Correction to: Gene Therapy (2013) 20, 225–233; doi: 10.1038/gt.2012.89; published online 15 November 2012

Since the advance online publication of this article, the authors have noticed that an old version of Figures 1, 3, 4, 5, 6 and 7 was used. The correct figures, which include a 12-week bar, are included in the corrected article, which appears in this issue. The html and online PDF versions have also been amended.

The authors would like to apologise for this error.