STUDIES ON A CEREBELLAR 50,000-DALTON PROTEIN ASSOCIATED WITH CEREBELLAR HYPOPLASIA IN JAUNDICED GUNN-RATS - ITS IDENTITY WITH GLIAL FIBRILLARY ACIDIC PROTEIN AS EVIDENCED BY THE IMPROVED IMMUNOBLOTTING METHOD

Since a 50,000-dalton protein (GR-50) shows a marked increase in the hypoplastic cerebellum of jaundiced homozygous Gunn rats and its electrophoretic behavior is similar to that of glial fibrillary acidic protein (GFAP), GR-50 was identified as GFAP by 2-dimensional electrophoresis of rat cerebellar membrane proteins using an improved immunoblotting method. A blot immunostained for a specific antigen was also visualized for other proteins, thereby enabling more precise localization of the antigen on the blot. GFAP antigen occupied exactly the same position as GR-50 on the blot, suggesting strongly the identity of both proteins. Immunohistochemical studies revealed that in the cerebellum of homozygotes compared with that of heterozygotes GFAP antigen was greatly increased and that it was especially rich in the homozygous rat cerebellar lobules with a high degree of hypoplasia. Not only the fibers of the Bergmann glial cells but also their somata were intensely immunostained in the affected lobules. A 47,000-dalton protein (SG-47), which is increased in staggerer mutant mice with cerebellar hypoplasia, also immunoreacted with the antiserum to GFAP.