Individual Predoctoral Dental Scientist Fellowship

描述(申请人提供)：目前，对牙齿发育后期的组织特异性基因调控知之甚少，尤其是与牙本质矿化相关的基因调控。最近的研究发现，转化生长因子-β1(TGF21)是牙本质细胞外基质(DECM)形成的潜在调节剂。研究表明，TGF21可诱导未成熟的牙乳头间充质细胞向成牙本质细胞分化。TGF21最初由釉质器官上皮细胞分泌，已被证明在牙本质形成过程中产生牙本质的成牙本质细胞中上调，并整合到DECM中。然而，在成熟的成牙本质细胞中，TGF21被证明下调DECM蛋白，如牙本质基质蛋白-1(DMP-1)和牙本质涎磷蛋白(DSPP)，这是骨/牙本质基质蛋白中的两个小整合素结合配体N-连接糖蛋白(兄弟)家族。基质细胞外磷酸糖蛋白(MEPE)是牙齿中特征最少的同胞成员，其在矿化过程中的作用似乎存在争议。初步研究表明，在一种新的Camurati-Engelmann病(CED)转基因小鼠模型中，TGF21对牙本质层和牙髓细胞中兄弟姐妹蛋白和基因的表达具有失调作用。CED虽然罕见，但最常见的原因是TGFB1基因点突变导致成熟、活跃的TGF21分子过度表达。CED患者表现出严重的骨质增厚和随后的软组织压缩。CED通过常染色体显性遗传传播，此前尚未有人类CED与牙齿异常有关的报道。我们的假设是，转基因CED小鼠模型显示出异常的牙本质形成，这是由成熟的TGF21过表达引起的兄弟姐妹，特别是MEPE的表达改变所介导的。这些特异性的目的是确定TGF21过表达对牙本质基质形成和成熟的信号作用，阐明MEPE在牙本质矿化中的作用，并确定TGF21调节MEPE表达的方式。将使用新的小鼠模型和体外系统，并通过放射和矿物质密度微型计算机断层扫描检查，以及生化和功能分析来表征。从这些研究中获得的信息将为理解牙本质正常和病理性发育的分子机制提供基础。最终，拟议的研究将有助于开发新的诊断工具和治疗方法，用于龋齿、各种牙齿/骨骼矿化障碍或牙本质形成改变综合征的患者。这项研究将阐明牙齿/骨基质材料特性在口腔和骨骼健康和疾病中的作用。 公共卫生相关性：我在UAB牙科学院DMD/PHD(分子和细胞病理学)项目的研究生论文工作建议的研究将集中在牙本质的矿化，特别是基质细胞外磷酸糖蛋白(MEPE)的功能，这是一种特别存在于骨骼和牙齿中的蛋白质，受大多数组织中的一种共同成分-转化生长因子-21(TGF21)的调节。这些研究将有助于我们了解矿化是如何在骨骼和牙齿中正常发生的，哪些因素特别是在牙齿的牙本质层增强或减少矿化过程，以及哪些分子事件在人类矿化障碍中扰乱骨和牙齿的形成。这项工作有可能为患有遗传性或非遗传性组织矿化障碍(如长骨过度增厚、牙髓异常钙化或牙齿发育)的个体开发新的治疗方法。

DESCRIPTION (provided by applicant): Currently, very little is known regarding tissue-specific gene regulation during the later stages of tooth development, especially those associated with dentin mineralization. Recent studies have identified transforming growth factor-beta 1 (TGF21) as a potential modulator of primary dentin extracellular matrix (DECM) formation. TGF21 has been shown to initiate odontoblast cytodifferentiation from immature dental papilla mesenchymal cells. Initially secreted by enamel organ epithelium, TGF21 has been shown to be upregulated in dentin-producing odontoblasts during primary dentinogenesis and become incorporated into the DECM. In mature odontoblasts, however, TGF21 has been shown to downregulate DECM proteins such as dentin matrix protein-1 (DMP-1) and dentin sialophosphoprotein (DSPP), two of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family of bone/dentin matrix proteins. Matrix extracellular phosphoglycoprotein (MEPE), the least characterized SIBLING member in teeth, seems to have controversial roles in mineralization. Preliminary studies demonstrate that TGF21 dysregulates SIBLING protein and gene expression in the dentin layer and in pulp cells of a novel transgenic mouse model for Camurati-Engelmann disease (CED). CED, though rare, is most often due to a point mutation in the TGFB1 gene leading to overexpression of the mature, active TGF21 molecule. Patients with CED present with severe bone thickening and subsequent soft tissue compression. Transmitted through autosomal dominant inheritance, CED in humans has not been previously reported to be associated with dental abnormalities. Our hypothesis is that the transgenic CED mouse model displays abnormal dentin formation as mediated by altered expression of the SIBLINGs, in particular MEPE, caused by the overexpression of mature TGF21. The specific aims seek to identify the signaling effects that overexpression of TGF21 has on dentin matrix formation and maturation, to clarify the function of MEPE in dentin mineralization, and to determine the way in which TGF21 regulates Mepe expression. Novel mouse models and in vitro systems will be used and characterized by way of radiographic and mineral density microcomputed tomography examinations, along with biochemical and functional assays. The information obtained from these studies will provide a foundation for understanding the molecular mechanisms involved in both normal and pathological dentin development. Eventually the proposed studies will facilitate the development of novel diagnostic tools and therapeutic treatments for patients with dental caries, various tooth/bone mineralization disorders, or syndromes with altered dentin formation. This research will elucidate the role of tooth/bone matrix material properties in oral and skeletal health and disease. PUBLIC HEALTH RELEVANCE: The proposed research for my graduate thesis work in the UAB DMD/PhD (Molecular and Cellular Pathology) program at UAB School of Dentistry will focus on dentin mineralization, particularly, the function of matrix extracellular phosphoglycoprotein (MEPE), a protein found especially in bones and teeth, as regulated by a common component in most tissues, transforming growth factor-21 (TGF21). These studies will contribute to our knowledge of how mineralization occurs normally in bones and teeth, which factors enhance or reduce the mineralization process specifically in the dentin layer of teeth, and which molecular events disrupt bone and tooth formation in human mineralization disorders. This work has potential to lead to the development of novel therapeutics for individuals with genetic or non-hereditary tissue mineralization disorders (e.g. excessive thickening of long bones, abnormal dental pulp calcification or tooth development).