genesDog breeds shed light on human disease

Pedigree dogs could help scientists identify genes involved in rare genetic disorders, a new US study shows. Researchers at the University of Washington looked at DNA samples from 85 different dog breeds, and found that each has a unique 'genetic signature'. The team, who published their findings in the journal Science, say the information should help geneticists decide which breeds will be most useful for studying a particular human or dog disease.

Scientists produced a rough draft of the entire canine genome in September 2003. Analysis revealed that 18,473 of the estimated 24,567 dog genes have human equivalents. The dog genome sequence is made up of around 2.4 billion DNA base-pairs, or 'letters', whereas humans have around 2.9 billion. According to Francis Collins, director of the National Human Genome Research Institute, a lot of researchers are now 'primed to take that sequence and leap forward' to study human genetic diseases.

Following 300 years of selective breeding, pure-bred dogs all have a particular set of inherited traits, including some disorders. Described as 'a geneticist's dream', dogs are ideal for tracking down genes, because each breed represents a group of genetically similar animals that are descended from just a few animals. In the latest study, the scientists measured the amount of genetic variation present in 414 different dogs from 85 breeds. The researchers looked at 96 variable DNA markers, and found that each dog breed, with very few exceptions, has a unique DNA fingerprint. They also found that they were able to sort the breeds into four groups of genetically similar varieties, which are thought to share common ancestors.

Study leader Elaine Ostrander said that each dog breed is like a little Iceland: 'an isolated population that allows us to simplify a complicated genetic problem'. Although there may be just as many genes for a given disease in dogs as there are in humans, she added, being able to search for them in a single breed 'allows us to find the one or two genes responsible for that disease in that population much more easily'. Researchers in Ostrander's group are hoping to use the dog data to identify genes involved in cancer, blindness and obsessive-compulsive disorder.