Establishment of spatial coordinates during Drosophila embryogenesis relies on differential regulatory activity of axis patterning enhancers. Concentration gradients of activator and repressor transcription factors (TFs) provide positional information to each enhancer, which in turn promotes transcription of a target gene in a specific spatial pattern. However, the interplay between an enhancer regulatory activity and its accessibility as determined by local chromatin organization is not well understood. We profiled chromatin accessibility with ATAC-seq in narrow, genetically tagged domains along the antero-posterior axis in the Drosophila blastoderm. We demonstrate that one-quarter of the accessible genome displays significant regional variation in its ATAC-seq signal immediately after zygotic genome activation. Axis patterning enhancers are enriched among the most variable intervals, and their accessibility changes correlate with their regulatory activity. In an embryonic domain where an enhancer receives a net activating TF input and promotes transcription, it displays elevated accessibility in comparison to a domain where it receives a net repressive input. We propose that differential accessibility is a signature of patterning cis-regulatory elements in the Drosophila blastoderm and discuss potential mechanisms by which accessibility of enhancers may be modulated by activator and repressor TFs.

中文翻译：

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ATAC-seq在果蝇胚盘空间坐标的建立过程中揭示了增强子可及性方面的区域差异。

果蝇胚胎发生过程中空间坐标的建立依赖于轴模式增强剂的不同调节活性。激活子和阻遏物转录因子（TFs）的浓度梯度可为每个增强子提供位置信息，从而促进特定基因模式下靶基因的转录。然而，由局部染色质组织确定的增强子调节活性与其可及性之间的相互作用尚不清楚。我们在果蝇胚盘中沿前后轴在狭窄的，带有基因标记的域中使用ATAC-seq进行染色质可及性分析。我们证明，合子基因组激活后，四分之一的可访问基因组在其ATAC-seq信号中立即显示出明显的区域变化。轴构图增强剂在变化最大的间隔中富集，其可及性变化与其调节活性相关。在其中增强子接收净激活的TF输入并促进转录的胚胎域中，与接收净抑制输入的域相比，增强子显示出提高的可及性。我们提出，差异可及性是果蝇胚盘中顺式调控元件模式化的标志，并讨论了通过激活剂和阻遏物TF调节增强剂可及性的潜在机制。与它收到净压制性输入的域相比，它显示出更高的可访问性。我们提出，差异可及性是果蝇胚盘中顺式调控元件模式化的标志，并讨论了通过激活剂和阻遏物TF调节增强剂可及性的潜在机制。与它收到净压制性输入的域相比，它显示出更高的可访问性。我们提出，差异可及性是果蝇胚盘中顺式调控元件模式化的标志，并讨论了通过激活剂和阻遏物TF调节增强剂可及性的潜在机制。