Toehold-Based CRISPR-dCas9Transcriptional ActivationPlatform for Spatiotemporally Controllable Gene Therapy in Tumor andDiabetic Mouse Models

The CRISPR-Cas system has been extensively employed as a genome editing tool with the dCas9-based transcriptional activation system emerging as a particularly promising approach for gene editing in the treatment of diseases at the gene level. Nevertheless, the challenge of achieving effective spatiotemporal control of the transcriptional activation system of dCas9 has thus far restricted its broader application. In this study, we present an miRNA-responsive CRISPR-dCas9 transcriptional activation (mCTA) system. This system is capable of responding specifically to exogenous and endogenous miRNAs in mammalian cells and enables the specific imaging of miRNAs during neural development or in the deep tissues of mice. Furthermore, the replacement of downstream functional genes with DTA has been demonstrated to result in the effective apoptosis of tumor cells and inhibition of xenografted tumor growth in mice. Finally, in a diabetic mouse model, the m₁₂₂CTA system was shown to reduce the blood glucose in diabetic mice via the activation of PDX-1 gene. Our work provides an effective platform for miRNA imaging and gene therapy via spatiotemporal control of gene regulation.