Cellular micro-environments reveal defective mechanosensing responses and elevated YAP signaling in LMNA-mutated muscle precursors

Abstract

The mechanisms underlying cell response to mechanical forces are critical for muscle development and functionality. We aim to determine whether mutations of the LMNA gene causing congenital muscular dystrophy impair the ability of muscle precursors to sense tissue stiffness and to respond to mechanical challenge. We found that LMNA-mutated myoblasts (LMNA) embedded in soft matrix did not align along the gel axis whereas control myoblasts did. LMNA myoblasts were unable to tune their cytoskeletal tension to the tissue stiffness as attested by inappropriate cell-matrix adhesion sites and cytoskeletal tension in soft versus rigid substrates or after mechanical challenge. Importantly, in soft 2D and/or static 3D conditions, LMNA myoblasts demonstrated enhanced activation of Yes-Associated Protein (YAP) signaling pathway that was paradoxically reduced after cyclic stretch. SiRNA-mediated downregulation of YAP reduced adhesion and actin stress fibers in LMNA myoblasts. This is the first demonstration that human myoblasts with LMNA mutations have mechanosensing defects through a YAP-dependent pathway. In addition, our data emphasize the crucial role of biophysical attributes of cellular microenvironment to the response of mechanosensing pathways in lamin A/C mutated myoblasts.