Fig. 6. Cooperation of FGF and BMP and WNT antagonists to induce the pre-placodal region. Misexpression of SMAD6 and Crescent (A-D, brown in B,D) leads to an expansion of Six4 (A,B; blue) and Eya2 (C,D; blue) expression into the extra-embryonic epiblast. (E-G) FGF8 induces ectopic Sox3 (E, arrowhead), Dlx5 (F, arrowhead) and Eya2 (H, arrowhead), but not Six4 (G, arrowhead). Misexpression of SMAD6, Crescent and FGF8 (I-P) results in ectopic induction of Six4 (I,J; blue) in the absence of the neural marker Sox2 (M,N) and of the heart mesoderm marker Nkx2.5 (O,P). When the FGF8 bead is replaced with an SU5402 bead after 5 hours (K,L), induction of Six4 expression is still observed. Brown staining in J,L,N,P represents immunostaining with anti-GFP antibody to visualise electroporated cells. (Q-T) Head mesoderm (brown in R,T) was grafted into the extra-embryonic region together with control (Q,R) or SU5402-coated beads (S,T). Six4 expression (blue) is induced in controls (Q,R), but not when FGF signalling is inhibited (S,T). Quail grafts are labelled using QCPN antibody (brown in R,T).