Figure 7. TUNEL assay on normal and affected dogs. A: Retina of the normal dog NA2 displayed no TUNEL-positive labeling. B: Retina of the affected dog A6 at the age of 2 months treated with DnaseI (positive control). C: Retina of the affected dog A6 at the age of 2 months treated with label solution only (negative control). TUNEL staining (D,E,F) and corresponding light micrographs (G,H,I) of the retinas of affected dogs. (D,G) retina of the affected dog A6 at the age of 2 months, (E,H) retina of the affected dog A1 at the age of 11 months and (F,I) retina of the affected dog A2 at the age of 28 months. TUNEL staining revealed apoptotic cells in all affected dogs, mostly in the outer nuclear layer, indicating apoptosis of photoreceptor cells. Abbreviations: retinal pigment epithelium (RPE); outer segments (OS); inner segments (IS); outer nuclear layer (ONL); outer plexiform layer (OPL); inner nuclear layer (INL); inner plexiform layer (IPL); ganglion cell layer (GCL). The scale bar represents 100 µm.