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Eric R. Ritchey, Christopher Zelinka, Simon M. Petersen-Jones, Andy J. Fischer; Vision-guided Ocular Growth In A Mutant Chicken Model With Diminished Visual Acuity. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3446.
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The proper regulation of ocular growth has been demonstrated to be a vision-dependent phenomenon across multiple species. We test whether vision-guided ocular growth is disrupted in an animal with a congenital defect causing diminished visual acuity.
We examine vision-guided ocular growth in the Retinopathy, Globe Enlarged (RGE) chicken, which develops an ocular phenotype, including poor visual acuity in young animals without significant retinal abnormalities, resulting from a single codon deletion within guanine nucleotide-binding protein beta-3 (GNB3) (Montiani-Ferreira et al. 2003; Tummala et al. 2006). We investigate whether interrupted form-deprivation and lens-imposed defocus influence rates of ocular growth and retinal amacrine cells in RGE eyes.
We found that minus lens-wear increased rates of ocular growth in RGE chicks in a manner similar to that seen in wild-type (WT) chicks. Brief daily periods of normal vision interrupting form-deprivation prevented ocular enlargement in RGE chicks in a manner similar to that seen in WT chicks. However, the growth-slowing effects of plus lens-wear were diminished in RGE eyes compared to those seen in WT eyes. We found that glucagonergic amacrine cells differentially expressed Egr1 in response to growth-regulating visual stimuli in RGE retinas similar to expression patterns seen in WT retinas, with the exception of diminished responses to short-term treatment with plus-defocus. In addition, we provide evidence that the GNB3-positive bipolar cells could form synaptic connections with the glucagonergic amacrine cells.
We conclude that the normal functions of photoreceptors and ON-bipolar cells in RGE retinas are not required for the growth-enhancing effects of minus lens-wear. The diminished responses of RGE eyes to plus-defocus may result from signaling deficits in photoreceptors and ON-bipolar cells.
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