Bartlett M H, Adra C N, Park J, Chapman V M, McBurney M W
Department of Medicine, University of Ottawa, Ontario, Canada.
Somat Cell Mol Genet. 1991 Jan;17(1):35-47. doi: 10.1007/BF01233203.
The extent of methylation of DNA sequences upstream and within the two X-linked genes, Pgk-1 and Hprt, was analyzed in male and female somatic cells and in female embryonal carcinoma cells carrying either two active X chromosomes (Xa) or one active and one inactive X chromosome (Xi). Sites upstream and within the first intron of both Pgk-1 and Hprt were heavily methylated on the Xi in somatic cells and in embryonal carcinoma cells with an Xi. Reactivation of this Xi was accompanied by extensive demethylation of these sites. In female embryonal carcinoma cells with two active X chromosomes, one X inactivates during differentiation in culture; however, methylation did not occur during differentiation, consistent with the idea that DNA methylation does not play a role in the initiation of X inactivation but may be involved in maintaining inactivation of those genes on the Xi.
在雄性和雌性体细胞以及携带两条活性X染色体（Xa）或一条活性X染色体和一条失活X染色体（Xi）的雌性胚胎癌细胞中，分析了两个X连锁基因Pgk - 1和Hprt上游及基因内部DNA序列的甲基化程度。在体细胞和带有Xi的胚胎癌细胞中，Pgk - 1和Hprt第一个内含子的上游及内部位点在Xi上高度甲基化。这条Xi的重新激活伴随着这些位点的广泛去甲基化。在具有两条活性X染色体的雌性胚胎癌细胞中，一条X在培养分化过程中失活；然而，在分化过程中并未发生甲基化，这与DNA甲基化在X染色体失活起始过程中不起作用，但可能参与维持Xi上那些基因的失活这一观点一致。
