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，发生在高达1%-5%的新生儿中，在发达国家仍然是导致婴儿发病率和死亡率的主要非传染性原因。瓣膜畸形占先天性心脏病的30%。尽管进行了数十年的研究，但先天性瓣膜疾病的潜在机制在很大程度上仍然难以捉摸。MicroRNAs(MiRNAs)已成为多种心血管疾病的治疗靶点和药物。虽然miRNAs在调节心肌发生中的关键作用已经得到很好的证实，但它们在瓣膜发生过程中的活动，特别是在哺乳动物中，几乎没有研究过。我们目前对miRNA在瓣膜发育中的功能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。对miRNAs在哺乳动物瓣膜形成过程中的作用缺乏了解，这是开发miRNAs在瓣膜疾病诊断/治疗应用中的主要障碍。为了直接测试miRNAs对哺乳动物瓣膜发育是否必不可少，我们建立了一个小鼠模型，在该模型中，Dicer1在胚胎心内膜细胞中被特异性失活，而心内膜细胞是瓣膜叶细胞的前体。我们的研究首次揭示了心内膜细胞中的miRNA调节机制是正常的瓣膜形成所必需的，以支持新生小鼠的生存。我们提出的中心假设是miRNAs是调控哺乳动物正常心脏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。在目标1中，我们将确定全局阻断心内膜细胞miRNA生物合成对小鼠心脏瓣膜形成的影响。在目标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。MiRNAs在许多生物/病理过程中发挥着重要作用，但它们在哺乳动物瓣膜形成过程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控哺乳动物瓣膜形成的复杂分子/遗传机制的基本理解，并为将miRNAs用于临床治疗先天性瓣膜疾病提供重要线索。

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.