Type A-PRA Test

For: Miniature Schnauzer

• Breed Links

 There is good news on the Miniature Schnauzer PRA research front!

Scientists at the Baker Institute, Cornell University College of Veterinary Medicine, found a mutation in one of the genes that cause PRA – Progressive Retinal Atrophy – in the Miniature Schnauzer.

Before you read any further, please be sure to pay careful attention to the fact that Type A-PRA is only one of two or possibly more forms of PRA that occur in this breed….some details follow.

The Research

The gene for Type A-PRA was discovered in a region of a chromosome being studied intensely by scientists at the Baker Institute. The mutation in this gene that causes one form of PRA disease in Miniature Schnauzer is accurately and reliably detected by a direct mutation test done on DNA isolated from a small sample of blood. Two further pieces of information were discovered and these are extremely important for use of the Type A-PRA mutation test to screen dogs before breeding.

First, this newly discovered gene/mutation, named Type A-PRA, is the cause of some but not all cases of PRA in Miniature Schnauzers. There appears to be at least two, or maybe even three, different genetic forms of PRA in this breed even though the clinical signs of PRA in all diseased dogs look exactly the same. One form of PRA cannot be distinguished from another form based on a clinical exam. (When a second PRA causing gene/mutation is discovered, it will be named Type B-PRA.) The significance of this is that a dog that is clear for Type A-PRA could still be at risk for having or carrying the other form of PRA. At this time, the relative frequency of Type A-PRA compared to other types in the Miniature Schnauzer is not known. We only know that Type A-PRA is an important and not infrequent form. More information on its frequency will be gathered as more dogs are tested.

Second, this newly discovered Type A-PRA is different from other forms of PRA studied so far because it has a partially dominant expression. That is, some carrier animals appear affected when examined clinically and/or by ERG. This is due to the biology of the disease and the function of the genes causing the disease. This is NOT due to any inaccuracy in the genetic test. Although most gene mutations act in a straightforward dominant or recessive fashion, there is ample evidence of similar situations known with human inherited diseases.

Results for the Dogs in the Research Project

For reasons of client/doctor confidentiality, scientists at the Baker Institute cannot release the test results of the research dogs without specific permission from each individual owner. Owners who donated blood samples for these studies and who want their results should contact the AMSC and request the form to fill out and submit in order to receive their results.

Breeding Recommendations

The Miniature Schnauzer Type A-PRA mutation, in contrast to other forms of PRA, can cause disease in some, but not all, carriers. Therefore, OptiGen recommends only clear by clear breedings to prevent Type A-PRA. Neither tested affecteds (both genes of the pair are mutant) nor carriers (one gene of the pair is mutant, the other normal) should be used in breeding programs.

All dogs testing affected have or will have Type A-PRA. Some dogs testing as carrier have or will have symptoms of Type A-PRA, although some carriers will not have disease symptoms. If the tested dog is a carrier, it will transmit a mutant gene to approximately 50% of its offspring. If the dog tested affected, it will transmit a mutant gene to all of its progeny.

If a dog tests clear for Type A-PRA, but has a parent or grandparent that has had a clinical diagnosis of PRA (Type unknown), OptiGen strongly recommends that the ancestor with PRA be tested for Type A-PRA. If that ancestor tests clear for Type A-PRA or is not available for testing, one should proceed as if that ancestor dog has some type of PRA and the descendent dog should not be bred due to high risk of carrying some form of PRA other than Type A-PRA.

Finding the other PRA Genes in Miniature Schnauzer

Research on Miniature Schnauzers is continuing in order to identify the remaining genes that cause other types of PRA.

You can help if you have a dog that has a documented diagnosis of PRA. OptiGen will test dogs that have a CERF or ACVO or comparable clinical exam report stating that PRA has been diagnosed. The owner can submit the dog’s blood sample with a copy of exam records, along with the dog’s pedigree and a statement permitting use of this dog’s blood sample for research purposes if it tests clear for Type A-PRA. There will be no charge for tests on PRA-affected dogs. Please read the notice on the News & Updates page and/or call OptiGen for details in advance of sending this sample.

The Genetic Test

The genetic test for Type A-PRA is available exclusively from OptiGen due to licensing agreements. Please use the “Request Test” form and follow the “Ship Sample” instructions found on this web site through links on the Home Page or on the menu bar.