Identification of disialosyl paragloboside and O-acetyldisialosyl paragloboside in cerebellum and embryonic cerebrum.

The lacto series of glycolipids are only minor constituents in mammalian CNS and are found mostly during development. Expression of a significant amount (70 micrograms of neuraminic acid/g dry weight) of disialosyl-lacto-N-neotetraosylceramide (LD1) in adult mouse cerebellum is reported for the first time in the nervous system. The structure of this ganglioside was determined by hydrolysis with various glycosidases, immunochemical tests, sugar and fatty acid analyses after permethylation and capillary GLC-mass spectrometry, sugar linkage analysis of permethylated alditol acetates, and fast-atom bombardment-mass spectrometry of the native ganglioside. The structure of LD1 was determined to be NeuAc-NeuAc alpha 2-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1-ceramide. The major fatty acid was 18:0, and the long-chain base was C18-sphingenine. Mouse cerebellum also contained O-acetyl-LD1 and several other O-acetylated gangliosides as recognized by monoclonal antibodies ME311 and 3G5. The levels of LD1 and O-acetyl-LD1 in cerebellum increased during postnatal development. During development of the Purkinje cell degeneration mutant, pcd/pcd, the levels of both of these gangliosides in the cerebellum declined with the loss of Purkinje cells, a finding indicating that these gangliosides are primarily associated with Purkinje cells. In the cortex, LD1, O-acetyl-LD1, and O-acetyl GD3, like GD3, are developmentally regulated antigens and are only expressed in the fetal cortex and not to any significant extent in the adult.