Fig. 4. Rescue of retinal patterning in the ace mutant by Fgf8-soaked beads. In 36-hour embryos, alkaline-phosphatase-tagged Epha3 protein detects nasal expression of Efna-ligands in the wild type (A), which is reduced in ace (C) and rescued after Fgf8-bead implantation at the 10-somite stage into the forebrain (D). Bead implantation also induces ectopic Efna-ligand expression in the ventronasal retina (asterisks in B,D). The sites of the beads are indicated by arrowheads. Images are flat-mounts of dissected eyes, orientation as indicated in A. (B,D) Digitally inverted images. D, dorsal; V, ventral; N, nasal; T, temporal.