VIMENTIN, THE 57000 MOLECULAR-WEIGHT PROTEIN OF FIBROBLAST FILAMENTS, IS THE MAJOR CYTOSKELETAL COMPONENT IN IMMATURE GLIA

Abstract

Comparison of cytoskeletal preparations obtained from newborn and adult rat brain showed similar patterns on SDS-PAGE [sodium dodecyl sulfate-polyacrylamide gel electrophoresis]. Coelectrophoresis of the newborn and adult preparations revealed distinct differences in the mobility of 2 major bands in the MW range of 50-70,000. In adult brain cytoskeletons the main band in the 50,000 range co-migrated with purified rat GFA [glial fibrillary acidic] protein (apparent MW 53,000). No major band co-migrated with purified rat vimentin (apparent MW 57,000). The reverse was true for newborn brain cytoskeleton. In adult and newborn brain cytoskeleton a major band co-migrated with the 150,000 neurofilament polypeptide isolated from rat spinal cord by immunoaffinity chromatography. Another neurofilament polypeptide (apparent MW 72,000) was prominent in adult but not in newborn brain cytoskeleton. Newborn brain cytoskeleton comprised a band trailing behind the 72,000 neurofilament polypeptide. This band was not present in adult brain cytoskeleton. The distribution of vimentin in newborn rat brain was studied by immunofluorescence microscopy and compared to the distribution of GFA protein. A relatively limited number of GFA positive cells are present in the brain at this stage compared to later in development. The large number of vimentin positive cells in newborn brain was well in keeping with the presence of a prominent vimentin band in cytoskeletal preparations obtained from this tissue. With the exception of meninges and blood vessels, vimentin appeared to be mainly localized in immature glia: periventricular glia; glia in non-myelinated white matter; radial glia in cerebral cortex and basal ganglia; Bergmann glia in cerebellum (Bergmann glia are still GFA negative in newborn rat). The neuroblastic germinal layers in hippocampus and cerebellum did not stain with vimentin antisera.