Apparently, this is pretty big: https://www.nature.com/articles/s41586-019-1711-4
“ Okay, Science time.
A paper just came out yesterday in the scientific journal, Nature, and the entire biotech world is completely freaking out with excitement about it. I stayed up way too late last night reading it myself and I can't stop thinking about it now. Let me tell you about it.
You might have heard of CRISPR-Cas9. Discovered in bacteria, where it functions as an antiviral immune system, Cas9 is a programmable DNA scissors which takes an RNA barcode, scans DNA, and cuts wherever it finds a perfect match. Biological science has long aspired to the ability to make virtually any targeted change in the genome of any living cell or organism, and with CRISPR, the ability to precisely cut any region of DNA we want has opened up so many possibilities, it's no stretch to say that it ignited a revolution and sparked a whole new era in biology today.
One limitation of CRISPR is that on its own, breaking DNA is all it does. If we want to disable something, it's great- cells have an internal mechanism for quickly patching DNA breaks back together, which often disables the particular gene there by introducing small mutations at the seam.
But if we don't want to just break things, if we want to edit or insert or delete a specific thing, we need to add a second component: a DNA donor template that mostly matches the target site but contains the modifications that we want. Then, when the cell repairs the break, we hope that instead of mashing the ends together willy nilly, it uses the other DNA repair mechanism it has, which grabs the ends, seeks out similar-looking DNA, and uses that as a template for repair. Not only is this mechanism rare and slow, we also need to be lucky enough that a copy of our donor template happens to be close by.
In the lab, this limitation isn't a problem: we can blast a million cells, sort through them individually cell by cell, pick out the rare ones that perfectly integrated our template, and just grow those. But breaking the DNA at 90% of the cells to get that rare 10% of cells to accept our specific mutation has obvious limitations, and the ratios are usually even worse than that.
Here's where this paper comes in. Anzalone et. al. from the Broad Institute (pronounced Brode) took CRISPR and modified it into something they call CRISPR PRIME.
Their paper is titled, "Search and Replace Genome Editing Without Double-Strand Breaks or Donor DNA".
They started with a modified CRISPR that cuts only one strand, creating single-strand nicks instead of double-strand breaks. They took the RNA barcode, which programs CRISPR to recognize specific DNA sequences for cutting, and they added an extra long RNA tail to it containing the desired mutation. Finally, they welded another protein, Reverse Transcriptase, to CRISPR, which reads RNA and creates DNA strands from it.
They envisioned a system where instead of introducing our donor separately and hoping the cell happens to use it after CRISPR breaks the site, CRISPR carries the donor with it, gently nicks the site and immediately writes the patch in itself.
And IT WORKS.
From the paper: "We performed more than 175 edits in human cells including targeted insertions, deletions, and all 12 types of point mutations... We applied prime editing in human cells to correct efficiently and with few byproducts the primary genetic causes of sickle cell disease and Tay-Sachs disease, to install a protective transversion in PRNP, and to insert various tags and epitopes precisely into target loci... Prime editing substantially expands the scope and capabilities of genome editing, and in principle could correct about 89% of known pathogenic human variants".
They're releasing this system free to everyone for academic and research use and I need need NEED to try it out myself. I don't think it's a stretch to say that CRISPR prime will be a revolution in how biologists do gene editing, and the entire field agrees.
This is seriously amazing work.”
Dr Zi Teng Wang