Figure 5

Expression of musculoskeletal tissue marker genes in the head of turtle embryos at stage 17. (A) Lateral view of the head of a turtle embryo at stage 17. (B-F) Frontal sections prepared around the plane indicated by the blue line in (A). (B) Runx2-positive mesenchymal cells (arrows) are broadly distributed at the lateral portion of the head, from the top of the head to the ventral margin of the first pharyngeal arch derivative. (C) Cranial muscular tissues are clearly labeled by MyoD probe. (D) Cartilaginous tissues, including the braincase and quadrate, are clearly labeled by Sox9 probe. (E) Scx is expressed in tendinous tissues at the periphery of external adductor muscle (ame) (arrowheads) and in the bodenaponeurosis (boap. central tendon of jaw adductor muscle). (F) Six2 is expressed mainly in connective tissue cells associated with cartilages of the braincase and quadrate, as well as in connective tissue cells within jaw muscles (arrowheads). Note that the external adductor muscle (red outlined domain) is covered by a thick layer of Runx2-positive mesenchyme laterally. Scale bar in (A) is 1 mm. Scale bars in (B-F) are 0.5 mm.