Department of Genetics, Yale University School of Medicine, New Haven, United States.
Institute for Quantitative Health Science & Engineering (IQ), Michigan State University, East Lansing, United States.
Elife. 2023 Mar 7;12:e83444. doi: 10.7554/eLife.83444.
Stem cell differentiation requires dramatic changes in gene expression and global remodeling of chromatin architecture. How and when chromatin remodels relative to the transcriptional, behavioral, and morphological changes during differentiation remain unclear, particularly in an intact tissue context. Here, we develop a quantitative pipeline which leverages fluorescently-tagged histones and longitudinal imaging to track large-scale chromatin compaction changes within individual cells in a live mouse. Applying this pipeline to epidermal stem cells, we reveal that cell-to-cell chromatin compaction heterogeneity within the stem cell compartment emerges independent of cell cycle status, and instead is reflective of differentiation status. Chromatin compaction state gradually transitions over days as differentiating cells exit the stem cell compartment. Moreover, establishing live imaging of () nascent RNA, which marks the onset of stem cell differentiation, we find that transcription is highly dynamic and largely precedes the global chromatin compaction changes associated with differentiation. Together, these analyses reveal that stem cell differentiation involves dynamic transcriptional states and gradual chromatin rearrangement.
干细胞分化需要基因表达的剧烈变化和染色质结构的全局重塑。染色质相对于转录、行为和形态变化的重塑方式和时间在分化过程中仍不清楚，特别是在完整组织环境中。在这里，我们开发了一种定量分析方法，该方法利用荧光标记的组蛋白和纵向成像来跟踪活体小鼠单个细胞内的大规模染色质压缩变化。将该方法应用于表皮干细胞，我们揭示了干细胞隔室内细胞间染色质压缩异质性的出现与细胞周期状态无关，而是反映了分化状态。随着分化细胞退出干细胞隔室，染色质压缩状态在数天内逐渐转变。此外，我们建立了新生 RNA 的活体成像，该 RNA 标记了干细胞分化的开始，我们发现转录是高度动态的，并且在很大程度上先于与分化相关的整体染色质压缩变化。总之，这些分析表明干细胞分化涉及动态转录状态和逐渐的染色质重排。
