Wang Min, Xie Hehuang, Shrestha Sheela, Sredni Simone, Morgan Gabrielle A, Pachman Lauren M
Children's Hospital of Chicago Research Center and Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
Arthritis Rheum. 2012 Oct;64(10):3478-85. doi: 10.1002/art.34573.
To determine the effect of methylation alteration in inflamed muscles from children with juvenile dermatomyositis (DM) and other idiopathic inflammatory myopathies (IIMs).
Magnetic resonance imaging-directed diagnostic muscle biopsies yielded samples from 20 children with juvenile DM, which were used for genome-wide DNA methylation profiling, as were muscle biopsy samples from 4 healthy controls. Bisulfite treatment followed by pyrosequencing confirmed methylation status in juvenile DM and other IIMs. Immunohistochemistry defined localization and expression levels of WT1.
Comparison of genome-wide DNA methylation profiling between juvenile DM muscle and normal control muscle revealed 27 genes with a significant methylation difference between the groups. These genes were enriched with transcription factors and/or cell cycle regulators and were unrelated to duration of untreated disease. Six homeobox genes were among them; ALX4, HOXC11, HOXD3, and HOXD4 were hypomethylated, while EMX2 and HOXB1 were hypermethylated. WT1 was significantly hypomethylated in juvenile DM (Δβ = -0.41, P < 0.001). Bisulfite pyrosequencing verification in samples from 56 patients with juvenile DM confirmed the methylation alterations of these genes. Similar methylation alterations were observed in juvenile polymyositis (n = 5) and other IIMs (n = 9). Concordant with the other findings, WT1 protein was increased in juvenile DM muscle, with average positive staining of 11.6%, but was undetectable in normal muscle (P < 0.001).
These results suggest that affected muscles of children with juvenile DM and IIMs have the capacity to be repaired, and that homeobox and WT1 genes are epigenetically marked to facilitate this repair process, potentially suggesting new avenues of therapeutic intervention.
确定青少年皮肌炎（DM）及其他特发性炎性肌病（IIM）患儿炎症肌肉中甲基化改变的影响。
磁共振成像引导下的诊断性肌肉活检获取了20例青少年DM患儿的样本，用于全基因组DNA甲基化分析，4例健康对照的肌肉活检样本也用于此项分析。亚硫酸氢盐处理后进行焦磷酸测序，以确认青少年DM及其他IIM中的甲基化状态。免疫组织化学确定WT1的定位和表达水平。
青少年DM肌肉与正常对照肌肉全基因组DNA甲基化分析比较显示，两组之间有27个基因存在显著甲基化差异。这些基因富含转录因子和/或细胞周期调节因子，且与未治疗疾病的持续时间无关。其中有6个同源框基因；ALX4、HOXC11、HOXD3和HOXD4低甲基化，而EMX2和HOXB1高甲基化。WT1在青少年DM中显著低甲基化（Δβ = -0.41，P < 0.001）。对56例青少年DM患者样本进行的亚硫酸氢盐焦磷酸测序验证了这些基因的甲基化改变。在青少年多发性肌炎（n = 5）和其他IIM（n = 9）中也观察到类似的甲基化改变。与其他结果一致，WT1蛋白在青少年DM肌肉中增加，平均阳性染色为11.6%，而在正常肌肉中未检测到（P < 0.001）。
这些结果表明，青少年DM和IIM患儿受影响的肌肉具有修复能力，同源框基因和WT1基因在表观遗传上有标记以促进这一修复过程，这可能提示了新的治疗干预途径。
