Fig. 5. Incomplete closure of the optic fissure in early retinal development produces a coloboma in the neonatal Fz5^-/- eye. (A,B) X-Gal-stained whole-mounts of (A) Fz5^lacZ/+;Sox2-CreER (Fz5^+/-) and (B) Fz5^CKO-AP/lacZ;Sox2-CreER (Fz5^-/-) mouse eyes at E13.5 as viewed from the back, showing failed optic fissure closure in the Fz5^-/- retina (red arrowheads). Green arrowheads indicate the optic nerve. (C,D) Vertical sections through the eyes shown in A,B. The red bracket in D (and H) demarcates the open ventral fissure. (E,F) Front view of X-Gal-stained eyes at E15.5. Note the tear-drop shape to the Fz5^-/- iris. (G,H) Vertical sections through the eyes shown in E,F. (I,J) P1 eyes showing the typical Fz5^-/- coloboma (arrowheads in J) and microphthalmia. (K,L) Anti-neurofilament (NF) immunostaining of whole-mount P1 retinas to visualize retinal ganglion cell axons. The optic disc is at the upper right (green arrowhead), and the open fissure is to the right in the Fz5^-/- retina (red arrowhead). Misdirected bundles of retinal ganglion cell axons are seen in the Fz5^-/- retina (white arrowheads). In all panels, dorsal is upward, as indicated in A (D, dorsal; V, ventral).