We found several apoptotic cells in the Prom1−/− retina upon infection with control AAV-Gfp (Fig. 4I, I′, K), which was never detected in the Prom1+/−  retina (Fig. 4H, H′, K) under the same experimental conditions; however, infection with AAV-Igf1 significantly decreased the number of TUNEL-positive cells (Fig. 4J, J′, K). The gene discussed is IGF1; the disease is infection.