Figure 7

Expression of Bmp4 , Msx1 , and Msx2 in crocodile and turtle embryos at stage 17. (A-C) Frontal sections prepared around the plane indicated by the blue line in Figure 3A. (D-F) Sections prepared around the plane indicated as the green line in Figure 3A. (G-I) Sections prepared around the plane indicated as the red line in Figure 5A. (J) Section prepared around the plane indicated as the blue line in Figure 5A. (A, D, and G) In both crocodile and turtle embryos, expression of Bmp4 is detected in the epithelium of the cochlear canal, the mesenchyme surrounding the eye, and the mesenchyme distributed in medial part of the jaw (arrows). (B, E, and H) Expression of Msx1 is detected at the mesenchymal cells that later differentiates into quadratojugal bone (qj) and in a thin layer of mesenchymal cells that covers brain dorsally (arrows at the top of E and H), as well as in the epithelium of the cochlear canal. (C and F) In crocodile embryos, expression of Msx2 is detected at a population of mesenchymal cells in close proximity of postorbital and quadratojugal bones, as well as in a layer of the mesenchyme surrounding the brain dorsally where future a pair of parietal bones are developed. (I and J) In turtle embryos, Msx2 was expressed in a thick layer of mesenchymal cells that populate lateral aspect of the head (arrows). The Msx2-positive mesenchymal cells cover the external adductor muscle precursors (red outlined domains in G- J) laterally. The red outlined domains in (A-F) indicate the location of the pseudotemporal muscle deduced from adjacent sections where muscular tissues are labeled by MyoD probe. The blue outlined domains in (A-J) indicate the location of quadrate cartilage deduced from adjacent sections where cartilaginous tissues are labeled by Sox9 probe. Scale bars are 0.5 mm.