Abstract
Purpose: :
To investigate the effect of imposed myopic defocus on gene expression profiles in chicken retinal pigment epithelium (RPE) using DNA microarrays.
Methods: :
Fifteen 19 day-old White Leghorn chicks wore monocular +10 D lenses for 48 hours; fellow eyes were left untreated. RPE cells were isolated from both treated and fellow eyes and total RNA extracted. Three chips were used as statistical repeats between treatment and control, with samples from both treated and fellow eyes applied to each, generated by pooling extracted RNA from 5 birds in each case. Data were analyzed using Partek software.
Results: :
Out of a possible maximum of 38535 gene probes detectible with the Affymetrix Chicken Genome chip, an average of 20314 were detected in RPE from treated eyes (52.1%) compared to 19809 genes for fellow eyes (51.4%). Differential expression by more than 1.5-, 2- and 3-fold was observed for 1327, 344 and 59 probes respectively (p<0.05). Most genes were down-regulated in treated eyes and included glucagon receptor, Map kinase 1 (MAPK1), bone morphogenetic protein 4 (BMP4), TGF-β induced factor (all ≥3-fold), connective tissue growth factor (CTGF), bone morphogenetic protein 2 (BMP2), claudin-11, TIMP2, TIMP3 and CREB1 (all ≥1.5 fold). Many of the genes previously reported to be differentially expressed (≥1.5 fold) in response to hyperopic defocus (-10 D lens) (abstract # 4417, ARVO 2007), including TGF-β2, insulin-like growth factor-1 receptor (IGF-1R), somatostatin, vasoactive intestinal peptide (VIP), aquaporin, iNOS, L-type voltage-dependent calcium channel and protein kinase C, were unaffected by myopic defocus.
Conclusions: :
That imposed myopic defocus induced significant differential expression of a number of genes in the RPE, including ones already linked with ocular growth, is consistent with a role for the RPE in ocular growth modulation. That the gene sets affected by myopic defocus have apparently little overlap with that affected by hyperopic defocus argues for different signal pathways, at least at the level of the RPE.
Keywords: retinal pigment epithelium • gene microarray • gene/expression