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Progressive Retinal Atrophy (SLC4A3 gene, Golden Retriever)

Progressive Retinal Atrophy (SLC4A3 gene, Golden Retriever)

Progressive retinal atrophy is an eye condition in which a gradual loss of vision is experienced due to degeneration of the photoreceptor cells (cones and rods) in the retina.

Symptoms

One of the first clinical symptoms seen in progressive retinal atrophy is loss of night vision, as daytime vision degeneration usually takes longer to manifest and leads to complete blindness. In addition, this eye disorder has other distinctive signs, such as changes in the appearance of the eyes, which may include clouding, grayish hue and a slight abnormal sheen. Affected dogs tend to bump into objects more easily and may experience retinal cataracts as a result of disease progression.

Disease Management

The management of progressive retinal atrophy in dogs aims to improve the quality of life of the affected dog, even though there is no curative treatment for this disease. However, measures can be taken to ensure a suitable environment, such as keeping furniture and objects in place, which facilitates the dog's adaptation to the disease.

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

Progressive retinal atrophy is an inherited disorder belonging to a group of retinal diseases characterized by the gradual degeneration of the rods, leading to night blindness and loss of peripheral vision. Subsequently, degeneration of the cones occurs, resulting in loss of central vision and, ultimately, total blindness. A link between the SLC4A3 gene and the development of this ocular condition has been identified. The SLC4A3 gene encodes a solute transport protein found in several tissues, including Müller cells and horizontal retinal cells. In a study by Downs et al. (2011), a mutation in the SLC4A3 gene was identified in the Golden Retriever breed. This specific mutation is characterized by a single cytosine insertion in exon 16 (c.2601_2602insC). The suspected effect of this mutation is the generation of a premature termination codon in exon 18, which may result in degradation of the messenger RNA or production of a truncated protein. Importantly, this mutation does not explain all cases of progressive retinal atrophy in Golden Retrievers, but it is a common cause of this condition in the breed. This suggests that there may be additional loci that also contribute to the development of progressive retinal atrophy in the Golden Retriever breed.

Most affected breeds

Golden Retriever

Bibliography

Downs LM, Wallin-Håkansson B, Boursnell M,et al. A frameshift mutation in golden retriever dogs with progressive retinal atrophy endorses SLC4A3 as a candidate gene for human retinal degenerations. PLoS One. 2011;6(6):e21452.