Nat. Biotechnol. 28, 935–942 (2010); published online 09 September 2010; corrected after print 7 December 2010

In the version of this article initially published, the affiliation for Ken Fukuda was incorrect. The correct affiliation is Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan. The error has been corrected in the HTML and PDF versions of the article.