…and this little piggy corrected genetic mutations

Scientists have come a step closer to being able to correct mistakes in our DNA, thanks to a new method for rewriting mutations in stem cells. This could be used to treat genetic diseases for which there are no treatments available.

The researchers made use of piggyBac, a ‘jumping gene‘ originally found in moths. These ‘jumping genes’, as their name suggests, move from place to place along the DNA and can be used to carry other genes with them. Acting as a genetic cut-and-paste, they can neatly insert a corrected gene with remarkable precision. “Our systems leave behind no trace of the genetic manipulation, save for the gene correction,” says Professor Allan Bradley of the Wellcome Trust Sanger Institute.

In the case described in Nature the team focused on a genetic liver disease.

Severe deficiency in the protein alpha 1-antitrypsin is caused by a mutation, which is found in 1 in 2000 North Europeans. This protein is produced in the liver, but is responsible for protecting the lungs. The mutation causes the protein to accumulate in the liver, leading to cirrhosis, and deplete in the lungs, causing emphysema.

The scientists converted samples of patients’ skin cells into stem cells and corrected the mutation, using piggyBac. These stem cells were then converted into liver cells, in test tubes and in mice, which were able to produce the correct form of the protein.

Despite advances in the technology, producing stem cells in this fashion introduces new mutations into the DNA. While most of these mutations are likely to be harmless, there can be potentially fatal side-effects. This risk will need to be minimized before the technique is brought forward to treating patients.

Currently the only cure for alpha 1-antitrypsin deficiency is a liver transplant, but with transplant waiting lists longer than ever, this new development can bring hope to thousands of sufferers.