Hermantara R, Richmond L, Taqi AF, Chilaka S, Jeantet V, Guerrini I, West K, West A. Improving CRISPR-Cas9 directed faithful transgene integration outcomes by reducing unwanted random DNA integration.
J Biomed Sci 2024;
31:32. [PMID:
38532479 DOI:
10.1186/s12929-024-01020-x]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Accepted: 03/09/2024] [Indexed: 03/28/2024] Open
Abstract
BACKGROUND
The field of genome editing has been revolutionized by the development of an easily programmable editing tool, the CRISPR-Cas9. Despite its promise, off-target activity of Cas9 posed a great disadvantage for genome editing purposes by causing DNA double strand breaks at off-target locations and causing unwanted editing outcomes. Furthermore, for gene integration applications, which introduce transgene sequences, integration of transgenes to off-target sites could be harmful, hard to detect, and reduce faithful genome editing efficiency.
METHOD
Here we report the development of a multicolour fluorescence assay for studying CRISPR-Cas9-directed gene integration at an endogenous locus in human cell lines. We examine genetic integration of reporter genes in transiently transfected cells as well as puromycin-selected stable cell lines to determine the fidelity of multiple CRISPR-Cas9 strategies.
RESULT
We found that there is a high occurrence of unwanted DNA integration which tarnished faithful knock-in efficiency. Integration outcomes are influenced by the type of DNA DSBs, donor design, the use of enhanced specificity Cas9 variants, with S-phase regulated Cas9 activity. Moreover, restricting Cas9 expression with a self-cleaving system greatly improves knock-in outcomes by substantially reducing the percentage of cells with unwanted DNA integration.
CONCLUSION
Our results highlight the need for a more stringent assessment of CRISPR-Cas9-mediated knock-in outcomes, and the importance of careful strategy design to maximise efficient and faithful transgene integration.
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