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10/31/2017

    New advance in DNA base editing tools




    Described in a study published in Nature, scientists have further developed the genome editing technique known as 'base editing' to turn adenine-thymine base pairs back to guanine-cytosine. They hope the approach could one day be used to treat diseases associated with single genetic mutations.


    'We are currently using base editing to try to study or validate potential future therapeutic treatments for blood diseases, genetic deafness, genetic blindness … and some neurological disorders as well,' said author Professor David Liu of Harvard University.


    Unlike the more common CRISPR/ Cas9 technology, base editing does not cleave DNA to make edits, reducing the substantial number of errors at target sites such as random insertions or deletions. Yet until now, this technique - developed last year by the same team - only allowed the conversion of guanine-cytosine (G-C) into adenine-thymine (A-T). This class of mutation, changing a G-C to an A-T, accounts for about half of the 32,000 known pathogenic point mutations in humans.


    The new approach uses an enzyme that changes adenine into a molecule called inosine. Another enzyme, Cas9, then places a 'nick' in the strand across from the inosine, which stimulates the cell's machinery to begin a repair. That nick prompts the cell to replace the T with a C, because the base opposite the T has been converted to inosine, which pairs with C. The process worked in both bacteria and human cells.


    Dr Helen O'Neill from University College London, who was not involved in the research, said: 'The ability to now directly alter all four base-pairs with such specificity adds more ammunition to the genome editing artillery and will be incredibly powerful in the research of diseases and future restoration of disease-causing mutations.'


    Read More: "Programmable base editing of A•T to G•C in genomic DNA without DNA cleavage", Nature (2017) doi:10.1038/nature24644