Fig. 3. Neural crest induction by Foxd3. (A-I) Electroporation of Foxd3^Myc (A-F) and Foxd3^IRES-EGFP (G-I) in neural tubes of stage 10 chick embryos. (A-C) Forty-eight hours after Foxd3^Myc electroporation (stage 22), widespread expression of Foxd3^Myc leads to ectopic expression of HNK-1 in one half of the trunk neural tube (A,B). Normally, HNK-1 is expressed only on migrating neural crest cells (arrow). At this stage, cells ectopically expressing Foxd3, HNK-1 (B) and Cad-7 (C) are seen migrating away from the neural tube (arrow). (D) Ectopic expression of HNK-1 is observed in the brachial neural tube of stage 18 embryos as early 24 hours after electroporation of Foxd3^Myc. (E,F) Delamination and migration of ectopic Foxd3^Myc+ cells is also observed at hindbrain levels of the neural tube (arrows). (G-I) Bright field images (G,H) of neural tubes electroporated with Foxd3^IRES-EGFP (I). (H,I) High magnification showing the delamination and emigration of Foxd3^Myc+ cells from the intermediate neural tube (arrows). fp, floor plate.