Enamel Structure Sophistication throuth Amelogenin Evolution

描述(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，这些晶体组织成棒状(棱柱)，相互倾斜，交替排列。这种非凡的3D结构是在釉质发育期间建立的，这是细胞过程和有机基质分泌协调活动的结果。本提案侧重于主要釉质基质基因产物釉原蛋白的独特C结构域在釉质结构组织中的作用。在以前的研究中，我们已经记录到在两栖类/爬行动物向哺乳动物的转变过程中，釉原蛋白C结构域、脯氨酸和谷氨酰胺串联重复序列以及棱柱状釉质组织显著增加。在目前的应用中，我们正在使用这种进化生物学的方法来破译釉原蛋白C结构域在复杂釉质结构进化中的作用。作为第一步，我们已经建立了青蛙釉原蛋白过度表达的小鼠模型，其特征是釉质矿物组织发生了严重变化，缺乏棱柱形成。当AMEL过表达的小鼠与AMEL缺失的小鼠杂交时，釉质厚度进一步减少，棱镜缺失。为了了解釉原蛋白基因的特定结构域在脊椎动物进化过程中如何影响釉质生物矿化的变化，我们现在提交了一项研究计划，以确定釉原蛋白C结构域进化的影响，因为它与釉质基质组织、釉质晶体和棱柱形成有关。我们的研究旨在验证这一假说，即复杂的哺乳动物釉质结构是釉原蛋白C结构域进化促进的釉质基质结构复杂的结果。 公共卫生相关性：本研究项目的目的是确定牙釉质形成的关键因素。青蛙牙齿的牙釉质薄、组织少、柔软，而哺乳动物的牙釉质组织复杂，比青蛙牙釉质更厚、更硬。在这里，我们正在比较青蛙和小鼠牙釉质的差异，以确定在蛋白质水平上牙釉质形成的关键差异。我们对主要的釉质蛋白--釉原蛋白的中心部分感兴趣。我们认为，这一中心部分在釉质形成中起着重要作用，我们将使用一些模型来验证我们的想法是否准确。在这些模型系统中，将包括我们将这种蛋白质与晶体生长溶液混合的实验，以及我们在小鼠身上操纵主要基因的实验。我们希望有一天，我们的方法将导致修复人类牙齿的新方法。

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.