Control of Cell Number in Developing Retina

项目总结/摘要 我的长期科学目标是了解指定视网膜细胞数量的分子机制。使用 以果蝇的复眼为实验模型，我的实验室发现了海马通路 作为这一过程的核心机制。Hippo通路的核心包括激酶级联反应， 其中Ste20激酶Hippo（Hpo）磷酸化并激活NDR家族激酶Warts（Wts）。 反过来，Wts通过将癌蛋白Yorkie（Yki）从细胞核中排除而使其磷酸化和失活， 其中它通常作为DNA结合转录因子Scalloped（Sd）的共激活因子发挥作用。我们 研究进一步确定了Hippo途径在控制哺乳动物器官大小中的关键作用， 强调了果蝇作为一个强大的模型来发现普遍发展的重要性， 机制等 尽管最近的进展，我们的理解的组成，机制和调节Hippo信号转导 仍然不完整。我们最近的大部分努力都集中在发现 Hippo通路，最终目标是定义一个完整的Hippo信号网络。在目前的赠款中， 在此期间，我们已经填补了我们对Hippo途径的理解中的几个关键空白，包括一个功能链接， 在Hippo信号传导和先天免疫受体Toll之间，血影蛋白作为Hippo的上游调节剂 通过调节肌动球蛋白的信号传导，由STRIPAK磷酸酶介导的Hpo活性的自身抑制 复合物，一种与Hpo（一种募集的组蛋白甲基转移酶复合物）冗余发挥功能的Hpo样激酶 通过Yki激活Hippo靶基因的转录，以及通过Yki募集的锌指转录阻遏物。 Sd抑制Hippo靶基因的转录。我们进一步为河马研究社区做出了贡献 通过开发一套苍蝇种群，可以用来明确验证任何Hippo途径调节器， 严格的遗传上位性测试 在下一个资助期内，我们将进一步阐明Hippo途径的分子基础， 具体目标。首先，我们将剖析血影蛋白和 肌动球蛋白细胞骨架调节发育组织中的Hippo信号传导。其次，我们将确定上游 通过拮抗STRIPAK磷酸酶活性调节Hippo信号传导的肿瘤抑制剂 复杂.这些研究将使我们能够确定STRIPAK磷酸酶复合物如何作为一个中心的功能， Hippo是一个枢纽，将不同的上游输入整合到Hippo途径中。最后，我们将描述新的监管机构 从敏化筛选中分离出的Hippo信号传导的突变增强了Hippo表型的部分丧失 in the eye.这种不偏不倚的方法将揭示以前无法预见的监管机构/机制， 河马之路除了揭示眼睛发育的基本机制外，拟议的研究还将 对其他组织的发育有普遍的影响。

Project Summary / Abstract My long-term scientific goal is to understand the molecular mechanisms that specify retina cell number. Using the compound eye of Drosophila as an experimental model, my laboratory has discovered the Hippo pathway as a central mechanism underlying this process. The core of the Hippo pathway comprises a kinase cascade in which the Ste20 kinase Hippo (Hpo) phosphorylates and activates the NDR family kinase Warts (Wts). Wts, in turn, phosphorylates and inactivates the oncoprotein Yorkie (Yki) by excluding it from the nucleus, where it normally functions as a coactivator for the DNA-binding transcription factor Scalloped (Sd). Our research further established a critical role for the Hippo pathway in controlling organ size in mammals, underscoring the importance of Drosophila as a powerful model to discover universal developmental mechanisms. Despite recent progress, our understanding of the composition, mechanism and regulation of Hippo signaling remains incomplete. Much of our recent efforts have focused on discovering the missing components of the Hippo pathway, with the ultimate goal of defining a complete Hippo signaling network. In the current grant period, we have filled several key gaps in our understanding of the Hippo pathway, including a functional link between Hippo signaling and the innate immunity receptor Toll, spectrin as an upstream regulator of Hippo signaling by modulating actomyosin, autoinhibition of Hpo activity mediated by the STRIPAK phosphatase complex, a Hpo-like kinase that functions redundantly with Hpo, a histone methyltransferase complex recruited by Yki to activate the transcription of Hippo target genes, and a zinc finger transcriptional repressor recruited by Sd to repress the transcription of Hippo target genes. We further contributed to the Hippo research community by developing a set of fly stocks that can be used to unequivocally validate any Hippo pathway regulators through rigorous genetic epistasis test. In the next grant period, we will further elucidate the molecular underpinnings of the Hippo pathway through the following specific aims. First, we will dissect the molecular and cellular mechanisms by which spectrin and actomyosin cytoskeletons regulate Hippo signaling in developing tissues. Second, we will identify upstream tumor suppressors that regulate Hippo signaling by antagonizing the activity of the STRIPAK phosphatase complex. These studies will allow us to define how the STRIPAK phosphatase complex functions as a central hub that integrates diverse upstream inputs into the Hippo pathway. Lastly, we will characterize novel regulators of Hippo signaling isolated from a sensitized screen for mutations that enhance a partial loss-of-Hippo phenotype in the eye. This unbiased approach will shed light on previously unforeseen regulators/mechanisms underlying the Hippo pathway. Besides revealing fundamental mechanisms of eye development, the proposed studies will have general implications for the development of other tissues.