A Cas12a ortholog with stringent PAM recognition followed by low off-target editing rates for genome editing

Our study shows that CeCas12a nuclease is active in human cells and the stringency of PAM recognition could be an important factor shaping off-target editing in gene editing. Thus, CeCas12a provides a promising candidate with distinctive characteristics for research and therapeutic applications we identify a novel Cas12a nuclease CeCas12a from Coprococcus eutactus, which is a programmable nuclease with genome editing efficiencies comparable to AsCas12a and LbCas12a in human cells. Moreover, CeCas12a is revealed to be more stringent for PAM recognition in vitro and in vivo followed by very low off-target editing rates in cells. Notably, CeCas12a renders less off-target edits located at C-containing PAM at multiple sites compared to LbCas12a and AsCas12a, as assessed by targeted sequencing methods