Mutations in Lamin A/C Gene Causes Mechanosensing Defects in Human Myoblasts

Abstract

The mechanisms underlying mechanosensitivity are critical for muscle development and functionality. The presence of lamin A/C is essential for intact nucleoskeleton and mechanical transmission between the nucleus and the extracellular matrix. Therefore, we tested the hypothesis that mutation in the LMNA gene (encoding for lamin A/C) cause mechanosensing defects in human myoblasts.Myoblasts with LMNA p.Lys32del mutation (Lmna) and normal human myoblasts (WT) were immortalized and cultured in a linear 3D fibrin matrix. At day 1, WT have spontaneously aligned along the gel axis whereas Lmna cells exhibited random orientation (p<0.001). Mutated myoblasts had larger and more abundant actin bundles, and vinculin adhesion sites were longer and thicker compared with WT myoblasts (each p<0.05). This was associated with higher protein and mRNA expression of vinculin in Lmna cells (p<0.01). In WT, uni-axial cyclic stretch of the gel (0.5 Hz, 10% for 4 hours) induced cytoskeletal reorganization characterized by thickening of actin stress fibers and elongation of vinculin adhesion sites. These changes were absent in Lmna and in blebbistatin- or Y-27632-treated WT. Similar results were obtained in primary myoblasts from another patient with similar mutation and in myoblasts with LMNA p.Arg249Trp mutation. In conclusion, these data provide first evidence that lamin A/C mutation causes defects in myoblast mechanosensing that may contribute to mechanical damage in striated muscles from L-CMD.