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Yan Zhang, Albert Truong, Feng Zhao, Christine Wildsoet; Chick Retinal Pigment Epithelium Responds to Imposed Defocus in Minutes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3590.
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© ARVO (1962-2015); The Authors (2016-present)
We previously reported that gene expression of BMP2, 4, and 7 in chick RPE show differential regulation by optical defocus in as little as 2 hours, which suggest their involvement of RPE in the early stage of eye growth regulation. This study was conducted to further characterize the temporal profile of these defocus-induced BMP gene expression changes in the chick RPE
White-Leghorn chicks wore monocular -10 or +10 D lenses from 14 days of age for 5, 15, 30 or 60 minutes. At the end of the lens treatment periods, chicks were sacrificed, eyes enucleated, RPE isolated and RNA extract. RNA was subjected to cDNA synthesis and then qPCR. Expression levels for lens-treated eyes were compared to those of their fellow eyes
As reported previously, differences in BMP gene expression were detected in chick RPE samples from eyes subjected to positive (+) versus negative (-) lens treatments. With positive lenses, 5 and 30 min of wear was sufficient to up-regulate the gene expression of BMP2 and BMP4 in treated eyes respectively, with up-regulation also detected at the other 3 time points for BMP2 and 60 minutes treatment for BMP4. For 5, 15, 30 and 60 min of +lens treatment, BMP2 was up-regulated 2.0-fold (p < 0.05, n = 5), 3.4-fold (p < 0.05, n = 7), 11.3-fold (p < 0.01, n = 7), and 5.0-fold (p < 0.001, n = 7), respectively, while BMP4 was up-regulated 7.8-fold (p < 0.05, n = 7) and 2.9-fold (p < 0.05, n = 7) after 30 and 60 minutes of treatment respectively. In contrast, BMP7 did not show differential expression with these short 5-60 min +lens treatments, and nor was differential expression detected with 5, 30, and 60 min of -lens treatment for these three BMPs. A trend of down-regulation of BMP2 was observed after 60 minutes of -lens treatment (6 out of 8 birds), but curiously, this gene showed significant up-regulation at 15 minutes (2.5-fold, p < 0.05, n = 8)
This study provides further evidence for the involvement of the RPE in eye growth regulation signaling cascades. The differences in the temporal profiles of gene expression changes induced by positive versus negative lenses, i.e., positive lenses inducing very rapid changes, suggest different pathways are involved. Finally, differences in the temporal profiles of the three genes studied - BMP2, 4 and 7, suggest that they are regulated differently. These proteins may interact synergistically across time during eye growth regulation
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