Retinoic acid promotes the differentiation of adrenergic cells and melanocytes in quail neural crest cultures.

The neural crest (NC) generates very diverse neuronal and nonneuronal cell types in the vertebrate embryo. Pluripotency and plasticity of NC cells have been demonstrated, but the mechanisms whereby extrinsic factors control NC cell diversification are still unknown. Here we have investigated in vitro the influence of the morphogen retinoic acid (RA) in cultures of quail NC cells explanted at different developmental stages, when they start to migrate from the neural primordium, and when they reach their target organs. We found that addition of RA to mass cultures of early-migrating trunk NC promotes the differentiation of melanocytes and adrenergic cells. These responses are dose-dependent and vary according to the time of RA exposure. Testing RA effect on crest-derived cells located in Embryonic Day 3 (E3) somites and in E4 skin showed that the adrenergic-promoting action of RA is restricted to early-migratory cells, while melanogenic precursors colonizing the skin remain sensitive to RA for a longer period. Furthermore, analysis of cephalic and trunk NC clonal cultures revealed that RA influences the differentiation of cells when they are in a pluripotent state: among the progeny of isolated crest cells, RA specifically increases the number of the adrenergic cells, very likely by influencing their commitment; moreover, RA stimulates pigment synthesis in the melanoblasts. In conclusion, these results demonstrate that RA enhances in vitro the differentiation of NC cells and support a role for endogenous retinoids in the ontogeny of NC derivatives.