Misexpression of tfap2a promotes overproduction of placodes. A-L, Markers of placodal derivatives, including pitx3 in the anterior pituitary at 30 hpf (A and B, arrows), cxcr4b in the olfactory pit at 24 hpf (C and D, circled), Isl1 in trigeminal placode at 14 hpf (E and F), isl1 in cranial ganglia at 30 hpf (G and H, trigeminal ganglion indicated by arrows), pax2a in the otic/epibranchial placodes at 14 hpf (I and J, brackets indicate otic domain), and the otic vesicle at 30 hpf (K and L) in control embryos and hs:tfap2a/+ transgenic embryos. All indicated placodal derivatives are enlarged following activation of hs:tfap2a at 7 hpf. M–T, expression of competence factors tfap2c (M and N), foxi1 (O and P) and gata3 (Q and R, otic domain indicated by brackets) at 14 hpf, and the general PPE marker dlx3b at 11 hpf (S and T) in control embryos and hs:tfap2a embryos. Activation of hs:tfap2a at 7 hpf results in upregulated and expanded expression of all of these genes in placodal tissues. Images show lateral views with anterior to the left (C, D, G-L), dorsal views with anterior up (E, F, M-T), or facial views of the front of the head (A and B).