Loss of Math5 alters the proliferation of retinal progenitors and causes the increased Math5 -lineage cells in cell cycle. Retinal sections from the control (top panels) and Math5-null (bottom panels) mice at the indicated developmental stages were immunolabeled with cell proliferation markers (red) BrdU (S-phase) or PH3 (M-phase) and anti-GFP (green). (A, B) At E13.5 to E15.5, GFP+/BrdU+ cells (arrows) are rarely detected in control retinas but are frequently seen in Math5-null retinas. (C, D) At P0 and P3, no visible GFP+/BrdU+ cells are found in the control and Math5-null retina, and the BrdU+ cells are profoundly decreased in Math5-null retinas. (E and F) PH3+ cells (red; arrowheads) are rarely seen as GFP+ cells in the control retina but in Math5-null retina, the GFP+/PH3+ cohorts (arrows) are significantly increased. (G) Quantification of the total BrdU+ or PH3+ cells per 350 μm length. (H) Quantification of the GFP+/BrdU+ or GFP+/PH3+ cells per retinal section. Scale bar equals 100 μm in A (applies to A, E and F), B (applies to B-D).