healthHealth and Medicine

Debate Rages Over Safety Of CRISPR Gene-Editing Technique


Robin Andrews

Science & Policy Writer

Note: this is not actually how CRISPR works, but you get the idea. vchal/Shutterstock

In the last few years, CRISPR – the precise and easily available gene-editing technique – has gone from strength to strength. Right now, it’s more potential than practical, but its uses are almost countless. From removing genetic diseases from babies before they are born to causing cancerous cells to self-destruct, it’s more likely than not it will rapidly become a key tenet of modern medicine.

The technique is being used in a massive number of trials right now, and a few of them have highlighted that it’s far from fully understood and far from being perfected. One particularly controversial study released back in May claimed that CRISPR was in fact dangerous, but now another study, currently sitting on the bioRxiv pre-print server, has dismissed this research and its "provocative conclusion" as seriously flawed.


The original study looked at the effect of using CRISPR in mice, and found that it introduced a large number of previously unknown mutations into their genome. The mice were blind, and the gene-editing technique was used to effectively cure them of this affliction.

While it was successful, it also appeared to inadvertently lead to mutations elsewhere – nearly 1,600 of them, in fact. Of these, just over 100 mutations were more serious, involving not just DNA base pair changes, but full deletions or insertions of new segments of DNA.

What is CRISPR? Wired via YouTube

Although there were no physiological side effects, unwanted mutations are always a cause for concern. As a result, the authors concluded that CRISPR has the potential to be quite hazardous to the normal operation of biological systems.


When this study was released, it caused quite a stir. Similar studies had only shown a handful of changes, which turned out to be harmless. People were quick to point out that the study was very small, involving just three mice, and that the changes made elsewhere on their genomes could easily be attributed to normal genetic mutations that take place all the time.

Now, a Harvard University-led team have suggested that these “unwanted mutations” have a far more innocuous explanation.

Apart from the fact that there is no direct line of evidence demonstrating that CRISPR caused the mutations, the team note that the mice used in the study were very closely related. This means that whatever mutations one had, the other would have had too.

Combined with the fact that the mutations were found nowhere near the actual gene-editing site, the authors conclude that, once again, CRISPR is probably safe after all.


"Given these substantial issues, we urge Schaefer et al. to revise or re-state the original conclusions of their published work so as to avoid leaving misleading and unsupported statements to persist in the literature," the authors of the pre-print study conclude.

Plenty more trials are needed to verify this, of course – but the point here is that this study raised a massive red flag when it wasn’t justified in doing so.

[H/T: New Scientist]


healthHealth and Medicine
  • tag
  • gene editing,

  • study,

  • response,


  • controversial,

  • dangerous,

  • explanation,

  • damaging