White Shane N, Paine Michael L, Ngan Amanda Y W, Miklus Vetea G, Luo Wen, Wang HongJun, Snead Malcolm L
School of Dentistry, University of California at Los Angeles, Los Angeles, California 90095, USA.
J Biol Chem. 2007 Feb 23;282(8):5340-5. doi: 10.1074/jbc.M604814200. Epub 2006 Dec 22.
Dentin sialophosphpoprotein (Dspp) is transiently expressed in the early stage of secretory ameloblasts. The secretion of ameloblast-derived Dspp is short-lived, correlates to the establishment of the dentinoenamel junction (DEJ), and is consistent with Dspp having a role in producing the specialized first-formed harder enamel adjacent to the DEJ. Crack diffusion by branching and dissipation within this specialized first-formed enamel close to the DEJ prevents catastrophic interfacial damage and tooth failure. Once Dspp is secreted, it is subjected to proteolytic cleavage that results in two distinct proteins referred to as dentin sialoprotein (Dsp) and dentin phosphoprotein (Dpp). The purpose of this study was to investigate the biological and mechanical contribution of Dsp and Dpp to enamel formation. Transgenic mice were engineered to overexpress either Dsp or Dpp in their enamel organs. The mechanical properties (hardness and toughness) of the mature enamel of transgenic mice were compared with genetically matched and age-matched nontransgenic animals. Dsp and Dpp contributions to enamel formation greatly differed. The inclusion of Dsp in bulk enamel significantly and uniformly increased enamel hardness (20%), whereas the inclusion of Dpp weakened the bulk enamel. Thus, Dsp appears to make a unique contribution to the physical properties of the DEJ. Dsp transgenic animals have been engineered with superior enamel mechanical properties.
牙本质涎磷蛋白（Dspp）在分泌期成釉细胞早期短暂表达。成釉细胞源性Dspp的分泌是短暂的，与釉牙本质界（DEJ）的形成相关，并且与Dspp在产生紧邻DEJ的特化的最先形成的较硬釉质中发挥作用相一致。在靠近DEJ的这种特化的最先形成的釉质内，裂纹通过分支和消散进行扩散，可防止灾难性的界面损伤和牙齿损坏。一旦Dspp分泌出来，它就会受到蛋白水解切割，产生两种不同的蛋白质，即牙本质涎蛋白（Dsp）和牙本质磷蛋白（Dpp）。本研究的目的是探讨Dsp和Dpp对釉质形成的生物学和力学贡献。构建了在其釉器中过表达Dsp或Dpp的转基因小鼠。将转基因小鼠成熟釉质的力学性能（硬度和韧性）与基因匹配和年龄匹配的非转基因动物进行比较。Dsp和Dpp对釉质形成的贡献差异很大。在整块釉质中加入Dsp显著且均匀地提高了釉质硬度（20%），而加入Dpp则削弱了整块釉质。因此，Dsp似乎对DEJ的物理性质有独特的贡献。已构建出具有优异釉质力学性能的Dsp转基因动物。
