Progressive retinal atrophy (XL-PRA) - English Cocker Spaniel

Progressive retinal atrophies in dogs are a heterogeneous group of genetically determined eye diseases characterised by progressive degeneration of the retina, which can lead to a gradual deterioration of vision and ultimately blindness.

In the English Cocker Spaniel, prcd-PRA in particular has been known for many years. However, not all clinically diagnosed cases of PRA in this breed could be explained by the known variant associated with prcd-PRA. A newly described variant in the CACNA1F gene has now been associated with another form of PRA in the English Cocker Spaniel.

In the affected English Cocker Spaniels described to date, the first typical retinal changes were detected at approximately 3–4 years of age. As this is a comparatively late-onset disease, affected dogs may already have been used for breeding before clinical changes become apparent.

A genetic test can identify the genetic variant independently of the presence of clinical signs and can therefore support targeted breeding decisions. However, as genetic tests only detect the specific variant being tested, they do not replace regular eye examinations by a veterinarian or veterinary ophthalmologist.

The CACNA1F gene encodes the voltage-gated calcium channel Cav1.4, which plays an important role particularly in retinal nerve cells. At the terminals of photoreceptors, calcium influx enables the continuous release of neurotransmitters and is therefore essential for the transmission of visual signals. Changes in the CACNA1F gene can impair this function and lead to retinal disease.

The CACNA1F variant is inherited in an X-linked recessive manner. Due to this sex-linked mode of inheritance, the possible genotypes and the risk of developing the disease differ between males and females.