The molecular mechanisms necessary for remyelination by oligodendrocytes remain unexplored. We previously characterized a myelin basic protein promoter-lacZ (MBP-lacZ) transgene whose expression is regulated uniquely during development, and also in pathological situations, suggesting that it may be a useful reporter of molecular mechanisms during remyelination. As a first step toward creating a transgenic mouse model of remyelination, we cultured oligodendrocytes from these transgenic mice and showed that expression of MBP-lacZ appeared in parallel with a marker of oligodendrocyte maturation, galactocerebroside (GC). In addition, basic fibroblast growth factor blocked the expression of both MBP-lacZ and GC in these cells. Therefore, expression of MBP-lacZ reflects not only the developmental stage of oligodendrocytes, but also extrinsic influences on oligodendrocytes. These data suggest that MBP-lacZ may be a useful marker in transgenic mouse models of remyelination.