Cellular and electrophysiological characterization of triadin knockout syndrome using induced pluripotent stem cell-derived cardiomyocytes
Daniel J. Clemens, Dan Ye, Lili Wang, C.S. John Kim, Wei Zhou, Steven M. Dotzler, David J. Tester, Isabelle Marty, Björn C. Knollmann, Michael J. Ackerman
Abstract
Triadin knockout syndrome (TKOS) is a malignant arrhythmia disorder caused by recessive null variants in TRDN -encoded cardiac triadin. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were generated from two unrelated TKOS patients and an unrelated control. CRISPR-Cas9 gene editing was used to insert homozygous TRDN-p.D18fs ∗ 13 into a control line to generate a TKOS model (TRDN −/− ). Western blot confirmed total knockout of triadin in patient-specific and TRDN −/− iPSC-CMs. iPSC-CMs from both patients revealed a prolonged action potential duration (APD) at 90% repolarization, and this was normalized by protein replacement of triadin. APD prolongation was confirmed in TRDN −/− iPSC-CMs. TRDN −/− iPSC-CMs revealed that loss of triadin underlies decreased expression and co-localization of key calcium handling proteins, slow and decreased calcium release from the sarcoplasmic reticulum, and slow inactivation of the L-type calcium channel leading to frequent cellular arrhythmias, including early and delayed afterdepolarizations and APD alternans.