There is an emerging concern among scientists that the gene-editing technique CRISPR “might inadvertently alter regions of the genome other than the intended one,” says STAT, the health and medicine site. Dr. J. Keith Joung of Massachusetts General Hospital says that algorithms used to predict off-target effects of gene editing “miss a fair number” of them.
“Their tools [algorithms] are used in a lot of papers but they really aren’t very good at predicting where there will be off-target effects,” he said. “We think we can get off-target effects to less than 1 percent but we need to do better” if the technique is to be used in medicine. Joung spoke at a hematology workshop last week, said STAT.
CRISPR is a hit among plant scientists because it is cheaper and faster than traditional biotechnology that transfers genetic material from one species into another. Gene editing also is outside the federal regulation of biotech, which is focused on genetic transfers and preservation of seed purity. The agribusiness sector says gene editing is safe and should remain exempt from regulation in the new biotech code being developed by the federal government. The National Academy of Sciences says the United States should conduct safety reviews of all plant varieties that pose potential hazards, not just the results of genetic engineering.
In April, USDA said a white button mushroom, altered by CRISPR to reduce browning, was exempt from regulation because it contained no added genetic material — the first CRISPR-developed organism to get the green light for commercialization, said the journal Nature. A few days later, Pioneer, the second-largest seed company in the world, said it created a new variety of high-starch “waxy” corn with CRISPR. The variety could be offered for sale to U.S. farmers within five years, pending field trials and regulatory review.
According to Joung, off-target effects occur because more than one site in a genome can have the same string of nucleotides targeted by CRISPR. Further, he said the algorithms used to predict off-target effects may not be comprehensive. “Scientists from some of the leading genome-editing companies said they are confident they will be able to minimize off-target CRISPR’ing, by picking ‘high-quality’ guide RNAs, among other methods,” said STAT.