Dynamic regulation of anterior-posterior patterning genes in living Drosophila embryos
Dynamic regulation of anterior-posterior patterning genes in living Drosophila embryos
复制标题
DOI：
10.1016/j.cub.2021.02.050
复制
发表时间：
2021-05-24
期刊：
影响因子：
9.2
通讯作者：
Fukaya, Takashi
中科院分区：
文献类型：
--
作者：
Fukaya, Takashi
在果蝇胚胎发生过程中，gap和pair-rule基因的表达在机体分割中起着至关重要的作用。（1-5）然而，在单细胞水平上，这些关键发育基因的精确表达模式是如何从随机转录激活中产生的尚不清楚。在这里，我使用基因组编辑和实时成像方法来全面可视化内源位点上的gap和pair-rule基因的调控。定量图像分析显示，活性转录的总持续时间（转录周期）是早期胚胎基因表达空间模式的主要决定因素。转录周期的长短取决于单个细胞核中爆发活动的连续性，核心表达域比边界区域产生更多的爆发。在转录爆发期间，每个基因都表现出不同的新生RNA生产速率，这有助于基因到基因的总输出变异性。我还提供了“增强子干扰”的证据，其中远端弱增强子通过强近端增强子干扰转录激活，从而在不改变转录速率的情况下下调转录周期的长度。对内源性驼背（hb）基因座的分析表明，去除远端阴影增强子会诱导强烈的异位转录激活，从而抑制胚胎前部最初的宽表达域细化为更窄的条纹模式。这项研究为动物发育过程中转录爆发、增强子-启动子相互作用和基因表达时空模式之间的联系提供了关键见解。
Expression of the gap and pair-rule genes plays an essential role in body segmentation during Drosophila embryogenesis.(1-5) However, it remains unclear how precise expression patterns of these key developmental genes arise from stochastic transcriptional activation at the single-cell level. Here, I employed genome-editing and live-imaging approaches to comprehensively visualize regulation of the gap and pair-rule genes at the endogenous loci. Quantitative image analysis revealed that the total duration of active transcription (transcription period) is a major determinant of spatial patterning of gene expression in early embryos. The length of the transcription period is determined by the continuity of bursting activities in individual nuclei, with the core expression domain producing more bursts than boundary regions. Each gene exhibits a distinct rate of nascent RNA production during transcriptional bursting, which contributes to gene-to-gene variability in the total output. I also provide evidence for "enhancer interference," wherein a distal weak enhancer interferes with transcriptional activation by a strong proximal enhancer to downregulate the length of the transcription period without changing the transcription rate. Analysis of the endogenous hunchback (hb) locus revealed that the removal of the distal shadow enhancer induces strong ectopic transcriptional activation, which suppresses refinement of the initial broad expression domain into narrower stripe patterns at the anterior part of embryos. This study provides key insights into the link between transcriptional bursting, enhancer-promoter interaction, and spatiotemporal patterning of gene expression during animal development.