Homeostatic signaling in the Drosophila intestine

 描述(申请人提供)：这项建议旨在利用果蝇来了解调节干细胞介导的肠道组织稳态的机制。人类胃肠道(GI)中的数十亿细胞每天都在脱落和更换。维持这种动态平衡的机制必须得到很好的平衡，调节不当将导致各种疾病，包括组织损伤、炎症和癌症。人类胃肠道的大小和复杂性使得涉及多种细胞类型和调节途径的动态平衡的研究相当困难。与哺乳动物的肠道相似，果蝇中肠代表着一个由常驻干细胞维持的活跃的动态平衡系统。进化上保守的途径包括EGF、Insulin、Wnt和JAK-STAT调节中肠干细胞(ISCs)的组织生长。我们将研究中肠的两种主要上皮细胞类型， 成熟的肠细胞和分化的肠母细胞，产生生长因子来调节ISC的分裂和维持组织健康。具体目的1是研究Rab11如何调节成熟肠细胞中Upd3的表达，以调节ISC分裂。Rab11是一种小的GTP酶，已知控制高尔基体和内体中的蛋白质运输。肠细胞中Rab11功能的丧失会导致显著的ISC增殖表型，伴随着JAK-STAT配体Upd3的表达增加。此外，这种表型与在Rab11a基因敲除后观察到的小鼠肠上皮细胞中观察到的非常相似。遗传和分子方法将被用来确定连接Rab11和Upd3的途径。具体目标2是研究肠成纤维细胞作为上皮细胞生态位的一部分来调节ISCs的功能。从肠成纤维细胞特异的先导RNAi筛选中，我们发现了与疣-约克病毒相互作用的激酶畸形，以调节Upd3的表达。这在哺乳动物细胞中作为MAP4K4-LATS-YAP通路保守。我们将从基因筛选的角度详细分析这一途径和其他基因的功能，以确定肠成纤维细胞也是一种重要的生态位细胞类型。我们的长期目标是了解上皮细胞之间的协调，以产生最适量的生长因子来维持肠道内环境的稳定。所获得的结果将为人类炎症性疾病、衰老和癌症的治疗策略提供重要的见解。

 DESCRIPTION (provided by applicant): This proposal aims at using Drosophila to understand the mechanisms that regulate stem-cell-mediated intestinal tissue homeostasis. Billions of cells in the human gastrointestinal (GI) tract are shed and replaced every day. The mechanisms that maintain this homeostasis must be balanced well, and mis-regulation will lead to various diseases including tissue damage, inflammation and cancer. The size and complexity of the human GI tract renders the studying of homeostasis involving multiple cell types and regulatory pathways rather difficult. Similar to the mammalian intestine, the Drosophila midgut represents an active homeostatic system maintained by resident stem cells. Evolutionarily conserved pathways including EGF, Insulin, Wnt, and JAK-STAT regulate midgut intestinal stem cells (ISCs) for tissue growth. We will investigate how the two main epithelial cell types in the midgut, mature enterocytes and differentiating enteroblasts, produce growth factors to modulate ISC division and maintain tissue wellness. The specific aim 1 is to investigate how Rab11 regulates Upd3 expression in mature enterocytes to modulate ISC division. Rab11 is a small GTPase known to control protein trafficking in Golgi and endosomes. Loss of Rab11 function in enterocytes causes a prominent ISC proliferation phenotype, concomitant with an increased expression of the JAK-STAT ligand Upd3. Moreover, this phenotype is very similar to that observed in mouse intestinal epithelium after Rab11a knockout. Genetic and molecular approaches will be used to identify the pathway that connects Rab11 with Upd3. The specific aim 2 is to examine the function of enteroblasts as part of the epithelial niche to regulate ISCs. From an enteroblast-specific pilot RNAi screen we have uncovered the kinase Misshapen interacting with Warts-Yorkie to regulate Upd3 expression. This is conserved in mammalian cells as the MAP4K4-LATS-YAP pathway. We will analyze in detail this pathway and the function of other genes from the genetic screen to establish that enteroblasts also act as an important niche cell type. Our long-term goal is to understand the coordination among epithelial cells to produce the optimal amount of growth factors for intestinal homeostasis. The results obtained should provide important insights into therapeutic strategies for human inflammatory diseases, aging and cancer.