Role of TET dioxygenase associated immune mechanisms in cardiac injury and repair

项目总结/摘要 不确定潜能的克隆性造血（Clonal hematopoiesis of indeterminate potential，CHIP）是指在造血干细胞中， 在没有血液系统疾病的个体中进行血细胞克隆。最近确定的外显子组测序 具有表观遗传调节因子（例如，的 DNA甲基胞嘧啶双加氧酶TET 2），其在老化期间表现出具有克隆扩增的生长优势。 有趣的是，具有体细胞TET 2突变的CHIP个体倾向于具有高的冠状动脉心血管疾病风险。 疾病（CVD）。这一发现预示着一个分子时代的到来，在解剖新的致病性 CHIP-CVD会聚的潜在机制。在模拟克隆造血的动物研究中，Tet 2 LOF 会加速动脉粥样硬化和心力衰竭虽然这些研究提供了详细的 表型特征，潜在的分子机制和TET 2之间的因果关系 CHIP中的LOF和CVD风险增加在很大程度上仍未得到解决。PI的实验室开发了一套 独特的工具，以解决这一关键的临床相关的知识差距，包括（i）组织特异性Tet 2缺陷 小鼠模型（在髓系或HSPC中特异性消除Tet 2）， 心脏损伤期间体内实时谱系追踪;和（ii）基于dCas 9的表观基因组编辑工具，其允许 对表观基因型和表型之间因果关系的探讨。该小组建议测试 Tet 2控制增强子活性的假设，该增强子调节了表达所需的关键基因， 维持单核细胞/巨噬细胞在对缺血性损伤的修复反应中的适当功能（例如， 心肌梗塞或MI）。目标1将解决Tet 2缺失如何损害活跃的骨髓细胞和HSPC 参与心肌梗死后心脏修复过程。目标2将解决Tet 2缺陷如何破坏增强子 关键基因的活性，这些基因对促炎性单核细胞向修复性单核细胞的转化至关重要， 干扰单核细胞的双相MI后反应以损害炎症的及时消退， 心脏修复将进一步测试恢复Tet 2/5 hmC功能的想法以干预MI后组织修复。 本研究通过关注心血管疾病与心血管疾病之间的相互作用， 心血管系统和免疫造血系统。该项目的完成预计将产生 体细胞TET 2突变相关的克隆造血如何增加 心血管疾病（CVD）和损害心脏功能的压力。更有临床意义的发现 本研究中所做的研究也有望建立靶向表观遗传缺陷的临床前理论基础。 预防和治疗CVD的调节剂。

Project Summary/ Abstract Clonal hematopoiesis of indeterminate potential (CHIP) is defined as an expansion of somatic hematopoietic blood cell clone in individual without hematological disorders. Recent exome sequencing identified hematopoietic stem and progenitor cells (HSPCs) with frequent mutations of epigenetic regulators (e.g., the DNA methylcytosine dioxygenase TET2) that exhibited growth advantage with clonal expansion during aging. Interestingly, CHIP individuals with somatic TET2 mutations tend to have high risk of coronary cardiovascular diseases (CVD). This discovery heralds the advent of a molecular era in the dissection of novel pathogenic mechanisms underlying CHIP-CVD convergence. In animal studies that mimic clonal hematopoiesis, Tet2 LOF has been found to accelerate atherosclerosis and heart failure. While these studies provided detailed phenotypic characterizations, the underlying molecular mechanisms and the causal relations between TET2 LOF in CHIP and increased CVD risk remain largely unresolved. The PI’s laboratory has developed a set of unique tools to address this critical clinically-relevant knowledge gap, including (i) tissue specific Tet2-deficient mouse models (specific ablation of Tet2 in the myeloid lineage or in HSPCs) with reporter genes to enable real-time lineage tracing in vivo during cardiac injury; and (ii) dCas9 based epigenome editing tools that allow the interrogation of causal effects between epigenotypes and phenotypes. The team proposes to test the hypothesis that Tet2 controls the activity of enhancers that regulate the expression of key genes required for maintaining the proper function of monocytes/ macrophages in the reparative response to ischemic injury (e.g., myocardial infarction or MI). Aim 1 will address how Tet2 loss impairs myeloid cells and HSPCs that actively participate in the post-MI cardiac repair process. Aim 2 will address how Tet2 deficiency disrupts enhancer activities in key genes that are essential for proinflammatory to reparative monocyte conversion, thereby perturbing the biphasic post-MI response of monocyte to compromise timely resolution of inflammation and cardiac repair. The idea of restoring Tet2/5hmC function will be further tested to intervene post-MI tissue repair. This study introduces a new dimension to dissect CVD pathogenesis by focusing on the interplay between the cardiovascular system and the immune-hematopoietic system. Completion of this project is anticipated to yield novel insights on how somatic TET2 mutations-associated clonal hematopoiesis increases the risk of cardiovascular disease (CVD) and impairs cardiac function under stress. More clinically relevant, discoveries made in this study are also expected to establish the preclinical rationale for targeting defective epigenetic regulators to prevent and treat CVD.