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Brenda Tan, Abduqodir Toychiev, David Troilo, Stewart A Bloomfield; Rearing mice in low ambient light as a model to explore the genetics of myopia. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2737.
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© ARVO (1962-2015); The Authors (2016-present)
A mouse model of myopia provides an unparalleled opportunity to explore the genetic basis of eye growth and the development of myopia. Here we present preliminary evidence that rearing in low luminance can be used to induce eye growth and refractive changes in mice.
Different strains of mice, including control C57BL/6 mice and Cx36 knockout (KO) and their wild type littermates (CxWT: mixed 129S1/C37BL/6 background) were tested. Mice were raised in one of two 12:12 hour luminance conditions: a control condition of 500 lux or dim ambient light of 20 lux for 12 weeks. All mice were raised under control conditions for the first 3-5 weeks after birth. Animals were refracted with an IR videorefraction system (F. Schaeffel, Germany). Axial length was measured with a small animal OCT (Bioptigen Invivovue). Measurements were taken at 4-week intervals. Mice were anesthetized with 2:1 ketamine:xylazine during the measures.
All mice strains raised under normal 500 lux illumination showed a significant reduction in hyperopia with a shift toward myopia over the 12 week period. C57BL/6 mice showed a refractive change of -11.5 D and an increased axial length of 0.21 mm. CxWT mice showed a comparable refractive change of -12.8 D and an increased axial length of 0.20 mm. However, control mice raised in dim 20 lux illumination showed significantly greater shifts towards myopia and increases in axial length as compared to measures under 500 lux. C57BL/6 mice raised in 20 lux showed a refractive change of -19.2 D with an increased axial length of 0.23 mm. CxWT mice showed a refractive change of -15.1 D coupled with an increased axial length of 0.23 mm. In preliminary studies we examined refractive changes in Cx36 KO mice as the gene encoding Cx36 has been implicated in human myopia (Cheng et al., 2013). Interestingly, Cx36 KO mice showed only a -1.5 D changes under 500 lux luminance and only a -5.1 D change under 20 lux, significantly different from changes seen in control mice.
Low luminance can be used as an effective method for inducing changes in eye growth and refraction in mice and may serve as a useful model of myopia to test the genetics of visually regulated eye growth and refractive state. Preliminary tests indicate that Cx36, expressed by neuronal gap junctions in retina, may be important in the growth response to different light conditions.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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