Gene expression in early mouse embryo and its regulation

在各种物种的早期胚胎发生过程中，母体RNA向合子RNA的转变被认为在发育后期的分子编程中起着重要作用。我们首先在小鼠中发现，我们实验室首次分离的一种称为“ssc - d（阶段特异性胚胎克隆- d）”的母体RNA在受精后18h（对应于1细胞后期）表现出poly(a)链在3'端短暂延伸的峰值，此后poly(a)链逐渐降解。基于这一发现，我们在过去三年中对这一现象进行了更详细的研究，并获得了以下几点发现。ssc - d RNA的瞬间大小增加是由于在其3'端增加了poly (A)链，这需要新的蛋白质合成。2. 由于mRNA检测系统的改进，可以使用10-20个受精卵和早期胚胎进行Northern blot分析。3. 体外合成的含有EGFP cDNA的RNA连接到ssc - d RNA的不同大小的3'-非编码区，在细胞质注射实验后，在受精卵中也观察到RNA的瞬时延伸。因此，这种现象已经被编程了。4. 添加跨越300-400个核苷酸的poly(A)可以释放母体RNA本身的翻译抑制状态。5. 这种poly(A)延伸依赖于ssc - d RNA本身的序列及其3'端区域的poly(A)序列。6. 通过提高受精卵对生物素标记ATP的吸收，可以浓缩含有母体rna的cdna。

In early embryogenesis of various species, there is a transition of matemal RNA to zygotic RNA, which is thought to play an important role in molecular programming of later stage of development. We first found in mice that one type of maternal RNA, which was first isolated in our laboratory and termed "SSEC-D(stage-specific embryonic clone-D)", exhibited a transient extension of poly (A) strand at its 3' end with a peak at 18h after fertilization (corresponding to the late 1-cell stage) and a gradual degradation of the poly(A) strand thereafter. Based on this finding, we have examined this phenomenon in more detail in the past three years, and obtained several findings as mentioned below.1. Transient increase in the size of SSEC-D RNA is due to addition of poly (A) strand at its 3' end, and it requires new protein synthesis. 2. It is possible to perform Northern blot analysis using 10-20 zygotes and early embryos due to improvement of mRNA detection system. 3. Transient extension of RNA was also observed in zygotes after cytoplasmic injection experiments using in vitro synthesized RNAs containing EGFP cDNA ligated to various sizes of 3'-noncoding region of SSEC-D RNA. Thus, this phenomenon is already programmmed. 4. Addition of poly(A) spanning 300-400 nucleotides can release the translationally suppressed state of the maternal RNA iteself. 5. This poly(A) extension is dependent on the sequence of SSEC-D RNA itself and poly(A) sequence at its 3' end region. 6. It becomes possible to concentrate cDNAs enriched with maternal RNAs by improving the uptake of biotin labeled ATP by zygotes.