Zygotic genome activation has been extensively studied in a variety of systems including flies, frogs, and mammals. However, there is comparatively little known about the precise timing of gene induction during the earliest phases of embryogenesis. Here we used high-resolution in situ detection methods, along with genetic and experimental manipulations, to study the timing of zygotic activation in the simple model chordate Ciona with minute-scale temporal precision. We found that two Prdm1 homologs in Ciona are the earliest genes that respond to FGF signaling. We present evidence for a FGF timing mechanism that is driven by ERK-mediated derepression of the ERF repressor. Depletion of ERF results in ectopic activation of FGF target genes throughout the embryo. A highlight of this timer is the sharp transition in FGF responsiveness between the eight- and 16-cell stages of development. We propose that this timer is an innovation of chordates that is also used by vertebrates.

中文翻译：

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用于合子基因组激活的 FGF 计时器

合子基因组激活已在包括果蝇、青蛙和哺乳动物在内的多种系统中得到广泛研究。然而，对于胚胎发生最早阶段基因诱导的精确时间知之甚少。在这里，我们使用高分辨率原位检测方法以及遗传和实验操作，以分钟尺度的时间精度研究简单模型脊索动物Ciona中合子激活的时间。我们发现Ciona中的两个Prdm1同源物是最早响应 FGF 信号传导的基因。我们提出了 FGF 计时机制的证据，该机制是由 ERK 介导的 ERF 阻遏物去抑制驱动的。ERF 的消耗导致整个胚胎中 FGF 靶基因的异位激活。该计时器的一个亮点是 FGF 响应性在 8 细胞和 16 细胞发育阶段之间的急剧转变。我们认为这个计时器是脊索动物的创新，也被脊椎动物使用。