P5.77 Sarcomeric gene and protein expression during human myogenesis in vitro

Abstract

In vertebrates, skeletal muscle is found throughout the body and forms during the entire life span. Adult skeletal muscle displays a high regenerative capacity, with satellite cells as the primary source of this remarkable ability. Satellite cells are quiescent muscle progenitors located between myofibers and their surrounding basal lamina. The formation of skeletal muscle cells, myogenesis, is a complex process, which takes place during embryonic development, postnatal growth and adult muscle regeneration. Myogenesis is marked by specific changes in muscle cell morphology and cytoarchitecture through the fusion of mononucleated myoblasts into multinucleated myotubes and the assembly of contractile sarcomeric myofibrils. The formation of contractile myofibrils involves the transition of myoblast cytoarchitecture, which requires a change in the expression of proteins from non-muscle-specific to muscle-specific isoforms. In this study, combined molecular and immunocytochemistry methods were used to investigate the expression profile of sarcomeric genes and proteins during myoblast proliferation and differentiation in human muscle cell line. We observed the expression of a panel of sarcomeric gene transcripts together with the early expression of a number of the investigated sarcomeric proteins at the proliferated myoblasts. In addition, after 6 days of differentiation, the majority of cells expressed all the investigated sarcomeric proteins. The results presented here provide novel insights into the sequential onset of the sarcomeric genes and proteins and support the previous notion that non-committed stem cells exist in the adult muscle satellite cells during myogenesis in vitro. In addition, our study demonstrates the effectiveness of a differentiation system, which transforms undifferentiated and star-shaped myoblasts, into long multinucleated myotubes, displaying the features of contractile muscle cells.