Progressive Retinal Atrophy Papillon y Phalène-Genetic disease dog

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

The onset of the disease is usually late, generally manifesting around 5 or 6 years of age, and its progression is slow. 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 onset of the disease is usually late, generally manifesting around 5 or 6 years of age, and its progression is slow. 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.

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 correlation has been established between the CNGB1 gene and the development of this eye condition. The CNGB1 gene is responsible for encoding a protein that is part of the cGMPc-activated cation channel in rod photoreceptors. This channel plays an essential role in the regulation of the visual transduction cascade, enabling the correct response of the eye to light. In the study by Ahonen et al. (2011), a complex mutation in the CNGB1 gene was found to be associated with the development of progressive retinal atrophy in Papillon and Phalène breeds. This specific mutation involves a one base pair deletion and a 6 base pair insertion in exon 26, resulting in the appearance of a premature termination codon in a highly evolutionarily conserved region. It is important to note that there are several forms of progressive retinal atrophy and different genes have been identified in dogs that could be related to this condition. At the moment, not all variations described to date are included in our test.

Most affected breeds

Papillon and Phalène

Bibliography

Ahonen SJ, Arumilli M, Lohi H. A CNGB1 frameshift mutation in Papillon and Phalène dogs with progressive retinal atrophy. PLoS One. 2013 Aug 28;8(8):e72122.

Progressive Retinal Atrophy (CNGB1 gene, Papillon and Phalène)