Base Editing: A new category in CRISPR gene editing
Base editors have two components: First, we use a CRISPR enzyme, which can be programmed to specifically target any location within the genome. Depending on the choice of CRISPR enzyme, we can target either DNA or RNA. Unlike nuclease editing, base editing enzymes are modified to avoid cutting the DNA or RNA once they bind to the target site.
Instead, an editing enzyme is tethered to the modified CRISPR enzyme and directly converts one base to another. The initial versions of base editors make edits using deaminases, which produce predictable chemical modifications to nucleobases (A-to-G or C-to-T for cytidine or adenosine deaminases, respectively). When targeting DNA, additional components of the technology help influence repair pathways to make the edit permanent. Because the system is modular, selection of different CRISPR enzymes or deaminases produces base editors with different gene targeting and editing capabilities.
DNA base editors have the potential to permanently correct or modify a gene after one-time delivery to the target tissue. RNA base editors can deliver either long-term or transient modifications of protein function based on constitutive or short-term delivery of the editor. In both cases, the final gene sequence expressed by the cell is corrected, creating a functional protein and treating the disease.
Using this technology, we believe we can precisely repair a variety of disease-causing point mutations, write in beneficial genetic variations known to protect against disease, or modulate expression of disease-causing genes.
Because base editing directly converts a base in an existing gene, it is not reliant on importing new DNA sequences. Base editing also occurs in both dividing and non-dividing cells, and the resulting edited gene maintains its normal regulation and expression level. The base editor is designed to minimize the frequency and impact of any “off-target” genetic changes, both within the target gene and elsewhere across the genome.
To create base editor therapeutics, Beam is working with a variety of validated and emerging technologies for delivering base editors to different tissues and cell types.