It is not yet clear which FGFR type, or types, mediates the effect of endogenous FGF2 in the context of demyelination and remyelination. Differential effects of FGF2 at different stages of the oligodendrocyte lineage may occur through differential expression and activation of FGFR isoforms (43) . Oligodendrocyte lineage cell expression of high-affinity FGFRs and coreceptors varies with developmental stage and FGF2 exposure (44) . Furthermore, expression of multiple FGFR types is significantly increased in response to demyelination (19) . FGF2 may also have differential effects based on changing interactions with other signaling pathways that regulate oligodendrocyte lineage differentiation and myelination such as Notch1 (45, 46) and neuregulin (47, 48) . Interpreting a direct effect of FGF2 is complicated because neurons and glial cells express multiple FGFR types within and near demyelinated lesions (19) . Therefore, future studies will be required to identify the specific signaling components mediating endogenous FGF2 signaling in the in vivo context of demyelination and remyelination.