Atrophy, more commonly known as PRA, is a general term for a group
of diseases causing degeneration of the retina, leading to a loss
of vision. One form of this disorder is known as cord1-PRA, which
stands for cone-rod dystrophy-PRA. Cord1-PRA is a genetic disorder
associated with a recessive mutation in the RPGRIP1 gene, which
codes for an important photoreceptor protein in the eye. Like many
forms of PRA, cord1-PRA is breed
specific, and is known to occur in Miniature Dachshunds and English
Cone-rod dystrophy first affects the cones in
the retina, which are the photoreceptors responsible for detecting
bright light or daylight. Rods, or low-light photoreceptors, begin
degenerating secondarily. This is different than other forms of
PRA, such as prcd-PRA, in which the rods are affected first, followed
by the cones. Unfortunately, most dogs affected by cord1-PRA will
eventually become blind, and there is no cure at this time.
The age of onset can vary with this disorder,
some dogs will first begin experiencing problems around 6 months
in age, though the average age of onset is around 5 years of age.
A small percentage of dogs do not experience any symptoms until
as late as 10 years of age. It is not yet known why some dogs will
experience late-onset PRA, however, it is likely due to the presence
of other genetic modifiers that have not been determined at this
Because this disorder is recessive, a dog must
have two copies of the mutated gene to exhibit symptoms associated
with PRA. A dog can be a carrier of cord1-PRA, meaning it only has
one copy of the mutation, and not show any outward signs of retinal
degeneration. A carrier can still pass on the mutated gene to any
offspring; mating two carrier dogs can produce offspring affected
Animal Genetics offers DNA testing and detection
of the gene mutation associated with cord1-PRA. Animal Genetics
only tests for this mutation in the breeds known to be affected
by cord1-PRA, including:
Miniature Long-Haired Dachshund
Miniature Wire-Haired Dachshund
Minature Smooth-Haired Dachshund
English Springer Spaniel
US per sample.
Collect sample using buccal swabs provided by
Animal Genetics. Ensure that the dog has not eaten within a few
hours of sample collection. Any food particles can inhibit the test.
Rub each of the swabs along the inside of the dog's mouth for 10-15
seconds, and allow the swabs to dry thoroughly. Label the provided
envelope with the dog's name, and place the swab inside it. Download
and complete a submission form for each sample and send along with
payment to Animal Genetics for testing.
Results are given using the following symbolic
The dog carries two copies of the mutant gene and is homozygous
for the cord1-PRA mutation. The dog will display symptoms associated
with the disorder, and will always pass on a copy of the mutation
to any offspring.
Both the normal and mutant copies of the gene detected. The
dog is a carrier for cord1-PRA, and could pass on either allele
to any offspring.
Tested negative for the cord1-PRA mutation.