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Andreas Wenzel, Johannes von Lintig, Vitus Oberhauser, Naoyuki Tanimoto, Christian Grimm, Mathias W. Seeliger; RPE65 Is Essential for the Function of Cone Photoreceptors in NRL-Deficient Mice. Invest. Ophthalmol. Vis. Sci. 2007;48(2):534-542. doi: 10.1167/iovs.06-0652.
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purpose. Phototransduction in cones is initiated by the bleaching of their visual pigment, which comprises a protein component—cone opsin—and a vitamin A derivative—11-cis retinal. Little is known about the source of 11-cis retinal for cones. In the current study, neural retina leucine zipper–deficient (Nrl −/−) and rod opsin (Rho −/−)–deficient mice were used, two mouse models that have been described as having a “cone-only” retina, to analyze the retinoid metabolism of cones. In addition, these mice were bred to retinal pigment epithelial protein 65 (Rpe65 −/−)–deficient mice to study the role of RPE65.
methods. Mice were analyzed using morphology, Western blot analysis, immunohistochemistry, electroretinography (ERG), and retinoid profiling by HPLC.
results. In comparison to wild-type mice, the retina of Nrl −/− mice contained elevated levels of RPE65 and cellular retinaldehyde-binding protein (CRALBP), suggesting a particular role of these two proteins for the retinoid metabolism of cones. In Nrl −/− mice, different retinoid species were present in proportions similar to wild type. Ablation of RPE65 in Nrl −/− and Rho −/− mice led to the absence of 11-cis retinal, but increased the total retinoid content, with retinyl esters representing the most abundant retinoid species. In the absence of RPE65, retinal sensitivity in Nrl −/− mice dropped by a factor of a thousand.
conclusions. The data show that RPE65, previously shown to be essential for rod function, is also indispensable for the production of 11-cis retinal for cones and thus for cone function.
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