Isolation and identification of cDNAs related with mouse tooth germs and its localization on human odontogenic tumor.

我们从小鼠胚胎(E13-E17)的牙胚和牙周组织中提取了cDNA，并用RT-PCR和差异显示技术比较了它们在各组织中的表达。从丙烯酰胺凝胶中洗脱的牙胚特异性cDNA的PCR产物是经紫外线辐射的胸腺嘧啶二聚物(T-T)。用每个T-T二聚化的cDNAs探针与小鼠胚胎(E14-17)的牙胚进行原位杂交，证实了cDNAs的特异性。用该方法分离了小鼠釉原蛋白基因，其编码区与人釉原蛋白的同源性为83%，并对人牙源性肿瘤：成釉细胞瘤(丛状型、滤泡型和混合型)、钙化牙源性肿瘤和牙骨质瘤进行了原位杂交。在丛状型和滤泡型成釉细胞瘤中均检测到成釉蛋白，而在钙化性牙源性肿瘤和牙骨质瘤中未检测到成釉蛋白，提示T-T二聚体基因探针原位杂交技术可用于筛选和分离新的组织特异性mRNA。

We isolated cDNAs from excised tooth germs and giniva of mouse embryo (E13-E17) and compared expression of cDNAs of each tissue by using RT-PCR and differential display. The eluted PCR products of tooth germ-spcecific cDNAs from acrylamide gels were thymine-thymine (T-T) dimerized by ultra violet irradiation. The specificity of the cDNAs were confirmed by in situ hybridization applied to tooth germs of mouse embryo (E14-17) by using the each T-T dimerized cDNA probe. By this method, we isolated mouse amelogenin cDNA and the coding region had 83% identity with human amelogenin.Moreover, we performed in situ hybridization for the same amelogenin cDNA probe on human odontogenic tumor : Ameloblastoma (plexiform type, follicular type and mixed type), Calcifying odon togenic tumor, and Cementoma. The amelogenin was detected on ameloblastoma both plexiform and follicular type but not calcifying odontogenic tumor and cementoma, because of previous decalcification by hydrochloric acid.These results reveals that the in situ hybridization using T-T dimerized cDNA probe were available for screening and isolation of novel tissue specific mRNA.