Reduced heterogeneous expression of Cx43 results in decreased Nav1.5 expression and reduced sodium current that accounts for arrhythmia vulnerability in conditional Cx43 knockout mice.
Publication year
2012Source
Heart Rhythm, 9, 4, (2012), pp. 600-607ISSN
Annotation
1 april 2012
Publication type
Article / Letter to editor

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Organization
Human Genetics
Journal title
Heart Rhythm
Volume
vol. 9
Issue
iss. 4
Page start
p. 600
Page end
p. 607
Subject
IGMD 3: Genomic disorders and inherited multi-system disordersAbstract
BACKGROUND: Reduced expression of connexin43 (Cx43) and sodium channel (Nav1.5) and increased expression of collagen (fibrosis) are important determinants of impulse conduction in the heart. OBJECTIVE: To study the importance and interaction of these factors at very low Cx43 expression, inducible Cx43 knockout mice with and without inducible ventricular tachycardia (VT) were compared through electrophysiology and immunohistochemistry. METHODS: Cx43(CreER(T)/fl) mice were induced with tamoxifen and killed after 2 weeks. Epicardial activation mapping was performed on Langendorff-perfused hearts, and arrhythmia vulnerability was tested. Mice were divided into arrhythmogenic (VT+; n = 13) and nonarrhythmogenic (VT-; n = 10) animals, and heart tissue was analyzed for Cx43, Nav1.5, and fibrosis. RESULTS: VT+ mice had decreased Cx43 expression with increased global, but not local, heterogeneity of Cx43 than did VT- mice. Nav1.5-immunoreactive protein expression was lower in VT+ than in VT- mice, specifically at sites devoid of Cx43. Levels of fibrosis were similar between VT- and VT+ mice. QRS duration was increased and epicardial activation was more dispersed in VT+ mice than in VT- mice. The effective refractory period was similar between the 2 groups. Premature stimulation resulted in a more severe conduction slowing in VT+ than in VT- hearts in the right ventricle. Separate patch-clamp experiments in isolated rat ventricular myocytes confirmed that the loss of Cx43 expression correlated with the decreased sodium current amplitude. CONCLUSIONS: Global heterogeneity in Cx43 expression and concomitant heterogeneous downregulation of sodium-channel protein expression and sodium current leads to slowed and dispersed conduction, which sensitizes the heart for ventricular arrhythmias.
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- Academic publications [203686]
- Faculty of Medical Sciences [80280]
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