Gene editing method can work on DNA and RNA

By SABRINA CHEN | March 1, 2018

CRISPR-Cas9 is a molecular genetic method that allows scientists to cut DNA at specific sites of the genome. Traditionally, the technique has been used in animal models to delete certain genes from the DNA in order to attack viruses or correct genetic defects.

CRISPR is an abbreviation for clusters of regularly interspaced short palindromic repeats, or specific regions of DNA that can be recognized by a protein called Cas9. 

The Cas9 protein can target foreign DNA to remove it from the genome or it can help alter specific sequences of DNA by replacing the cut sites with another gene.

Recently, scientists at the University of Michigan have discovered a protein that can cut both DNA and RNA, NmeCas9. NmeCas9 is the first protein of it’s kind, since traditional Cas9 proteins are only able to cut DNA. 

Researchers accidentally found the NmeCas9 protein when they studied the bacteria Neisseria meningitidis, the bacteria that causes meningitis.

“[Nme] is capable of programmable, RNA-guided, site-specific cleavage and recognition of single-stranded RNA targets,” read the journal article, published in Molecular Cell.

DNA and RNA are the two molecules that carry genetic information in the cell. Whereas DNA is important for long term storage and transmission of genetic information between generations, RNA’s main function is to use the genetic code to make proteins that the cell can use.

According to Yan Zhang, assistant professor of biological chemistry at the University of Michigan and the primary investigator of the research team, NmeCas9 is particularly powerful because it can work on all the genetic material in the cell at once, instead of only altering the DNA.

“The fact that our protein has dual function — able to target both DNA and RNA — gives us the opportunity to develop platforms to do dual targeting,” Zhang said, according to ScienceDaily. “It may make it possible to perform CRISPR cutting on both RNA and DNA at once, or alternatively just on single-stranded messenger RNA without affecting genomic regions at all.”

CRISPR has been used to delete genes in mice and to study the functions of those deleted genes. It also can be used to insert other genes. Though human testing is still in its very early stages, scientists note that it has the potential to cure malaria by inserting malaria resistance genes in the human genome. CRISPR could also potentially be used to attack many diseases that have no current cure such as HIV, Alzheimer’s, sickle-cell disease and heart disease.

In fact, just last week, China announced eight clinical CRISPR trials in an attempt to treat cancer. Cancers that are being targeted include lung cancer, bladder cancer, cervical cancer and prostate cancer.

“China is starting to pull ahead of other parts of the world — maybe for the time — in regards to biomedicine,” Hallam Stevens, an anthropologist at the Nanyang Technological University, said, according to NPR. “They’ve been really investing heavily in it over the last couple of decades and it’s starting to pay off in a big way.”

In the United States, although there have been advances in the CRISPR mechanism, such as the NmeCas9 gene, only one CRISPR cancer study has been approved. Part of this has to do with the more stringent study regulations in America and the general distrust the public has in gene editing techniques.

“My concern is: Are we really ready? There’s so much about CRISPR that we don’t understand,” Lainie Ross, a bioethicist at the University of Chicago, said, according to NPR. “We could be doing more harm than benefit. We need to be very, very cautious. This is an incredibly powerful tool.”

Others believe that China is ready to take on using CRISPR in human healthcare settings. 

China U.S. Healthtech Forum Co-President Jillian Ho said that she predicts China may have success in using these new gene editing methods.

“The biotechnology industry in China has been rising rapidly, and many media platforms such as Forbes and Business Insider have been labeling China as the biotech powerhouse,” Ho said. “Overall I think if the technology in China is ready for CRISPR to be used in humans, I don’t see any real problem.”

Indeed, clinical trials in humans in combination with recent NmeCas9 findings could have huge implications for the fields of genetics and biomedical research. 

“If NmeCas9 works in live cells as it has in vitro, we can develop it as a tool to edit the messenger RNA transcript, which means we might be able to block a gene product without manipulating the gene itself,” Zhang said.

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