Nat. Genet. 41, 334–341 (2009); published online 8 February 2009; corrected after print 27 May 2009

In the version of this article initially published, the names of four co-authors (Christopher W Knouff, Dawn M Waterworth, Max C Walker, Vincent Mooser) were omitted from the author list. The error has been corrected in the HTML and PDF versions of the article.