Systematic in vivo analysis of Wnt secretory routes

Wnt糖蛋白家族是Wnt信号通路的配体，是多细胞动物胚胎发育过程中参与多种过程的生长因子。Wnt信号通路也在包括癌症在内的各种疾病中发挥关键作用。我们已经在人类细胞中进行了全基因组siRNA筛选，以鉴定Wnt信号传导所需的新型调节剂。我们利用合成的siRNA文库系统敲除约21，500个基因，并结合基于上位细胞的Wnt信号传导活性测定。上位性筛选之间的比较使我们能够鉴定出在Wnt信号级联的不同部分起作用的有限数量的基因。我们建议在这里描述少数相关的候选人，并通过在果蝇和非洲爪蟾的功能分析的增益和损失在体内表征它们。然后将对相关候选物进行详细的上位性和生物化学分析，以揭示其作用机制。一个特别的重点将是参与Wnt分泌（布特罗斯）和受体激活机制（尼尔斯）的基因。

The family of the Wnt glycoproteins, the ligands of the Wnt signaling pathway, are growth factors that are implicated in diverse processes during embryonic patterning in metazoans. The Wnt signaling pathway also plays key roles in various diseases, including cancer. We have conducted a genome-wide siRNA screen in human cells to identify novel regulators which are required for Wnt signaling. We made use of a synthetic siRNA library for the systematic knockdown of about 21,500 genes combined with epistatic cell-based assays for Wnt signaling activity. Comparisons between epistasis screens allowed us to identify a limited number of genes that act in different parts of the Wnt signaling cascade. We propose here to characterize a small number of relevant candidates and characterize them by in vivo by gain- and loss- of function analysis in both Drosophila as well as Xenopus. Relevant candidates will then be epistatically and biochemically analyzed in detail to unravel their mechanism of action. A particular focus will be on genes involved in Wnt secretion (Boutros) and mechanisms of receptor activation (Niehrs).