Identification and characterization of a novel genetic mutation with prolonged QT syndrome in an unexplained postoperative death
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The human ether-à-go-go-related gene (hERG) encodes the α-subunit of a cardiac potassium channel. Various mutations of hERG, including missense mutations, have been reported to cause long QT syndrome (LQTS) and severe arrhythmic disorders such as sudden cardiac death. We identified a novel hERG frameshift mutation (hERG(ΔAT)) in the S5-pore region from a LQTS patient who died suddenly and analyzed its genetic profile and the molecular and electrophysiological behaviors of the protein product to assess the pathogenicity of hERG(ΔAT).
Methods and results
We performed direct sequencing of hERG and evaluated its transcript level by using a whole blood sample from the patient. We performed immunoblotting, immunocytochemistry, and patch-clamp recordings of HEK-293 T cells transfected with hERG(ΔAT), wild-type hERG (hERG(WT)), or both. The patient demonstrated an AT deletion (c.1735_1736del) in hERG and a decrease in hERG mRNA transcripts. HEK-293 T cells showed lower production and cell surface expression of hERG(ΔAT) compared with hERG(WT) protein. In addition, the hERG(∆AT) protein failed to form functional channels, while the activation kinetics of functional channels, presumably consisting of hERG(WT) subunits, were unaffected.
The ΔAT mutation may decrease the number of functional hERG channels by impairing the posttranscriptional and posttranslational processing of the mutant product. This decrease may partly explain the cardiac symptoms of the patient who was heterozygous for hERG(ΔAT).
KeywordsM579fs + 75X frameshift mutation Human ether-à-go-go-related gene Long QT syndrome Patch-clamp Transmembrane pore domain Arrhythmia
We thank Drs. Kenshi Hayashi (Kanazawa University Graduate School of Medical Science, Kanazawa, Japan), Sabina Kupershmidt (Vanderbilt University School of Medicine, Nashville, USA), and Jun-ichi Miyazaki (Osaka University Medical School, Osaka, Japan) for providing plasmids. We also thank Prof. K. Fukurotani for the opportunity to perform this work. This work was supported in part by KAKENHI grants from MEXT, Japan, to T.T. (19045019, 20022025, 20500284, 21026011, and 23500384) and a KAKENHI grant from JSPS, Japan, to Y.H. (24590852).
Conflict of interest
The authors declare that they have no conflict of interest.
The experiments described in this manuscript conform to the Declaration of Helsinki, and the protocols of gene sampling and manipulation were approved by the University of Toyama’s committee on the usage of human genetic material (#24-1).
- 2.Splawski I, Timothy KW, Sharpe LM, Decher N, Kumar P, Bloise R, Napolitano C, Schwartz PJ, Joseph RM, Condouris K, Tager-Flusberg H, Priori SG, Sanguinetti MC, Keating MT (2004) Cav1.2 calcium channel dysfunction causes a multisystem disorder including arrhythmia and autism. Cell 119:19–31PubMedCrossRefGoogle Scholar
- 5.Yang Y, Yang Y, Liang B, Liu J, Li J, Grunnet M, Olesen SP, Rasmussen HB, Ellinor PT, Gao L, Lin X, Li L, Wang L, Xiao J, Liu Y, Liu Y, Zhang S, Liang D, Peng L, Jespersen T, Chen YH (2010) Identification of a Kir3.4 mutation in congenital long QT syndrome. Am J Hum Genet 86:872–880PubMedCentralPubMedCrossRefGoogle Scholar
- 8.Shimizu W, Moss AJ, Wilde AA, Towbin JA, Ackerman MJ, January CT, Tester DJ, Zareba W, Robinson JL, Qi M, Vincent GM, Kaufman ES, Hofman N, Noda T, Kamakura S, Miyamoto Y, Shah S, Amin V, Goldenberg I, Andrews ML, McNitt S (2009) Genotype–phenotype aspects of type 2 long QT syndrome. J Am Coll Cardiol 54:2052–2062PubMedCentralPubMedCrossRefGoogle Scholar
- 18.Kinoshita K, Yamaguchi Y, Nishide K, Kimoto K, Nonobe Y, Fujita A, Asano K, Tabata T, Mori H, Inoue H, Hata Y, Fukurotani K, Nishida N (2012) A novel missense mutation causing a G487R substitution in the S2–S3 loop of human ether-à-go-go-related gene channel. J Cardiovasc Electrophysiol 23:1246–1253PubMedCrossRefGoogle Scholar
- 20.Millat G, Chevalier P, Restier-Miron L, Da Costa A, Bouvagnet P, Kugener B, Fayol L, Gonzàlez Armengod C, Oddou B, Chanavat V, Froidefond E, Perraudin R, Rousson R, Rodriguez-Lafrasse C (2006) Spectrum of pathogenic mutations and associated polymorphisms in a cohort of 44 unrelated patients with long QT syndrome. Clin Genet 70:214–227PubMedCrossRefGoogle Scholar