Characterization of the structure and function of DMP2

骨骼和牙齿的适当矿化对人类的正常生长发育包括肌肉骨骼功能具有重要意义。这些组织中的矿物相有助于结构的硬度和综合强度，也具有作为钙和镁代谢储存库的主要生理作用。矿化过程中的问题在许多骨骼病理中都很明显。矿化组织研究中最有趣的问题之一是，在生理环境中，循环中的钙、磷和其他矿物相离子如何集中在特定的、局部的器官或组织中。到目前为止，我们对启动和监管这一级联反应的过程几乎没有定义。然而，有机基质被认为在矿化过程中起着重要的调节作用。我们主要关注牙本质矿化，因为它是一个比骨更简单的系统，但这两种机制可能是密切相关的。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中，这些大分子负责成核并启动矿化级联反应。可能这些酸性大分子还调节碳酸化的羟基磷灰石晶体的大小。在寻找牙本质主要的酸性非胶原蛋白(NCP)的编码基因，即磷酸化蛋白(PP)的过程中，我们鉴定了两个克隆，一个代表磷酸化蛋白，现在命名为DMP2(牙本质基质蛋白2)，另一个DMP3(牙本质基质蛋白3)，它是牙本质涎蛋白和一个微小的“磷酸化蛋白”样结构域的复合体。从部分DMP2基因推导出的氨基酸序列具有特殊的意义，因为它清楚地代表了一种富含天冬氨酸和丝氨酸的酸性蛋白，该蛋白是牙本质基质成分的预期类型。该基因已被紧密定位于小鼠染色体5q21，相当于人类染色体4q21。为了扩大我们对DMP2基因结构和功能的了解，我们提出了下列特定目标：(1)确定大鼠DMP2的完整一级结构并确定DMP2启动子序列和参与组织特异性调控的元件(3)克隆人DMP2基因，以便最终确定DMP2基因在牙本质发育不全患者中的表达变化(4)研究DMP2在牙齿发育过程中的表达的时空模式(5)确定DMP2的钙结合性质。我们的长期目标是了解DMP2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.