Transcriptional regulation of cardiac conduction system morphogenesis

项目总结/摘要 电脉冲的传播，协调有节奏和同步的心脏收缩， 促进体循环是由专门的结构和细胞类型（心脏传导）调节的 系统（CCS）和工作心肌细胞在时空上精确的方式。先天性心脏病 CCS和CCS稳态的失调可导致CCS功能障碍，引起危及生命的疾病， 心律失常和增加儿童和成人的死亡风险。全基因组关联研究 在患有各种心律失常的人类患者中，GWAS显示了异常 心电图与许多离子通道、间隙连接蛋白、肌肉结构蛋白以及一些关键的 在心脏发育和特化、分化和稳态中起作用的转录因子 CCS的维持，其中包括碱性螺旋环抑制因子（bHLH）转录因子Hand1 和T-box转录因子Tbx20。Hand1在早期发育的心脏中表达， 心脏形态发生。Tbx20被证明与多种心源性事件和心脏事件密切相关。 功能有趣的是，尽管Hand1和Tbx20以前没有与CCS开发中的角色相关联， 或功能，GWAS分析揭示了HAND1和TBX20内的单核苷酸多态性（SNP 与QRS持续时间延长相关，具有强烈的连锁不平衡。适用于HAND1和TBX20 这些SNP是基因间的，提示在这些基因的转录调节中的作用。我确已 鉴定了一种左心室（LV）Hand1增强子，其具有GATA 4和T-box结合位点，位于 保守的非编码序列（CNS）位于报告的SNP之间。突变小鼠 携带这种增强子的基因编辑缺失导致QRS延长。支持这一发现，我们有 最近观察到Hand1在出生后心脏的CCS结构内特异性表达。 Tbx20的转录调控在多种心脏细胞谱系中表达。心肌获得或丧失 功能研究显示QRS持续时间改变和严重心律失常。总的来说，我们最重要的 假设Hand1和Tbx20协调并维持心脏空间和时间控制 通过平行或单一基因调控途径，传导系统发育和功能。我们将 我们用以下具体目的来检验这一假设：1）检验Hand 1的成人表达 在CCS内需要保持正常的QRS持续时间; 2）检验Tbx 20 在CCS的发展和体内平衡以及维持传导性 3）测试Hand1和Tbx20是否作为心肌细胞的关键转录调节因子， CCS的发育和CCS生理功能在共同或不同的调控途径。

PROJECT SUMMARY/ABSTRACT The propagation of electrical impulses that coordinate the rhythmic and synchronized cardiac contractions to facilitate systemic circulation is regulated by a specialized structures and cell types, the cardiac conduction system (CCS), and working cardiomyocytes in a spatial-temporally precise manner. Congenital defects of the CCS and dysregulation of CCS homeostasis can lead to CCS dysfunction, causing life threatening arrhythmias and increasing the risk of death in both children and adults. Genome Wide Association studies (GWAS) in human patients with various arrhythmias have revealed a close association between abnormal ECG and many ion channels, gap junction proteins, muscle structural proteins as well as a number of critical transcription factors that function in cardiac development and the specification, differentiation and homeostatic maintenance of the CCS, among them include the basic Helix-loop-Helix (bHLH) transcription factor Hand1 and the T-box transcription factor Tbx20. Hand1 is expressed in the early developing hearts and is essential for cardiac morphogenesis. Tbx20 is shown to be critically involved in multiple cardiogenic events and cardiac function. Interestingly, despite Hand1 and Tbx20 are not previously associated with roles in CCS development or function, GWAS analysis revealed single nucleotide polymorphisms (SNPs) within both HAND1 and TBX20 associated with prolonged QRS duration with strong linkage disequilibrium. For both HAND1 and TBX20 these SNPs are intergenic suggesting roles in transcriptional regulation of these genes. Indeed, we have identified a left ventricle (LV) Hand1 enhancer with GATA4 and T-box binding sites that resides within a conserved non-coding sequence (CNS) that lies in between the reported SNPs. Mutant mice that have harbored a gene-edited deletion of this enhancer result in a prolonged QRS. Supporting this finding, we have recently observed that Hand1 is specifically expressed within CCS structures in postnatal hearts. Transcriptional regulation of Tbx20 is expressed in multiple cardiac cell lineages. Myocardial gain- or loss-of- function studies have shown altered QRS duration and severe arrhythmia. Collectively, our overriding hypothesis is that Hand1 and Tbx20 coordinate and maintain the spatial and temporal control of the cardiac conductive system development and function via either parallel or single gene regulatory pathways. We will test this hypothesis with the following specific Aims: 1) to test the hypothesis that adult expression of Hand1 within the CCS is required for maintaining a normal QRS duration; 2) to test the hypothesis that Tbx20 functions in the development and homeostasis of the CCS as well as the maintenance of the conductive function of cardiomyocytes; 3) to test whether Hand1 and Tbx20 serves as key transcriptional regulators for CCS development and CCS physiological function in a common or different regulatory pathways.