Researchers from the state-run Chinese Academy of Sciences claimed in a recently published study to have developed a gene-editing method that is allegedly “more efficient and safer” than established techniques because it uses the CRISPR gene-editing tool to target RNA instead of DNA, the South China Morning Post (SCMP) reported on Wednesday.
Relaying the development on August 17, the Hong Kong-based newspaper wrote:
Scientists from the Chinese Academy of Sciences said the new tool uses CRISPR (clustered regularly interspaced short palindromic repeats) technology – a natural defence mechanism that allows bacterial cells to detect and destroy the viruses that attack them and has become one of the most commonly used gene-editing techniques in recent years.
The most widely used system employs CRISPR-associated protein-9 (Cas9), an enzyme that can cut the two strands of DNA in the genome to add or remove material.
But the new approach uses the Cas13 enzyme, which targets RNA. The technique is believed to be safer since RNAs are transient molecules that only exist in the cell for a limited period of time and are not integrated into the genome.
“Compared to DNA editing techniques, the Cas13 gene editing system is safer, and the effects are more controllable and short-lived,” Yang Hui, an author of the study and a researcher at the Chinese Academy of Sciences’ Brain Science and Intelligence Technology center, recently told Chinese reporters.
A major flaw within the new RNA-based gene-editing method — known as “collateral cleavage, or its ability to cleave nontarget RNAs” — has limited its usage in clinical applications, the SCMP observed on Wednesday.
“Due to this so-called collateral effect, Cas13 can degrade both target and non-target RNAs at random, thus making it difficult to design experiments and interpret results when using Cas13,” the study’s research team recently said as quoted by the Chinese Academy of Sciences’ website.
A study published in the scientific journal Nucleic Acids Research in late June “highlight[ed] the need for caution when designing and interpreting Cas13-based knockdown experiments.” The study’s researchers urged caution in regard to the gene-editing method because of its “potential for promiscuous cleavage of nearby RNAs (so-called collateral damage).”
“[W]e found that the off-target effects of RxCas13d, a commonly used Cas13 effector, can be as strong as the level of on-target RNA knockdown. The extent of off-target effects is positively correlated with target RNA expression levels, and collateral damage can be observed even after reducing RxCas13d/guide RNA levels,” the authors wrote.
The study, titled “CRISPR/Cas13 effectors have differing extents of off-target effects that limit their utility in eukaryotic cells,” was funded by the U.S. government’s National Institutes of Health (NIH) and the American Heart Association. It was co-authored by a consultant for Laronde, which is a U.S.-based biotech research firm that specializes in RNA-based gene editing.
The People’s Court of Nanshan District of Shenzhen, China, sentenced Chinese biophysicist He Jiankui to three years in prison on December 30, 2019, for “illegal medical practice.” He was charged with the crime for using the CRISPR gene-editing system to alter the DNA of unborn babies.
He revealed that he had committed the illegal act during an interview with the Associated Press (AP) in November 2018, during which he announced the birth of “the world’s first genetically edited babies — twin girls.”
“He said he altered embryos for seven couples during fertility treatments, with one pregnancy resulting thus far. He said his goal was not to cure or prevent an inherited disease, but to try to bestow a trait that few people naturally have — an ability to resist possible future infection with HIV, the AIDS virus,” the AP relayed after conducting an exclusive interview with the biophysicist.
He’s experiment shocked the global scientific community because it was the first known use of gene-editing technology on human embryos, an action considered unethical and illegal worldwide. Chinese authorities released He from prison in April, according to the British scientific journal Nature.
