GLIAL FIBRILLARY ACIDIC PROTEIN AND ITS ENCODING MESSENGER-RNA EXHIBIT MOSAIC EXPRESSION IN A GLIOBLASTOMA MULTIFORM CELL-LINE OF CLONAL ORIGIN

The expression of two astroglial differentiation markers, vimentin and glial fibrillary acidic protein, was investigated in a previously est ablished human glioma cell line of clonal origin (GL15). Vimentin immu nolabelling was homogeneously expressed in all cells. Glial fibrillary acidic protein and its encoding message, investigated by immunocytoch emistry and in situ hybridization, showed a mosaic-like expression. On ly 30% of the cell population expressed glial fibrillary acidic protei n and its mRNA. Western and Northern blots performed for both markers confirmed the presence of both proteins and messages, and their level was correlated with the observed antigenic and molecular probe labelli ng. The overall antigenic pattern suggests that GL-15 cells do not bel ong to the 0-2A progenitor cell lineage and may arise from a clonal ex pansion of astrocyte precursors.