CRISPR (Credit: Ernesto del Aguila III, NHGRI)

It’s coming up to nearly a year since that study was published, claiming that CRISPR-Cas9 caused hundreds of unintended mutations in the genome. 


CRISPR Gene Editing Can Cause Hundreds of Unintended Mutations


Since then, a more recent study was published squashing those allegations. We are coming to you today with the latest installment, which sees the authors themselves, revealing that they are unable to replicate the controversial result. 

Although the reports of new mice experiments didn’t introduce such mutations, it goes a long way in confirming that alarm bells should never have been sounded in the first place, writes Science Alert

In the new research, the team conducted whole-genome sequencing on two mouse lines that had undergone a CRISPR-editing procedure. But, unlike their first study, no unintended gene variants showed up after the genetic alterations. 

The thing is, it wasn’t the ‘big picture’ approach that scientists had a problem with, instead, it was in the shortcomings in their method. 


Study Squashes Any Fears That CRISPR Triggers Unintended Gene Mutations


Soon after its initial publication, a critique of the original paper by another team pointed out that the two gene-edited mice in the experiment were genetically more closely related to each other than to the third, ‘control’ mice. 

More concerningly, the implication was that the ‘unexpected mutations’ the team had detected weren’t the result of CRISPR, but rather due to the pre-existing genetics of the mice selected for the study. 

Since their sample of animals in the experiment was so small, the results were not only unreliable, they were also misleading. 

 Naturally, this work created a lot of controversies. The authors had concerns, but rather than airing them, they re-visited the matter in their new research. 

While defending “reasonable concern” about such unintended mutations, the authors conclude the new results “support the idea that in specific cases, CRISPR-Cas9 editing can precisely edit the genome at the organismal level and may not introduce numerous, unintended, off-target mutations.”

Despite many arguing that the original paper should be retracted, this hasn’t happened yet. However, at least for now, new data has come to light, and important things have been learned from such research.