Scientists at the Francis Crick Institute in London have found simple rules that could hugely improve the accuracy of CRISPR gene editing.
Dr Paola Scaffidi, who led the study, said it was previously assumed that outcome of CRISPR editing was unpredictable and led to random insertions and deletions at the DNA target site.
“Until now, editing genes with CRISPR has involved a lot of guesswork, frustration and trial and error”, Dr Scaffidi said.
“The effects of CRISPR were thought to be unpredictable and seemingly random, but by analysing hundreds of edits we were shocked to find that there are actually simple, predictable patterns behind it all.“
The discovery is based on an analysis of the genetic letters – A, T, C and G – that comprise the guide RNA, which directs Cas9 to the point of the genome that needs editing.
The researchers found the precision of the outcome depends on the fourth letter from the end of the guide RNA. Having a G in this position leads to a lack of precision in deletions, whereas an A or T here will result in insertions which are much more predictable.
Their study, published last week in the journal Molecular Cell, has thrown up several other new rules that are likely to improve the use of the technique, and ultimately its efficiency and safety for potential clinical use in the future.
Dr Scaffidi said “this will fundamentally change the way we use CRISPR, allowing us to study gene function with greater precision and significantly accelerating our science".
Source: Chakrabarti, A.M., Henser-Brownhill, T., Monserrat, J., Poetsch, A.R., Luscombe, N.M., Scaffidi, P. (2018) “Target-Specific Precision of CRISPR-Mediated Genome Editing”, Molecular Cell, available at doi: 10.1016/j.molcel.2018.11.031