Engineered CRISPR RNA improves the RNA cleavage efficiency of hfCas13X.

As the most compact variant in the Cas13 family, CRISPR-Cas13X holds considerable promise for gene therapy applications. The development of high-fidelity Cas13X (hfCas13X) mutants has enhanced the safety profile for in vivo applications. However, a notable reduction in on-target cleavage efficiency accompanies the diminished collateral cleavage activity in hfCas13X. In this study, we obtained two engineered crRNA mutants that notably enhance the on-target cleavage efficiency of hfCas13X. Furthermore, we have identified a novel crRNA structure that consistently augments the on-target cleavage efficiency of hfCas13X across various cellular environments, without significant enhancement of its collateral activity. These findings collectively enrich the gene-editing toolkit, presenting a more effective hfCas13X system for future research and application.