Recessive cardiac phenotypes in induced pluripotent stem cell models of Jervell and Lange-Nielsen syndrome: Disease mechanisms and pharmacological rescue

Significance There are few laboratory models that recapitulate human cardiac disease. Here, we created human cell models for Jervell and Lange-Nielsen syndrome (JLNS) in vitro, based on human induced pluripotent stem cells (hiPSCs). JLNS is one of the most severe disorders of heart rhythm and can cause sudden death in young patients. JLNS is inherited recessively and is caused by homozygous mutations in the slow component of the delayed rectifier potassium current, IKs. Cardiomyocytes (CMs) from two independent sets of patient-derived and engineered hiPSCs showed electrophysiological defects that reflect the severity of the condition in patients. Our work allowed better understanding of the mechanisms of recessive inheritance. Furthermore, JLNS-CMs showed increased sensitivity to proarrhythmic drugs, which could be rescued pharmacologically, demonstrating the potential of hiPSC-CMs in drug testing. Jervell and Lange-Nielsen syndrome (JLNS) is one of the most severe life-threatening cardiac arrhythmias. Patients display delayed cardiac repolarization, associated high risk of sudden death due to ventricular tachycardia, and congenital bilateral deafness. In contrast to the autosomal dominant forms of long QT syndrome, JLNS is a recessive trait, resulting from homozygous (or compound heterozygous) mutations in KCNQ1 or KCNE1. These genes encode the α and β subunits, respectively, of the ion channel conducting the slow component of the delayed rectifier K+ current, IKs. We used complementary approaches, reprogramming patient cells and genetic engineering, to generate human induced pluripotent stem cell (hiPSC) models of JLNS, covering splice site (c.478-2A>T) and missense (c.1781G>A) mutations, the two major classes of JLNS-causing defects in KCNQ1. Electrophysiological comparison of hiPSC-derived cardiomyocytes (CMs) from homozygous JLNS, heterozygous, and wild-type lines recapitulated the typical and severe features of JLNS, including pronounced action and field potential prolongation and severe reduction or absence of IKs. We show that this phenotype had distinct underlying molecular mechanisms in the two sets of cell lines: the previously unidentified c.478-2A>T mutation was amorphic and gave rise to a strictly recessive phenotype in JLNS-CMs, whereas the missense c.1781G>A lesion caused a gene dosage-dependent channel reduction at the cell membrane. Moreover, adrenergic stimulation caused action potential prolongation specifically in JLNS-CMs. Furthermore, sensitivity to proarrhythmic drugs was strongly enhanced in JLNS-CMs but could be pharmacologically corrected. Our data provide mechanistic insight into distinct classes of JLNS-causing mutations and demonstrate the potential of hiPSC-CMs in drug evaluation.