Dog Genetics Are Model System

By Marlene Cimons, National Science Foundation

While geneticists have learned a great deal in recent years about the evolution of breed dogs, they still don’t know very much about the origins of “village” dogs—those semi-feral dogs we often call “mutts,’’ or strays.

Scientists believe that studying village dogs can provide vital new information about dog domestication and evolutionary genomics. “Dogs really are a powerful model system for understanding how evolutionary forces influence genetic variation among populations,” said Carlos Bustamante, a professor of genetics at the Stanford University School of Medicine.

The village dog project grew out of a major three-way collaboration examining dog genetics and evolution, which also includes Robert Wayne, UCLA professor of ecology and evolutionary biology, and Elaine Ostrander, chief and senior investigator, cancer and genetics branch of the National Human Genome Research Institute.

Ostrander studies genes important in growth regulation, particularly as they apply to human and dog diseases. Among other things, her group has constructed high-density comparative maps of the canine genome and has been able to map genetic loci for several dog cancers, Addison’s disease, osteoarthritis, and other disorders. Cancer is of particular interest to her group and is the major focus of its canine disease studies.

Earlier this year, Wayne’s team at UCLA released a National Science Foundation (NSF) funded study showing that most breed dogs can trace their origins to Middle Eastern wolves, not Asian or European wolves as previously thought. This research involved analyzing genetic data from more than 900 dogs from 85 breeds, including all the major ones, and more than 200 wild gray wolves worldwide, including populations from North America, Europe, the Middle East and Asia.

The work also produced the first evolutionary tree of dog breeds, showing a surprising structure that suggested that new breeds were developed from crosses within specific breed groups that share particular traits.

These studies focused on breed dogs are key to identifying genetic differences among breeds. “But there was a piece missing—village dogs,” Bustamante said.  “These are dogs that are not pure-bred dogs, who can hearken back to pre-breed diversity.”

Bustamante, who recently was among those named to receive a prestigious $500,000 MacArthur “genius’’ award, a “no-strings attached’’ fellowship, said there is a strong scientific rationale for studying village dogs.

“If we think about dogs, they live in different types of worlds,’’ he said. “Breed dogs, we keep in our homes. Wolves live in the wild and are subject to natural selection. Then you have village dogs, which are somewhere in between. They have undergone some degree of adaptive change, living near humans but still are subject to natural selection, the way wolves are. So by studying them, we can get a much better picture of the evolutionary process.”

Bustamante is leading a project, believed to be the largest of its kind, to genotype stray dogs around the world. He and his team, who began the effort while at Cornell University, have collected blood samples from more than 1,200 village dogs found in dozens of different countries on five continents. To do so, they enlisted the help of numerous local researchers, shelters and veterinarians.

“The procedure involved talking to locals to find dogs that were living in the community, or working with shelters to sample shelter dogs that had been brought there from the around the area,” said Adam Boyko, a research assistant in the department of genetics who is directing the sampling effort. “Dogs were briefly muzzled for safety, and then weighed, measured and photographed before 3-5 milliliters of blood was drawn for an analysis.”