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Ginjupalli VKM, Cupelli M, Reisqs JB, Sleiman Y, El-Sherif N, Gourdon G, Puymirat J, Chahine M, Boutjdir M. Electrophysiological basis of cardiac arrhythmia in a mouse model of myotonic dystrophy type 1. Front Physiol 2023; 14:1257682. [PMID: 37811496 PMCID: PMC10551179 DOI: 10.3389/fphys.2023.1257682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 09/06/2023] [Indexed: 10/10/2023] Open
Abstract
Introduction: Myotonic dystrophy type 1 (DM1) is a multisystemic genetic disorder caused by the increased number of CTG repeats in 3' UTR of Dystrophia Myotonia Protein Kinase (DMPK) gene. DM1 patients experience conduction abnormalities as well as atrial and ventricular arrhythmias with increased susceptibility to sudden cardiac death. The ionic basis of these electrical abnormalities is poorly understood. Methods: We evaluated the surface electrocardiogram (ECG) and key ion currents underlying the action potential (AP) in a mouse model of DM1, DMSXL, which express over 1000 CTG repeats. Sodium current (INa), L-type calcium current (ICaL), transient outward potassium current (Ito), and APs were recorded using the patch-clamp technique. Results: Arrhythmic events on the ECG including sinus bradycardia, conduction defects, and premature ventricular and atrial arrhythmias were observed in DMSXL homozygous mice but not in WT mice. PR interval shortening was observed in homozygous mice while ECG parameters such as QRS duration, and QTc did not change. Further, flecainide prolonged PR, QRS, and QTc visually in DMSXL homozygous mice. At the single ventricular myocyte level, we observed a reduced current density for Ito and ICaL with a positive shift in steady state activation of L-type calcium channels carrying ICaL in DMSXL homozygous mice compared with WT mice. INa densities and action potential duration did not change between DMSXL and WT mice. Conclusion: The reduced current densities of Ito, and ICaL and alterations in gating properties in L-type calcium channels may contribute to the ECG abnormalities in the DMSXL mouse model of DM1. These findings open new avenues for novel targeted therapeutics.
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Affiliation(s)
- Vamsi Krishna Murthy Ginjupalli
- Cardiovascular Research Program, VA New York Harbor Health care System, Brooklyn, NY, United States
- Departments of Medicine, Cell Biology and Pharmacology, SUNY Downstate Health Sciences University, Brooklyn, NY, United States
- Department of Medicine, Faculty of Medicine, Université Laval, Quebec City, QC, Canada
| | - Michael Cupelli
- Cardiovascular Research Program, VA New York Harbor Health care System, Brooklyn, NY, United States
- Departments of Medicine, Cell Biology and Pharmacology, SUNY Downstate Health Sciences University, Brooklyn, NY, United States
| | - Jean-Baptiste Reisqs
- Cardiovascular Research Program, VA New York Harbor Health care System, Brooklyn, NY, United States
| | - Yvonne Sleiman
- Cardiovascular Research Program, VA New York Harbor Health care System, Brooklyn, NY, United States
| | - Nabil El-Sherif
- Cardiovascular Research Program, VA New York Harbor Health care System, Brooklyn, NY, United States
- Departments of Medicine, Cell Biology and Pharmacology, SUNY Downstate Health Sciences University, Brooklyn, NY, United States
| | - Genevieve Gourdon
- Centre de recherche en Myologie, Inserm, Institut de Myologie, Sorbonne Université, Paris, France
| | - Jack Puymirat
- LOEX, CHU de Québec-Université Laval Research Center, Quebec City, QC, Canada
| | - Mohamed Chahine
- Department of Medicine, Faculty of Medicine, Université Laval, Quebec City, QC, Canada
- CERVO Research Center, Institut Universitaire en Santé Mentale de Québec, Quebec City, QC, Canada
| | - Mohamed Boutjdir
- Cardiovascular Research Program, VA New York Harbor Health care System, Brooklyn, NY, United States
- Departments of Medicine, Cell Biology and Pharmacology, SUNY Downstate Health Sciences University, Brooklyn, NY, United States
- Department of Medicine, New York University, Grossman School of Medicine, New York, NY, United States
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2
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Nitschke L, Hu RC, Miller A, Lucas L, Cooper T. Alternative splicing mediates the compensatory upregulation of MBNL2 upon MBNL1 loss-of-function. Nucleic Acids Res 2023; 51:1245-1259. [PMID: 36617982 PMCID: PMC9943662 DOI: 10.1093/nar/gkac1219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 12/05/2022] [Accepted: 01/03/2023] [Indexed: 01/10/2023] Open
Abstract
Loss of gene function can be compensated by paralogs with redundant functions. An example of such compensation are the paralogs of the Muscleblind-Like (MBNL) family of RNA-binding proteins that are sequestered and lose their function in Myotonic Dystrophy Type 1 (DM1). Loss of MBNL1 increases the levels of its paralog MBNL2 in tissues where Mbnl2 expression is low, allowing MBNL2 to functionally compensate for MBNL1 loss. Here, we show that loss of MBNL1 increases the inclusion of Mbnl2 exon 6 and exon 9. We find that inclusion of Mbnl2 exon 6 increases the translocation of MBNL2 to the nucleus, while the inclusion of Mbnl2 exon 9 shifts the reading frame to an alternative C-terminus. We show that the C-terminus lacking exon 9 contains a PEST domain which causes proteasomal degradation. Loss of MBNL1 increases the inclusion of exon 9, resulting in an alternative C-terminus lacking the PEST domain and the increase of MBNL2. We further find that the compensatory mechanism is active in a mouse DM1 model. Together, this study uncovers the compensatory mechanism by which loss of MBNL1 upregulates its paralog MBNL2 and highlights a potential role of the compensatory mechanism in DM1.
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Affiliation(s)
- Larissa Nitschke
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Rong-Chi Hu
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Andrew N Miller
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lathan Lucas
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
- Chemical, Physical & Structural Biology Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA
| | - Thomas A Cooper
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular & Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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3
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Lee KY, Seah C, Li C, Chen YF, Chen CY, Wu CI, Liao PC, Shyu YC, Olafson HR, McKee KK, Wang ET, Yeh CH, Wang CH. Mice lacking MBNL1 and MBNL2 exhibit sudden cardiac death and molecular signatures recapitulating myotonic dystrophy. Hum Mol Genet 2022; 31:3144-3160. [PMID: 35567413 PMCID: PMC9476621 DOI: 10.1093/hmg/ddac108] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Revised: 04/22/2022] [Accepted: 05/04/2022] [Indexed: 11/13/2022] Open
Abstract
Myotonic dystrophy (DM) is caused by expansions of C(C)TG repeats in the non-coding regions of the DMPK and CNBP genes, and DM patients often suffer from sudden cardiac death due to lethal conduction block or arrhythmia. Specific molecular changes that underlie DM cardiac pathology have been linked to repeat-associated depletion of Muscleblind-like (MBNL) 1 and 2 proteins and upregulation of CUGBP, Elav-like family member 1 (CELF1). Hypothesis solely targeting MBNL1 or CELF1 pathways that could address all the consequences of repeat expansion in heart remained inconclusive, particularly when the direct cause of mortality and results of transcriptome analyses remained undetermined in Mbnl compound knockout (KO) mice with cardiac phenotypes. Here, we develop Myh6-Cre double KO (DKO) (Mbnl1−/−; Mbnl2cond/cond; Myh6-Cre+/−) mice to eliminate Mbnl1/2 in cardiomyocytes and observe spontaneous lethal cardiac events under no anesthesia. RNA sequencing recapitulates DM heart spliceopathy and shows gene expression changes that were previously undescribed in DM heart studies. Notably, immunoblotting reveals a nearly 6-fold increase of Calsequestrin 1 and 50% reduction of epidermal growth factor proteins. Our findings demonstrate that complete ablation of MBNL1/2 in cardiomyocytes is essential for generating sudden death due to lethal cardiac rhythms and reveal potential mechanisms for DM heart pathogenesis.
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Affiliation(s)
- Kuang-Yung Lee
- Department of Neurology, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan.,Chang Gung University, College of Medicine, Taoyuan, Taiwan
| | - Carol Seah
- Department of Neurology, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan
| | - Ching Li
- Department of Neurology, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan
| | - Yu-Fu Chen
- Department of Neurology, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan
| | - Chwen-Yu Chen
- Department of Neurology, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan
| | - Ching-I Wu
- Department of Neurology, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan
| | - Po-Cheng Liao
- Community Medicine Research Center, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan
| | - Yu-Chiau Shyu
- Community Medicine Research Center, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan.,Department of Nursing, Chang Gung University of Science and Technology, Taoyuan City, Taiwan
| | - Hailey R Olafson
- Department of Molecular Genetics & Microbiology, Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL. 32610, USA
| | - Kendra K McKee
- Department of Molecular Genetics & Microbiology, Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL. 32610, USA
| | - Eric T Wang
- Department of Molecular Genetics & Microbiology, Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL. 32610, USA
| | - Chi-Hsiao Yeh
- Department of Thoracic and Cardiovascular Surgery, Chang Gung Memorial Hospital, Linko Branch, Taoyuan, Taiwan.,Chang Gung University, College of Medicine, Taoyuan, Taiwan
| | - Chao-Hung Wang
- Division of Cardiology, Department of Internal Medicine, Heart Failure Research Center, Chang Gung Memorial Hospital, Keelung Branch, Keelung, Taiwan.,Chang Gung University, College of Medicine, Taoyuan, Taiwan
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4
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Molecular Therapies for Myotonic Dystrophy Type 1: From Small Drugs to Gene Editing. Int J Mol Sci 2022; 23:ijms23094622. [PMID: 35563013 PMCID: PMC9101876 DOI: 10.3390/ijms23094622] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/19/2022] [Accepted: 04/20/2022] [Indexed: 12/16/2022] Open
Abstract
Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy affecting many different body tissues, predominantly skeletal and cardiac muscles and the central nervous system. The expansion of CTG repeats in the DM1 protein-kinase (DMPK) gene is the genetic cause of the disease. The pathogenetic mechanisms are mainly mediated by the production of a toxic expanded CUG transcript from the DMPK gene. With the availability of new knowledge, disease models, and technical tools, much progress has been made in the discovery of altered pathways and in the potential of therapeutic intervention, making the path to the clinic a closer reality. In this review, we describe and discuss the molecular therapeutic strategies for DM1, which are designed to directly target the CTG genomic tract, the expanded CUG transcript or downstream signaling molecules.
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5
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Cardiac Pathology in Myotonic Dystrophy Type 1. Int J Mol Sci 2021; 22:ijms222111874. [PMID: 34769305 PMCID: PMC8584352 DOI: 10.3390/ijms222111874] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/28/2021] [Accepted: 10/29/2021] [Indexed: 01/08/2023] Open
Abstract
Myotonic dystrophy type 1 (DM1), the most common muscular dystrophy affecting adults and children, is a multi-systemic disorder affecting skeletal, cardiac, and smooth muscles as well as neurologic, endocrine and other systems. This review is on the cardiac pathology associated with DM1. The heart is one of the primary organs affected in DM1. Cardiac conduction defects are seen in up to 75% of adult DM1 cases and sudden death due to cardiac arrhythmias is one of the most common causes of death in DM1. Unfortunately, the pathogenesis of cardiac manifestations in DM1 is ill defined. In this review, we provide an overview of the history of cardiac studies in DM1, clinical manifestations, and pathology of the heart in DM1. This is followed by a discussion of emerging data about the utility of cardiac magnetic resonance imaging (CMR) as a biomarker for cardiac disease in DM1, and ends with a discussion on models of cardiac RNA toxicity in DM1 and recent clinical guidelines for cardiologic management of individuals with DM1.
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6
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Rao AN, Campbell HM, Guan X, Word TA, Wehrens XH, Xia Z, Cooper TA. Reversible cardiac disease features in an inducible CUG repeat RNA-expressing mouse model of myotonic dystrophy. JCI Insight 2021; 6:143465. [PMID: 33497365 PMCID: PMC8021116 DOI: 10.1172/jci.insight.143465] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 01/20/2021] [Indexed: 11/17/2022] Open
Abstract
Myotonic dystrophy type 1 (DM1) is caused by a CTG repeat expansion in the DMPK gene. Expression of pathogenic expanded CUG repeat (CUGexp) RNA causes multisystemic disease by perturbing the functions of RNA-binding proteins, resulting in expression of fetal protein isoforms in adult tissues. Cardiac involvement affects 50% of individuals with DM1 and causes 25% of disease-related deaths. We developed a transgenic mouse model for tetracycline-inducible and heart-specific expression of human DMPK mRNA containing 960 CUG repeats. CUGexp RNA is expressed in atria and ventricles and induced mice exhibit electrophysiological and molecular features of DM1 disease, including cardiac conduction delays, supraventricular arrhythmias, nuclear RNA foci with Muscleblind protein colocalization, and alternative splicing defects. Importantly, these phenotypes were rescued upon loss of CUGexp RNA expression. Transcriptome analysis revealed gene expression and alternative splicing changes in ion transport genes that are associated with inherited cardiac conduction diseases, including a subset of genes involved in calcium handling. Consistent with RNA-Seq results, calcium-handling defects were identified in atrial cardiomyocytes isolated from mice expressing CUGexp RNA. These results identify potential tissue-specific mechanisms contributing to cardiac pathogenesis in DM1 and demonstrate the utility of reversible phenotypes in our model to facilitate development of targeted therapeutic approaches.
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Affiliation(s)
| | - Hannah M Campbell
- Department of Molecular Physiology and Biophysics, and.,Medical Scientist Training Program, Baylor College of Medicine, Houston, Texas, USA
| | - Xiangnan Guan
- Computational Biology Program, Oregon Health & Science University, Portland, Oregon, USA
| | - Tarah A Word
- Department of Molecular Physiology and Biophysics, and
| | - Xander Ht Wehrens
- Department of Molecular Physiology and Biophysics, and.,Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas, USA
| | - Zheng Xia
- Computational Biology Program, Oregon Health & Science University, Portland, Oregon, USA.,Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon, USA
| | - Thomas A Cooper
- Department of Molecular and Cellular Biology.,Department of Molecular Physiology and Biophysics, and.,Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas, USA.,Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas, USA
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7
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iPSC-derived cardiomyocytes from patients with myotonic dystrophy type 1 have abnormal ion channel functions and slower conduction velocities. Sci Rep 2021; 11:2500. [PMID: 33510259 PMCID: PMC7844414 DOI: 10.1038/s41598-021-82007-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 10/21/2020] [Indexed: 02/07/2023] Open
Abstract
Cardiac complications such as electrical abnormalities including conduction delays and arrhythmias are the main cause of death in individuals with Myotonic Dystrophy type 1 (DM1). We developed a disease model using iPSC-derived cardiomyocytes (iPSC-CMs) from a healthy individual and two DM1 patients with different CTG repeats lengths and clinical history (DM1-1300 and DM1-300). We confirmed the presence of toxic RNA foci and mis-spliced MBNL1/2 transcripts in DM1 iPSC-CMs. In DM1-1300, we identified a switch in the cardiac sodium channel SCN5A from the adult to the neonatal isoform. The down-regulation of adult SCN5A isoforms is consistent with a shift in the sodium current activation to depolarized potentials observed in DM1-1300. L-type calcium current density was higher in iPSC-CMs from DM1-1300, which is correlated with the overexpression of the CaV1.2 transcript and proteins. Importantly, INa and ICaL dysfunctions resulted in prolonged action potentials duration, slower velocities, and decreased overshoots. Optical mapping analysis revealed a slower conduction velocity in DM1-1300 iPSC-CM monolayers. In conclusion, our data revealed two distinct ions channels perturbations in DM1 iPSC-CM from the patient with cardiac dysfunction, one affecting Na+ channels and one affecting Ca2+ channels. Both have an impact on cardiac APs and ultimately on heart conduction.
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