Rossant J, Sanford J P, Chapman V M, Andrews G K
Dev Biol. 1986 Oct;117(2):567-73. doi: 10.1016/0012-1606(86)90325-8.
The first two lineages to differentiate in the mouse embryo are the trophectoderm and primitive endoderm, which give rise to various extraembryonic structures only. Previous work has shown that all derivatives of these two lineages share the property of undermethylation of repetitive DNA sequences, both satellite and dispersed. Here we show that this undermethylation is not a peculiarity of these repetitive elements but is also a feature of structural gene sequences within both lineages. alpha-Fetoprotein, albumin, and major urinary protein gene sequences all showed extensive undermethylation at MspI restriction sites in extraembryonic lineages, which did not correlate with their expression in these tissues. The same sequences were heavily methylated in embryonic tissues as early as 7.5 days of development. There are, therefore, major global differences in DNA methylation between the earliest cell lineages to be established in the mouse embryo. The significance of these differences for cellular commitment events remains to be elucidated.
在小鼠胚胎中最早分化的两个谱系是滋养外胚层和原始内胚层，它们仅产生各种胚外结构。先前的研究表明，这两个谱系的所有衍生物都具有重复DNA序列（包括卫星序列和分散序列）低甲基化的特性。在此我们表明，这种低甲基化并非这些重复元件所特有，也是这两个谱系内结构基因序列的一个特征。甲胎蛋白、白蛋白和主要尿蛋白基因序列在胚外谱系的MspI限制位点均显示出广泛的低甲基化，这与它们在这些组织中的表达无关。早在发育7.5天时，相同的序列在胚胎组织中就高度甲基化。因此，在小鼠胚胎中最早建立的细胞谱系之间，DNA甲基化存在重大的全局差异。这些差异对细胞定向事件的意义仍有待阐明。
