Basic Fibroblast Growth Factor (bFGF) acts intracellularly to cause the transdifferentiation of avian neural crest-derived Schwann cell precursors into melanocytes

We previously found that cultured neural crest-derived cells from embryonic quail peripheral nerves, which consist mostly of Schwann cell precursors, gave rise to melanocytes following treatment with basic fibroblast growth factor (bFGF) or 12-O-tetradecanoyl phorbol-13-acetate (TPA). Here, we show that antisense deoxyoligonucleotides targeted against two regions of the bFGF mRNA transcript blocked this TPA-induced transdifferentiation of Schwann cell precursors. Neither sense nor scrambled antisense control oligonucleotides had any effect in this regard. TPA increased bFGF protein expression in cell lysates but not in conditioned media from these cultures, and this expression was localized to the nucleus and cytoplasm. Furthermore, bFGF-neutralizing antibodies and inositolhexakisphosphate (InsP₆) both inhibited pigmentation caused by exogenous bFGF, but had no affect on TPA-induced melanogenesis, suggesting that bFGF is not released by these cells. These data indicate that bFGF is necessary for the TPA-induced transdifferentiation of Schwann cell precursors into melanocytes and that bFGF acts via an intracrine mechanism.