Nature Communications 6 Article number: 7481 (2015); Published 26 June 2015; Updated 5 February 2016

The financial support for the work described in this Article was not fully acknowledged. The Acknowledgements should have included the following: This work was supported in part by a grant to H.J.G., B.H. and N.T. (European Union’s Seventh Framework Program (FP/2007/2013)/European Research Council (ERC) Grant Agreement 322820).