Neural induction - a bird's eye view

Since the discovery of the phenomenon of neural induction by Spemann and Ma ngold in 1924, considerable effort has been invested in identifying the sig nals produced by the organizer that are responsible for diverting the fate of cells from epidermal to neural. Substantial progress has been made only recently by the finding in amphibians that BMP4 is a neural inhibitor and e pidermal inducer, and that endogenous antagonists of BMPs ate secreted by t he organizer. However, recent results in the chick point to the existence o f other, upstream events required before BMP inhibition stabilizes neural f ates. Here we take a critical view of the evidence far and against the view that BMP inhibition is a sufficient trigger for neural induction in differ ent vertebrates.