PDF(Pubmed)
Abstract：
Transcription control is a major determinant of cell fate decisions in somatic tissues. By contrast, early germline fate specification in numerous vertebrate and invertebrate species relies extensively on RNA-level regulation, exerted on asymmetrically inherited maternal supplies, with little-to-no zygotic transcription. However delayed, a maternal-to-zygotic transition is nevertheless poised to complete the deployment of pre-gametic programs in the germline. Here, we focus on early germline specification in the tunicate Ciona to study zygotic genome activation. We first demonstrate that a peculiar cellular remodeling event excludes localized postplasmic Pem-1 mRNA, which encodes the general inhibitor of transcription. Subsequently, zygotic transcription begins in Pem-1-negative primordial germ cells (PGCs), as revealed by histochemical detection of elongating RNA Polymerase II, and nascent Mef2 transcripts. In addition, we uncover a provisional antagonism between JAK and MEK/BMPRI/GSK3 signaling, which controls the onset of zygotic gene expression, following cellular remodeling of PGCs. We propose a 2-step model for the onset of zygotic transcription in the Ciona germline and discuss the significance of germ plasm dislocation and remodeling in the context of developmental fate specification.
摘要：
转录控制是体细胞组织中细胞命运决定的主要决定因素。相比之下,许多脊椎动物和无脊椎动物物种的早期种系命运规范广泛依赖于RNA水平的调节，施加于不对称遗传的母体供应，几乎没有合子转录。然而延迟，然而,从母体到合子的过渡已准备好完成种系中配子前计划的部署.这里,我们专注于被膜Ciona的早期种系规范，以研究合子基因组的激活。我们首先证明了一个特殊的细胞重塑事件排除了局部的后质Pem-1mRNA，它编码转录的一般抑制剂。随后，合子转录始于Pem-1阴性原始生殖细胞（PGCs），如延伸RNA聚合酶II的组织化学检测所示，和新生的Mef2成绩单。此外,我们发现JAK和MEK/BMPRI/GSK3信号之间的暂时拮抗作用，控制合子基因表达的开始，PGCs细胞重塑后。我们提出了Ciona种系中合子转录开始的两步模型，并讨论了在发育命运规范的背景下种质错位和重塑的重要性。
