biostudies-literatureUnknown41(5)Lam DKCytosine base editors (CBEs) enable programmable genomic C·G-to-T·A transition mutations and typically comprise a modified CRISPR-Cas enzyme, a naturally occurring cytidine deaminase, and an inhibitor of uracil repair. Previous studies have shown that CBEs utilizing naturally occurring cytidine deaminases may cause unguided, genome-wide cytosine deamination. While improved CBEs that decrease stochastic genome-wide off-targets have subsequently been reported, these editors can suffer from suboptimal on-target performance. Here, we report the generation and characterization of CBEs that use engineered variants of TadA (CBE-T) that enable high on-target C·G to T·A across a sequence-diverse set of genomic loci, demonstrate robust activity in primary cells and cause no detectable elevation in gNature biotechnology686-697https://www.ebi.ac.uk/biostudies/studies/S-EPMC10188367biostudies-literatureImproved cytosine base editors generated from TadA variants.PMC10188367Lee KDPeraro LLee SJFeliciano PRSawyer CArif ABohnuud TOrtega MAGaudelli NMGehrke JMSchwaegerle NDLam DKCiaramella GYoung LFernandez TPGrayson PfalseImproved cytosine base editors generated from TadA variants.Cytosine base editors (CBEs) enable programmable genomic C·G-to-T·A transition mutations and typically comprise a modified CRISPR-Cas enzyme, a naturally occurring cytidine deaminase, and an inhibitor of uracil repair. Previous studies have shown that CBEs utilizing naturally occurring cytidine deaminases may cause unguided, genome-wide cytosine deamination. While improved CBEs that decrease stochastic genome-wide off-targets have subsequently been reported, these editors can suffer from suboptimal on-target performance. Here, we report the generation and characterization of CBEs that use engineered variants of TadA (CBE-T) that enable high on-target C·G to T·A across a sequence-diverse set of genomic loci, demonstrate robust activity in primary cells and cause no detectable elevation in g2023-01-01T00:00:00Z2023 May2026-05-28T08:26:14.862Z2025-04-05T21:10:01.028ZS-EPMC101883673662414910.1038/s41587-022-01611-9