Cell Fate Decisions in Epithelial Stem Cell Lineages

R35授予摘要 我的实验室对了解细胞分化是如何在连续的 更新上皮组织。这些组织的保守特征尚未完全了解和统一研究 跨实验系统包括一个灵活的利基结构，一个通常 具有显著的细胞可塑性，以及邻近干细胞谱系竞争利基的能力 入住率。为了了解组织的这些新特性，我们把重点放在了能够 用于研究细胞在天然、体内和细胞分辨率下的行为.我们的主要模型 系统是果蝇卵巢的卵泡上皮，我们最近将我们的研究扩展到 小鼠肠道上皮细胞。我们在过去十年中的贡献包括确定来源和 识别毛囊干细胞(FSC)利基配体，定义FSC的自我更新网络，描述新的 促进干细胞和子代细胞命运分离的机制，以及建立和使用 作为理解干细胞生态位竞争的模型。我们目前的研究是 调查三个相互关联的区域。首先，我们创建了一个果蝇卵巢的细胞图谱，它描述了 十多种已知和新的细胞类型的身份、位置和基因表达谱。这个项目有 提供了有用的新工具，使我们能够研究组织中细胞的谱系可塑性，并已 例如，他发现，在生理应激期间，利基细胞可以转化为干细胞。在……里面 此外，这些工具为我们提供了一个新的机会来研究动态的利基细胞群体如何能够 在不断变化的组织需求中保持稳定的FSCs池。第二，我们正在研究分子 管理干细胞利基竞争的机制。我们已经确定了一大类导致 对利基市场的过度竞争，我们正在使用遗传学、定量成像和数学建模来 理解选择一种血统而不是另一种血统的基础。我们亦已把这些研究扩展至 小鼠肠道上皮细胞，发现这一过程至少是部分保守的。第三，我们是 研究细胞内pH(Phi)在调节细胞命运决定中的作用。我们演示了Phi FSC谱系和小鼠胚胎干细胞在分化过程中都会增加，这 PHI的增加是分化所必需的。在未发表的研究中，我们发现了类似的要求 增加了小鼠肠道干细胞谱系中的phi。目前，我们正专注于了解Phi如何 调节细胞命运，重点是具有pKa的候选“pH感应器”蛋白，如β-catenin 在生理范围内。对于这些蛋白质来说，质子的获得或丢失的功能类似于翻译后 修饰，从而将pH动态与可能影响细胞命运的蛋白质活动的变化联系起来。通过研究 这些在特征良好的果蝇和小鼠上皮中的紧急特性，我们正在获得详细的 对正常组织动态平衡过程的洞察将为更好地理解 在衰老和疾病期间组织动态平衡是如何失效的。

R35 GRANT ABSTRACT My lab is broadly interested in understanding how cellular differentiation is controlled within a continuously renewing epithelial tissue. Conserved features of these tissues that are not fully understood and unify studies across experimental systems include a flexible niche structure, a “transit amplification” stage which typically has significant cellular plasticity, and the ability of neighboring stem cell lineages to compete for niche occupancy. To understand these emergent properties of tissues, we have focused on approaches that allow for the study of cell behaviors within the native, in vivo context in at cellular resolution. Our primary model system is the follicle epithelium of the Drosophila ovary, and we have recently extended our studies into the mouse intestinal epithelium. Our contributions over the past ten years include identifying the source and identity of the follicle stem cell (FSC) niche ligands, defining a self-renewal network for FSCs, describing new mechanisms that promote the segregation of stem cell and daughter cell fates, and the establishment and use of the FSC lineage as a model for understanding stem cell niche competition. Our current studies are investigating three interconnected areas. First, we created a cell atlas of the Drosophila ovary that describes the identity, position, and gene expression profile of over a dozen known and novel cell types. This project has provided useful new tools that are allowing us to investigate the lineage plasticity of cells in the tissue and has led, for example, to the discovery that niche cells can convert to stem cells during physiological stress. In addition, these tools provide us with a new opportunity to study how a dynamic population of niche cells is able to maintain a stable pool of FSCs amid changing tissue demands. Second, we are investigating the molecular mechanisms that govern stem cell niche competition. We have identified a broad class of alleles that cause hypercompetition for the niche, and we are using genetics, quantitative imaging, and mathematical modeling to understand the basis for selection of one lineage over another. We have also extended these studies into the mouse intestinal epithelium and found that the process is at least partially conserved. Third, we are investigating the role of intracellular pH (pHi) in regulating cell fate decisions. We demonstrated that pHi increases during differentiation in both the FSC lineage and mouse embryonic stem cells, and that this increase in pHi is necessary for differentiation. In unpublished studies, we discovered a similar requirement for increased pHi in the mouse intestinal stem cell lineage. Currently, we are focused on understanding how pHi regulates cell fate, with an emphasis on candidate “pH sensor” proteins, such as β-catenin, that have a pKa within the physiological range. For these proteins, the gain or loss of a proton functions like a post-translational modification, thus linking pH dynamics to changes in protein activities that may affect cell fate. By studying these emergent properties within well-characterized Drosophila and mouse epithelia, we are gaining detailed insights into the process of normal tissue homeostasis that will provide a foundation for a better understanding of how tissue homeostasis fails during aging and disease.