Biophysical properties of 9 KCNQ1 mutations associated with long-QT syndrome.

Yang T, Chung SK, Zhang W, Mullins JG, McCulley CH, Crawford J, MacCormick J, Eddy CA, Shelling AN, French JK, Yang P, Skinner JR, Roden DM, Rees MI
Circ Arrhythm Electrophysiol. 2009 2 (4): 417-26

PMID: 19808498 · PMCID: PMC2748886 · DOI:10.1161/CIRCEP.109.850149

BACKGROUND - Inherited long-QT syndrome is characterized by prolonged QT interval on the ECG, syncope, and sudden death caused by ventricular arrhythmia. Causative mutations occur mostly in cardiac potassium and sodium channel subunit genes. Confidence in mutation pathogenicity is usually reached through family genotype-phenotype tracking, control population studies, molecular modeling, and phylogenetic alignments; however, biophysical testing offers a higher degree of validating evidence.

METHODS AND RESULTS - By using in vitro electrophysiological testing of transfected mutant and wild-type long-QT syndrome constructs into Chinese hamster ovary cells, we investigated the biophysical properties of 9 KCNQ1 missense mutations (A46T, T265I, F269S, A302V, G316E, F339S, R360G, H455Y, and S546L) identified in a New Zealand-based long-QT syndrome screening program. We demonstrate through electrophysiology and molecular modeling that 7 of the missense mutations have profound pathological dominant-negative loss-of-function properties, confirming their likely disease-causing nature. This supports the use of these mutations in diagnostic family screening. Two mutations (A46T, T265I) show suggestive evidence of pathogenicity within the experimental limits of biophysical testing, indicating that these variants are disease-causing via delayed- or fast-activation kinetics. Further investigation of the A46T family has revealed an inconsistent cosegregation of the variant with the clinical phenotype.

CONCLUSIONS - Electrophysiological characterization should be used to validate long-QT syndrome pathogenicity of novel missense channelopathies. When such results are inconclusive, great care should be taken with genetic counseling and screening of such families, and alternative disease-causing mechanisms should be considered.

MeSH Terms (24)

Adolescent Adult Animals Biophysics Child CHO Cells Cricetinae Cricetulus Death, Sudden, Cardiac Female Genotype Humans KCNQ1 Potassium Channel Long QT Syndrome Male Middle Aged Mutagenesis, Site-Directed Mutation, Missense Patch-Clamp Techniques Pedigree Phenotype Protein Structure, Tertiary Structure-Activity Relationship Transfection

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