Expression patterns of bmp16 in zebrafish embryos. In situ hybridization at 24 (A-D), 36 (E, F, H, I), 52 (G) and 72 hpf (J) and at 5 dpf (K, L). All pictures except I (islet-1 [isl-1]) show expression of the zebrafish bmp16. (A) A lateral view with expression signals in a crescent-shaped region of the tail bud mesenchyme. (B, C) Transverse sections at the levels indicated in A, showing signals in the neural keel (nk) and the neural rod (nr), respectively. (D, E) Lateral views showing bmp16 expression (arrowheads) in the developing heart. (F) A lateral view focusing on the expression signals in the apical ectodermal fold of the pectoral fin bud (arrowhead). (G) A dorsal view of the expression domain in the developing swim bladder (arrowhead) at 52 hpf. (H) A dorsal view of the developing swim bladder (arrow) and the pectoral fin buds (arrowheads). (I) A dorsal view of the same region as in H, showing isl-1 expression in a more caudal region (numbers indicate somite counts). (J) A lateral view of the two distinct expression domains (arrowheads), of which the caudal one marks the developing swim bladder in a 72 hpf embryo. (K) A lateral view of a 5 dpf embryo with bmp16 expression signals (arrowheads). (L) A transverse section of the embryo shown in K with expression signals in the gut epithelium (g) and swim bladder (sb). The section was prepared by manually cutting the embryo using a razor blade. Other abbreviations: g, gut; mff, median fin fold; nk, neural keel; nr, neural rod; nt, neural tube; sb, swim bladder. Scale bar: 50 μm.