title: Ca2+ signaling in human induced pluripotent stem cell-derived cardiomyocytes (iPS-CM) from normal and catecholaminergic polymorphic ventricular tachycardia (CPVT)-afflicted subjects.
abstract: Derivation of cardiomyocytes from induced pluripotent stem cells (iPS-CMs) allowed us to probe the Ca(2+)-signaling parameters of human iPS-CMs from healthy- and catecholaminergic polymorphic ventricular tachycardia (CPVT1)-afflicted individuals carrying a novel point mutation p.F2483I in ryanodine receptors (RyR2). iPS-CMs were dissociated on day 30-40 of differentiation and patch-clamped within 3-6 days. Calcium currents (ICa) averaged ∼8pA/pF in control and mutant iPS-CMs. ICa-induced Ca(2+)-transients in control and mutant cells had bell-shaped voltage-dependence similar to that of ICa, consistent with Ca(2+)-induced Ca(2+)-release (CICR) mechanism. The ratio of ICa-activated to caffeine-triggered Ca(2+)-transients was ∼0.3 in both cell types. Caffeine-induced Ca(2+)-transients generated significantly smaller Na(+)-Ca(2+) exchanger current (INCX) in mutant cells, reflecting their smaller Ca(2+)-stores. The gain of CICR was voltage-dependent as in adult cardiomyocytes. Adrenergic agonists enhanced ICa, but differentially altered the CICR gain, diastolic Ca(2+), and Ca(2+)-sparks in mutant cells. The mutant cells, when Ca(2+)-overloaded, showed longer and wandering Ca(2+)-sparks that activated adjoining release sites, had larger CICR gain at -30mV yet smaller Ca(2+)-stores. We conclude that control and mutant iPS-CMs express the adult cardiomyocyte Ca(2+)-signaling phenotype. RyR2 F2483I mutant myocytes have aberrant unitary Ca(2+)-signaling, smaller Ca(2+)-stores, higher CICR gains, and sensitized adrenergic regulation, consistent with functionally altered Ca(2+)-release profile of CPVT syndrome.
authors.affiliation: Cardiac Signaling Center of USC, MUSC, & Clemson University, Charleston, SC 29403, USA.
authors.forename: X-H
authors.initials: XH
authors.lastname: Zhang
authors.forename: S
authors.initials: S
authors.lastname: Haviland
authors.forename: H
authors.initials: H
authors.lastname: Wei
authors.forename: T
authors.initials: T
authors.lastname: Sarić
authors.forename: A
authors.initials: A
authors.lastname: Fatima
authors.forename: J
authors.initials: J
authors.lastname: Hescheler
authors.forename: L
authors.initials: L
authors.lastname: Cleemann
authors.forename: M
authors.initials: M
authors.lastname: Morad
mesh_terms: D000322:Adrenergic Agonists / Q000494:pharmacology; D000328:Adult; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002395:Catecholamines / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D018408:Patch-Clamp Techniques; D039904:Pluripotent Stem Cells / Q000378:metabolism* / Q000473:pathology; D017354:Point Mutation / Q000235:genetics; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism; D017180:Tachycardia, Ventricular / Q000378:metabolism* / Q000473:pathology
chemical_list: D000322:Adrenergic Agonists; D002395:Catecholamines; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D002118:Calcium
keywords: CICR gain; CPVT; Calcium signaling; Mutation in RyR2 gene; Pluripotent stem cells