Fat-Dachsous signaling in growth control and planar cell polarity

描述（由申请人提供）：本提案概述了一系列实验，旨在测试由Hippo和疣蛋白激酶介导的重要细胞内通路的调控，该通路用于控制发育生物体的生长、细胞死亡和模式。该途径在控制器官生长中起主要作用，并且该途径的错误调节是致瘤性的，但对其如何控制知之甚少。我们正在集中研究这一途径是如何被大型果蝇原钙粘蛋白Fat和Dachsous调节的。这两种跨膜蛋白的胞外结构域相互结合，通过激活Hippo通路抑制生长。然而，将Fat和Dachsous与Hippo通路联系起来的机制尚不清楚。首先，我们正在剖析脂肪细胞内结构域的活动，并利用它来开发脂肪活动所需分子的体外RNAi筛选。其次，我们正在研究脂肪和Dachsous表达的边界和梯度，以及由此产生的脂肪和Dachsous在细胞表面的极化，如何抑制Hippo通路并触发生长。第三，我们正在研究脂肪活性的下游负调节因子，非典型肌球蛋白Dachs/Myosin29D及其调节因子的作用。最后，我们正在研究Hippo通路如何结合其他（特别是空间）信息来调节重要的下游靶标miRNA bantam的表达。

DESCRIPTION (provided by applicant): This proposal outlines a series of experiments designed to test the regulation of an important intracellular pathway for controlling growth, cell death and patterning in developing organisms: that mediated by the Hippo and Warts protein kinases. This pathway plays a major role in controlling organ growth, and misregulation of the pathway is tumorigenic, but little is known about how it is controlled. We are concentrating on how this pathway is regulated by the large Drosophila protocadherins Fat and Dachsous. The extracellular domains of these two transmembrane proteins bind each other, and this suppresses growth by activating the Hippo pathway. However, the mechanisms connecting Fat and Dachsous to the Hippo pathway are poorly understood. First, we are dissecting the activities of the intracellular domains of Fat, and are using that to develop an in vitro RNAi screen for molecules required for Fat activity. Second, we are examining how boundaries and gradients of Fat and Dachsous expression, and the resultant polarization of Fat and Dachsous on cell surfaces, inhibits the Hippo pathway and triggers growth. Third, we are examining the role of a downstream negative regulator of Fat activity, the atypical myosin Dachs/Myosin29D, and its regulator Approximated. Finally, we are examining how the Hippo pathway combines with additional (especially spatial) information to regulate the expression of an important downstream target, the miRNA bantam. PUBLIC HEALTH RELEVANCE: The experiments test and refine our knowledge about how developing organisms precisely control their growth and patterning. Such precision is essential to normal human development, and failure in such precision underlies many pathologies, including genetic defects and cancers. The pathway being studied is an important means for controlling growth that is shared by humans and other organisms; it can be profitably examined in Drosophila because of Drosophila's genetic and molecular advantages, and the rigor and speed with which such studies can be performed.