Nat. Genet.; doi:10.1038/ng.3591; corrected online 18 July 2016

In the version of this article initially published online, the following callouts to supplementary items or main figure panels were incorrect: in the legend to Figure 1, the callout to Supplementary Figure 4 should have referred to Supplementary Figure 2; on page 4 of the PDF, the callout to Figure 4a should have also called out Figure 4b; on page 6 of the PDF, the callout to Supplementary Table 4 should have referred to Supplementary Table 5 and the callout to Supplementary Figure 9b should have referred to Supplementary Figure 10b; and on page 9 of the PDF, the callout to Supplementary Table 2 should have referred to Supplementary Data. The errors have been corrected for the print, PDF and HTML versions of this article.