4th quarter 2005

Dog genome project helps scientists gain a better understanding of human diseases

Dogs have always been man's best friend. They help in hunting and herding animals, but also fulfil complex human needs when kept as pets. Dogs were domesticated earlier than any other animal (more than 15,000 years ago), probably in southeast Asia. All modern dogs are descendants of wolves. The obvious differences between them, such as in size and behaviour, have been brought about by breeding. Dogs thus provide a unique genetic model. Due to inbreeding, dogs of the same breed are genetically very similar. This makes it easier to trace certain breeding traits (such as size or aggressiveness) back to their genetic sources.

The complete genome of a female boxer dog has now been deciphered. The dog genome is somewhat smaller than the human one. It is made up of 2.4 billion (compared to 3.2 billion) letters, and has slightly fewer genes. The most important 5% of the human genome can largely be found in dogs, too. There is about as much genetic difference between two humans as there is between a boxer and a poodle (every thousandth letter).

This is why scientists are using animals to study fundamental biological questions, most of which are relevant to humans, too. There are many biological functions which were optimised at a very early point in the evolution. These genes have not changed much since then. As a result, humans, dogs, mice and many other animals today share a substantial number of identical or similar genes.

There are a few hundred genetic disorders which may affect both humans and (specific breeds of) dogs, such as narcolepsy (uncontrollable episodes of sleeping) in dobermans or renal cancer in German shepherd dogs. The genetic homogeneity of dogs — a product of breeding — makes it easier to identify the gene responsible for a particular disease in canines than it would be in human subjects. Researchers can thus identify genetic disorders in dogs, and follow this up with therapeutical experiments relatively easily. This means that the causes and therapies of human diseases can be studied in the same model organism.

In the area of environmental effects, the WHO study discusses a variety of aspects, for example the reduced need for chemicals in agriculture and for chemicals and waste water in the industrial sector, the introgression (penetration of one population's genes into the genome of another) of transgenic DNA into traditional Mexican maize strains, the StarLink case, the case of the Monarch butterfly and the extensive studies in England on the effect of GM plants on biodiversity, which are based on the world's largest outdoor trial.

Overall, the sequencing of the dog genome marks another milestone in genetic research. It will help provide a better understanding of medical issues and fundamental questions of evolution.