Wang Xinping, Ito Yoshihiro, Luan Xianghong, Yamane Akira, Diekwisch Thomas G H
Department of Oral Biology and Allan G. Brodie Laboratory for Craniofacial Genetics, College of Dentistry, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
J Exp Zool B Mol Dev Evol. 2005 Mar 15;304(2):177-86. doi: 10.1002/jez.b.21035.
The amelogenin gene contributes the majority of tooth enamel proteins and plays a significant role in enamel biomineralization. While several mammalian and reptilian amelogenins have been cloned and sequenced, basal vertebrate amelogenin evolution remains to be understood. In order to start elucidating the structure and function of amelogenins in the evolution of enamel, the leopard frog (Rana pipiens) was used as a model. Tissues from Rana pipiens teeth were analyzed for enamel structure and RNA extracts were processed for sequence analysis. Electron microscopy revealed that Rana pipiens enamel contains long and parallel crystals similar to mammalian enamel, while immunoreactions confirmed the site-specific localization of cross-reactive amelogenins in Rana pipiens enamel. Sequencing of amelogenin PCR products revealed a 782bp cDNA with a 546-nucleotide coding sequence encoding 181 amino acids. The homology of the newly discovered Rana pipiens amelogenin nucleotide and amino acid sequence with the published mouse amelogenin was 38.6% and 45%, respectively. These findings report the first complete amelogenin cDNA sequence in amphibians and indicate a close homology between mammalian enamel formation and Rana pipiens enamel biomineralization.
釉原蛋白基因贡献了大部分牙釉质蛋白，并在釉质生物矿化过程中发挥着重要作用。虽然几种哺乳动物和爬行动物的釉原蛋白已被克隆和测序，但基础脊椎动物釉原蛋白的进化仍有待了解。为了开始阐明釉原蛋白在釉质进化中的结构和功能，豹蛙（北美豹蛙）被用作模型。对北美豹蛙牙齿组织进行了釉质结构分析，并对RNA提取物进行了序列分析。电子显微镜显示，北美豹蛙的釉质含有与哺乳动物釉质相似的长而平行的晶体，而免疫反应证实了交叉反应性釉原蛋白在北美豹蛙釉质中的位点特异性定位。釉原蛋白PCR产物的测序显示，一个782bp的cDNA具有一个546个核苷酸的编码序列，编码181个氨基酸。新发现的北美豹蛙釉原蛋白核苷酸和氨基酸序列与已发表的小鼠釉原蛋白的同源性分别为38.6%和45%。这些发现报道了两栖动物中首个完整的釉原蛋白cDNA序列，并表明哺乳动物釉质形成与北美豹蛙釉质生物矿化之间存在密切的同源性。
