The Geneticist's Best Friend

Dogs are helping to hunt down more than foxes and lions: Researchers are increasingly relying on them to track down genes and pathways involved in canine and human diseases

Talk about blind faith. Twenty years ago, Gustavo Aguirre and his colleague Gregory Acland were struggling to understand a common cause of inherited blindness in dogs. They had bred affected and unaffected individuals and traced the inheritance patterns in the offspring, but "there was no hope of finding the gene," recalls Aguirre, a veterinarian at the University of Pennsylvania's School of Veterinary Medicine in Philadelphia. At the time, researchers hadn't even assigned numbers to the canine chromosomes, let alone begun to map the locations of genes. Nonetheless, "I decided that in the future, someone somewhere would come up with [a way] to come up with the gene," he says. So they banked blood from their dogs and waited.

Their patience paid off. A decade later, their freezers provided the raw material for a linkage map of the dog genome and, eventually, the discovery of the long-sought gene for progressive rod-cone degeneration. With that map as a starting point, researchers have built a community that has proven the value of dog genetics not just for veterinarians and dog breeders but also for human geneticists.

Dogs are a geneticist's dream. Pure breeds, as the name implies, are often highly inbred for specific traits. They have large families and well-documented genealogies, all of which greatly simplifies the task of tracking down mutations that cause disease or genes that underlie traits such as size, coat color, or even behavior. And the link to humans can be direct: The top 10 diseases in dogs include cancer, epilepsy, allergy, and heart disease--disorders that affect many millions of people. Also, because dogs live in the same environment as people, they share some of the same environmental risk factors. As a result, more and more researchers, including a consortium about to be announced in Europe (see p. 1670), are turning to the dog for clues to human genetics. "All of a sudden, people from a wide range of disciplines can see the value, power, and practicality of genetic studies in dogs to shed light on issues of concern to them," says Acland, a geneticist now at Cornell University.

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