From iPSC-Cas9-PB cells, genome editing is highly efficient. As shown in Fig. 2 and Suppl. Fig. 1, we routinely obtain clones in which 19% have undergone HDR and 54% have undergone NHEJ. The surveyor nuclease assay is a useful predictor of efficient genome modification: if a robust nuclease cleavage product is observed, then analysis of 48–96 clones will likely yield the desired genome edited product. On the other hand, weak or absent nuclease cleavage product (Fig. 6) suggests that the experiment should be halted and steps should be taken to troubleshoot the genome editing efficiency (see Supplementary Table 1).
