Fig. 5. Effect of localized overexpression of Wnt11 mRNA on neural crest migration. (A) One-cell stage embryos were injected with Wnt11 mRNA and FDX. At stage 9, the animal cap was dissected and cultured under a coverslip until the equivalent of stage 14. The ectoderm was grafted adjacent to the neural crest of a host embryo (stage 14), but into the neural plate side. Grafted embryos were cultured until stage 23-26, when neural crest migration was examined by Slug expression. Purple arrow indicates the normal migration of the neural crest cells. (B) Control side showing normal cephalic neural crest migration (dashed line), and the three streams of migration (black arrows). (C) Grafted side of the embryo shown in B. Note the inhibition in neural crest migration (dashed line and white arrows). The green arrowhead indicates the graft. (D,E) Sections from grafted embryos. Red bars indicate the ventral limit of neural crest migration; green arrowhead indicates the graft. (D) Graft of ectoderm injected with FDX; no effect on neural crest migration is observed. (E) Section of the embryo shown in B,C. Note the shorter distance of migration in the grafted side. The stronger signal in the grafted side is likely to be a consequence of all of the neural crest cells grouping in the dorsal region. Forty-five percent of embryos grafted with Wnt11-expressing cells showed inhibition of neural crest migration (n=26). (F) Similar experiment to the one described in A, but the Wnt11-expressing cells were grafted onto the normal pathway of neural crest migration. Grafted embryos were cultured until stage 26 when neural crest migration was examined by Slug expression. Purple arrow indicates the normal migration of the neural crest cells. (G-N) Anterior to the right. E, eye; dashed line indicates the limit of the graft; arrow indicates the migrating neural crest. (G,H,K,L) The operated (H,L) and control (G,K) sides of the same embryo are shown. (I,M) Sections of grafted embryos. (J,N) Summary of cephalic neural crest migration. Pink, branchial; blue, hyoid; purple, mandibular neural crest. Mixed colours indicate abnormal neural crest migration. The Wnt11-expressing graft is shown in green. Arrows indicate the proposed route of abnormal neural crest migration. (G-J) Control embryo that received an uninjected graft. (K-N) Embryos that received a Wnt11-expressing graft; 80% of the embryos with a Wnt11-expressing graft exhibited this phenotype, n=28.