DEVELOPMENTAL EXPRESSION OF NEUROFILAMENT AND GLIAL FILAMENT PROTEINSIN RAT CEREBELLUM

Neurofilament protein (NFP) consists of three subunits: NF200, NF150 a nd NF68. Several studies on expression of NFP in developing brain have shown that NF200 appears later than NF150 and NF68. However, there ar e some reports on simultaneous appearance of these subunits in develop ment. The present study is an attempt to resolve this controversy. Rat cerebellum was chosen as most of its development takes place during t he first three weeks of postnatal period. Cytoskeletal and NFP prepara tions from newborn (P0), postnatal day 8 (P8), P15, P21, P30 and adult (3 months) rat cerebella were subjected to electrophoresis on 7.5% SD S-PAGE. All the NFP subunits were present from PO onwards and there wa s an increase in NFP content and glial fibrillary acidic protein (GFAP )with age as revealed by the densitometric scanning. Immunoblots of NF P preparations confirmed the presence of NF200 in the early postnatal cerebellum In vivo phosphorylation studies indicated the presence of p hosphorylated NF subunits from P8 onwards, which was confirmed by stai ning in immunoblots by SM131, Immunohistochemical studies on Bouin's f ixed tissues revealed that in P0 cerebella, the deeper neurones (soma and processes) expressed all the NFP subunits while from P8 onwards th ey were negative for NF200. Similarly, Purkinje cells (soma) expressed transiently NF200 subunits on P8 and ceased to express them from P15 onwards. The white matter was immunopositive for NF200 and NF150 on P0 and the intensity of staining increased progressively. Astrocytes exp ressing GFAP were seen in cerebellar white matter from P8 onwards and the staining in radial glia could be detected from P15 onwards. The po lyclonal antibodies used in this study, recognize predominantly the ph osphorylated forms of NFP.