Fig. 3. ß-gal staining pattern in [K14-Cre; R26R] embryos demonstrates the occurrence of epithelial-mesenchymal transdifferentiation during and after seam degeneration. (A) ß-gal staining in the anterior region of the palate at early E14.5, where the two shelves have just made contact. Note that the MEE cells were strongly labeled with ß-gal (arrowhead), but no signal was present in mesenchymal cells. (B) ß-gal staining in the middle region of the palate at early E14.5, where seam degeneration has just been initiated. Some epithelial-like ß-gal-positive cells have dissociated from the midline and migrated into the mesenchymal region (arrowhead). (C,D) ß-gal staining in the middle region of the palate at late E14.5, when seam degeneration is advanced. Both clump-like blue cells (arrowhead in C,D) and typical mesenchymal-looking blue cells (arrow in C,D) were observed in the mesenchymal region of the palate. (E) ß-gal staining in the fully fused palate at E15.5, showing that a high portion of the mesenchymal cells were ß-gal positive (arrow). Scale bars: 100 µm in A; 50 µm B-E.