The Role of the C-terminus of Amelogenen in Enamel Structure

描述(申请人提供)：正确的釉质形成需要结构基质蛋白和蛋白水解酶的协调分泌以及矿化，以形成体内最坚硬和最矿化的组织。釉原蛋白占成釉细胞分泌的有机基质的90%，是釉质矿化所必需的。釉原蛋白的突变会导致成釉不全，这是一种导致釉质缺陷的遗传性疾病。釉原蛋白的不同区域负责牙釉质矿化过程的不同方面。釉原蛋白是由成釉细胞在釉质形成过程中分泌的蛋白水解酶(如MMP20)处理的。釉原蛋白的C末端被认为是正确形成和组装纳米球、指导矿物晶体生长的球形蛋白质聚集体以及与羟基磷灰石矿物相互作用所必需的。为了利用转基因小鼠和成釉蛋白缺失小鼠检测釉原蛋白C-末端在釉质结构完整性中的作用，本建议将：1)确定缺乏釉原蛋白C-末端对釉质微观结构和纳米机械性能的影响；2)确定C-末端加工MMP20对釉质微结构、纳米机械特性和有机基质去除的重要性；以及3)检测成釉蛋白C-端突变小鼠的棒状组织和成釉细胞的突起形态。 公共卫生相关性：这项研究将有助于目前对釉质基质蛋白在釉质发育和矿化中的作用的了解。对含有釉原蛋白和其他釉质基质基因突变的转基因小鼠模型的分析可以增加对患者不同铝表型及其相应基因突变的了解。因此，铝和其他釉质紊乱的临床治疗和方法可以得到改进。

DESCRIPTION (provided by applicant): Proper enamel formation requires coordinated secretion of both structural matrix proteins and proteases along with mineralization to form the hardest and most mineralized tissue in the body. Amelogenins constitute 90% of the organic matrix secreted by ameloblasts and are required for enamel mineralization. Mutations in amelogenin cause Amelogenesis Imperfecta (Al), which is a genetic disorder that causes enamel defects. Different regions of the amelogenin protein are responsible for varying aspects of the enamel mineralization process. Amelogenins are processed by proteolytic enzymes also secreted by ameloblasts, such as MMP20, during enamel formation. The C-terminus of amelogenin is thought to be required for proper formation and assembly of nanospheres, spherical protein aggregates that guide mineral crystal growth, and interaction with hydroxyapatite mineral. To examine the role of the C-terminus of amelogenin in enamel structural integrity using transgenic and amelogenin null mice, this proposal will: 1) determine the effect of the lack of the amelogenin C-terminus on enamel microstructure and nanomechanical properties; 2) determine the importance of MMP20 processing of amelogenin at the C-terminus on enamel microstructure, nanomechanical properties, and organic matrix removal; and 3) examine rod organization and ameloblast Tomes' process morphology in mice with an amelogenin C-terminal mutation. PUBLIC HEALTH RELEVANCE: This research will contribute to the current knowledge of the role of enamel matrix proteins in enamel development and mineralization. Analysis of transgenic mouse models with mutations in amelogenin and other enamel matrix genes can lead to increased understanding of different Al phenotypes and their corresponding genetic mutations in patients. As a result, clinical treatments and approaches for humans with Al and other enamel disorders can be improved.