Programmable base editing of A•T to G•C in genomic DNA without DNA cleavage.
Level 5 - mechanism / opinion, no new human data
In vitro molecular engineering and cell culture study (bench research).
PubMed 29160308 · doi:10.1038/nature24644
What was done
The authors engineered an adenine base editor (ABE) by evolving a transfer RNA adenosine deaminase to operate on DNA and fusing it to a catalytically impaired CRISPR-Cas9 mutant. They evaluated seventh-generation ABEs in human cells for target A•T to G•C conversion efficiency, product purity, indel formation, and off-target modifications compared to standard Cas9 nuclease-based methods.
What was found
Seventh-generation ABEs achieved approximately 50% conversion efficiency of targeted A•T to G•C base pairs in human cells. Product purity was typically at least 99.9%, and indel rates were typically no more than 0.1%. Compared to Cas9 nuclease-based methods, ABEs introduced point mutations with higher efficiency, greater purity, and fewer off-target modifications.
Why it matters
This tool enables the programmable installation of all four transition mutations without double-stranded DNA cleavage. It provides a targeted mechanism to correct C•G to T•A transitions, which constitute half of known human pathogenic point mutations.
Limits
Findings are limited to in vitro protein evolution and cell culture assays, without in vivo delivery or animal safety data reported in the abstract. Specific cell types, sample sizes, and detailed locus-specific variability are not provided in the abstract text.
Cited by
- supports David Liu at Harvard developed CRISPR base editors that change nucleotides at targeted sites without generating double-stranded DNA breaks by using a deaminase domain.