Cas9d Ultra Editor
The compact Cas9d Ultra editor was placed in a single AAV viral vector and used to modify a gene in the livers of mice. On August 19, authors published a study on Cas9d Ultra, a compact genetic editor. One of its variants, 9dCBE, changes the letter C in DNA; it was packaged with a guide RNA in a single AAV9 viral vector and administered to newborn mice.
Through five weeks, the editor modified the target region of the Pcsk9 gene in the liver by an average of 15.7%, and the level of LDL cholesterol in the serum was lower than in mice after PBS injection. The base editor makes precise changes to one "letter" of DNA. The guide RNA sets the address in the genome, the CRISPR protein holds the editor in place, and the attached enzyme performs the chemical replacement of the base.
The AAV virus, which carries the genetic cargo into cells, typically holds around 4,700 nucleotides. Large editors are often split between two vectors. In this study, a single AAV9 delivered both the editor and its guide RNA. The Cas9d MG34-1 was chosen due to its size: this protein consists of 747 amino acids and works with a guide RNA of normal length for CRISPR. In a 2022 study, its early version achieved up to 22% base editing on three targets in human cells. The current authors modified four amino acids in the protein and the guide RNA scaffold. In a cellular test, where DNA cutting triggers a fluorescent signal, activity increased from 20.44% to 63.32%.
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PubMed Central (PMC)
Compact 9dBEs Enable Efficient and Precise Genome Editing in Mammalian Cells and In Vivo
Despite the promise of DNA base editors for diverse genome editing applications, their utility remains constrained by off‐target effects, which are exacerbated by short spacers in miniature systems and the large size of Cas9‐derived editors, which ...
August 23, 2026 5
