GENE therapy should become a more exact science thanks to the discovery that it is possible to predict where a transferred gene is likely to be inserted into the recipient’s DNA.

Where a beneficial gene ends up has been a mystery till now. As a result, a large number of a person’s cells need to be infected with the retrovirus that is used to transfer the genetic material, to increase the chance of the gene ending up in the right place. This also increases the risk of side effects such as cancer.

To better understand the process, Jeremy Luban and his colleagues at University of Geneva in Switzerland combed previous gene therapy trials looking for a pattern between the gene-insertion sites and features in DNA. For three retroviruses out of 12, they found a group of proteins in recipient DNA whose presence predicted the site of insertion with a 75 per cent success rate (PLoS Computational Biology, DOI: 10.1371/journal.pcbi.1001008).

Peter Cherepanov at Imperial College London, who was not part of the team, says now that the probability of an undesirable insertion can be estimated, it will become easier to balance the chance of success with the risk of side effects.