Abstract 20475: Investigating Molecular Mechanisms of Type 2 Long QT Syndrome With iPSC-Derived Cardiomyocytes

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Patient-specific cardiomyocytes obtained from induced pluripotent stem cells (CM-iPSC) offer unprecedented mechanistic insights in the study of inherited cardiac diseases. The aim of this work was to model type 2 long QT syndrome (LQTS2) in CM-iPSC. Mononuclear peripheral blood cells obtained from two patients with a mutation in the voltage sensing region of KCNH2 (c.1600C>T) were isolated and enriched for erythroblasts. iPSC were generated and colonies were selected, expanded, karyotyped. iPSC were characterized by RT-PCR, immunofluorescence and spontaneous differentiation. Our results demonstrated an efficient enrichment of the erythroid population, with coexpression of CD36 and CD71 over 90%. iPSC emerged during days 15-20 and were selected manually for expansion. The selected cell lines expressed pluripotency markers and exhibited spontaneous differentiation. In addition, we inserted the same mutation in a normal iPSC line by CRISPR/Cas9 genome editing. Electrophysiology demonstrated that the action potential duration (APD) of cardiomyocytes differentiated from patient-derived LQTS2-iPSC as well as from CRISPR-LQTS2-iPSC was significantly longer than that of control iPSC. Moreover, triangulation of action potentials, implying a longer duration of phase 3, was also increase in cells carrying the mutation. Treatment with E4031 caused APD prolongation only in control iPSC, indicating that IKr channel does not contribute to repolarization mutated cardiomyocytes. Patch-clamp demonstrated a reduction of IKrcurrent and immunofluorescence for Kv11.1 indicated a perinuclear staining of this channel in LQTS2 cell lines. We generated cardiomyocytes that recapitulate LQTS2 phenotype and our findings reinforce the hypothesis that iPSC reprogramed from LQTS2 patients constitute a promising platform to describe pathophysiological mechanisms and drug sensitivity in LQTS2.

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