| 配分額 *注記 |
4,160千円 (直接経費: 3,200千円、間接経費: 960千円)
2022年度: 1,300千円 (直接経費: 1,000千円、間接経費: 300千円)
2021年度: 1,560千円 (直接経費: 1,200千円、間接経費: 360千円)
2020年度: 1,300千円 (直接経費: 1,000千円、間接経費: 300千円)
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| 研究開始時の研究の概要 |
KCNH2 gene is one of the major related genes of short QT syndrome. We found a novel KCNH2 gene variant, p. His70Tyr, in a new SQTS family. KCNH2-H70Y variant showed a “gain-of-function” effect by functional analysis. The functional change might be related with the channel cellular mechanism. Therefore, elucidating the molecular mechanism of KCNH2 variants using HL-1 cells or cardiomyocyte differentiated from human-induced pluripotent cells (hiPSC-CM), can help to explore the targets of potential drugs for short QT syndrome.
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| 研究実績の概要 |
In our short QT syndrome family, we identified double mutations in KCNH2 and SLC4A3 genes. However, the KCNH2-H70Y did not affect IKr channel kinetics, which play an important role in the cardiac action potential. Therefore, we aimed to elucidate the relationship between a SLC4A3 mutation and QTc interval. Because the SLC4A3 gene encodes AE3 protein, which worked as an Cl-/HCO3- exchanger for maintaining intracellular pH (pHi), we examine the pHi of SLC4A3-WT and mutant HEK293 stable cells. We found that mutant cells showed low ability for the H+-equivalent flux and slow exchange speed when extracellular solution changed between physiological salt solution and Cl- free solution. Therefore, the SLC4A3-mutation showed loss-of-function of the channel kinetics.
We also studied the AE3 protein expression of total cell lysate, mutant cells showed normal expression with WT cells. Then, we focus our study on the electrophysiological study to check whether the SLC4A3 mutant directly involved in the phase 3 and 4 of cardiac action potential. However, there is no significant difference on the IKs, IK1 and Ikr wild-type (WT) currents, recorded on SLC4A3 WT and mutant HEK293 stable cell lines. In the following, we transfected KCNH2-H70Y plasmid into cells stably expressing SLC4A3 mutant, the IKr channel deactivation time constants were prolonged compared to the WT cells.
In conclusion, under the abnormal pHi environment affected by SLC4A3 mutation, KCNH2-H70Y decelerate the IKr deactivation kinetics, which may shorten the cardiac action potential and lead to short QT syndrome.
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