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Monday, August 1, 2011

Mouse gene knockout assembly

Researchers from the U.S., England, Germany and New Zealand have collaborated on a project (the International Knockout Mouse Consortium) to knockout every gene in the mouse genome.  They are over 40% of the way there.

If you want to know what a gene does, one of the most effective ways to find out is to eliminate that gene’s function and see how not having that gene affects the cell or the organism.  The disabled genes are known as ‘knockouts’.  Although knockouts have been used in genetics for decades, only a tiny subset of genes have been candidates for this type of study.  For one thing, creating knockouts requires extremely precise genetic manipulation.  For another, if the gene in question is essential to life, it’s impossible to grow single cells containing that knockout, let alone an entire organism.

William Skarnes of Cambridge and an international consortium got around these problems by creating a series of highly specific recombinant DNA molecules, or vectors. Each DNA vector is inserted into the intron of a specific gene.  Introns are normally removed from RNA in the process of making proteins, thus the vectors do not disrupt gene function unless they are activated.  This ensures that even knockouts of essential genes can be constructed.  Once a vector is activated and that gene product is eliminated, the results can be observed in that cell.  If the knockout is made in a germ-line cell (egg or sperm), the effect of the knockout in an entire organism can be studied.

Not only did the researchers come up with a method of knocking out any gene, but they also developed what they refer to as a ‘high-throughput gene-targeting pipeline’ for creating the vectors.  Thus far, they’ve made over 15,000 vectors, and knocked out over 9000 genes, out of the 20,000 or so in the mouse genome.