Abstract 17739: Modelling Long-QT Syndrome Associated With a Calmodulin Mutation Using Human Induced Pluripotent Stem Cells
Background: Calmodulin (CALM) is a ubiquitous Ca2+-sensor molecule, and it modulates various proteins including several ion channels, ryanodine receptor 2, and Ca2+/calmodulin-dependent protein kinase. Recently, several studies reported that CALM mutations are associated with severe early-onset long-QT syndrome (LQTS). However, the underlying mechanism remains unknown.
Purpose: The present study aims to establish the in-vitro disease model of CALM-related LQTS and elucidate the pathophysiological mechanism using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).
Methods: The hiPSC clones were generated from a 12-year-old boy with LQTS carrying a missense CALM2 mutation (c.293A>G, p.N98S), and differentiated into cardiomyocytes via embryoid body (EB) formation. The electrophysiological characteristics of CALM2-N98S hiPSC-CMs, including action potential (AP) and L-type Ca2+ channel (LTCC) currents, were analyzed by patch-clamp technique, and compared with those of hiPSC-CMs derived from healthy control.
Results: The beating rate of CALM2-N98S EBs was significantly lower than that of control (23.8 ± 1.6 bpm vs 47.3 ± 1.7 bpm, p < 0.01). The corrected AP duration at 90% repolarization (cAPD90) of CALM2-N98S hiPSC-CMs was significantly prolonged compared to that of control (480.9 ± 59.4 ms vs 201.5 ± 19.5 ms, p < 0.01, Figure). At 1 Hz pacing, CALM2-N98S hiPSC-CMs exhibited significantly longer APD90 than control (495.5 ± 47.7 ms vs 227.8 ± 21.6 ms, p < 0.01). The time constants of LTCC inactivation tau fast of CALM2-N98S hiPSC-CMs were significantly larger than those of control at 0, +10, and +20 mV test potentials (Figure).
Conclusion: The hiPSC-CMs model of CALM2-related LQTS successfully recapitulated the disease phenotypes, and elucidated the pathophysiological mechanism: impaired inactivation of LTCC currents. This model might be useful for drug discovery in CALM2-related LQTS.
Author Disclosures: Y. Yamamoto: None. T. Makiyama: None. T. Harita: None. K. Sasaki: None. M. Hayano: None. S. Nishiuchi: None. Y. Wuriyanghai: None. H. Kohjitani: None. S. Hirose: None. J. Chen: None. T. Ishikawa: None. S. Ohno: None. Y. Yoshida: None. M. Horie: None. N. Makita: None. T. Kimura: None.
- © 2015 by American Heart Association, Inc.