Expression of c- jun/AP-1 during myogenic differentiation in mouse C 2C 12 myoblasts

Abstract

Mitogen withdrawal triggers myogenic differentiation in skeletal myoblasts in culture. We have examined the expression of the proto-oncogene c- jun during this process in mouse C 2C 12 myoblasts. c- jun belongs to a family of immediate early genes whose expression is activated in cultured cells in response to the addition of serum growth factors. Interestingly, expression of c- jun was maintained in mouse C 2C 12 and rat L6 myoblasts undergoing myogenic differentiation under low-serum conditions. Previously it has been reported that expression of c- jun is downregulated during differentiation of C2 cells. However, our results using C 2C 12 cells, a subclone of the C2 line, show that c- jun mRNA, protein and the activator-protein 1 (AP-1) DNA-binding activity were easily detected in proliferating myoblasts and differentiated myotubes. Although overexpression of c- jun has been shown to block myogenic differentiation in C2 cells, results presented here suggest that expression of c- jun at physiological levels may not interfere with skeletal myogenesis.