(A-A″) Egfp-expressing mesenchymal cells from the anterior palate, when grafted to the anterior region of an explanted wild-type palatal shelf, exhibit a directional migration towards to the lateral side after 24 hours. Arrows indicate the migrating cells. (B-B″) Egfp-expressing mesenchymal cells from the posterior palate, when grafted to the posterior region of an explanted wild-type palatal shelf, show a directional migration towards the anterior end after 24 hours. (C-C″,D-D″) Directional migration by the Egfp-expressing cells is not observed when these cells are grafted to either the anterior (C-C″) or the posterior (D-D″) palatals shelves from Wnt5a mutants.