STUDY OF THE FORMATION OF ENAMEL CRYSTALLITES BY AMELOGENINS

釉蛋白形成牙釉质微晶的研究

• 批准号: 7357291
• 负责人: WILLIAM J LANDIS
• 金额: $ 0.23万
• 依托单位: WADSWORTH CENTER
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-02-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7357291
• 关键词: STUDY; FORMATION; ENAMEL; CRYSTALLITES; AMELOGENINS

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The formation of enamel in the teeth of vertebrates, including rodents and man, is mediated by specific cells, the ameloblasts, that synthesize and secrete a class of small proteins, the amelogenins, into the extracellular matrices of this tissue. At locations close to the points of secretion along the so-called Tomes' processes of the ameloblasts, the amelogenins have been proposed to undergo assembly into two- or three-dimensional arrays of nanospheres, ~20-25 nm in diameter. These arrays are thought to initiate the deposition of enamel, long ribbon-like crystallites chemically identified as apatite (a calcium phosphate) and themselves organized in three-dimensions. The assembly of nanospheres and their interactions wtih calcium and phosphate ions (in the extracellular matrices of the ameloblasts) leading to nucleation and growth of enamel mineral are poorly defined and understood. Conventional electron microscopy and atomic force microscopy have been used previously to help characterize these putative events, but both techniques have been limited in their utility and the interpretation of their resulting data. The principal reasons for the limitations lie in the use of sample preparation methods that alter enamel crystal composition or structure and, in the case of conventional electron microscopy, images that are two-dimensional rather that three. High voltage electron microscopy and tomographic imaging are technical approaches that hold promise of providing novel three-dimensional information on the assembly of nanospheres, their interaction with nascent enamel crystallites, and the elaboration of the mineral ribbons. Combined with anhydrous sample preparation, including the use of ethylene glycol or cryofixation that does not interfere with mineral composition or structure, high voltage microscopy and tomographic reconstruction of collected images should be extremely powerful in circumventing the uncertain techniques of analysis that have been applied earlier. In addition to investigations of normal enamel specimens obtained from mice as well accepted models for human tooth structure, two available mutant animals will also be examined. These mice contain known genetic alterations in the structure of their constituent amelogenin proteins and, as a result, they should mediate enamel crystallites that are different from those determined by normal amelogenins. In these studies of mouse mutants, high voltage and tomography will be applied to identify putative changes in their ameloblast nanosphere assembly and enamel mineral organization. In the previous reporting period, Dr. Landis visited the RVBC to review archived data from past years.

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。脊椎动物（包括啮齿动物和人类）牙齿的牙釉质形成是由一种特殊的细胞介导的，即成釉细胞，这种细胞合成并分泌一类小蛋白质，即成釉原蛋白，并将其分泌到牙齿组织的细胞外基质中。在靠近成釉细胞分泌点的地方，这些成釉原蛋白被认为是在直径约20-25纳米的纳米球的二维或三维阵列中组装的。这些排列被认为引发了牙釉质的沉积，牙釉质是一种长带状晶体，化学上被鉴定为磷灰石（一种磷酸钙），它们自己以三维形式组织。纳米球的组装及其与钙和磷酸盐离子（在成釉细胞的细胞外基质中）的相互作用导致珐琅质矿物成核和生长的定义和理解尚不清楚。传统的电子显微镜和原子力显微镜以前被用来帮助描述这些假定的事件，但这两种技术在其效用和对其结果数据的解释方面都受到限制。限制的主要原因在于使用的样品制备方法改变了珐琅晶体的组成或结构，并且在传统电子显微镜的情况下，图像是二维的而不是三维的。高压电子显微镜和层析成像技术有望为纳米球的组装、它们与新生珐琅晶体的相互作用以及矿物带的精细加工提供新的三维信息。结合无水样品制备，包括使用乙二醇或不干扰矿物成分或结构的冷冻固定，高压显微镜和收集图像的层析重建应该非常强大，可以避免先前应用的不确定分析技术。除了研究从小鼠身上获得的正常牙釉质标本作为人类牙齿结构的公认模型外，还将研究两种可用的突变动物。这些小鼠在其组成淀粉原蛋白的结构中含有已知的遗传改变，因此，它们应该介导与正常淀粉原蛋白决定的不同的牙釉质晶体。在这些小鼠突变体的研究中，高压和断层扫描将被应用于确定成釉细胞纳米球组装和搪瓷矿物组织的推定变化。在上一个报告期间，兰迪斯博士访问了RVBC，审查了过去几年的存档数据。