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

描述（由申请人提供）：适当的牙釉质形成需要结构基质蛋白和蛋白酶的协调分泌以及矿化，以形成体内最坚硬和矿化程度最高的组织。成釉原蛋白占成釉细胞分泌的有机基质的90%，是牙釉质矿化所必需的。淀粉原蛋白的突变导致淀粉原性不全症（Al），这是一种导致牙釉质缺陷的遗传性疾病。淀粉原蛋白的不同区域负责釉质矿化过程的不同方面。在珐琅质形成过程中，成釉细胞（如MMP20）分泌的蛋白水解酶也会处理成釉原蛋白。淀粉原蛋白的c端被认为是纳米球的正确形成和组装所必需的，球形蛋白质聚集引导矿物晶体生长，并与羟基磷灰石矿物相互作用。为了研究淀粉原蛋白c端在牙釉质结构完整性中的作用，本研究将利用转基因和无淀粉原蛋白小鼠：1)确定淀粉原蛋白c端缺失对牙釉质微观结构和纳米力学性能的影响；2)确定c端淀粉原蛋白MMP20处理对牙釉质微观结构、纳米力学性能和有机基质去除的重要性；3)观察变淀粉原c端突变小鼠的棒状组织和成釉细胞Tomes过程形态。

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.