Collins Carol M, Ellis Joseph A, Holaska James M
University of the Sciences, Department of Pharmaceutical Sciences, 600 S. 43rd St, Philadelphia, PA 19104, USA.
University of the Sciences, Department of Pharmaceutical Sciences, 600 S. 43rd St, Philadelphia, PA 19104, USA
Dis Model Mech. 2017 Apr 1;10(4):385-397. doi: 10.1242/dmm.028787. Epub 2017 Feb 10.
Mutations in the gene encoding emerin cause Emery-Dreifuss muscular dystrophy (EDMD). Emerin is an integral inner nuclear membrane protein and a component of the nuclear lamina. EDMD is characterized by skeletal muscle wasting, cardiac conduction defects and tendon contractures. The failure to regenerate skeletal muscle is predicted to contribute to the skeletal muscle pathology of EDMD. We hypothesize that muscle regeneration defects are caused by impaired muscle stem cell differentiation. Myogenic progenitors derived from emerin-null mice were used to confirm their impaired differentiation and analyze selected myogenic molecular pathways. Emerin-null progenitors were delayed in their cell cycle exit, had decreased myosin heavy chain (MyHC) expression and formed fewer myotubes. Emerin binds to and activates histone deacetylase 3 (HDAC3). Here, we show that theophylline, an HDAC3-specific activator, improved myotube formation in emerin-null cells. Addition of the HDAC3-specific inhibitor RGFP966 blocked myotube formation and MyHC expression in wild-type and emerin-null myogenic progenitors, but did not affect cell cycle exit. Downregulation of emerin was previously shown to affect the p38 MAPK and ERK/MAPK pathways in C2C12 myoblast differentiation. Using a pure population of myogenic progenitors completely lacking emerin expression, we show that these pathways are also disrupted. ERK inhibition improved MyHC expression in emerin-null cells, but failed to rescue myotube formation or cell cycle exit. Inhibition of p38 MAPK prevented differentiation in both wild-type and emerin-null progenitors. These results show that each of these molecular pathways specifically regulates a particular stage of myogenic differentiation in an emerin-dependent manner. Thus, pharmacological targeting of multiple pathways acting at specific differentiation stages may be a better therapeutic approach in the future to rescue muscle regeneration .
编码emerin的基因突变会导致埃默里-德赖富斯肌营养不良症（EDMD）。Emerin是一种整合的内核膜蛋白，也是核纤层的一个组成部分。EDMD的特征是骨骼肌萎缩、心脏传导缺陷和肌腱挛缩。预计骨骼肌再生失败会导致EDMD的骨骼肌病理变化。我们假设肌肉再生缺陷是由肌肉干细胞分化受损引起的。利用来自emerin基因敲除小鼠的成肌祖细胞来证实其分化受损，并分析选定的成肌分子途径。缺乏emerin的祖细胞在细胞周期退出方面延迟，肌球蛋白重链（MyHC）表达降低，形成的肌管较少。Emerin与组蛋白去乙酰化酶3（HDAC3）结合并激活它。在此，我们表明，HDAC3特异性激活剂茶碱可改善缺乏emerin的细胞中的肌管形成。添加HDAC3特异性抑制剂RGFP966可阻断野生型和缺乏emerin的成肌祖细胞中的肌管形成和MyHC表达，但不影响细胞周期退出。先前的研究表明，emerin的下调会影响C2C12成肌细胞分化中的p38丝裂原活化蛋白激酶（MAPK）和细胞外信号调节激酶/丝裂原活化蛋白激酶（ERK/MAPK）途径。使用完全缺乏emerin表达的纯化成肌祖细胞群体，我们表明这些途径也受到破坏。抑制ERK可改善缺乏emerin的细胞中的MyHC表达，但未能挽救肌管形成或细胞周期退出。抑制p38 MAPK可阻止野生型和缺乏emerin的祖细胞的分化。这些结果表明，这些分子途径中的每一条都以emerin依赖的方式特异性调节成肌分化的特定阶段。因此，针对在特定分化阶段起作用的多种途径进行药物靶向治疗可能是未来挽救肌肉再生的更好治疗方法。
