Pathogenic mechanism and gene correction for LQTS-causing double mutations in KCNQ1 using a pluripotent stem cell model

Abstract Aims To establish a KCNQ1 mutant-specific induced pluripotent stem cell (iPSC) model of a Chinese inherited long QT syndrome (LQTS) patient and to explore the pathogenesis of KCNQ1 mutations. Methods and results (1) Two patient-specific iPSC lines from the proband were obtained. (2) The experiments produced spontaneously beating cardiomyocytes (CMs) from patient iPSCs. Splicing mutation c. 605-2A > G in iPSC-derived cardiomyocytes (iPSC-CMs) resulted in the skipping of exon 4, exons 3-4, or exons 3-6 in KCNQ1 transcription what was observed in the patient's peripheral leukocytes. (3) Action potential duration (APD) at 50% and 90% repolarization (APD50 and APD90) of the patient's iPSC-derived ventricular-like-CMs was significantly longer than that of the control. Moreover, early after depolarization (EAD) and coupled beats were observed only in L1-iPSC-CMs. (4) A c.815G > A corrected iPSC line was obtained by using the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR associated protein 9 (Cas9) system. Conclusion (1) Cardiomyocytes with spontaneous pulsation were successfully differentiated from LQTS patient-specific iPSC lines. (2) For KCNQ1 splicing mutations, there is a chance that splicing patterns in peripheral leukocytes are similar to that in patient iPSC-CMs. (3) The truncated KCNQ1 proteins induced by such splicing mutation might cause Iks decrease, which in turn produced APD prolongation and triggered activities. (4) Our data showed that CRISPR-Cas9 system could be used to rescue the LQTS-related mutations.