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Pellman J, Sheikh F. Atrial fibrillation: mechanisms, therapeutics, and future directions. Compr Physiol 2016; 5:649-65. [PMID: 25880508 DOI: 10.1002/cphy.c140047] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, affecting 1% to 2% of the general population. It is characterized by rapid and disorganized atrial activation leading to impaired atrial function, which can be diagnosed on an EKG by lack of a P-wave and irregular QRS complexes. AF is associated with increased morbidity and mortality and is a risk factor for embolic stroke and worsening heart failure. Current research on AF support and explore the hypothesis that initiation and maintenance of AF require pathophysiological remodeling of the atria, either specifically as in lone AF or secondary to other heart disease as in heart failure-associated AF. Remodeling in AF can be grouped into three categories that include: (i) electrical remodeling, which includes modulation of L-type Ca(2+) current, various K(+) currents and gap junction function; (ii) structural remodeling, which includes changes in tissues properties, size, and ultrastructure; and (iii) autonomic remodeling, including altered sympathovagal activity and hyperinnervation. Electrical, structural, and autonomic remodeling all contribute to creating an AF-prone substrate which is able to produce AF-associated electrical phenomena including a rapidly firing focus, complex multiple reentrant circuit or rotors. Although various remodeling events occur in AF, current AF therapies focus on ventricular rate and rhythm control strategies using pharmacotherapy and surgical interventions. Recent progress in the field has started to focus on the underlying substrate that drives and maintains AF (termed upstream therapies); however, much work is needed in this area. Here, we review current knowledge of AF mechanisms, therapies, and new areas of investigation.
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Affiliation(s)
- Jason Pellman
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
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52
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Jassim A, Aoyama H, Ye WG, Chen H, Bai D. Engineered Cx40 variants increased docking and function of heterotypic Cx40/Cx43 gap junction channels. J Mol Cell Cardiol 2016; 90:11-20. [PMID: 26625713 DOI: 10.1016/j.yjmcc.2015.11.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 10/30/2015] [Accepted: 11/24/2015] [Indexed: 02/06/2023]
Abstract
Gap junction (GJ) channels provide low resistance passages for rapid action potential propagation in the heart. Both connexin40 (Cx40) and Cx43 are abundantly expressed in and frequently co-localized between atrial myocytes, possibly forming heterotypic GJ channels. However, conflicting results have been obtained on the functional status of heterotypic Cx40/Cx43 GJs. Here we provide experimental evidence that the docking and formation of heterotypic Cx40/Cx43 GJs can be substantially increased by designed Cx40 variants on the extracellular domains (E1 and E2). Specifically, Cx40 D55N and P193Q, substantially increased the probability to form GJ plaque-like structures at the cell-cell interfaces with Cx43 in model cells. More importantly the coupling conductance (Gj) of D55N/Cx43 and P193Q/Cx43 GJ channels are significantly increased from the Gj of Cx40/Cx43 in N2A cells. Our homology models indicate the electrostatic interactions and surface structures at the docking interface are key factors preventing Cx40 from docking to Cx43. Improving heterotypic Gj of these atrial connexins might be potentially useful in improving the coupling and synchronization of atrial myocardium.
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Affiliation(s)
- Arjewan Jassim
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Hiroshi Aoyama
- Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan
| | - Willy G Ye
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Honghong Chen
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
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53
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Maleszewski J, Lai C, Veinot J. Anatomic Considerations and Examination of Cardiovascular Specimens (Excluding Devices). Cardiovasc Pathol 2016. [DOI: 10.1016/b978-0-12-420219-1.00001-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Wang ZC, Ji WH, Ruan CW, Liu XY, Qiu XB, Yuan F, Li RG, Xu YJ, Liu X, Huang RT, Xue S, Yang YQ. Prevalence and Spectrum of TBX5 Mutation in Patients with Lone Atrial Fibrillation. Int J Med Sci 2016; 13:60-7. [PMID: 26917986 PMCID: PMC4747871 DOI: 10.7150/ijms.13264] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 11/09/2015] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF), the most common type of cardiac rhythm disturbance encountered in clinical practice, is associated with substantially increased morbidity and mortality. Aggregating evidence demonstrates that abnormal cardiovascular development is involved in the pathogenesis of AF. A recent study has revealed that the TBX5 gene, which encodes a T-box transcription factor key to cardiovascular development, was associated with AF and atypical Holt-Oram syndrome. However, the prevalence and spectrum of TBX5 mutation in patients with lone AF remain unclear. In this study, the coding regions and splicing junction sites of TBX5 were sequenced in 192 unrelated patients with lone AF and 300 unrelated ethnically-matched healthy individuals used as controls. The causative potential of the identified TBX5 variation was evaluated by MutationTaster and PolyPhen-2. The functional effect of the mutant TBX5 was assayed by using a dual-luciferase reporter assay system. As a result, a novel heterozygous TBX5 mutation, p.H170D, was identified in a patient, with a mutational prevalence of approximately 0.52%. This mutation, which was absent in the 300 control individuals, altered the amino acid completely conserved evolutionarily across species, and was predicted to be disease-causing. Functional deciphers showed that the mutant TBX5 was associated with significantly reduced transcriptional activity when compared with its wild-type counterpart. Furthermore, the mutation significantly decreased the synergistic activation between TBX5 and NKX2-5 or GATA4. The findings expand the mutational spectrum of TBX5 linked to AF and provide new evidence that dysfunctional TBX5 may contribute to lone AF.
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Affiliation(s)
- Zhan-Cheng Wang
- 1. Department of Cardiology, Shanghai Eighth People's Hospital, 8 Caobao Road, Shanghai 200235, China
| | - Wen-Hui Ji
- 2. Department of Internal Medicine, Huajing Community Health Service Center of Xu Hui Distric, 180 Jianhua Road, Shanghai 200231, China
| | - Chang-Wu Ruan
- 1. Department of Cardiology, Shanghai Eighth People's Hospital, 8 Caobao Road, Shanghai 200235, China
| | - Xing-Yuan Liu
- 3. Department of Pediatrics, Tongji Hospital, Tongji University School of Medicine, 389 Xincun Road, Shanghai 200065, China
| | - Xing-Biao Qiu
- 4. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Fang Yuan
- 4. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Ruo-Gu Li
- 4. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Ying-Jia Xu
- 4. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Xu Liu
- 4. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Ru-Tai Huang
- 5. Department of Cardiovascular Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Song Xue
- 5. Department of Cardiovascular Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Yi-Qing Yang
- 4. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China;; 6. Department of Cardiovascular Research Laboratory, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China;; 7. Department of Central Laboratory, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
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Takahashi K, Sasano T, Sugiyama K, Kurokawa J, Tamura N, Soejima Y, Sawabe M, Isobe M, Furukawa T. High-fat diet increases vulnerability to atrial arrhythmia by conduction disturbance via miR-27b. J Mol Cell Cardiol 2016; 90:38-46. [PMID: 26654778 DOI: 10.1016/j.yjmcc.2015.11.034] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 11/07/2015] [Accepted: 11/30/2015] [Indexed: 02/02/2023]
Abstract
BACKGROUND Lifestyle-related diseases, such as obesity and dyslipidemia are important risk factors for atrial fibrillation (AF). However, the underlying mechanism linking these diseases and AF has not been fully investigated. METHODS Adult male mice were fed a high-fat diet (HFD) or vehicle (NC) for 2 months. Electrocardiography and in vivo electrophysiological study were performed. Mice were then sacrificed for quantification of mRNA, microRNA, and protein in atria, in addition to histological analysis. Conduction velocity (CV) in right atrium was measured by optical mapping in Langendorff perfused hearts. Cultured atrial cardiomyocytes were treated with palmitate with or without a specific microRNA inhibitor. Twelve hours after stimulation, cells were lysed, and subjected to analysis with qPCR and Western blotting. RESULTS HFD mice showed prolonged P wave duration, increased inducibility of sustained atrial tachycardia, and reduced atrial CV than NC mice. HFD mice also showed increased expression in inflammatory cytokines, whereas fibrotic area and signals relating fibrosis were not changed. HFD mice demonstrated reduced expression of Cx40 in mRNA and protein levels, and its lateralized expression in atria. MicroRNA array analysis revealed that miR-27b expression was up-regulated in HFD mice, and luciferase assay confirmed the direct interaction between miR-27b and Cx40 3'UTR. In palmitate-stimulated atrial cardiomyocytes, miR-27b up-regulation and Cx40 down-regulation were observed, while expression of inflammatory cytokines was not altered. Inhibition of miR-27b with antisense oligonucleotides reversed the alteration caused by palmitate stimulation. CONCLUSION HFD may increase the vulnerability to atrial arrhythmia by down-regulation of Cx40 via miR-27b, rather than fibrosis, which is independent of inflammation.
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Affiliation(s)
- Kentaro Takahashi
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Tetsuo Sasano
- Department of Biofunctional Informatics, Tokyo Medical and Dental University School of Health Care Sciences, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
| | - Koji Sugiyama
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Junko Kurokawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Noriko Tamura
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Yurie Soejima
- Department of Molecular Pathology, Tokyo Medical and Dental University School of Health Care Sciences, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Motoji Sawabe
- Department of Molecular Pathology, Tokyo Medical and Dental University School of Health Care Sciences, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Mitsuaki Isobe
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Tetsushi Furukawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
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Lubitz SA, Ellinor PT. Somatic mutations and atrial fibrillation: the end or just the beginning? ACTA ACUST UNITED AC 2015; 8:2-3. [PMID: 25691683 DOI: 10.1161/circgenetics.115.000963] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Steven A Lubitz
- From the Division of Cardiac Arrhythmia Service and Cardiovascular Research Center, Massachusetts General Hospital, Boston; and Medical and Population Genetics Program, The Broad Institute, Cambridge, MA
| | - Patrick T Ellinor
- From the Division of Cardiac Arrhythmia Service and Cardiovascular Research Center, Massachusetts General Hospital, Boston; and Medical and Population Genetics Program, The Broad Institute, Cambridge, MA.
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Wang Q, Hu X, Li S, Wang X, Wang J, Zhang R, Sun J, Zhang P, Feng X, Li YG. Association of the angiotensinogen M235T polymorphism with recurrence after catheter ablation of acquired atrial fibrillation. J Renin Angiotensin Aldosterone Syst 2015; 16:888-97. [PMID: 26240116 DOI: 10.1177/1470320315594315] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 05/22/2015] [Indexed: 11/15/2022] Open
Abstract
PURPOSE Previous studies showed that genetic variants of the angiotensinogen (AGT) gene conferred higher risk for acquired atrial fibrillation (AF). The present study investigated whether AGT variants correlate with the clinical outcome in patients with acquired AF after catheter ablation (CA). METHODS A total of 150 acquired symptomatic drug-refractory AF patients (mean age 63.7±11.0 years, 24.6% non-paroxysmal AF) with acquired AF underwent a single CA procedure in our department and were included in this retrospective analysis. Eight tagging single nucleotide polymorphisms (tSNPs) in the AGT gene were genotyped. Standard electrocardiographs (ECGs) and 24-hour Holter recordings were performed during a median follow-up period of 57.5 months to detect AF recurrence. RESULTS Sixty-one patients (40.7%) suffered AF recurrences after a single CA procedure during follow up. Of the eight tSNPs, the frequency of the M allele of M235T was significantly higher in the recurrence group (28%) compared to the non-recurrence group (18%) (p=0.042). The recurrence rates of patients with the TT, MT, and MM genotypes were 34.4%, 50%, and 55.6%, respectively (ptrend=0.049). After adjusting for age, sex, body mass index, hypertension, left atrial volume index (LAVI) and other covariates, M235T increased the risk of AF recurrence in additive and dominant models with odds ratios of 2.023 (95% confidence interval (CI): 1.034-3.926, p=0.033) and 2.601 (95% CI: 1.102-6.056, p=0.025), respectively. However, in multiple correction analyses, the p values of multiple comparisons were not statistically significant (pcorrect>0.05). CONCLUSIONS The M allele of M235T might be associated with an increased risk of AF recurrence after CA. Genotyping may thus be helpful on identifying patients with higher risks of AF recurrence after CA and developing optimal follow-up strategies. These strategies may differ and should be individualized according to patients' genotype. Future studies are warranted to validate the potential effect of AGT M235T on AF recurrence post CA.
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Affiliation(s)
- Qunshan Wang
- Department of Cardiology, Shanghai Jiaotong University School of Medicine, China
| | - Xiaofeng Hu
- Department of Cardiology, Zhejiang Hospital, China
| | - Shuyuan Li
- School of Life Sciences and Institutes of Biomedical Sciences, Fudan University, China
| | - Xiaofeng Wang
- School of Life Sciences and Institutes of Biomedical Sciences, Fudan University, China
| | - Jun Wang
- Department of Cardiology, Shanghai Jiaotong University School of Medicine, China
| | - Rui Zhang
- Department of Cardiology, Shanghai Jiaotong University School of Medicine, China
| | - Jian Sun
- Department of Cardiology, Shanghai Jiaotong University School of Medicine, China
| | - Pengpai Zhang
- Department of Cardiology, Shanghai Jiaotong University School of Medicine, China
| | - Xiangfei Feng
- Department of Cardiology, Shanghai Jiaotong University School of Medicine, China
| | - Yi-Gang Li
- Department of Cardiology, Shanghai Jiaotong University School of Medicine, China
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Palatinus JA, Das S. Your Father and Grandfather's Atrial Fibrillation: A Review of the Genetics of the Most Common Pathologic Cardiac Dysrhythmia. Curr Genomics 2015; 16:75-81. [PMID: 26085805 PMCID: PMC4467307 DOI: 10.2174/1389202916666150108222031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 12/24/2014] [Accepted: 01/06/2015] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) remains the most common pathologic dysrhythmia in humans with a prevalence of 1-2% of the total population and as high as 10% of the elderly. AF is an independent risk marker for cardiovascular mortality and morbidity, and given the increasing age of the population, represents an increasing burden of disease. Although age and hypertension are known risk factors for development of AF, the study of families with early onset AF revealed mutations in genes coding for ion channels and other proteins involved in electrotonic coupling as likely culprits for the pathology in select cases. Recent investigations using Genome-Wide Association Studies have revealed several single nucleotide polymorphisms (SNPs) that appear to be associated with AF and have highlighted new genes in the proximity of the SNPs that may potentially contribute to the development of the dysrhythmia. Here we review the genetics of AF and discuss how application of GWAS and next generation sequencing have advanced our knowledge of AF and further investigations may yield novel therapeutic targets for the disease.
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Affiliation(s)
- Joseph A Palatinus
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Saumya Das
- Cardiovascular Institute, Beth Israel Deaconess Medical Center, Boston, MA, USA
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59
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Christophersen IE, Ellinor PT. Genetics of atrial fibrillation: from families to genomes. J Hum Genet 2015; 61:61-70. [DOI: 10.1038/jhg.2015.44] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 03/27/2015] [Accepted: 04/07/2015] [Indexed: 12/19/2022]
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Abstract
Gene therapy to treat electrical dysfunction of the heart is an appealing strategy because of the limited therapeutic options available to manage the most-severe cardiac arrhythmias, such as ventricular tachycardia, ventricular fibrillation, and asystole. However, cardiac genetic manipulation is challenging, given the complex mechanisms underlying arrhythmias. Nevertheless, the growing understanding of the molecular basis of these diseases, and the development of sophisticated vectors and delivery strategies, are providing researchers with adequate means to target specific genes and pathways involved in disorders of heart rhythm. Data from preclinical studies have demonstrated that gene therapy can be successfully used to modify the arrhythmogenic substrate and prevent life-threatening arrhythmias. Therefore, gene therapy might plausibly become a treatment option for patients with difficult-to-manage acquired arrhythmias and for those with inherited arrhythmias. In this Review, we summarize the preclinical studies into gene therapy for acquired and inherited arrhythmias of the atria or ventricles. We also provide an overview of the technical advances in the design of constructs and viral vectors to increase the efficiency and safety of gene therapy and to improve selective delivery to target organs.
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61
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Roberts JD, Gollob MH. A contemporary review on the genetic basis of atrial fibrillation. Methodist Debakey Cardiovasc J 2015; 10:18-24. [PMID: 24932358 DOI: 10.14797/mdcj-10-1-18] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation is the most common sustained cardiac arrhythmia, and affected individuals suffer from increased rates of heart failure, stroke, and death. Despite the enormous clinical burden that it exerts on patients and health care systems, contemporary treatment strategies have only modest efficacy that likely stems from our limited understanding of its underlying pathophysiology. Epidemiological studies have provided unequivocal evidence that the arrhythmia has a substantial heritable component. Subsequent investigations into the genetics underlying atrial fibrillation have suggested that there is considerable interindividual variability in the pathophysiology characterizing the arrhythmia. This heterogeneity may partly account for the poor treatment efficacy of current therapies. Subdividing atrial fibrillation into mechanistic subtypes on the basis of genotype illustrates the heterogeneous nature of the arrhythmia and may ultimately help guide treatment strategies. A pharmacogenetic approach to the management of atrial fibrillation may lead to dramatic improvements in treatment efficacy and improved patient outcomes.
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Vecoli C, Pulignani S, Foffa I, Andreassi MG. Congenital heart disease: the crossroads of genetics, epigenetics and environment. Curr Genomics 2014; 15:390-9. [PMID: 25435801 PMCID: PMC4245698 DOI: 10.2174/1389202915666140716175634] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 06/24/2014] [Accepted: 07/07/2014] [Indexed: 02/07/2023] Open
Abstract
Congenital heart diseases (CHDs) are recognized as the most common type of birth malformations. Although recent advances in pre- and neonatal diagnosis as well as in surgical procedures have reduced the morbidity and mortality for many CHD, the etiology for CHD remains undefined. In non-syndromic and isolated (without a familial history or a Mendelian inheritance) forms of CHDs, a multifactorial pathogenesis with interplay between inherited and non-inherited causes is recognized. In this paper, we discuss the current knowledge of the potential molecular mechanisms, mediating abnormal cardiac development in non-syndromic and isolated CHD, including mutations in cardiac transcription factors, the role of somatic mutations and epigenetic alterations as well as the influence of gene-environment interactions. In the near future, the advent of high-throughput genomic technologies with the integration of system biology will expand our understanding of isolated, non-syndromic CHDs for their prevention, early diagnosis and therapy.
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Affiliation(s)
| | | | - Ilenia Foffa
- CNR, Institute of Clinical Physiology, Massa, Italy
| | - Maria Grazia Andreassi
- CNR, Institute of Clinical Physiology, Pisa, Italy ; Fondazione Toscana G.Monasterio, Massa, Italy
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63
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Nishii K, Shibata Y, Kobayashi Y. Connexin mutant embryonic stem cells and human diseases. World J Stem Cells 2014; 6:571-578. [PMID: 25426253 PMCID: PMC4178256 DOI: 10.4252/wjsc.v6.i5.571] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 09/11/2014] [Accepted: 09/17/2014] [Indexed: 02/06/2023] Open
Abstract
Intercellular communication via gap junctions allows cells within multicellular organisms to share small molecules. The effect of such interactions has been elucidated using mouse gene knockout strategies. Although several mutations in human gap junction-encoding connexin (Cx) have been described, Cx mutants in mice do not always recapitulate the human disease. Among the 20 mouse Cxs, Cx26, Cx43, and Cx45 play roles in early cardiac or placental development, and disruption of the genes results in lethality that hampers further analyses. Embryonic stem cells (ESCs) that lack Cx43 or Cx45 have made analysis feasible in both in vitro differentiated cell cultures and in vivo chimeric tissues. The success of mouse ESCs studies is leading to the use of induced pluripotent stem cells to learn more about the pathogenesis of human Cx diseases. This review summarizes the current status of mouse Cx disruption models and ESC differentiation studies, and discusses their implication for understanding human Cx diseases.
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64
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Roberts JD, Longoria J, Poon A, Gollob MH, Dewland TA, Kwok PY, Olgin JE, Deo RC, Marcus GM. Targeted deep sequencing reveals no definitive evidence for somatic mosaicism in atrial fibrillation. ACTA ACUST UNITED AC 2014; 8:50-7. [PMID: 25406240 DOI: 10.1161/circgenetics.114.000650] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Studies of ≤15 atrial fibrillation (AF) patients have identified atrial-specific mutations within connexin genes, suggesting that somatic mutations may account for sporadic cases of the arrhythmia. We sought to identify atrial somatic mutations among patients with and without AF using targeted deep next-generation sequencing of 560 genes, including genetic culprits implicated in AF, the Mendelian cardiomyopathies and channelopathies, and all ion channels within the genome. METHODS AND RESULTS Targeted gene capture and next-generation sequencing were performed on DNA from lymphocytes and left atrial appendages of 34 patients (25 with AF). Twenty AF patients had undergone cardiac surgery exclusively for pulmonary vein isolation and 17 had no structural heart disease. Sequence alignment and variant calling were performed for each atrial-lymphocyte pair using the Burrows-Wheeler Aligner, the Genome Analysis Toolkit, and MuTect packages. Next-generation sequencing yielded a median 265-fold coverage depth (interquartile range, 64-369). Comparison of the 3 million base pairs from each atrial-lymphocyte pair revealed a single potential somatic missense mutation in 3 AF patients and 2 in a single control (12 versus 11%; P=1). All potential discordant variants had low allelic fractions (range, 2.3%-7.3%) and none were detected with conventional sequencing. CONCLUSIONS Using high-depth next-generation sequencing and state-of-the art somatic mutation calling approaches, no pathogenic atrial somatic mutations could be confirmed among 25 AF patients in a comprehensive cardiac arrhythmia genetic panel. These findings indicate that atrial-specific mutations are rare and that somatic mosaicism is unlikely to exert a prominent role in AF pathogenesis.
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Affiliation(s)
- Jason D Roberts
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.)
| | - James Longoria
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.)
| | - Annie Poon
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.)
| | - Michael H Gollob
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.)
| | - Thomas A Dewland
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.)
| | - Pui-Yan Kwok
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.)
| | - Jeffrey E Olgin
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.)
| | - Rahul C Deo
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.).
| | - Gregory M Marcus
- From the Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine (J.D.R., T.A.D., J.E.O., G.M.M.), Cardiovascular Research Institute (A.P., P.-Y.K., R.C.D.), and Department of Medicine, California Institute for Quantitative Biosciences, Institute for Human Genetics (R.C.D.), University of California San Francisco; Division of Cardiovascular Surgery, Sutter Health, Sacramento, CA (J.L.); and Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (M.H.G.).
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Kleber AG, Saffitz JE. Role of the intercalated disc in cardiac propagation and arrhythmogenesis. Front Physiol 2014; 5:404. [PMID: 25368581 PMCID: PMC4201087 DOI: 10.3389/fphys.2014.00404] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 09/30/2014] [Indexed: 01/28/2023] Open
Abstract
This review article discusses mechanisms underlying impulse propagation in cardiac muscle with specific emphasis on the role of the cardiac cell-to-cell junction, called the “intercalated disc.”The first part of this review deals with the role of gap junction channels, formed by connexin proteins, as a determinant of impulse propagation. It is shown that, depending on the underlying structure of the cellular network, decreasing the conductance of gap junction channels (so-called “electrical uncoupling”) may either only slow, or additionally stabilize propagation and reverse unidirectional propagation block to bidirectional propagation. This is because the safety factor for propagation increases with decreasing intercellular electrical conductance. The role of heterogeneous connexin expression, which may be present in disease states, is also discussed. The hypothesis that so-called ephaptic impulse transmission plays a role in heart and can substitute for electrical coupling has been revived recently. Whereas ephaptic transmission can be demonstrated in theoretical simulations, direct experimental evidence has not yet been presented. The second part of this review deals with the interaction of three protein complexes at the intercalated disc: (1) desmosomal and adherens junction proteins, (2) ion channel proteins, and (3) gap junction channels consisting of connexins. Recent work has revealed multiple interactions between these three protein complexes which occur, at least in part, at the level of protein trafficking. Such interactions are likely to play an important role in the pathogenesis of arrhythmogenic cardiomyopathy, and may reveal new therapeutic concepts and targets.
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Affiliation(s)
- Andre G Kleber
- Department of Pathology, Beth Israel Medical Center, Harvard Medical School Boston, MA, USA
| | - Jeffrey E Saffitz
- Department of Pathology, Beth Israel Medical Center, Harvard Medical School Boston, MA, USA
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Wang J, Zhang DF, Sun YM, Li RG, Qiu XB, Qu XK, Liu X, Fang WY, Yang YQ. NKX2-6 mutation predisposes to familial atrial fibrillation. Int J Mol Med 2014; 34:1581-90. [PMID: 25319568 DOI: 10.3892/ijmm.2014.1971] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Accepted: 10/10/2014] [Indexed: 12/29/2022] Open
Abstract
Atrial fibrillation (AF) is the most common form of sustained cardiac arrhythmia and is associated with substantially increased morbidity and mortality rates. Aggregating evidence demonstrates that genetic defects are involved in the pathogenesis of AF and a number of AF-associated genes have been identified. Nevertheless, AF is a genetically heterogeneous disorder and the genetic components underpinning AF in an overwhelming majority of patients remain unclear. In this study, the entire coding exons and splice junction sites of the NK2 homeobox 6 (NKX2-6) gene, which encodes a homeodomain transcription factor important for cardiovascular development, were sequenced in 150 unrelated patients with lone AF, and a novel heterozygous NKX2-6 mutation, p.Q175H, was identified in an index patient. Genetic analysis of the available family members of the mutation carrier revealed that the mutation co-segregated with AF transmitted in an autosomal dominant pattern. The missense mutation was absent in the 200 unrelated ethnically matched healthy individuals used as controls and the altered amino acid was completely conserved evolutionarily among species. Due to unknown transcriptional targets of NKX2-6, the functional characteristics of the mutation as regards transcriptional activity were analyzed using NKX2-5 as a surrogate. Alignment between human NKX2-6 and NKX2-5 proteins displayed that the Q175H-mutant NKX2-6 was equivalent to the Q181H-mutant NKX2-5, and the introduction of Q181H into NKX2-5 significantly decreased its transcriptional activity at the atrial natriuretic factor promoter. The present study firstly associates genetically defective NKX2-6 with enhanced susceptibility to AF, providing novel insight into the molecular mechanisms underlying AF and suggesting potential strategies for the antenatal prophylaxis and personalized treatment of AF.
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Affiliation(s)
- Jun Wang
- Department of Cardiology, East Hospital, Tongji University School of Medicine, Shanghai 200120, P.R. China
| | - Dai-Fu Zhang
- Department of Cardiology, East Hospital, Tongji University School of Medicine, Shanghai 200120, P.R. China
| | - Yu-Min Sun
- Department of Cardiology, Jing-An District Central Hospital, Shanghai 200040, P.R. China
| | - Ruo-Gu Li
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
| | - Xing-Biao Qiu
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
| | - Xin-Kai Qu
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
| | - Xu Liu
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
| | - Wei-Yi Fang
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
| | - Yi-Qing Yang
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
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67
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Sinner MF, Tucker NR, Lunetta KL, Ozaki K, Smith JG, Trompet S, Bis JC, Lin H, Chung MK, Nielsen JB, Lubitz SA, Krijthe BP, Magnani JW, Ye J, Gollob MH, Tsunoda T, Müller-Nurasyid M, Lichtner P, Peters A, Dolmatova E, Kubo M, Smith JD, Psaty BM, Smith NL, Jukema JW, Chasman DI, Albert CM, Ebana Y, Furukawa T, MacFarlane P, Harris TB, Darbar D, Dörr M, Holst AG, Svendsen JH, Hofman A, Uitterlinden AG, Gudnason V, Isobe M, Malik R, Dichgans M, Rosand J, Van Wagoner DR, Benjamin EJ, Milan DJ, Melander O, Heckbert SR, Ford I, Liu Y, Barnard J, Olesen MS, Stricker BH, Tanaka T, Kääb S, Ellinor PT. Integrating genetic, transcriptional, and functional analyses to identify 5 novel genes for atrial fibrillation. Circulation 2014; 130:1225-35. [PMID: 25124494 PMCID: PMC4190011 DOI: 10.1161/circulationaha.114.009892] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 08/01/2014] [Indexed: 01/11/2023]
Abstract
BACKGROUND Atrial fibrillation (AF) affects >30 million individuals worldwide and is associated with an increased risk of stroke, heart failure, and death. AF is highly heritable, yet the genetic basis for the arrhythmia remains incompletely understood. METHODS AND RESULTS To identify new AF-related genes, we used a multifaceted approach, combining large-scale genotyping in 2 ethnically distinct populations, cis-eQTL (expression quantitative trait loci) mapping, and functional validation. Four novel loci were identified in individuals of European descent near the genes NEURL (rs12415501; relative risk [RR]=1.18; 95% confidence interval [CI], 1.13-1.23; P=6.5×10(-16)), GJA1 (rs13216675; RR=1.10; 95% CI, 1.06-1.14; P=2.2×10(-8)), TBX5 (rs10507248; RR=1.12; 95% CI, 1.08-1.16; P=5.7×10(-11)), and CAND2 (rs4642101; RR=1.10; 95% CI, 1.06-1.14; P=9.8×10(-9)). In Japanese, novel loci were identified near NEURL (rs6584555; RR=1.32; 95% CI, 1.26-1.39; P=2.0×10(-25)) and CUX2 (rs6490029; RR=1.12; 95% CI, 1.08-1.16; P=3.9×10(-9)). The top single-nucleotide polymorphisms or their proxies were identified as cis-eQTLs for the genes CAND2 (P=2.6×10(-19)), GJA1 (P=2.66×10(-6)), and TBX5 (P=1.36×10(-5)). Knockdown of the zebrafish orthologs of NEURL and CAND2 resulted in prolongation of the atrial action potential duration (17% and 45%, respectively). CONCLUSIONS We have identified 5 novel loci for AF. Our results expand the diversity of genetic pathways implicated in AF and provide novel molecular targets for future biological and pharmacological investigation.
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Affiliation(s)
- Moritz F. Sinner
- Department of Medicine I, University Hospital Munich, Campus Grosshadern, Ludwig-Maximilians-University, Munich, Germany
| | - Nathan R. Tucker
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA
| | - Kathryn L. Lunetta
- Department of Biostatistics, Boston University School of Public Health, Boston, MA
- National Heart, Lung and Blood Institute’s and Boston University's Framingham Heart Study, Framingham, MA
| | - Kouichi Ozaki
- Laboratory for Cardiovascular Diseases, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - J. Gustav Smith
- Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, MA
- Department of Cardiology, Lund University, Lund, Sweden
| | - Stella Trompet
- Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Joshua C. Bis
- Cardiovascular Health Research Unit, University of Washington, Seattle, WA
- Department of Medicine, University of Washington, Seattle, WA
| | - Honghuang Lin
- National Heart, Lung and Blood Institute’s and Boston University's Framingham Heart Study, Framingham, MA
- Computational Biomedicine Section, Department of Medicine, Boston University School of Medicine, Boston, MA
| | - Mina K. Chung
- Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | - Jonas B. Nielsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Copenhagen, Denmark
- Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Steven A. Lubitz
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA
- Cardiac Arrhythmia Service, Masschusetts General Hospital, Boston, MA
| | - Bouwe P. Krijthe
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Consortium for Healthy Aging (NCHA), Netherlands
| | - Jared W. Magnani
- Cardiology Section, Department of Medicine, Boston University School of Medicine, Boston, MA
| | - Jiangchuan Ye
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA
| | - Michael H. Gollob
- Arrhythmia Research Laboratory, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
| | - Tatsuhiko Tsunoda
- Laboratory for Medical Science Mathematics, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Martina Müller-Nurasyid
- Department of Medicine I, University Hospital Munich, Campus Grosshadern, Ludwig-Maximilians-University, Munich, Germany
- Institute of Genetic Epidemiology, Helmholtz Zentrum München - German Research Center for Environmental Health, Neuherberg, Germany
- Institute of Medical Informatics, Biometry and Epidemiology, Ludwig-Maximilians-University, Munich, Germany
| | - Peter Lichtner
- Institute of Human Genetics, Helmholtz Zentrum München - German Research Center for Environmental Health, Neuherberg, Germany
| | - Annette Peters
- Deutsches Zentrum für Herz- Kreislaufforschung e.V. (DZHK), partner site Munich Heart Alliance, Munich, Germany
- Institute of Epidemiology II, Helmholtz Zentrum München - German Research Center for Environmental Health, Neuherberg, Germany
| | - Elena Dolmatova
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA
| | - Michiaki Kubo
- Laboratory for Genotyping Development, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Jonathan D. Smith
- Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH
- Department of Cellular & Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | - Bruce M. Psaty
- Cardiovascular Health Research Unit, University of Washington, Seattle, WA
- Group Health Research Institute, Group Helath Cooperative, Seattle, WA
- Department of Epidemiology, University of Washington, Seattle, WA
- Department of Health Services, University of Washington, Seattle, WA
| | - Nicholas L. Smith
- Cardiovascular Health Research Unit, University of Washington, Seattle, WA
- Group Health Research Institute, Group Helath Cooperative, Seattle, WA
- Department of Epidemiology, University of Washington, Seattle, WA
- Epidemiologic Research and Information Center of the Department of Veterans Affairs Office of Research and Development, Seattle, WA
| | - J. Wouter Jukema
- Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
- Interuniversity Cardiology Institute of the Netherlands, Utrecht, The Netherlands
| | - Daniel I. Chasman
- Division of Preventive Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA
| | - Christine M. Albert
- Division of Preventive Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA
- Division of Cardiovascular Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA
| | - Yusuke Ebana
- Department of Bio-Informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tetsushi Furukawa
- Department of Bio-Informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Peter MacFarlane
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, UK
| | - Tamara B. Harris
- Laboratory of Epidemiology, Demography, and Biometry, Intramural Research Program, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Dawood Darbar
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
| | - Marcus Dörr
- Department of Internal Medicine B, Ernst Moritz Arndt University Greifswald, Greifswald, Germany
| | - Anders G. Holst
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Copenhagen, Denmark
- Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Jesper H. Svendsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Copenhagen, Denmark
- Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Department of Clinical Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Albert Hofman
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Consortium for Healthy Aging (NCHA), Netherlands
| | - Andre G. Uitterlinden
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Consortium for Healthy Aging (NCHA), Netherlands
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Vilmundur Gudnason
- Icelandic Heart Association Research Institute, Kopavogur, Iceland
- University of Iceland, Reykjavik, Iceland
| | - Mitsuaki Isobe
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Japan
| | - Rainer Malik
- Institute for Stroke and Dementia Research, University Hospital Munich, Ludwig-Maximilians-University, Munich, Germany
| | - Martin Dichgans
- Institute for Stroke and Dementia Research, University Hospital Munich, Ludwig-Maximilians-University, Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Jonathan Rosand
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA
- Department of Neurology, Massachusetts General Hospital, Boston, MA
- Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, MA
| | - David R. Van Wagoner
- Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | | | - Emelia J. Benjamin
- National Heart, Lung and Blood Institute’s and Boston University's Framingham Heart Study, Framingham, MA
- Cardiology Section, Department of Medicine, Boston University School of Medicine, Boston, MA
- Department of Epidemiology, Boston University School of Public Health, Boston, MA
- Preventive Medicine Section, Department of Medicine, Boston University School of Medicine, Boston, MA
| | - David J. Milan
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA
- Cardiac Arrhythmia Service, Masschusetts General Hospital, Boston, MA
| | - Olle Melander
- Department of Clinical Sciences, Lund University, Malmo, Sweden
| | - Susan R. Heckbert
- Cardiovascular Health Research Unit, University of Washington, Seattle, WA
- Group Health Research Institute, Group Helath Cooperative, Seattle, WA
- Department of Epidemiology, University of Washington, Seattle, WA
| | - Ian Ford
- Robertson Centre for Biostatistics, University of Glasgow, Glasgow, UK
| | - Yongmei Liu
- Department of Epidemiology & Prevention, Public Health Sciences, Wake Forest School of Medicine, Winston Salem, NC
| | - John Barnard
- Department of Quantitative Health Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | - Morten S. Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Copenhagen, Denmark
- Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Bruno H.C. Stricker
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Consortium for Healthy Aging (NCHA), Netherlands
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
- Inspectorate for Health Care, the Hague, The Netherlands
- Department of Medical Informatics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Toshihiro Tanaka
- Laboratory for Cardiovascular Diseases, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
- Department of Human Genetics and Disease Diversity, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Stefan Kääb
- Department of Medicine I, University Hospital Munich, Campus Grosshadern, Ludwig-Maximilians-University, Munich, Germany
- Deutsches Zentrum für Herz- Kreislaufforschung e.V. (DZHK), partner site Munich Heart Alliance, Munich, Germany
| | - Patrick T. Ellinor
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA
- Cardiac Arrhythmia Service, Masschusetts General Hospital, Boston, MA
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA
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Zhang SS, Shaw RM. Trafficking highways to the intercalated disc: new insights unlocking the specificity of connexin 43 localization. ACTA ACUST UNITED AC 2014; 21:43-54. [PMID: 24460200 DOI: 10.3109/15419061.2013.876014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
With each heartbeat, billions of cardiomyocytes work in concert to propagate the electrical excitation needed to effectively circulate blood. Regulated expression and timely delivery of connexin proteins to form gap junctions at the specialized cell-cell contact region, known as the intercalated disc, is essential to ventricular cardiomyocyte coupling. We focus this review on several regulatory mechanisms that have been recently found to govern the lifecycle of connexin 43 (Cx43), the short-lived and most abundantly expressed connexin in cardiac ventricular muscle. The Cx43 lifecycle begins with gene expression, followed by oligomerization into hexameric channels, and then cytoskeletal-based transport toward the disc region. Once delivered, hemichannels interact with resident disc proteins and are organized to effect intercellular coupling. We highlight recent studies exploring regulation of Cx43 localization to the intercalated disc, with emphasis on alternatively translated Cx43 isoforms and cytoskeletal transport machinery that together regulate Cx43 gap junction coupling between cardiomyocytes.
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Prudat Y, Kucera JP. Nonlinear behaviour of conduction and block in cardiac tissue with heterogeneous expression of connexin 43. J Mol Cell Cardiol 2014; 76:46-54. [PMID: 25128085 DOI: 10.1016/j.yjmcc.2014.07.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/25/2014] [Accepted: 07/31/2014] [Indexed: 11/18/2022]
Abstract
Altered gap junctional coupling potentiates slow conduction and arrhythmias. To better understand how heterogeneous connexin expression affects conduction at the cellular scale, we investigated conduction in tissue consisting of two cardiomyocyte populations expressing different connexin levels. Conduction was mapped using microelectrode arrays in cultured strands of foetal murine ventricular myocytes with predefined contents of connexin 43 knockout (Cx43KO) cells. Corresponding computer simulations were run in randomly generated two-dimensional tissues mimicking the cellular architecture of the strands. In the cultures, the relationship between conduction velocity (CV) and Cx43KO cell content was nonlinear. CV first decreased significantly when Cx43KO content was increased from 0 to 50%. When the Cx43KO content was ≥60%, CV became comparable to that in 100% Cx43KO strands. Co-culturing Cx43KO and wild-type cells also resulted in significantly more heterogeneous conduction patterns and in frequent conduction blocks. The simulations replicated this behaviour of conduction. For Cx43KO contents of 10-50%, conduction was slowed due to wavefront meandering between Cx43KO cells. For Cx43KO contents ≥60%, clusters of remaining wild-type cells acted as electrical loads that impaired conduction. For Cx43KO contents of 40-60%, conduction exhibited fractal characteristics, was prone to block, and was more sensitive to changes in ion currents compared to homogeneous tissue. In conclusion, conduction velocity and stability behave in a nonlinear manner when cardiomyocytes expressing different connexin amounts are combined. This behaviour results from heterogeneous current-to-load relationships at the cellular level. Such behaviour is likely to be arrhythmogenic in various clinical contexts in which gap junctional coupling is heterogeneous.
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Affiliation(s)
- Yann Prudat
- Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
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Molica F, Meens MJP, Morel S, Kwak BR. Mutations in cardiovascular connexin genes. Biol Cell 2014; 106:269-93. [PMID: 24966059 DOI: 10.1111/boc.201400038] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 06/20/2014] [Indexed: 12/25/2022]
Abstract
Connexins (Cxs) form a family of transmembrane proteins comprising 21 members in humans. Cxs differ in their expression patterns, biophysical properties and ability to combine into homomeric or heteromeric gap junction channels between neighbouring cells. The permeation of ions and small metabolites through gap junction channels or hemichannels confers a crucial role to these proteins in intercellular communication and in maintaining tissue homeostasis. Among others, Cx37, Cx40, Cx43, Cx45 and Cx47 are found in heart, blood and lymphatic vessels. Mutations or polymorphisms in the genes coding for these Cxs have not only been implicated in cardiovascular pathologies but also in a variety of other disorders. While mutations in Cx43 are mostly linked to oculodentodigital dysplasia, Cx47 mutations are associated with Pelizaeus-Merzbacher-like disease and lymphoedema. Cx40 mutations are principally linked to atrial fibrillation. Mutations in Cx37 have not yet been described, but polymorphisms in the Cx37 gene have been implicated in the development of arterial disease. This review addresses current knowledge on gene mutations in cardiovascular Cxs systematically and links them to alterations in channel properties and disease.
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Affiliation(s)
- Filippo Molica
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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Downregulation of connexin43 by microRNA-130a in cardiomyocytes results in cardiac arrhythmias. J Mol Cell Cardiol 2014; 74:53-63. [PMID: 24819345 DOI: 10.1016/j.yjmcc.2014.04.024] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 04/23/2014] [Accepted: 04/25/2014] [Indexed: 01/17/2023]
Abstract
MicroRNAs (miRNAs) are now recognized as critical regulators of diverse physiological and pathological processes; however, studies of miRNAs and arrhythmogenesis remain sparse. Connexin43 (Cx43), a major cardiac gap junction protein, has elicited great interest in its role in arrhythmias. Additionally, Cx43 was a potential target for miR-130a as predicted by several computational algorithms. This study investigates the effect of miR-130a overexpression in the adult heart and its effect on cardiac rhythm. Using a cardiac-specific inducible system, transgenic mice demonstrated both atrial and ventricular arrhythmias. We performed ventricular-programmed electrical stimulation and found that the αMHC-miR130a mice developed sustained ventricular tachycardia beginning 6weeks after overexpression. Western blot analysis demonstrated a steady decline in Cx43 after 2weeks of overexpression with over a 90% reduction in Cx43 levels by 10weeks. Immunofluorescent staining confirmed a near complete loss of Cx43 throughout the heart. To validate Cx43 as a direct target of miR-130a, we performed in vitro target assays in 3T3 fibroblasts and HL-1 cardiomyocytes, both known to endogenously express miR-130a. Using a luciferase reporter fused to the 3'UTR of Cx43, we found a 52.9% reduction in luciferase activity in 3T3 cells (p<0.0001) and a 47.6% reduction in HL-1 cells (p=0.0056) compared to controls. Addition of an antisense miR-130a inhibitor resulted in a loss of inhibitory activity of the Cx43 3'UTR reporter. We have identified an unappreciated role for miR-130a as a direct regulator of Cx43. Overexpression of miR-130a may contribute importantly to gap junction remodeling and to the pathogenesis of atrial and ventricular arrhythmias.
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Sun Y, Tong X, Chen H, Huang T, Shao Q, Huang W, Laird DW, Bai D. An atrial-fibrillation-linked connexin40 mutant is retained in the endoplasmic reticulum and impairs the function of atrial gap-junction channels. Dis Model Mech 2014; 7:561-9. [PMID: 24626989 PMCID: PMC4007407 DOI: 10.1242/dmm.013813] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 03/11/2014] [Indexed: 12/18/2022] Open
Abstract
Connexin40 (Cx40)-containing gap-junction channels are expressed in the atrial myocardium and provide a low-resistance passage for rapid impulse propagation. A germline mutation in the GJA5 gene, which encodes Cx40, resulting in a truncated Cx40 (Q49X) was identified in a large Chinese family with lone (idiopathic) atrial fibrillation (AF). This mutation co-segregated with seven AF probands in an autosomal-dominant way over generations. To test the hypothesis that this Cx40 mutant affects the distribution and function of atrial gap junctions, we studied the Q49X mutant in gap-junction-deficient HeLa and N2A cells. The Q49X mutant, unlike wild-type Cx40, was typically localized in the cytoplasm and failed to form gap-junction plaques at cell-cell interfaces. When the Q49X mutant was co-expressed with Cx40 or Cx43, the mutant substantially reduced the gap-junction plaque formation of Cx40 and Cx43. Electrophysiological studies revealed no electrical coupling of cell pairs expressing the mutant alone and a significant decrease in the coupling conductance when the mutant was co-expressed with Cx40 or Cx43. Further colocalization experiments with the organelle residential proteins indicate that Q49X was retained in the endoplasmic reticulum. These findings provide evidence that the Q49X mutant is capable of impairing gap-junction distribution and function of key atrial connexins, which might play a role in the predisposition to and onset of AF.
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Affiliation(s)
- Yiguo Sun
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Xiaoling Tong
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Honghong Chen
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Tao Huang
- Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Qing Shao
- Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Weixiong Huang
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Dale W. Laird
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
- Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Donglin Bai
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
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74
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Patel D, Gemel J, Xu Q, Simon AR, Lin X, Matiukas A, Beyer EC, Veenstra RD. Atrial fibrillation-associated connexin40 mutants make hemichannels and synergistically form gap junction channels with novel properties. FEBS Lett 2014; 588:1458-64. [PMID: 24457199 PMCID: PMC3989446 DOI: 10.1016/j.febslet.2014.01.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 01/10/2014] [Accepted: 01/13/2014] [Indexed: 01/08/2023]
Abstract
Mutations of Cx40 (GJA5) have been identified in people with lone chronic atrial fibrillation including G38D and M163V which were found in the same patient. We used dual whole cell patch clamp procedures to examine the transjunctional voltage (Vj) gating and channel conductance properties of these two rare mutants. Each mutant exhibited slight alterations of Vj gating properties and increased the gap junction channel conductance (γj) by 20-30 pS. While co-expression of the two mutations had similar effects on Vj gating, it synergistically increased γj by 50%. Unlike WTCx40 or M163V, G38D induced activity of a dominant 271 pS hemichannel.
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Affiliation(s)
- Dakshesh Patel
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Joanna Gemel
- Department of Pediatrics, University of Chicago, Chicago, IL 60637, United States
| | - Qin Xu
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Adria R Simon
- Department of Pediatrics, University of Chicago, Chicago, IL 60637, United States
| | - Xianming Lin
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Arvydas Matiukas
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Eric C Beyer
- Department of Pediatrics, University of Chicago, Chicago, IL 60637, United States
| | - Richard D Veenstra
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States; Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY 13210, United States.
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75
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Bai D. Atrial fibrillation-linked GJA5/connexin40 mutants impaired gap junctions via different mechanisms. FEBS Lett 2014; 588:1238-43. [PMID: 24656738 DOI: 10.1016/j.febslet.2014.02.064] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/05/2014] [Accepted: 02/06/2014] [Indexed: 01/08/2023]
Abstract
The gap junctions (GJs) formed by Cx40 and Cx43 provide a low resistance passage allowing for rapid propagation of action potentials. Sporadic somatic mutations in GJA5 (encoding Cx40) have been identified in lone atrial fibrillation (AF) patients. More recently germline autosomal dominantly inherited mutations in GJA5 have been found in early onset lone AF patients in several families over generations. Characterizations of these AF-linked Cx40 mutants in model cells and in patient tissues revealed that some of the mutants reduced GJ channel function due to an impaired trafficking or channel formation. While others showed a gain-of-function in hemichannels. These functional alterations in GJs or hemichannel may play an important role in the pathogenesis of AF in the mutant carriers.
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Affiliation(s)
- Donglin Bai
- Department of Physiology and Pharmacology, Western University, London, Ontario N6A 5C1, Canada.
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76
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Extracellular domains play different roles in gap junction formation and docking compatibility. Biochem J 2014; 458:1-10. [PMID: 24438327 DOI: 10.1042/bj20131162] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
GJ (gap junction) channels mediate direct intercellular communication and play an important role in many physiological processes. Six connexins oligomerize to form a hemichannel and two hemichannels dock together end-to-end to form a GJ channel. Connexin extracellular domains (E1 and E2) have been shown to be important for the docking, but the molecular mechanisms behind the docking and formation of GJ channels are not clear. Recent developments in atomic GJ structure and functional studies on a series of connexin mutants revealed that E1 and E2 are likely to play different roles in the docking. Non-covalent interactions at the docking interface, including hydrogen bonds, are predicted to form between interdocked extracellular domains. Protein sequence alignment analysis on the docking compatible/incompatible connexins indicate that the E1 domain is important for the formation of the GJ channel and the E2 domain is important in the docking compatibility in heterotypic channels. Interestingly, the hydrogen-bond forming or equivalent residues in both E1 and E2 domains are mutational hot spots for connexin-linked human diseases. Understanding the molecular mechanisms of GJ docking can assist us to develop novel strategies in rescuing the disease-linked connexin mutants.
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77
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Sun Y, Hills MD, Ye WG, Tong X, Bai D. Atrial fibrillation-linked germline GJA5/connexin40 mutants showed an increased hemichannel function. PLoS One 2014; 9:e95125. [PMID: 24733048 PMCID: PMC3986259 DOI: 10.1371/journal.pone.0095125] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 03/24/2014] [Indexed: 01/08/2023] Open
Abstract
Mutations in GJA5 encoding the gap junction protein connexin40 (Cx40) have been linked to lone atrial fibrillation. Some of these mutants result in impaired gap junction function due to either abnormal connexin localization or impaired gap junction channels, which may play a role in promoting atrial fibrillation. However, the effects of the atrial fibrillation-linked Cx40 mutants on hemichannel function have not been studied. Here we investigated two atrial fibrillation-linked germline Cx40 mutants, V85I and L221I. These two mutants formed putative gap junction plaques at cell-cell interfaces, with similar gap junction coupling conductance as that of wild-type Cx40. Connexin deficient HeLa cells expressing either one of these two mutants displayed prominent propidium iodide-uptake distinct from cells expressing wild-type Cx40 or other atrial fibrillation-linked Cx40 mutants, I75F, L229M, and Q49X. Propidium iodide-uptake was sensitive to [Ca2+]o and the hemichannel blockers, carbenoxolone, flufenamic acid and mefloquine, but was not affected by the pannexin 1 channel blocking agent, probenecid, indicating that uptake is most likely mediated via connexin hemichannels. A gain-of-hemichannel function in these two atrial fibrillation-linked Cx40 mutants may provide a novel mechanism underlying the etiology of atrial fibrillation.
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Affiliation(s)
- Yiguo Sun
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - Matthew D. Hills
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - Willy G. Ye
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - Xiaoling Tong
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - Donglin Bai
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
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78
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Dhillon PS, Chowdhury RA, Patel PM, Jabr R, Momin AU, Vecht J, Gray R, Shipolini A, Fry CH, Peters NS. Relationship between connexin expression and gap-junction resistivity in human atrial myocardium. Circ Arrhythm Electrophysiol 2014; 7:321-9. [PMID: 24610741 DOI: 10.1161/circep.113.000606] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The relative roles of the gap-junctional proteins connexin40 (Cx40) and connexin43 (Cx43) in determining human atrial myocardial resistivity is unknown. In addressing the hypothesis that changing relative expression of Cx40 and Cx43 underlies an increase in human atrial myocardial resistivity with age, this relationship was investigated by direct ex vivo measurement of gap-junctional resistivity and quantitative connexin immunoblotting and immunohistochemistry. METHODS AND RESULTS Oil-gap impedance measurements were performed to determine resistivity of the intracellular pathway (Ri), which correlated with total Cx40 quantification by Western blotting (rs=0.64, P<0.01, n=20). Specific gap-junctional resistivity (Rj) correlated not only with Western immunoquantification of Cx40 (rs=0.63, P=0.01, n=20), but also more specifically, with the Cx40 fraction localized to the intercalated disks on immunohistochemical quantification (rs=0.66, P=0.02, n=12). Although Cx43 expression showed no correlation with resistivity values, the proportional expression of the 2 connexins, (Cx40/[Cx40+Cx43]) correlated with Ri and Rj (rs=0.58, P<0.01 for Ri and rs=0.51, P=0.02 for Rj). Advancing age was associated with a rise in Ri (rs=0.77, P<0.0001), Rj (rs=0.65, P<0.001, n=23), Cx40 quantity (rs=0.54, P=0.01, n=20), and Cx40 gap-junction protein per unit area of en face disk (rs=0.61, P=0.02, n=12). CONCLUSIONS Cx40 is associated with human right atrial gap-junctional resistivity such that increased total, gap-junctional, and proportional Cx40 expression increases gap-junctional resistivity. Accordingly, advancing age is associated with an increase in Cx40 expression and a corresponding increase in gap-junctional resistivity. These findings are the first to demonstrate this relationship and a mechanistic explanation for changing atrial conduction and age-related arrhythmic tendency.
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Affiliation(s)
- Paramdeep S Dhillon
- Myocardial Function Section, Imperial College London and Imperial College NHS Trust, London, UK
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79
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Nagata N, Yamanaka S. Perspectives for induced pluripotent stem cell technology: new insights into human physiology involved in somatic mosaicism. Circ Res 2014; 114:505-10. [PMID: 24481841 DOI: 10.1161/circresaha.114.303043] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Induced pluripotent stem cell technology makes in vitro reprogramming of somatic cells from individuals with various genetic backgrounds possible. By applying this technology, it is possible to produce pluripotent stem cells from biopsy samples of arbitrarily selected individuals with various genetic backgrounds and to subsequently maintain, expand, and stock these cells. From these induced pluripotent stem cells, target cells and tissues can be generated after certain differentiation processes. These target cells/tissues are expected to be useful in regenerative medicine, disease modeling, drug screening, toxicology testing, and proof-of-concept studies in drug development. Therefore, the number of publications concerning induced pluripotent stem cells has recently been increasing rapidly, demonstrating that this technology has begun to infiltrate many aspects of stem cell biology and medical applications. In this review, we discuss the perspectives of induced pluripotent stem cell technology for modeling human diseases. In particular, we focus on the cloning event occurring through the reprogramming process and its ability to let us analyze the development of complex disease-harboring somatic mosaicism.
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Affiliation(s)
- Naoki Nagata
- From the Department of Reprogramming Science, Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto, Japan (N.N., S.Y.); and Gladstone Institute of Cardiovascular Disease, San Francisco, CA (S.Y.)
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80
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Olesen MS, Nielsen MW, Haunsø S, Svendsen JH. Atrial fibrillation: the role of common and rare genetic variants. Eur J Hum Genet 2014; 22:297-306. [PMID: 23838598 PMCID: PMC3925267 DOI: 10.1038/ejhg.2013.139] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 04/28/2013] [Accepted: 05/27/2013] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia affecting 1-2% of the general population. A number of studies have demonstrated that AF, and in particular lone AF, has a substantial genetic component. Monogenic mutations in lone and familial AF, although rare, have been recognized for many years. Presently, mutations in 25 genes have been associated with AF. However, the complexity of monogenic AF is illustrated by the recent finding that both gain- and loss-of-function mutations in the same gene can cause AF. Genome-wide association studies (GWAS) have indicated that common single-nucleotide polymorphisms (SNPs) have a role in the development of AF. Following the first GWAS discovering the association between PITX2 and AF, several new GWAS reports have identified SNPs associated with susceptibility of AF. To date, nine SNPs have been associated with AF. The exact biological pathways involving these SNPs and the development of AF are now starting to be elucidated. Since the first GWAS, the number of papers concerning the genetic basis of AF has increased drastically and the majority of these papers are for the first time included in a review. In this review, we discuss the genetic basis of AF and the role of both common and rare genetic variants in the susceptibility of developing AF. Furthermore, all rare variants reported to be associated with AF were systematically searched for in the Exome Sequencing Project Exome Variant Server.
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Affiliation(s)
- Morten S Olesen
- The Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark
- Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Morten W Nielsen
- The Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark
- Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Stig Haunsø
- The Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark
- Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Department of Surgery and Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jesper H Svendsen
- The Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark
- Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Department of Surgery and Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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81
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Schumacher-Bass SM, Vesely ED, Zhang L, Ryland KE, McEwen DP, Chan PJ, Frasier CR, McIntyre JC, Shaw RM, Martens JR. Role for myosin-V motor proteins in the selective delivery of Kv channel isoforms to the membrane surface of cardiac myocytes. Circ Res 2014; 114:982-92. [PMID: 24508725 DOI: 10.1161/circresaha.114.302711] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Kv1.5 (KCNA5) mediates the ultra-rapid delayed rectifier current that controls atrial action potential duration. Given its atrial-specific expression and alterations in human atrial fibrillation, Kv1.5 has emerged as a promising target for the treatment of atrial fibrillation. A necessary step in the development of novel agents that selectively modulate trafficking pathways is the identification of the cellular machinery controlling Kv1.5 surface density, of which little is yet known. OBJECTIVE To investigate the role of the unconventional myosin-V (MYO5A and MYO5B) motors in determining the cell surface density of Kv1.5. METHODS AND RESULTS Western blot analysis showed MYO5A and MYO5B expression in the heart, whereas disruption of endogenous motors selectively reduced IKur current in adult rat cardiomyocytes. Dominant negative constructs and short hairpin RNA silencing demonstrated a role for MYO5A and MYO5B in the surface trafficking of Kv1.5 and connexin-43 but not potassium voltage-gated channel, subfamily H (eag-related), member 2 (KCNH2). Live-cell imaging of Kv1.5-GFP and retrospective labeling of phalloidin demonstrated motility of Kv1.5 vesicles on actin tracts. MYO5A participated in anterograde trafficking, whereas MYO5B regulated postendocytic recycling. Overexpression of mutant motors revealed a selective role for Rab11 in coupling MYO5B to Kv1.5 recycling. CONCLUSIONS MYO5A and MYO5B control functionally distinct steps in the surface trafficking of Kv1.5. These isoform-specific trafficking pathways determine Kv1.5-encoded IKur in myocytes to regulate repolarizing current and, consequently, cardiac excitability. Therapeutic strategies that manipulate Kv1.5 selective trafficking pathways may prove useful in the treatment of arrhythmias.
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Affiliation(s)
- Sarah M Schumacher-Bass
- From the Department of Pharmacology, University of Michigan, Ann Arbor (S.M.S.-B., E.D.V., L.Z., K.E.R., D.P.M., C.R.F., J.C.M., J.R.M.); Cardiovascular Research Institute Robin Shaw, Department of Medicine, University of California, San Francisco (P.J.C.); and Cedars-Sinai Medical Center, Los Angeles, CA (R.M.S.)
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82
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Qiu XB, Xu YJ, Li RG, Xu L, Liu X, Fang WY, Yang YQ, Qu XK. PITX2C loss-of-function mutations responsible for idiopathic atrial fibrillation. Clinics (Sao Paulo) 2014; 69:15-22. [PMID: 24473555 PMCID: PMC3870307 DOI: 10.6061/clinics/2014(01)03] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2013] [Accepted: 07/10/2013] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVE This study aimed to identify novel PITX2c mutations responsible for idiopathic atrial fibrillation. METHODS A cohort of 210 unrelated patients with idiopathic atrial fibrillation and 200 unrelated, ethnically matched healthy individuals used as controls were recruited. The whole coding exons and splice junctions of the PITX2c gene, which encodes a paired-like homeobox transcription factor required for normal cardiovascular morphogenesis, were sequenced in 210 patients and 200 control subjects. The causative potentials of the identified mutations were automatically predicted by MutationTaster and PolyPhen-2. The functional characteristics of the PITX2c mutations were explored using a dual-luciferase reporter assay system. RESULTS Two novel heterozygous PITX2c mutations (p.Q105L and p.R122C) were identified in 2 of the 210 unrelated patients with idiopathic atrial fibrillation. These missense mutations were absent in the 400 control chromosomes and were both predicted to be pathogenic. Multiple alignments of PITX2c protein sequences across various species showed that the altered amino acids were highly evolutionarily conserved. A functional analysis demonstrated that the mutant PITX2c proteins were both associated with significantly reduced transcriptional activity compared with their wild-type counterparts. CONCLUSION The findings of this study associate PITX2c loss-of-function mutations with atrial fibrillation, supporting the hypothesis that dysfunctional PITX2c confers enhanced susceptibility to atrial fibrillation and suggesting potential implications for early prophylaxis and allele-specific therapy for this common arrhythmia.
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Affiliation(s)
- Xing-Biao Qiu
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, Shanghai Jiao Tong University, Shanghai Chest Hospital, Department of Cardiology and Cardiovascular Research, Shanghai, China
| | - Ying-Jia Xu
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, Shanghai Jiao Tong University, Shanghai Chest Hospital, Department of Cardiology and Cardiovascular Research, Shanghai, China
| | - Ruo-Gu Li
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, Shanghai Jiao Tong University, Shanghai Chest Hospital, Department of Cardiology and Cardiovascular Research, Shanghai, China
| | - Lei Xu
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, Shanghai Jiao Tong University, Shanghai Chest Hospital, Department of Cardiology and Cardiovascular Research, Shanghai, China
| | - Xu Liu
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, Shanghai Jiao Tong University, Shanghai Chest Hospital, Department of Cardiology and Cardiovascular Research, Shanghai, China
| | - Wei-Yi Fang
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, Shanghai Jiao Tong University, Shanghai Chest Hospital, Department of Cardiology and Cardiovascular Research, Shanghai, China
| | - Yi-Qing Yang
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, Shanghai Jiao Tong University, Shanghai Chest Hospital, Department of Cardiology and Cardiovascular Research, Shanghai, China
| | - Xin-Kai Qu
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, Shanghai Jiao Tong University, Shanghai Chest Hospital, Department of Cardiology and Cardiovascular Research, Shanghai, China
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83
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Yu H, Xu JH, Song HM, Zhao L, Xu WJ, Wang J, Li RG, Xu L, Jiang WF, Qiu XB, Jiang JQ, Qu XK, Liu X, Fang WY, Jiang JF, Yang YQ. Mutational spectrum of the NKX2-5 gene in patients with lone atrial fibrillation. Int J Med Sci 2014; 11:554-63. [PMID: 24782644 PMCID: PMC4003540 DOI: 10.7150/ijms.8407] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Accepted: 03/07/2014] [Indexed: 12/16/2022] Open
Abstract
Atrial fibrillation (AF) is the most common form of sustained cardiac arrhythmia in humans and is responsible for substantial morbidity and mortality worldwide. Emerging evidence indicates that abnormal cardiovascular development is involved in the pathogenesis of AF. In this study, the coding exons and splice sites of the NKX2-5 gene, which encodes a homeodomain-containing transcription factor essential for cardiovascular genesis, were sequenced in 146 unrelated patients with lone AF as well as the available relatives of the mutation carriers. A total of 700 unrelated ethnically matched healthy individuals used as controls were genotyped. The disease-causing potential of the identified NKX2-5 variations was predicted by MutationTaster and PolyPhen-2. The functional characteristics of the mutant NKX2-5 proteins were analyzed using a dual-luciferase reporter assay system. As a result, two heterozygous NKX2-5 mutations, including a previously reported p.E21Q and a novel p.T180A mutation, were identified in two families with AF transmitted in an autosomal dominant pattern. The mutations co-segregated with AF in the families with complete penetrance. The detected substitutions, which altered the amino acids highly conserved evolutionarily across species, were absent in 700 control individuals and were both predicted to be causative. Functional analyses demonstrated that the NKX2-5 mutants were associated with significantly decreased transcriptional activity compared with their wild-type counterpart. The findings expand the spectrum of NKX2-5 mutations linked to AF and provide additional evidence that dysfunctional NKX2-5 may confer vulnerability to AF, suggesting the potential benefit for the early prophylaxis and personalized treatment of AF.
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Affiliation(s)
- Hong Yu
- 1. Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, 389 Xincun Road, Shanghai 200065, China
| | - Jia-Hong Xu
- 1. Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, 389 Xincun Road, Shanghai 200065, China
| | - Hao-Ming Song
- 1. Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, 389 Xincun Road, Shanghai 200065, China
| | - Lan Zhao
- 2. Department of Cardiology, Yantaishan Hospital, 91 Jiefang Road, Yantai 264001, Shandong, China
| | - Wen-Jun Xu
- 1. Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, 389 Xincun Road, Shanghai 200065, China
| | - Juan Wang
- 1. Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, 389 Xincun Road, Shanghai 200065, China
| | - Ruo-Gu Li
- 3. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Lei Xu
- 3. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Wei-Feng Jiang
- 3. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Xing-Biao Qiu
- 3. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Jin-Qi Jiang
- 4. Department of Emergency, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Xin-Kai Qu
- 3. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Xu Liu
- 3. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Wei-Yi Fang
- 3. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
| | - Jin-Fa Jiang
- 1. Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, 389 Xincun Road, Shanghai 200065, China
| | - Yi-Qing Yang
- 3. Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China; ; 5. Department of Cardiovascular Research Laboratory, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China; ; 6. Department of Central Laboratory, Shanghai Chest Hospital, Shanghai Jiao Tong University, 241 West Huaihai Road, Shanghai 200030, China
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84
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Corradi D. Atrial fibrillation from the pathologist's perspective. Cardiovasc Pathol 2013; 23:71-84. [PMID: 24462196 DOI: 10.1016/j.carpath.2013.12.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 12/03/2013] [Accepted: 12/07/2013] [Indexed: 12/18/2022] Open
Abstract
Atrial fibrillation (AF), the most common sustained cardiac arrhythmia encountered in clinical practice, is associated with increased morbidity and mortality. Electrophysiologically, it is characterized by a high rate of asynchronous atrial cell depolarization causing a loss of atrial contractile function and irregular ventricular rates. For a long time, AF was considered as a pure functional disorder without any structural background. Only in recent years, have new mapping and imaging techniques identified atrial locations, which are very often involved in the initiation and maintenance of this supraventricular arrhythmia (i.e. the distal portion of the pulmonary veins and the surrounding atrial myocardium). Morphological analysis of these myocardial sites has demonstrated significant structural remodeling as well as paved the way for further knowledge of AF natural history, pathogenesis, and treatment. This architectural myocardial disarrangement is induced by the arrhythmia itself and the very frequently associated cardiovascular disorders. At the same time, the structural remodeling is also capable of sustaining AF, thereby creating a sort of pathogenetic vicious circle. This review focuses on current understanding about the structural and genetic bases of AF with reference to their classification, pathogenesis, and clinical implications.
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Affiliation(s)
- Domenico Corradi
- Department of Biomedical, Biotechnological, and Translational Sciences (S.Bi.Bi.T.), Unit of Pathology, University of Parma, Parma, Italy.
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85
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Lübkemeier I, Andrié R, Lickfett L, Bosen F, Stöckigt F, Dobrowolski R, Draffehn AM, Fregeac J, Schultze JL, Bukauskas FF, Schrickel JW, Willecke K. The Connexin40A96S mutation from a patient with atrial fibrillation causes decreased atrial conduction velocities and sustained episodes of induced atrial fibrillation in mice. J Mol Cell Cardiol 2013; 65:19-32. [PMID: 24060583 DOI: 10.1016/j.yjmcc.2013.09.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 09/11/2013] [Accepted: 09/13/2013] [Indexed: 12/22/2022]
Abstract
Atrial fibrillation (AF) is the most common type of cardiac arrhythmia and a major cause of stroke. In the mammalian heart the gap junction proteins connexin40 (Cx40) and connexin43 (Cx43) are strongly expressed in the atrial myocardium mediating effective propagation of electrical impulses. Different heterozygous mutations in the coding region for Cx40 were identified in patients with AF. We have generated transgenic Cx40A96S mice harboring one of these mutations, the loss-of-function Cx40A96S mutation, as a model for atrial fibrillation. Cx40A96S mice were characterized by immunochemical and electrophysiological analyses. Significantly reduced atrial conduction velocities and strongly prolonged episodes of atrial fibrillation were found after induction in Cx40A96S mice. Analyses of the gating properties of Cx40A96S channels in cultured HeLa cells also revealed significantly lower junctional conductance and enhanced sensitivity voltage gating of Cx40A96S in comparison to Cx40 wild-type gap junctions. This is caused by reduced open probabilities of Cx40A96S gap junction channels, while single channel conductance remained the same. Similar to the corresponding patient, heterozygous Cx40A96S mice revealed normal expression levels and localization of the Cx40 protein. We conclude that heterozygous Cx40A96S mice exhibit prolonged episodes of induced atrial fibrillation and severely reduced atrial conduction velocities similar to the corresponding human patient.
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Affiliation(s)
- Indra Lübkemeier
- Life and Medical Sciences (LIMES) Institute, Molecular Genetics, University of Bonn, Bonn, Germany
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86
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Zhou YM, Zheng PX, Yang YQ, Ge ZM, Kang WQ. A novel PITX2c loss‑of‑function mutation underlies lone atrial fibrillation. Int J Mol Med 2013; 32:827-34. [PMID: 23913021 DOI: 10.3892/ijmm.2013.1463] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2013] [Accepted: 07/29/2013] [Indexed: 11/05/2022] Open
Abstract
Atrial fibrillation (AF) is the most common form of sustained cardiac arrhythmia responsible for substantial morbidity and significantly increased mortality rates. A growing body of evidence documents the important role of genetic defects in the pathogenesis of AF. However, AF is a heterogeneous disease and the genetic determinants for AF in an overwhelming majority of patients remain unknown. In the present study, a cohort of 100 unrelated patients with lone AF and a total of 200 unrelated, ethnically matched healthy individuals used as controls, were recruited. The whole coding exons and splice junctions of the pituitary homeobox 2c (PITX2c) gene, which encodes a paired‑like homeobox transcription factor required for normal cardiovascular morphogenesis, were sequenced in the 100 patients and 200 control subjects. The causative potential of the identified mutation of PITX2c was predicted by MutationTaster and PolyPhen‑2. The functional characteristics of the PITX2c mutation were assayed using a dual‑luciferase reporter assay system. Based on the results, a novel heterozygous PITX2c mutation (p.T97A) was identified in a patient with AF. The missense mutation was absent in the 400 reference chromosomes and was automatically predicted to be disease‑causing. Multiple alignments of PITX2c protein sequences across species revealed that the altered amino acid was completely conserved evolutionarily. Functional analysis demonstrated that the mutant PITX2c protein was associated with significantly decreased transcriptional activity when compared with its wild‑type counterpart. The findings of the present study firstly link the PITX2c loss‑of‑function mutation to lone AF, and provide novel insight into the molecular mechanisms underlying AF, suggesting the potential implications for the early prophylaxis and allele‑specific therapy of this common type of arrhythmia.
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Affiliation(s)
- Yi-Meng Zhou
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Shandong University Qilu Hospital, Jinan, Shandong 250012, PR China
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87
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De Bock M, Kerrebrouck M, Wang N, Leybaert L. Neurological manifestations of oculodentodigital dysplasia: a Cx43 channelopathy of the central nervous system? Front Pharmacol 2013; 4:120. [PMID: 24133447 PMCID: PMC3783840 DOI: 10.3389/fphar.2013.00120] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 09/02/2013] [Indexed: 12/30/2022] Open
Abstract
The coordination of tissue function is mediated by gap junctions (GJs) that enable direct cell–cell transfer of metabolic and electric signals. GJs are formed by connexins of which Cx43 is most widespread in the human body. In the brain, Cx43 GJs are mostly found in astroglia where they coordinate the propagation of Ca2+ waves, spatial K+ buffering, and distribution of glucose. Beyond its role in direct intercellular communication, Cx43 also forms unapposed, non-junctional hemichannels in the plasma membrane of glial cells. These allow the passage of several neuro- and gliotransmitters that may, combined with downstream paracrine signaling, complement direct GJ communication among glial cells and sustain glial-neuronal signaling. Mutations in the GJA1 gene encoding Cx43 have been identified in a rare, mostly autosomal dominant syndrome called oculodentodigital dysplasia (ODDD). ODDD patients display a pleiotropic phenotype reflected by eye, hand, teeth, and foot abnormalities, as well as craniofacial and bone malformations. Remarkably, neurological symptoms such as dysarthria, neurogenic bladder (manifested as urinary incontinence), spasticity or muscle weakness, ataxia, and epilepsy are other prominent features observed in ODDD patients. Over 10 mutations detected in patients diagnosed with neurological disorders are associated with altered functionality of Cx43 GJs/hemichannels, but the link between ODDD-related abnormal channel activities and neurologic phenotype is still elusive. Here, we present an overview on the nature of the mutants conveying structural and functional changes of Cx43 channels and discuss available evidence for aberrant Cx43 GJ and hemichannel function. In a final step, we examine the possibilities of how channel dysfunction may lead to some of the neurological manifestations of ODDD.
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Affiliation(s)
- Marijke De Bock
- Physiology Group, Department of Basic Medical Sciences, Ghent University Ghent, Belgium
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88
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Jennings MM, Donahue JK. Connexin Remodeling Contributes to Atrial Fibrillation. J Atr Fibrillation 2013; 6:839. [PMID: 28496873 DOI: 10.4022/jafib.839] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 07/22/2013] [Accepted: 07/24/2013] [Indexed: 11/10/2022]
Abstract
Atrial fibrillation significantly contributes to mortality and morbidity through increased risk of stroke, heart failure and myocardial infarction. Investigations of mechanisms responsible for the development and maintenance of atrial fibrillation have highlighted the importance of gap junctional remodeling. Connexins 40 and 43, the major atrial gap junctional proteins, undergo considerable alterations in expression and localization in atrial fibrillation, creating an environment conducive to sustained reentry. Atrial fibrillation is initiated and/or maintained in this reentrant substrate. This review will focus on connexin remodeling in the context of underlying mechanism and possible therapeutic target for atrial fibrillation.
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Affiliation(s)
| | - J Kevin Donahue
- Case Western Reserve University School of Medicine, MetroHealth Campus
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89
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Woods JO, Singh-Blom UM, Laurent JM, McGary KL, Marcotte EM. Prediction of gene-phenotype associations in humans, mice, and plants using phenologs. BMC Bioinformatics 2013; 14:203. [PMID: 23800157 PMCID: PMC3704650 DOI: 10.1186/1471-2105-14-203] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 05/24/2013] [Indexed: 12/19/2022] Open
Abstract
Background Phenotypes and diseases may be related to seemingly dissimilar phenotypes in other species by means of the orthology of underlying genes. Such “orthologous phenotypes,” or “phenologs,” are examples of deep homology, and may be used to predict additional candidate disease genes. Results In this work, we develop an unsupervised algorithm for ranking phenolog-based candidate disease genes through the integration of predictions from the k nearest neighbor phenologs, comparing classifiers and weighting functions by cross-validation. We also improve upon the original method by extending the theory to paralogous phenotypes. Our algorithm makes use of additional phenotype data — from chicken, zebrafish, and E. coli, as well as new datasets for C. elegans — establishing that several types of annotations may be treated as phenotypes. We demonstrate the use of our algorithm to predict novel candidate genes for human atrial fibrillation (such as HRH2, ATP4A, ATP4B, and HOPX) and epilepsy (e.g., PAX6 and NKX2-1). We suggest gene candidates for pharmacologically-induced seizures in mouse, solely based on orthologous phenotypes from E. coli. We also explore the prediction of plant gene–phenotype associations, as for the Arabidopsis response to vernalization phenotype. Conclusions We are able to rank gene predictions for a significant portion of the diseases in the Online Mendelian Inheritance in Man database. Additionally, our method suggests candidate genes for mammalian seizures based only on bacterial phenotypes and gene orthology. We demonstrate that phenotype information may come from diverse sources, including drug sensitivities, gene ontology biological processes, and in situ hybridization annotations. Finally, we offer testable candidates for a variety of human diseases, plant traits, and other classes of phenotypes across a wide array of species.
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Affiliation(s)
- John O Woods
- Center for Systems & Synthetic Biology, Institute for Cellular & Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA
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90
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Minogue PJ, Beyer EC, Berthoud VM. A connexin50 mutant, CX50fs, that causes cataracts is unstable, but is rescued by a proteasomal inhibitor. J Biol Chem 2013; 288:20427-34. [PMID: 23720739 DOI: 10.1074/jbc.m113.452847] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The mechanisms by which mutant connexins lead to disease are diverse, including those of connexin50 (CX50) encoded by the GJA8 gene. We investigated the cellular and functional behavior of CX50fs, a mutant CX50 that has a frameshift after amino acid 255 and causes recessive congenital cataracts. Cellular levels of CX50fs were much lower than those of wild type CX50 in stably transfected HeLa cells. Whereas CX50 localized at distinct gap junction plaques and supported extensive intercellular transfer of Neurobiotin, CX50fs gap junctions were rare, and their support of Neurobiotin transfer was reduced by >90%. After inhibition of new protein synthesis with cycloheximide, CX50fs disappeared much more rapidly than CX50, suggesting increased degradation of the mutant. Treatment of cells with epoxomicin (a proteasomal inhibitor) led to a dramatic increase in CX50fs levels and in the abundance of gap junctions. Epoxomicin treatment also rescued intercellular transfer of Neurobiotin to levels similar to those in cells expressing the wild type protein. Treatment with eeyarestatin I (an inhibitor of p97-dependent protein degradation) resulted in many abundant slowly migrating CX50 and CX50fs bands consistent with polyubiquitination of the proteins. These results demonstrate that the CX50fs mutant is rapidly degraded by endoplasmic reticulum-associated degradation in mammalian cells. This accelerated degradation reduces the abundance of gap junctions and the extent of intercellular communication, potentially explaining the pathogenesis of cataracts linked to this mutant. The efficacy of epoxomicin in restoring function suggests that protease inhibition might have therapeutic value for this and other diseases caused by mutants with similar defects.
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Affiliation(s)
- Peter J Minogue
- Department of Pediatrics, University of Chicago, Chicago, Illinois 60637, USA
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91
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Liao HR, Poon KS, Chen KB. Atrial fibrillation: an anesthesiologist's perspective. ACTA ACUST UNITED AC 2013; 51:34-6. [PMID: 23711604 DOI: 10.1016/j.aat.2013.03.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 08/03/2012] [Accepted: 08/08/2012] [Indexed: 11/19/2022]
Abstract
Atrial fibrillation (AF) is not only the most common arrhythmia in the global population but also the most frequent one encountered in the operating room. For an anesthesiologist, it is crucial to have the ability to maintain hemodynamics and prevent complications of patients who present AF perioperatively. Here we provide a brief review in the novel concept of the classification, pathophysiology, and management of AF to provide a practical approach for physicians coming across this arrhythmia during the perioperative period.
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Affiliation(s)
- Hsiu-Rong Liao
- Department of Anesthesia, Pain Service and Critical Care Medicine, China Medical University Hospital, Taichung, Taiwan
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92
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Li RG, Wang Q, Xu YJ, Zhang M, Qu XK, Liu X, Fang WY, Yang YQ. Mutations of the SCN4B-encoded sodium channel β4 subunit in familial atrial fibrillation. Int J Mol Med 2013; 32:144-50. [PMID: 23604097 DOI: 10.3892/ijmm.2013.1355] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 04/12/2013] [Indexed: 01/08/2023] Open
Abstract
Atrial fibrillation (AF) represents the most common form of sustained cardiac arrhythmia and accounts for substantial morbidity and mortality. Mutations in the cardiac sodium channel α, β1, β2 and β3 subunit genes (SCN5A, SCN1B, SCN2B and SCN3B) have been associated with AF, which suggests that mutations in the sodium channel β4 subunit gene, SCN4B, are also involved in the pathogenesis of AF. To examine this hypothesis, the coding exons and exon-intron boundaries of SCN4B were sequenced in 170 unrelated index patients with familial AF. The available relatives of the probands carrying the identified mutations and 200 unrelated ethnically matched healthy individuals used as the controls were subsequently genotyped. The pathogenic potential of a SCN4B sequence variation was predicted using MutationTaster. As a result, 2 novel heterozygous SCN4B mutations, p.V162G and p.I166L, were identified in 2 unrelated families with AF transmitted in an autosomal dominant pattern, respectively. In each family the mutation co-segregated with AF and was absent in the 400 control chromosomes. The mutations altered the amino acids evolutionarily highly conserved across species and were both predicted to be disease-causing. To the best of our knowledge, this is the first study to demonstrate an association of SCN4B mutations with AF, suggesting SCN4B as a novel AF susceptibility gene.
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Affiliation(s)
- Ruo-Gu Li
- Department of Cardiology and Cardiovascular Research, Shanghai Chest Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200030, P.R. China
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93
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Sabina S, Pulignani S, Rizzo M, Cresci M, Vecoli C, Foffa I, Ait-Ali L, Pitto L, Andreassi MG. Germline hereditary, somatic mutations and microRNAs targeting-SNPs in congenital heart defects. J Mol Cell Cardiol 2013; 60:84-9. [PMID: 23583740 DOI: 10.1016/j.yjmcc.2013.04.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 03/22/2013] [Accepted: 04/04/2013] [Indexed: 12/21/2022]
Abstract
Somatic mutations and dysregulation by microRNAs (miRNAs) may have a pivotal role in the Congenital Heart Defects (CHDs). The purpose of the study was to assess both somatic and germline mutations in the GATA4 and NKX2.5 genes as well as to identify 3'UTR single nucleotide polymorphisms (SNPs) in the miRNA target sites. We enrolled 30 patients (13 males; 13.4±8.3 years) with non-syndromic CHD. GATA4 and NKX2.5 genes were screened in cardiac tissue of sporadic and in blood samples of familial cases. Computational methods were used to detect putative miRNAs in the 3'UTR region and to assess the Minimum Free Energy of hybridization (MFE, kcal/mol). Difference of MFEs (ΔMFE) ≥4 kcal/mol between alleles was considered biologically relevant on miRNA binding. The sum of all ΔMFEs (|ΔMFEtot|=∑|ΔMFE|) was calculated in order to predict the biological importance of SNPs binding more miRNAs. No evidence of novel GATA4 and NKX2.5 mutations was found both in sporadic and familial patients. Bioinformatic analysis revealed 27 putative miRNAs binding to identified SNPs in the 3'UTR of GATA4. ΔMFE ≥4 kcal/mol between alleles was obtained for the +354A>C (miR-4299), +587A>G (miR-604), +1355G>A (miR-548v, miR-139-5p) and +1521C>G (miR-583, miR-3125, miR-3928) SNPs. The +1521C>G SNP showed the highest ΔMFEtot (21.66 kcal/mol). Luciferase reporter assays indicated that miR-583 was dose-dependently effective in regulating +1521 C allele compared with +1521 G allele. Based on the analysis of 100 CHD cases and 204 healthy newborns, the +1521 G allele was also associated with a lower risk of CHD (OR=0.5, 95% CI 0.3-0.9, p=0.03), likely due to the relatively low binding of the miRNA and high levels of protein. These results suggest that common SNPs in the 3'UTR of GATA4 alter miRNA gene regulation contributing to the pathogenesis of CHDs.
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94
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Zhang SS, Shaw RM. Multilayered regulation of cardiac ion channels. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1833:876-85. [PMID: 23103513 PMCID: PMC3568256 DOI: 10.1016/j.bbamcr.2012.10.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 10/12/2012] [Accepted: 10/12/2012] [Indexed: 12/27/2022]
Abstract
Essential to beat-to-beat heart function is the ability for cardiomyocytes to propagate electrical excitation and generate contractile force. Both excitation and contractility depend on specific ventricular ion channels, which include the L-type calcium channel (LTCC) and the connexin 43 (Cx43) gap junction. Each of these two channels is localized to a distinct subdomain of the cardiomyocyte plasma membrane. In this review, we focus on regulatory mechanisms that govern the lifecycles of LTCC and Cx43, from their biogenesis in the nucleus to directed delivery to T-tubules and intercalated discs, respectively. We discuss recent findings on how alternative promoter usage, tissue-specific transcription, and alternative splicing determine precise ion channel expression levels within a cardiomyocyte. Moreover, recent work on microtubule and actin-dependent trafficking for Cx43 and LTCC are introduced. Lastly, we discuss how human cardiac disease phenotypes can be attributed to defects in distinct mechanisms of channel regulation at the level of gene expression and channel trafficking. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.
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Affiliation(s)
- Shan-Shan Zhang
- University of California, San Francisco, San Francisco, CA 94158, USA
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95
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A novel NKX2.5 loss-of-function mutation responsible for familial atrial fibrillation. Int J Mol Med 2013; 31:1119-26. [PMID: 23525379 DOI: 10.3892/ijmm.2013.1316] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 02/27/2013] [Indexed: 01/08/2023] Open
Abstract
Atrial fibrillation (AF) represents the most common form of sustained cardiac arrhythmia and accounts for substantial morbidity and mortality. Increasing evidence demonstrates that abnormal cardiovascular development is involved in the pathogenesis of AF. In this study, the coding exons and splice sites of the NKX2.5 gene, which encodes a homeodomain-containing transcription factor pivotal for normal cardiovascular morphogenesis, were sequenced in 110 unrelated index patients with familial AF. The available relatives of the mutation carrier and 200 unrelated ethnically-matched healthy individuals serving as controls were subsequently genotyped. The disease-causing potential of the identified NKX2.5 variation was predicted by MutationTaster. The functional characteristics of the mutant NKX2.5 protein were analyzed using a dual-luciferase reporter assay system. As a result, a novel heterozygous NKX2.5 mutation, p.F145S, was identified in a family with AF transmitted as an autosomal dominant trait, which co-segregated with AF in the family with complete penetrance. The detected substitution, which altered the amino acid completely conserved evolutionarily across species, was absent in 400 control chromosomes and was automatically predicted to be causative. Functional analysis demonstrated that the NKX2.5 mutant was associated with significantly decreased transcriptional activity compared with its wild-type counterpart. To the best of our knowledge, this is the first report on the association of the NKX2.5 loss-of-function mutation with increased susceptibility to familial AF. The findings of the present study provide novel insights into the molecular mechanism underlying AF, suggesting the potential implications for the early prophylaxis and allele-specific therapy of AF.
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96
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Kim E, Fishman GI. Designer gap junctions that prevent cardiac arrhythmias. Trends Cardiovasc Med 2012; 23:33-8. [PMID: 23245912 DOI: 10.1016/j.tcm.2012.08.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 08/01/2012] [Accepted: 08/02/2012] [Indexed: 12/28/2022]
Abstract
Cardiac gap junctions are specialized membrane structures comprised of arrays of intercellular channels responsible for propagation of the cardiac impulse. These channels are formed by oligomerization of individual protein subunits known as connexins. In response to a broad array of pathologic stressors, gap junction expression is disturbed, resulting in aberrant cardiac conduction and increased propensity for rhythm disturbances. In this article, we review some of the recently identified molecular regulators of connexin assembly, membrane targeting, and degradation, focusing on the role of post-translational phosphorylation of connexin 43, the major gap junctional protein expressed in ventricular myocardium. We also describe efforts to engineer "designer" gap junctions that are resistant to pathologic remodeling.
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Affiliation(s)
- Eugene Kim
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, NY 10016, USA
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97
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Wang XH, Huang CX, Wang Q, Li RG, Xu YJ, Liu X, Fang WY, Yang YQ. A novel GATA5 loss-of-function mutation underlies lone atrial fibrillation. Int J Mol Med 2012; 31:43-50. [PMID: 23175127 DOI: 10.3892/ijmm.2012.1189] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 08/16/2012] [Indexed: 11/06/2022] Open
Abstract
Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is associated with significantly increased morbidity and mortality. Cumulative evidence highlights the importance of genetic defects in the pathogenesis of AF. However, AF is of remarkable heterogeneity and the genetic determinants of AF in a vast majority of patients remain illusive. In this study, the coding exons and splice junctions of the GATA5 gene, which encodes a zinc-finger transcription factor essential for normal cardiogenesis, were sequenced in 118 unrelated patients with lone AF. The available relatives of the index patient carrying an identified mutation and 200 unrelated ethnically-matched healthy individuals used as controls were genotyped. The functional effect of the mutant GATA5 was characterized in contrast to its wild-type counterpart using a luciferase reporter assay system. As a result, a novel heterozygous GATA5 mutation, p.W200G, was identified in a family with AF inherited as an autosomal dominant trait. The mutation was absent in 200 control individuals and the altered amino acid was completely conserved evolutionarily across species. Functional analysis showed that the mutation of GATA5 was associated with a significantly decreased transcriptional activity. These findings provide novel insight into the molecular mechanism involved in AF, suggesting potential implications for the early prophylaxis and gene-specific therapy of AF.
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Affiliation(s)
- Xin-Hua Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, PR China
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98
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Riley G, Syeda F, Kirchhof P, Fabritz L. An introduction to murine models of atrial fibrillation. Front Physiol 2012; 3:296. [PMID: 22934047 PMCID: PMC3429067 DOI: 10.3389/fphys.2012.00296] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 07/08/2012] [Indexed: 01/28/2023] Open
Abstract
Understanding the mechanism of re-entrant arrhythmias in the past 30 years has allowed the development of almost curative therapies for many rhythm disturbances. The complex, polymorphic arrhythmias of atrial fibrillation (AF) and sudden death are, unfortunately, not yet well understood, and hence still in need of adequate therapy. AF contributes markedly to morbidity and mortality in aging Western populations. In the past decade, many genetically altered murine models have been described and characterized. Here, we review genetically altered murine models of AF; powerful tools that will enable a better understanding of the mechanisms of AF and the assessment of novel therapeutic interventions.
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Affiliation(s)
- Genna Riley
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham Birmingham, UK
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99
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Li J, Liu WD, Yang ZL, Yang YQ. Novel GATA6 loss-of-function mutation responsible for familial atrial fibrillation. Int J Mol Med 2012; 30:783-90. [PMID: 22824924 DOI: 10.3892/ijmm.2012.1068] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2012] [Accepted: 06/19/2012] [Indexed: 11/06/2022] Open
Abstract
Atrial fibrillation (AF) is the most commonly sustained cardiac arrhythmia, and confers a substantially increased risk of morbidity and mortality. Increasing evidence has indicated that hereditary defects are implicated in AF. However, AF is genetically heterogeneous and the genetic etiology of AF in a significant portion of patients remains unclear. In this study, the entire coding sequence and splice junctions of the GATA6 gene, which encodes a zinc-finger transcription factor crucial for cardiogenesis, were sequenced in 140 unrelated patients with lone AF. The available relatives of the index patient carrying an identified mutation and 200 unrelated ethnically-matched healthy individuals used as the controls were genotyped. The functional characteristics of the mutant GATA6 were assessed in contrast to its wild-type counterpart using a luciferase reporter assay system. As a result, a novel heterozygous GATA6 mutation, p.G469V, was identified in a family with AF inherited in an autosomal dominant pattern. The mutation was absent in the 200 control individuals and the altered amino acid was completely conserved across species. Functional analysis demonstrated that the GATA6 mutation was associated with a significantly decreased transcriptional activity. The findings provide novel insight into the molecular mechanism involved in the pathogenesis of AF, as well as insight into potential therapies for the prevention and treatment of AF.
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Affiliation(s)
- Jian Li
- Department of Emergency, Pu Nan Hospital, Shanghai 200125, PR China
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100
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Jones DL, Tuomi JM, Chidiac P. Role of Cholinergic Innervation and RGS2 in Atrial Arrhythmia. Front Physiol 2012; 3:239. [PMID: 22754542 PMCID: PMC3386567 DOI: 10.3389/fphys.2012.00239] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 06/12/2012] [Indexed: 01/25/2023] Open
Abstract
The heart receives sympathetic and parasympathetic efferent innervation as well as the ability to process information internally via an intrinsic cardiac autonomic nervous system (ICANS). For over a century, the role of the parasympathetics via vagal acetylcholine release was related to controlling primarily heart rate. Although in the late 1800s shown to play a role in atrial arrhythmia, the myocardium took precedence from the mid-1950s until in the last decade a resurgence of interest in the autonomics along with signaling cascades, regulators, and ion channels. Originally ignored as being benign and thus untreated, recent emphasis has focused on atrial arrhythmia as atrial fibrillation (AF) is the most common arrhythmia seen by the general practitioner. It is now recognized to have significant mortality and morbidity due to resultant stroke and heart failure. With the aging population, there will be an unprecedented increased burden on health care resources. Although it has been known for more than half a century that cholinergic stimulation can initiate AF, the classical concept focused on the M2 receptor and its signaling cascade including RGS4, as these had been shown to have predominant effects on nodal function (heart rate and conduction block) as well as contractility. However, recent evidence suggests that the M3 receptor may also playa role in initiation and perpetuation of AF and thus RGS2, a putative regulator of the M3 receptor, may be a target for therapeutic intervention. Mice lacking RGS2 (RGS2−/−), were found to have significantly altered electrophysiological atrial responses and were more susceptible to electrically induced AF. Vagally induced or programmed stimulation-induced AF could be blocked by the selective M3R antagonist, darifenacin. These results suggest a potential surgical target (ICANS) and pharmacological targets (M3R, RGS2) for the management of AF.
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Affiliation(s)
- Douglas L Jones
- Department of Physiology and Pharmacology, The University of Western Ontario London, ON, Canada
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