MiR-ON-CRISPR: a microRNA-activated CRISPR–dCas9 system for precise gene therapy in living cells and mouse models of sepsis

The CRISPR–dCas9 technology is a powerful tool for manipulating the expression of target genes in a variety of biomedical applications. Nevertheless, it is imperative that the activity of the CRISPR–dCas9 system be tightly controlled to improve its safety and applicability. In this study, we successfully designed a microRNA-activated CRISPR–dCas9 system, termed miR-ON-CRISPR, in which the core components (dCas9 and sgRNA) are both regulated by endogenous miRNA. Our findings demonstrated that the miR-ON-CRISPR system can regulate firefly luciferase reporter gene expression to faithfully visualize miRNA activity and image the differentiation status of neural cells. Moreover, the miR-ON-CRISPR was designed as an AND/OR gate system, thereby enabling the simultaneous detection of two distinct miRNAs. Furthermore, the system was adapted to achieve cell type-specific killing by activating the exogenous DTA genes or endogenous BAX genes. Finally, in mouse models of sepsis, the miR-ON-CRISPR system was shown to alleviate the sepsis-induced liver injury as well as the associated oxidative stress damage and endoplasmic reticulum stress via activating the nuclear erythroid 2-related factor 2 gene. In conclusion, this proof-of-concept study demonstrates the feasibility of the miR-ON-CRISPR system for cell type-specific control of CRISPR–dCas9 activity and its therapeutic applications in the treatment of genetic diseases.