In a mere seven years, Cas9 has shown itself to be a formidable gene editor, employed in humans, plants, animals and bacteria to quickly and accurately cut and splice DNA, transforming biology and opening new avenues for treating disease.
But a new kid on the block, CasX, may give Cas9 a run for its money. Discovered two years ago by UC Berkeley scientists Jill Banfield and Jennifer Doudna in some of the world’s smallest bacteria, the protein is similar to Cas9, but quite a bit smaller: a big advantage if you’re trying to deliver a gene editor into a cell.
But would it work outside its native bacteria?
According to a study published in Nature, CasX is, in fact, a potent and efficient gene editor in both bacteria and human cells. Its design is similar to Cas9 and its well-studied cousin, Cas12, but is different enough that it appears to have evolved in bacteria independently of the other Cas proteins. It can cut double-stranded DNA like Cas9, can bind to DNA to regulate genes, and it can be targeted to specific DNA sequences like other Cas proteins.