Ithaca, N.Y.-The English Mastiff dog breed is enabling scientists to help explain retinitis pigmentosa (RP) in humans.

Researchers at Cornell University and the University of Pennsylvania have discovered that this particular breed, which can carry a gene defect for progressive retinal atrophy (PRA) disease, is the best animal model of the human eye disease, RP.

"This research will greatly help in finding treatments and cures for these inherited forms of blindness in humans and eradicating the condition in dogs," says Gerald J. Chader, M.D., chief scientific officer of the Foundation Fighting Blindness, a sponsor of the study.

The dogs may be used to test therapies for the human disease, according to researchers at Cornell's Baker Institute for Animal Health and the University of Pennsylvania's Scheie Eye Institute.

Up to 100,000 humans in the United States suffer from the disease.

Recently Cornell scientists discovered the genetic mutation of a defective gene - RHO - which is causing PRA blindness in the English Mastiff. The study was reported in the April 30 Proceedings of the National Academy of Sciences.

Vision researchers had been seeking a large animal model for the human version of the eye disease since it was discovered in humans in 1990.

As a result of the research, scientists have developed a genetic screening test for dog breeders to help eliminate the defective gene from the line of purebred dogs.

Sponsors of the study include the National Institutes of Health and the Morris Animal Foundation.