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Researchers optimize a new CRISPR system for human gene editing

The engineered Cas12b works precisely at human body temperatures

by Megha Satyanarayana
January 24, 2019 | A version of this story appeared in Volume 97, Issue 4


Structures of the three known CRISPR-Cas systems for editing human genomes, Cas9, Cas12a, and the newly developed Cas12b.
Credit: Nat. Commun.
Cas12b (right) is the third CRISPR-based human genome editing system developed by scientists. It is smaller than its cousins, Cas9 (left) and Cas12a (middle), and has been optimized to precisely cut nucleic acids. Regions in color denote differences in structure between the three enzymes.

Researchers at Broad Institute of MIT and Harvard and the National Institutes of Health have expanded the CRISPR gene-editing toolbox. The team has engineered a CRISPR-associated enzyme called Cas12b that they think might be a good way to edit human genes via viral delivery due to its small size. CRISPR-Cas12b joins its larger cousins Cas9 and Cas12a as tools researchers can use to fix gene mutations or to introduce new genetic sequences into genomes (Nat. Comm. 2019, DOI: 10.1038/s41467-018-08224-4).

Konstantin Severinov, a CRISPR expert at Rutgers University who was not involved in the work, says having a robust toolbox benefits scientific research. Giving researchers different CRISPR systems with different properties “makes one’s research more versatile by allowing different engineering strategies, increasing the number of sites one can edit, altering delivery options, and so on,” he says.

To engineer the optimized Cas12b, the research team, led by Feng Zhang of Broad Institute, searched various bacterial species for Cas12b family members that might work well at human body temperature. The most studied Cas12b works best at temperatures too high for use in human cells, Zhang says.

After identifying Cas12b from Bacillus hisashii, the team made two arginine mutations and one glycine mutation in and around the active site of the enzyme to boost its ability to grab onto nucleic acids at 37 °C. The team found that the engineered enzyme cut and edited comparably to its cousins across several test genes.


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