Fig. 7

Nkx genes regulate SAN markers. (A-O) Ventral view, anterior towards the top, at 52?hpf. Dotted white lines illustrate the cardiac silhouettes. In situ hybridization for bmp4 (A-E), tbx2b (F-J) and hcn4 (K-O). Expression of bmp4 is restricted to the OFT (white arrow), AVC (yellow arrow) and IFT (black arrow) in wild-type (n=7/7) (A) and nkx2.5^+/+;nkx2.7^?/? (n=4/4) (B) embryos. However, its expression is expanded throughout the cardiac chambers in nkx2.5^?/?;nkx2.7^+/+ (n=3/4) (C), nkx2.5^?/?;nkx2.7^+/? (n=3/3) (D) and nkx2.5^?/?; nkx2.7^?/? (n=3/3) (E) embryos. Similar findings are observed in the wild-type (n=6/7) (F), nkx2.5^+/+;nkx2.7^?/? (n=3/4) (G), nkx2.5^?/?;nkx2.7^+/+ (n=3/3) (H), nkx2.5^?/?;nkx2.7^+/? (n=2/2) (I) and nkx2.5^?/?;nkx2.7^?/? (n=2/2) (J) embryos using the tbx2b probe, and in wild-type (n=8/8) (K), nkx2.5^+/+;nkx2.7^?/? (n=5/6) (L), nkx2.5^?/?;nkx2.7^+/+ (n=9/11) (M), nkx2.5^?/?;nkx2.7^+/? (n=3/3) (N) and nkx2.5^?/?;nkx2.7^?/? (n=3/3) (O) embryos using the hcn4 probe.