Characterization of the structure and function of DMP2

骨骼和牙齿的适当矿化在正常的人类生长和发育中具有重要意义，包括肌肉骨骼功能。 这些组织中的矿物质相有助于结构的硬度和综合强度，并且还具有作为钙和镁的代谢库的主要生理作用。 矿化过程中的问题在许多骨骼病变中是明显的。 矿化组织研究中最有趣的问题之一是，在生理环境中，循环的钙和磷酸盐以及其他矿物质相离子如何集中在特定的局部器官或组织中。 到目前为止，我们对这一级联的启动和调节过程几乎没有定义。然而，有机基质被认为在调节矿化过程中起着重要作用。 我们的工作主要集中在牙本质矿化上，因为它是一个比骨更简单的系统，但这两种机制可能密切相关。 我们对基质介导的矿化的基本假设是，酸性大分子首先结合在胶原基质内，这些大分子负责成核和启动矿化级联反应。 可能这些酸性大分子也调节碳酸化羟基磷灰石晶体的大小。在寻找编码牙本质主要酸性非胶原蛋白（NCP）即磷酸化蛋白（PP）的基因时，我们鉴定了两个克隆，一个代表磷酸化蛋白，现命名为牙本质基质蛋白2（DMP 2），另一个代表磷酸化蛋白，是牙本质涎蛋白和一个小磷酸化蛋白样结构域的复合物。 从部分DMP 2 cDNA推导的氨基酸序列是特别感兴趣的，因为它清楚地代表了预期的牙本质基质组分的富含天冬氨酸和丝氨酸的酸性蛋白质类型。 该基因已被紧密定位于小鼠染色体5 q21，相当于人类染色体4 Q21。 由于人类染色体4 q13 -21与牙本质矿化障碍牙本质形成II型牙本质形成相关，因此该染色体位置特别有趣。 为了扩大我们对DMP 2基因结构及其功能的理解，我们提出了以下具体目标：（1）确定大鼠DMP 2的完整一级结构（2）描绘DMP 2启动子序列并鉴定参与组织特异性调节的元件（3）克隆人DMP 2基因以最终鉴定牙本质生成不全II型患者的基因改变（4）研究牙胚发育过程中DMP 2表达的时空变化规律。 长期目标是了解DMP 2在牙本质矿化中的调控机制。

The proper mineralization of bones and teeth has great importance in normal human growth and development including musculo-skeletal functions. The mineral phase in these tissues contributes to the hardness and comprehensive strength of the structure and also has a major physiological role as the metabolic reservoir of calcium and magnesium. Problems in the mineralization process are evident in a number of skeletal pathologies. One of the most interesting questions in mineralized tissue research is how, within the physiological environments, circulating calcium and phosphate and other mineral phase ions can be concentrated in specific, localized organs or tissues. Up until this point we have defined little about the process by which this cascade is initiated and regulated. However, the organic matrix has been implicated to have a major role in regulating the mineralization process. We have focussed our efforts primarily on dentin mineralization because it is a simpler system than bone, but the two mechanisms are probably closely related. Our basic hypothesis for matrix-mediated mineralization, is that acidic macromolecules first bind within the collagen matrix and these are responsible for nucleating and starting the mineralization cascade. Probably these acidic macromolecules also regulate the size of carbonated hydroxyapatite crystals. In the search for the gene encoding for the principle acidic noncollagenous protein (NCP) of dentin, namely phosphophoryn (PP) we identified 2 clones one representing phosphophoryn now named DMP2 (dentin matrix protein 2) and the other DMP3 (dentin matrix protein 3) which is a compound of dentin sialoprotein and a mini "phosphophoryn"like domain. The amino acid sequence deduced from the partial DMP2 cDNA is of special interest because it clearly represents an aspartic acid and serine rich acidic protein of the type to be expected of a dentin matrix component. This gene has been tightly localized to mouse chromosome 5q21, equivalent to human chromosome 4Q21. This chromosome location is especially interesting because of the linkage of human chromosome 4q13-21 with the dentin mineralization disorder dentinogenesis imperfecta type II. In order to expand our understanding of the DMP2 gene structure and its function we propose the following specific aims: (1) To determine the complete primary structure of rat DMP2 (2) To delineate DMP2 promoter sequences and identify elements involved in tissue -specific regulation (3) To clone the human DMP2 gene in order to ultimately identify gene alterations in patients with Dentinogenesis Imperfecta Type II (4) To examine the temporal and spatial patterns of DMP2 expression during tooth development (5) To determine the calcium binding property of DMP2. The long-term goal is to understand the regulatory mechanism of DMP2 in dentin mineralization.