Fig. 3. Axons projecting from Brn3c-expressing cells in retinal explants. (A) Weak AP activity detected in axons projecting from a Brn3c (AP/+) retinal explant. (B) AP activity was twice as intense as in A in axons projecting from a Brn3c (AP/AP) retinal explant. (C,D) DIC images of A and B, respectively, showing abundant axons emanating from both of the retinal explants. (E) AP expression in neurites and migrating cells from a Brn3b (AP/AP) retinal explant. (F) Lack of AP expression in neurites and migrating cells from a Brn3b (GFP/GFP):Brn3c (AP/AP) double mutant retinal explant. Arrows point to nonexpressing neurites. (G) AP expression in neurites (arrows) within the tissue body of Brn3b (GFP/GFP):Brn3c (AP/+) retinal explants. (H) AP expression in Brn3c-expressing cells (arrowheads) within the tissue body of a Brn3b (GFP/GFP):Brn3c (AP/AP) double mutant retinal explant.