Davegårdh Cajsa, Broholm Christa, Perfilyev Alexander, Henriksen Tora, García-Calzón Sonia, Peijs Lone, Hansen Ninna Schiøler, Volkov Petr, Kjøbsted Rasmus, Wojtaszewski Jørgen F P, Pedersen Maria, Pedersen Bente Klarlund, Ballak Dov B, Dinarello Charles A, Heinhuis Bas, Joosten Leo A B, Nilsson Emma, Vaag Allan, Scheele Camilla, Ling Charlotte
Department of Clinical Sciences, Lund University Diabetes Centre, Lund University, Malmö, 205 02, Sweden.
Department of Endocrinology, Rigshospitalet, Copenhagen, 2100, Denmark.
BMC Med. 2017 Feb 22;15(1):39. doi: 10.1186/s12916-017-0792-x.
Human skeletal muscle stem cells are important for muscle regeneration. However, the combined genome-wide DNA methylation and expression changes taking place during adult myogenesis have not been described in detail and novel myogenic factors may be discovered. Additionally, obesity is associated with low relative muscle mass and diminished metabolism. Epigenetic alterations taking place during myogenesis might contribute to these defects.
We used Infinium HumanMethylation450 BeadChip Kit (Illumina) and HumanHT-12 Expression BeadChip (Illumina) to analyze genome-wide DNA methylation and transcription before versus after differentiation of primary human myoblasts from 14 non-obese and 14 obese individuals. Functional follow-up experiments were performed using siRNA mediated gene silencing in primary human myoblasts and a transgenic mouse model.
We observed genome-wide changes in DNA methylation and expression patterns during differentiation of primary human muscle stem cells (myoblasts). We identified epigenetic and transcriptional changes of myogenic transcription factors (MYOD1, MYOG, MYF5, MYF6, PAX7, MEF2A, MEF2C, and MEF2D), cell cycle regulators, metabolic enzymes and genes previously not linked to myogenesis, including IL32, metallothioneins, and pregnancy-specific beta-1-glycoproteins. Functional studies demonstrated IL-32 as a novel target that regulates human myogenesis, insulin sensitivity and ATP levels in muscle cells. Furthermore, IL32 transgenic mice had reduced insulin response and muscle weight. Remarkably, approximately 3.7 times more methylation changes (147,161 versus 39,572) were observed during differentiation of myoblasts from obese versus non-obese subjects. In accordance, DNMT1 expression increased during myogenesis only in obese subjects. Interestingly, numerous genes implicated in metabolic diseases and epigenetic regulation showed differential methylation and expression during differentiation only in obese subjects.
Our study identifies IL-32 as a novel myogenic regulator, provides a comprehensive map of the dynamic epigenome during differentiation of human muscle stem cells and reveals abnormal epigenetic changes in obesity.
人类骨骼肌干细胞对肌肉再生至关重要。然而，在成人肌生成过程中发生的全基因组DNA甲基化和表达变化尚未得到详细描述，可能会发现新的肌生成因子。此外，肥胖与相对肌肉量低和代谢减弱有关。肌生成过程中发生的表观遗传改变可能导致这些缺陷。
我们使用Infinium HumanMethylation450 BeadChip试剂盒（Illumina）和HumanHT-12表达微珠芯片（Illumina）分析了来自14名非肥胖和14名肥胖个体的原代人成肌细胞分化前后的全基因组DNA甲基化和转录情况。在原代人成肌细胞和转基因小鼠模型中使用siRNA介导的基因沉默进行了功能后续实验。
我们观察到原代人肌肉干细胞（成肌细胞）分化过程中全基因组DNA甲基化和表达模式的变化。我们确定了肌生成转录因子（MYOD1、MYOG、MYF5、MYF6、PAX7、MEF2A、MEF2C和MEF2D）、细胞周期调节因子、代谢酶以及先前与肌生成无关基因（包括IL32、金属硫蛋白和妊娠特异性β-1-糖蛋白）的表观遗传和转录变化。功能研究表明IL-32是调节人类肌生成、胰岛素敏感性和肌肉细胞中ATP水平的新靶点。此外，IL32转基因小鼠的胰岛素反应和肌肉重量降低。值得注意的是，在肥胖与非肥胖受试者的成肌细胞分化过程中，观察到的甲基化变化约多3.7倍（147,161对39,572）。相应地，DNMT1表达仅在肥胖受试者的肌生成过程中增加。有趣的是，许多与代谢疾病和表观遗传调控相关的基因仅在肥胖受试者的分化过程中表现出差异甲基化和表达。
我们的研究确定IL-32为一种新的肌生成调节因子，提供了人类肌肉干细胞分化过程中动态表观基因组的全面图谱，并揭示了肥胖中的异常表观遗传变化。
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