Bmp4 induces hand2 and msxe expression in the absence of Edn1. (A-P) Confocal sections of 36 hpf in situ hybridizations for hand2 (green) with dlx3b (red, A-H) or msxe (red, I-P) in control hsp70I:Gal4 (A,I), edn1-/- mutant (E,M), UAS:Bmp4 (B-D,J-L) and edn1-/-; UAS:Bmp4 (F-H,N-P) embryos. Increasing periods of Bmp4 heat-shock induction [1 minute at 21 hpf (B,F,J,N), 3 minutes at 21 hpf (C,G,K,O) and 4 hours from 20-24 hpf (D,H,L,P)] resulted in progressive recovery of hand2 and msxe but not dlx3b expression in edn1-/- mutants. Consistent phenotypes were observed for the following: (A) n=55, (B) n=31, (C) n=15, (D) n=9, (E) n=8, (F) n=3, (G) n=4, (H) n=1, (I) n=37, (J) n=11, (K) n=6, (L) n=9, (M) n=20, (N) n=2, (O) n=3 and (P) n=2. Scale bar: 50 μm.