Figure 2

Expression of musculoskeletal tissue marker genes in the head of crocodile embryos at stage 15. (A) Lateral view of the head of a crocodile embryo at stage 15. (B-D) Frontal sections prepared around the plane indicated by the red line in (A). (E-G) Frontal sections prepared around the plane indicated by the blue line in (A). (H) Frontal sections prepared around the plane indicated by the green line in (A). (B, E, and H) Runx2-positive mesenchymal cells are observed at the location where future dermatocranial elements are developed. (C and F) Expression of MyoD is detected at the cranial muscular tissues. (D and G) Cartilaginous tissues, including the braincase, quadrate, and Meckel's, are clearly labeled by Sox9 probe. The red outlined domains in (B, D, E, and G) indicate the location of the pseudotemporal muscle (ptm) deduced from adjacent sections where muscular tissues are labeled by MyoD probe. Scale bar in (A) is 1 mm. Scale bars in (B-H) are 0.5 mm.