Dog gene map may help explain human diseases

U.S. scientists say a detailed analysis of the dog genome answers such questions as how dogs of a different breed still belong to the same species, and may also explain some aspects of human health and biology.

A U.S. government-funded study has assembled the complete genetic map of an inbred boxer named Tasha which not only helps explain how poodles differ from jackals, but might offer insights into bone cancer, blindness and epilepsy, say the researchers.

According to Dr Eric Lander, a gene expert at the Broad Institute at the Massachusetts Institute of Technology and Harvard University, who helped coordinate the study, the knowledge will make the identification of many disease genes 50 times easier.

Lander believes in the next three to four years it will become possible to identify a gene for bone cancer in dogs.

In the study researchers at 15 institutions described how they compared the genetic blueprint of the boxer with 10 other breeds.

They also compared the dog genome to the already-completed maps of human genes, mice, rats and chimpanzees.

The team, led by the Broad Institute's Kerstin Lindblad-Toh, sequenced the 2.4 billion letters of Tasha's DNA, representing 39 pairs of chromosomes.

There is apparently one big difference between dogs and people, human genes are found on just 23 pairs of chromosomes.

The researchers also compiled a catalog of 2.5 million single-nucleotide polymorphisms, one-letter changes in the genetic code, that differ among the 10 breeds of dogs studied.

The genes that make some dogs big and others little, that give some dogs long snouts and others pushed-in faces, and that predispose some dogs to certain diseases provides an excellent basis for studying biology, medicine and evolution.

Hans Ellegren of Uppsala University in Sweden says the hundreds of years of careful inbreeding to produce the various breeds have delivered a geneticist's dream model for human genetic disease.

It was back in 2003 that teams at the Institute for Genomic Research and genome entrepreneur Craig Venter's Center for the Advancement of Genomics in Rockville, Maryland, published a genetic map of Venter's pet poodle.

But the current U.S. government-funded study is apparently more complete and systematic.

Lander says that up until now they only had little shreds of the dog genome, whereas now they have 'the entire book from end to end, ready to read'.

The researchers held a news conference at a dog show in Massachusetts, and it was clear they were dog lovers.

According to Lander the incredible physical and behavioral diversity of dogs is encoded in their genomes, and it can uniquely help us understand embryonic development, neurobiology, human disease and the basis of evolution.

Elaine Ostrander, chief of cancer genetics at the National Human Genome Research Institute, agrees that dog genetics could help narrow down the search for human disease genes.

Ostrander says the leading causes of death in dogs are a variety of cancers, and many of them are very similar biologically to human cancers.

Dr. Matthew Breen, associate professor of genomics at North Carolina State University, who worked on the project, also says that dogs have many habits similar to humans, and the cancers that dogs get are exactly the same as the cancers that humans get.

The study and the comments relating to it are published in the science journal Nature.