Modeling epithelial stem cell competition in a dynamic Drosophila ovarian niche

描述（由申请人提供）：本提案概述了定义果蝇卵巢中一种新型动态干细胞生态位的关键成分的策略，并阐明了生态位占有的竞争机制。实现本提案的目标将是一个重要的里程碑，朝着建立上皮干细胞调控的详细模型的长期目标，以开发基于再生医学的治疗方法，并了解调控过程如何在疾病状态（如癌症）中失败。产生滤泡上皮的卵泡干细胞（FSCs）具有许多与哺乳动物上皮祖细胞相同的特征，可能成为上皮干细胞生物学的优秀模型。像果蝇和哺乳动物中其他几种类型的上皮干细胞一样，FSCs在组织中稳定地维持，但似乎没有固定的、不分裂的小生境细胞群支持。相反，假设的生态位细胞在成年期分裂，并且随着周围生殖细胞囊肿在卵子发生过程中的移动，生态位的位置也发生了变化。此外，FSC子细胞有规律地在生态位之间迁移并争夺生态位，这一过程可能与正常上皮稳态和癌症早期阶段广泛相关。然而，这些假设的生态位细胞的身份以及介导干细胞维持和生态位竞争的机制尚不清楚。根据已发表的研究和重要的初步数据，该提案的中心假设是细胞粘附性和细胞极性的差异导致FSC和子细胞命运分化。具体目标包括：(1)鉴定动态FSC生态位细胞，确定其谱系，并测量其周转率；(2)阐明细胞粘附在FSC维持和FSC生态位竞争中的作用；(3)阐明细胞极性在FSC规范和子细胞命运中的作用。为了实现第一个目标，将使用细胞类型特异性标记，谱系分析和细胞周期标记来识别假定的生态位细胞并测量其周转率，结果将通过实时成像来证实。为了实现第二个和第三个目标，免疫荧光将用于鉴定在FSC生态位中表达的细胞粘附和细胞极性蛋白，而马赛克分析将用于确定它们在FSC维持和竞争中的功能。本课题为上皮干细胞生态位的研究建立了一个新的模型，具有重要的意义。这是对以往研究的创新背离，这些研究的重点是建立FSC生态位的综合模型，并理解动态生态位、生态位竞争和干细胞特异性极性的新概念。最终，它将为理解体内上皮干细胞调控的保守机制提供基础。

DESCRIPTION (provided by applicant): This proposal outlines a strategy for defining key components of a novel type of dynamic stem cell niche in the Drosophila ovary and for elucidating the mechanism of competition for niche occupancy. Accomplishing the aims in this proposal will be an important milestone toward the long-term goal of building a detailed model of epithelial stem cell regulation in order to develop regenerative medicine-based therapies and understand how the regulatory process fails in disease states such as cancer. The follicle stem cells (FSCs) that produce follicular epithelia have many features in common with mammalian epithelial progenitors and will likely be an excellent model for epithelial stem cell biology. Like several other types of epithelial stem cells in Drosophila and mammals, FSCs are stably maintained in the tissue but do not appear to be supported by a fixed, non- dividing niche cell population. Instead, putative niche cells divide during adulthood, and the position of the niche changes as surrounding germ cell cysts move through oogenesis. In addition, FSC daughters regularly migrate between niches and compete for niche occupancy in a process that may have broad relevance both to normal epithelial homeostasis and the early stages of cancer. However, the identity of the putative niche cells and the mechanisms that mediate stem cell maintenance and niche competition are unknown. Based on published studies and significant preliminary data, the central hypothesis of the proposal is that differences in cell adhesion and cell polarity cause FSC and daughter cell fates to diverge. Specific aims include: (1) Identifying the dynamic FSC niche cells, determining their lineage, and measuring their rate of turn over; (2) Elucidating the role of cell adhesion in FSC maintenance and FSC niche competition; and (3) Elucidating the role of cell polarity in the specification of FSC versus daughter cell fate. To achieve the first aim, cell-type-specific markers, lineage analysis, and cell cycle markers will be used to identify putative niche cells and measure their rate of turnover, and results will be confirmed with live imaging. To achieve the second and third aims, immunofluorescence will be used to identify cell adhesion and cell polarity proteins that are expressed in the FSC niche, and mosaic analysis will be used to determine their function in FSC maintenance and competition. This project is significant because it will establish a new model for the study of epithelial stem cell niches. It is an innovative departure from previous studies that focuses on building a comprehensive model of the FSC niche and on understanding the novel concepts of the dynamic niche, niche competition and stem cell-specific polarity. Ultimately, it will provide a foundation for understanding conserved mechanisms of in vivo epithelial stem cell regulation.