Rat genome reveals supercharged evolution
18:00 31 March 04

Roughly 200 years after being tamed, bred and adopted as science's favourite
laboratory animal, the brown Norway rat has had its genome sequenced. It is
only the third mammal after humans and mice to have its genetic plan read.

Researchers say the feat will allow important human genes to be tracked down
more quickly, for example those related to cardiovascular disease or
behaviour, and will speed the creation of treatments for diseases.

Comparisons between the genomes is also yielding tantalising insights into
how each species evolved. The analysis has already shown, for example, that
rats have been evolving faster than both humans and mice. "We find that
rodent evolution is an order of magnitude faster than in humans," says
Richard Gibbs of the Baylor College of Medicine in Houston, Texas, and head
of the sequencing effort.

The regions evolving fastest are those associated the rat's acute sense of
smell and its use in detecting danger, marking territory and choosing mates.
Rats have an estimated 2070 smell receptor genes, about a third more than
mice, and also make more "pheromone" scents.

Smelly pipes

Rats have also zoomed ahead in the evolution of genes that help them
detoxify chemicals in their livers and elsewhere. "Rats occur in smelly
sewer pipes and yucky places, as compared with the mouse living in nice
clean fields, and that fits the model of how their genes develop," Gibbs
says.

By "knocking out" genes, it might be possible to genetically engineer rats
so that their detox machinery is identical to ours, improving the predictive
accuracy of toxicology and drug safety testing.

Similarities between the human and rat genomes are as important as the
differences. Researchers were relieved to find that almost all the human
genes linked with disease so far are identical in rats too, validating the
use of rats in their experiments.

The availability of the draft rat genome, covering 90 per cent of its
genetic code, should accelerate research on the genetic roots of inherited
disorders in humans.

"The identification of disease genes will in many cases be five fold quicker
with a [rat] genome sequence," says Kerstin Lindblad-Toh, at MIT's Whitehead
Institute in Cambridge Massachusetts.

Read the rest at NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99994840

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