What gives the dentin-enamel junction strength? Structural and mechanical function of collagen and amelogenin.

牙齿中的牙本质-牙釉质连接处(DEJ)提供了一个坚固而坚韧的界面，可以承受长时间的工作 几乎没有改建。然而，导致这些非凡机械的分子组成和结构 人们对房地产的了解仍然很少。具体地说，牙釉质基质中的蛋白质如何与牙本质胶原蛋白相互作用 纤维形成持续矿化的组织，需要加以解决。这个项目的目标是推进我们的 了解DEJ的强度和韧性的纳米级起源。我们建议定义胶原蛋白的作用 和釉原蛋白，主要蛋白分别来自牙本质和釉质，对DEJ的强度通过两种特异性 目标。在第一个目标中，我们将测试牙本质矿物晶体的延伸不需要釉原蛋白 胶原蛋白在阻止全长蛋白质切割的同时，改变了DEJ的结构。在第二个目标中，我们将 证明牙本质胶原蛋白的突变可以影响DEJ的形成和机械性能。我们的第一次 支持这一假说的事实是，釉原蛋白基因敲除小鼠的DEJ看起来完好无损，而小鼠模型缺乏 基质金属蛋白酶-20(MMP20)是釉质蛋白在釉质过程中发生切割的主要酶 分泌物，有一个妥协的DEJ和牙釉质脱层。在我们的第二个目标中，我们将探索 牙本质发育不全小鼠模型中I型胶原的突变改变DEJ。我们将通过以下方式检验这些假设 用高分辨电子显微镜和免疫组织化学技术原位表征 野生型和突变小鼠的DEJ以及有机基质成分。同样，我们将探索有机基质 纳米结构与矿物组织和结晶度的关系。我们还将评估胶原蛋白突变对 它在体外与釉质蛋白有亲和力。最后，我们将量化突变对人的力量和韧性的影响 DEJ使用创新的原子力显微镜进行表征。综上所述，该项目的成果将 极大地提高了我们对DEJ以及导致其不可思议的机械行为的机制的理解。

The dentin-enamel junction (DEJ) in teeth provide a strong and tough interface that can withstand a long working life with little to no remodeling. However, the molecular composition and structure that leads to these remarkable mechanical properties are still poorly understood. Specifically, how proteins from the enamel matrix interact with dentin collagen fibrils to form a continuously mineralized tissue, needs to be addressed. The goal of this project is to advance our understanding of the nanoscale origin of the strength and toughness of the DEJ. We propose to define the role of collagen and amelogenin, the major proteins from dentin and enamel respectively, on the strength of DEJ through two specific aims. In the first aim we will test that amelogenin is not required for the extension of mineral crystals from dentin’s collagen, while preventing the cleavage of the full-length protein alters the structure of the DEJ. In the second aim we will demonstrate that mutations in dentin collagen can affect the formation and mechanical properties of the DEJ. Our first hypothesis is supported by the fact that the DEJ of amelogenin knock-out mice appears intact while mouse models lacking matrix metalloproteinase-20 (MMP-20), the main enzyme responsible for the cleavage of enamel proteins during enamel secretion, have a compromised DEJ and enamel delaminates from the dentin. In our second aim, we will explore how mutation of type I collagen in mouse models of dentinogenesis imperfecta alter the DEJ. We will test these hypotheses by using high-resolution electron microscopy and immunohistochemistry techniques to characterize in situ the morphology of DEJ as well as the organic matrix composition in wild type and mutant mice. Similarly, we will explore the organic matrix nanostructure in relation to mineral organization and crystallinity. We will also assess the impact of collagen mutation on its affinity to enamel proteins in vitro. Finally, we will quantify the impact of mutations on the strength and toughness of the DEJ using innovative atomic force microscopy characterization. Taken together, the results of this project will significantly improve our understanding of the DEJ and on the mechanisms leading to its incredible mechanical behavior.