Brussels, 02 Apr 2004
An international consortium of scientists has sequenced the genome of the Brown Norway rat, which many predict will deliver a boost for medical science as well as our understanding of evolution.
The rat's is the third mammalian DNA sequence to be deciphered, following the human and mouse genomes. Sequencing it was a priority for researchers, due to the widespread use of rats in medical research.
The sequence itself, published in the journal Nature, is made up of some 25,000 genes, 90 per cent of which have a match in the human and mouse models. This means that nearly all disease-related human genes have a counterpart in the rat, which should ensure better rat models for researching human diseases and provide new targets for treatments.
'You cannot over emphasise the importance of having a complete database like this,' said Dr Richard Gibbs from Baylor College of Medicine in Houston, USA, who coordinated the international sequencing effort. Teams from various institutes in the UK, Germany and Sweden were involved in the project.
The rat genome was documented by combining methods from the human and mouse genome project to produce a highly accurate sequence. 'This makes it more efficient and thorough than previous genome sequences,' added Dr Gibbs.
The sequencing effort has already led to some interesting discoveries. For example, among the ten per cent of rat genes that have no match in the human genome are a number that make up the code for smell related proteins, which could explain rodents' exceptional sense of smell.
Rats also have more genes designed to break down toxins than humans do, which could have consequences for drugs testing. If indeed rats are better able to break down toxins than humans, then researchers will have to re-evaluate the practice of using rats in toxicity tests for human drugs.
Comparisons between the rat and human genomes also suggest that the pace of evolution in the rodents is up to three times faster than in people, as the rat genome is much more diverse. It may be this genetic diversity that has allowed rats to colonise a wide range of habitats all over the world.
In an effort to gain further insights into evolution, Dr Gibbs and his colleagues will now turn their attention towards sequencing the genomes of the cow, macaque monkey and sea urchin. 'This should help us to refine our evolutionary comparisons,' concluded Dr Gibbs.
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