Clonal expansion of WT RPCs in the p15 ⁺ retinae is not due to apoptotic signals. (A) Whole mount GFP immunostaining (green) and TUNEL assay (magenta with yellow arrowheads) of 28-hpf p15⁺ host retinae transplanted with gfp-expressing WT (n = 10) donor RPCs or p15⁺ (n = 11) donor RPCs. Schematic inserts show TUNEL signals (magenta) in p15⁺ host RPCs (gray) in the presence of WT donor RPCs or p15⁺ donor RPCs (green). In each group, zoom-in images of retinal areas (dashed yellow rectangles) at the merged and three separate channels are shown in the right panels. (B) The ratio of the number of GFP−TUNEL+ (GFP negative and TUNEL positive) nuclear fragments in p15⁺ host RPCs to the total number of GFP− (GFP negative) p15⁺ host RPCs in the presence of WT donor RPCs or p15⁺ donor RPCs. (C) Whole mount GFP immunostaining (green) and TUNEL assay (magenta with yellow arrowheads) of 28-hpf p15⁺ (n = 10) and p15⁺/bcl2a⁺ (n = 12) host retinae transplanted with gfp-expressing WT donor RPCs. Schematic inserts show TUNEL signals (magenta) in p15⁺ and p15⁺/bcl2a⁺ host RPCs (gray) in the presence of WT donor RPCs (green). In each group, zoom-in images of retinal areas (dashed yellow rectangles) at the merged and three separate channels are shown in the right panels. (D) The ratio of the number of GFP−TUNEL+ nuclear fragments in p15⁺ and p15⁺/bcl2a⁺ host RPCs to the total number of GFP− p15⁺ or p15⁺/bcl2a⁺ host RPCs in the presence of WT donor RPCs. (E and F) Representative images (E) and quantification of clone size (F) of 72-hpf clones derived from single 12-hpf WT donor RPCs in p15⁺ and p15⁺/bcl2a⁺ retinae, respectively. OPL, the outer plexiform layer; IPL, the inner plexiform layer. Areas within white dashed contour lines are retinae in A and C. Data in B, D, and F represent mean ± SEM. Scale bars, 10 µm.