Nature Communications 5: Article number: 5214 (2014); Published 31 October 2014; Updated 26 February 2015.

The original version of this Article contained a typographical error in the spelling of the authors Futoshi Nakagami and Ekaterina Chernogubova, which were incorrectly given as Futoshi Nagakami and Ekaterina Chernugobova. This has now been corrected in both the PDF and the HTML versions of the Article.