The new tools, developed by the labs of CRISPR pioneers Jennifer Doudna and Feng Zhang, are showcased in two studies published today in the journal Science. In one paper, Doudna’s team describes a system called DETECTR, which can accurately identify different types of the HPV virus in human samples. In the second paper, Zhang’s team shows an upgraded version of SHERLOCK — which was shown last year to detect viruses like Zika and dengue, as well as other harmful bacteria — in human samples.
The CRISPR used in the first Science study is called CRISPR-Cas12a. Doudna’s team discovered that when this type of CRISPR snips double-stranded DNA, it does something interesting: it starts shredding single-stranded DNA as well
the CRISPR system is programmed to detect the HPV DNA inside a person’s cells. When CRISPR detects it, it also cuts a “reporter molecule” with single-stranded DNA that releases a fluorescent signal. So if the cells are infected with HPV, scientists are able to see the signal and quickly diagnose a patient. For now, DETECTR was tested in a tube containing DNA from infected human cells, showing it could detect HPV16 with 100 percent accuracy, and HPV18 with 92 percent accuracy.
Called SHERLOCK, this system uses a variety of CRISPR enzymes, including Cas12a. Last year, Zhang’s team showed that SHERLOCK uses CRISPR-Cas13a to find the genetic sequence of Zika, dengue, and several other bacteria, as well as the sequences associated with a cancer mutation in a variety of human samples, such as saliva. Now, the team has improved the tool to be 100 times more sensitive and detect multiple viruses — such as Zika and dengue — in one sample simultaneously. It does this by combining different types of CRISPR enzymes, which are unleashed together to target distinct bits of DNA and RNA, another of the major biological molecules found in all forms of life. Some enzymes also work together to make the tool more sensitive.
If you read Doudna’s book, featured in the H+ “Key Books” section, you realise the enormous progress we made in the last 10 years in terms of DNA manipulation thanks to CRISPR, and yet you have a clear understanding that we are just scratching the surface of what is possible.