Fig. 7. fgf8 or fgf3 can induce expression of val and krox-20. (A) Embryo (14 s) with FGF8 bead (arrow). val (blue) and krox-20 (red) are induced in ectoderm adjacent to the bead, shown magnified in B. (C) Embryo (12 s) with FGF8 bead next to the caudal hindbrain, showing ectopic val (blue) and krox-20 (red). (D) Embryo (6 s) with fgf8-expressing cells (red, arrowhead) in r5. Ectopic krox-20 expression (blue, arrow) is induced in r6-r7. Seven out of 43 heat-shocked embryos showed ectopic krox-20 expression in the caudal hindbrain with nearby fgf8-expressing cells. (E) Embryo (6 s) with fgf8-expressing cells (red, arrowheads) in r6 and in ectoderm overlying r6-r7. Ectopic val (blue, arrow) spreads caudally into r7. Twelve out of 34 heat-shocked embryos showed ectopic val expression in the caudal hindbrain with nearby fgf8-expressing cells. (F) Embryo (6 s) with fgf8-expressing cells (red, arrowheads) in the midbrain and rostral hindbrain. val expression is not affected (blue). (G-G'') Embryo (8 s) with FGF3-Myc-expressing cell (arrowhead in G) in ectoderm overlying r5. Ectopic val spreads caudally into r7 (arrow in G') and ectopic krox-20 spreads caudally into r6 (arrow in G''). Ten out of 36 heat-shocked embryos showed ectopic val and krox-20 expression in the caudal hindbrain with nearby FGF3-expressing cells. Dorsal views show anterior towards the left. Scale bars: in A, 100 µm for A; in B, 50 µm for B,G-G''; in C, 50 µm for C; in D, 50 µm for D-F.