Project description:A-T to G-C base editing efficiency at targeted gene sites in HEK293T cells using the dCas12f-ABE design or the Cas12f-ABE design. Found that the total A-T to G-C conversion efficiency of Circular gRNAs exhibited about two-fold increase compared with U6 gRNAs. We further analyzed the pattern for A-T to G-C conversion on the target site, and observed that the most efficient base editing occurred in a narrow window A3 (3bp downstream of the PAM) similar to U6 gRNAs. In summary, Circular gRNAs with dCas12f-ABE design could enhance A-T to G-C base editing efficiency in a narrow window.
Project description:Genome editing technologies have enabled the clinical development of allogeneic cellular therapies, yet the optimal gene editing modality for multiplex editing of therapeutic T cell product manufacturing remains elusive. In this study, we conducted a comprehensive comparison of CRISPR/Cas9 nuclease and adenine base editor (ABE) technologies in generating allogeneic chimeric antigen receptor (CAR) T cells, utilizing extensive in vitro and in vivo analyses. Both methods achieved high editing efficiencies across four target genes, critical for mitigating graft-versus-host disease and allograft rejection: TRAC or CD3E, B2M, CIITA, and PVR. Notably, ABE demonstrated higher manufacturing yields and distinct off-target profiles compared to Cas9, with translocations observed exclusively in Cas9-edited products. Functionally, ABE-edited CAR T cells exhibited superior in vitro effector functions under continuous antigen stimulation, including enhanced proliferative capacity and increased surface CAR expression. Transcriptomic analysis revealed that ABE editing resulted in reduced activation of p53 and DNA damage response pathways at baseline, along with sustained activation of metabolic pathways during antigen stress. Consistently, ATAC-seq data indicated that Cas9-edited, but not ABE-edited, CAR T cells showed enrichment of chromatin accessibility peaks associated with double-strand break repair and DNA damage response pathways. In a preclinical leukemia model, ABE-edited CAR T cells demonstrated improved tumor control and extended overall survival compared to their Cas9-edited counterparts. Collectively, these findings position ABE as a superior choice of Cas9 nucleases for multiplex gene editing in therapeutic T cells.
Project description:Genome editing technologies have enabled the clinical development of allogeneic cellular therapies, yet the optimal gene editing modality for multiplex editing of therapeutic T cell product manufacturing remains elusive. In this study, we conducted a comprehensive comparison of CRISPR/Cas9 nuclease and adenine base editor (ABE) technologies in generating allogeneic chimeric antigen receptor (CAR) T cells, utilizing extensive in vitro and in vivo analyses. Both methods achieved high editing efficiencies across four target genes, critical for mitigating graft-versus-host disease and allograft rejection: TRAC or CD3E, B2M, CIITA, and PVR. Notably, ABE demonstrated higher manufacturing yields and distinct off-target profiles compared to Cas9, with translocations observed exclusively in Cas9-edited products. Functionally, ABE-edited CAR T cells exhibited superior in vitro effector functions under continuous antigen stimulation, including enhanced proliferative capacity and increased surface CAR expression. Transcriptomic analysis revealed that ABE editing resulted in reduced activation of p53 and DNA damage response pathways at baseline, along with sustained activation of metabolic pathways during antigen stress. Consistently, ATAC-seq data indicated that Cas9-edited, but not ABE-edited, CAR T cells showed enrichment of chromatin accessibility peaks associated with double-strand break repair and DNA damage response pathways. In a preclinical leukemia model, ABE-edited CAR T cells demonstrated improved tumor control and extended overall survival compared to their Cas9-edited counterparts. Collectively, these findings position ABE as a superior choice of Cas9 nucleases for multiplex gene editing in therapeutic T cells.
Project description:The most common form of genetic heart disease is hypertrophic cardiomyopathy (HCM), which is caused by mutations in cardiac sarcomeric genes and leads to abnormal heart muscle thickening. Complications of HCM include heart failure, arrhythmia, and sudden cardiac death. The dominant-negative c.1208 G>A (p.R403Q) mutation in b-myosin (MYH7) is a common and well-studied mutation that leads to increased cardiac contractility and HCM onset. Here we identify an adenine base editor (ABE) and single-guide RNA system that can efficiently correct this human pathogenic mutation with minimal off-target and bystander editing. We show that delivery of base editing components rescues pathological manifestations of HCM in iPSC-cardiomyocytes derived from HCM patients and in a humanized mouse model of HCM. Our findings demonstrate the use of base editing to treat inherited cardiac diseases and prompt the further development of ABE-based therapies to correct a variety of monogenic mutations causing cardiac disease.
Project description:Background The safety of CRISPR-based gene editing methods is of the utmost priority in clinical applications. Previous studies have reported that Cas9 cleavage induced frequent aneuploidy in primary human T cells, but whether cleavage-mediated editing of base editors would generate off-target structure variations remains unknown. Here, we investigated the potential off-target structural variations associated with CRISPR/Cas9, ABE and CBE editing in mouse embryos and primary human T cells by whole-genome sequencing and single-cell RNA-seq analyses. Results The results showed that both Cas9 and ABE generated off-target structural variations (SVs) in mouse embryos, while CBE induced rare SVs. In addition, off-target large deletions were detected in 32.74% of primary human T cells transfected with Cas9 and 9.17% of cells transfected with ABE. Moreover, Cas9-induced aneuploid cells activated the P53 and apoptosis pathways, whereas ABE-associated aneuploid cells significantly upregulated cell cycle-related genes and arrested in G0 phase. A percentage of 16.59% and 4.29% aneuploid cells were still observable at 3 weeks post transfection of Cas9 or ABE. These off-target phenomena in ABE were universal as observed in other cell types such as B cells and Huh7. Furthermore, the off-target SVs were significantly reduced in cells treated with high-fidelity ABE (ABE-V106W). Conclusions This study raises urgent need for minimizing the off-target SVs of CRISPR/Cas9 and ABE.
Project description:The majority of known pathogenic point mutations in the human genome are C•G to T•A substitutions. Adenine base editors (ABEs), comprised of nuclease-impaired Cas9 fused to adenine deaminases, enable direct repair of these mutations, making them promising tools for precision in vivo genome editing therapies. However, prior to application in patients, thorough safety and efficacy studies in relevant model organisms are needed. Here, we apply adenine base editing in vivo in the liver of mice and cynomolgus macaques to install a splice site mutation in PCSK9 and reduce blood low-density lipoprotein (LDL) levels, a well-known risk factor for cardiovascular disease. Intravenous delivery of ABE-encoding mRNA and a locus-specific single guide (sg)RNA utilizing lipid nanoparticle (LNP) technology induce up to 67% editing in the liver of mice and up to 34% editing in the liver of macaques, leading to a reduction of plasma PCSK9 and LDL levels. We observed rapid clearance of ABE mRNA after LNP-mediated delivery, and neither sgRNA-dependent nor sgRNA-independent off-target mutations are detected in genomic DNA. Together, our findings support safety and feasibility of adenine base editing to treat patients with monogenetic liver diseases.
Project description:The majority of known pathogenic point mutations in the human genome are C•G to T•A substitutions. Adenine base editors (ABEs), comprised of nuclease-impaired Cas9 fused to adenine deaminases, enable direct repair of these mutations, making them promising tools for precision in vivo genome editing therapies. However, prior to application in patients, thorough safety and efficacy studies in relevant model organisms are needed. Here, we apply adenine base editing in vivo in the liver of mice and cynomolgus macaques to install a splice site mutation in PCSK9 and reduce blood low-density lipoprotein (LDL) levels, a well-known risk factor for cardiovascular disease. Intravenous delivery of ABE-encoding mRNA and a locus-specific single guide (sg)RNA utilizing lipid nanoparticle (LNP) technology induce up to 67% editing in the liver of mice and up to 34% editing in the liver of macaques, leading to a reduction of plasma PCSK9 and LDL levels. We observed rapid clearance of ABE mRNA after LNP-mediated delivery, and neither sgRNA-dependent nor sgRNA-independent off-target mutations are detected in genomic DNA. Together, our findings support safety and feasibility of adenine base editing to treat patients with monogenetic liver diseases.
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes Sequence library of miRNAs from a single sample of human foetal mesenchymal stem cells. Results tested and confirmed by northern blotting. Please note that only raw data files are available for the embryonic and neual samples and thus, directly submitted to SRA (SRX547311, SRX548700, respectively under SRP042115/PRJNA247767)