Biphasic Roles of OSX-WNT-B-Catenin Signaling Pathway in Tooth Root Formation

 描述（由申请人提供）：牙科和NIDCR最重要的目标之一是生成一个完整的“生物牙齿”，它将由牙冠和牙根组成。在过去的三十年里，在牙胚和牙冠形成的研究方面取得了相当大的成就，尽管由于缺乏合适的动物模型，加上处理矿化牙本质的固有困难，牙根研究落后。尽管如此，重要的是要认识到牙根是牙齿的关键结构组成部分，因为：i）有许多遗传综合症和染色体异常会影响牙根结构;和ii）迫切需要产生牙根来治疗牙齿创伤、牙齿发育不全和牙周疾病。我们的长期目标是了解控制牙根形成的生物机制，这将填补知识的关键空白，从而实现再生整个“生物牙齿”的目标。这里的目标，这是我们追求这一目标的下一步，是定义对根至关重要的新兴信号通路。 但不用于牙冠牙本质形成。我们的中心假设是，在牙根牙本质形成的新的控制机制是不同的，在牙冠的形成，其中NFIC，OSX，β-catenin，和DSPP之间的相互作用发挥关键作用。该假设是基于我们使用全局敲除（KO）和条件性KO（cKO）小鼠模型以及体外分子方法产生的强有力的初步数据制定的。本文提出了两个具体的目标来检验这一假设：1）。通过Wnt-β-catenin的负调控和DSPP的正调控，阐明NFIC关键下游转录因子OSX在生后牙根-而非牙冠-牙本质形成中的关键作用;和2）.为了确定阻断升高的β-连环蛋白水平是否在体内挽救Osx cKO牙齿表型，并确定是否重新激活Osx cKO。在Osx cKO或CA-β-catenin小鼠中DSPP的表达恢复牙本质小管形成和矿化。拟议的研究是创新的，因为i）这些基因工程动物模型开发了惊人的牙根表型，而牙冠没有明显的变化; ii）提出的方法将以组织和时间依赖性的方式描绘每个分子在这种新兴信号通路中的新作用。所提出的研究是重要的，因为获得的有价值的信息可以应用于填补这一研究不足的领域的关键知识空白，并有助于对未来生物牙齿替代的一代的调查。

 DESCRIPTION (provided by applicant): One of the most important goals of dentistry and the NIDCR is to generate a whole "Bio-Tooth", which would be composed of crown and root. In the last three decades, considerable achievements have been made in studies of tooth germ and crown formation, although the root studies lag behind due to the lack of appropriate animal models available, plus the inherent difficulties associated with handling mineralized dentin. Nevertheless, it is important to recognize that the root is a critical structural component of the tooth because: i) There are numerous hereditary syndromes and chromosomal anomalies that affect the root structure; and ii) There is an urgent need to generate a root for treatment of dental trauma, tooth agenesis, and periodontal diseases. Our long-term goal is to understand the biological mechanisms controlling root formation, which will fill a key gap of knowledge leading to the goal of regenerating a whole "Bio-Tooth". The objective here, which is our next step in the pursuit of that goal, is to define the emerging signaling pathway(s) essential for root but not for crown dentin formation. Our central hypothesis is that the novel control mechanism in root dentin formation is different from that in the tooth crown formation, in which the interaction among NFIC, OSX, -catenin, and DSPP play key roles. This hypothesis is formulated on the basis of our strong preliminary data produced using both global knockout (KO) and conditional KO (cKO) mouse models, as well as in vitro molecular approaches. Two Specific Aims are proposed to test this hypothesis: 1). To demonstrate the critical role of OSX, the key downstream transcriptional factor of NFIC, in control of postnatal root - but not crown - dentin formation by means of the negative regulation of Wnt--catenin and positive regulation of DSPP; and 2).To determine whether blocking the elevated -catenin level rescues the Osx cKO tooth phenotype in vivo and to define whether re- expressions of DSPP either in the Osx cKO or the CA- -catenin mice restore dentin tubule formation and mineralization. The proposed research is innovative because i) these genetically engineered animal models developed astonishing tooth root phenotypes with no apparent changes in the crown; and ii) the approaches proposed will delineate the novel roles of each molecule in this emerging signaling pathway in a tissue- and temporal-dependent manner. The studies proposed are significant because the valuable information gained can be applied to fill the critical knowledge gap in this understudied area and contribute to investigations on the generation of a future biological tooth replacement.