Enamel Structure Sophistication throuth Amelogenin Evolution

描述（由申请人提供）：牙釉质由紧密堆积的碳化羟基磷灰石晶体组成，这些晶体被组织成杆（棱柱），以交替的方式相互倾斜地运行。这种非凡的3D结构是在牙釉质发育过程中，由于细胞过程和有机基质分泌的协调活动而建立的。目前的建议集中在主要的釉质基质基因产物，淀粉原蛋白的独特的c结构域的作用，因为它涉及到釉质结构组织。在之前的研究中，我们已经记录了在两栖/爬行动物向哺乳动物过渡期间，淀粉原蛋白c结构域脯氨酸和谷氨酰胺串联重复序列和棱柱状牙釉质组织的显著增加。在目前的应用中，我们正在使用这种进化生物学方法来破译淀粉原蛋白c结构域在复杂牙釉质结构进化中的作用。作为第一步，我们已经建立了青蛙过表达淀粉原蛋白的小鼠模型，其特征是牙釉质矿物组织严重改变，缺乏棱柱形成。当amel过表达者与无amel小鼠杂交时，牙釉质厚度进一步减少，晶状体缺失。为了了解淀粉原蛋白基因的特定结构域如何影响脊椎动物进化过程中牙釉质生物矿化的改变，我们现在提交了一项研究计划，以确定淀粉原蛋白c结构域进化对牙釉质基质组织、牙釉质晶体和棱柱形成的影响。我们的研究旨在验证一种假设，即复杂的哺乳动物牙釉质结构是由淀粉原蛋白c结构域进化促进的牙釉质基质结构复杂的结果。

DESCRIPTION (provided by applicant): Tooth enamel consists of tightly packed carbonated hydroxyapatite crystals which are organized into rods (prisms) running obliquely to one another in alternating rows. This extraordinary 3D architecture is established during enamel development as a result of the coordinated activity of cellular processes and organic matrix secretion. The present proposal focuses on the role of the unique C-domain of the major enamel matrix gene product, amelogenin, as it pertains to enamel structural organization. In previous studies, we have documented a significant increase in amelogenin C-domain proline and glutamine tandem repeats and prismatic enamel organization during the amphibian/reptile to mammal transition. In the present application, we are using this evolutionary biology approach to decipher the role of the amelogenin C-domain in the evolution of complex enamel structure. As a first step, we have generated frog amelogenin- overexpressing mouse models featuring grossly altered enamel mineral organization and lack of prism formation. Enamel thickness was further decreased and prisms were lacking when amel-overexpressors were crossed with amel null mice. In order to understand how specific domains of the amelogenin gene might affect alterations in enamel biomineralization during vertebrate evolution, we are now submitting a research plan to determine the effect of amelogenin C-domain evolution as it relates to enamel matrix organization, enamel crystal and prism formation. Our studies are designed to test the hypothesis that complex mammalian enamel architecture is a result of enamel matrix structure sophistication facilitated by amelogenin C-domain evolution. PUBLIC HEALTH RELEVANCE: The purpose of this research project is to identify key factors in tooth enamel formation. Tooth enamel in frog teeth is thin, little organized, and soft, while tooth enamel in mammals' features sophisticated organization and is thicker and harder than frog enamel. Here we are comparing the difference between frog and mouse enamel to identify key differences in enamel formation on a protein level. We are interested in the center portion of the major enamel protein, amelogenin. We believe that this center portion plays an important role in enamel formation and we will use a number of models to find out whether our thinking is accurate. Among those model systems will be experiments in which we will mix this protein with crystal growth solutions and experiments in which we manipulate the major gene in mice. We hope that one day our approach will lead to new ways of repairing human teeth.