Arrhythmogenicity of human SAP97 Mutations in patient specific iPSC-CMs and Mice

 描述（申请人提供）：心脏离子通道基因突变可导致电节律紊乱，称为心律失常。这种遗传性节律紊乱被称为离子通道病，包括Brugada综合征（BrS）和长QT综合征（LQTS）等疾病。在某些情况下，约70%的通道病基因无法检测。“MAGUK”蛋白质在细胞膜下支撑离子通道，允许有效的电信号。MAGUK的异常表达可以改变离子通道功能，从而损害电激发。典型的MAGUK是突触相关蛋白97（SAP 97）。SAP 97基因在心脏中大量表达，有证据表明SAP 97与离子通道相互作用，因此可能调节兴奋。我们建立了一个独特的基因敲除小鼠模型（Sap 97-KO），以研究Sap 97在兴奋中的作用。Sap 97-KO小鼠心电图和细胞电生理特性异常。此外，最近的一项临床研究确定了与BrS相关的SAP 97突变，可能是关键钾通道表达异常增加的结果。我们假设SAP 97对心脏离子通道蛋白的组装很重要，并且SAP 97的异常表达会增加心律失常的易感性。我们将使用我们的小鼠模型以及患者特异性干细胞衍生的心肌细胞（iPSC-CM）来测试我们的假设。将讨论三个目标。1)目的研究Sap 97-KO小鼠心肌致瘤机制。2)研究Sap 97-KO小鼠细胞和BrS中SAP 97突变患者的干细胞衍生心肌细胞（iPSC-CM）中钾、钠和钙通道表达的Sap 97依赖性变化。3)研究单细胞以及iPSC-CM层中与人SAP 97突变相关的心律失常机制。我们提出的研究将深入了解与SAP 97表达异常相关的通道病的分子机制，并提供治疗干预的靶点。

 DESCRIPTION (provided by applicant): Mutations on cardiac ion channel genes can lead to electrical rhythm disturbances known as arrhythmias. Such inherited rhythm disturbances are termed ion channelopathies and include disorders such as Brugada Syndrome (BrS) and Long QT Syndrome (LQTS). In certain instances approximately 70% of channelopathy genes are elude detection. 'MAGUK' proteins scaffold ion channels underneath cell membranes, allowing for efficient electrical signaling. Abnormal expression of a MAGUK could alter ion channel function and thereby compromise electrical excitation. The prototypical MAGUK is the synapse-associated protein 97 (SAP97). SAP97 gene is abundantly expressed in the heart, and there is evidence that SAP97 interacts with ion channels and may therefore regulate excitation. We generated a unique mouse model with the gene knock out (Sap97-KO), to investigate the role of Sap97 in excitation. Sap97-KO mice have abnormalities in ECG and cell electrophysiological properties. Furthermore, a recent clinical study identified mutations in SAP97, which were associated with BrS, and probably the result of abnormally increased expression of a key potassium channel. It is our hypothesis that SAP97 is important for the assembly of cardiac ion channel proteins, and that abnormal SAP97 expression will increase arrhythmia susceptibility. We will test our hypothesis using our mouse model, as well as patient-specific stem cell-derived cardiac myocytes (iPSC-CMs). Three aims will be addressed. 1) To study arrhythmogenic mechanisms in the myocardium of Sap97-KO mice. 2) To investigate Sap97- dependent changes in the expression of potassium, sodium and calcium channels in Sap97-KO mouse cells, and in stem cell-derived cardiac myocytes (iPSC-CMs) of patients with SAP97 mutations in BrS. 3) To study arrhythmia mechanisms associated with human SAP97 mutations in single cells, as well as in layers of iPSC- CMs. Our proposed study will provide insight into molecular mechanisms of channelopathies associated with abnormal SAP97 expression, as well as provide targets for therapeutic intervention.