小鼠Wntless（Wls）与果蝇等同源并特定调节Wnt蛋白分子的分泌过程。因而对牙胚上皮及间充质发育Wls功能的研究会反映出器官发育中Wnt分子的来源。利用Cre/Lox手段我们发现牙胚上皮失去Wls后牙齿形态发生不能进行，并伴随牙胚中Wnt信号水平下降。得到的设想是牙齿形态发生中功能性Wnt分子的来源于上皮组织，Wls通过对Wnt分子在分泌水平的调节实现对牙齿形态发生的控制。本项目拟从3方面验证上述可能性。1）利用分子原位杂交，抗体免疫组化,细胞活动等对上皮组织Wls条件敲除后牙齿缺陷形成机理分析阐明形态发生受阻与Wnt信号水平间的关系；2）利用体外蛋白质技术以及组织重组技术找出Wls与牙胚上皮表达Wnt分子的作用，并证明牙胚发育中Wnt配体的分泌依赖Wls 3）利用器官组织重组及Osr2基因敲除小鼠多齿遗传模型研究Wls突变胚胎牙胚组织的牙向诱导能力及对诱导的反应。

Mouse Wntless (Wls) encodes a multi-transmembrane protein that specifically regulates secretion of Wnt proteins. We could get insight into the tissue source of Wnt by studying the functional role of Wls in epithelial/mesenchymal organogenesis. In our preliminary study we discovered that, by means of Cre/Lox recombination system in mouse models, tooth development arrested prior to morphogenesis in the oral epithelial absence of mouse Wls protein; in which the Wnt/canonical signaling was dramatically down-regulated as well. These leads to our hypothesis that the functional Wnt source is the dental epithelium in tooth morphogenesis and, Wntless could governs the tooth morphogenesis through controls the secretion of Wnt protein in producing cell. We plan to test these possibilities by pursuing following experiments: 1) To elucidate the interaction between Wntless and epithelial expressed Wnt proteins through both in situ and in vitro protein approaches and define the requirement of Wntless for Wnt secretion in tooth germ development; 2) To explain the molecular mechanism of tooth morphogenetic arrest, in which Wntless was specifically deleted in oral epithelium, by in situ hybridization for RNA expression, immunohistochemistry for antibody staining, and cell activities in development of dental epithelium. (3). To detect the odontogenic inductive and competent potentials of oral epithelium in the absence of Wntless function, by means of tissue recombination and genetic approaches.