Figure 4. Distribution of mitotically active cells. DNA synthesis was 
determined in a normal 18-week-old CAG-EGFP cornea (A,B) and a 20-week-old 
GFP-Dstncorn1  cornea (C,D). Animals were labeled with systemic BrdU for 24 h continuously with an osmotic pump. BrdU positive cells were determined by immunohistochemistry with whole mount corneas and basal epithelial cells imaged (A,C). DAPI stain shows the entire population of basal epithelial cells of the same area (B,D). Bar: 50 µm.