Latham K E, Beddington R S, Solter D, Garrels J I
Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania.
Mol Reprod Dev. 1993 Jun;35(2):140-50. doi: 10.1002/mrd.1080350207.
The changes in protein synthesis that occur during differentiation of the primitive germ layers were examined by high-resolution, two-dimensional gel electrophoresis of proteins synthesized in 6.5 and 7.5 days postcoitum (d.p.c.) mouse embryos. For 6.5 d.p.c. embryos, protein synthesis patterns were compared between whole extraembryonic and embryonic regions and between embryonic visceral endoderm and embryonic ectoderm. For 7.5 d.p.c. embryos, comparisons were made between extraembryonic and embryonic regions and between isolated embryonic endoderm, mesoderm, and ectoderm. Each of the isolated 7.5 d.p.c. germ layers was divided into anterior and posterior fragments in order to evaluate possible regional differences in gene expression along the anterior-posterior axis. Comparisons of protein synthesis patterns revealed the greatest difference between isolated endoderm and ectoderm, indicating that by as early as 6.5 d.p.c. patterns of gene expression differ significantly between these tissues. The greatest similarities were found between ectoderm and whole embryonic regions and between endoderm and whole extraembryonic regions, which most likely reflects the overall cellular compositions of the embryonic and extraembryonic regions. Based on their patterns of synthesis, four groups of proteins were identified that were preferentially synthesized in either endoderm or ectoderm. These provide useful markers for studying differentiation in these tissues. One other protein, migrating at the position expected for vimentin, was synthesized at an elevated rate in isolated mesoderm. We also observed differences in rates of synthesis of alpha-tubulin and tropomyosin-5 indicative of potential differences in cytoskeletal composition among the germ layers beyond those previously described. The difference in overall protein synthesis patterns between anterior and posterior regions was greatest in the embryonic endoderm, indicating that differentiation along the anterior-posterior axis may be initiated sooner or may proceed more rapidly in the endoderm than in the other germ layers. These data provide the first quantitative evaluation of the degree to which differentiation of the three primitive germ layers affects protein synthesis patterns and reveal potentially useful markers of endoderm and ectoderm differentiation.
通过对妊娠6.5天和7.5天（d.p.c.）的小鼠胚胎中合成的蛋白质进行高分辨率二维凝胶电泳，研究了原始胚层分化过程中发生的蛋白质合成变化。对于6.5 d.p.c.的胚胎，比较了整个胚外区域和胚胎区域之间以及胚胎内胚层和外胚层之间的蛋白质合成模式。对于7.5 d.p.c.的胚胎，比较了胚外区域和胚胎区域之间以及分离的胚胎内胚层、中胚层和外胚层之间的蛋白质合成模式。为了评估沿前后轴基因表达可能存在的区域差异，将每个分离的7.5 d.p.c.胚层分为前部和后部片段。蛋白质合成模式比较显示，分离的内胚层和外胚层之间差异最大，表明早在6.5 d.p.c.时，这些组织之间的基因表达模式就有显著差异。在外胚层与整个胚胎区域之间以及内胚层与整个胚外区域之间发现了最大的相似性，这很可能反映了胚胎区域和胚外区域的整体细胞组成。根据它们的合成模式，鉴定出了四组优先在内胚层或外胚层中合成的蛋白质。这些为研究这些组织中的分化提供了有用的标记物。另一种在波形蛋白预期位置迁移的蛋白质，在分离出的中胚层中合成速率升高。我们还观察到α-微管蛋白和原肌球蛋白-5合成速率的差异，这表明胚层之间细胞骨架组成的潜在差异超出了先前描述的范围。胚胎内胚层中前后区域之间整体蛋白质合成模式的差异最大，表明沿前后轴的分化可能在内胚层中比在其他胚层中更早开始或进行得更快。这些数据首次对三个原始胚层的分化影响蛋白质合成模式的程度进行了定量评估，并揭示了内胚层和外胚层分化的潜在有用标记物。
