Neural crest induction by paraxial mesoderm in XXXX embryos requires FGF signals.

@entity72898 @entity66022 @entity1238 @entity53945 @entity29293 @entity29291 @entity1573 @entity1274 @entity72899 @entity62828
At the border of the neural plate, the induction of the neural crest can be achieved by interactions with the epidermis, or with the underlying mesoderm. Wnt signals are required for the inducing activity of the epidermis in @entity1573 and amphibian embryos. Here, we analyze the molecular mechanisms of neural crest induction by the mesoderm in @entity1238 embryos. Using a recombination assay, we show that prospective paraxial mesoderm induces a panel of neural crest markers ( @entity62828 , FoxD3, @entity72898 and @entity66022 ), whereas the future axial mesoderm only induces a subset of these genes. This induction is blocked by a dominant negative (dn) form of @entity53945 . However, neither dnFGFR4a nor inhibition of Wnt signaling prevents neural crest induction in this system. Among the FGFs, @entity72899 is strongly expressed by the paraxial mesoderm. @entity72899 is sufficient to induce the neural crest markers FoxD3, @entity66022 and @entity72898 transiently in the animal cap assay. In vivo, @entity72899 injections also expand the @entity62828 expression domain. This suggests that @entity72899 can initiate neural crest formation and cooperates with other DLMZ-derived factors to maintain and complete neural crest induction. In contrast to Wnts, @entity29293 or @entity29291 , @entity72899 elicits neural crest induction in the absence of mesoderm induction and without a requirement for BMP antagonists. In vivo, it is difficult to dissociate the roles of FGF and WNT factors in mesoderm induction and neural patterning. We show that, in most cases, effects on neural crest formation were parallel to altered mesoderm or neural development. However, @entity1274 patterning can be dissociated experimentally using different dominant-negative manipulations: while Nfz8 blocks both posterior neural plate formation and neural crest formation, dnFGFR4a blocks neural patterning without blocking neural crest formation. These results suggest that different signal transduction mechanisms may be used in neural crest induction, and anteroposterior neural patterning.
