ÐÓ°ÉÔ­´´

A ROVING snippet of DNA has been used to make reprogrammed stem cells that are stripped of potentially cancer-causing genes.

The first reprogrammed stem cells – known as induced pluripotent stem cells – were made by Shinya Yamanaka of Kyoto University in Japan. He used viruses to insert four genes into the chromosomes of adult skin cells, reprogramming them into an embryonic state. These iPS cells could turn into any of the body’s tissues, but cells derived from them were not transplantable into people because viruses can add extra copies of cancer-causing genes to the chromosome.

Now two teams, led by of the University of Edinburgh, UK, and of the Samuel Lunenfeld Research Institute in Toronto, Canada, have used a piece of DNA called a transposon to deliver the four genes. Unlike viruses, the transposon can often be made to leap out of the genome once it has done its job rather than reinserting, posing less of a cancer risk.

The teams engineered the transposon piggyBac to contain Yamanaka’s four genes, then added it to mouse and human skin cells. It reprogrammed a small portion of these cells. Then they reactivated the transposon to make it leap out of the chromosomes, and selected for those cells in which it failed to jump back in again (Nature, and ).

Previously, iPS cells have been made using viruses that don’t insert themselves into the genome, but the engineered piggyBac was more efficient.