medRxiv : the preprint server for health sciences · 2025
Increased L-type calcium current causes action potential prolongation in Jervell and Lange-Nielsen syndrome and is a drug target.
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Wada Yuko, Blair Marcia A, Strickland Teresa L, Laudeman Julie A, Kim Kyungsoo, Harvey M Lorena, Solus Joseph F, Fountain Darlene F, Knollmann Bjorn C, Shoemaker M Benjamin, Kannankeril Prince J, Roden Dan M
Аннотация
BACKGROUND: KCNQ1 loss of function variants are thought to cause type 1 long QT syndrome by reducing I Ks. However, we have recently reported that pharmacologic block of I Ks in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) produced minimal increases in action potential duration at 90% repolarization (APD90), while genetic loss of KCNQ1 markedly prolonged APD90. We sought here to define mechanisms underlying APD prolongation by genetic loss of KCNQ1.
METHODS: We studied iPSC-CMs from population controls, an isogenic KCNQ1 knock out (KO) line created by a homozygous edit for the R518X loss of function variant, and 2 unrelated patients with the Jervell and Lange-Nielsen syndrome (JLN) due to compound heterozygosity for loss of function KCNQ1 variants.
RESULTS: In both JLN and the KCNQ1-KO lines, I Ks was absent, APD90 was markedly prolonged, and L-type Ca channel (LTCC) current (I Ca-L) was significantly increased, 2-3-fold, compared to the control cells with no change in kinetics or gating. RNA-sequencing identified 298 and 584 genes that were up- and down-regulated, respectively, by KCNQ1-KO compared to the isogenic control cells. Gene ontology analysis identified down-regulation of 6 Ca2+ channel negative regulatory genes (p=0.0002, FDR=0.02), and in knockdown experiments in wild-type iPSC-CMs, three of these, CBARP, FKBP1B, and RRAD, increased I Ca-L, and RRAD increased APD90. A therapeutic low concentration (1 μM) of the Ca channel antagonist diltiazem significantly shortened APD90 in the two JLN cell lines and in KCNQ1-KO cells. A single low dose of intravenous diltiazem in one of the JLN patients shortened QTc.
CONCLUSIONS: These data further support the concept that delayed repolarization in JLN cannot be explained solely by loss of I Ks. Our findings demonstrate that KCNQ1 mutations lead to down-regulation of Ca2+ channel inhibitory genes, with resultant increased I Ca-L that underlies delayed repolarization in JLN. We further propose that diltiazem can be repurposed for treatment of patients with JLN.
METHODS: We studied iPSC-CMs from population controls, an isogenic KCNQ1 knock out (KO) line created by a homozygous edit for the R518X loss of function variant, and 2 unrelated patients with the Jervell and Lange-Nielsen syndrome (JLN) due to compound heterozygosity for loss of function KCNQ1 variants.
RESULTS: In both JLN and the KCNQ1-KO lines, I Ks was absent, APD90 was markedly prolonged, and L-type Ca channel (LTCC) current (I Ca-L) was significantly increased, 2-3-fold, compared to the control cells with no change in kinetics or gating. RNA-sequencing identified 298 and 584 genes that were up- and down-regulated, respectively, by KCNQ1-KO compared to the isogenic control cells. Gene ontology analysis identified down-regulation of 6 Ca2+ channel negative regulatory genes (p=0.0002, FDR=0.02), and in knockdown experiments in wild-type iPSC-CMs, three of these, CBARP, FKBP1B, and RRAD, increased I Ca-L, and RRAD increased APD90. A therapeutic low concentration (1 μM) of the Ca channel antagonist diltiazem significantly shortened APD90 in the two JLN cell lines and in KCNQ1-KO cells. A single low dose of intravenous diltiazem in one of the JLN patients shortened QTc.
CONCLUSIONS: These data further support the concept that delayed repolarization in JLN cannot be explained solely by loss of I Ks. Our findings demonstrate that KCNQ1 mutations lead to down-regulation of Ca2+ channel inhibitory genes, with resultant increased I Ca-L that underlies delayed repolarization in JLN. We further propose that diltiazem can be repurposed for treatment of patients with JLN.