Juvenile onset
For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.
At risk dogs are highly likely to show signs of this disease in their lifetime.
Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.
Clinical signs of CD occur at the age of 8-12 weeks. Affected pups show signs of day-blindness and photophobia due to the degeneration of cone cells in the retina. Cone cells are gradually lost and may be completely absent in an adult dog affected with CD. The degeneration does not affect rod cells, therefore vision in dim light remains normal; cone degeneration does not result in complete blindness.
Affected dogs may find exposure to bright light irritating or even painful, so exposure should be limited where possible. However, their vision at night and in dim lighting should remain intact.
There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.
This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to be shown. A carrier dog with one copy of the CD mutation can be safely bred with a clear dog with no copies of the CD mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the CD mutation. A dog with two copies of the CD mutation can be safely bred with a clear dog. The resulting puppies will all be carriers. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the CD mutation could develop due to a different genetic or clinical cause.
| Gene | CNGB3 |
|---|---|
| Variant | Deletion |
| Chromosome | 29 |
| Coordinate Start | 32,695,888 |
| Coordinate End | 33,101,135 |
All coordinates reference CanFam3.1
Sidjanin, D. J. (2002). Canine CNGB3 mutations establish cone degeneration as orthologous to the human achromatopsia locus ACHM3. Human Molecular Genetics. View the article
Yeh, C. Y., Goldstein, O., Kukekova, A. V., Holley, D., Knollinger, A. M., Huson, H. J., … Komáromy, A. M. (2013). Genomic deletion of CNGB3 is identical by descent in multiple canine breeds and causes achromatopsia. BMC Genetics, 14. View the article
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