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Title: Egr-1 mRNA expression is a marker for the direction of Mammalian Ocular growth
Authors: Ashby, RS
Zeng, G
Leotta, AJ
Tse, YY 
McFadden, SA
Keywords: Myopia
Guinea pig
Refractive error
Issue Date: 2014
Publisher: Association for Research in Vision and Ophthalmology
Source: Investigative ophthalmology and visual science, 2014, v. 55, no. 9, p. 5911-5921 How to cite?
Journal: Investigative ophthalmology and visual science 
Abstract: PURPOSE. The immediate early gene Egr-1 is thought to form part of the pathway that mediates abnormal ocular growth. This study investigated whether the mRNA expression levels of Egr-1 in a mammalian retina are modulated differentially, depending on the direction of ocular growth. METHODS. To induce accelerated growth and myopia, guinea pigs wore a -5 diopter ( D) lens over one eye from 4 to 11 days of age. To induce inhibited growth, the lens was removed after 7 days of -5 D lens wear, and the eye allowed to recover from myopia for 3 days. Ocular parameters and Egr-1 mRNA levels were subsequently assessed, and compared to untreated fellow eyes and eyes from untreated littermates. Possible circadian changes in Egr-1 mRNA levels were also determined in 18 additional animals by taking measures every 4 hours during a 24-hour cycle. RESULTS. Ocular compensation to a -5 D lens occurred after 7 days (Delta -4.8 D, Delta +147 mu m growth, N = 20). In 5 highly myopic eyes (Delta -7.4 D), Egr-1 mRNA levels in the retina were significantly downregulated relative to contralateral control (51%) and age-matched untreated (47%) eyes. Three days after the -5 D lens was removed, eyes had recovered from the myopia (Delta - 0.5 D, relative change of +2.9 D, N = 4) and Egr-1 mRNA levels were significantly elevated relative to contralateral (212%) and untreated (234%) eyes, respectively. Normal Egr-1 mRNA expression was higher in the middle of the day than in the middle of the night. Immunolabeling showed strong Egr-1 reactivity in cell bodies in the inner nuclear and ganglion cell layers. CONCLUSIONS. Egr-1 mRNA levels in a mammalian retina show a bi-directional persistent response to opposing ocular growth stimuli. This suggests retinal Egr-1 might act as a signal for the direction of ocular growth in different species.
ISSN: 0146-0404
EISSN: 1552-5783
DOI: 10.1167/iovs.13-11708
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