Scientists take a snap of man's best friend

[DoozyDog]

Mapping the genes of dogs is expected to provide insights into human diseases

By Gareth Cook
January 19, 2006

Scientists in the US have finished a sophisticated map of a dog's genes, providing new insights into the deep links between humans and one of their most treasured animals as well as creating a unique tool for studying diseases, from cancer to blindness, that affect people as well as dogs.

The scientists, led by the Broad Institute of Harvard and Massachusetts Institute of Technology, determined almost the entire genetic code, or genome, of the dog, the canine equivalent of the completion two years ago of the Human Genome Project.

Rough drafts of the dog genome have been released over the past several years, but the new work represents the first highly accurate version and includes, for the first time, a detailed library of common genetic variations seen in dogs - making possible a new generation of fast, accurate genetic studies of diseases and other traits.

Biologists have taken up the genetics of many animals, but the dog is uniquely interesting and useful, the scientists say, because of its history. The several hundred breeds of modern dog are the product of thousands of years of careful breeding, aimed at drawing out specific behaviours, such as the obsessive herding of the border collie, or appearances, such as the hairless Chinese crested. By applying the modern tools of genetics to these breeds, it is now easy to find the small genetic variations responsible for the differences, with applications from dog breeding to human psychiatry.

"It is a historic day in the relationship between man and dog," Eric Lander, director of the Broad Institute and the owner of two golden retrievers, said at a press conference.

Scientists say the dog also stands as a testament to the power of evolution - and its importance - at a time when some are challenging its teaching in public schools. Looking for the genetic causes of human diseases in dogs makes sense only if humans and dogs are close evolutionary relatives that share a common ancestor - a fact strongly supported by the genetic map Lander and his colleagues found. "Biomedical research today depends on evolution," he said. "It is hard to say that it is 'just a theory'."

The research, reported in the journal Nature, was led by Kerstin Lindblad-Toh, co-director of genome sequencing and analysis at the Broad Institute. Using a blood sample from a boxer named Tasha, the team determined about 99 per cent of the sequence of DNA that makes up the dog genome.

The team, which included researchers across the US as well as in France and the United Kingdom, also compiled a list of 2.5 million places in the sequence where there are common differences among dogs. This was done, says the Nature paper, by comparing Tasha's DNA with DNA from a poodle and other breeds - enough to record many of the most common variations in dogs.

Having a list of common differences will make it far easier for researchers to do genetic studies involving large numbers of dogs, because they can focus on the places in the genome where dogs are likely to have differences that might explain why one dog gets bone cancer and another does not. For example, scientists who are interested in why some greyhounds get bone cancer, and others do not, can look at these places to see if there is a pattern, without having to determine the entire genetic code of each dog - about 2.4 billion molecules long. "This is really the big thing," said Gregory Acland, a senior research associate at the Institute for Animal Health at Cornell University.

Many ailments - such as cancer, epilepsy and heart disease - are thought to be similar in dogs and humans, but it will be easier to identify the genes involved using dogs, said Acland. In contrast with humans, dog breeds are highly inbred, making two dogs in the same breed more similar genetically than two humans. Thus, scientists could compare Dalmatians that are deaf with those that are not deaf, and there would be fewer random genetic differences between the dogs to cloud the picture.

The work, and follow-up work planned to study specific diseases, were made possible by the American Kennel Club and dog owners who agreed to send in blood samples from their pets. (There is more information at http://www.dogdna.org.)

Dogs are a human creation, thought to have begun when people domesticated the wolf in East Asia. The new analysis suggests that this happened about 30,000 years ago, said Lindblad-Toh.

Yet there is also irony in discovering the scientific potential of dogs, noted Mark Neff, a scientist at the Centre for Veterinary Genetics at the University of California, Davis. "We are so close to our pet dogs that we stop thinking of them as this incredible, unique species," Neff said.

The New York Times