Abstract
Purpose: :
To compare the differential gene expression signatures produced in tree shrew retina by three different visual conditions that all produce ocular elongation and myopia.
Methods: :
Three groups of tree shrews (n=7 per group) were used: 4 days of monocular -5 D lens wear (ML), 4 days of monocular translucent diffuser wear (FD), and continuous darkness for 11 days (DK). Treatment ended at the same time point (28 days of visual experience). The untreated contralateral eyes in ML and FD groups served as controls. Real-time PCR was used to measure the relative changes in mRNA levels for 22 candidate genes: RARB, RXRB, RLBP1, SERPINF1, NYX, SLC1A6, EGR1, BMP2, RASGRF1, VIM, DRD2, P2RY1, NOS1, GCG, INSR, APOA1, APOE, IGF2, ACHE, FGFR2, IL1B, and VIP in comparison to a reference gene (POLR2A).
Results: :
The treated eyes in all groups responded with a myopic shift. Based on previous studies, the myopia in all groups was actively progressing. In the ML group, four genes showed significant differential (treated vs. control) changes: VIP (1.49 ± 0.09), APOE (1.16 ± 0.04), IGF2 (1.16 ± 0.06), and FGFR2 (1.26 ± 0.06) (mean fold change ± SEM, paired t-test, p<0.05). In the FD group, three genes showed significant differential changes: VIP (1.70 ± 0.08), ACHE (-1.12 ± 0.04), and IL1B (-1.23 ± 0.06). After 11 days of darkness there was a nearly 80% decrease in total retinal RNA yield, however, there was a significant up-regulation of VIP expression in treated eyes of DK group compared with control eyes of ML group (2.40 ± 0.20). Perhaps as expected, EGR1 mRNA level was down-regulated in the DK group (-3.75 ± 0.31).
Conclusions: :
VIP is the only gene that showed similar up-regulation in all three myopiagenic visual conditions. This suggests a possible common role of VIP in retinal signaling transduction during myopia development under minus lens, form deprivation, and darkness conditions. The other genes that showed significant differential changes may be involved in myopia development in specific visual conditions.
Keywords: myopia • retina • gene/expression