title: Zebrafish embryos express an orthologue of HERG and are sensitive toward a range of QT-prolonging drugs inducing severe arrhythmia.
abstract: A wide range of drugs has been shown to prolong the QT interval of the electrocardiogram by blocking the pore-forming subunit of the rapidly activating delayed rectifier K+ channel, HERG (ether-à-go-go-related gene), sometimes leading to life-threatening arrhythmia. In this paper we describe cloning, sequence, and expression of the zebrafish orthologue of HERG, Zerg. Further, we studied effects of Zerg inhibition in zebrafish embryos caused by drugs or by an antisense approach. Zerg is expressed specifically in both heart chambers of zebrafish embryos, is composed of six transmembrane domains, and shows an especially high degree of amino acid conservation in the S6 and pore domain (99% identity). Several QT-prolonging drugs added to the bathing medium elicited bradycardia and arrhythmia in zebrafish embryos. The arrhythmia induced ranged from an atrioventricular 2:1 block, the ventricle beating half as often as the atrium, to more severe irregular arrhythmia with higher concentrations of the drugs. These effects were highly specific, reproducible, and rapid, e.g., 10 microM astemizole caused a 2:1 heartbeat within a minute after addition of the compound in all the embryos studied. Morpholino antisense oligonucleotides targeting Zerg were injected into zebrafish embryos and elicited similar dose-sensitive and specific arrhythmia as the QT-prolonging drugs, suggesting an evolutionarily conserved role for Erg in regulating heartbeat rate and rhythm. Further, we identified a mutation in the Per-Arnt-Sim domain of the Zerg channel in the breakdance mutant, also characterized by a 2:1 atrioventricular block. In conclusion, the zebrafish could be a tractable model organism for the study of Erg function and modulation but might also have a value in the field of cardiovascular pharmacology, e.g., as an early preclinical model for testing drugs under development for potential QT prolongation.
authors.affiliation: Exelixis Deutschland GmbH, Spemannstrasse 35, D-72076 Tübingen, Germany. U.Langeheinrich@exelixis-de.com
authors.forename: Ulrike
authors.initials: U
authors.lastname: Langheinrich
authors.forename: Gabriele
authors.initials: G
authors.lastname: Vacun
authors.forename: Thomas
authors.initials: T
authors.lastname: Wagner
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced; D001483:Base Sequence; D027682:Cation Transport Proteins; D003001:Cloning, Molecular; D064420:Drug-Related Side Effects and Adverse Reactions; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels; D006321:Heart / Q000187:drug effects* / Q000196:embryology; D006339:Heart Rate / Q000187:drug effects*; D008133:Long QT Syndrome / Q000139:chemically induced*; D023421:Models, Animal; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000096:biosynthesis*; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D015027:Zebrafish / Q000196:embryology* / Q000378:metabolism
chemical_list: D027682:Cation Transport Proteins; D051638:Ether-A-Go-Go Potassium Channels; C092509:KCNH6 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger