Researchers have discovered a technique that could block the effects of a powerful gene-editing tool to protect adjacent genes against accidental alteration. The breakthrough could be the beginning of a major step forward for genetic engineering.

Scientists at the University of California (UC) in San Francisco researchers have discovered how to switch off the effects of the CRISPR gene editing system. CRISPR has been a major advance for gene editing, but there are difficulties in limiting its effects on adjacent genes. So far this has militated against its use in research, most obviously, into the human genome.

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Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR), or CRISPR/Cas9 to give its full name, is a revolutionary tool for editing genes. It is a particular kind of short, repeating sequence of DNA which was first identified in E.Coli bacteria by Japanese scientists.

The regular patterning in the sequence is the key to its use as a tool – a very crude comparison could be the regular patterning of a spanner, wrench head.

Similar sequences were then identified in other simple organisms.In 2012, scientists in UC Berkeley announded that they could extract these DNA sequences to create a gene editing tool. The CRISPR/Cas tool system involves CRISPR, a Cas protein called Cas9 (which assists in unwinding DNA), and hybrid RNA. The tool can be programmed to identify, cut and/or replace any gene sequence.

The system is much easier to use than earlier gene editing tools, meaning the breakthrough has phenomenal implications for genetic engineering. However, while CRISPR is believed to have the potential to modify crops, viruses and animal cells – including human cells – it has so far been something of a blunt tool. Sometimes it alters nearby cells that scientist do not want changed and this can cause unintended and unwanted outcomes.

However, the UC San Francisco team have discovered that some anti-CRISPR proteins may be able to protect non-target cells from the effects of the gene editing tool.

"Researchers and the public are reasonably concerned about CRISPR being so powerful that it potentially gets put to dangerous uses," said Jospeh Bondy-Denomy, one of the researchers. "These inhibitors provide a mechanism to block nefarious or out-of-control CRISPR applications, making it safer to explore all the ways this technology can be used to help people."

The UC team scrutinised strains of Listeria and evaluated its proteins to find the right protein that could block CRISPR. This breakthrough is likely to herald a big step forward in the use of CRISPR, and therefore genetic engineering. Most pertinently, it may be decisive for assuaging critics of the use of the tool for research into altering the human genome.