Nat. Med. 21, 989–997 (2015); published online 03 August 2015; corrected after print 4 September 2015

In the version of this article initially published, the word 'genetically' was added by the editor to the penultimate sentence of the abstract during proofing of the manuscript. However, the authors used not only a genetic knockout approach but also morpholino-induced inhibition of proper mRNA processing to target Snail1 expression. Thus, the word 'genetically' has been deleted from the sentence to better convey the findings of the report. The error has been corrected in the HTML and PDF versions of the article.