Figure 3. AIF deficiency protects from RD-induced photoreceptor apoptosis.

To examine the AIF expression in retinas of AIF mutant mice (Hq/Y), we compared the expression of AIF and AIFsh mRNA (A and B) and AIF protein (C) in WT and Hq/Y mice before and after RD. Hq/Y mice exhibited negligible levels of AIF mRNA or AIF protein in contrast to WT mice (A–C). We also examined the expression of AIFsh, a proapoptotic short variant of AIF. The AIFsh mRNA expression was also decreased in AIF-deficient mice (Hq/Y; A and B), and AIFsh protein expression was not induced by RD in WT or Hq/Y mice (C). AIF immunohistochemistry confirmed the low AIF expression in Hq/Y mice (G and H; AIF in red, TUNEL in green, DAPI in blue) in contrast to WT mice (D and E). AIF deficiency in Hq/Y mice substantially decreased TUNEL-positive apoptotic cells after RD (E, H, and J) and preserved ONL cell count (K) and ONL thickness (L). The remaining TUNEL-positive apoptotic photoreceptors showed activated, cleaved caspase-9 in Hq/Y mice (F and I, caspase-9 in red). Electron microscopy also showed well-preserved rod spherules and cone pedicles in the outer plexiform layer (M and P, arrowheads; degenerated pedicles and spherules), decreased apoptotic nuclei in the ONL (N and Q, arrows), and relatively preserved mitochondria in the inner segment of photoreceptors (O and R, white arrows). n = 5 per group; *P < 0.05, **P < 0.01. Scale bars: 50 μm (D), 10 μm (M).