Diagnostic scissors
CRISPR Cas12a is a modern genome editing tool
The Cas12a enzyme was discovered in 2015 and was initially positioned as a more effective replacement and supplement to the Cas9 enzyme.
Researchers Janice Chen, Enbo Ma and Lucas Harrington from the University of California at Berkeley have discovered an interesting feature of Cas12a: when it dissects the double DNA chain in the target site, it also triggers the process of indiscriminately cutting all single-stranded DNA in the sample.
For genome editing, this feature of the Cas12a enzyme has not become a problem, since the target DNA sites usually consist of two strands. But the scientists decided to use a single DNA strand with a signaling protein in combination with CRISPR-Cas12a to develop a diagnostic tool: when Cas12a finds and binds to the target molecule, a signaling fluorescent protein is released.
The authors named the new diagnostic system DETECTR – from DNA Endonuclease Targeted CRISPR Trans Reporter. It can be used to detect genetic mutations, oncological diseases, antibiotic resistance, bacterial and viral infections in a variety of biological materials, including blood, saliva, urine and feces.
The target DNA is enhanced by recombinase polymerase amplification (RPA), a method of rapid multiplication of genetic material. This makes it more "noticeable" for Cas12a and increases the sensitivity of the test. When the target DNA and Cas12a interact, the process of cutting all single-stranded DNA, including DNA associated with a fluorescent protein (marked with a gold asterisk), is started. The release of protein indicates a positive result of the analysis.
The DETECTR system was tested on samples containing several different types of human papillomavirus (HPV) at the same time. She was able to detect samples with the most "dangerous" HPV types 16 and 18 in attomolar concentrations (100 molecules per milliliter of solution).
The accidental discovery of an unusual property of Cas12a underscores the importance of deep fundamental research: simple curiosity led to the creation of an almost universal diagnostic tool.
Article by J. S. Chen et al. CRISPR-Cas12a target binding unleashes discriminate single-stranded DNase activity published in the journal Science.
Aminat Adzhieva, portal "Eternal Youth" http//vechnayamolodost.ru based on materials from UC Berceley: CRISPR scissors, Cas12a, enables cutting-edge diagnostics.