Christians E, Rao V H, Renard J P
Unité de Biologie du Développement, INRA, Jouy-en-Josas, France.
Dev Biol. 1994 Jul;164(1):160-72. doi: 10.1006/dbio.1994.1188.
Regulation of gene expression during early embryonic development in the rabbit was investigated by quantitative assay of firefly luciferase activity obtained by microinjection of three plasmid constructs using the regulatory region of polyomavirus promoter (PrPyV) with two different enhancer sequences (wild type or mutant "embryo-responsive," ER2) coupled to this reporter gene. Following injection at the 1-cell stage maximal level of expression of these genes was reached after three cell cycles. Two important regulatory steps that progressively limited gene expression were identified: the passage through the first mitosis and the transition from maternal to zygotic control of development (MZT) described at the 8- to 16-cell stage. The completion of the first mitosis was associated with the requirement of an enhancer sequence to stimulate expression of the weak PrPyV promoter while beyond the MZT, only particular enhancer sequences, such as ER2, allowed maintainance of the expression of PrPyV promoter. In addition, comparison of expression of constructs injected in pronuclei, 2-cell embryonic nuclei, and transplanted 32-cell blastomeres revealed that the nuclear environment could be a major effector in the regulation of embryonic gene expression. A schematic view is proposed describing the sequential establishment of the regulation exerted on early embryonic gene expression in progress from the onset of the zygotic genome activity to the MZT.
通过定量检测萤火虫荧光素酶活性，对兔早期胚胎发育过程中的基因表达调控进行了研究。该活性是通过显微注射三种质粒构建体获得的，这些构建体使用多瘤病毒启动子（PrPyV）的调控区域与两个不同的增强子序列（野生型或突变的“胚胎反应性”，ER2）连接到该报告基因上。在单细胞阶段注射后，这些基因在三个细胞周期后达到最大表达水平。确定了两个逐渐限制基因表达的重要调控步骤：通过第一次有丝分裂以及在8至16细胞阶段描述的从母体到合子发育控制（MZT）的转变。第一次有丝分裂的完成与刺激弱PrPyV启动子表达所需的增强子序列相关，而在MZT之后，只有特定的增强子序列，如ER2，才能维持PrPyV启动子的表达。此外，对注射到原核、2细胞胚胎核和移植的32细胞卵裂球中的构建体表达的比较表明，核环境可能是胚胎基因表达调控的主要效应因素。提出了一个示意图，描述了从合子基因组活性开始到MZT过程中对早期胚胎基因表达施加的调控的顺序建立。
