With a discovery published online in Nature that could herald an alternative to gene therapy, Michael Holmes and his colleagues demonstrate a new way to correct disease-causing mutations in human DNA.
Researchers have struggled to perfect gene therapy, in which they try to compensate for defective genes by inserting a new working copy into cells. Gene correction takes a different approach: repairing the mistakes in DNA that cripple the gene.
Holmes' team fused a zinc-finger protein, which recognizes three to four base pairs in DNA, to a nuclease, which cuts DNA at that sequence. These 'zinc-finger nucleases' are known to trigger homologous recombination, a process by which the surrounding segment of DNA is replaced by a fresh copy.
The team designed a zinc-finger nuclease that recognizes the mutation underlying X-linked severe combined immune deficiency (SCID) - children with this condition can suffer life-threatening infections soon after birth. Holmes and co-workers showed that the nuclease prompted correction of the defect in a high frequency of T cells - the cells affected by the disorder. The study offers the prospect that zinc-finger nucleases could be engineered against any disease-causing mutation in the human genome, and used to treat the disease.
Michael Holmes (Sangamo, BioSciences, Richmond, CA, USA)
(C) Nature press release.
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