EXPRESSION AND DISTRIBUTION OF GAP-43 IN HUMAN ASTROCYTES IN CULTURE

By combining mRNA analysis and immunocytochemistry, we investigated th e expression of the growth associated protein 43 (GAP-43) in enriched populations of astrocytes, obtained from mixed cultures of human fetal brains. Total cellular RNA was extracted from cell pellets and revers e transcribed into cDNA; cDNA was subjected to PCR amplification using primers specific for GAP-43 and PCR products were separated through p olyacrylamide gels. Double immunofluorescence staining was performed o n dissociated cell cultures using antibodies to glial fibrillary acidi c protein (GFAP) and to GAP-43. Results showed that both transcription and translation for GAP-43 occur in cultured astrocytes. GAP-43 immun oreacting material was detected in the cell processes and diffusely in the cytoplasm of GFAP-positive astrocytes, during early stages of mai ntenance in vitro. In older cultures, GAP-43 immunoreactivity persiste d in a large percentage of cells, with a tendency to accumulate in per inuclear areas. These observations provide evidence that GAP-43 is not restricted to neuronal cells. The close spatial association with cyto skeletal constituents, as observed in astrocytes, suggests a role for this protein in the control of cell shape, motility and adhesion proce sses.