand, that several epigenetic marks (histone acetylation, methylation, ubiquitylation, phosphorylation and DNA modifications) are altered in multiple models and in postmortem patient samples, and on the other hand, that pharmacological treatments aimed to reverse such alterations have beneficial effects on HD phenotypic and biochemical traits. However, the working hypotheses regarding the biological significance of epigenetic dysregulation in this disease and the mechanisms of action of the tested ameliorative strategies need to be refined. Understanding the complexity of the epigenetics in HD will provide useful insights to examine the role of epigenetic dysregulation in other neuropathologies, such as Alzheimer's or Parkinson's diseases.
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Affiliation(s)
- Luis M Valor
- Instituto de Neurociencias de Alicante (Universidad Miguel Hernández, Consejo Superior de Investigaciones Científicas), Av. Santiago Ramón y Cajal s/n, Sant Joan d'Alacant, 03550 Alicante, Spain.
| | - Deisy Guiretti
- Instituto de Neurociencias de Alicante (Universidad Miguel Hernández, Consejo Superior de Investigaciones Científicas), Av. Santiago Ramón y Cajal s/n, Sant Joan d'Alacant, 03550 Alicante, Spain
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Induction of a trophoblast-like phenotype by hydralazine in the p19 embryonic carcinoma cell line. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012. [PMID: 23195226 DOI: 10.1016/j.bbamcr.2012.11.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chemicals that affect cellular differentiation through epigenetic mechanisms have potential utility in treating a wide range of diseases. Hydralazine decreases DNA methylation in some cell types but its effect on differentiation has not been well explored. After five days of exposure to hydralazine, P19 embryocarcinoma cells displayed a giant cell morphology and were binucleate, indicative of a trophoblast-like morphology. Other trophoblast-like properties included the intermediary filament Troma-1/cytokeratin 8 and the transcription factor Tead4. A decrease in CpG methylation at three sites in the TEAD4 promoter and the B1 repeated sequence was observed. Knocking down expression of Tead4 with siRNA blocked the increase in Troma-1/cytokeratin 8 and over expression of Tead4 induced the expression of Troma-1/cytokeratin 8. Cells treated for 5days with hydralazine were no longer capable of undergoing retinoic acid-mediated neuronal differentiation. An irreversible loss of the pluripotent transcription factor Oct-4 was observed following hydralazine exposure. In summary, hydralazine induces P19 cells to assume a trophoblast-like phenotype by upregulating Tead4 expression through a mechanism involving DNA demethylation.
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Fonville NC, Ward RM, Mittelman D. Stress-induced modulators of repeat instability and genome evolution. J Mol Microbiol Biotechnol 2012; 21:36-44. [PMID: 22248541 DOI: 10.1159/000332748] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Evolution hinges on the ability of organisms to adapt to their environment. A key regulator of adaptability is mutation rate, which must be balanced to maintain genome fidelity while permitting sufficient plasticity to cope with environmental changes. Multiple mechanisms govern an organism's mutation rate. Constitutive mechanisms include mutator alleles that drive global, permanent increases in mutation rates, but these changes are confined to the subpopulation that carries the mutator allele. Other mechanisms focus mutagenesis in time and space to improve the chances that adaptive mutations can spread through the population. For example, environmental stress can induce mechanisms that transiently relax the fidelity of DNA repair to bring about a temporary increase in mutation rates during times when an organism experiences a reduced fitness for its surroundings, as has been demonstrated for double-strand break repair in Escherichia coli. Still, other mechanisms control the spatial distribution of mutations by directing changes to especially mutable sequences in the genome. In eukaryotic cells, for example, the stress-sensitive chaperone Hsp90 can regulate the length of trinucleotide repeats to fine-tune gene function and can regulate the mobility of transposable elements to enable larger functional changes. Here, we review the regulation of mutation rate, with special emphasis on the roles of tandem repeats and environmental stress in genome evolution.
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Chromatin changes in the development and pathology of the Fragile X-associated disorders and Friedreich ataxia. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1819:802-10. [PMID: 22245581 DOI: 10.1016/j.bbagrm.2011.12.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/22/2011] [Accepted: 12/26/2011] [Indexed: 01/11/2023]
Abstract
The Fragile X-associated disorders (FXDs) and Friedreich ataxia (FRDA) are genetic conditions resulting from expansion of a trinucleotide repeat in a region of the affected gene that is transcribed but not translated. In the case of the FXDs, pathology results from expansion of CGG•CCG-repeat tract in the 5' UTR of the FMR1 gene, while pathology in FRDA results from expansion of a GAA•TTC-repeat in intron 1 of the FXN gene. Expansion occurs during gametogenesis or early embryogenesis by a mechanism that is not well understood. Associated Expansion then produces disease pathology in various ways that are not completely understood either. In the case of the FXDs, alleles with 55-200 repeats express higher than normal levels of a transcript that is thought to be toxic, while alleles with >200 repeats are silenced. In addition, alleles with >200 repeats are associated with a cytogenetic abnormality known as a fragile site, which is apparent as a constriction or gap in the chromatin that is seen when cells are grown in presence of inhibitors of thymidylate synthase. FRDA alleles show a deficit of the FXN transcript. This review will address the role of repeat-mediated chromatin changes in these aspects of FXD and FRDA disease pathology. This article is part of a Special Issue entitled: Chromatin in time and space.
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37
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Topoisomerase 1 and single-strand break repair modulate transcription-induced CAG repeat contraction in human cells. Mol Cell Biol 2011; 31:3105-12. [PMID: 21628532 DOI: 10.1128/mcb.05158-11] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Expanded trinucleotide repeats are responsible for a number of neurodegenerative diseases, such as Huntington disease and myotonic dystrophy type 1. The mechanisms that underlie repeat instability in the germ line and in the somatic tissues of human patients are undefined. Using a selection assay based on contraction of CAG repeat tracts in human cells, we screened the Prestwick chemical library in a moderately high-throughput assay and identified 18 novel inducers of repeat contraction. A subset of these compounds targeted pathways involved in the management of DNA supercoiling associated with transcription. Further analyses using both small molecule inhibitors and small interfering RNA (siRNA)-mediated knockdowns demonstrated the involvement of topoisomerase 1 (TOP1), tyrosyl-DNA phosphodiesterase 1 (TDP1), and single-strand break repair (SSBR) in modulating transcription-dependent CAG repeat contractions. The TOP1-TDP1-SSBR pathway normally functions to suppress repeat instability, since interfering with it stimulated repeat contractions. We further showed that the increase in repeat contractions when the TOP1-TDP1-SSBR pathway is compromised arises via transcription-coupled nucleotide excision repair, a previously identified contributor to transcription-induced repeat instability. These studies broaden the scope of pathways involved in transcription-induced CAG repeat instability and begin to define their interrelationships.
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38
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Abstract
Epigenetic marks are well recognized as heritable chemical modifications of DNA and chromatin that induce chromatin structural changes thereby affecting gene activity. A lesser-known phenomenon is the pervasive effects these marks have on genomic integrity. Remarkably, epigenetic marks and the enzymes that establish them are involved in multiple aspects of maintaining genetic content. These aspects include preserving nucleotide sequences such as repetitive elements, preventing DNA damage, functioning in DNA repair mechanisms and chromatin restoration, and defining chromosomal organization through effects on structural elements such as the centromere. This review discusses these functional aspects of epigenetic marks and their effects on human health and disease.
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López Castel A, Nakamori M, Tomé S, Chitayat D, Gourdon G, Thornton CA, Pearson CE. Expanded CTG repeat demarcates a boundary for abnormal CpG methylation in myotonic dystrophy patient tissues. Hum Mol Genet 2010; 20:1-15. [PMID: 21044947 DOI: 10.1093/hmg/ddq427] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Myotonic dystrophy (DM1) affects multiple organs, shows age-dependent progression and is caused by CTG expansions at the DM1 locus. We determined the DM1 CpG methylation profile and CTG length in tissues from DM1 foetuses, DM1 adults, non-affected individuals and transgenic DM1 mice. Analysis included CTCF binding sites upstream and downstream of the CTG tract, as methylation-sensitive CTCF binding affects chromatinization and transcription of the DM1 locus. In humans, in a given foetus, expansions were largest in heart and smallest in liver, differing by 40-400 repeats; in adults, the largest expansions were in heart and cerebral cortex and smallest in cerebellum, differing by up to 5770 repeats in the same individual. Abnormal methylation was specific to the mutant allele. In DM1 adults, heart, liver and cortex showed high-to-moderate methylation levels, whereas cerebellum, kidney and skeletal muscle were devoid of methylation. Methylation decreased between foetuses and adults. Contrary to previous findings, methylation was not restricted to individuals with congenital DM1. The expanded repeat demarcates an abrupt boundary of methylation. Upstream sequences, including the CTCF site, were methylated, whereas the repeat itself and downstream sequences were not. In DM1 mice, expansion-, tissue- and age-specific methylation patterns were similar but not identical to those in DM1 individuals; notably in mice, methylation was present up- and downstream of the repeat, but greater upstream. Thus, in humans, the CpG-free expanded CTG repeat appears to maintain a highly polarized pattern of CpG methylation at the DM1 locus, which varies markedly with age and tissues.
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Affiliation(s)
- Arturo López Castel
- Genetics and Genome Biology, Department of Pediatrics, The Hospital for Sick Children, and Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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40
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Mittelman D, Sykoudis K, Hersh M, Lin Y, Wilson JH. Hsp90 modulates CAG repeat instability in human cells. Cell Stress Chaperones 2010; 15:753-9. [PMID: 20373063 PMCID: PMC3006633 DOI: 10.1007/s12192-010-0191-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 03/16/2010] [Accepted: 03/18/2010] [Indexed: 12/30/2022] Open
Abstract
The Hsp90 molecular chaperone has been implicated as a contributor to evolution in several organisms by revealing cryptic variation that can yield dramatic phenotypes when the chaperone is diverted from its normal functions by environmental stress. In addition, as a cancer drug target, Hsp90 inhibition has been documented to sensitize cells to DNA-damaging agents, suggesting a function for Hsp90 in DNA repair. Here we explore the potential role of Hsp90 in modulating the stability of nucleotide repeats, which in a number of species, including humans, exert subtle and quantitative consequences for protein function, morphological and behavioral traits, and disease. We report that impairment of Hsp90 in human cells induces contractions of CAG repeat tracks by tenfold. Inhibition of the recombinase Rad51, a downstream target of Hsp90, induces a comparable increase in repeat instability, suggesting that Hsp90-enabled homologous recombination normally functions to stabilize CAG repeat tracts. By contrast, Hsp90 inhibition does not increase the rate of gene-inactivating point mutations. The capacity of Hsp90 to modulate repeat-tract lengths suggests that the chaperone, in addition to exposing cryptic variation, might facilitate the expression of new phenotypes through induction of novel genetic variation.
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Affiliation(s)
- David Mittelman
- Human Genome Sequencing Center, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 USA
| | - Kristen Sykoudis
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 USA
| | - Megan Hersh
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 USA
| | - Yunfu Lin
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 USA
| | - John H. Wilson
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 USA
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 USA
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41
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McIvor EI, Polak U, Napierala M. New insights into repeat instability: role of RNA•DNA hybrids. RNA Biol 2010; 7:551-8. [PMID: 20729633 DOI: 10.4161/rna.7.5.12745] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Expansion of tandem repeat sequences is responsible for more than 20 human diseases. Several cis elements and trans factors involved in repeat instability (expansion and contraction) have been identified. However no comprehensive model explaining large intergenerational or somatic changes of the length of the repeating sequences exists. Several lines of evidence, accumulated from different model studies, indicate that transcription through repeat sequences is an important factor promoting their instability. The persistent interaction between transcription template DNA and nascent RNA (RNA•DNA hybrids, R loops) was shown to stimulate genomic instability. Recently, we demonstrated that cotranscriptional RNA•DNA hybrids are preferentially formed at GC-rich trinucleotide and tetranucleotide repeat sequences in vitro as well as in human genomic DNA. Additionally, we showed that cotranscriptional formation of RNA•DNA hybrids at CTG•CAG and GAA•TTC repeats stimulate instability of these sequences in both E. coli and human cells. Our results suggest that persistent RNA•DNA hybrids may also be responsible for other downstream effects of expanded trinucleotide repeats, including gene silencing. Considering the extent of transcription through the human genome as well as the abundance of GC-rich and/or non-canonical DNA structure forming tandem repeats, RNA•DNA hybrids may represent a common mutagenic conformation. Hence, R loops are potentially attractive therapeutic target in diseases associated with genomic instability.
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Affiliation(s)
- Elizabeth I McIvor
- Department of Biochemistry and Molecular Biology and Center for Cancer Epigenetics, University of Texas MD Anderson Cancer Center, Houston, TX, USA
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42
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Convergent transcription through a long CAG tract destabilizes repeats and induces apoptosis. Mol Cell Biol 2010; 30:4435-51. [PMID: 20647539 DOI: 10.1128/mcb.00332-10] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Short repetitive sequences are common in the human genome, and many fall within transcription units. We have previously shown that transcription through CAG repeat tracts destabilizes them in a way that depends on transcription-coupled nucleotide excision repair and mismatch repair. Recent observations that antisense transcription accompanies sense transcription in many human genes led us to test the effects of antisense transcription on triplet repeat instability in human cells. Here, we report that simultaneous sense and antisense transcription (convergent transcription) initiated from two inducible promoters flanking a CAG95 tract in a nonessential gene enhances repeat instability synergistically, arrests the cell cycle, and causes massive cell death via apoptosis. Using chemical inhibitors and small interfering RNA (siRNA) knockdowns, we identified the ATR (ataxia-telangiectasia mutated [ATM] and Rad3 related) signaling pathway as a key mediator of this cellular response. RNA polymerase II, replication protein A (RPA), and components of the ATR signaling pathway accumulate at convergently transcribed repeat tracts, accompanied by phosphorylation of ATR, CHK1, and p53. Cell death depends on simultaneous sense and antisense transcription and is proportional to their relative levels, it requires the presence of the repeat tract, and it occurs in both proliferating and nonproliferating cells. Convergent transcription through a CAG repeat represents a novel mechanism for triggering a cellular stress response, one that is initiated by events at a single locus in the genome and resembles the response to DNA damage.
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43
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Induction of Foxp3 demethylation increases regulatory CD4+CD25+ T cells and prevents the occurrence of diabetes in mice. J Mol Med (Berl) 2009; 87:1191-205. [DOI: 10.1007/s00109-009-0530-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 08/02/2009] [Accepted: 08/26/2009] [Indexed: 01/09/2023]
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44
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Instability and chromatin structure of expanded trinucleotide repeats. Trends Genet 2009; 25:288-97. [PMID: 19540013 DOI: 10.1016/j.tig.2009.04.007] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 04/29/2009] [Accepted: 04/30/2009] [Indexed: 12/16/2022]
Abstract
Trinucleotide repeat expansion underlies at least 17 neurological diseases. In affected individuals, the expanded locus is characterized by dramatic changes in chromatin structure and in repeat tract length. Interestingly, recent studies show that several chromatin modifiers, including a histone acetyltransferase, a DNA methyltransferase and the chromatin insulator CTCF can modulate repeat instability. Here, we propose that the unusual chromatin structure of expanded repeats directly impacts their instability. We discuss several potential models for how this might occur, including a role for DNA repair-dependent epigenetic reprogramming in increasing repeat instability, and the capacity of epigenetic marks to alter sense and antisense transcription, thereby affecting repeat instability.
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45
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Mittelman D, Moye C, Morton J, Sykoudis K, Lin Y, Carroll D, Wilson JH. Zinc-finger directed double-strand breaks within CAG repeat tracts promote repeat instability in human cells. Proc Natl Acad Sci U S A 2009; 106:9607-12. [PMID: 19482946 PMCID: PMC2701052 DOI: 10.1073/pnas.0902420106] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Indexed: 01/12/2023] Open
Abstract
Expanded triplet repeats have been identified as the genetic basis for a growing number of neurological and skeletal disorders. To examine the contribution of double-strand break repair to CAG x CTG repeat instability in mammalian systems, we developed zinc finger nucleases (ZFNs) that recognize and cleave CAG repeat sequences. Engineered ZFNs use a tandem array of zinc fingers, fused to the FokI DNA cleavage domain, to direct double-strand breaks (DSBs) in a site-specific manner. We first determined that the ZFNs cleave CAG repeats in vitro. Then, using our previously described tissue culture assay for identifying modifiers of CAG repeat instability, we found that transfection of ZFN-expression vectors induced up to a 15-fold increase in changes to the CAG repeat in human and rodent cell lines, and that longer repeats were much more sensitive to cleavage than shorter ones. Analysis of individual colonies arising after treatment revealed a spectrum of events consistent with ZFN-induced DSBs and dominated by repeat contractions. We also found that expressing a dominant-negative form of RAD51 in combination with a ZFN, dramatically reduced the effect of the nuclease, suggesting that DSB-induced repeat instability is mediated, in part, through homology directed repair. These studies identify a ZFN as a useful reagent for characterizing the effects of DSBs on CAG repeats in cells.
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Affiliation(s)
- David Mittelman
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030; and
| | - Christopher Moye
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Jason Morton
- Department of Biochemistry, University of Utah School of Medicine,Salt Lake City, UT 84112
| | - Kristen Sykoudis
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Yunfu Lin
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Dana Carroll
- Department of Biochemistry, University of Utah School of Medicine,Salt Lake City, UT 84112
| | - John H. Wilson
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030; and
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46
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Abstract
Triplet repeat expansion is the molecular basis for several human diseases. Intensive studies using systems in bacteria, yeast, flies, mammalian cells, and mice have provided important insights into the molecular processes that are responsible for mediating repeat instability. The age-dependent, ongoing repeat instability in somatic tissues, especially in terminally differentiated neurons, strongly suggests a robust role for pathways that are independent of DNA replication. Several genetic studies have indicated that transcription can play a critical role in repeat instability, potentially providing a basis for the instability observed in neurons. Transcription-induced repeat instability can be modulated by several DNA repair proteins, including those involved in mismatch repair (MMR) and transcription-coupled nucleotide excision repair (TC-NER). Though the mechanism is unclear, it is likely that transcription facilitates the formation of repeat-specific secondary structures, which act as intermediates to trigger DNA repair, eventually leading to changes in the length of the repeat tract. In addition, other processes associated with transcription can also modulate repeat instability, as shown in a variety of different systems. Overall, the mechanisms underlying repeat instability in humans are unexpectedly complicated. Because repeat-disease genes are widely expressed, transcription undoubtedly contributes to the repeat instability observed in many diseases, but it may be especially important in nondividing cells. Transcription-induced instability is likely to involve an extensive interplay not only of the core transcription machinery and DNA repair proteins, but also of proteins involved in chromatin remodeling, regulation of supercoiling, and removal of stalled RNA polymerases, as well as local DNA sequence effects.
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Affiliation(s)
- Yunfu Lin
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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47
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Dion V, Lin Y, Price BA, Fyffe SL, Seluanov A, Gorbunova V, Wilson JH. Genome-wide demethylation promotes triplet repeat instability independently of homologous recombination. DNA Repair (Amst) 2008; 7:313-20. [PMID: 18083071 DOI: 10.1016/j.dnarep.2007.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 10/30/2007] [Accepted: 11/05/2007] [Indexed: 01/06/2023]
Abstract
Trinucleotide repeat instability is intrinsic to a family of human neurodegenerative diseases. The mechanism leading to repeat length variation is unclear. We previously showed that treatment with the demethylating agent 5-aza-2'-deoxycytidine (5-aza-CdR) dramatically increases triplet repeat instability in mammalian cells. Based on previous reports that demethylation increases homologous recombination (HR), and our own observations that HR destabilizes triplet repeats, we hypothesized that demethylation alters repeat stability by stimulating HR. Here, we test that hypothesis at the adenosine phosphoribosyl transferase (Aprt) locus in CHO cells, where CpG demethylation and HR have both been shown to increase CAG repeat instability. We find that the rate of HR at the Aprt locus is not altered by demethylation. The spectrum of recombinants, however, was shifted from the usual 6:1 ratio of conversions to crossovers to more equal proportions in 5-aza-CdR-treated cells. The subtle influences of demethylation on HR at the Aprt locus are not sufficient to account for its dramatic effects on repeat instability. We conclude that 5-aza-CdR promotes triplet repeat instability independently of HR.
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Affiliation(s)
- Vincent Dion
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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48
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Abstract
Unstable repeats are associated with various types of cancer and have been implicated in more than 40 neurodegenerative disorders. Trinucleotide repeats are located in non-coding and coding regions of the genome. Studies of bacteria, yeast, mice and man have helped to unravel some features of the mechanism of trinucleotide expansion. Looped DNA structures comprising trinucleotide repeats are processed during replication and/or repair to generate deletions or expansions. Most in vivo data are consistent with a model in which expansion and deletion occur by different mechanisms. In mammals, microsatellite instability is complex and appears to be influenced by genetic, epigenetic and developmental factors.
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49
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Dion V, Lin Y, Hubert L, Waterland RA, Wilson JH. Dnmt1 deficiency promotes CAG repeat expansion in the mouse germline. Hum Mol Genet 2008; 17:1306-17. [PMID: 18252747 DOI: 10.1093/hmg/ddn019] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Expanded CAG repeat tracts are the cause of at least a dozen neurodegenerative disorders. In humans, long CAG repeats tend to expand during transmissions from parent to offspring, leading to an earlier age of disease onset and more severe symptoms in subsequent generations. Here, we show that the maintenance DNA methyltransferase Dnmt1, which preserves the patterns of CpG methylation, plays a key role in CAG repeat instability in human cells and in the male and female mouse germlines. SiRNA knockdown of Dnmt1 in human cells destabilized CAG triplet repeats, and Dnmt1 deficiency in mice promoted intergenerational expansion of CAG repeats at the murine spinocerebellar ataxia type 1 (Sca1) locus. Importantly, Dnmt1(+/-) SCA1 mice, unlike their Dnmt1(+/+) SCA1 counterparts, closely reproduced the intergenerational instability patterns observed in human SCA1 patients. In addition, we found aberrant DNA and histone methylation at sites within the CpG island that abuts the expanded repeat tract in Dnmt1-deficient mice. These studies suggest that local chromatin structure may play a role in triplet repeat instability. These results are consistent with normal epigenetic changes during germline development contributing to intergenerational instability of CAG repeats in mice and in humans.
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Affiliation(s)
- Vincent Dion
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, USDA Children's Nutrition Research Center, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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Laidlaw J, Gelfand Y, Ng KW, Garner HR, Ranganathan R, Benson G, Fondon JW. Elevated basal slippage mutation rates among the Canidae. ACTA ACUST UNITED AC 2007; 98:452-60. [PMID: 17437958 DOI: 10.1093/jhered/esm017] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The remarkable responsiveness of dog morphology to selection is a testament to the mutability of mammals. The genetic sources of this morphological variation are largely unknown, but some portion is due to tandem repeat length variation in genes involved in development. Previous analysis of tandem repeats in coding regions of developmental genes revealed fewer interruptions in repeat sequences in dogs than in the orthologous repeats in humans, as well as higher levels of polymorphism, but the fragmentary nature of the available dog genome sequence thwarted attempts to distinguish between locus-specific and genome-wide origins of this disparity. Using whole-genome analyses of the human and recently completed dog genomes, we show that dogs possess a genome-wide increase in the basal germ-line slippage mutation rate. Building on the approach that gave rise to the initial observation in dogs, we sequenced 55 coding repeat regions in 42 species representing 10 major carnivore clades and found that a genome-wide elevated slippage mutation rate is a derived character shared by diverse wild canids, distinguishing them from other Carnivora. A similarly heightened slippage profile was also detected in rodents, another taxon exhibiting high diversity and rapid evolvability. The correlation of enhanced slippage rates with major evolutionary radiations suggests that the possession of a "slippery" genome may bestow on some taxa greater potential for rapid evolutionary change.
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Affiliation(s)
- Jeffrey Laidlaw
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390, USA
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