Chang Wakam, Antoku Susumu, Östlund Cecilia, Worman Howard J, Gundersen Gregg G
a Department of Pathology and Cell Biology ; College of Physicians and Surgeons; Columbia University ; New York , NY USA.
Nucleus. 2015;6(1):77-88. doi: 10.1080/19491034.2015.1004947.
Myoblast migration is essential for muscle development and repair; however, the factors that contribute to the polarity of migrating myoblasts are relatively unknown. We find that randomly migrating C2C12 myoblasts orient their centrosomes in the direction of migration. Using wounded monolayers, we further show that centrosome orientation is stimulated by the serum factor lysophosphatidic acid (LPA) and involves the rearward movement of the nucleus while the centrosome is maintained at the cell centroid. The rate of nuclear movement correlated with that of actin retrograde flow and both cytochalasin D and blebbistatin prevented nuclear movement and centrosome orientation. Actin-dependent rearward nuclear movement in fibroblasts is mediated by assembly of nuclear membrane nesprin-2G and SUN2 LINC complexes into transmembrane actin-associated nuclear (TAN) lines anchored by A-type lamins and emerin. In C2C12 myoblasts, depletion of nesprin-2G, SUN2 or lamin A/C prevented nuclear movement and endogenous nesprin-2G and a chimeric GFP-mini-nesprin-2G formed TAN lines during nuclear movement. Depleting nesprin-2G strongly interfered with directed cell migration and reduced the efficiency of myoblast fusion into multinucleated myotubes. Our results show that nuclear movement contributes to centrosome orientation and polarity for efficient migration and fusion of myoblasts. Given that mutations in the genes encoding A-type lamins, nesprin-2 and SUN2 cause Emery-Dreifuss muscular dystrophy and related myopathies, our results have implications for understanding the mechanism of disease pathogenesis.
成肌细胞迁移对于肌肉发育和修复至关重要;然而,促成迁移成肌细胞极性的因素相对尚不明确。我们发现随机迁移的C2C12成肌细胞会使其中心体沿迁移方向定向。利用损伤的单层细胞,我们进一步表明中心体定向受到血清因子溶血磷脂酸(LPA)的刺激,并且涉及细胞核的向后移动,而中心体则维持在细胞质中央。核移动速率与肌动蛋白逆行流的速率相关,细胞松弛素D和博来霉素均能阻止核移动和中心体定向。成纤维细胞中依赖肌动蛋白的核向后移动是由核膜nesprin - 2G和SUN2 LINC复合体组装成由A型核纤层蛋白和emerin锚定的跨膜肌动蛋白相关核(TAN)线介导的。在C2C12成肌细胞中,nesprin - 2G、SUN2或核纤层蛋白A/C的缺失会阻止核移动,并且内源性nesprin - 2G和嵌合型绿色荧光蛋白 - 小nesprin - 2G在核移动过程中形成TAN线。敲低nesprin - 2G会强烈干扰细胞的定向迁移,并降低成肌细胞融合形成多核肌管的效率。我们的结果表明,核移动有助于中心体定向和极性,从而实现成肌细胞的高效迁移和融合。鉴于编码A型核纤层蛋白、nesprin - 2和SUN2的基因突变会导致埃默里 - 德赖富斯肌营养不良症及相关肌病,我们的结果对于理解疾病发病机制具有重要意义。