Shox2-Hand2调控染色质可接近性在窦房结形态发生中的表观遗传学机制研究

病态窦房结综合征（SSS）是一种常见的心脏疾病，其病理机制仍未完全阐明。我们发现Shox2基因敲除抑制窦房结起搏细胞标记物Hcn4的表达，引起P波消失、心动过缓及P-R间期延长等SSS表型；Shox2与组蛋白H3.3修饰的染色质结合，其缺失降低整体染色质可接近性、抑制Hand2的转录活性，导致起搏细胞转分化为工作心肌细胞和小鼠窦房结发育不全。我们推测Shox2与H3.3修饰的染色质结合，增加局部染色质可接近性，促进Hcn4等窦房结关键基因的表达从而维持窦房结的形态发生。本项目拟利用Shox2、Hand2基因敲除小鼠模型，运用激光显微切割、ATAC-seq及染色质构象捕获（3C）等技术深入揭示Shox2-Hand2在窦房结形态发生和功能维持中的作用；阐明Shox2-Hand2调控窦房结发生的染色质重塑机制，为以Shox2-Hand2信号轴为靶点开发表观遗传小分子药物治疗SSS提供理论依据。

Sick sinus syndrome (SSS) is one of the most common heart diseases, and its pathological mechanism has not yet been fully elucidated. We found that conditional knockout of Shox2 gene inhibited the expression of Hcn4, a pacemaker-cell marker in the Sinoatrial node (SAN) and led to SSS phenotypes such as disappearance of P waves, bradycardia, and prolonged PR intervals. We further revealed that Shox2 could bind to Histone H3.3, and the deletion of Shox2 reduced the transcriptional activity of Hand2 and overall chromatin accessibility, leading to the transdifferentiation of pacemaker cells into working cardiomyocytes and the hypoplasia of the SAN. We hypothesize that Shox2-Hand2 combines with H3.3 modified chromatin to increase partial chromatin accessibility, to promote the expression of key SAN genes such as Hcn4, and maintains the morphogenesis and function of the SAN. We intend to utilize knockout mouse models of Shox2 and Hand2 genes and use techniques such as laser capture, ATAC-seq, and chromatin conformation capture (3C) techniques; to reveal the chromatin remodeling mechanism of Shox2-Hand2 signal axis and elucidate their roles in the morphogenesis and function maintenance of the SAN. These result would provide a theoretical basis for developing epigenetic small molecule drugs to treat SSS with the Shox2-Hand2 signal axis as the target.