Figure 1. Optic cup labeling reveals a precise growth pattern for cells derived from the optic cup lip. A, B: Graphics of the labeling targets in the E3 optic cup, viewed as a wholemount (A) and transverse section (B). The crosshairs in A highlight orientation in all wholemount eyes: D-dorsal; V-ventral; N-nasal; T-temporal. In B, A-anterior (from lens), P-posterior (toward head) axis, specific for the eye, is indicated. The OCL (green dot) or optic cup (purple dot) was targeted around the circumference of the pupil. C-M: DiI labeled embryos: Embryos were imaged immediately after labeling (C-E) and following reincubation (F-M). The curved bars outline the boundary between the lens and optic cup. C, D: Dye targeted to the OCL (arrowhead). E: Dye targeted on the optic cup (arrowhead). F, G: OCL targeted embryos after 24 (F) and 48 (G) h reincubation. Labeled cells are present as a spoke-line extending from the OCL, adjacent to the lens, toward the posterior eye. The line highlights the extent of labeled cells. H, I: Resultant dye pattern 24 (H) and 48 (I) h after labeling the optic cup, as in E. Discrete patches of dye are found posterior to the OCL (arrow). The scattered dye is in the mesenchyme overlying the neuroepithelium. No linear labeling is found. J-M: Sections through the labeled tissue 48 h after targeting the OCL (J, K) or optic cup (L, M). J: After OCL labeling, the dye is retained in the OCL and is distributed through the anterior optic cup. K: A higher magnification of the boxed area in J. Dye is present in the inner and outer epithelial layers of the optic cup and in the overlying mesenchyme. L: After optic cup labeling, dye is found as a discrete patch in the posterior eye and is absent from the front of the eye. Some dye is present in the mesenchyme overlying the neuroepithelium (arrowheads). M: A higher magnification of the boxed area in L. Dye is present in both the neural retina and overlying retinal pigmented epithelium. Scale Bars: 100 µm. OCL; Optic Cup Lip, L; lens, NR; Neural retina, RPE; Retinal pigmented epithelium, CB; Ciliary body, IL; Inner layer, OL; Outer layer.