Mapping the Trajectory of Cell Fate Transitions

描述（由申请人提供）：能够显著再生的生物体保持具有灵活性或可塑性的成体细胞，以改变其命运。这一特点使他们能够建立替代部件，如器官或肢体，从损伤或疾病中恢复。该项目先前的工作和其他研究揭示了特化细胞显示干细胞某些特性的广泛倾向;它们会对损伤做出反应，产生新的细胞类型。细胞在从一种命运到另一种命运的转变过程中所经历的动态变化可以揭示细胞用来使它们能够改变命运的机制。这些见解将揭示细胞可塑性的基本特征，从而可以改善人类细胞的再生治疗。然而，由于在分析体内再生细胞的整体状态方面的局限性， 知道细胞如何从一个状态到另一个状态的遍历。 该实验计划旨在提供细胞在再生过程中过渡到新命运的全面视图。这项研究利用植物，因为模型系统提供了一个难得的机会来模拟细胞可塑性。此外，调节可塑性的机制在植物和动物中得到了很好的保护，植物熟练的再生能力将说明细胞改变其身份的全部潜力。该提案利用了一个强大的模型系统，允许再生组织的连续成像和分析单细胞的转录内容，因为它们穿越命运。该系统包括每个细胞命运的活性基因清单，允许定量分析跟踪细胞再生时的复杂身份。因此，完整的分析将生成再生细胞轨迹的模型，以解决有关再生的基本问题：参与再生的高度可塑性细胞的起源是什么？再生细胞是否表现出类似干细胞的增殖行为？命运的转变是否需要失去所有的身份，达到一个“基础”状态或更年轻的发展阶段（去分化）？或者，细胞直接穿越到新的命运？ 结果将指向可以有针对性地使再生更有效的过程。分析细胞的完整转录动力学并将其投影到再生组织的图像上的创新广泛适用于许多发育模型系统。因此，总体而言，拟议的工作对再生领域产生了广泛的影响。

DESCRIPTION (provided by applicant): Organisms capable of dramatic regeneration maintain adult cells that have the flexibility, or plasticity, to change their fate. This feature enables thm build replacement parts, like organs or limbs, to recover from damage or disease. Previous work on the project and other studies have revealed a broad propensity for specialized cells to display some properties of stem cells; they give rise to new cell types in response to injury. The dynamic changes that cells undergo during the transition from one fate to another could reveal the mechanisms that cells employ to enable them to switch their fates. Such insights will reveal basic features of cellular plasticity that could improve regeneration therapy in human cells. However, due to limitations in analyzing the global status of regenerating cells in vivo, little is known about how cells make the traversal from one state to another. The experimental plan proposes to provide a comprehensive view of cells as they transition to new fates during regeneration. The study utilizes plants because the model system provides a rare opportunity to model cellular plasticity. In addition, the mechanisms that regulate plasticity are well conserved across plants and animals and the plant's adept ability to regenerate will illustrate the full potential of cells to change their identity. The proposal takes advantage of a powerful model system that permits continual imaging of regenerating tissue and the analysis of the transcriptional contents of single cells as they traverse fates. This system includes an inventory of active genes for each cell fate, permitting quantitative analyses to track the complex identity of cells as they regenerate. Thus, the complete analysis will generate a model of the trajectory of regenerating cells in order to address basic questions about regeneration: What is the origin of the highly plastic cells that participate in regeneration? Do regenerating cells show proliferative behavior that resembles stem cells? Do fate transitions require losing all identity and reaching a "ground" state or younger developmental stage (dedifferentiation)? Or, do cells traverse directly to new fates? The results will point to processes that can be targeted to make regeneration more efficient. The innovation of profiling the complete transcriptional dynamics of cells and projecting them onto images of regenerating tissue is widely applicable to many developmental model systems. Thus, overall, the proposed work has broad impact on the field of regeneration.