Author:
Hwang Gue-ho,Lee Seok-Hoon,Oh Minsik,Kim Segi,Habib Omer,Jang Hyeon-Ki,Kim Heon Seok,Kim Chan Hyuk,Kim Sun,Bae Sangsu
Abstract
AbstractCRISPR-Cas9 nucleases are versatile tools for genetic engineering cells and function by producing targeted double-strand breaks (DSBs) in the DNA sequence. However, the unintended production of large deletions (>100 bp) represents a challenge to the effective application of this genome-editing system. We optimized a long-range amplicon sequencing system and developed a k-mer sequence-alignment algorithm to simultaneously detect small DNA alteration events and large DNA deletions. With this workflow, we determined that CRISPR-Cas9 induced large deletions at varying frequencies in cancer cell lines, stem cells, and primary T cells. With CRISPR interference screening, we determined that end resection and the subsequent TMEJ [DNA polymerase theta-mediated end joining] repair process produce most large deletions. Furthermore, base editors and prime editors also generated large deletions despite employing mutated Cas9 “nickases” that produce single-strand breaks. Our findings reveal an important limitation of current genome-editing tools and identify strategies for mitigating unwanted large deletion events.
Publisher
Cold Spring Harbor Laboratory