14 January 2013
A new technique could offer a more precise, flexible, reliable and cost-effective way to edit genomic DNA.
The technique makes use of a protective mechanism employed by bacteria – called the Cas system – that attacks and chops up invasive viral DNA. The method, reported in the journal Science, attaches bacterial Cas enzymes to custom-made RNA sequences that direct them to specific complementary sections of the genome where they are then activated to snip the DNA molecule and insert or delete a desired sequence.
Methods for editing DNA at specific locations have been around for several years - often based upon zinc finger nucleases - but these only work with certain sequences, and can often be very inefficient. Artificially created enzymes called TALENS have been developed to overcome these limitations, but this new method should be both less expensive and more precise, potentially enabling just a single nucleotide within the genome to be altered if necessary. The technique has very high specificity – a single letter difference between the attached RNA sequence and a genome location will prevent the Cas enzyme being activated.
The system can also be adapted to target multiple regions of the genome simultaneously. Lead author of the study Feng Zhang said “That's the beauty of this - you can easily program a nuclease to target one or more positions in the genome".
This suggests a wide range of potential applications for the technique, from engineering bacteria for use in industry to human gene therapy. It could also aid understanding of human disease. "Using this genome editing system, you can very systematically put in individual mutations and differentiate the stem cells into neurons or cardiomyocytes and see how the mutations alter the biology of the cells" said Zhang.