Fig. 5. Gene expression analysis at E5 in BA1 grafted with QT6-Shh cells. (A-C) Frontal sections from distal (A) to half-proximal (B,C) regions of E5 mandibular buds (Mds). (A,B) Bmp4 is strongly expressed in the caudal-most ectoderm in the QT6-Shh grafted side (arrow) as in the rostral ectoderm of the Md, where it is normally expressed (arrowheads). (C) Sox9 expression is caudally extended in the mesenchyme of the grafted Md. Mx, maxillary bud. (D) Facial view of a grafted embryo at E5 with the location (double-headed arrow) of a series of transverse sections (E-I) indicated according to the proximodistal axis of the Mds. (E) Shh expression shows the grafted QT6-Shh cells (arrow) in the proximal region close to the oral endoderm expressing Shh. Very few Shh-producing cells are found in the distal mesenchyme (arrowhead). (F) Col2a1 expression shows expansion of Meckel's cartilage (proximal part and induced branch) in the grafted side (arrows). The arrowhead indicates tongue cartilage. (G) Bmp4 transcripts are present in the tip of the tongue mesenchyme (arrowhead) and in the Md distal ectoderm and mesenchyme in the experimental side (arrows). (H,I) Dlx5 and Pitx1 expressions are extended distally and show a colocalization with Bmp4 in the mesenchyme in close contact with lateral ectoderm (arrows). Scale bar: 500 µm in A-C,E-I.