these sites was related to Cas9 activity. In addition, we detected clear off-target activity at a site (site A, Fig. 4b) with a 1 bp gRNA mismatch but a variant PAM sequence, CAG, with known partial activity19. Together these results suggest that Cas9 does not induce widespread genomic instability or rearrangements, but does induce off-target mutagenesis at rare sites that cannot be fully anticipated by current prediction rules.
