ISSN 2398-2969      

Retina: cone degeneration

icanis

Synonym(s): Hemeralopia; day blindness


Introduction

  • Cause: rare inherited autosomal-recessive disease.
  • Signs: day blindness, with an absence of cone function in adult dogs.
  • Diagnosis: clinical signs in specific breeds, electroretinography and DNA testing.
  • Treatment: no treatment is possible commercially although gene therapy has been successful.
  • Prognosis: night vision is not affected throughout life but there is always day blindness.

Pathogenesis

Etiology

  • Cone degeneration is a recessively inherited disease.
  • The mutation responsible for the condition has been identified as a deletion of part of the CNGB3 gene in the Alaskan Malamute and Miniature Australian Shepherd.
  • The condition in the German Short-Haired Pointer is allelic with the Alaskan Malamute gene deletion but instead of a deletion it is due to a point mutation in the CNGB3 gene.

Pathophysiology

  • The cones develop normally and this has been shown histologically.
  • Degeneration of the cones progressive occurs from 8-12 weeks of age until all cones are affected by six months of age.
  • No cone elements remain from 4 years of age.
  • There is a selective absence of b-3-transducin expression early in the course of the disease.

Timecourse

  • Cones are normal at birth.
  • Degeneration begins at approximately 8-12 weeks of age, and clinical signs develop at this stage.
  • Cone loss is progressive until no cone elements remain by 4 years of age.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Yeh C Y, Goldstein O, Kukekova AV et al (2013) Genomic deletion of CNGB3 is identical by descent in multiple canine breeds and causes achromatopsia. BMC Genetics 14,  27 PubMed.
  • Komáromy A M, Rowlan J S, Corr A T P et al (2013) Transient photoreceptor deconstruction by CNTF enhances rAAV-mediated cone functional rescue in late stage CNGB3-achromatopsia. Molecular Therapy 21 (6), 1131-1141 PubMed.
  • Garcia M M, Ying G S, Cocores C A et al (2010) Evaluation of a behavioral method for objective vision testing and identification of achromatopsia in dogs. Am J Vet Res 71 (1), 97-102 PubMed.
  • Komáromy A M, Alexander J J, Rowlan J S et al (2010) Gene therapy rescues cone function in congenital achromatopsia. Human Molecular Genetics 19 (13), 2581-2593 PubMed.
  • Mowat F M, Petersen-Jones S M, Williamson H et al (2008) Topographical characterization of cone photoreceptors and the area centralis of the canine retina. Mol Vis 14, 2518-2527 PubMed.
  • Sidjanin D J, Lowe J K, McElwee J L et al (2002) Canine CNGB3 mutations establish cone degeneration as orthologous to the human achromatopsia locus ACHM3. Hum Mol Genet 11 (16), 1823-1833 PubMed.
  • Aguirre G D, Rubbin L F (1975) The electroretinogram in dogs with inherited cone degeneration. Invest Ophthalmol 14 (11), 840-847 PubMed.
  • Aguirre G D, Rubin  L F (1974) Pathology of hemeralopia in the Alaskan malamute dog. Invest Ophthalmol 13 (3), 231-235 PubMed.
  • Rubin L F (1971) Hemeralopia in Alaskan malamute pups. JAVMA 158 (10), 1699-1701 PubMed.
  • Rubin L F (1971) Clinical features of hemeralopia in the adult Alaskan malamute. JAVMA 158 (10), 1696-1698 PubMed.

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