Overlap Arrhythmia Syndromes Resulting from Multiple Genetic Variations Studied in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Figures

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  Figure 1. Representative ECG of MMRL1215 illustrating Early Repolarization Syndrome phenotype. A slurring of the QRS complex is apparent in multiple leads (denoted by the arrows). In addition, a QTc = 326 ms was noted.

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  Figure 2. (A): Extracellular field potential (EFP) signals recorded in WT (left side) and MMRL1215 hiPSC-CMs (right side). Compared to WT hiPSC, myocytes derived from MMRL1215 showed a complete lack of a pseudo QRS complex, suggesting a major reduction in inward current(s). Panel (B): Action potential (AP) recordings obtained from WT and MMRL1215 monolayers. MMRL1215 hiPSC-CMs had a shorter action potential duration compared to WT.

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  Figure 3. Line scans recorded from WT and MMRL1215 hiPSC-CMs showing spontaneous Ca2+ transients. Fluorescence intensity was much lower in MMRL 1215, and in some myocytes the spontaneous activity was episodic in nature.

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  Figure 4. Representative traces showing ICa recorded from WT (n = 11) and MMRL1215 (n = 9) (A,B). Ca2+ currents were recorded during a 300 ms step depolarization from −40 to +50mV. (C) Current-voltage relationship for ICa.

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  Figure 5. Representative whole cell INa recordings from WT and MMRL1215 hiPSC-CMs (A,B). Current recordings were obtained at test potentials between −80 and 30 mV (protocol at top of figure). (C): I–V relation for WT (n = 18) and MMRL1215 (n = 25) myocytes. (D): Steady-state activation curves for WT and MMRL1215 myocytes. Data were normalized and plotted against their test potential. * Statistically significant from WT, p < 0.05.

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  Figure 6. Representative steady-state inactivation recordings from WT and MMRL1215 myocytes (A,B) in response to the voltage clamp protocol (top of the figure). The steady state-inactivation relation for hiPSC-CMs (C) yielded similar mid-inactivation potential for WT (n = 25) and MMRL1215 (n = 29) cells.

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  Figure 7. Representative recovery from inactivation traces recorded from WT and MMRL1215 myocytes (A,B). Recovery was measured using two identical voltage clamp steps to −20 mV from a holding potential of either −120 mV or −100 mV separated by selected time intervals. (C): Mean data showing recovery time-course of INa recorded at −120 mV for WT (n = 24) and MMRL1215 (n = 26). (D): Recovery time-course of INa recorded at −100 mV for WT (n = 16) and MMRL1215 (n = 19).

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  Figure 8. Expression profile of genes PKP2, ANK2 and SCN5A obtained using real-time PCR.