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Yan Zhang, Yue Liu, Carol Ho, David Hammond, Christine F. Wildsoet; Differential Expression of BMP7, TGF-β2, and Noggin in Chick RPE after Imposed Optical Defocus. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3458.
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This study examined the gene expression of BMPs (BMP3, 6, 7), TGF-β2, and Noggin (NOG), a BMP antagonist protein, in chick retinal pigment epithelium (RPE) after exposure to imposed optical defocus. It is part of a larger investigation into the role in early eye growth regulation of TGF-β family (including BMPs) in RPE, which we believe to be involved because of its strategic location between the retina and choroid.
White-Leghorn chicks wore monocular -10 or +10 D lenses from 19 days of age for 2 or 48 h. Age-matched non-treated chicks were included. At the end of the lens treatment periods, chicks were sacrificed, eyes enucleated, RPE isolated and RNA extracted. RNA from the RPE and retina of age-matched non-treated chick was also purified. RNA was subjected to cDNA synthesis and then real-time PCR amplification. Primers for chick BMP3, BMP6, BMP7, NOG, TGFB2, and GAPDH (house-keeping gene) were designed using Primer Express 3.0 and gene information in the NCBI database. Expression levels for lens-treated eyes were compared to those of their fellow eyes, and these data were compared with values from untreated chicks.
All five genes (BMP3, 6, 7, TGFB2, NOG) were highly expressed in chick RPE compare to retina (459, 15, 599, 6 & 28 fold higher respectively). Expression of BMP7 in RPE was down-regulated by 2.2 and 2.0 fold after 2 and 48 h of -10 D lens wear compared to levels in fellow eyes (p < 0.01, n = 16; p < 0.05, n = 13), but not affected by +10 D lens wear. Likewise, expression of NOG in RPE appeared to be up-regulated after 2 and 48 h of the -10 D lens treatment, i.e. by 2.0 and 5.9 fold (p = 0.06, n = 6; p < 0.05, n = 14), although compared to levels for control chicks, the latter trends reflected down-regulation in fellow eyes rather than up-regulation in treated eyes. In contrast, expression of TGF-β2 in RPE was not affected by -10 D lens wear, but was up-regulated by 3.9 and 8.6 fold after 2 and 48 hours +10 D lens wear respectively (p < 0.01, n = 14, 14). Neither the expression of BMP3 nor that of BMP6 was affected by -10 D and +10D lens treatments.
Our finding that expression levels of BMP7, TGF-β2, and NOG in chick RPE are all sensitive to imposed optical defocus, albeit with defocus sign-dependent differences in sensitivity, is consistent with roles of these members of the TGF-β superfamily as RPE-based signal relays or modulators in the early eye growth regulation.
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