Nat. Biotechnol. 30, 55–56 (2012); published online 9 January 2012; corrected after print 7 June 2012

In the version of this article initially published, the volume number and year of reference 2 should have been 30 and 2012, and not 29 and 2011, respectively. The errors have been corrected in the HTML and PDF versions of the article.