Dogs share most genes with humans

Carl T. Hall:

Scientists are publishing today the complete DNA sequence that makes a dog a dog, and it turns out to be uncannily close to what makes a person a person.

Genome sequencers at Harvard University, MIT and their affiliated Whitehead Institute for Biomedical Research in Cambridge, Mass., led an international team of scientists through a unique landscape of doggie DNA.

About 2.4 billion chemical units of DNA define a species uniquely shaped by people ever since dogs left the wolf pack and joined our human ancestors at least 15,000 years ago. Accurately mapping the dog genome took about two years and $30 million. Canis familiaris is the latest species to have its genetic code mapped, following that of the rat, mouse, fruit fly and, most famously, the human.

A report on the work appears today in Nature, the British science journal.

Simultaneously, Cold Spring Harbor Laboratory on Long Island devoted the December issue of its journal "Genome Research," exclusively to canine studies, and produced a book, "The Dog and Its Genome," co-edited by the Whitehead Institute's Kerstin Lindblad-Toh, lead author of the genome study.

Researchers note that dogs share many of the same gene-related health conditions as humans, including cancer and obesity. They have about 19,300 genes, scientists estimate, all but a handful close copies of human genes. Although humans have half a billion more DNA units, or "base pairs," that's mostly because humans are thought to have more silent stretches of so-called junk DNA.

"It's basically the same gene set in dogs and humans," Lindblad-Toh said during a telephone interview this week.

Dogs attract keen research interest in part because of their astounding variety of sizes, physical forms, coat colors and, of course, behavioral traits. If some of these variations can be traced to genes, results may shed light on more subtle variability in other species, including humans.

The task is made more manageable because the same breeding programs that generated the 350 or so modern dog breeds also left precise records of lineages going back many generations. These are tied in some cases to detailed medical records and observations by trainers and owners -- a treasure trove in the era of comparative genomics.

After hundreds of years of selective inbreeding, many of the most prized purebreds have a high risk of genetic maladies. Discovery of a narcolepsy gene in Dobermans, for instance, helped scientists understand what caused the human form of the sleep disorder.

"The dog is a good model for human disease," Lindblad-Toh said. "They are highly intelligent, social animals, and we interact with them in the same environment."

Just goes to show that genetically similar organisms can be very different.