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Youwen Zhang, Samuel D Cross, Yong Lee, James Brett Stanton, Lori A Bachman, Yun-Zheng Le, Alan D Marmorstein, Lihua Y Marmorstein; RPE-specific deletion of murine Atg5 or Atg7 causes AMD-like features and retinal degeneration. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2397.
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In early age-related macular degeneration (AMD), damaged proteins, lipids, and functionally disabled organelles accumulate within retinal pigment epithelium (RPE) cells and/or in sub-RPE deposits. Autophagy is a cellular degradation pathway responsible for the disposal of damaged macromolecular complexes and organelles. ATG5 and ATG7 are two core components of the autophagy machinery. Deletion of either gene causes neonatal lethality in mice. This study examined whether autophagy deficiency in the RPE causes AMD-like or other retinal defects through conditional knock out of Atg5 or Atg7 in mouse models.<br />
Conditional knockout mice with a floxed allele of Atg5 or Atg7 were crossed with inducible VMD2-rtTA/Cre transgenic mice resulting in doxycycline inducible RPE-specific gene expression. Eyes were collected from induced and non-induced mice and 1µm plastic sections were stained with Toluidine blue, and inspected for gross histopathological changes by light microscopy. Transmission electronic microscopy (TEM) of thin sections was performed for ultrastructural analysis. Accumulation of damaged lipids, proteins, and/or DNA/RNA was determined by immunofluorescence staining of cryosections.<br />
Retinal degeneration was observed in both Atg5 and Atg7 conditional knockout mouse lines. By 8 months of age, photoreceptor and outer plexiform layers were absent and inner nuclear layer was thinned. RPE cells were thinned, the nuclei were flat, and RPE cell density was reduced. Neovascularization and RPE cell migration were also observed in both mouse lines. Immunofluorescence staining indicates that lipid peroxidation was no more pronounced in these lines than in controls. 4-hydroxynonenal (HNE) and malondialdehyde (MDA) levels were similar. However, the levels of both 3-nitrotyrosine and advanced glycation end products (AGEs) were elevated indicating significant more oxidative protein damage. A higher level of 8-hydroxyguanosine (8-OHdG) was also observed, indicating elevated oxidized DNA/RNA damage.<br />
RPE-specific autophagy deficiency causes retinal degeneration and AMD-like features in mice.<br />
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