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H. Fong, M.–Y. Lin, S. Pandey, H. Kochounian; Exon–Skipping Isoform of Human RGR Opsin in Normal and AMD Retina . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5520.
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Mutations in the human RGR gene are associated with retinitis pigmentosa. Previously, we have found an extraneous exon–skipping splice variant of the human RGR mRNA in postmortem donor retinas. The predicted protein isoform differs from full–length human RGR opsin by having an in–frame deletion of exon 6, which contains the entire sixth transmembrane domain. The purpose of this work is to verify that the exon 6–deleted RGR protein (RGR–d) exists in human retinas.
Antibody probes were produced to detect the RGR–d protein by Western blot assay and immunohistochemistry.
In Western blot assays, RGR–d was detected in the retinas of a large proportion of individual donors, including patients with age–related macular degeneration (AMD). The relative abundance of RGR d varied significantly between individuals. The altered protein is expressed in RPE cells and, even in young donors, has a predominantly basal subcellular localization that is different from the distribution of normal RGR opsin. Positive immunostaining was seen in the drusen found in some of the older donors.
A common mutant form of RGR is expressed in the retina and RPE of humans, but not in bovine or mouse eyes. The RGR–d protein may be pathogenic under certain conditions or contribute to the progressive derangement of human RPE.
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