Homeostatic signaling in the Drosophila intestine

 描述（由申请人提供）：本提案旨在利用果蝇了解调节干细胞介导的肠组织稳态的机制。人体胃肠道（GI）中每天有数十亿个细胞脱落和更换。维持这种稳态的机制必须保持良好的平衡，而错误的调节将导致各种疾病，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稳态研究相当困难。类似于哺乳动物的肠道，果蝇中肠代表了由常驻干细胞维持的主动稳态系统。包括EGF、胰岛素、Wnt和JAK-STAT在内的进化上保守的途径调节中肠肠干细胞（ISCs）的组织生长。我们将研究中肠的两种主要上皮细胞类型， 成熟的肠上皮细胞和分化中的成肠细胞产生生长因子以调节ISC分裂并维持组织健康。具体目的1是研究Rab 11如何调节Upd 3在成熟肠上皮细胞中的表达以调节ISC分裂。Rab 11是一个小的GTdR，已知控制高尔基体和内体中的蛋白质运输。肠上皮细胞Rab 11功能的丧失导致显著的ISC增殖表型，伴随着JAK-STAT配体Upd 3表达的增加。此外，这种表型与Rab 11 a敲除后在小鼠肠上皮中观察到的表型非常相似。遗传和分子方法将用于确定连接Rab 11与Upd 3的途径。具体目标2是检查肠母细胞作为上皮小生境的一部分调节ISCs的功能。从肠母细胞特异性的试验RNAi筛选中，我们发现了与Warts-Yorkie相互作用以调节Upd 3表达的激酶Misshapen。这在哺乳动物细胞中作为MAP 4K 4-LATS-YAP途径是保守的。我们将详细分析这一途径和其他基因的功能，从遗传筛选，以建立肠母细胞也作为一个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，以产生最佳数量的生长因子，以维持肠道内稳态。所获得的结果应该为人类炎症性疾病，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.