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 developed a therapeutic strategy for beta-hemoglobinopathies aimed at reactivating fetal hemoglobin expression in red blood cells derived from human hematopoietic stem/progenitor cells edited with CRISPR/Cas9 nucleases, cytidine or adenine base editors targeting the fetal gamma-globin promoters. Here, we report the transcriptomic changes occurring in human hematopoietic stem/progenitor cells (obtained from healthy donors) 48 h after transfection with CRISPR/Cas9 nucleases, cytidine or adenine 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:We used RNA-sequencing data to explore the transcriptome-wide effects of cytosine and adenine deaminases on gene expression induced by base editors.
2021-06-01 | GSE158693 | GEO
Project description:Functional Correction of CFTR Mutations in Human Airway Epithelial Cells using Adenine Base Editors
Project description:A variety of base editors have been developed to achieve C-to-T editing in different genomic contexts. Here, we compare a panel of five base editors on their C-to-T editing efficiencies and product purity at commonly-editable sites, including some human pathogenic C-to-T mutations. We further profile the accessibilities of twenty base editors to all possible pathogenic mutations in silico. Finally, we build the BEable-GPS (Base Editable prediction of Global Pathogenic SNVs) database for users to select proper base editors to model or correct disease-related mutations. This in-vivo comparison and in-silico profiling catalogs the availability of base editors and their broad applications in biomedical studies.
Project description:Adenine and cytosine base editors (ABEs and CBEs) represent a new genome editing technology that allows the programmable installation of A-to-G or C-to-T alterations on DNA. We engineered Streptococcus pyogenes Cas9-based adenine and cytosine base editor (SpACE) that enables efficient simultaneous introduction of A-to-G and C-to-T substitutions in the same base editing window on DNA.