Fig. 1. Ectopic axis induction by FoxD3. (A) Control. At the four-cell stage a single ventral blastomere was injected with FoxD3 RNA (100 or 300 pg). Ectopic anterior axial structures, including ectopic eyes, were induced at the high dose (B) and ectopic tails were induced at the low dose (C). Embryos were analyzed at stage 35 by serial-section immunocytochemistry to detect muscle (12/101) (D), notochord (Tor70) (E) and neural tube (4d) (F) (transverse sections, dorsal up; arrowheads indicate stained tissues). Embryos were also analyzed at the early gastrula stage (stage 10.25) by whole-mount in situ hybridization for the expression of Goosecoid (G,H). FoxD3 induced ectopic Goosecoid expression (H) (vegetal views, dorsal up; arrowheads indicate dorsal blastopore lip and arrows indicate region of ectopic gene expression).