Notch signaling and fkh cooperate to maintain intestinal stem cells in Drosophila

 描述(申请人提供)：最近的报告已经确定了一个转录网络，它指定了胚胎干细胞的命运，促进了将体细胞重新编程为多能干细胞的突破性发展。此外，越来越多的证据表明，成熟细胞的身份也是由转录网络决定的。然而，决定成体干细胞命运的转录网络在很大程度上还没有确定，主要是因为调控体细胞干细胞命运的转录因子尚不清楚。在这项研究中，我们假设转录网络决定了果蝇成年中肠(肠)中肠干细胞(ISC)的命运。我们建议确定这些关键的ISC转录调控因子，以建立一个全面的干细胞转录网络，管理苍蝇ISC的命运。在我们的初步研究中，利用一只强壮的苍蝇 在肠道再生模型中，我们进行了RNAi筛选，以确定中肠再生所需的转录因子。我们已经鉴定了几种转录因子，包括da(E蛋白)、fkh(FoxA)、Klu和dSox9。具体地说，我们证明了这些转录因子在中肠祖细胞中的丢失导致了它们在中肠中的异位分化。此外，我们的遗传和分子研究表明，fkh和da共同诱导包括dSox9和klu在内的下游基因来决定ISC的命运。在此基础上，我们假设这些转录因子可能作为ISC转录网络发挥作用，我们打算在本研究中详细阐述这一点。首先，我们建议确定两个关键的ISC转录因子Fkh和Da如何通过确定它们的下游转录因子靶点来协同维持ISCs。其次，我们建议建立一个指定果蝇ISC细胞命运的ISC转录网络。第三，我们提出了小生境信号如何调节ISC转录网络以促进中肠祖细胞分化的机制。建立一个全面的肠道干细胞转录网络将有助于准确鉴定其下游干细胞基因，以便进行前所未有的功能分析，以揭示潜在的干细胞新功能。

 DESCRIPTION (provided by applicant): Recent reports have identified a transcriptional network that specifies the embryonic stem cell fate, which facilitated the breakthrough development of reprogramming somatic cells into pluripotent stem cells. Furthermore, increasing evidences suggest that the identities of mature cells are also defined by transcriptional networks. However, the transcriptional networks that specify adult stem cell fates are largely uncharacterized, mainly because the transcription factors regulating somatic stem cell fates are unknown. In this study, we hypothesize that a transcriptional network specifies the intestinal stem cell (ISC) fate in Drosophila adult midgut (intestine). We propose to identify thes critical ISC transcriptional regulators to establish a comprehensive stem cell transcriptional network that governs the fly ISC fate. In our preliminary studies, taking advantage of a robust fly gut regeneration model, we performed an RNAi screen to identify transcription factors required for midgut regeneration. We have characterized several transcription factor hits, including da (E-protein), fkh (FoxA), klu and dSox9. Specifically, we showed that loss of these transcriptional factors in the midgut progenitors leads to their ectopic differentiation in the midgut. Furthermore our genetic and molecular studies indicate that fkh and da collaborate to induce downstream genes including dSox9 and klu to specify the ISC fate. Based on that, we hypothesize that these transcription factors likely function as an ISC transcriptional network, which we aim to elaborate in this study. First, we propose to determine how two critical ISC transcription factors Fkh and Da collaborate to maintain ISCs by identifying their downstream transcription factor targets. Second, we propose to establish an ISC transcriptional network that specifies the fly ISC cell fate. Third, we propose to explore the mechanism how niche signals regulate the ISC transcriptional network to promote the differentiation of midgut progenitors. The establishment of a comprehensive intestinal stem cell transcriptional network will facilitate the accurate identification of its downstream stem cell genes to allow for the unprecedented functional analysis in order to uncover potential novel stem cell functions.