The strict breeding practices that produce champion purebred dogs are proving a boon to geneticists. New results reported in this week's Science and at a genome meeting held last week at Cold Spring Harbor Laboratory on New York's Long Island suggest that our pedigreed canine companions may be a major help in finding the genetic keys to common human afflictions such as cancer, diabetes, and mental disorders.
What is it about dogs? Purebred dogs are, well, pure. Within a breed, they have less variation in their DNA sequence than do humans. So geneticists have been focusing on the dog as a possible model for gene searches because this lack of sequence variation may help them circumvent a frequent problem with studies in humans. When seeking the genes at fault in a disease, they find all too often that the trail goes cold because there aren't enough members of affected families or isolated groups of people to pin down the genetic risk factors.
But to get the most out of canine gene hunts, geneticist Elaine Ostrander and her colleagues at the Fred Hutchinson Cancer Research Center in Seattle, Washington, realized that she needed to know the degree of genetic differences among various breeds. She and graduate student Heidi Parker set out by identifying variations in 96 microsatellites--short pieces of unique sequence that serve as landmarks for gene seekers--in 414 dogs from 85 breeds. The researchers identified a clear set of microsatellites specific to each breed. The findings should aid in tracking down disease genes, says Ostrander. If she is looking for a gene in one breed, she can now expand that search to other breeds shown to be related by their microsatellite composition. Having a larger sample will make it easier to detect the mutation at fault. “This is what I see as the most powerful use of the data,” she notes. At the same meeting, Kerstin Lindblad-Toh of the MIT Broad Institute in Cambridge, Massachusetts, and her colleagues outlined the initial analysis of the 2.4 billion bases of the dog genome. They described their progress sequencing the genome of a boxer named Tasha, chosen because the breed has very little genetic variation. Once that goes public, which should occur in the next few weeks, finding disease genes in dogs will be even easier.