Elevated c-fos expression inhibits differentiation of L6 rat myoblasts.
Expression of c-fos is induced by a number of signals in several cell systems. Although the exact function of the c-fos product is unknown, it has been implicated to be of importance for both cell growth and differentiation (Verma and Sassone-Corsi, 1987). To analyze how c-fos expression relates to in vitro myogenic differentiation, the kinetics of c-fos mRNA expression during spontaneous in vitro differentiation of L6J1 myoblasts was examined; c-fos transcripts were most abundant at day 4 of the differentiation process. Multinucleated myotubes and expression of alpha-actin and myosin heavy chain (MHC) mRNA appeared later, at day 6 or 7, and increased to maximal levels after 10 days in culture. To analyze further the relation between c-fos expression and L6J1 myogenic differentiation, L6J1 myoblasts were transfected with expression vectors containing the murine c-fos gene driven by a metallothionein promoter. The growth rate of c-fos-transfected L6J1 cells did not differ from that of control cells. However, formation of myotubes was significantly reduced in c-fos-transfected L6J1 cultures compared with neo-transfected controls. Myotube formation and expression of the myogenic markers alpha-actin and MHC were reduced in subclones expressing high levels of c-fos, but not in subclones with lower levels of c-fos expression. These results indicate that a marked elevation of c-fos expression at least partially inhibits L6J1 myogenic differentiation.
Rahm
M
M
Department of Medical Cell Genetics, Karolinska Institutet, Stockholm, Sweden.
Jin
P
P
Sümegi
J
J
Sejersen
T
T
D000199:Actins / Q000235:genetics; D000818:Animals; D015139:Blotting, Southern; D002454:Cell Differentiation; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D009132:Muscles / Q000166:cytology* / Q000378:metabolism; D009218:Myosins / Q000235:genetics; D011519:Proto-Oncogenes; D012313:RNA / Q000032:analysis; D051381:Rats; D014158:Transcription, Genetic; D014162:Transfection
D000199:Actins; D012313:RNA; D009218:Myosins