Molecular noise is a natural phenomenon that is inherent to all biological systems 1 , 2 . How stochastic processes give rise to the robust outcomes that support tissue homeostasis remains unclear. Here we use single-molecule RNA fluorescent in situ hybridization (smFISH) on mouse stem cells derived from haematopoietic tissue to measure the transcription dynamics of three key genes that encode transcription factors: PU.1 (also known as Spi1 ), Gata1 and Gata2 . We find that infrequent, stochastic bursts of transcription result in the co-expression of these antagonistic transcription factors in the majority of haematopoietic stem and progenitor cells. Moreover, by pairing smFISH with time-lapse microscopy and the analysis of pedigrees, we find that although individual stem-cell clones produce descendants that are in transcriptionally related states—akin to a transcriptional priming phenomenon—the underlying transition dynamics between states are best captured by stochastic and reversible models. As such, a stochastic process can produce cellular behaviours that may be incorrectly inferred to have arisen from deterministic dynamics. We propose a model whereby the intrinsic stochasticity of gene expression facilitates, rather than impedes, the concomitant maintenance of transcriptional plasticity and stem cell robustness. Single-molecule fluorescence in situ hybridization and live-cell imaging are used to study the contribution of transcriptional noise to stem cell heterogeneity, revealing that stochastic transcription dynamics are conducive to concomitant stem-cell maintenance and tissue homeostasis.

中文翻译：

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体干细胞转录动力学的单分子成像

分子噪声是一种自然现象，是所有生物系统 1、2 所固有的。随机过程如何产生支持组织稳态的稳健结果仍不清楚。在这里，我们在源自造血组织的小鼠干细胞上使用单分子 RNA 荧光原位杂交 (smFISH) 来测量编码转录因子的三个关键基因的转录动力学：PU.1（也称为 Spi1）、Gata1 和 Gata2。我们发现不常见的、随机的转录爆发导致这些拮抗转录因子在大多数造血干细胞和祖细胞中的共表达。此外，通过将 smFISH 与延时显微镜和谱系分析相结合，我们发现，尽管单个干细胞克隆产生的后代处于转录相关状态（类似于转录启动现象），但状态之间的潜在转变动态最好通过随机和可逆模型来捕捉。因此，随机过程可以产生细胞行为，这些行为可能被错误地推断为是由确定性动力学引起的。我们提出了一个模型，其中基因表达的内在随机性促进而不是阻碍转录可塑性和干细胞稳健性的伴随维持。单分子荧光原位杂交和活细胞成像用于研究转录噪声对干细胞异质性的贡献，