[Molecular diversity of brain ganglioside and its biological significance]

Gangliosides are sialic acid containing glycosphingolipids found in highest concentrations in central nervous tissues (CNS). More than 100 species of gangliosides including extremely minor components exist in CNS tissues. We have developed a new method using Q-Sepharose to efficiently purify them from complex mixtures of bovine brain gangliosides. Among the isolated gangliosides a unique new series of gangliosides was shown to exist in the polysialoganglioside fraction. They possessed N-acetylneuraminic acid attached to N-acetylgalactosamine in alpha 2-6 linkage. The immunohistochemical staining of human and rat brains with specific monoclonal antibody to the gangliosides showed that they are stained intensely the neuropile of dorsal horn on spinal cord, being presumably expressed on the cholinergic nerve terminals. On the basis of these observations, extremely minor species may play significant roles in CNS. The present data also indicated that brain tissues contain a new type of alpha 2-6 sialytransferase to act on GalNAc in the gangliotetraose structure.