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M. R. Frost, T. T. Norton; Patterns of Differential Protein Expression in Tree Shrew Sclera During the Development of, and Recovery From, Lens-Induced Myopia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3683.
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© ARVO (1962-2015); The Authors (2016-present)
During experimentally induced emmetropization there is a regulated remodeling of the scleral extracellular matrix. Difference Gel Electrophoresis (DIGE) was used to identify proteins that are involved in this process.
Two groups of 5 tree shrews wore a monocular -5 D lens, starting 24 days after natural eye opening. The compensation group wore a lens for 4 days while the recovery group wore a lens for 11 days, compensated, and then were allowed to recover for 4 days. Two normal groups (n=5) were also used, age-matched to each of the treatment groups. Scleral proteins were isolated and resolved by DIGE. The resulting protein profiles were compared using SameSpots analysis software to identify protein spots that were differentially represented between treated, control, and normal eyes during both lens compensation and recovery. Proteins were identified from these spots by mass spectrometry.
77 spots were found to be differentially represented across all comparisons, 70 of which were successfully examined by mass spectrometry, identifying 63 distinct proteins. Of these, 54 proteins were differentially expressed between treated, control, and normal eyes during lens compensation (46 down-regulated, 8 up-regulated); 29 proteins were changed during recovery (15 down-regulated, 14 up-regulated). Focusing on treated vs. control eye sclera, during lens wear there was a general down-regulation of proteins involved in cell adhesion and mobility, both cell-cell and cell-ECM interaction. Also reduced was the level of several ECM components and proteins involved in cytoskeletal organization and biogenesis, primarily actin remodeling and proteins that interact with actin. Also down-regulated were small GTPase-mediated signal transduction proteins and factors that regulate transcription. No proteins were found to be up-regulated between treated vs. control sclera during lens compensation. After 4 days of recovery, there was a continued down-regulation of many of the cytoskeletal, ECM, and signal transduction proteins identified during lens compensation, while several stress response proteins were up-regulated (in contrast to the slight down-regulation observed during compensation).
The proteomic results are consonant with mRNA studies, suggesting that a major effect of retinal "go" signals in the sclera is to down-regulate cell-matrix interactions. This, along with loss of collagen at the edges of the lamellae, may produce the increased viscoelasticity that results in faster axial elongation. Recovery is not a mirror image of compensation.
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