Abstract
Abstract: :
Purpose: Low retinal carotenoid levels are known to be associated with age–related macular degeneration (ARMD). Primate macula has high carotenoid levels, which is thought to protect the macula from light induced damage. Retbindin is a novel, retina–specific protein in the riboflavin– and folate–binding protein superfamily and is an interesting candidate for carotenoid binding in retina. Methods: Total RNA from monkey and human tissues, including retina were isolated. Northern blot analysis was performed on monkey multiple tissue, as well as monkey and human fovea, peripheral retina and RPE/choroid. In Situ hybridization (ISH) was performed on monkey retina to determine the mRNA distribution. A specific peptide antibody was designed to the human retbindin sequence. Western blot analysis was used on fovea and peripheral retina and immunohistochemistry (IHC) was performed on human retina to evaluate and localize retbindin protein expression. Results: Northern blot of multiple monkey tissues demonstrates that retbindin mRNA is predominantly expressed in retina. It is highly abundant in peripheral retina and less in the fovea. Western blot analysis confirmed the higher expression in peripheral retina. ISH showed retbindin mRNA expression in inner retina, including inner nuclear layer and retinal ganglion cell, and in the photoreceptor layer. IHC revealed that retbindin protein is localized in the photoreceptor layer, especially in cones. Conclusions: : Retbindin is essentially retina specific. It belongs to a superfamily with binding activity for different pigment–related small molecules, making it a possible candidate for involvement in carotenoid binding in the retina. While northern and western blots suggest that retbindin expression is highest in peripheral retina, IHC shows striking localization to cones.
Keywords: retina • gene/expression • age–related macular degeneration