title: Dominant negative consequences of a hERG 1b-specific mutation associated with intrauterine fetal death.
abstract: The human ether-a-go-go related gene (hERG) encodes two subunits, hERG 1a and hERG 1b, that combine in vivo to conduct the rapid delayed rectifier potassium current (IKr). Reduced IKr slows cardiac action potential (AP) repolarization and is an underlying cause of cardiac arrhythmias associated with long QT syndrome (LQTS). Although the physiological importance of hERG 1b has been elucidated, the effects of hERG 1b disease mutations on cardiac IKr and AP behavior have not been described. To explore the disease mechanism of a 1b-specific mutation associated with a case of intrauterine fetal death, we examined the effects of the 1b-R25W mutation on total protein, trafficking and membrane current levels in HEK293 cells at physiological temperatures. By all measures the 1b-R25W mutation conferred diminished expression, and exerted a temperature-sensitive, dominant-negative effect over the WT hERG 1a protein with which it was co-expressed. Membrane currents were reduced by 60% with no apparent effect on voltage dependence or deactivation kinetics. The dominant-negative effects of R25W were demonstrated in iPSC-CMs, where 1b-R25W transfection diminished native IKr compared to controls. R25W also slowed AP repolarization, and increased AP triangulation and variability in iPSC-CMs, reflecting cellular manifestations of pro-arrhythmia. These data demonstrate that R25W is a dominant-negative mutation with significant pathophysiological consequences, and provide the first direct link between hERG 1b mutation and cardiomyocyte dysfunction.
authors.affiliation: Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA.
authors.forename: David K
authors.initials: DK
authors.lastname: Jones
authors.affiliation: Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.affiliation: Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA.
authors.forename: Natasha
authors.initials: N
authors.lastname: Dombrowski
authors.affiliation: Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA.
authors.forename: Sunita
authors.initials: S
authors.lastname: Joshi
authors.affiliation: Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA. Electronic address: garobert@wisc.edu.
authors.forename: Gail A
authors.initials: GA
authors.lastname: Robertson
mesh_terms: D000200:Action Potentials / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005313:Fetal Death; D057809:HEK293 Cells; D006321:Heart / Q000503:physiopathology; D006801:Humans; D009154:Mutation; D011188:Potassium / Q000378:metabolism; D055550:Protein Stability; D013696:Temperature
chemical_list: D051638:Ether-A-Go-Go Potassium Channels; C496884:KCNH1 protein, human; D011188:Potassium
keywords: Arrhythmia; Cardiomyocyte; KCNH2; Long QT syndrome; hERG