Control of cell number in developing retina

描述（由申请人提供）：成功开发功能性眼睛不仅需要细胞分化程序，指定各种视网膜细胞类型，还需要大小控制机制，决定视网膜中细胞的数量。我的实验室正在采用分子、遗传和生化的方法来了解决定视网膜细胞数量的分子机制。我的实验室最近利用果蝇复眼作为实验模型，发现了一个通过协调调节细胞增殖和细胞死亡来控制视网膜细胞数量的关键信号通路。该途径由三种通常负调控视网膜细胞数量的肿瘤抑制基因定义：hippo （hpo）、salvador （sav）和warts （wts）。Hpo是一种丝氨酸/苏氨酸激酶，结合并磷酸化Sav， Sav是一种含有WW和卷曲结构域的接头蛋白。Hpo和Sav之间的相互作用反过来增强了Hpo对Wts的激酶活性。该通路的失活导致细胞周期调节因子Cyclin E和细胞死亡抑制剂diap1的转录升高，从而导致增殖增加和细胞凋亡减少。此外，这一途径似乎在哺乳动物中起着进化保守的作用。为了进一步了解Hpo通路在视网膜大小控制中的功能和调控，我们提出了三个具体目标。在第一个具体目标中，我们将通过鉴定Hpo应答转录因子并分析其调节模式来确定Hpo通路调节diap1转录的分子机制。在第二个具体目标中，我们将确定Hpo信号转导途径的细胞机制。在第三个具体目标中，我们将使用生化，酵母双杂交和遗传方法来确定Hpo途径的其他组成部分。除了揭示眼睛发育的基本机制外，我们的研究对其他组织的发育也有普遍的意义。

DESCRIPTION (provided by applicant): Successful development of a functional eye requires not only cell-differentiation programs that specify various retina cell types, but also size-control mechanisms that determine the number of cells in the retina. My laboratory is taking molecular, genetic and biochemical approaches to understand the molecular mechanisms that specify retina cell number. Using the compound eye of Drosophila as an experimental model, my laboratory has recently identified a key signaling pathway that controls retina cell number by coordinately regulating cell proliferation and cell death. This pathway is defined by three tumor suppressor genes that normally negatively regulate retina cell number: hippo (hpo), salvador (sav) and warts (wts). Hpo, a Ser/Thr kinase, binds to and phosphorylates Sav, an adaptor protein containing WW and coiled-coil domains. Interactions between Hpo and Sav in turn potentiate the kinase activity of Hpo towards Wts. Inactivation of this pathway results in elevated transcription of the cell cycle regulator Cyclin E and the cell death inhibitor diap1, thus leading to increased proliferation and reduced apoptosis. Moreover, this pathway appears to play an evolutionarily conserved role in mammals. Here we propose three specific aims to further understand the function and regulation of the Hpo pathway in retina size-control. In the first specific aim, we will determine the molecular mechanisms by which the Hpo pathway regulates diap1 transcription by identifying the Hpo-responsive transcription factor and analyzing its mode of regulation. In the second specific aim, we will determine the cellular mechanism of the Hpo signal transduction pathway. In the third specific aim, we will use biochemical, yeast two-hybrid and genetic approaches to identify additional components of the Hpo pathway. Besides revealing basic mechanisms of eye development, our studies have general implications for the development of other tissues.