Signaling by beta 1 integrins regulates ventricular wall morphogenesis and compaction

心血管疾病是发达国家发病率和死亡率的主要原因。这样的一个 疾病是左心室致密化不全(LVNC，OMIM604169)。据报道，LVNC的患病率在 从0.01%到0.3%，在心力衰竭患者中更高，据报道为3%到4%。遗传遗传 至少30%-50%的患者发生LVNC，导致LVNC的基因包括编码肉瘤或 细胞骨架蛋白和Notch信号通路基因。在LVNC中，小梁不能进行压实。 小梁是从心肌延伸到心腔的片状结构，其功能是 在冠脉循环系统尚未发育时增加表面积。缺乏骨小梁 会导致胚胎死亡，过度的小梁形成会导致人类的LVNC和心力衰竭。我们的研究 结果表明，心肌细胞的定向分裂和定向迁移在单个细胞内是可能的。 较厚的心肌通过形成多层心肌而促进骨小梁的形成。然后是心内膜 细胞(EndCs)侵袭多层心肌，并分配心肌细胞形成小梁 E9.5。许多收缩蛋白基因突变与LVNC相关，并已推测 心肌的收缩功能是心室紧凑所必需的；然而，没有遗传模型 来检验这一假说。这一领域的后续问题将是什么机制 调节骨小梁的形成、新生小梁形成和脑室紧实。我们的初步数据 表明早期Itgb1基因导致小梁形成、生长、Notch1缺陷 纤维连接蛋白(FN)的激活和沉积，以及后期缺失导致致密性和Notch1缺陷 激活。此外，ITGA5基因或Fn1基因的全球缺失会导致心血管缺陷 但早期致死性阻碍了对它们在小梁形态发生中的作用的研究。我们的 心脏特异的缺失 初步数据显示，心脏特异的ItGa6基因(编码整合素α6亚基或α6)， 在压实过程中特异性地在小梁区表达，降低心脏收缩功能。 因此，我们的中心假设是整合素α5β1和α6β1在心脏中具有不同的功能。 α5β1调节小梁的形成和生长，整合素α6β1调节脑室的形态发生 收缩和随后的紧致和Notch1的激活。检验这一假说有两个目的。 遗传工具，如小梁专化系和紧凑区专用系将被用来测试这些 假设。我们已经发展了一些独特的专业知识，例如单细胞谱系追踪分析来研究 小梁形成的机制；测量药物或药物处理的胚胎心脏收缩能力的回声 车辆；rAAV9系统，以挽救LVNC缺陷。研究的完成将确定α5β1轴是否 调节骨小梁的形成和α6β1调节体内的致密化 增强Notch1的收缩和激活可挽救LVNC心肌病。 删除

Cardiovascular diseases are the leading causes of morbidity and mortality in developed countries. One such disease is left ventricular noncompaction (LVNC, OMIM604169). The prevalence of LVNC reportedly ranged from 0.01% to 0.3%, and is higher in patients with heart failure, reportedly 3% to 4%. Genetic inheritance occurs in at least 30–50% of patients and genes that cause LVNC include the genes that encode sarcomeric or cytoskeletal proteins and Notch signaling pathway genes. In LVNC, trabeculae fail to undergo compaction. Trabeculae are sheet-like structures extending from the myocardium to the heart lumen that function to increase surface area when the coronary circulation system is not developed yet. A lack of trabeculation causes embryonic lethality, and excess trabeculation causes LVNC and heart failure in humans. Our studies demonstrated that the orientated cell division and directional migration of cardiomyocytes in the single-cell- thick myocardium contribute to trabecular initiation by forming a multiple-layer myocardium. Then endocardial cells (EndCs) invade the multiple layered myocardium and allocate cardiomyocytes to form trabeculae before E9.5. Many mutations of contractile protein genes correlate with LVNC, and it has been speculated that the contractile function of the myocardium is required for ventricular compaction; however, no genetic models have been made to test this hypothesis. The subsequent questions in this field will be what are the mechanisms that regulate the trabecular formation, de novo trabeculation, and ventricular compaction. Our preliminary data show that early the Itgb1 gene causes defects in trabecular formation, growth, Notch1 activation and deposition of Fibronectin (Fn), and late deletion causes defects in compaction and Notch1 activation. Furthermore, global deletion of the Itga5 gene or Fn1 gene causes defects in cardiovascular morphogenesis, but early lethality prevented the study of their functions in trabecular morphogenesis. Our heart-specific deletion of preliminary data show that heart-specific Itga6 gene (encoding integrin α6 subunit or α6), which is expressed specifically in the trabecular zone during compaction, reduces cardiac contractile function. Therefore, our central hypothesis is that integrin α5β1 and α6β1 have distinct functions in cardiac morphogenesis with α5β1 regulating trabecular formation and growth, and integrin α6β1 regulating ventricular contraction and the subsequent compaction and Notch1 activation. There are two aims to test the hypothesis. Genetic tools such as trabecular specific and compact zone specific Cre lines will be used to test these hypotheses. We have developed some unique expertise, e.g., single cell lineage tracing assay to study the mechanisms of trabeculation; ECHO to measure the contractility of embryonic hearts treated with drug or vehicle; rAAV9 system to rescue the LVNC defect. Completion of the studies will determine whether α5β1 axis regulates the trabecular formation and α6β1 regulates compaction in vivo and determine whether enhancement of contraction and activation of Notch1 can rescue the LVNC cardiomyopathy. deletion of the