Vision-guided ocular growth in a mutant chicken model with diminished visual acuity

Exp Eye Res. 2012 Sep;102:59-69. doi: 10.1016/j.exer.2012.07.001. Epub 2012 Jul 21.

Abstract

Visual experience is known to guide ocular growth. We tested the hypothesis that vision-guided ocular growth is disrupted in a model system with diminished visual acuity. We examine whether ocular elongation is influenced by form-deprivation (FD) and lens-imposed defocus in the Retinopathy, Globe Enlarged (RGE) chicken. Young RGE chicks have poor visual acuity, without significant retinal pathology, resulting from a mutation in guanine nucleotide-binding protein β3 (GNB3), also known as transducin β3 or Gβ3. The mutation in GNB3 destabilizes the protein and causes a loss of Gβ3 from photoreceptors and ON-bipolar cells (Ritchey et al., 2010). FD increased ocular elongation in RGE eyes in a manner similar to that seen in wild-type (WT) eyes. By comparison, the excessive ocular elongation that results from hyperopic defocus was increased, whereas myopic defocus failed to significantly decrease ocular elongation in RGE eyes. Brief daily periods of unrestricted vision interrupting FD prevented ocular elongation in RGE chicks in a manner similar to that seen in WT chicks. Glucagonergic amacrine cells differentially expressed the immediate early gene Egr1 in response to growth-guiding stimuli in RGE retinas, but the defocus-dependent up-regulation of Egr1 was lesser in RGE retinas compared to that of WT retinas. We conclude that high visual acuity, and the retinal signaling mediated by Gβ3, is not required for emmetropization and the excessive ocular elongation caused by FD and hyperopic defocus. However, the loss of acuity and Gβ3 from RGE retinas causes enhanced responses to hyperopic defocus and diminished responses to myopic defocus.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amacrine Cells / metabolism
  • Animals
  • Axial Length, Eye
  • Chickens / genetics*
  • Disease Models, Animal*
  • Early Growth Response Protein 1 / genetics
  • Early Growth Response Protein 1 / metabolism
  • Eye / diagnostic imaging
  • Eye / growth & development*
  • Fluorescent Antibody Technique, Indirect
  • Glucagon / genetics
  • Glucagon / metabolism
  • Heterotrimeric GTP-Binding Proteins / genetics
  • Heterotrimeric GTP-Binding Proteins / metabolism
  • Microscopy, Confocal
  • Myopia / genetics
  • Myopia / metabolism
  • Myopia / physiopathology*
  • RNA, Messenger / metabolism
  • Refraction, Ocular / physiology
  • Retinoscopy
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sensory Deprivation
  • Ultrasonography
  • Vision Disorders / genetics
  • Vision Disorders / metabolism
  • Vision Disorders / physiopathology*
  • Vision, Ocular / physiology*
  • Visual Acuity / physiology*

Substances

  • Early Growth Response Protein 1
  • G-protein beta3 subunit
  • RNA, Messenger
  • Glucagon
  • Heterotrimeric GTP-Binding Proteins