Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, 48149 Münster, Germany.
Center for Physiology and Pathophysiology, Institute for Neurophysiology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany.
Int J Mol Sci. 2023 Oct 18;24(20):15290. doi: 10.3390/ijms242015290.
Mutations in the gene, encoding one of the major subunits of cardiac G-protein-gated inwardly rectifying K (GIRK) channels, have been recently linked to inherited forms of sinus node dysfunction. Here, the pathogenic mechanism of the W101C mutation underlying sinus bradycardia in a patient-derived cellular disease model of sinus node dysfunction (SND) was investigated. A human-induced pluripotent stem cell (hiPSCs) line of a mutation carrier was generated, and CRISPR/Cas9-based gene targeting was used to correct the familial mutation as a control line. Both cell lines were further differentiated into cardiomyocytes (hiPSC-CMs) that robustly expressed GIRK channels which underly the acetylcholine-regulated K current (I). hiPSC-CMs with the W101C mutation (hiPSC-CM) had a constitutively active I under baseline conditions; the application of carbachol was able to increase I, further indicating that not all available cardiac GIRK channels were open at baseline. Additionally, hiPSC-CM had a more negative maximal diastolic potential (MDP) and a slower pacing frequency confirming the bradycardic phenotype. Of note, the blockade of the constitutively active GIRK channel with XAF-1407 rescued the phenotype. These results provide further mechanistic insights and may pave the way for the treatment of SND patients with GIRK channel dysfunction.
基因中的突变，该基因编码心脏 G 蛋白门控内向整流钾 (GIRK) 通道的主要亚基之一，最近与窦房结功能障碍的遗传形式有关。在这里，研究了导致窦房结心动过缓的 W101C 突变在窦房结功能障碍 (SND) 患者来源细胞疾病模型中的致病机制。生成了突变携带者的人诱导多能干细胞 (hiPSC) 系，并使用基于 CRISPR/Cas9 的基因靶向技术对家族突变进行校正作为对照系。这两种细胞系都进一步分化为心肌细胞 (hiPSC-CMs)，它们强烈表达构成乙酰胆碱调节的 K 电流 (I) 的 GIRK 通道。具有 W101C 突变的 hiPSC-CMs (hiPSC-CM) 在基线条件下具有持续激活的 I；应用卡巴胆碱能够增加 I，进一步表明并非所有可用的心脏 GIRK 通道在基线时都处于开放状态。此外，hiPSC-CM 的最大舒张电位 (MDP) 更负，起搏频率更慢，这证实了心动过缓的表型。值得注意的是，用 XAF-1407 阻断持续激活的 GIRK 通道可挽救表型。这些结果提供了进一步的机制见解，并可能为治疗 GIRK 通道功能障碍的 SND 患者铺平道路。
