Identification of gene mutation makes screening possible

Researchers at the at the Michigan State University College of Veterinary Medicine (MSU CVM) have developed a DNA-based test to detect one of the types of progressive retinal atrophy (PRA) in papillons. The test was developed after the team discovered a gene mutation for this form of PRA in papillons.

Dr. Simon Petersen-Jones, Dr Vet Med, PhD, CVM professor, and Myers-Dunlap Endowed Chair in Canine Health, and PhD Student Paige Winkler in the MSU CVM Comparative Ophthalmology Lab identified the gene mutation. Dr. Kari Ekenstedt, DVM, PhD, at the University of Wisconsin-River Falls collaborated with the MSU team on this research. Support from the Papillon Club of America and Papillon owners and breeders made the work possible.

There is more than one type of PRA in papillons. This form is being called PRA Type 1 (PRA1).

• PRA1 causes the earlier onset form of the disease, resulting in night blindness and a slowly progressive retinal degeneration.
• PRA1 is recessively inherited—for a dog to be affected it has to inherit the mutated gene from both its parents and is therefore homozygous for the mutated version of the gene.

DNA test for PRA1 in Papillons

A DNA test is being offered through the Comparative Ophthalmology Lab at MSU CVM. This test identifies genetically-normal dogs, PRA1-carrier dogs, and PRA1-affected dogs.

This test identifies only one of the forms of PRA in papillons—it is still important to get regular CERF examinations performed on your breeding dogs, even if they have been cleared for PRA1.

Making informed breeding decisions

This new test can help breeders make informed breeding decisions. DNA testing allows breeders to safely breed PRA1-carrier dogs with genetically-normal dogs. This prevents passing on the disease without restricting the available gene pool. PRA1-carrier dogs with positive characteristics can be bred for those traits worth preserving. Limiting the dogs used for breeding in an attempt to rapidly eradicate a particular condition like PRA can cause the emergence of a genetic problem for which there is no genetic test.

It is important to be aware that there is more than one type of PRA in Papillons. This DNA test will only identify the PRA1 mutation. Research will continue until all additional gene mutations that cause PRA in papillons are found.

Papillons that have been diagnosed with PRA by a veterinary ophthalmologist (e.g., at a CERF clinic) will be tested for PRA1 at no charge. This will enable us to find out what percentage of PRA in papillons is due to the PRA1 mutation. A copy of the CERF form or report from the veterinary ophthalmologist must accompany samples.