Synergistic integration of inducible RNA switches enhances the manipulation of vector expression

Precise manipulation of gene expression is pivotal for gene function studies and the optimization of gene therapy. RNA-based gene switches are attractive tools due to their robust tunability by FDA-approved small molecules, the absence of exogenous immunogenic proteins, and the small size for gene delivery vectors such as adeno-associated virus (AAV). However, existing RNA switches only target a single step of gene expression such as transcription or RNA splicing, exhibiting intrinsic limitations in gene regulation. To overcome this issue, this study integrated the aptamer-based polyA regulator (pA), the drug-elicitable alternative splicing module (DreAM) and an engineered translation modulator with conditional upstream open reading frames (uORFs) to construct the DreAM-plus RNA switch. The pA-DreAM concatenation led to 1.5[~]5.0-fold and 1.2[~]4.4-fold increase of inducible fold changes than pA and DreAM, respectively. The uORF module further enhanced the switching performance by 1.4[~]6.3-fold. DreAM-plus-mediated transient transgene expression demonstrated a temporal resolution of about 24 hours and high tissue specificity to liver or heart. Critically, DreAM-plus achieved transient expression of an array of gene editors (SpCas9, SaCas9, Un1Cas12f1, OsCas12f1, AcCas12n, IsDra2 TnpB etc.) that significantly mitigated off-target effects by 1.4[~]2.8 folds in plasmids, lentivirus and AAV. In a new mouse model with lipid-nanoparticle-delivered pre-existing immunity, DreAM-plus attenuated AAV-delivered Cas-specific CD8 T cell immune toxicity in the liver and the heart. Therefore, multiple RNA switches could be synergistically integrated to build more sophisticated genetic cassettes for enhanced manipulation of gene expression.