Targeting Specificity of the CRISPR/Cas9 System

CRISPR/Cas9 system has accelerated research across many fields since its demonstration for genome editing. CRISPR also offers vast therapeutic potential, but an important hurdle of this technology is the off-target mutations it can induce. In this viewpoint, we will discuss recent strategies for improving CRISPR specificity, emphasizing how a complete mechanistic understanding of CRISPR/Cas9 can benefit such efforts. We also propose that agreeing upon a consensus protocol with the highest specificity could benefit researchers working on CRISPR-based therapies. In addition to improving CRISPR/Cas9 specificity, accurate detection of off-target events is also crucial, and we will discuss various unbiased off-target detection methods in terms of their advantages and disadvantages. We suggest that using a combination of cell-based and cell-free methods can prove more useful. In addition, we point out that improving predictive algorithms for off-target sites would require pooling of the available off-target analysis data and standardization of the protocols used for obtaining the data. Moreover, we highlight the risk of insertional mutagenesis for gene correction applications requiring the use of donor DNA. We conclude by discussing future prospects for the field, as well as steps that can be taken to overcome the aforementioned challenges.