Figure 6

Expression of Bmp4 , Msx1 , and Msx2 in crocodile and turtle embryos at stage 15. (A-D) Frontal sections prepared around the plane indicated by the red line in Figure 2A. (E, F) Frontal sections prepared around the plane indicated by the blue line in Figure 2A. (G-J) Frontal sections prepared around the plane indicated by the red line in Figure 4A. (K, L) Frontal sections prepared around the plane indicated by the blue line in Figure 4A. (A and G) In both crocodile and turtle embryos, expression of Bmp4 is detected at the mesenchyme distributed in medial part of the jaw primordia (arrows). (B and H) Expression of Msx1 is detected at the mesenchyme that occupies the domain close to jaw articulation and lateral to quadrate and Meckel's cartilages (arrows). (C and E) In crocodile embryos, Msx2 is expressed in a thin layer of mesenchymal cells surrounding dorsal aspect of the brain and in a population of the mesenchyme that occupies the domain between ventrolateral part of quadrate cartilage and surface epidermis (arrows). (I and K) In turtle embryos, Msx2 is expressed in mesenchymal cells that populate lateral aspect of the head (arrows). In contrast to the condition in crocodile embryos, the ventral edge of Msx2-expressing mesenchymal layer is terminated ventral to the eye in turtle embryos and these cells cover MyoD-expressing jaw adductor muscle precursor (J and L) laterally. The red outlined domains in (A-C, and E) indicate the location of the anlagen of the pseudotemporal muscle deduced from adjacent sections where muscular tissues are labeled by MyoD probe. The red outlined domains in (G-I, and K) indicate the location of the anlagen of jaw adductor muscle. Scale bars are 0.5 mm.