A Novel CALM1 Gene Mutation N98I Causing Long QT Syndrome and Ventricular Fibrillation

Abstract

Background: The CALM genes' mutations have been reported to be causative for multiple kinds of arrhythmias.

Objectives: We report here a novel heterozygous CALM1 mutation (c.296A>T; p.N98I) causing arrhythmic phenotype of long QT syndrome (LQTS) and ventricular fibrillation (VF) in a 4 year old Chinese girl and thus aim to elucidate its underlying mechanisms.

Methods: The recombinant proteins of CaM1-WT, CaM1-N98I and CaM1-N98S were expressed, purified and used in patch clamp experiments to detect the in vitro effects on the electrophysiology in mouse ventricular cardiomyocytes (VMCs). Then, C57BL/6J mice injected of Adeno-associated virus9 (AAV9), which mediates overexpression of CaM1-WT or CaM1-N98I, were used to detect the in vivo effects on the surface Electrocardiogram (ECG) and optical voltage mapping.

Results: CaM1-N98I significantly prolonged the action potential duration (APD) and increased the incidence of delayed afterdepolarization (DAD) and DAD-triggered AP in VMCs. CaM1-N98I also magnificently delayed the Ca2+/CaM-dependent inactivation (CDI) of L-type Ca2+ channel (LTCC, ICaL) and slightly increased NaV1.5 late current. Mice overexpressing CaM1-N98I had prolonged QT intervals, 100% incidence of premature ventricular beats (PVC) at resting state, 85.7% incidence of isoproterenol (ISO)-induced VF, and significantly slowed cardiac conduction velocity.

Conclusion: Our clinical data, together with in vitro and in vivo results, identify that the novel mutation CaM1-N98I is pathogenic for LQTS/VF.

Note:
Funding Information: This work was supported by the Natural Science Foundation of China (NSFC) Grant No. 91949128 (to Q-S. W.), No. 81873485 (to Q-S. W.), No.81974041 (to Y-P. W.), and No.82270447 (to Y-P. W.).

Declaration of Interests: The authors declare no conflict of interest.

Ethics Approval Statement: This study was approved by the Ethics Committee of Xinhua Hospital at SJTUSM. All mouse experiments were conducted in compliance with both the Guide for the Animal Care and Use Committee of Xinhua Hospital and the NIH Guide for the Care and Use of Laboratory Animals. The case study was approved by the Ethics Committee of Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine approval number: Approval No, XHEC-F-2023-051. Parental consent was obtained for this study.

Keywords: Mutation, Calmodulin; Long QT syndrome (LQTS), Ventricular Fibrillation (VF), L-type Ca2+ channels (LTCC), Action Potential Duration (APD)