Nat. Genet. 38, 752–754 (2006); published online 18 June 2006; corrected after print 17 July 2006

In the version of this article initially published, the authors neglected to acknowledge sample contributions. Samples were obtained from the “Cell line and DNA bank from patients affected by genetic diseases” collection at the Giannina Gaslini Institute (http://www.gaslini.org/labdppm.htm) supported by Italian Telethon grants (project #GTF04002). This error has been corrected in the PDF version of the article.