Oligodendrocytes synthesize dramatic amounts of myelin membrane. We hypothesized that this requires unique aspects of vesicular trafficking. Specific stages of the oligodendrocyte lineage were assayed for low molecular weight GTP-binding proteins implicated in the regulation of vesicular transport pathway (two dimensional gel electrophoresis, [alpha-32P]GTP overlay). Consistent with the hypothesis, as oligodendrocytes differentiate from early progenitors to mature myelin-producing cells, > or = 12 small GTP-binding proteins become up-regulated. Myelin membrane also has a complex pattern of GTP-binding proteins. Several of these proteins may be specific to oligodendrocytes, suggesting that oligodendrocytes may utilize cell-type specific GTP-binding proteins for biogenesis and maintenance of the myelin membrane.