Figure 1.

Imaging osteogenesis in vivo: transgenic zebrafish lines highlighting chondrocytes and osteoblasts. (a) Skeletal structure of a zebrafish at 5 weeks post fertilization (w.p.f.). Scales were removed and the bone stained with alizarin red. (b) Ventral view of the Meckel's cartilage (red) and abutting osteoblasts (green) in a 6 d.p.f. embryo expressing col2a1:mCherry;osterix:GFP. Mk, Meckel's cartilage; mx, maxilla; d, dentary; pq, palatoquadrate; ep, ethmoid plate. (c) Magnification of the developing operculum in a 6 d.p.f embryo expressing osterix:gal4;UAS:GFP. Note that the osteoblasts (green) are placed distally to the mineralized matrix they produce. (d) Vertebral column of a 5 w.p.f. transgenic zebrafish showing expression of cathepsin K, a marker for osteoclasts, in green. Inset: magnification of a hypural bone with osteoclasts in close proximity to the bone surface.