An MIT group consisting of the CRISPR pioneer Feng Zhang and 18 of his colleagues recently published a paper in Science demonstrating a new platform for using CRISPR technology as a diagnostic tool for detecting nucleic acids. The CRISPR-based diagnostic tool (or CRISPR-Dx) may be valuable for applications ranging from detecting the presence of bacterial or viral pathogens to nucleic acid markers for genetic diseases or cancer.
The new CRISPR diagnostic tool is based upon the RNA-guided, RNA-targeting CRISPR effector Cas13a (previously known as C2c2) and was named SHERLOCK (Specific High Sensitivity Enzymatic Reporter UnLOCKing). According to the researchers, the new diagnostic tool relies on the “‘collateral effect’ of promiscuous RNAse activity upon target recognition.” By combining the collateral effect of Cas13a with isothermal amplification, the researchers created a molecular detection platform described as engaging in rapid detection of DNA or RNA down to the highly sensitive attomolar level (10-18 moles per liter).
According to the researchers, the SHERLOCK platform was found to be effective at detecting Zika and Dengue virus at low viral loads in clinical isolates as well as cell-free DNA fragments of low-frequency cancer mutations. The platform was further evaluated for its accuracy in discerning between closely related strains of pathogens. Based upon their tests, the researchers demonstrated that the SHERLOCK platform was capable of distinguishing targets containing only a single-base mismatch. In addition to these strengths, the researchers describe this newly developed SHERLOCK system as highly portable and estimate that a single SHERLOCK field test could cost as little as 61 cents.
The future of this CRISPR diagnostic tool may be affected by the ongoing litigation over the patent rights to CRISPR technology in eukaryotic cells. Although the MIT Broad Institute and Harvard won a legal victory earlier this year over the University of California and the University of Vienna for the patent rights to a CRISPR-Cas9 system, the University of California has recently appealed this decision to the Federal Circuit. Given the differences between the earlier CRISPR-Cas9 and current Cas13a technology, we will have to wait and see how the ongoing dispute might affect intellectual property rights in the current technology.