Nat. Genet. 43, 246–252 (2011); published online 6 February 2011; corrected after print 11 August 2011

In the version of this article initially published, an affiliation was missing for two authors, Maria Gazouli and Nicholas P. Anagnou. They are also affiliated with the Foundation for Biomedical Research of the Academy of Athens in Athens, Greece. The error has been corrected in the HTML and PDF versions of the article.