Nat. Genet. 42, 72–76 (2010); published online 20 December 2009; corrected after print 5 February 2010.

In the version of this article initially published, Stephen J. Tonna was inadvertently omitted from the author list, and the fourth author (Hiroyasu Tsukaguchi) was missing one of his affiliations. These errors have been corrected in the HTML and PDF versions of the article.