ALTERED 9-O ACETYLATION OF DISIALOGANGLIOSIDES IN CEREBELLAR PURKINJE-CELLS OF THE NERVOUS MUTANT MOUSE

Some gangliosides in the nervous system are developmentally down-regul ated, but many other gangliosides continue to be expressed in the adul t nervous system. We have previously demonstrated that the 9-O-acetyla ted gangliosides recognized by a monoclonal antibody, P-path, confer u nique compartmentation among Purkinje cell groups in the normal adult cerebellum. We have continued to explore the role of this group of gan gliosides in cerebellar organization by investigating the biochemical and cellular expression of this unique epitope in the cerebellum of th e mutant mouse, nervous, where postnatally, most Purkinje cells degene rate. Overall ganglioside composition of nervous cerebellum is similar to wild type cerebellum. However, quantitative analysis of gangliosid es by TLC-immunostaining shows that the relative concentration of 9-O- acetylated gangliosides varies considerably. In nervous cerebellum, th ere is more than a three-fold increase in the concentration of 9-O-ace tyl disialolactosyl ceramide (GD3), and 9-O-acetyl disialolactoneotetr aosyl ceramide (LD1) is decreased to 25% of wild type. In addition, GD 3 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 cerebell um. Thus, in nervous cerebellum the ratio of 9-O-acetyl GD3 to its dis ialoganglioside precursor is dramatically increased compared to wild t ype cerebellum In accord with the altered expression of 9-O-acetyl gan gliosides, immunoelectron microscopy demonstrates a change in the subc ellular distribution in mutant Purkinje cells. Instead of being associ ated with the somatic and dendritic membranes, P-path immunoreactivity is located internally, in the cytoplasm of Purkinje cell bodies and t heir dendrites. In addition to the changes in the cerebellum, the othe r regions of the brain decreased in size by about 15% in the nervous m utant. In the ganglioside composition of these regions of nervous brai n, 9-O-acetyl GD3 nearly doubled, but 9-O-acetyl LD1 and other ganglio sides did not differ. Our findings of significant changes in 9-0-acety lated gangliosides, accompanied by the overall decrease in brain size, suggest that carbohydrate or glycolipid metabolism is abnormal in the nervous mutant mouse brain.