Identification and functional characterisation of a novel KCNJ2 mutation, Val302del, causing Andersen-Tawil syndrome.

Ördög, Balázs and Hategan, Lidia and Kovács, Mária and Seprényi, György and Kohajda, Zsófia and Nagy, István and Hegedűs, Zoltán and Jost, Norbert László and Jancsó Gáborné Katona, Márta and Szekeres, Miklós and Papp, Gyula and Varró, András and Sepp, Róbert and Forster, Tamás and Környei, László (2015) Identification and functional characterisation of a novel KCNJ2 mutation, Val302del, causing Andersen-Tawil syndrome. CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY, 93 (7). pp. 569-575. ISSN 0008-4212

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Abstract

Loss-of-function mutations of the KCNJ2 gene encoding for the inward rectifier potassium channel subunit Kir2.1 cause Andersen-Tawil Syndrome (ATS), a rare genetic disorder characterised by periodic paralysis, ventricular arrhythmias, and dysmorphic features. Clinical manifestations of the disease appear to vary greatly with the nature of mutation, therefore, functional characterisation of ATS-causing mutations is of clinical importance. In this study, we describe the identification and functional analysis of a novel KCNJ2 mutation, Val302del, identified in a patient with ATS. Heterologously expressed wild type (WT) and Val302del mutant alleles showed similar subcellular distribution of the Kir2.1 protein with high intensity labelling from the membrane region, demonstrating normal membrane trafficking of the Val302del Kir2.1 variant. Cells transfected with the WT allele displayed a robust current with strong inward rectification, while no current above background was detected in cells expressing the Val302del Kir2.1 subunit. Co-transfection of CHO cells with the WT and the Val302del Kir2.1 revealed a dose-dependent inhibitory effect of the Val302del Kir2.1 mutant subunit on WT Kir2.1 currents. These observations indicate that the WT and the Val302del mutant subunits co-assemble in the cell membrane and that the mutation affects potassium conductivity and (or) gating of the WT/Val302del heteromeric Kir2.1 channels.

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