According to the latest issue of Scientific Progress, researchers at the Massachusetts Institute of Technology (MIT) have discovered a Cas9 enzyme that targets almost half of the genomic locus, greatly expanding the scope of gene editing tools.
Despite the considerable success of gene editing tools in recent years, the number of sites accessible to CRISPR-Cas9 on the genome remains limited. This is because CRISPR requires a specific sequence flanking the genomic targeting site, the Protospacer Adjacent Primitive (PAM), to identify this site. The most widely used Cas9 enzyme, S. pyogenes Cas9, requires two G nucleotides as its PAM sequence, which greatly limits the number of sites it can target (about 9.9% of the genome). .
Professor Joseph Jacobson, head of the molecular machine research group at MIT, said that CRISPR is like a very accurate and efficient postal system. As long as the postal code ends in zero, you can reach exactly where you want to go. But because it is very accurate and specific, it also limits the number of locations that can be visited.
To develop a more versatile CRISPR system, researchers used algorithms to perform bioinformatics searches of bacterial sequences to determine if similar enzymes with lower PAM restriction requirements exist. To this end, they developed a data analysis software tool and built a synthetic version of CRISPR in the lab to evaluate the performance of newly discovered enzymes.
The study found that the most successful enzyme was ScCas9 from Streptococcus mutans, which is very similar to the currently widely used Cas9 enzyme, but is capable of targeting DNA sequences that are not targeted by common enzymes. The new enzyme requires only one, but not two, G nucleotides as its PAM sequence, opening up more targeting sites on the genome, allowing CRISPR to target many specific disease mutations that have previously exceeded the system.
For example, a typical gene is about 1000 bases in length, and if simply knocking out the entire gene, it can provide researchers with many different targeting sites. However, diseases such as sickle cell anemia are caused by single base mutations, which makes it more difficult to target.
Jacobson believes that base editing is not just a matter of finding and knocking out anywhere in the gene at 1000 bases, but a problem of entering and correcting the genes that you want to change in a very precise way. The new CRISPR tools have great potential in these applications and can track every locus on the genome in the future. (Reporter Feng Weidong)
Source: Technology Daily
Zhejiang Ocean Family Co., Ltd., , https://www.ocean-family.com