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Michelle Grunin, Shira Levi, Tal Burstyn-Cohen, Itay Chowers; Gene Expression Signature in the Monocyte Population of Patients with Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2013;54(15):152.
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Further evidence in recent years has linked monocytes/macrophages and their respective populations with the pathogenesis of age-related macular degeneration (AMD). We speculate that monocyte involvement in AMD is reflected in the peripheral blood circulation. To evaluate this hypothesis, we have characterized the gene expression signature of monocytes from patients with AMD.
Peripheral blood was taken from treatment-naïve neovascular AMD patients (n=14), and age-matched controls (n=15). Peripheral blood mononuclear cells (PBMC) were separated using a Histopaque gradient, and total blood monocytes, including the CD14+ and CD14+CD16+ subgroups, were isolated via negative selection with magnetic beads. Total mRNA was extracted and gene expression was evaluated using the Affymetrix Gene 1.0 ST microarrays. Analysis was performed using the open sourceware programs R, DAVID, Expander, TANGO, ISMARA and other genomics tools. Age, ethnicity, response to treatment, and severity of disease were taken into account for analysis. Quantitative PCR (QPCR) was performed to validate microarray data.
Using RMA normalization and ANOVA, 1,522 genes were associated with AMD (P<0.05), of which 77 genes had a fold change>1.5. Alternative algorithm (Expander program with RMA) validated the existence of an altered expression pattern in AMD patients. QPCR analysis of 3 genes on AMD and control samples not previously used for microarray (AMD: n=6, control: n=6), supported the microarray results. DAVID functional analysis of the 1,522 differentially expressed genes generated 6 main annotation clusters that were upregulated (FDR-corrected P< 0.05) in AMD. Alternative algorithm (TANGO) detected 27 differentially expressed clusters (FDR-corrected P< 0.05). Both algorithms identified “immune system process” as the highest ranked cluster. Other clusters involved cytokine/chemokine activity, defense mechanisms, activation of cellular response, and apoptotic response. ISMARA motif analysis identified motifs of known transcription factor families involved in immune system regulation.
Microarray analysis revealed an altered gene expression signature in peripheral blood monocytes from neovascular AMD patients. The data supports the activation of the systemic immune response in monocytes from AMD patients.
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