Saito Fumiaki, Kanagawa Motoi, Ikeda Miki, Hagiwara Hiroki, Masaki Toshihiro, Ohkuma Hidehiko, Katanosaka Yuki, Shimizu Teruo, Sonoo Masahiro, Toda Tatsushi, Matsumura Kiichiro
Department of Neurology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan,
Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
Hum Mol Genet. 2014 Sep 1;23(17):4543-58. doi: 10.1093/hmg/ddu168. Epub 2014 Apr 9.
Several types of muscular dystrophy are caused by defective linkage between α-dystroglycan (α-DG) and laminin. Among these, dystroglycanopathy, including Fukuyama-type congenital muscular dystrophy (FCMD), results from abnormal glycosylation of α-DG. Recent studies have shown that like-acetylglucosaminyltransferase (LARGE) strongly enhances the laminin-binding activity of α-DG. Therefore, restoration of the α-DG-laminin linkage by LARGE is considered one of the most promising possible therapies for muscular dystrophy. In this study, we generated transgenic mice that overexpress LARGE (LARGE Tg) and crossed them with dy(2J) mice and fukutin conditional knockout mice, a model for laminin α2-deficient congenital muscular dystrophy (MDC1A) and FCMD, respectively. Remarkably, in both the strains, the transgenic overexpression of LARGE resulted in an aggravation of muscular dystrophy. Using morphometric analyses, we found that the deterioration of muscle pathology was caused by suppression of muscle regeneration. Overexpression of LARGE in C2C12 cells further demonstrated defects in myotube formation. Interestingly, a decreased expression of insulin-like growth factor 1 (IGF-1) was identified in both LARGE Tg mice and LARGE-overexpressing C2C12 myotubes. Supplementing the C2C12 cells with IGF-1 restored the defective myotube formation. Taken together, our findings indicate that the overexpression of LARGE aggravates muscular dystrophy by suppressing the muscle regeneration and this adverse effect is mediated via reduced expression of IGF-1.
几种类型的肌肉萎缩症是由α- dystroglycan（α-DG）与层粘连蛋白之间的连接缺陷引起的。其中，包括福山型先天性肌肉萎缩症（FCMD）在内的糖基化肌营养不良症是由α-DG的异常糖基化导致的。最近的研究表明，类N-乙酰葡糖胺基转移酶（LARGE）能强烈增强α-DG与层粘连蛋白的结合活性。因此，通过LARGE恢复α-DG-层粘连蛋白连接被认为是治疗肌肉萎缩症最有前景的可能疗法之一。在本研究中，我们培育了过度表达LARGE的转基因小鼠（LARGE转基因小鼠），并将它们分别与dy(2J)小鼠和福库汀条件性敲除小鼠杂交，这两种小鼠分别是层粘连蛋白α2缺陷型先天性肌肉萎缩症（MDC1A）和FCMD的模型。值得注意的是，在这两种品系中，LARGE的转基因过度表达都导致了肌肉萎缩症的加重。通过形态计量分析，我们发现肌肉病理的恶化是由肌肉再生的抑制引起的。LARGE在C2C12细胞中的过度表达进一步证明了肌管形成存在缺陷。有趣的是，在LARGE转基因小鼠和过度表达LARGE的C2C12肌管中都发现胰岛素样生长因子1（IGF-1）的表达降低。用IGF-1补充C2C12细胞可恢复有缺陷的肌管形成。综上所述，我们的研究结果表明，LARGE的过度表达通过抑制肌肉再生而加重肌肉萎缩症，并且这种不良影响是通过IGF-1表达降低介导的。
