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.

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子弹和调查员（PI）可能已经从其他NIH来源获得了主要资金，因此可以在其他清晰的条目中代表。列出的机构适用于该中心，这不一定是调查员的机构。包括啮齿动物和人在内的脊椎动物牙齿中的牙釉质形成是由特定细胞，成纤维细胞的介导的，这些细胞合成并分泌一类小蛋白质蛋白（amelelogenins），分为该组织的细胞外基质。在沿着所谓的小素细胞过程中分泌的位置接近分泌的位置，已提出amelogenins将组装成两维纳米球阵列，直径约为20-25 nm。这些阵列被认为可以启动牙釉质的沉积，长色的结晶石化学鉴定为磷灰石（磷酸钙），并在三维中组织。纳米球的组装及其相互作用WTIH钙和磷酸离子（在木质细胞的细胞外基质中），导致搪瓷矿物质的成核和生长的定义很差和理解。先前已使用常规电子显微镜和原子力显微镜来帮助表征这些推定事件，但是两种技术的效用及其对所得数据的解释都受到限制。局限性的主要原因在于使用样品制备方法改变牙釉质晶体组成或结构，并且在常规电子显微镜的情况下，图像是二维而不是三个。高压电子显微镜和层析成像是技术方法，其有望提供有关纳米球组装的新型三维信息，它们与新生的搪瓷晶体的相互作用以及矿物质丝带的阐述。 结合无水样品制备，包括使用不干扰矿物质成分或结构的乙二醇或冷冻固定，高压显微镜和收集图像的层析成像重建在避免早期已应用的不确定分析技术方面应非常强大。除了研究从小鼠获得的正常牙釉质标本以及人类牙齿结构的良好模型外，还将检查两种可用的突变动物。这些小鼠在其组成蛋白蛋白的结构中包含已知的遗传改变，因此，它们应介导与正常氨基蛋白酶确定的牙釉质结晶石。在这些小鼠突变体的研究中，将应用高电压和断层扫描来确定其成成木细胞纳米组装和搪瓷矿物质组织的推定变化。在上一个报告期间，Landis博士访问了RVBC，以审查过去几年的存档数据。