The maintenance of methylation-free islands in transgenic mice.
The maintenance of methylation-free islands in transgenic mice.
复制标题
转基因小鼠中无甲基化岛的维持。
作者：
A. Kolstø;G. Kollias;V. Giguère;K. Isobe;H. Prydz;F. Grosveld
Thy-1基因以组织和阶段特异性模式表达，具有典型的1.6kb甲基化无岛（MFI），覆盖两个备选第一外显子的上游和下游约600bp。通过将小鼠Thy-1.1/人Thy-1基因显微注射到受精卵中，我们能够证明转基因小鼠的MFI得到了恢复。侧翼序列被甲基化，但在不同发育阶段的转基因小鼠的所有组织中，无论基因的表达位置如何，MFI都保持未甲基化。有一个例外，在14.5天胚胎的胚胎外组织中，一小部分岛被甲基化。我们得出结论，MFI的维持是由基因中存在的顺式作用序列调控的，并表明岛屿的非甲基化状态与基因表达的必要条件一致，但不是充分条件。
The Thy-1 gene is expressed in a tissue- and stage-specific pattern and has a typical 1.6kb methylation-free island (MFI) covering about 600bp upstream and downstream of the two alternative first exons. By microinjection of a mouse Thy-1.1/human Thy-1 gene into fertilized eggs, we were able to show that the MFI is restored in the transgenic mice. The flanking sequence became methylated, but the MFI remains unmethylated in all tissues of transgenic mice at different developmental stages tested, irrespective of the site of expression of the gene. There is one exception, in extra-embryonal tissues of 14.5 day embryos a small percentage of the islands were methylated. We conclude that maintenance of the MFI is regulated by cis-acting sequences present within the gene, and indicates that the unmethylated state of the islands is consistent with a necessary but not sufficient condition for expression of the gene.