Fig. 6. Gene expression analysis at E6 in BA1 grafted with QT6-Shh cells: cell differentiation. (A) Facial view of a grafted E6 chick embryo showing caudal mandibular bud (Md) extension in the grafted side (arrow). (B-G) Frontal serial sections proximodistally at the level of the Mds. (B,B') Bmp4 expression in the distal ectoderm and mesenchyme of the ectopic Md. (C,C') Col2a1 expression indicates an extra Meckel's cartilage (arrow) near the Bmp4 zone of expression. (D,D') Cbfa1 transcripts are present in the mesenchyme of normal and ectopic Mds close to the Bmp4 domain and around Col2A1-expressing Meckel's cartilage anlage. (E) Distal region of the extra Md with a faint expression of Shh in the ectoderm (arrow). (F) Nerve fibers immunostained with HNK1 mAb close to the ectopic Meckel's cartilage (arrows; see outlines in B' and C'). (G) Frontal section in Md proximal half, in the grafted side, shows an extension of muscle (MyoD expression) and HNK1+ nerves (square enlarged in G'). (G') MyoD expression is associated with nerve (HNK1 immunostaining). Scale bar: 500 µm in B-G.