Cell Fate Decisions in Epithelial Stem Cell Lineages

R35资助摘要 我的实验室对理解细胞分化是如何在一个连续的 更新上皮组织这些组织的保守特征尚未完全了解，并统一研究 跨实验系统包括一个灵活的利基结构，一个“过境放大”阶段，通常有 显着的细胞可塑性，以及邻近干细胞谱系竞争生态位占据的能力。 为了理解组织的这些新特性，我们集中研究了允许研究 在细胞分辨率下的天然的、体内环境中的细胞行为。我们的主要模型系统是毛囊 果蝇卵巢的上皮，我们最近将研究扩展到小鼠肠道 上皮我们在过去十年的贡献包括确定毛囊的来源和身份 干细胞（FSC）小生境配体，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，以及FSC谱系的建立和使用 作为理解干细胞生态位竞争的模型。我们目前的研究正在调查三个 相互关联的领域。首先，我们创建了果蝇卵巢的细胞图谱，描述了卵巢的身份，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 这些工具使我们能够研究组织中细胞的谱系可塑性，例如， 发现小生境细胞可以在生理应激过程中转化为干细胞。此外，这些工具还提供 我们有一个新的机会，研究如何动态种群的利基细胞是能够维持一个稳定的池， FSC满足不断变化的组织需求。第二，我们正在研究 干细胞生态位竞争我们已经确定了一大类等位基因，它们会导致生态位的过度竞争， 我们正在使用遗传学，定量成像和数学建模来了解 一个血统对另一个血统的选择。我们还将这些研究扩展到小鼠肠上皮细胞 发现这个过程至少部分是保守的。第三，我们正在研究细胞内pH值的作用， (pHi)调节细胞命运的决定。我们证明，在FSC和FSC的分化过程中，pHi增加， 谱系和小鼠胚胎干细胞，并且这种pHi的增加是分化所必需的。在 在一项未发表的研究中，我们发现了小鼠肠道干细胞中增加pHi的类似要求。 脉目前，我们的重点是了解pHi如何调节细胞命运，重点是候选细胞。 “pH传感器”蛋白，如β-连环蛋白，其具有生理范围内的pKa。对于这些蛋白质， 质子的获得或丢失功能类似于翻译后修饰，从而将pH动态与 蛋白质活性可能影响细胞命运。通过研究这些涌现的特性， 果蝇和小鼠上皮细胞，我们正在获得详细的了解正常组织稳态的过程 这将为更好地理解组织内稳态在衰老和疾病过程中如何失效提供基础。

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.