Induction by soluble factors of organized axial structures in chick epiblasts.

Inductive action of soluble factors was tested on isolated chick epiblasts. An assay was developed wherein conditioned medium derived from the Xenopus XTC cell line induced the formation of a full-length notochord and rows of bilaterally symmetric somites. Basic fibroblast growth factor, epidermal growth factor, retinoic acid, and transforming growth factor type B1 and B2 were not capable of inducing axial structures. Thus, soluble factors can elicit the development of polarity stored in the epiblast and behave as true morphogens since they can induce the formation of the organized complex structures that constitute the embryonic axis.