Nat. Genet. 41, 228–233 (2009), published online 4 January 2009; corrected after print 28 April 2009

The affiliation of the 24th author, Alessandro Terrinoni, was listed incorrectly. It should read IDI-IRCCS Biochemistry Laboratory c/o Univ. Tor Vergata, 00133 Rome, Italy. The error has been corrected in the HTML and PDF versions of this article.