Cell Fate Decisions in Epithelial Stem Cell Lineages

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争夺利基的能力。 为了了解组织的这些新特性，我们将重点放在允许研究 在细胞分辨率下，细胞在天然的体内环境中的行为.我们的主要模型系统是卵泡 果蝇卵巢上皮，我们最近将我们的研究扩展到小鼠的肠道 上皮组织。我们在过去十年中的贡献包括识别卵泡的来源和身份 干细胞(FSC)利基配体，定义了FSC的自我更新网络，描述了 促进干细胞和子细胞命运的分离，建立和使用FSC谱系 作为理解干细胞利基竞争的模型。我们目前的研究正在调查三个 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，它描述了果蝇卵巢的身份、位置、 以及十几种已知和新的细胞类型的基因表达谱。该项目提供了有用的新技术 这些工具使我们能够研究组织中细胞的谱系可塑性，并导致，例如 发现在生理压力下，壁龛细胞可以转化为干细胞。此外，这些工具还提供 我们有了一个新的机会来研究动态的利基细胞种群如何能够维持稳定的 在不断变化的组织需求中进行FSCS。第二，我们正在研究支配人类的分子机制 干细胞利基竞争。我们已经确定了一大类导致生态位过度竞争的等位基因， 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我们还将这些研究扩展到小鼠的肠道上皮 并发现这个过程至少是部分保守的。第三，我们正在研究细胞内pH的作用 (Phi)调节细胞命运的决定。我们证明了在分化过程中，FSC和FSC的phi升高。 这种PHI的增加是分化所必需的。在……里面 在未发表的研究中，我们发现在小鼠的肠道干细胞中也需要增加phi。 血统。目前，我们致力于了解phi是如何调控细胞命运的，重点是候选基因 “pH感应器”蛋白质，如β-连环蛋白，其pKa在生理范围内。对于这些蛋白质， 质子的获得或损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。通过研究这些新出现的特性， 果蝇和小鼠上皮，我们正在对正常组织动态平衡的过程有详细的了解 这将为更好地理解组织内稳在衰老和疾病期间如何失灵提供基础。

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.