Reversal of a developmental restriction in neural crest-derived cells of avian embryos by a phorbol ester drug

Neural crest cells and some of the crest-derived cells of dorsal root ganglia (DRG) of early avian embryos give rise to pigment cells when placed in culture. DRG from older embryos, however, fail to do so under comparable culture conditions. This age-dependent loss of melanogenic ability might be explained either by (i) the death of a subpopulation of latent melanoblasts within early DRG, or (ii) the imposition of additional developmental restrictions in multipotent DRG cells. We show here that 12-O-tetradecanoylphorbol-13-acetate (TPA) causes some DRG cells to undergo pigmentation in cultures from older embryos, indicating that the loss of melanogenic ability in older embryos is not due to cell death. These pigment cells also display morphogenetic properties of normal melanocytes, including the ability to invade feather primordia. In addition to DRG, various other neural crest-derivatives contain cells similarly affected by TPA, including cells within sympathetic ganglia and peripheral nerves. We suggest that TPA reverses the developmental restriction of melanogenic ability that is normally imposed on neural crest-derived cells that migrate to various sites in avian embryos where melanogenesis does not normally occur.