Cell-type specific segregation of transcriptional expression of glial genes in the rat peripheral neurotumor RT4 cell lines.

Four types of cells, RT4-AC (stem cell type), RT4-B and RT4-E (neuronal cell types), and RT4-D (glial cell type) were previously isolated from an ethylnitrosourea (ENU) induced rat peripheral neurotumor RT4. In a phenomenon termed cell-type conversion, RT4-AC spontaneously and permanently gives rise to the three other cell types in culture. In the RT4 system the expression of glial fibrillary acidic protein (GFAP) and S100 beta protein genes segregates in a cell-type specific manner. To further characterize the RT4 family, the expression of four myelin-forming glial genes--P0 glycoprotein, suppressed cAMP inducible POU (SCIP), 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP), and myelin basic protein (MBP)--has been studied in the RT4 cell lines. In addition to these genes, the expression of the low-affinity nerve growth factor (LNGF) receptor (expressed in immature Schwann cells) has been examined. We have found the following results. 1) The stem cell type RT4-AC and the glial cell type RT4-D express mRNA transcripts of P0, SCIP, and CNP (the larger form, 2.8 kb), and the amount of mRNA of these genes was increased by forskolin. 2) RT4-AC and RT4-D also express a low level of MBP mRNA upon forskolin treatment. 3) The neuronal cell types RT4-B and RT4-E do not express any of these myelin-forming glial genes with or without forskolin treatment. 4) The LNGF receptor mRNA is expressed in RT4-AC and RT4-D and at a lower level in RT4-B; its expression is stimulated by forskolin.