Changing the way dogs are bred
By Amy Ettinger
Genetic tests identify at-risk dogs and prevent diseases
When a dog develops blindness, the condition can be devastating for both the animal and its human companion. Almost all breeds of dogs can be affected by degenerative eye disease. Fortunately, researchers have a new understanding of the genetic causes and have developed tools to help breeders identify at-risk dogs. As a result the number of dogs affected has been greatly reduced.
Researchers are now using genetic markers to identify a number of inherited diseases in dogs, ranging from cancer to progressive retinal atrophy (PRA). Genetic markers are pieces of genetic material, usually DNA, that can be used to identify different cells in an organism. Knowledge of these markers has led to diagnostic tools that can pinpoint which gene is causing a certain disease. Morris Animal Foundation has been funding research in this area for decades.
Genetic markers in sight
In 1993, Dr. Gustavo Aguirre received his first grant from Morris Animal Foundation and began looking for genetic markers for PRA.
“We were supposed to find markers, but we had no genetic map and no tools to develop a genetic map,” says Dr. Aguirre, a veterinary ophthalmologist and geneticist at the School of Veterinary Medicine at the University of Pennsylvania. The team of researchers began making a list of genes that could be involved with the disease. Every year, new genes were added.
“Little did we know that there were more than 200 genes that cause retinal disease in people,” Dr. Aguirre says. “Imagine at least that many in dogs.”
Dr. Aguirre and collaborators developed a genetic map in 1997 and then created a physical map that led them to find the marker for PRA. By finding the marker, Dr. Aguirre was ultimately able to develop a genetic test to identify which dogs carry the PRA gene. There is still no cure for the disease, but the creation of a genetic test has changed the way dogs are bred and helped reduce PRA’s prevalence.
Dogs that are carriers of the disease can and should be bred, says Dr. Aguirre. Otherwise, it can significantly reduce the gene pool and create potential long-term problems for the species, he adds. But that breeding should be done carefully.
“A dog that’s a carrier of the disease can be bred to a dog that isn’t a carrier, and the puppies will be unaffected by the disease,” says Dr. Aguirre. That is the main goal of breeding: not producing any dog affected with a disease, such as PRA, yet maintaining the genetic diversity within a breed.
The results of Dr. Aguirre’s research have greatly helped organizations like Seeing Eye Inc., which trains guide dogs. The organization collaborated with the Foundation to fund some of Dr. Aguirre’s earlier research on PRA.
Past funding from Morris Animal Foundation has allowed researchers at the University of Pennsylvania to identify the genetic causes for many types of blindness in dogs. From these discoveries DNA-based tests were developed for more than 11 retinal disease genes that are applicable to diseases affecting more than 47 different breeds of dogs.
Marking the spot for diseases
Dog owners can now turn to companies like OptiGen, a New York–based company established to provide DNA- based diagnoses and information about inherited diseases of dogs. OptiGen also offers a free PRA-testing program for pedigreed dogs that a veterinary ophthalmologist diagnoses as being affected by PRA. In addition, the company provides DNA tests for many other diseases common in specific breeds, ranging from neuropathy in Greyhounds to narcolepsy in Labrador Retrievers.
Researchers are working hard to uncover more genetic markers for more canine diseases. With Foundation funding, researchers at Cornell University are currently developing new tests for two genetically related disorders that cause abnormal liver function in small purebred terriers. The researchers hope to identify genetic markers for these disorders and then use the markers to develop a test for detecting at-risk dogs.
Scientists at Texas A&M University are looking for the genetic marker for hypertriglyceridemia, a condition that affects Miniature Schnauzers and occurs when a dog has high levels of triglycerides, which are fatty molecules in the blood that appear to be linked to several serious health problems, including insulin resistance, liver disease, pancreatitis and eye disorders.
Dr. Matthew Breen, a researcher at North Carolina State University, former member of one of the Foundation’s scientific advisory boards and now a canine cancer adviser, says genetic markers are also being used to break new ground with cancer research, from predicting which dogs will be diagnosed with cancer to developing the best treatments.
“We are also looking closely at the changes to genome organization that occur in cancer cells,” says Dr. Breen. “Already we have started to identify changes that are associated with subtypes of cancers and changes associated with response to therapy, which allows us to provide new information to the clinicians about duration of remission."
These advances are leading veterinarians to appropriate treatment options and are helping develop new targets for therapy. The results of canine cancer research may have a far- reaching impact, says Dr. Breen.
“A major positive side effect of working with dogs is that we are also able to use the data to translate to human cancers, and so by helping our dogs, we are also helping ourselves,” Dr. Breen says. “I predict that over the next five to 10 years we will learn more about the intricacies of cancer by studying our dogs than by studying people. Man and his best friend, side by side on the path to fighting cancer.”
Posted by MAFon August 26, 2011. Permalink