Scientists have produced a rough map of the genetic blueprint of dogs. The map, published in the current issue of Genomics, should be a useful guide for veterinary researchers to home in on disease-causing genes common to certain breeds--work that could provide clues to similar diseases in people.
Centuries of intensive inbreeding has yielded more than 300 distinct breeds of dogs with a range of genetically defined shapes, sizes, and temperaments--as well as an extremely high risk of developing genetic diseases. Many of these diseases--from hip problems to epilepsy to blindness--also occur in people. But it's easier to study such diseases in dogs because they have more offspring, shorter life-spans, and less genetic diversity than humans. "Every dog breed is like a genetic Finland"--a country whose small population with little influx of foreign genes is often studied for genetic disease incidence--says Elaine Ostrander, a molecular biologist at the Fred Hutchinson Cancer Research Center in Seattle.
Ostrander and postdoc Cathryn Mellersh set out to map the dog's genome using unique genetic markers as signposts to genes of interest. The team found 150 of these inherited molecular signposts and then turned to Cornell University study co-author Gustavo Aguirre, who studies genetic eye diseases in canines, for genetic samples from dogs he has bred for other projects. The team located the precise positions of these markers in DNA from 17 three-generation dog families, totaling 212 individuals, eventually piecing together a map with a marker every 14 million DNA bases on average. (The current human genome map has a marker roughly every 1 million bases.) "It's like having a map with states and cities, but still no streets," says Ostrander. "Instead of looking for a needle in haystack, researchers can now look for a needle in a cup of hay."
Ostrander's team did "extraordinary" work, says Linda Cork, a veterinary pathologist and chief of comparative medicine at Stanford University. Now, "we can begin to look at the genetics of these complex behaviors and traits" in a way that's not possible in people, she says. Cork hopes to use dogs to study neurological diseases--such as like Alzheimer's and Parkinson's--that occur late in life in people and thus are difficult to trace through family trees.