Nat. Biotechnol. 25, 1468–1475 (2007); published online 25 November 2007; corrected after print 8 July 2008

In the version of this article initially published, a reference was missing from the first paragraph. A new sentence and the reference (no. 6) have been added: “A recent study characterized neural crest differentiation from cloned bovine blastocysts via a neural rosette intermediate6. Other....” Subsequent references have been renumbered. The corrections have been made in the HTML and PDF versions of the article.