European Molecular Biology Laboratory, Developmental Biology Unit, Heidelberg, Germany.
Department of Cell and Developmental Biology, University College London, London, UK.
EMBO J. 2021 Sep 15;40(18):e107245. doi: 10.15252/embj.2020107245. Epub 2021 Aug 16.
During embryonic development, signalling pathways orchestrate organogenesis by controlling tissue-specific gene expression programmes and differentiation. Although the molecular components of many common developmental signalling systems are known, our current understanding of how signalling inputs are translated into gene expression outputs in real-time is limited. Here we employ optogenetics to control the activation of Notch signalling during Drosophila embryogenesis with minute accuracy and follow target gene expression by quantitative live imaging. Light-induced nuclear translocation of the Notch Intracellular Domain (NICD) causes a rapid activation of target mRNA expression. However, target gene transcription gradually decays over time despite continuous photo-activation and nuclear NICD accumulation, indicating dynamic adaptation to the signalling input. Using mathematical modelling and molecular perturbations, we show that this adaptive transcriptional response fits to known motifs capable of generating near-perfect adaptation and can be best explained by state-dependent inactivation at the target cis-regulatory region. Taken together, our results reveal dynamic nuclear adaptation as a novel mechanism controlling Notch signalling output during tissue differentiation.
在胚胎发育过程中，信号通路通过控制组织特异性基因表达程序和分化来协调器官发生。尽管许多常见的发育信号系统的分子成分已经为人所知，但我们目前对信号输入如何实时转化为基因表达输出的理解还很有限。在这里，我们采用光遗传学技术，以分钟级的精度控制果蝇胚胎发育过程中 Notch 信号的激活，并通过定量活细胞成像来跟踪靶基因的表达。Notch 细胞内结构域（NICD）的光诱导核易位导致靶 mRNA 表达的快速激活。然而，尽管持续进行光激活和核 NICD 积累，靶基因转录仍随时间逐渐衰减，表明对信号输入的动态适应。通过数学建模和分子扰动，我们表明这种适应性转录反应符合能够产生近乎完美适应的已知基序，并且可以通过在靶顺式调控区的状态依赖性失活来最好地解释。总之，我们的结果揭示了动态核适应作为一种控制组织分化过程中 Notch 信号输出的新机制。
