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Congenital Stationary Night Blindness (RPE65 gene)

Congenital Stationary Night Blindness (RPE65 gene)

Congenital stationary night blindness (CNEC) is a retinal disorder caused by a mutation in the RPE65 gene, which causes night blindness and some impairment of daytime vision.

Symptoms

The characteristic symptom of CNEC is loss of night vision or reduced ability to see in the dark. They may also suffer vision problems during daylight hours. Although some dogs may experience permanent, irreversible blindness, the severity of symptomatology can vary significantly from case to case. Fortunately, dogs with minimal symptoms maintain a relatively good quality of life.

Disease Management

Currently, there is no known cure for this disease, but if your dog has vision problems, your veterinarian can provide guidance on how to help your pet adapt and cope with visual difficulties.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

The enzyme encoded by the RPE65 gene plays a key role in the process of visual pigment regeneration, which is necessary for rod- and cone-mediated vision. The expression of this enzyme occurs in the retinal pigment epithelium, which highlights its importance in visual function. In the study by Aguirre G.D. et al. (1998) a four nucleotide deletion (AAGA) in the RPE65 gene was identified, which causes a reading frame shift and the appearance of a premature stop codon. The result is mistranslation, and thus a defective protein.

Most affected breeds

Briard

Bibliography

Aguirre GD, Baldwin V, Pearce-Kelling S,et al. Congenital stationary night blindness in the dog: common mutation in the RPE65 gene indicates founder effect. Mol Vis. 1998 Oct 30;4:23.

Cai X, Conley SM, Naash MI. RPE65: role in the visual cycle, human retinal disease, and gene therapy. Ophthalmic Genet. 2009 Jun;30(2):57-62.