Correction to: Nature Biotechnology https://doi.org/10.1038/s41587-019-0266-0, published online 7 October 2019.

In the version of this article initially published online, the color of the red and black squares was reversed in Fig. 4d and the labels RCI001 and RCI002 were reversed in Supplementary Tables 1 and 3. The errors have been corrected in the print, PDF and HTML versions of the article.