mED2-一个小鼠胚胎发育的新基因

克隆参与胚胎发育的新基因并研究其表达规律和功能是揭示胚胎发育的基因调控机理的重要途径。囊胚形成和原肠形成是哺乳动物胚胎发育过程中的两个关键阶段。囊胚阶段发生了胚胎的第一次分化，是细胞多能性和分化的一个转折点。此时涉及的基因活动，既有维持胚胎干细胞全能性或多能性的基因活动，又有按照预定发育模式参与胚胎定向分化的基因活动。原肠期是胚胎发育过程中的第二个关键转折点，涉及到3个胚层的形成和细胞命运决定等多种变化。在这个时期胚胎获得了胎儿原基的所有信息，新组织的产生和细胞迁移的再生组织与形态发生、细胞增殖、细胞分化、模式形成等存在着非常复杂而相互协调的关联。大多数细胞正由原来的多潜能逐渐向寡潜能发展，控制组织器官形态建成的基因正逐渐开启。这两个时期的基因表达图式、特征和种类会有很大的差异和变化，因此研究这两个时期的新基因的表达规律和功能，将是了解胚胎发育的基因调控机理的重要途径。文章以这两个时期胚胎为原始材料，利用减法杂交方法克隆到一新的小鼠胚胎基因mED2，对其进行了表达规律和生物学功能的初步分析。RT-PCR-Southern和原位杂交实验表明，mED2基因转录水平具有发育阶段的依赖性；随着发育过程的进行，其表达主要在胚神经系统和中胚层衍生的组织表达。mED2基因活性的knockdown对于合子的卵裂和植入前早期胚胎发育均有抑制作用。亚细胞定位实验表明，mED2基因编码的蛋白基本定位于细胞核膜及其临近的内膜细胞器（粗糙内质网和高尔基体）。根据生物信息学分析，mED2蛋白可能为一跨膜蛋白且与含有硫氧还蛋白结构域的蛋白有部分匹配。由此推测mED2基因参与了小鼠植入前早期胚胎发育，其基因产物可能通过蛋白之间的相互作用，即对蛋白进行后期修饰、折叠及行使分子伴侣等作用来活化或抑制其靶蛋白的活性，进而参与小鼠的早期胚胎发育。

mED2-A Novel Gene Involved in Mouse Embryonic Development

Dissection of new genes underlying embryonic development is important for our understanding of the molecular mechanism of vertebrate embryonic development. In this study, the expression pattern and functional analysis of a new gene, called mED2, originally cloned from mouse embryos using subtractive hybridization was reported, reED2 expression patterns were characterized by RT-PCR-Southern hybridization and in situ hybridization. The results showed that reED2 was mainly expressed in the embryonic nervous system and mesoderm-derived tissues and its expression varied depending on the embryonic developmental stages. The knockdown of mED2 activity by antisense RNA injection inhibited zygote cleavage and blastocyst formation during pre-implantation in mice. Subcellular localization of mED2-eGFP fusion protein revealed a pattern of nuclear membrane and juxta-/perinuclear location such as in the rough endoplasmic reticulum and Golgi apparatus. This finding was supported by bioinformatics analysis, which indicated reED2 protein to be a transmembrane protein with partial homology to the thioredoxin family of proteins. It is inferred that reED2 gene can probably take part in early embryonic development in mouse and may be involved in target protein posttranslational modification, turnover, folding, and stability at the endoplasmic reticulum and/or the Golgi apparatus.