Expression of Type I Procollagen and Amelogenin Genes in Ectoderm-Derived Mineralized Tissue

外胚层衍生的硬组织如釉质、釉质样（由上皮细胞和外胚间充质细胞共同产生）和鹅膏分别在牙齿和鳞片上形成外部高度矿化层。胶原蛋白的存在使釉质与真正的釉质有明显的区别，但这两种组织之间的系统发育关系却知之甚少。然而，釉样胶原的细胞来源一直存在争议。考虑到这些因素，我们寻找胶原蛋白和釉原蛋白基因，并表征了釉样胶原蛋白的起源。已使用地高辛标记的合成寡核苷酸探针定位编码Ⅰ型前胶原α 1的信使RNA。使用抗地高辛抗体使探针-mRNA杂交体可视化。在口腔粘膜、结缔组织和软骨膜的成纤维细胞中检测到强烈的前胶原杂交信号。此外，阳性杂交信号也观察到成牙本质细胞的牙釉质基质形成过程中的urodele幼虫（Triturus pyrrhogaster）的牙胚。而在口腔黏膜上皮细胞包括内上皮细胞中均未检测到信号。提示成牙本质细胞合成釉样基质的Ⅰ型前胶原α 1。

Ectoderm-derived hard tissues such as enamel, enameloid(produced jointly by epithelial and ectomesenchymal cells) and ganoine form an external highly mineralized layer on the teeth and scales respectively. The presence of collagen in enameloid distinguishes it clearly from true enamels, but little is known about phylogenetic relationship between these two tissues. The cellular source of enameloid collagen, however, has been remained controversial. With these considerations in mind we searched for collagen and amelogenin genes and characterized the origin of enameloid collagen. Messenger RNA encoding procollagen α 1 type I have been localized using digoxigenin-labelled synthetic oligonucleotide probes. The probe-mRNA hybrides were visualized using an anti-digoxin antibodies. Intense hybridization signals for the procollagen were detected in the fibroblasts of the oral mucosa connective tissues and perichondrium. Further, the positive hybridization signals were also observed in odontoblasts of the tooth germs of the larval urodele (Triturus pyrrhogaster) during enameloid matix formation. But no signals were detected in the oral mucosa epithelial cells including inner epithelial cells. It is highly suggestive that odontoblasts synthesize procollagen α 1 type I of the enameloid matrix.