Researchers have induced pluripotency in human cells for the first time without using viral methods to deliver the reprogramming factors. The work, described online in Nature, demonstrates stable induced pluripotent stem (iPS) cells in both human and mouse fibroblasts using a DNA sequence that can move around the cell known as piggyBac, and combining this approach with a single vector to deliver all the factors into one site on the chromosome, and then excise it.
iPS cells have great potential in applications from regenerative medicine to toxicological testing and drug screening, but most current methods involve viral gene delivery that could cause abnormalities in the induced cells. Keisuke Kaji and colleagues demonstrate in mice that it is possible to use a single vector, containing the coding sequences of the four viral factors commonly used in inducing pluripotency, and synthesise four independent reprogramming factor proteins from that. They then show that the four genes can be removed using sequences surrounding the cassette in combination with an excision protein that cuts the intervening DNA out and rejoins the ends. Kaji and the team go on to generate iPS cells by combining their single-vector cassette with the piggyBac transposon.
Andras Nagy and colleagues take the piggyBac work a step further by combining it with the single-vector method to generate stable iPS cells from both human and mouse embryonic fibroblasts before the vector is removed from the chromosome in one piece. This team also shows that the piggyBac method can be used to generate lines in which different combinations of the reprogramming factors are removed individually, making lines that are potentially useful for drug screens and research.
Keisuke Kaji (The University of Edinburgh, UK)
Andras Nagy (Mount Sinai Hospital, Toronto, Canada)
Abstracts available online:
Abstract of Paper 1.
Abstract of Paper 2.
(C) Nature press release.
Message posted by: Trevor M. D'Souza