The embryonic brain is rich in acidic, sugar containing lipid molecules, sialoglycosphingolipids, or gangliosides. Formation of axonal and dendritic processes in the developing neuron requires delivery of plasma membrane elements containing gangliosides of a special higher molecular type. It is not known how trafficking of plasma membrane gangliosides takes place during the crucial initial post-mitotic developmental period of the neuron when processes are being elaborated. This issue will be investigated using a convenient system of early chick telencephalic neurons cultured under defined conditions in which synchronous outgrowth of neurites are induced by epidermal growth factor, EGF. The mechanisms involved in the modification of gangliosides contained in the membranes of coated vesicles that are taken up into the neuron following EGF stimulation will be studied. The hypothesis that ecto-sialotransferase activity is involved in alteration of the ganglioside, GD3, in such a way as to provide matrix attachment and neurite extension capability to the plasma membrane will be investigated. These studies promise to provide fundamental information on ganglioside biosynthesis and function in brain development.
