Molecular mechanisms regulating mouse valvulogenesis

描述（由申请人提供）：先天性心脏病（CHDs）是最常见的出生缺陷形式，发生在多达1-5%的新生儿中，并且仍然是发达国家婴儿发病率和死亡率的主要非传染性原因。瓣膜畸形占冠心病的30%。尽管几十年的研究，潜在的先天性瓣膜疾病的机制仍然在很大程度上难以捉摸。MicroRNAs （miRNAs）已成为各种心血管疾病的有希望的治疗靶点/药物。虽然mirna在调节心肌发生中的关键作用已经得到了很好的确立，但它们在瓣膜发生中的活动，特别是在哺乳动物中，几乎没有研究过。我们目前对miRNA在瓣膜发育中的作用的了解仅限于几篇使用斑马鱼作为主要模型系统的出版物。关于mirna在哺乳动物瓣膜发生中的作用的知识的缺乏，对开发mirna治疗瓣膜疾病的诊断/治疗应用构成了主要障碍。为了直接测试mirna是否对哺乳动物瓣膜发育至关重要，我们建立了小鼠模型，其中Dicer1在胚胎心内膜细胞中特异性失活，心内膜细胞是瓣膜小叶细胞的前体。我们的研究首次揭示了心内膜细胞中的miRNA调节机制是支持新生小鼠正常瓣膜形成所需的。我们提出了一个中心假设，即mirna是哺乳动物正常瓣膜发生的分子调控网络的重要组成部分。我们将通过以下两个具体目标来检验这一假设。在Aim 1中，我们将确定在小鼠心内膜细胞中全面阻断miRNA生物合成对瓣膜形成的影响。在Aim 2中，我们将测试mirna介导的Ptpn11抑制在预防瓣膜增生中的作用。mirna在许多生物/病理过程中发挥重要作用，但其在哺乳动物瓣膜发生中的功能尚未被研究。完成这些研究将极大地促进我们对调节哺乳动物瓣膜发生的复杂分子/遗传机制的基本理解，并为mirna在先天性瓣膜疾病的临床应用提供重要线索。

DESCRIPTION (provided by applicant): Congenital heart diseases (CHDs) are the most common form of birth defects, occurring in as many as 1-5% of newborns, and remain the leading noninfectious cause of infant morbidity and mortality in developed countries. Malformation of valves accounts for up to 30% of CHDs. Despite decades of research, the mechanisms underlying congenital valve diseases remain largely elusive. MicroRNAs (miRNAs) have emerged as promising therapeutic targets/agents for various cardiovascular diseases. While critical roles of miRNAs in regulating cardiomyogenesis have been well established, their activities during valvulogenesis, especially in mammals, have been barely studied. Our current knowledge of miRNA function in developing valves is limited to several publications using zebrafish as the primary model system. The lack of knowledge regarding the roles of miRNAs during mammalian valvulogenesis poses a major barrier to developing diagnostic/therapeutic applications for miRNAs against valve diseases. To directly test whether miRNAs are essential for mammalian valve development, we established a mouse model in which Dicer1 is specifically inactivated in embryonic endocardial cells, which are precursors of valve leaflet cells. Our studies reveal for the first time that the miRNA regulatory machinery in endocardial cells is required for normal valvulogenesis to support survival of neonatal mice. We propose the central hypothesis that miRNAs are essential components of the molecular regulatory network governing normal valvulogenesis in mammals. We will test this hypothesis through the following two Specific Aims. In Aim 1, we will determine the effect of globally blocking miRNA biosynthesis in endocardial cells on valvulogenesis in mice. In Aim 2, we will test the role of miRNA-mediated repression of Ptpn11 in preventing valve hyperplasia. MiRNAs play important roles in numerous biological/pathological processes, and yet their functions during mammalian valvulogenesis have not been examined. Accomplishing these studies will significantly advance our fundamental understanding of the complex molecular/genetic mechanisms regulating mammalian valvulogenesis and provide crucial clues regarding the use of miRNAs for clinical applications against congenital valve diseases.