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Y. Zhang, Y. Liu, J. Xu, N. Nimri, C. F. Wildsoet; Microarray Analysis of RPE Gene Expression in Chicks During Long-term Imposed Myopic Defocus. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3680.
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This study examined the role of the retinal pigment epithelium (RPE) in transferring ocular growth signals from retina to sclera during the development of lens-induced myopia and possible secondary effects of myopia on RPE function.
To induce myopia, 4 White-Leghorn chicks wore monocular -15D lenses from 10-days of age for 38 days. Retinoscopy and high-frequency A-scan ultrasonography were used to monitor refractive errors (RE) and axial ocular dimensions of both treated and untreated fellow eyes, which served as controls. Chicks were then euthanized with euthasol, eyes enucleated, RPE isolated and RNA extracted. After verification of its quality in 2 ways, by spectrophotometry and using an Agilent 2100 bioanalyzer with an RNA 6000 Pico Chip Kit, RNA was subjected to cDNA synthesis, in vitro transcription and labeling. The labeled cRNA product was then cleaned up, quantified, fragmented, and hybridized onto Affymetrix GeneChip Chicken Genome Arrays. Microarray data were analyzed using BioConductor package. Expression patterns for RPE from myopic and fellow eyes were compared.
Significant myopia and axial length (AL) increases were recorded in treated eyes compared to their fellows after 38 days of treatment (RE: -13.00±0.46 cf. +4.06±0.33D; AL: 14.65±0.24 cf.12.67±0.19mm). Eight hundred and fifty-two transcripts were up- or down-regulated in myopic compared to fellow eyes, by at least 1.5-fold (p<0.05). Up-regulated growth factors and receptors included BMP2, BMP7, TGFB2, FGF1, PDGFA, FIGF, FGFR2, PDGFRA, and KDR. However, BMP receptors, TGF-β receptors and Smad proteins were not differentially expressed. Four neurotransmitter receptors (DRD4, GRM3, GRIN2A, GRIA3), a water channel (AQP4), a transporter (CRABP1), 2 peptidases (MMP2, PLAU), and a tight junction protein (CLDN2) also were up-regulated, while the neurotransmitter receptor, GABBR2, was down-regulated.
Differential expression was observed in a range of genes that could plausibly be involved in ocular growth regulation, based on their known actions in other tissues, although functional changes in RPE secondary to myopic growth may underlie changes in some affected genes, e.g. tight junctions. Gene expression changes involving the protein but not its receptor are compatible with a model of secretion from RPE to modulate the function or growth of adjacent tissues, while cases involving both the protein and related receptor are suggestive of complex roles, including constitutive activity.
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