level of BMP activity is required to induce the neural plate border, including placodes and neural crest cells, that in this border the iro1 geneis activated, and that this activation is required for the specification of the placodes.

Cranial placodes are discrete regions of thickened epithelium that form in characteristic positions in the head of vertebrate embryos. They contribute to the formation of nose, eyes, ears, lateral line, and cranial sensory gangli