MicroRNA in Liver Development

描述(由申请人提供)： 基因表达的控制是生物发育和动态平衡的核心，在疾病过程中，发育途径经常被打乱。这在肝胆疾病中尤其如此，20多种先天性疾病与胆管的分化、形态发生和维持方面的缺陷有关。胆道闭锁包括胆道闭锁，约1/3的病例与胆管发育缺陷有关(1，2)。鉴于胆道闭锁是儿童肝移植最常见的适应症，了解胆管发育的分子基础可能对人类健康有重大影响。近年来，人们发现了一种意想不到的基因调控形式，即被称为microRNAs(MiRNA)的小RNA分子通过RNA干扰抑制靶基因的表达(综述见(3-5))。人类有500多个miRNAs，它们可能共同调节所有基因的20%-30%(6-8个)。关于miRNA在肝脏发育和疾病中的作用，人们几乎一无所知。为了解决这一问题，我们对小鼠肝脏发育过程中miRNA的表达进行了首次大规模研究(见初步数据)，从而识别出其时空表达提示发育功能的肝脏miRNAs。其中miR-30a主要表达于胆管板和胆管。我们利用斑马鱼模型系统作为快速、初步的实验来测试miR-30a的功能。初步研究表明，斑马鱼miR-30a对胆管的正常发育和功能至关重要。本研究旨在研究miR-30a在哺乳动物肝脏中的生物学和分子功能。在目标1中，我们将建立小鼠肝脏miR-30a缺陷的模型，并测量该缺陷对胆管结构和功能的影响。在目标2中，我们将使用这个模型、细胞培养模型和计算预测来对肝脏中的miR-30a靶点进行大规模调查。这项研究具有重要意义，因为它可能首次证明在肝脏发育过程中需要miRNA，并将极大地增加我们对控制这一生物过程的调控途径的有限理解。它直接涉及NIH肝脏研究行动计划中关于肝脏发育的目标(12)。 项目简介这项提案将研究一种最近发现的在肝脏内胆管形成过程中的基因调控形式。这将帮助我们了解肝脏的正常发育，以及在与胆管畸形相关的一系列疾病中，这一过程是如何出错的。然后，这些见解可以应用于更好地治疗肝脏和胆管疾病。

DESCRIPTION (provided by applicant): Project Summary The control of gene expression is at the core of biological development and homeostasis, and developmental pathways are often disrupted in disease processes. This is particularly true in hepatobiliary disease, as illustrated by the existence of over 20 congenital disorders associated with defects in the differentiation, morphogenesis, and maintenance of the bile ducts. This class includes biliary atresia, of which approximately 1/3rd of cases are associated with a developmental defect of the bile ducts (1, 2). In light of the fact that biliary atresia is the most common indication for pediatric liver transplantation, an understanding of the molecular basis of bile duct development may have a significant impact on human health. In recent years, an unexpected form of gene regulation has been discovered in which small RNA molecules known as microRNAs (miRNA) repress the expression of target genes through RNA interference (reviewed in (3-5)). There are over 500 human miRNAs and these may collectively regulate 20-30% of all genes (6-8). Virtually nothing is known regarding the function of miRNA in liver development and disease. To address this, we have performed the first large-scale study of miRNA expression during mouse liver development (see Preliminary Data), resulting in the identification of hepatic miRNAs whose spatio-temporal expression is suggestive of developmental functions. One of these (miR- 30a) is predominantly expressed in the ductal plate and bile ducts. We have utilized the zebrafish model system as a rapid, preliminary assay to test the function of miR-30a. As shown in the Preliminary Studies, zebrafish miR-30a is critical for the normal development and function of bile ducts. This proposal aims to investigate the biological and molecular function of miR-30a in the mammalian liver. In Aim 1, we will derive a mouse model of hepatic miR-30a deficiency and we will measure the effects of this deficiency on biliary structure and function. In Aim 2, we will use this model, a cell culture model, and computational prediction to perform a large-scale survey of miR-30a targets in the liver. The research proposed is significant because it may provide the first demonstration of a requirement for miRNA in liver development and it will significantly add to our limited understanding of the regulatory pathways controlling this biological process. It directly addresses goals of the NIH Action Plan for Liver Research regarding liver development (12). Project Narrative This proposal will study a recently-discovered form of gene regulation during the formation of the the [sic] bile ducts within the liver. This will help us to understand the normal development of the liver and the ways in which that process goes awry in a spectrum of diseases associated with malformations of the bile ducts. Those insights can then be applied towards better treatment of diseases of the liver and bile ducts.