The gene editing technology CRISPR has been arguably the top story in the biomedical world in the last two years, but going forward there is a CRISPR challenger in upstart gene editing technology NgAgo.
For more background on NgAgo and the key first published paper on its genetic modification characteristics see my post here.
In the comments on that post and in discussions I’ve had with other researchers, some key points have crystalized on NgAgo versus CRISPR at this time. As a possible CRISPR challenger, how does NgAgo fare?
Broader possible applicability. The lack of a PAM site requirement for NgAgo means it is almost certain that for some specific gene editing applications, NgAgo will work and CRISPR won’t. Design of NgAgo guides seems to be a simpler matter too because no PAM is needed (more on guides below). In that first NgAgo paper they reported effective editing of 8 different genes with good efficiency so it’s unlikely there is a strongly required DNA sequence context needed for NgAgo. However, it is still formally possible that NgAgo in some contexts will have some kind of preference for certain DNA sequences. Further study will help resolve this more concretely, but so far this is looking like a major plus for NgAgo.
DNA guides should be a lot easier. The use of DNA-based guides will make gene editing easier as opposed to RNA-based guides. At the very least you eliminate a cloning step and you can just order oligos, which you can phosphorylate in your lab to use as guides by transfection.
Stronger targeting specificity. The somewhat longer guide length for NgAgo should mean significantly higher specificity than with CRISPR. It is sort of like having a better GPS.
Further potential for less off-target activity due to nature of NgAgo system. The reported orderly assembly and function of NgAgo leading to an apparent one-hit-and-done nature of cutting could mean the NgAgo system could be less prone to re-cutting and potential spurious outcomes at the desired locus as well as off-target activities. This idea is also further supported by the use of transfected oilgos for NgAgo rather than gRNAs encoded by plasmids as the latter can be integrated and mediate repeated cutting with CRISPR whereas oligos are rapidly degraded. There can also be endogenous gRNA mimics in cells that could lead CRISPR-Cas9 astray, while that endogenous nucleotide mistargeting seems less likely with the NgAgo system.
Lots of potential, but no tidal shift…at least not this year. Those of us who have already invested a lot of time and resources into CRISPR are probably not all going to switch to NgAgo any time soon even if NgAgo is proven better. But gene editing time kind of goes by like “dog years” 7 times faster than normal clock/calendar time (i.e. things move quickly) so NgAgo could relatively rapidly have significant influence if it is indeed ultimately proven to be better in important ways. I know of several labs already gearing up to try NgAgo so stay tuned on that.
Which brings me to a final point that it is such early days on NgAgo that we don’t know for sure if the bullet points above will still hold true in 6-12 months, but it could be very exciting.