Project description:We report transcriptome wide edits comparison between split-engineered base editors and intact base editors. Our results show that, split-engineered base editors show backgound levels of unique C>U edits when compared to intact base editors.
Project description:RNA-programmable deaminases, known as base editors (BEs), enable precise single base conversions on genomic DNA and hold great promise for therapeutic application in patients. Recent studies, however, have raised serious concern with regard to off-target effects, questioning translatability of BEs to the clinic. Here we analyze transcriptome- and genome-wide off-target effects following AAV-mediated delivery of cytosine base editors (CBEs) in vivo in an unbiased manner. We show that low expression of CBEs allows sufficient on-target editing to cure a disease phenotype with no increase in off-target effects compared to untreated controls. To further improve safety of in vivo base editing, we developed a lipid nanoparticle (LNP)-mediated delivery system to transiently express BEs. We reach up to 21% on-target editing with no detectable transcriptome- or genome-wide off-target effects, and are able to reverse the disease phenotype of a phenylketonuria mouse model. These results have important implications, underlining the feasibility of transient in vivo base editing for therapeutic use in patients.
Project description:CRISPR-Cas9 delivery by AAV holds promise for gene therapy but faces critical barriers due to its potential immunogenicity and limited payload capacity. Here, we demonstrate genome engineering in postnatal mice using AAV-split-Cas9, a multi-functional platform customizable for genome-editing, transcriptional regulation, and other previously impracticable AAV-CRISPR-Cas9 applications. We identify crucial parameters that impact efficacy and clinical translation of our platform, including viral biodistribution, editing efficiencies in various organs, antigenicity, immunological reactions, and physiological outcomes. These results reveal that AAV-CRISPR-Cas9 evokes host responses with distinct cellular and molecular signatures, but unlike alternative delivery methods, does not induce detectable cellular damage in vivo. Our study provides a foundation for developing effective genome therapeutics mRNA-Seq from muscles (9 samples; 3 mice x 3 conditions) and lymph nodes (9 samples; 3 mice x 3 conditions).
Project description:CRISPR-Cas9 delivery by AAV holds promise for gene therapy but faces critical barriers due to its potential immunogenicity and limited payload capacity. Here, we demonstrate genome engineering in postnatal mice using AAV-split-Cas9, a multi-functional platform customizable for genome-editing, transcriptional regulation, and other previously impracticable AAV-CRISPR-Cas9 applications. We identify crucial parameters that impact efficacy and clinical translation of our platform, including viral biodistribution, editing efficiencies in various organs, antigenicity, immunological reactions, and physiological outcomes. These results reveal that AAV-CRISPR-Cas9 evokes host responses with distinct cellular and molecular signatures, but unlike alternative delivery methods, does not induce detectable cellular damage in vivo. Our study provides a foundation for developing effective genome therapeutics
Project description:Conjugation of CRISPR-Cas9 with cytidine deaminases leads to base editors (BEs) for programmable C-to-T editing, which holds potentials in clinical applications, but suffers from off-target (OT) mutations. By taking advantage of a cleavable deoxycytidine deaminase inhibitor (dCDI) domain, a transformer BE (tBE) system is developed to induce efficient editing with only background levels of genome-wide and transcriptome-wide OT mutations. After being produced, tBE remains inactive at OT sites with the fusion of a cleavable dCDI, thus eliminating unintended mutations. Only when binding at on-target sites, tBE is transformed to cleave off the dCDI domain and catalyzes targeted deamination for precise base changes. After delivery into mice via a dual-AAV system, tBE created a premature stop codon in Pcsk9 and significantly reduced serum PCSK9 level, which resulted in ~30-40% decrease of total cholesterol. Together, the development of tBE establishes a highly-precise base editing system and its in vivo efficacy envisions potential therapeutic applications.
Project description:Conjugation of CRISPR-Cas9 with cytidine deaminases leads to base editors (BEs) for programmable C-to-T editing, which holds potentials in clinical applications, but suffers from off-target (OT) mutations. By taking advantage of a cleavable deoxycytidine deaminase inhibitor (dCDI) domain, a transformer BE (tBE) system is developed to induce efficient editing with only background levels of genome-wide and transcriptome-wide OT mutations. After being produced, tBE remains inactive at OT sites with the fusion of a cleavable dCDI, thus eliminating unintended mutations. Only when binding at on-target sites, tBE is transformed to cleave off the dCDI domain and catalyzes targeted deamination for precise base changes. After delivery into mice via a dual-AAV system, tBE created a premature stop codon in Pcsk9 and significantly reduced serum PCSK9 level, which resulted in ~30-40% decrease of total cholesterol. Together, the development of tBE establishes a highly-precise base editing system and its in vivo efficacy envisions potential therapeutic applications.
Project description:Large genes including several CRISPR-Cas modules, such as gene activators (CRISPRa), require dual adeno-associated viral (AAV) vectors for efficient in vivo delivery and expression. Current dual AAV vector approaches have important limitations, e.g., low reconstitution efficiency, production of alien proteins, or low flexibility in split site selection. Here, we present a dual AAV vector technology based on reconstitution via mRNA trans-splicing (REVeRT). REVeRT is flexible in split site selection and can efficiently reconstitute different split genes in numerous in vitro models, in human organoids and in vivo. Furthermore, REVeRT can functionally reconstitute a CRISPRa module targeting genes in various mouse tissues and organs in single or multiplexed approaches upon different routes of administration. Finally, supplementation of ABCA4 (6.8 kb) via REVeRT improves retinal degeneration and function in a mouse model of inherited blindness. Due to its flexibility and efficiency REVeRT harbors great potential for basic research and clinical applications.
Project description:Large genes including several CRISPR-Cas modules, such as gene activators (CRISPRa), require dual adeno-associated viral (AAV) vectors for efficient in vivo delivery and expression. Current dual AAV vector approaches have important limitations, e.g., low reconstitution efficiency, production of alien proteins, or low flexibility in split site selection. Here, we present a dual AAV vector technology based on reconstitution via mRNA trans-splicing (REVeRT). REVeRT is flexible in split site selection and can efficiently reconstitute different split genes in numerous in vitro models, in human organoids and in vivo. Furthermore, REVeRT can functionally reconstitute a CRISPRa module targeting genes in various mouse tissues and organs in single or multiplexed approaches upon different routes of administration. Finally, supplementation of ABCA4 (6.8 kb) via REVeRT improves retinal degeneration and function in a mouse model of inherited blindness. Due to its flexibility and efficiency REVeRT harbors great potential for basic research and clinical applications.