Fig. 4. (A) Quantification of cell death in the Dlx1/Dlx2 mutant. At E13.5, there is a significant (asterisk) 3-fold increase in activated caspase-3-expressing cells in the mutant. This amount of apoptosis is less marked at E16.5 (cross), when there is a significant 66% increase in the number of apoptotic cells. There is no statistical difference in cell death by E18.5. (B-G) Co-localization of activated caspase-3 and BRN3b indicates that cell death is occurring among RGCs (D, box, insert) at E13.5 and at E16.5 (G, box, insert). Scale bars: 100 µm in D; 50 µm in G. Inserts in D and G represent 2-fold enlargements.