July 10, 2020

The Niche

Knoepfler lab stem cell blog

Will new gene editing tech NgAgo challenge CRISPR?

2020 Update: early NgAgo reports have been mostly discredited and there is doubt on its function as a gene-editing method.


What could be better than CRISPR for gene editing?

A new genetic modification technology called NgAgo has some researchers really excited. How does it compare to CRISPR?

I’ll admit it that as a scientist who works on genetics and genomics, I am really enjoying the power and simplicity of CRISPR-Cas9 type technology for genome editing. We are working with it extensively in my lab. One of the remarkable things about CRISPR is how fast the technology has evolved in just the last 2 years.

NgAgo
NgAgo, Figure 5, Nature Biotechnology

Despite all that warp speed for CRISPR, some are asking: could the new method zoom past CRISPR?

While NgAgo is indeed a nifty new genome editing technology based on DNA guides instead of RNA guides, it’s not going to immediately race ahead of CRISPR…not yet any way. Still it’s got people buzzing.

A recent Nature Biotechnology paper from Chunyu Han’s lab, DNA-guided genome editing using the Natronobacterium gregoryi Argonaute, is a must-read for genome editing folks. Their team sums up the new method’s potential pluses this way (emphasis mine):

“The useful features of NgAgo for genome editing include the following. First, it has a low tolerance to guide–target mismatch. A single nucleotide mismatch at each position of the gDNA impaired the cleavage efficiency of NgAgo, and mismatches at three positions completely blocked cleavage in our experiments. Second, 5′ phosphorylated short ssDNAs are rare in mammalian cells, which minimizes the possibility of cellular oligonucleotides misguiding NgAgo. Third, NgAgo follows a ‘one-guide-faithful’ rule, that is, a guide can only be loaded when NgAgo protein is in the process of expression, and, once loaded, NgAgo cannot swap its gDNA with other free ssDNA at 37 °C. All of these features could minimize off-target effects. Finally, it is easy to design and synthesize ssDNAs and to adjust their concentration, which is difficult with the Cas9-sgRNA system, if the sgRNA is expressed from a plasmid and the normal dosage of an ssDNA guide is only ~1/10 of that of a sgRNA expression plasmid.

This might be a more orderly way and perhaps even simpler way to go about genome editing than CRISPR, but the jury is still out on that until there are more papers and data. The NgAgo edit efficiency at this preliminary stage of technology development seems very strong (see Figure 5 from the paper above).

NgAgo is a nifty new kid on the block for genome editing so let’s see what more we learn about it in coming months via the almost certain flood of additional papers that tell us more about it.

Hat tip to my colleague Dave Segal on the NgAgo paper.

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