May 2007
Volume 48, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2007
Mice Heterozygous for a Glu155Gly Gene Targeted Mutation in GCAP1 Lack Flicker Response and Show Severely Reduced Photopic ERG Amplitudes
Author Affiliations & Notes
  • P. K. Buch
    Molecular Therapy and Molecular Genetics, Institute of Ophthalmology, University College London, London, United Kingdom
  • P. Cottrill
    Molecular Therapy and Molecular Genetics, Institute of Ophthalmology, University College London, London, United Kingdom
  • S. E. Wilkie
    Molecular Therapy and Molecular Genetics, Institute of Ophthalmology, University College London, London, United Kingdom
  • R. A. Pearson
    Molecular Therapy and Molecular Genetics, Institute of Ophthalmology, University College London, London, United Kingdom
  • S. S. Bhattacharya
    Molecular Therapy and Molecular Genetics, Institute of Ophthalmology, University College London, London, United Kingdom
  • D. J. Wells
    Gene Targeting Group, Department of Cellular and Molecular Neuroscience, Imperial College Faculty of Medicine, London, United Kingdom
  • D. M. Hunt
    Molecular Therapy and Molecular Genetics, Institute of Ophthalmology, University College London, London, United Kingdom
  • Footnotes
    Commercial Relationships P.K. Buch, None; P. Cottrill, None; S.E. Wilkie, None; R.A. Pearson, None; S.S. Bhattacharya, None; D.J. Wells, None; D.M. Hunt, None.
  • Footnotes
    Support Wellcome Trust Grant 063545
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 4666. doi:
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      P. K. Buch, P. Cottrill, S. E. Wilkie, R. A. Pearson, S. S. Bhattacharya, D. J. Wells, D. M. Hunt; Mice Heterozygous for a Glu155Gly Gene Targeted Mutation in GCAP1 Lack Flicker Response and Show Severely Reduced Photopic ERG Amplitudes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4666.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose:: Mutations in the gene encoding guanylate cyclase activating protein (GCAP1), also known as GUCA1A, cause the autosomal dominant cone dystrophy COD3. The Tyr99Cys and Glu155Gly mutations result in a GCAP1 protein that shows reduced Ca2+-dependent inactivation of retinal guanylate cyclase activity. Mice expressing a mutant Tyr99Cys Gcap1 transgene expressed only in rod photoreceptors have been shown to suffer photoreceptor degeneration in vivo. The studies presented here have been undertaken with mice harbouring a Glu155Gly knock-in mutation in Gcap1 and therefore represent a more accurate model of the human cone dystrophy.

Methods:: Mutant mice were generated using gene targeting, and were genotyped using PCR and sequencing. Retinal function was assayed using Ganzfeld ERGs.

Results:: The presence of an A→G substitution at position 19 of exon 6 in the Gcap1 gene, resulting in a Glu155→Gly amino acid change, was confirmed using PCR and direct sequencing. Electroretinography performed on mice heterozygous for this mutation showed that photopic b-wave amplitudes are significantly reduced (102.9 µV ± 26.1 µV) when compared to wild-type litter-mates (194.8 µV ± 34.1 µV) at six months of age (p < 0.001); mice harbouring the mutation also lack a flicker response to 10- and 15-Hz flash stimulus, whereas wild-type litter-mates have normal flicker responses. Scotopic b-wave amplitudes at this time point appear normal in knock-in mice.

Conclusions:: The analysis performed to date indicates that mice harbouring a Glu155Gly mutation in Gcap1 have a phenotype that is consistent with altered cone cell function. This will be further explored using a range of techniques including histology, single-cell suction electrode recording, and calcium imaging, so as to fully describe the cellular and physiological pathology of this human disease mutation.

Keywords: retinal degenerations: cell biology • photoreceptors • retina: distal (photoreceptors, horizontal cells, bipolar cells) 
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