Abstract
Abstract: :
Purpose: Alterations in retinal gene expression are one of the first steps in the signaling pathway in visually guided eye growth. We are interested in identifying novel, yet unknown genes which change their expression pattern following treatment with plus or minus lenses, occluders or during recovery from myopia. Sequences found earlier by Differerential Display (DD) studies were applied to 5 `RACE and identified as 15 kDa selenoprotein and prolidase. Moreover, we obtained more sequence information for a yet unidentified gene. We have studied the expression of these genes following lens or occluder treatment. Methods: Nine to 13 day old white leghorn chickens (n=5-7) were monocularly treated with translucent occluders, +7 D or –7 D lenses for 2, 4, or 24 hours. Chickens of another group were allowed to recover from 4 days of occluder wear for 4 hours. Untreated chicks served as a control for contralateral eye effects. Following the extraction of retinal RNA, the relative expression of the three genes was determined by semiquantitative real-time PCR. Results: (1) After 4 hrs of recovery, following 4 days of occluder wear, gene expression of selenoprotein was significantly up-regulated by about 50% (treated vs. untreated contralateral eye, paired t-test: p<0.04). However, if treated eyes were compared to an independent control group, wearing of occluders or –7 D lenses for 4 hrs also resulted in a significant rise of gene expression (p<0.02; p<0.05). (2) Two hrs of occluder wear resulted in a significant down-regulation of prolidase compared to the control group (p<0.04) whereas 4 hrs induced an increase in gene expression when compared to both contralateral eye and control group (p<0.01; p<0.04). The rise between the second and the fourth hour of occluder wear was almost 2.5fold. Furthermore, 4 hrs of +7 D lenses increased gene expression of prolidase vs. the contralateral eye (p<0.004). (3) The not yet identified gene which was found to be controlled by the sign of imposed defocus in the DD studies proved to be down-regulated after 24 hrs of –7D lens wear compared to the control group (p<0.04; 123%). The trends found in the current study (4 hrs of treatment) are in the same direction as in the previous DD screening. Conclusions: Real-time PCR is a powerful method to demonstrate relative alterations in gene expression. Some of the genes that were examined could be involved in the signaling pathway of eye growth. Further investigations are necessary to reveal the time kinetics of changes in gene expression in response to retinal image defocus.
Keywords: myopia • gene/expression • retina