Mutation Test for prcd-PRA

OptiGen, LLC Press Release
June 1, 2005
Added information for the ECSCA

Ithaca, NY:  OptiGen, LLC, proudly announces identification of the gene causing canine prcd-PRA (progressive rod-cone degeneration form of Progressive Retinal Atrophy). The cause of this inherited blinding disease, occurring in at least a dozen purebreeds, is one specific mutation in the coding sequence of the gene. OptiGen now offers a direct gene mutation test (mutation test) to detect the prcd-PRA status of any dog among affected breeds.

This success results from years of extensive investigation by Dr. Gus Aguirre and Dr. Greg Acland and their research staff at Cornell University. Essential cooperation from multiple breed clubs and more recent participation by OptiGen completed the team. The research data defining this mutation are being prepared for publication in a scientific journal. Commenting on future work, Dr. Aguirre says: “Going forward, the biological action of the prcd gene in the retina will be studied, with goals of understanding the basis of this disease and searching for treatments or even, eventually, cures.”

The new OptiGen prcd mutation test accurately detects the presence or absence of the mutant prcd disease gene copy. It replaces earlier OptiGen DNA-marker-based tests (marker tests) that detected changes in coding sequences of genes located near to and inherited with (linked to) the prcd gene. OptiGen henceforth defines result status based on the mutation test as “Normal/Clear” or “Carrier” or “Affected.” Designation of Patterns A(A1), B(B1), and C(C1) for previous marker tests are retired.

While the basic research of Aguirre and Acland spans decades, OptiGen’s prcd-PRA test evolved over the last 7 years, with the first marker test offered to Portuguese Water Dogs in 1998. Initially it detected false positive alleles. Subsequently, improved versions of the marker test analyzed coding sequence changes in more tightly linked genes and greatly reduced the frequency of false alleles. This improved marker test accuracy and gave an excellent estimate of prcd-PRA frequency within affected breeds.

A crucial set of information for proof of the prcd mutation was generated by OptiGen, according to Dr. Jeanette Felix, President. Between March 1, 2004 and May 31, 2005, OptiGen had added the potential mutation test to the standard marker test for all new samples from prcd-affected breeds in order to validate the identity of the mutation in large populations. Analysis now shows that the results are consistent between the marker test and the potential mutation test.

The prcd mutation test further improved accuracy over the marker test for Labrador Retrievers and Miniature and Toy Poodles. Only these groups will receive updated test reports by mail during June. For all other breeds, there was no difference in the outcome between marker and mutation tests. Given this match, OptiGen will not retest other breeds originally tested before March 1, 2004. All test reports that gave Pattern status can be interpreted as:  Pattern (A)A1 = Normal/Clear; Pattern (B)B1 = Carrier; Pattern (C)C1 = Affected.

Statistics based on the new mutation test show that the frequency of prcd-PRA varies substantially among breeds, ranging between 4% to 20% affecteds and 20% to 50% carriers.  Dr. Acland emphasizes: “Genetic testing used in informed breeding programs clearly is essential for preventing new cases of vision loss. I expect more genetic tests will be developed as canine genome research accelerates. Breeders with experience using the prcd-PRA test will be eager to make use of all new genetic information.”

The prcd-PRA mutation test can be obtained following the same procedures as before – see As of June 1, 2005, the fee for the prcd-PRA test is reduced 25%, down to $195. Opportunities for discounts for litters, through online ordering and 20/20 Clinics continue.

The Morris Animal Foundation/The Seeing Eye, Inc. is a major sponsor of research by Drs. Acland and Aguirre. Grants from the NEI/NIH, the Foundation Fighting Blindness and The Van Sloan Fund and contributions from many breed clubs, organizations and individuals are gratefully acknowledged. Many club health committees and breeders gave welcome encouragement as well as invaluable samples and information on their breed lines.

OptiGen, LLC, is a private company established to provide canine genetic tests to breeders and owners of purebred dogs, their veterinarians and other veterinary specialists. OptiGen holds an exclusive international license to the Cornell University technology for prcd-PRA mutation testing, and exclusive and non-exclusive licenses to multiple other technologies developed at Cornell and elsewhere.

Added information for the ECSCA

OptiGen tested about 400 ECSs with both the improved marker test and the potential (now real!) mutation test. There was no difference in the results, giving a probably of less than 1 in 400 of a result being different with the mutation test compared to the marker test. This means that the best marker test was accurate for ECSs, even though it didn’t detect the real mutation.

OptiGen does not plan to retest ECSs, and we do not encourage owners to request a retest. If they do, the regular fee will be charged. For test reports dated prior to May 31, 2005, A1 = Normal/Clear, B1 = Carrier and C1= Affected.

We have also retested the pedigrees of extremely late onset PRA, that had multiple members testing as Pattern C1. All of the C1 dogs are “Affected” with the mutation test. That leaves us with the theory that this subgroup inherits prcd-PRA but also must inherit an unidentified second gene that modifies the onset of PRA, causing some “Affecteds” in the pedigree to exhibit typical prcd-PRA, and some retain good vision throughout their lifetime. Unfortunately, we do not have any more satisfying explanation for the situation. Hopefully it will be more clear with ongoing research.

Thanks for helping us reach this point and thanks for sharing the excitement!

Jeanette S. Felix, Ph.D.
President and Manager
OptiGen, LLC
Cornell Business & Technology Park
767 Warren Road, Suite 300
Ithaca, NY 14850

phone: 607-257-0301
fax: 607-257-0353

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