Abstract
Purpose :
Extensive changes to the expression of coding genes have been documented in animal models of refractive error, however, the role of non-coding genes including microRNAs (miRNAs) remains largely unexplored. Thus, this study used next generation sequencing to profile miRNA expression in the chick retina/RPE/choroid following lens-induced myopia and hyperopia.
Methods :
Chicks were raised with +10D lenses, -10D lenses, or no lens. Following biometric measurements at 1, 2, and 3 days, four chicks per lens-group were euthanized and total RNA was extracted from the retina/RPE/choroid. Small RNA libraries were sequenced on the Ion Torrent system, and reads were mapped to the GalGal4 genome using TMAP. Empirical Bayes moderated t tests (LIMMA R package) were used to identify differentially expressed miRNA (fold change >2, FDR <0.05). The target genes of differentially expressed miRNAs were predicted using TargetScan (CWCS less than -0.4). Then, biological themes in the target genes were identified using KEGG pathway over-representation analysis in WebGestalt (FDR <0.05).
Results :
Refractive and axial length change was rapid during the first day of defocus for both lens-types and slower over subsequent days (particularly for positive lenses). Consistent with the initially rapid change in ocular morphology, more miRNA were differentially expressed at early versus late time-points and following negative versus positive lens-wear. Differentially expressed miRNA in negative and positive lens groups were distinct, with the exception of miR-214 that was up-regulated at 1 day in both lens groups. Multiple let-7 family members (let-7a-5p, let-7c-5p, let-7f-5p, let-7j-5p, let-7k-5p) were down-regulated following 1 and 2 days of negative lens-wear. Over-represented gene sets in the predicted targets of miRNA implicated following negative lens-wear included structural processes (focal adhesion, actin cytoskeleton) and several signalling pathways (AGE/RAGE, MAPK, mTOR). Focal adhesion and AGE-RAGE signalling were also implicated in the positive lens condition.
Conclusions :
The present findings suggest that miRNA are involved in regulating structural and inflammatory processes during myopia and hyperopia induction. Down-regulation of let-7, a master regulator of cell proliferation pathways, is particularly interesting in light of previous reports of increased proliferation at the retinal periphery in myopic chicks.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.