Fig. 1. Fgf signaling is necessary for the induction but not maintenance of some otic placode markers. (A) A region of chick head between the first pair of somites and the midbrain was isolated from embryos between 0-8 ss and cultured as a chunk in collagen gel in the presence or absence of the Fgf receptor inhibitor SU5402. (B) Chunk cultures stained after 24 hours with antibodies to Pax2, Epha4 or Dlx3 or processed for in situ hybridization with a Bmp7 probe. Ectoderm positive for each marker is shown with an arrow; negative ectoderm is indicated with an arrowhead.