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- Title
Long-read sequence analysis of MMEJ-mediated CRISPR genome editing reveals complex on-target vector insertions that may escape standard PCR-based quality control.
- Authors
Higashitani, Yuki; Horie, Kyoji
- Abstract
CRISPR genome editing is a powerful tool for elucidating biological functions. To modify the genome as intended, it is essential to understand the various modes of recombination that can occur. In this study, we report complex vector insertions that were identified during the generation of conditional alleles by CRISPR editing using microhomology-mediated end joining (MMEJ). The targeting vector contained two loxP sequences and flanking 40-bp microhomologies. The genomic regions corresponding to the loxP sequences were cleaved with Cas9 in mouse embryonic stem cells. PCR screening for targeted recombination revealed a high frequency of bands of a larger size than expected. Nanopore sequencing of these bands revealed complex vector insertions mediated not only by MMEJ but also by non-homologous end joining and homologous recombination in at least 17% of the clones. A new band appeared upon improving the PCR conditions, suggesting the presence of unintentionally modified alleles that escape standard PCR screening. This prompted us to characterize the recombination of each allele of the genome-edited clones using heterozygous single nucleotide polymorphisms, leading to confirmation of the presence of homozygous alleles. Our study indicates that careful quality control of genome-edited clones is needed to exclude complex, unintended, on-target vector insertion.
- Subjects
QUALITY control standards; GENOME editing; BIVECTORS; SEQUENCE analysis; CRISPRS; SINGLE nucleotide polymorphisms
- Publication
Scientific Reports, 2023, Vol 13, Issue 1, p1
- ISSN
2045-2322
- Publication type
Article
- DOI
10.1038/s41598-023-38397-y