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B. S. Westlund, M. Hansen, J. Olsen, M. H. Nissen, J. R. Sparrow; Microarray Gene Expression Profile of A2E-Laden RPE Cells Irradiated With Blue Light. Invest. Ophthalmol. Vis. Sci. 2009;50(13):711.
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Accumulation of lipofuscin and its major fluorophore A2E in the retinal pigment epithelium (RPE) is involved in the etiology of some retinal disorders such as Stargardts and age-related macular degeneration (AMD). We have previously shown that exposure of A2E-laden RPE cells to blue light (430nm) induce RPE cell death and activation of the complement system. Here we performed a genome-wide gene expression profiling to identify genes that are differentially expressed in A2E-laden RPE cells that had been irradiated at 430nm (A2E/430nm).
ARPE-19 cells were allowed to accumulate A2E and were irradiated at 430nm for 6, 10, 15 or 20 min. Controls included untreated RPE cells, A2E-free RPE cells irradiated for 20 min and RPE cells that had accumulated A2E but were not exposed to blue light. Differential gene-expression was quantified using microarrays (HG-U133 plus 2.0, Affymetrix) for mRNA expression. Robust multiarray analysis (RMA) procedure with quantile normalization and RMA background correction was used to summarize probe level into single normalized gene expression measures for each probe set. The obtained high-dimensional dataset (54,675 probe sets corresponding to 54,675 dimensions) was reduced to 2 dimensions using principal component analysis (PCA). PCA is a multivariate dimension reduction technique for finding new variables to represent covarying original variables. Quantitative RT-PCR was used to validate several candidate genes.
1st principal component from PCA showed separation of the groups with a clear dose-response pattern according to the duration of irradiation. Further analysis of the involved genes revealed an up-regulation of genes coding for anti-apoptotic proteins and heat shock proteins in A2E-laden RPE cells exposed to blue light as compared to controls. A2E/430nm also induced down-regulation of of complement related genes.
We have identified genes that are differentially regulated in the setting of intracellular accumulation of A2E and exposure to blue light. These genes may serve as valuable targets for further investigations in order to improve the understanding of the mechanisms contributing to development of AMD.
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