Biological mechanisms of developmental stem cell plasticity

干细胞是组织发育、维持和再生的重要驱动力。为了确保这些过程的完整性，干细胞在它们可以采用的分子身份和命运决定方面表现出可塑性，这必须受到仔细的控制。干细胞识别最好的特征是基因和蛋白质表达水平；尽管溶酶体等细胞细胞器整合了多种生物学过程，但人们对其影响知之甚少。溶酶体是细胞的“废物处理系统”--自噬--的公认效应者。我们对这个细胞器更广泛的功能的了解仍在展开，尽管最近出现了与影响细胞命运决定的过程的联系，包括代谢、表观遗传和细胞信号调节。因此，阐明溶酶体影响的干细胞群体和相应的机制将填补一个关键的知识空白，并为发现开辟新的途径。我最近发现，神经干细胞的最初特征是溶酶体突然激活，这在亲代多能干细胞或发育相关的神经脊细胞(NCC)中没有观察到。随后，随着NSC群体的扩张、成熟，并开始做出自我更新或分化的命运决定，NSC群体在溶酶体水平上表现出异质性。强迫溶酶体激活到高水平会导致NSC表型功能障碍和加速分化，这表明这是维持溶酶体含量适中的关键要求。因此，微调的溶酶体激活对NSC的身份规范和正常的谱系发育都是至关重要的。我和我的团队将测试这一假设，即溶酶体表达动态调节NSC身份的采用、维持和可塑性。我的研究计划的总体目标是阐明干细胞特性的关键生物调节因素及其对细胞命运可塑性的影响。在接下来的五年里，我的团队将利用我建立的二维(2D)多能和3D器官类干细胞模型系统，开始研究溶酶体在干细胞识别规范和谱系发育中的作用。小鼠胚胎外植体将提供二次验证。我们将重点关注神经干细胞和神经干细胞，但也将调查其他干细胞群体。目的：1.明确干细胞鉴定规范中对溶酶体的要求。2.阐明溶酶体激活对谱系发育的影响。3.探讨溶酶体影响干细胞命运的生物学机制。这项工作将增进有关溶酶体生物学以及控制干细胞身份和命运可塑性的过程的基本知识。它还将为翻译研究人员揭示易于处理的细胞因素，开发组织再生策略，并识别干细胞完整性与功能障碍的生物标记物。

Stem cells are essential drivers of tissue development, maintenance, and regeneration. To ensure integrity in these processes, stem cells exhibit plasticity in the molecular identities and fate decisions they can adopt, which must be carefully controlled. Stem cell identity is best characterized at the level of gene and protein expression; though the impact of cellular organelles like lysosomes, which integrate multiple biological processes, is poorly understood. Lysosomes are well-established effectors of autophagy, the cell's "waste disposal system". Our understanding of the wider breadth of function of this organelle is still unfolding, though links to processes that are known to impact cell fate decisions have recently emerged, including metabolic, epigenetic, and cell signaling regulation. Thus, elucidating the stem cell populations and corresponding mechanisms that lysosomes impact would fill a critical knowledge gap and open up new avenues for discovery. I recently discovered that the initial specification of NSCs is marked by a sudden activation of lysosomes, which is not observed in parental pluripotent stem cells or developmentally related neural crest cells (NCCs). Subsequently, NSC populations exhibit heterogeneity in lysosome levels as they expand, mature, and begin making fate decisions to self-renew or differentiate. Suggesting a critical requirement for maintenance of `moderate' lysosome content, forced lysosome activation to `high' levels leads to dysfunctional NSC phenotypes and accelerated differentiation. Finely tuned lysosome activation thus appears to be critical for both NSC identity specification and normal lineage development. My team and I will test the hypothesis that lysosome expression dynamics regulate the adoption, maintenance, and plasticity of NSC identity. The over-arching goal of my research program is to elucidate the critical biological regulators of stem cell identity and their impacts on cell fate plasticity. Over the next five years my team will begin to investigate the role of lysosomes in stem cell identity specification and lineage development, using my established two-dimensional (2D) pluripotent and 3D organoid stem cell model systems. Mouse embryo explants will provide secondary validation. We will focus on NSCs and NCCs, but additional stem cell populations will also be investigated. OBJECTIVES: 1. Define the requirement for lysosomes in stem cell identity specification. 2. Elucidate the impacts of lysosome activation on lineage development. 3. Investigate the biological mechanisms by which lysosomes impact stem cell fate. This work will advance basic knowledge on lysosome biology and the processes that control stem cell identity and fate plasticity. It will also reveal tractable cellular factors for translational researchers developing tissue regeneration strategies and identifying biomarkers of stem cell integrity versus dysfunction.