Fig. 4. FGF2-mediated oligodendrocyte induction is dependent on MAP kinase signalling and is inhibited by BMP4. (A) Isolated E14 rat dorsal spinal cord cultures were examined for expression of oligodendrocytes (O4), astrocytes (GFAP), neurones (ß-tubulin) and smooth muscle actin (SMA) at 4-days post-plating, following exposure to FGF2 and BMP4 (0.1-10 ng/ml), MEK inhibitor (UO126) or PI3K pathway inhibitor (LY294002). BMP-treated cultures show a dose-dependent reduction of oligodendrocytes and astrocytes, and an induction of SMA. UO126-treated cultures show a similar reduction in oligodendrocytes (^*=P<0.01; ^**=P<0.05). (B) Immunomicrograph showing oligodendrocyte (O4) and astrocyte (GFAP) generation following 96 hours of (I) FGF2 and (II) FGF2 + BMP4 (10 ng/ml) treatment of E14 dorsal cultures. BMP4-treated cultures have no oligodendrocytes and reduced numbers of astrocytes following differentiation in control media after withdrawal of 4-day FGF2 and BMP4 treatment; compare with cultures treated with FGF2 alone. Immunomicrographs showing (III) neuronal (ß-tubulin) generation following FGF2 stimulation of E14 dorsal cultures, and (IV) smooth muscle actin-positive staining cells derived from FGF2 and BMP4 (10 ng/ml) treated cultures.