Effect of culture conditions on PLP and MAG gene expression in rat glioma C6 cells.

The effects of culture conditions on the expression of myelin-specific genes, i.e. proteolipid protein (PLP) and myelin-associated glycoprotein (MAG) in rat glioma C6 cells was studied. Early passage (40-46) cells had higher steady-state level of PLP- and MAG-specific mRNA than late (100) passage cells when grown in defined (serum-free) medium. The PLP gene expression was increased whereas the MAG gene expression was reduced in the presence of 10% fetal calf serum in either passage. The level of both PLP- and MAG-specific messages was also directly related to the cell density indicating cell contact-induced stimulation of the gene expression. Furthermore, the cells apparently secrete factors into the medium, which upregulate the gene expression in autocrine fashion. The results also indicate a dissimilarity of regulatory mechanisms involved in the expression of the PLP and MAG genes.