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Onkar Sawant, Meenal Shukla, Horton Amanda, Brent A Bell, Mary E Rayborn, Neal S Peachey, Joe G Hollyfield, Sujata Rao; Effect of light on photoreceptor development in mouse retina. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5417. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Environmental light is both the stimulus for visual function as well as an important regulator of photoreceptor physiology. Despite the importance of light in regulating visual function very little is known about the effects of light on the growth and development of the photoreceptors. Purpose of this study is to investigate the effect of light during early postnatal period on development of photoreceptors.
In this study, we reared new born mouse pups (C57BL/6) in either regular cyclic light dark condition (LD) or in constant darkness (DD) from post natal day 1 (P1) to post natal day 24 (P24). We performed immunofluorescence, western blot and transcriptional analysis to determine if photoreceptor development was affected. Since thyroid hormone signaling is known to regulate patterning of cone opsins, we also performed radio immune assay (RIA) to determine if serum thyroid hormones levels are altered in the DD pups compared to the LD pups. To determine if changes in photoreceptor development have any effect on the retinal function, we performed ERGs at P17 and P24. Electron microscopy was performed at P17 and P24 to explore the effect of light deprivation on morphology and plasticity of retinal connections.
In DD animals by P10 we observed significant changes in photoreceptor development. There was a significant reduction in rhodopsin levels in DD pups compared to LD pups as early as P10. By P17 the rod outer segment was shorter in DD pups compared to LD pups suggesting that light exposure is critical for outer segment development. In contrast to the rod photoreceptor there was a significant increase in proliferation of the cone photoreceptors. However a significant decrease in S-opsin expression was observed in DD pups. Levels of serum Triiodothyronine (T3) were significantly decreased in the DD pups compared to the LD pups at P10. ERG data revealed that both under light and dark adapted conditions there was a reduced response in DD pups compared to LD pups suggesting that retinal function was compromised when pups are deprived of light.
Our data demonstrates that during development light regulated thyroid hormone signaling is critical determinant for photoreceptor proliferation and development.
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