Nat. Med. 19, 739–746 (2013); published online 28 April 2013; corrected online 14 May 2013 (details online); corrected after print 25 August 2014

In the version of this article initially published, the accession code was not listed. The data are deposited in the Gene Expression Omnibus with the accession code GSE53514. The error has been corrected in the HTML and PDF versions of this article.