EGF receptor mediated signaling in Drosophila

描述（由申请人提供）：该研究项目研究在卵子发生过程中激活果蝇表皮生长因子受体（Egfr）的机制，以及介导卵巢卵泡细胞中对该受体酪氨酸激酶的反应的细胞途径。细胞间通讯在许多组织的发育中发挥着重要作用。我们的模型系统专注于果蝇卵巢中雌性种系与其周围卵泡细胞之间的信号传导。我们已经证明，果蝇 Egfr 在滤泡细胞中表达，并接收来自 gurken (grk) 基因编码的种系的高度控制信号。 Grk 对 Egfr 的有限激活会引发几种不同的卵泡细胞反应，并且是卵子和胚胎轴形成所必需的。我们还表明，卵子发生中的 grk 表达可以通过检查点机制进行调节。减数分裂过程中的 DNA 修复问题以及反转录转座子引起的其他核缺陷，会激活控制卵母细胞细胞质中 Grk 翻译的减数分裂检查点。我们的目标是研究种系中 Gurken 产生的调节，并分析毛囊细胞响应受体激活而激活的模式和分化过程。我们的具体目标是：1) 检查点介导的 Gurken 生产控制：1A) piRNAi 途径中截止 (cuff) 的作用。我们发现基因袖带是 piRNAi 途径的一个组成部分，可保护种系免受逆转录转座子损伤。袖带突变激活种系检查点。我们将确定 cuff 在 piRNAi 通路中的分子作用及其对检查点激活的影响。 1B) gurken RNA 的翻译调控。我们将确定减数分裂检查点如何调节 grk 的翻译。这将涉及对基因 vasa 以及影响检查点激活种系中 Grk 蛋白水平的翻译起始因子 eIF1A 的分析。 3）作用于卵巢卵泡细胞的反应途径分析。我们已经定义了滤泡细胞中 Egfr 激活的几种特定模式反应。特别是，我们分离出了影响后滤泡细胞分化的突变，并揭示了 Egfr 信号传导与 Notch 通路的相互作用。我们将分析两个基因的突变，这将使我们能够描述后滤泡细胞中两条通路的复杂相互作用。我们还将比较后滤泡细胞与背滤泡细胞的反应。检查点基因的突变以及人类 Egfr 同源物的不受调控的激活与多种癌症有关。我们的工作将阐明检查点基因的新作用，并分析调节该受体活性的正常细胞途径。它还将定义在滤泡细胞上皮（上皮发育和分化的模型系统）中运行的下游效应通路。

DESCRIPTION (provided by applicant): This research project investigates the mechanisms that activate the Drosophila Epidermal Growth Factor receptor (Egfr) during oogenesis, and the cellular pathways that mediate the response to this receptor tyrosine kinase in the ovarian follicle cells. Cell-cell communication plays an important role in the development of many tissues. Our model system focuses on signaling between the female germline and its surrounding follicle cells in the ovary of Drosophila melanogaster. We have shown that the Drosophila Egfr is expressed in the follicle cells and receives a highly controlled signal from the germline encoded by the gene gurken (grk). Restricted activation of the Egfr by Grk initiates several different follicle cell responses and is required for axis formation of the egg and embryo. We have also shown that grk expression in oogenesis can be regulated by a checkpoint mechanism. Problems in DNA repair during meiosis as well as other nuclear defects caused by retrotransposons, activate a meiotic checkpoint that controls translation of Grk in the oocyte cytoplasm. Our goal is to study the regulation of Gurken production in the germline and to analyze the patterning and differentiation processes that are activated in the follicle cells in response to receptor activation. Our specific aims are: 1) Checkpoint mediated control of Gurken production: 1A) The role of cutoff (cuff) in the piRNAi pathway. We have found that the gene cuff is a component of the piRNAi pathway that guards the germline against retrotransposon damage. Mutations in cuff activate a germline checkpoint. We will determine the molecular role of cuff in the piRNAi pathway and its effect on checkpoint activation. 1B) Translational regulation of gurken RNA. We will determine how the meiotic checkpoint regulates translation of grk. This will involve analysis of the gene vasa, as well as the translation initiation factor eIF1A that affects Grk protein levels in the checkpoint activated germline. 3) Analysis of the response pathway acting in the follicle cells of the ovary. We have defined several specific patterning responses to Egfr activation in the follicle cells. In particular, we have isolated mutations that affect posterior follicle cell differentiation and uncover interactions of Egfr signaling with the Notch pathway. We will analyze mutations in two genes that will allow us to describe the complex interactions of the two pathways in the posterior follicle cells. We will also compare the response of posterior follicle cells to that of dorsal follicle cells. Mutations in checkpoint genes, as well as unregulated activation of the human homologs of Egfr have been implicated in several forms of cancer. Our work will elucidate new roles of checkpoint genes, as well as analyzing the normal cellular pathways that regulate the activity of this receptor. It will also define downstream effector pathways operating in the follicle cell epithelium, a model system for epithelial development and differentiation.