Correction to: Nature Protocols https://doi.org/10.1038/nprot.2015.088, published online 3 September 2015

The version of this paper originally published shows incorrect units for two plasmid concentrations. In the “Reagent Setup” section, the instructions for sgRNA-Cas9 plasmid should read “Adjust the concentration of each plasmid to 1 μg μl–1,” rather than “to 1 μg ml–1.” Similarly, all concentrations in the tables in Steps 49A, 49C, and 49D should be in μg μl–1 instead of μg ml–1. Please note that these units have not been corrected in the PDF or HTML versions of the protocol available online.