Basic/Translational Science -> Genomics: Translational D-AB03 - Inherited arrhythmic disorders: new approaches for understanding of mechanisms and experimental therapies (ID 5) Abstract

D-AB03-05 - Inhibition Of Late Sodium Current Attenuates Prolonged Action Potential Durations In CACNA1C-E1115K IPS Cell Model With Disrupted Cav1.2 Ion Selectivity (ID 728)

Abstract

Background: A unique missense mutation, CACNA1C-E1115K, which impairs the calcium ion selectivity of L-type calcium channel, was reported to cause arrhythmogenic phenotypes. The therapeutic approach for this mutation is challenging.
Objective: The aim was to unveil a novel drug therapy for CACNA1C-E1115K using iPSC-based disease model.
Methods: We created iPSCs from a 12-year-old boy carrying heterozygous CACNA1C-E1115K, whose ECG presented QT prolongation, drug-induced Brugada pattern, and bradycardia. As controls, we used iPSCs from a healthy subject and isogenic iPSC lines created by using CRISPR-Cas9 and single-stranded oligonucleotide donors. Using differentiated cardiomyocytes, we investigated the reaction to anti-arrhythmic drugs in optical recordings with voltage-sensitive dye.
Results: In electrophysiological assay, E1115K iPS-CMs exhibited reduced peak ICaL densities and impaired calcium ion selectivity. In fluorescent images, E1115K iPS-CMs showed longer AP durations (APD), and more frequent APD alternans (Fig. A, B). As late sodium current (INaL) has been reported to contribute to brady-dependent QT prolongation (Heart Rhythm. 2011 May;8(5):762-9.), we focused on INaL blockade. Notably, mexiletine (10μM) and GS-458967 (500 nM), which inhibit INaL current, shortened APD specifically in E1115K iPS-CMs. Mexiletine also suppressed APD alternans (Fig C, D). These results suggested that INaL might have a crucial role in APD prolongation in mutant iPS-CMs, which was recapitulated by computer simulation model.
Conclusion: Inhibition of INaL was effective in APD shortening in E1115K iPS-CMs, and might be a pharmacological treatment option of this mutation.
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