Immunohistochemical and molecular biological study of enamel proteins with special reference to molecular isoforms.

釉质蛋白，如淀粉原蛋白和鞘蛋白，有几种异构体是由mrna的选择性剪接产生的。为了阐明鞘蛋白分子同工型的作用，我们开发了能够识别特殊分子形式的区域特异性抗体。采用免疫化学和免疫组织化学方法对大鼠切牙和猪牙胚的牙釉质器官和未成熟牙釉质基质进行了分析。结果总结如下：1。对大鼠门牙釉质器官基质形成期和早期成熟期的免疫化学分析表明，大鼠鞘蛋白的两种同工异构体成釉细胞素和amelin分别合成为56 kDa和54 kDa核心蛋白。釉质器官中amelin和ameloblastin的含量在基质形成阶段差异不大，而在早期成熟阶段前者明显低于后者。大鼠门牙的免疫组化结果表明，成釉细胞蛋白和amelin的免疫定位基本相同。然而，由于釉基质中至深层的amelin免疫反应较弱，其降解速度似乎比成釉酶快。免疫组化分析发现，识别短型鞘蛋白（猪鞘蛋白）的抗体能清晰地染色全层的棱柱鞘。然而，用识别鞘鞘短型的抗体免疫染色后，表面层的棱柱鞘不那么清晰。在成熟期后期到成熟期早期，表层短型鞘鞘的免疫反应性明显弱于长型鞘鞘，说明短型鞘鞘的降解速度比长型鞘鞘快。

Enamel proteins, such as amelogenins and sheath proteins, have several isoforms produced by alternative splicing of mRNAs. In order to clarify the role of molecular isoforms of sheath proteins, we have developed region specific antibodies that can recognize special molecular forms. Enamel organ and immature enamel matrix from the rat incisor and the porcine tooth germ were analyzed by means of immunochemistry and immunohistochemistry. The results are summarized as follows.1. Immunochemical analysis of the enamel organ from the matrix formation stage and the early maturation stage in the rat incisor showed that ameloblastin and amelin, two isoforms of rat sheath proteins, were synthesized as 56 kDa and 54 kDa core proteins, respectively. The amount of amelin and ameloblastin contained in the enamel organ was not so different at the matrix formation stage, while the former was significantly lower than the latter at the early maturation stage.2. Immunohistochemistry of rat incisor has showed that immunolocalization of ameloblastin and amelin was essentially identical. However, the degradation of amelin seemed to be faster than that of ameloblastin because of weak immunoreaction of amelin at the middle to deep layer of enamel matrix.3. Immunohistochemical analysis of porcine immature enamel has revealed that antibody that recognize short-form of sheathlin (porcine sheath protein) clearly stained prism sheath at the entire layer. However, after the immunostaining with antibody that recognize short-form of sheathlin, prism sheath at the surface layer was not so clear.4. At the late transition to early maturation stages, immunoreactivity of the short-form of sheathlin at the surface layer was significantly weaker than that of the long-form of sheathlin, suggesting the degradation of short-form of sheathlin occurs faster than the long-form of sheathlin.