Cellular and Molecular Mechanisms of Left Ventricular Growth and Morphogenesis

项目概要/摘要 先天性心脏病（CHD）是最常见的出生缺陷。在各种CHD中，单心室 由心室形态发生改变引起的表型具有最差的临床预后，包括 三尖瓣闭锁 (OMIM# 605067)、肺动脉闭锁 (OMIM# 265150) 和左心发育不全综合征 （HLHS；OMIM# 241550、614435）。单心室心脏呈现串联回路，使得全身 静脉回流至右心室和肺动脉，与来自肺静脉的血流相结合 返回左心室并排出体外与生存不相容。目前，有一个贫困 了解导致多种形式单一疾病的分子机制和细胞病因学 心室冠心病。 在 HLHS 中观察到人类心脏转录因子基因 NKX2.5 和 HAND1 突变 患者。由于当前的系统性和 鉴于广泛的表达域，Nkx2.5 和 Hand1 的条件敲除会导致胚胎致死 可用的 Cre 线路。由于缺乏受限的左心室 Cre 驱动器，禁止进行此类检查。手1是 在左心室的初级心野心肌内表达。我们已经分离出增强子 调节 Hand1 左心室表达并用其生成新型左心室特异性 Cre 驱动程序 通过它可以探究驱动左心室形态发生的细胞和分子机制 意识到了。我们的实验计划是从正在发育的左心室细胞中去除 Hand1 左心室谱系细胞。 胚胎心脏，有条件地删除左心室心肌内的 Nkx2.5，并验证 鉴定出从 24 名无关患者身上分离出的 HAND1 人类突变是 HLHS 的病因。这个 研究 Hand1 谱系心肌在心脏发生过程中的作用将有助于阐明细胞病因学 单心室表型和控制心室成熟的分子程序，因此 扩大对心室形态发生与人类疾病相关的理解。 相关性： 导致单心室表型的冠心病临床结果最差。从而，获得了 了解导致单心室心脏病的病因和分子机制 每年有可能使数千名儿科患者受益。 Hand1谱系在 单心室表型的起源并深入了解其细胞和分子机制 未充分研究的心肌人群将对开发冠心病非手术治疗方法有很大好处 患者。

PROJECT SUMMARY/ABSTRACT Congenital heart disease (CHD) is the most common birth defect. Among various CHDs, single ventricle phenotypes resulting from altered ventricular morphogenesis have the poorest clinical prognoses and include Tricuspid Atresia (OMIM# 605067), Pulmonary Atresia (OMIM# 265150), and Hypoplastic Left Heart Syndrome (HLHS; OMIM# 241550, 614435). The single ventricle heart presents with a series circuit such that systemic venous return to the right ventricle and pulmonary arteries combined with the flow from the pulmonary venous return into the left ventricle and out to the body is incompatible with survival. Currently, there is a poor understanding of the molecular mechanisms and cellular etiology causative of the many forms of single ventricle CHD. Human mutations in the cardiac transcription factor genes NKX2.5 and HAND1 have been observed in HLHS patients. Modeling and thus the study of possible HLHS phenotypes have been limited as current systemic and conditional knockouts of Nkx2.5 and Hand1 results in embryonic lethality given the broad expression domains of available Cre lines. The lack of a restricted left ventricle Cre driver prohibits such investigations. Hand1 is expressed within the primary heart field myocardium of the left ventricle. We have isolated the enhancer that regulates Hand1 left ventricular expression and used it to generate a novel left ventricular-specific Cre driver with which interrogation of the cellular and molecular mechanism driving left ventricular morphogenesis can be realized. Our experimental plan is to ablate the Hand1 left ventricular lineage cells from the developing embryonic heart, conditionally delete Nkx2.5 specifically within the left ventricular myocardium, and validate an identified human mutation in HAND1 isolated from 24 unrelated patients as being causative of HLHS. This study of the role that Hand1-lineage myocardium plays during cardiogenesis will shed light on the cell etiology of single ventricle phenotypes and on the molecular programs controlling ventricular maturation, thus expanding the understanding of ventricular morphogenesis as it relates to human disease. Relevance: CHDs resulting in single ventricle phenotypes have the poorest clinical outcomes. Thus, gaining an understanding of the etiology and molecular mechanisms that cause CHDs resulting in a single ventricle heart has the potential to benefit thousands of pediatric patients annually. The Hand1-lineage plays a key role in the genesis of single ventricle phenotypes and gaining insight into the cellular and molecular mechanism of this understudied myocardial population will have a great benefit to developing non-surgical treatments for CHD patients.