The gene editing tool known as CRISPR-Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats) enables permanent modification of genes within living organisms has been in existence only for a few years. But already, scientists are coming up with novel offshoot applications of the breakthrough technology.
Now, a CRISPR protein that targets RNA has been adapted by scientists as a rapid, inexpensive, and sensitive diagnostic tool.
The tool, which uses the Cas13a enzyme, (previously known as C2c2) and is called SHERLOCK (Specific High-sensitivity Enzymatic Reporter unLOCKing), was developed by researchers from the Broad Institute of MIT and Harvard, the McGovern Institute for Brain Research at MIT, the Institute for Medical Engineering & Science at MIT, and the Wyss Institute for Biologically Inspired Engineering at Harvard University.
It can be used to diagnose infections, such as Zika and dengue, with a high level of sensitivity. The upgrade could help assist the progress of rapid detection and diagnosis of many other viruses and pathogens, too.
Although some methods exist for detecting genetic sequences, they have concessions in sensitivity, specificity, simplicity, cost, and speed. In the search for a more effective method, Feng Zhang, Jonathan S. Gootenberg and colleagues turned to a CRISPR-Cas system that targets RNA.
Targeting RNA With CRISPR
Binding the target RNA activates this particular Cas enzyme to easily sever nearby RNA. They exploited this by including a reporter RNA that releases a fluorescent signal when it is cleaved, and used a technique, called recombinase polymerase amplification, to further boost sensitivity.
The combination resulted in a system that could detect rather low titers of Zika virus in serum, urine, and saliva. SHERLOCK can also be used to measure viral load, the authors demonstrated.
They also showed that the technique was effective at identifying various bacterial strains, even differentiating between strains of bacterial pneumonia with different resistance mutations. Finally, the researchers showed that SHERLOCK can be used to detect different cancer mutations.
“This new CRISPR based platform has the potential to be developed as a point of care diagnostic that could be as easy to use as an at-home pregnancy test,”
according to James Collins, MIT professor of engineering.
Jonathan S. Gootenberg et al.
Nucleic acid detection with CRISPR-Cas13a/C2c2
Science, 2017 DOI: 10.1126/science.aam9321