{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"medRxiv"}],"indexed":{"date-parts":[[2026,1,16]],"date-time":"2026-01-16T13:07:57Z","timestamp":1768568877281,"version":"3.49.0"},"posted":{"date-parts":[[2025,3,21]]},"group-title":"Cardiovascular Medicine","reference-count":53,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2025,3,21]],"date-time":"2025-03-21T00:00:00Z","timestamp":1742515200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2025,3,21]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:sec>\n                  <jats:title>Background<\/jats:title>\n                  <jats:p>\n                    <jats:italic>KCNQ1<\/jats:italic>\n                    loss of function variants are thought to cause type 1 long QT syndrome by reducing\n                    <jats:italic>I<\/jats:italic>\n                    <jats:sub>Ks<\/jats:sub>\n                    . However, we have recently reported that pharmacologic block of\n                    <jats:italic>I<\/jats:italic>\n                    <jats:sub>Ks<\/jats:sub>\n                    in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) produced minimal increases in action potential duration at 90% repolarization (APD\n                    <jats:sub>90<\/jats:sub>\n                    ), while genetic loss of\n                    <jats:italic>KCNQ1<\/jats:italic>\n                    markedly prolonged APD\n                    <jats:sub>90<\/jats:sub>\n                    . We sought here to define mechanisms underlying APD prolongation by genetic loss of\n                    <jats:italic>KCNQ1<\/jats:italic>\n                    .\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>\n                    We studied iPSC-CMs from population controls, an isogenic\n                    <jats:italic>KCNQ1<\/jats:italic>\n                    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\n                    <jats:italic>KCNQ1<\/jats:italic>\n                    variants.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>\n                    In both JLN and the KCNQ1-KO lines,\n                    <jats:italic>I<\/jats:italic>\n                    <jats:sub>Ks<\/jats:sub>\n                    was absent, APD\n                    <jats:sub>90<\/jats:sub>\n                    was markedly prolonged, and L-type Ca channel (LTCC) current (\n                    <jats:italic>I<\/jats:italic>\n                    <jats:sub>Ca-L<\/jats:sub>\n                    ) 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\u2013 and down-regulated, respectively, by KCNQ1-KO compared to the isogenic control cells. Gene ontology analysis identified down-regulation of 6 Ca\n                    <jats:sup>2+<\/jats:sup>\n                    channel negative regulatory genes (p=0.0002, FDR=0.02), and in knockdown experiments in wild-type iPSC-CMs, three of these,\n                    <jats:italic>CBARP<\/jats:italic>\n                    ,\n                    <jats:italic>FKBP1B<\/jats:italic>\n                    , and\n                    <jats:italic>RRAD<\/jats:italic>\n                    , increased\n                    <jats:italic>I<\/jats:italic>\n                    <jats:sub>Ca-L<\/jats:sub>\n                    , and\n                    <jats:italic>RRAD<\/jats:italic>\n                    increased APD\n                    <jats:sub>90<\/jats:sub>\n                    . A therapeutic low concentration (1 \u03bcM) of the Ca channel antagonist diltiazem significantly shortened APD\n                    <jats:sub>90<\/jats:sub>\n                    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.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Conclusions<\/jats:title>\n                  <jats:p>\n                    These data further support the concept that delayed repolarization in JLN cannot be explained solely by loss of\n                    <jats:italic>I<\/jats:italic>\n                    <jats:sub>Ks<\/jats:sub>\n                    . Our findings demonstrate that\n                    <jats:italic>KCNQ1<\/jats:italic>\n                    mutations lead to down-regulation of Ca\n                    <jats:sup>2+<\/jats:sup>\n                    channel inhibitory genes, with resultant increased\n                    <jats:italic>I<\/jats:italic>\n                    <jats:sub>Ca-L<\/jats:sub>\n                    that underlies delayed repolarization in JLN. We further propose that diltiazem can be repurposed for treatment of patients with JLN.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.1101\/2025.03.20.25324224","type":"posted-content","created":{"date-parts":[[2025,3,21]],"date-time":"2025-03-21T23:22:56Z","timestamp":1742599376000},"source":"Crossref","is-referenced-by-count":0,"title":["Increased L-type calcium current causes action potential prolongation in Jervell and Lange-Nielsen syndrome and is a drug target"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8533-8040","authenticated-orcid":false,"given":"Yuko","family":"Wada","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marcia A.","family":"Blair","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Teresa L.","family":"Strickland","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Julie A.","family":"Laudeman","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2869-0659","authenticated-orcid":false,"given":"Kyungsoo","family":"Kim","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"M. 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