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Recent years have seen an acceleration in the number of CRISPR endonucleases available in the bioengineer’s toolbox. Since CRISPR was first turned into an editing tool in 2012, Cas endonucleases have been isolated from many different bacterial species, with different protospacer adjacent motif specificity, activity windows, or guide RNA requirements. Similarly, protein engineering and mutant selection has produced a proliferation of fusions proteins: Cas9 or Cas12a with deaminase for DNA editing; Cas13a with deaminase for RNA base editing; Cas12k with transposase for site-specific DNA integration; and even deactivated Cas9 (dCas9) linked to transcriptional or epigenetic regulators. This minifocus provides an overview of these tools, their use in basic research and provides commentary on progress in turning them into therapeutic modalities.
As CRISPR–Cas9 enters human testing, the blistering pace of progress in preclinical research is offering a bewildering array of options for therapeutic gene editing.
As CRISPR therapies move into clinical testing, David Schaffer and colleagues review a raft of different delivery technologies being road tested to address cargo capacity limitations, maximize potency, minimize off-target effects and avoid immunogenicity.