Cellular Mechanisms of Wingless/Wnt Signaling Activity

小行星9600539 Wnt基因家族编码分泌的生长因子样分子，其通过细胞间通讯调节细胞行为。Wnt-1在成年雌性小鼠乳腺中的不适当表达导致乳腺肿瘤或乳腺癌。Wnt-1在发育中的小鼠胚胎中的正常表达调节细胞增殖并指定细胞身份。该建议利用果蝇，果蝇，作为一个模型系统，研究Wnt基因作用的细胞机制。果蝇wingless（wg）基因与小鼠Wnt-1基因高度同源，并且执行影响发育期间细胞行为的类似信号传导功能。 果蝇强大的遗传系统揭示了wg在发育的不同时期指定胚胎模式的不同方面。这些时间上不同的信号活动是单独可变的Wg蛋白内，这表明信号蛋白的结构特征影响细胞反应。此外，Wg蛋白在细胞内和细胞间的分泌和转运似乎对Wg功能至关重要。不同的Wg信号传导活动的性质和细胞间Wg运输的作用将通过突变转基因在活胚胎中的定向表达进行检查。使用GAL 4-UAS二元表达系统，具有正常Wg信号传导活性的确定子集的突变Wg分子将在热休克启动子的控制下普遍表达，或在确定的结构域中表达。将评估胚胎模式和wg信号传导活性的分子标记物的表型后果，以确定观察到的不同Wg信号传导活性的细胞基础。 此外，在信号传导和转运过程中与Wg蛋白相互作用的分子将通过表征调节Wg信号传导功能的突变来鉴定。已经分离出一小部分修饰wg突变体表型的突变，并且几个突变显示出强烈暗示直接参与wg信号传导途径的特征。将对这些修饰突变进行遗传和分子表征，以确定其与Wg相互作用的性质。这两种方法，在遗传上易于处理的果蝇系统，将提供深入了解的细胞机制，通过Wg/Wnt分子指定细胞的命运和控制细胞增殖。

9600539 Bejsovec The Wnt gene family encode secreted growth factor-like molecules that regulate cell behavior through cell-cell communication. Inappropriate expression of Wnt-l in the mammary glands of adult female mice results in mammary tumors, or breast cancer. Normal expression of Wnt-1 in developing mouse embryos regulates cell proliferation and specifies cellular identities. This proposal exploits the fruitfly, Drosophila melanogaster, as a model system to study the cellular mechanisms of Wnt gene action. The Drosophila wingless (wg) gene is highly homologous to the mouse Wnt-1 gene and performs similar signaling functions that influence cell behavior during development. The powerful genetic system of Drosophila has revealed that wg specifies different aspects of embryonic pattern at different times during development. These temporally distinct signaling activities are separately mutable within the Wg protein, suggesting that structural features of the signaling protein influence the cellular response. Furthermore, secretion and transport of Wg protein within and between cells appears to be essential to Wg function. The nature of the distinct Wg signaling activities and the role of intercellular Wg transport will be examined through the directed expression of mutant transgenes in living embryos. Mutant Wg molecules that possess defined subsets of the normal Wg signaling activities will be expressed either ubiquitously, under the control of the heat shock promoter, or in defined domains, using the GAL4-UAS binary expression system. The phenotypic consequences on embryonic pattern and on molecular markers of wg signaling activity will be assessed to determine the cellular basis for the distinct Wg signaling activities observed. In addition, molecules that interact with Wg protein during signaling and transport will be identified by characterizing mutations that modulate wg signaling function. A small collection of mutations that modify the wg mutant phenotype have been isolated and several mutations show features that strongly suggest a direct involvement in the wg signaling pathway. These modifier mutations will be characterized genetically and molecularly to determine the nature of their interaction with Wg. These two approaches, in the genetically tractable Drosophila system, will provide insight into the cellular machinery through which Wg/Wnt molecules specify cell fate and control cell proliferation.