Figure 3

Expression of musculoskeletal tissue marker genes in the head of crocodile embryos at stage 17. (A) Lateral view of the head of a crocodile embryo at stage 17. (B-D) Frontal sections prepared around the plane indicated by the red line in (A). (E-I) Frontal sections prepared around the plane indicated by the blue line in (A). (B and E) Expression of Runx2 is more concentrated to the precursors of dermatocranial elements, compared to the previous stages. (C, D, F, and G) Cranial muscular and cartilaginous tissues are clearly labeled by MyoD and Sox9 probes, respectively. (H and I) Expression domains of Scx and Six2 are indicated by arrowheads. The former is expressed in tendinous tissues accompanying cranial muscles and the latter is expressed mainly in connective tissue cells associated with cartilages of the jaw and the braincase. The red outlined domains in (B, D, E, G, H, and I) indicate the location of the pseudotemporal muscle deduced from adjacent sections where muscular tissues are labeled by MyoD probe. Green line in (A) indicates the plane where sections given in Figure 7D, E and F were prepared. Scale bar in (A) is 1 mm. Scale bars in (B-I) are 0.5 mm.