A new gene therapy technique that seems to exploit own genetics of a cell repair mechanism to rewrite its DNA sequence showed remarkable success in rats. The results, in this month of Nature Medicine , could have a major impact on efforts to cure hemophilia and other incurable genetic diseases.
For over a decade researchers have been trying to find a way to efficiently insert the DNA into the punishment cells. Clifford Steer and his team at the University of Minnesota Medical School in Minneapolis used a technique that mouthwatering results showed previously: so-called chimeric molecules, loops that contain both DNA and of RNA. Genes are made of DNA and cells use RNA - a molecule closely related - to translate the genes into proteins. A chimeric molecule is designed to match the target gene nucleotide for nucleotide bases except to researchers want to change -. In hemophilia, for example, single nucleotide must correct
Although no one really knows how to rewrite chimeric DNA sequences, the researchers suspected that when the chimera binds to the region of corresponding DNA in a cell, the cell's DNA repair mechanism detects the mismatch and - as an overlay key on a typewriter - removes the mutant base in its own DNA and the correct inserts. The RNA in the chimeric resistant enzymes that break down the foreign DNA into the cell and allows the binding molecule to the target gene closely
Although previous efforts to use chimeras were only carried out with cells in culture -. With mixed success with -the new study is the first to test the animals approach. Steer and colleagues injected their molecule, covered with a polymer which has the chimera into the liver cells in the tail veins of rats. In this case, the chimeras were designed not to cure a disease but to induce mutation that causes hemophilia in persons, which occurs when the liver cells can not make a protein essential for blood clotting. Indeed, the blood of treated rats did not coagulate as easily as those that were injected with saline. When researchers inspected the livers of the animals, they found that 40% of the cells were induced mutation. Changing the same DNA in 5% of liver cells would be enough to heal a haemophiliac patient, Steer said. The next step, he said, will be to try the technique in reverse, this time to cure the mutation hemophilia in dogs.
One expert called the experiment a success "incredible". Michael Strauss gene therapy researcher of the Humboldt University in Berlin warns that liver cells may be particularly amenable treatment. However, "if the technique can be reproduced by others in other cell systems and other target genes," he said, "we would have a method that could theoretically provide a cure for genetic diseases."
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