Nat. Biotechnol. 10.1038/nbt.4192; corrected online 31 July 2018

In the version of this article initially published online, four figure citations were incorrect on p.2: left-hand column, after “complex rearrangements,” “Supplementary Fig. 2a,b” should have been “Fig. 2a,b”; right-hand column, in three places, the citation for “Supplementary Fig. 3...” should have been for “Supplementary Fig. 2.” The errors have been corrected for the print, PDF and HTML versions of this article.