Fig. 5. Effect of ectopic Hoxa3 expression on facial development. At E6, quail-grafted control embryos develop a normal face (A) and show skeletal elements in the first branchial arch (B), consisting of Meckel’s, articular and quadrate cartilages (arrows). At E8, neural crest cells arising from untransfected diencephalic neural folds yield the entire facial and mandibular skeleton (C). By contrast, E6 embryos that have been engrafted with Hoxa3 transfected neural folds (D) show a reduced nasal bud (arrow) and fail to develop the first branchial arch (arrowheads). All the skeletal components of the mandibular bud are missing (E, arrowhead). At E8 (F), the nasal septum has developed rostral to the basipresphenoid and towards the top of the head. Although the posterior part of hyoid structure forms, in which the basihyal (Bh), ceratobranchial (Cb) and basibranchial (Bb) cartilages are recognizible, the lower jaw skeleton is completely absent. (G) At E7, in the forehead territory, telencephalic hemispheres are evidenced in which quail cells are identified as pericytes (H, arrows) of the neuroepithelium capillaries. At diencephalic level (I), the nasal septum that forms at the midline is of quail origin (Alcian Blue and QCPN mAb staining)(J). (K) Quail cells give rise to ciliary muscles and to the corneal endothelium. Bl, blood lacunae; Bs, basipresphenoid; Bv, blood vessel; Ce, corneal endothelium; Cm, ciliary muscle; Mc, Meckel’s cartilage; Ns, nasal septum. B,C,E,F are Alcian Blue stained embryos. Scale bars: 600 µm in G; 15 µm in H; 350 µm in I; 10 µm in J; 60 µm in K.