Abstract: The presently claimed invention offers programmable and precise regulation of Cas9 functions by utilizing a set of compact Cas9 derivatives created by deleting conserved HNH and/or REC-C domains based on the structural information across variant class 2 CRISPR effectors. In addition, a novel strategy for engineering the dimeric gRNA-guided nuclease by splitting the mini-dSaCas9 and fusing the FokI domain right after the split point is claimed to increase the on-target DNA cleavage efficiency and potentially reduce the off-target effect because of a closer proximity of dimeric Fold nuclease to the target sequence. By combining the optimized and compact gRNA expression cassette and the downsized SaCas9 derivatives, the entire CRISPR/Cas system with different effector domains for transactivation, DNA cleavage and base editing is loaded into a single AAV virus. Such an all-in-one AAV-CRISPR/Cas9 system will be particularly appealing in biomedical applications that require safe and efficient delivery in vivo.

Abstract: The presently claimed invention offers programmable and precise regulation of Cas9 functions by utilizing a set of compact Cas9 derivatives created by deleting conserved HNH and/or REC-C domains based on the structural information across variant class 2 CRISPR effectors. In addition, a novel strategy for engineering the dimeric gRNA-guided nuclease by splitting the mini-dSaCas9 and fusing the FokI domain right after the split point is claimed to increase the on-target DNA cleavage efficiency and potentially reduce the off-target effect because of a closer proximity of dimeric FokI nuclease to the target sequence. By combining the optimized and compact gRNA expression cassette and the downsized SaCas9 derivatives, the entire CRISPR/Cas system with different effector domains for transactivation, DNA cleavage and base editing is loaded into a single AAV virus. Such an all-in-one AAV-CRISPR/Cas9 system will be particularly appealing in biomedical applications that require safe and efficient delivery in vivo.

Abstract: While genetic engineering has undergone rapid advancement with the discovery of CRISPR/Cas9, there is room for improvement for genetic circuit control, precision (reducing circuit ‘leakiness’) and delivery into living systems. The claimed invention offers programmable and precise regulation of dCas9 functions in response to multiple molecular signals by using synthetic gene circuits, greatly expanding applications. Moreover, using the system to greatest therapeutic potential has been greatly limited by the restrictive cargo size of existing viral delivery systems. By splitting dCas9 into multiple sections, the delivery size of synthetic gene circuits is greatly reduced. By exchanging split dCas9 domains, differential regulation on one gene, or activating two different genes in response to cell-type specific microRNAs is illustrated.