Purchase this article with an account.
Tao Zhang, Ning Zhang, Wolfgang Baehr, Yingbin Fu; Cone Opsin Determines The Time Course Of Cone Photoreceptor Degeneration In Leber Congenital Amaurosis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1813.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Mutations in RPE65 or lecithin-retinol acyltransferase (LRAT) disrupt 11-cis-retinal recycling and cause Leber congenital amaurosis (LCA), the most severe retinal dystrophy in early childhood. The objectives were to investigate why ventral and central cones degenerate much more rapidly than dorsal cones in murine LCA models (Rpe65-/- and Lrat-/-) and to explore why blue cone function is lost early in LCA patients.
We used the Lrat-/- mouse model to examine our hypothesis that mouse S-opsin and human blue opsin are more likely to cause cone degeneration than mouse M-opsin and human red/green opsins in LCA animal models and human patients, respectively. Subcellular localization of mouse M and S opsins was examined by immunohistochemistry. The mRNA and protein levels of cone opsins were analyzed by real-time RT-PCR and western blotting, respectively, at three stages of cone degeneration: 1) P14, pre-degeneration; 2) P18, early-stage degeneration; 3) P30, late-stage degeneration. We used a cell culture system to examine subcellular distribution various human cone opsins in the absence of 11-cis-retinal. Since rods and cones share similarities in the synthesis and transport of visual pigments, we replaced rhodopsin with S-opsin in Lrat-/- rods to see whether it would accelerate rod degeneration.
Although both M and S cone opsins mistrafficked as reported previously, mislocalized M-opsin was degraded whereas mislocalized S-opsin accumulated in Lrat-/- cones before the onset of massive ventral/central cone degeneration. Since S-opsin was expressed at a higher level in the ventral and central regions than in the dorsal region of the mouse retina, our results may explain why ventral and central cones degenerate much more rapidly than dorsal cones in murine Rpe65-/- and Lrat-/- LCA models. S-opsin in Lrat-/- cones was phosphorylated and ubiquitinated, suggesting that LCA shares etiology with conformational diseases in the brain. In addition, human blue opsin and mouse S-opsin, but not mouse M-opsin or human red/green opsins, aggregated to form cytoplasmic inclusions in transfected cells. Replacing rhodopsin with S-opsin in Lrat-/- rods resulted in mislocalization and aggregation of S-opsin in the inner segment and the synaptic region of rods and dramatically accelerated rod degeneration.
Our results demonstrate that cone opsins play a major role in determining the degeneration rate of photoreceptors in LCA.
This PDF is available to Subscribers Only