Since it burst onto the scientific scene in 2012, CRISPR/Cas9 has been "hailed as dramatically easier, cheaper, and more versatile than previous technologies" for altering genomes, says Nature News.
But it's not perfect, and researchers are already looking for alternatives.
Some researchers have jumped on a new gene-editing system called NgAgo. Others are using a mini-Cas9, which is small enough to put into a virus. "Last December, two groups used the mini-me Cas9 in mice to correct the gene responsible for Duchenne muscular dystrophy," Nature News says.
There are some teams that are even looking beyond Cas9. Because Cas9 will only cut in the presence of a certain DNA sequence, it's challenging to use in certain contexts, the article says. So some researchers are looking to enzymes from microbes that could have different sequence requirements. One enzyme, Cpf1, is smaller than Cas9. Another, called C2c2, targets RNA instead of DNA.
And then there are the researchers who want to be able to swap certain sequences in a gene with other sequences, rather than just deleting them. Some teams are modifying Cas9 and tethering it to an enzyme that allows Cas9 to targets the given sequence, but not to cut it. Instead, Nature News says, the attached enzyme switches the DNA letters that are already there.
Nature News spoke to Harvard Medical School's George Church who said the search for CRISPR alternatives is "a reminder of how fragile every new technology is."
And some researchers are even going back to pre-CRISPR technologies like TALENs and zinc finger nucleases. Depending on the application, some investigators told GenomeWeb, these older methods still work very well.