Don Gnocchi Foundation, Milan, Italy.
Dept. of Biomedicine and Prevention, Medical Genetics Section, University of Rome Tor Vergata, Italy.
Biochim Biophys Acta Mol Basis Dis. 2018 Mar;1864(3):917-924. doi: 10.1016/j.bbadis.2017.12.037. Epub 2017 Dec 29.
Myotonic Dystrophy type 2 (DM2) is a multisystemic disorder associated with an expanded [CCTG]n repeat in intron 1 of the CNBP gene. Epigenetic modifications have been reported in many repeat expansion disorders, including myotonic dystrophy type 1 (DM1), either as a mechanism to explain somatic repeat instability or transcriptional alterations in disease genes. The purpose of our work was to determine the effect of DM2 mutation on the methylation status of CpG islands localized in the 5' promoter region and in the 3' end of the [CCTG]n expansion of the CNBP gene. By bisulfite pyrosequencing, we characterized the methylation profile of two different CpG islands within these regions, either in whole blood and skeletal muscle tissues of DM2 patients (n=72 and n=7, respectively) and controls (n=50 and n=7, respectively). Moreover, we compared the relative mRNA transcript levels of CNBP gene in leukocytes and in skeletal muscle tissues from controls and DM2 patients. We found that CpG sites located in the promoter region showed hypomethylation, whereas CpG sites at 3' end of the CCTG array are hypermethylated. Statistical analyses did not demonstrate any significant differences in the methylation profile between DM2 patients and controls in both tissues analyzed. According to the methylation analysis, CNBP gene expression levels are not significantly altered in DM2 patients. These results show that [CCTG]n repeat expansion, differently from the DM1 mutation, does not influence the methylation status of the CNBP gene and suggest that other molecular mechanisms are involved in the pathogenesis of DM2.
肌强直性营养不良 2 型（DM2）是一种多系统疾病，与 CNBP 基因内含子 1 中的 [CCTG]n 重复扩展有关。在许多重复扩展疾病中，包括肌强直性营养不良 1 型（DM1），已经报道了表观遗传修饰，无论是作为解释体细胞重复不稳定性的机制，还是作为疾病基因转录改变的机制。我们工作的目的是确定 DM2 突变对位于 CNBP 基因 5'启动子区域和 [CCTG]n 扩展 3'末端的 CpG 岛的甲基化状态的影响。通过亚硫酸氢盐焦磷酸测序，我们对这两个区域内的两个不同 CpG 岛的甲基化图谱进行了特征描述，分别是 DM2 患者（n=72 和 n=7）和对照组（n=50 和 n=7）的全血和骨骼肌组织，以及对照组和 DM2 患者的白细胞和骨骼肌组织中的 CNBP 基因相对 mRNA 转录水平进行了比较。我们发现，位于启动子区域的 CpG 位点表现出低甲基化，而 CCTG 阵列 3'端的 CpG 位点则表现出高甲基化。统计分析表明，在两种分析的组织中，DM2 患者和对照组之间的甲基化图谱没有显著差异。根据甲基化分析，DM2 患者的 CNBP 基因表达水平没有明显改变。这些结果表明，[CCTG]n 重复扩展与 DM1 突变不同，不会影响 CNBP 基因的甲基化状态，并表明其他分子机制参与了 DM2 的发病机制。
