Functional analysis of novel KCNQ2 mutations found in patients with Benign Familial Neonatal Convulsions

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• 作者：Linda Volkers ; Martin B. Rook ; Joost H.G. Das ; Nienke E. Verbeek ; W. Antoinette Groenewegen ; Marjan J.A. van Kempen ; Dick Lindhout ; Bobby P.C. Koeleman
• 关键词：Benign Familial Neonatal Convulsions ; BFNC ; KCNQ2 ; Kv7.2 ; Loss-of-function
• 刊名：Neuroscience Letters
• 出版年：2009
• 出版时间：18 September 2009
• 年：2009
• 卷：462
• 期：1
• 页码：24-29
• 全文大小：2142 K

文摘

Benign Familial Neonatal Convulsions (BFNC) are a rare epilepsy disorder with an autosomal-dominant inheritance. It is linked to mutations in the potassium channel genes KCNQ2 and KCNQ3. These encode for Kv7.2 and Kv7.3 potassium ion channels, which produce an M-current that regulates the potential firing action in neurons through modulation of the membrane potential. We report on the biophysical and biochemical properties of V589X, T359K and P410fs12X mutant-KCNQ2 ion channels that were detected in three BFNC families. Mutant KCNQ2 cDNAs were co-expressed with WT-KCNQ2 and KCNQ3 cDNAs in HEK293 cells to mimic heterozygous expression of the KCNQ2 mutations in BFNC patients. The resulting potassium currents were measured using patch-clamp techniques and showed an approximately 75 % reduction in current and a depolarized shift in the voltage dependence of activation. Furthermore, the time-constant of activation of M-currents in cells expressing T359K and P410fs12X was slower compared to cells expressing only wild-type proteins. Immunofluorescent labeling of HEK293 cells stably expressing GFP-tagged KCNQ2-WT or mutant α-subunits indicated cell surface expression of WT, V589X and T359K mutants, suggesting a loss-of-function, while P410fs12X was predominantly retained in the ER and sub-cellular compartments outside the ER suggesting an effectively haplo-insufficient effect.