Fig. 4. Ablation of RALDH3 alters development of the ventral periocular mesenchyme. (A,D) Frontal histological sections through the head of E12.5 wild-type (A) and Aldh1a3-null (D) fetuses. (B,E) Distribution of apoptotic cells (assessed by TUNEL assays) in E10.5 wild-type (B) and Aldh1a3-null (E) fetuses. (C,F) Whole mount in situ hybridization with a digoxigenin-labeled Eya2 antisense riboprobe on E11.5 wild-type (C) and Aldh1a3-null (F) fetuses. Note that the histological sections illustrated have been selected to provide the best match between mutant and wild-type embryos. Arrows indicate the optic nerve exit point; red brackets indicate the periocular mesenchyme. d, dorsal retina; e, eye cup; f, forebrain; g5, ganglion of the Vth nerve; le, lens or lens placode; v, ventral retina. Scale bar in D: 80 µm for A,D; 25 µm for B,E.