CEMENTOGENESIS: ROLE OF HERTWIG'S EPITHELIAL ROOT SHEATH

描述（由申请人提供）：尽管我们对调节牙齿发育的生长因子和转录因子已经有了大量的了解，但是在牙齿发育的后期，即矿化组织形成的阶段，有关调节牙根发育的因素的信息仍然缺乏，而关于调节牙根发育的因素的信息则更加缺乏。本研究的长期目标是在形态学、细胞和分子水平上了解牙根发育的过程，包括牙根本质和牙骨质形成的机制，以及牙根与健康牙周膜的附着。在本应用中，我们将重点关注Hertwig's上皮根鞘（HERS）细胞在根发育中的作用。虽然HERS细胞在根形成中的作用被广泛接受，但这些细胞的确切功能和命运仍然存在争议。这些细胞的功能范围从纯粹的结构实体（将牙外间充质组织细分为牙乳头和牙滤泡），到根发育时间的调节剂，到间充质细胞分化为成骨水泥细胞的诱导剂，再到成骨水泥细胞的前体。在这一竞争性更新中，我们将验证一个假设，即根发育是由HERS细胞通过与周围间质的动态和相互作用启动的，从而导致出芽形态发生，并且存在一个与这些组织相关的独特基因，该基因受NFI-C转录因子的调节。我们建议通过利用新创建的Nfi-c（核因子I-C）敲除小鼠敲除来验证这一假设，其独特的表型是缺乏根的形成。此外，我们将使用已建立的不朽细胞系（HERS，牙乳头间充质（DPM），牙毛囊）来完成以下具体目标：确定导致根形态发生的初始事件；确定什么样的细胞相互作用是根发育所必需的；确定与根发育有关的分子；确定已鉴定的分子在根系发育中的作用。使用广泛的技术，包括原位杂交、组织重组、器官培养、细胞培养、微阵列技术等，将提供完成我们特定施舍所需的数据。本研究的数据将为根系发育、HERS在这一过程中的作用以及参与根系形成的调控因子提供急需的信息。虽然罕见，个体与根发育不良已被记录。

DESCRIPTION (provided by applicant): Despite the tremendous knowledge related to the growth and transcription factors that regulate tooth development, there is still a lack of information related to the factors involved at later stages of tooth development, when the mineralized tissues are formed, and an even greater paucity of information as to the factors that regulate root development. It is the long-term objective of this study to understand the process of root development at the morphologic, cellular and molecular levels including the mechanisms underlying root dentin and cementum formation as well as root attachment to periodontal ligament in the healthy periodontium. In this application, we will focus on the role of Hertwig's Epithelial Root Sheath (HERS) cells in root development. Although the role of HERS cells in root formation is widely accepted, the precise function and fate of these cells remains controversial. Functions suggested for these cells have ranged from a pure structural entity (subdivide the dental ectomesenchymal tissues into dental papilla and dental follicle), to regulators of the timing of root development, to inducers for mesenchymal cells differentiation into cementoblasts, to being cementoblast cells precursors. In this competing renewal we will test the hypothesis that that root development is initiated by HERS cells through dynamic and reciprocal interactions with the surrounding mesenchyme resulting in budding morphogenesis and there is a unique gene associated with these tissues that is regulated by the NFI-C transcription factor. We propose to test this hypothesis by taking advantage of a newly created Nfi-c (Nuclear Factor I-C) knockout mice knock whose unique phenotype is that it lacks the formation of roots. In addition we will use established immortal cell lines (HERS, Dental Papillae Mesenchyme (DPM), dental follicle) to accomplish the following Specific Aims: To determine the initial events leading to root morphogenesis; To determine what kind of cell interactions are necessary for root development; To determine the molecules associated with root development; To determine the role of the molecules identified in root development. The use of a wide range of technology including in situ hybridization, tissue recombination, organ culture, cell culture, microarrays technology, etc. will provide the data required to accomplish our specific alms. The data generated in this study will provide much needed information related to root development, the role of HERS in this process and the regulatory factors involved in root formation. Although rare, individuals with root agenesis have been documented.