DNA Progressive Retinal Atrophy Research in Mastiffs

How you can help put an end to PRA
  by Kimberley Wall

You may know by now that Progressive Retinal Atrophy (PRA), a genetic disease that eventually leads to blindness, is becoming a problem in our breed. CERF's January 1991-December 1995 report for Mastiffs shows that 13 Mastiffs have been CERF-diagnosed with generalized PRA during that time period. The report also lists two other Mastiffs as "PRA-suspect."

The retina has specialized rods and cones (called "photoreceptors") that absorb the light that is focused upon them by the lens of the eye. The rods govern vision in dim light; the cones ... in bright light. Generalized PRA -- the form of PRA that appears to be the one that affects Mastiffs -- usually strikes the rods in the beginning. This is why night vision is often the first to go in an afflicted dog. Perhaps the dog is afraid to go out at night, or won't navigate though a dimly-lit room. As the disease gradually works on destroying the cones, the dog's daytime vision begins to fail. Meanwhile, the pupils become more and more dilated, causing the eyes to "shine." Cataracts may also result.

PRA does not come out of thin air. If a dog has PRA, BOTH parents must at least be carriers. The recessive PRA gene is a hidden monster. It can be dormant for generations, until paired with another recessive PRA gene from another dog. The Canine Eye Registration Foundation recommends that dogs who have PRA or who are known carriers (the parents and offspring of an afflicted dog) should not be bred. You should be aware that a dog can "CERF" clear before PRA is advanced enough to be detected ... and remember that a CERF exam cannot detect the recessive PRA gene.

Deb Jones, (who co-created and maintains the DeVine Farm Mastiff Pedigree Program), has been researching the pedigrees of five of the Mastiffs that she knows have PRA (having been told by their owners). These Mastiffs all come from well-known show lines. Several of their sires and dams are unrelated in the first four generations. One of these PRA-afflicted Mastiffs has 11 full siblings that have produced at least one litter, and none are registered with CERF. Another such dog's sire has 35 offspring that have produced at least one litter. Of the 35 offspring, 12 are champions, and only one has been registered with CERF. These 35 offspring have themselves produced 46 offspring that have produced at least one litter. Do you see how this disease can spread?

Researchers at Cornell University's James A. Baker Institute for Animal Health are working hard to identify what types of PRA are affecting certain dog breeds, and eventually develop DNA tests to screen PRA-afflicted and carrier dogs. This program is responsible for developing the PRA DNA test for Irish Setters. And now, Mastiff breeders and owners who have PRA-afflicted or carrier dogs are sending blood samples to the project, in the hopes that the form of PRA found in Mastiffs can be identified.

Once the researchers are able to identify the form of PRA affecting Mastiffs and the characteristics of the recessive PRA gene, the researchers can develop the test after a few months of hard work. Then, breeders can run blood tests on their breeding stock, to see who's normal, who's a carrier and who has or will develop PRA. Puppies can also be screened well before weaning. Thus, if someone has a Mastiff who carries the gene, it would be possible to breed that dog to a tested non-carrier and then screen the puppies, putting the carriers on limited registration and making sure they are spayed or neutered. This way, top-notch bloodlines do not have to be wiped out; you can preserve type while eliminating the disease. This is true genetic testing and how it can be used.

So, if you own a Mastiff with PRA or the sire, dam, grandsire, grandam or offspring of a Mastiff with PRA, please consider sending a blood sample to the Baker research team. Call Dr. Gregory Acland at (607) 256-5684 for details. The researchers say ANONYMITY IS GUARANTEED.

Even though the researchers will work on the Mastiff form of PRA if they get the needed blood samples, funds raised for this research will help speed up the progress. Much of the research team's current research is being bootlegged onto work funded for other projects. Direct funding for this kind of research is extremely limited. The basic support depends on federal funding for research on PRA as a model for human retinitis pigmentosa. Although this funding does support the research team's basic facilities, it does not directly support research into finding PRA genes. Think of the costs -- the blood kits, other equipment, general research procedures, etc. The Baker project can only stretch its own budget so far to research the various breeds -- including ours -- without additional funds.

During its May meeting, the MCOA Board of Directors voted to endorse the Mastiff PRA project, and to administer a fund for donations that would go specifically toward the Baker Institute's PRA DNA research in Mastiffs. The Baker Institute will be sending MCOA formal, annual reports on the research team's progress on the Mastiff research, plus informal updates when requested.

Therefore we have another request to make: please make a donation to end PRA and for the betterment of the breed. ANY amount at all would be a great help. We plan to recognize all contributors in future issues of the MCOA Journal. Please make checks payable to MCOA and send your donations to:

DONATIONS NO LONGER NEEDED - THANKS!
Deb Jones, MCOA PRA Research

This is now a MCOA-backed effort. Let's show our fellow dog fanciers that we are working to fight genetic disease. The researchers say it is possible that they could have this test developed in five years ... maybe even as early as TWO years. You can help prevent so many more Mastiffs from losing their sight.

Thanks in advance for your support. If you have any questions about PRA or the research project itself, please call me or send me your questions via e-mail.

Kimberley Wall
MCOA PRA Project