Quick Summary
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Phenotype: Stargardt disease is an inherited degenerative eye disease that affects the retina, the region of the eye that senses light. Affected dogs will have a progressive decline in vision.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal, S = Stargardt disease variant
Breeds appropriate for testing: Labrador Retriever
Explanation of Results:
- Dogs with N/N genotype do not have the variant thought to cause Stargardt disease in Labrador Retrievers.
- Dogs with N/S genotypes have one copy of the Stargardt variant but will not develop Stargardt disease. If two carriers with are mated, approximately 25% of the puppies are predicted to develop disease and 50% are predicted to be carriers.
- Dogs with S/S genotypes are homozygous for the variant associated with Stargardt disease in Labrador Retrievers and are expected to develop disease.
Results of this test can be submitted to the OFA (Orthopedic Foundation for Animals)
Labrador Retriever Health Panel 1
$165 per animal
Labrador Retriever Health Panel 2
$180 per animal
Sample Collection
Dog DNA tests are carried out using cells brushed from your dog's cheeks and gums. The preferred cytology brushes are sent to you by mail, or you may provide your own brushes. For accepted alternative brushes, click here
We recommend waiting until puppies are at least three weeks old before testing.
Step-By-Step:
- Make sure the dog has not had anything to eat or drink for at least 1 hour prior to collecting sample.
- When swabbing puppies, isolate each puppy from the mother, littermates and any shared toys for 1 hour prior to swabbing. Puppies should not have nursed or eaten for 1 hour prior to collecting sample.
- If collecting samples from more than one dog, make sure to sample one dog at a time and wash your hands before swabbing another dog.
- Label brush sleeve with name or ID of dog to be sampled.
- Open brush sleeve by arrow and remove one brush by its handle.
- Place bristle head between the dog’s gums and cheek and press lightly on the outside of the cheek while rubbing or rotating the brush back and forth for 15 seconds.
- Wave the brush in the air for 20 seconds to air dry.
- Insert brush back into sleeve.
- Repeat steps 5 - 8 for each unused brush in sleeve on a fresh area of cheek and gums. Make sure to use and return all brushes sent by the VGL. In most cases, it will be 3 brushes per dog. If using interdental gum brushes, please note that the VGL requires 4 brushes per dog and only moderate or wide interdental gum brushes are accepted.
- Do not seal brushes in sleeve.
- Place all samples in an envelope and return to the address provided.
ATTENTION:
- Do not collect saliva/drool – the key to obtaining a good sample is getting cheek cells on the swab
- Do not rub swab on the dog’s tongue or teeth – this will result in poor quality sample
- Do not collect a sample from a puppy that has recently nursed – the mother’s genetic material can rub off on the puppy’s mouth and contaminate the sample
Stargardt disease is an inherited degenerative eye disorder impacting the photoreceptor cells (cells of the eye that detect light) of the eyes, known as cones and rods. The cones are the cells that detect bright light and are important for color vision. Rods are the photoreceptor cells that detect light at night or in other low light conditions. Affected individuals show impaired vision in both daylight and dim light conditions, but partial vision is retained throughout their lifetime. Clinical features of Stargardt disease include diffuse retinal degeneration and reduction of the number of photoreceptors, with profoundly abnormal cone cell function but rod cell function is impacted to a lesser extent.
A single nucleotide insertion in the ATP binding cassette subfamily A member 4 (ABCA4) gene of a cytosine (C) in exon 28 is associated with Stargardt disease in the Labrador retriever. This insertion (c.4176insC) affects the reading frame of the protein and leads to a premature stop codon at amino acid position 1395 (p.F1393Lfs*1395). The resulting protein is truncated, missing the last 874 amino acid residues compared to the normal ABCA4 protein. This shortened protein is thought to lead to toxic byproducts in the cell that result in photoreceptor degeneration. The mode of inheritance is autosomal recessive, which means that males and females are equally affected and that two copies of the variant are needed to cause Stargardt disease. Mutations in this same gene cause several clinically distinct ocular diseases including one with a similar presentation to this Labrador specific disease.
The Stargardt disease variant was first identified in a pair of Labrador retriever siblings (one male, one female). Additional testing confirmed the association of the variant with disease. Eye exams of 22 additional Labrador Retrievers identified eight clinically affected dogs. All were were homozygous for the c.4176insC variant, whereas fourteen showed no signs of retinal degeneration by seven years of age; seven of these were carriers and the remaining seven were homozygous for the normal allele.
The VGL offers a DNA test for Stargardt disease. Test results assist veterinarians with diagnosis of Stargardt disease and helps breeders identify carriers among breeding stock to select appropriate mates thus reducing the risk of producing affected offspring.
