Altered 9- O acetylation of disialogangliosides in cerebellar Purkinje cells of the nervous mutant mouse

Abstract

Some gangliosides in the nervous system are developmentally down-regulated,d but many other gangliosides continue to be expressed in the adult nervous system. We have previously demonstrated that the 9- O-acetylated gangliosides recognized by a monoclonal antibody, P-path, confer unique compartmentation among Purkinje cell groups in the normal adult cerebellum. We have continued to explore the role of this group of gangliosides in cerebellar organization by investigating the biochemical and cellular expression of this unique epitope in the cerebellum of the mutant mouse, nervous, where postnatally, most Purkinje cells degenerate. Overall ganglioside composition of nervous cerebellum is similar to wild type cerebellum. However, quantitative analysis of gangliosides by TLC-immunostaining shows that the relative concentration of 9- O-acetylated gangliosides varies considerably. In nervous cerebellum, there is more than a three-fold increase in the concentration of 9- O-acetyl disialolactosyl ceramide (GD3), and 9- O-acetyl disialolactoneotetraosyl ceramide (LD1) is decreased to 25% of wild type. In addition, GD3 ganglioside, the immediate precursor of 9- O-acetyl GD3, is detected at 1/3 of the level of wild type cerebellum, and LD1 ganglioside, the precursor of 9- O-acetyl LD1, is virtually absent from nervous cerebellum. Thus, in nervous cerebellum the ratio of 9- O-acetyl GD3 to its disialoganglioside precursor is dramatically increased compared to wild type cerebellum. In accord with the altered expression of 9- O-acetyl gangliosides, immunoelectron microscopy demonstrates a change in the subcellular distribution in mutant Purkinje cells. Instead of being associated with thesomatic and dendritic membranes, P-path immunoreactivity is located internally, in the cytoplasm of Purkinje cell bodies and their dendrites. In addition to the changes in the cerebellum, the other regions of the brain decreased in size by about 15% in the nervous mutant. In the ganglioside composition of these regions of nervous brain, 9- O-acetyl GD3 nearly doubled, but 9- O-acetyl LD1 and other gangliosides did not differ. Our findings of significant changes in 9- O-acetylated gangliosides, accompanied by the overall decrease in brain size, suggest that carbohydrate or glycolipid metabolism is abnormal in the nervous mutant mouse brain.