Immortalized Hensen's node cells secrete a factor that regulates avian neural crest cell fates in vitro

The derivatives of the neural crest are regionally specified with respect to the anterior-posterior axis of the avian embryo. We have shown previously that young Hensen's node can act in vitro to regulate the expression of certain region-specific phenotypes in trunk neural crest cells. To study potential factors acting on the neural crest, we have generated an immortalized cell line from young Hensen's node. Here we show that a factor produced by these cells stimulates the expression of two cranial-specific phenotypes (fibronectin and smooth muscle actin) in trunk neural crest cells and decreases their expression of a trunk-specific phenotype (melanin). The active factor is a secreted protein with a molecular weight >30 kDa. Clonal studies suggest that the factor acts by changing the phenotypic fates of individual neural crest cells, rather than by selective effects on cell proliferation or survival. Previous work has shown that TGF-betas can mimic the effects of Hensen's node cells on neural crest differentiation. Results from the present study suggest that the factor in the conditioned medium of the immortalized node cell line is not a TGF-beta isoform. However, the cranial phenotype-inducing activity of the conditioned medium factor requires the presence of neural crest cell-derived TGF-betas.