title: Compound heterozygosity for mutations Asp611-->Tyr in KCNQ1 and Asp609-->Gly in KCNH2 associated with severe long QT syndrome.
abstract: LQTS (long QT syndrome) is an inherited cardiac disorder characterized by prolongation of QT interval, torsades de pointes and sudden death. We have identified two heterozygous missense mutations in the KCNQ1 and KCNH2 (also known as HERG) genes [Asp611-->Tyr (D611Y) in KCNQ1 and Asp609-->Gly (D609G) in KCNH2] in a 2-year-old boy with LQTS. The aim of the present study was to characterize the contributions of the mutations in the KCNQ1 and KCNH2 genes relative to the clinical manifestations and electrophysiological properties of LQTS. Six of 11 carriers of D611Y in KCNQ1 had long QT intervals. D609G in KCNH2 was detected only in the proband. Studies on the electrophysiological alterations due to the two missense mutations revealed that the D611Y mutation in KCNQ1 did not show a significant suppression of the currents compared with wild-type, but the time constants of current activation in the mutants were increased compared with that in the wild-type. In contrast, the D609G mutation in KCNH2 showed a dominant-negative suppression. Our results suggest that the mild phenotype produced by the D611Y mutation in KCNQ1 became more serious by addition of the D609G mutation in KCNH2 in the proband.
authors.affiliation: Molecular Genetics of Cardiovascular Disorders, Division of Cardiovascular Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8640, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Masami
authors.initials: M
authors.lastname: Shimizu
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Ino
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Terai
authors.forename: Kenshi
authors.initials: K
authors.lastname: Hayashi
authors.forename: Tomoya
authors.initials: T
authors.lastname: Kaneda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mabuchi
authors.forename: Ryo
authors.initials: R
authors.lastname: Sumita
authors.forename: Tohru
authors.initials: T
authors.lastname: Oshima
authors.forename: Naoto
authors.initials: N
authors.lastname: Hoshi
authors.forename: Haruhiro
authors.initials: H
authors.lastname: Higashida
mesh_terms: D000293:Adolescent; D000328:Adult; D002675:Child, Preschool; D000072237:ERG1 Potassium Channel; D004562:Electrocardiography; D051638:Ether-A-Go-Go Potassium Channels; D005260:Female; D015870:Gene Expression / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D007223:Infant; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D008133:Long QT Syndrome / Q000235:genetics* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense / Q000235:genetics*; D010375:Pedigree; D010641:Phenotype; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics*
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated