Control of cell number in developing retina

描述(申请人提供)：成功开发一只有功能的眼睛不仅需要指定各种视网膜细胞类型的细胞分化程序，还需要决定视网膜细胞数量的大小控制机制。我的实验室正在采用分子、遗传和生化方法来了解决定视网膜细胞数量的分子机制。以果蝇的复眼为实验模型，我的实验室最近发现了一条关键的信号通路，通过协调调节细胞增殖和细胞死亡来控制视网膜细胞的数量。这一途径由三个通常负向调节视网膜细胞数量的肿瘤抑制基因定义：河马(HPO)、萨尔瓦多(SAV)和疣(WTS)。HPO是一种丝氨酸/苏氨酸(Ser/Thr)激酶，它结合并磷酸化Sav，Sav是一种含有WW和螺旋卷曲结构域的接头蛋白。Hpo和Sav之间的相互作用反过来又增强了Hpo对WTS的激酶活性。这一途径的失活会导致细胞周期调节因子Cyclin E和细胞死亡抑制因子DIAP1转录水平升高，从而促进细胞增殖和减少细胞凋亡。此外，这一途径似乎在哺乳动物中扮演着进化上保守的角色。在这里，我们提出了三个具体的目标，以进一步了解HPO通路在视网膜大小控制中的功能和调节。在第一个特定目标中，我们将通过鉴定Hpo反应转录因子并分析其调控模式来确定Hpo途径调控DIAP1转录的分子机制。在第二个特定目标中，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鉴定HPO途径的其他成分。除了揭示眼睛发育的基本机制外，我们的研究还对其他组织的发育具有普遍意义。

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.