The private company that gave the world the human genome on Monday claims that it has now assembled the mouse genome as well.
Researchers chasing the same goal for a rival consortium of companies and publicly-funded institutes are sceptical, however. 鈥淚鈥檒l believe it when I see the publication,鈥� says Tim Hubbard, head of genome analysis at the Sanger Centre in Cambridge, a member of the consortium.
But no-one is in any doubt about the importance of mouse DNA to cracking the mysteries of our own genes. The mouse genome is extremely similar to ours, differing by as few as 200 to 300 genes. It should therefore provide a 鈥淩osetta stone鈥� for establishing the functions of human genes.
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Individual genes can be knocked out in mice, to see what effect this has on the animal. The function of its human counterpart is likely to be very similar.
Humans have about 30,000 genes but no function is known for 40 percent of them. Given that it would be ethically unthinkable to knock out genes in humans, mice should provide an indispensable way of finding out what they do.
Shotgun sequencing
Celera Genomics, the company founded by controversial gene entrepreneur, Craig Venter, began sequencing the mouse in April last year. It deployed its trademark 鈥渨hole genome shotgun鈥� sequencing technique, also used for its version of the human genome, now published in Science.
For the mouse genome, this involves tearing 3.1-billion-long string of DNA letters into tiny fragments, reading them and then reassembling them into the correct order.
To ensure no bits are missing, the company smashed up over five copies of the mouse genome, a total of 15.8 billion letters altogether. They included DNA from the most widely-used strains of lab mouse.
Mix and match
Because the human and mouse genomes are so similar, Venter was able to position the mouse fragments by 鈥渙verlaying鈥� them on the human genome, which he claims is virtually complete. Now he says the assembly of the mouse genome is 99 per cent complete.
鈥淐elera is continuing to refine this assembly and now begins the annotation, or analysis phase,鈥� says a company press release.
Hubbard agrees that it ought to be possible to overlay the mouse on the human genome. But there might be some mistakes doing it this way, he says, because human genes are longer. There might also be mistaken matches with the many duplicated regions of the human genome.
The rival mouse sequencing consortium is steadily doing the job region by region, rather than all at once like Venter. This 鈥渕apping鈥� approach was used by the publicly-funded effort to sequence the human genome, now published in Nature.
鈥淲e鈥檝e not got an assembly for the mouse genome yet,鈥� says Hubbard. 鈥淏ut we should complete threefold coverage of the genome by the end of March.鈥�
More at: Human genome analysis reveals far fewer genes than expected
