ATF4 and retinal degeneration: Our examination of H&E-stained T17M retinal cryostat sections and counts of the number of photoreceptor rows (Fig 1C and 1D) revealed a significant decline in the number of rows of photoreceptor nuclei in T17M ATF4-injected retinas (6.9 ± 0.20 rows of nuclei in GFP-injected vs. 4.4 ± 0.09 in ATF4-injected retinas), which further supported the functional test results indicating that ATF4 overexpression in T17M retinas accelerates retinal degeneration.