Role of BMP and Wnt signaling in early tooth development

描述（由申请人提供）：多个信号分子家族，包括BMP、FGF、Shh和Wnt蛋白，都参与了调节牙齿发育的组织相互作用。尽管自BMP4被确定为牙齿形成过程中的潜在形态因子以来，在过去的二十年中取得了重大进展，但这些信号通路的功能机制以及它们如何协同作用来调节牙齿形成仍然是一个谜。我们的长期目标是描述牙形成的分子机制，这将有助于更好地理解人类遗传相关的牙齿异常和牙齿再生。基于我们之前和初步的研究，我们假设BMP和Wnt信号通路在控制牙上皮发育中发挥不同但协同的功能，其中Wnt/b- catenin信号通路调节成牙命运，BMP介导的非规范信号通路调节细胞增殖。而不依赖smad4的典型BMP信号（称为非典型典型BMP信号）则通过调节Msx1的表达，在牙间质中起作用，控制牙生成程序。为了验证这一假设，提出了两个目标。在Aim 1中，我们将几种独特的转基因/基因敲除小鼠系解剖Wnt-和bmp介导的信号通路在调节早期牙齿发育中的独特和协同的生物学功能。为此，我们将：(1)建立Noggin作为Wnt信号拮抗剂的新功能；(2)在牙上皮中确定BMP信号作为细胞增殖的主要调节因子，但不作为成牙命运的调节因子；(3)明确BMP和Wnt信号在早期牙齿发育中的协同作用；(4)确定β-catenin在牙齿发育中的信号功能。在aims 2中，我们将使用几种转基因/敲除小鼠系结合细胞培养，生物化学和分子生物学方法来研究非典型典型BMP信号在牙间质中的作用和调节。为此，我们将；(1)确定TGFb信号通路在牙上皮Smad1/5/8激活中起主要作用；(2)确定非典型典型BMP信号在牙间质中的功能运作；(3)研究非典型典型BMP信号在牙间质中的调控机制。这些研究结果将极大地增强我们对BMP和Wnt信号在牙齿发育中的功能机制的理解，并挑战目前规范的BMP信号模型。

DESCRIPTION (provided by applicant): Multiple families of signaling molecules, including BMP, FGF, Shh, and Wnt protein, have been implicated in mediating tissue interactions that govern tooth development. Despite significant progresses in the last two decades since BMP4 was identified as a potential morphogen in during tooth initiation, functional mechanisms of these signaling pathways and how they act coordinately to regulate tooth formation remain elusive. Our long-term goal to delineate the molecular mechanisms underlying odontogenesis, which shall shed light on for better understanding of genetic related dental abnormalities and tooth regeneration in humans. Based on our previous and preliminary studies, we hypothesize that BMP and Wnt signaling pathways exert distinct but synergistic functions in controlling dental epithelium development, with Wnt/b- catenin signaling regulating odontogenic fate and BMP-mediated non-canonical signaling regulating cell proliferation, while Smad4-independent canonical BMP signaling (named as atypical canonical BMP signaling) acting in the dental mesenchyme to control odontogenic program by regulating Msx1 expression. Two aims are proposed to test this hypothesis. In Aim 1, we will several unique transgenic/knockout mouse lines dissect distinct and synergistic biological functions of Wnt- and BMP-mediated signaling pathways in the regulation of early tooth development. In this aim, we will: (1) Establish a novel function for Noggin as a Wnt signaling antagonist; (2) Establish BMP signaling as a major regulator for cell proliferation but not for odontogenic fate in the dental epithelium; (3) Define synergistic function of BMP and Wnt signaling in early tooth development; (4) Establish definite signaling function for β-catenin in tooth development. In Aim 2, we will use several transgenic/knockout mouse line combined with cell culture, biochemistry, and molecular biology approaches to investigate the role and regulation of atypical canonical BMP signaling in the dental mesenchyme. In this aim, we will; (1) Establish that TGFb signaling is primarily responsible for Smad1/5/8 activation in the dental epithelium; (2) Determine functional operation of atypical canonical BMP signaling in the dental mesenchyme; and (3) Investigate regulatory mechanism of atypical canonical BMP signaling in the dental mesenchyme. Results from these proposed studies will greatly enhance our understanding of functional mechanisms of BMP and Wnt signaling in tooth development and challenge the current model of the canonical BMP signaling.