Mesodermal cell lineage determination and proto-oncogene expression.
Previously, we have established a rat embryo fibroblastic cell line that is characterized as immortal, nontumorigenic and retains a diploid karyotype. We report here that this cell line will spontaneously differentiate along mesodermal cell lineages to form myotubes and adipocytes. We have isolated and characterized lineage-determined (nondifferentiated) preadipocytes and myoblasts. Using these cell lines we have investigated the expression of proto-oncogenes concomitant with lineage-specific determination. No major changes in proto-oncogene RNA levels were observed that correlated with lineage determination. These results would suggest that none of the 15 proto-oncogenes used in these experiments are involved in mesodermal lineage determination; but this does not rule out the possibility that other proto-oncogenes not tested or currently unknown may be involved. However, these differentiating subclones and nondifferentiating fibroblasts that exhibit a normal karyotype will be an excellent model-system to investigate the molecular basis of cell lineage determination.