Effects of the BMP inhibitor dorsomorphin on bone mineralization. Alizarin red staining of 5 dpf larvae treated at 2, 3 or 4 dpf during 24 h with 100 µM dorsomorphin. Control embryos were treated with DMSO. Embryos treated at 2 dpf (B lateral view and D ventral view) show severe reduction of all mineralized bone pieces compared to the controls (A lateral view and C ventral view). The treatments starting at 3 dpf (F in ventral view) and 4 dpf (H in ventral view) lead to a reduction of bone mineralization, but to a lesser extent than at 2 dpf compared to the controls embryos (respectively E and G in ventral view). c: cleithrum; en: entopterygoid; o: operculum; p: parasphenoid. Scale bar: 200 µM.

Effects of the specific BMP inhibitor K02288 on bone mineralization. Alizarine red staining of 5 dpf larvae previously treated at 2 (B,D) or 3 dpf (F) during 24 h with K02288 10 (B) and 20 µM (D,F). Control embryos (A,C,E) were treated with DMSO. c: cleithrum; en: entopterygoid; o: operculum; p: parasphenoid. Scale bar: 200 µM.

(A–D) Effects of BMP inhibitor treatment at 2–3 dpf on cartilage formation. Alcian blue staining of 5 dpf larvae previously treated at 2 dpf during 24 h with 100 µM dorsomorphin (B) or 20 µM K02288 (D). Control embryos (A,C) were treated with DMSO; (E–H) In situ hybridization using the sox9a probe. No difference in cartilage formation was observed between control (E,G) and treated (F,H). cb 1–4: ceratobranchial ray 1 to 4; ch: ceratohyal; mk: Meckel’s cartilage. Scale bar: 200 µM.