Nat. Genet. 47, 416–422 (2015); published online 2 March 2015; corrected after print 5 May 2015

In the version of this article initially published, the following two sentences were omitted from the Acknowledgments: “Sequencing was carried out at the Millard and Muriel Jacobs Genome Facility at the California Institute of Technology. This work was supported by US National Institutes of Health grants to P.W.S. (GM084389) and to R.V.A. (AI056189), by Cornell University salary and start-up funds to E.M.S. and by the Howard Hughes Medical Institute to P.W.S.” The error has been corrected in the HTML and PDF versions of the article.