Department of Embryology and Genetics, Vrije Universiteit Brussel, Laarbeeklaan 101, Brussels 1090, Belgium.
J Med Genet. 2010 Oct;47(10):700-3. doi: 10.1136/jmg.2009.074211. Epub 2010 Jul 19.
We have studied the methylation status of the sequence 152 nucleotides upstream of the CTG repeat of the DM1 locus in patients' peripheral blood. We used the methylation-sensitive endonucleases SacII, HpaII and HhaI, followed by PCR. This allowed to correlate the methylation status of each CTG allele with its size. Contrary to previous findings, only the SacII site is often but not always differentially methylated among expanded CTG alleles. Importantly, this methylation was not restricted to congenital DM1, nor to large expansions, as it was also present in DM1 patients with a classical phenotype and various expansion sizes. On the other hand, we did not find any methylated alleles on the HhaI and HpaII sites, as was reported by Steinbach et al, which is in line with the results of Shaw and collaborators. The size range of the repeat expansions with methylation was from as small as 300 to as large as 2800 repeats.
我们研究了患者外周血中的 DM1 基因座 CTG 重复序列上游 152 个核苷酸的甲基化状态。我们使用甲基化敏感内切酶 SacII、HpaII 和 HhaI 进行了后续的 PCR。这使得我们可以将每个 CTG 等位基因的甲基化状态与其大小相关联。与之前的发现相反,仅 SacII 位点在扩增的 CTG 等位基因中经常(但并非总是)表现出不同程度的甲基化。重要的是,这种甲基化不仅局限于先天性 DM1,也不仅局限于较大的扩增,因为它也存在于具有典型表型和各种扩增大小的 DM1 患者中。另一方面,我们在 HhaI 和 HpaII 位点没有发现任何甲基化等位基因,这与 Steinbach 等人的报道一致,与 Shaw 及其同事的结果一致。发生甲基化的重复扩增的大小范围从 300 个重复到 2800 个重复不等。