Ablation of Pigment Epithelium-derived Factor (PEDF) and Pigment Epithelium-derived Factor Receptor (PEDF-R) is Detrimental for Photoreceptors

Authors

• D Williams
• A McFadden
• T Sanchez
• AJ Hepperla
• M Henderson
• G Stott
• I Davis
• S Pattenden

Abstract

The SERPINF1 gene encodes the retinoprotective pigment epithelium-derived factor (PEDF). Photoreceptor cells express the PNPLA2 gene for its receptor PEDF-R, which is responsible for PEDF-mediated neurotrophic activities. To determine whether the PEDF/PEDF-R axis plays a regulatory role in photoreceptor structure and function, we characterized photoreceptors deficient in PEDF and PEDF-R.
CRISPR Pnpla2 knock-out mouse was crossbred with Serpinf1 null, and three genotypes were generated: wild type, Serpinf1+/-/Pnpla2-/- and Serpinf1-/-/Pnpla2-/-. Gene expression was determined in dissected retinas by RT-PCR. Mice were evaluated for electroretinography (ERG), fundoscopy and autofluorescence angiography. Whole eyes were enucleated and processed for histology, immunofluorescence, TUNEL, confocal microscopy, and transmission electron microscopy.
At 3 months of age, Serpinf1+/-/Pnpla2-/- and Serpinf1-/-/Pnpla2-/- mice had decreased and undetectable retinal Serpinf1, respectively, relative to their Serpinf1+/+/Pnpla2+/+ littermate controls and both had undetectable Pnpla2 expression levels. The Serpinf1+/-/Pnpla2-/- mice had higher lipid droplet density in their retinal pigment epithelium and Bruch’s membrane and the vasculature was more ectatic relative to controls. The Serpinf1-/-/Pnpla2-/- photoreceptors had morphological abnormalities. The ERG a- and b-waves of Serpinf1+/-/Pnpla2-/- and Serpinf1-/-/Pnpla2-/- mice were attenuated relative to controls. Loss of both PEDF and PEDF-R caused retinas to have thinner outer nuclear layers with TUNNEL positive photoreceptor cells, as well as decreased levels of rhodopsin, opsin, PKCα, and synaptophysin compared to controls.
Ablation of both PEDF and PEDF-R in mice causes defects in photoreceptor development resulting in suboptimal photoreceptor performance and increases in lipid accumulation. These data identify the PEDF/PEDF-R axis as a critical component for photoreceptor structure and function.

Scientific Focus Area: Molecular Biology and Biochemistry

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