Thread by @Biotech2k1

Looking at $BEAM the technology:

This will be a look at the underlying technology of base editing. I plan another guide for the science and maybe another for the corporate.

1/ They are using base editing technology. This takes the CRISPR CAS9 enzyme along with the guide RNA attached to a deaminase enzyme to make a modification to a single base of the DNA.

2/ The guide RNA looks for a photospacer sequence in the DNA. That is just a matching sequence of DNA that matches the guide RNA. Next to the photospacer sequence will the the Photospacer adjacent motif (PAM).

3/ Once the guide RNA is lined up with the phtotospacer, the demainase will react with the correct bases inside the 4 to 5 base pair editing window. If more then one A or C appear in the editing window, the deaminase can't determine one from the other.

4/ It will change one of them randomly. This can end up with what is called by-stander edits. They have to screen these possible by-stander edits to ensure they won't cause any problems.

5/ Base editing comes in two forms. There is the Adenine Base Editor (ABE) that removes the amino group from the A base and its read as an inosine that gets read as a G.

6/ The other base editor called the Cytosine Base Editor (CBE) that removes the amino group from the C which is read as a Uracil.

7/ There is an enzyme responsible for finding and repairing deamination events. This enzyme is called Uracil DNA Glycosylase (UNG). To get around this they must include a Uracil Glyclosylase Inhibitor (UGI).

8/ Once the base is modified, the nickase of the CAS enzyme cuts the opposite strand so that base pair miss match will get corrected using the edited strand as the template.

9/ The benefits of base editing is it gets away form double stranded breaks and None Homologous End Joining which is a very inaccurate repair mechanism.

10/ This prevents the possibility of Insertion or Deletions (Indels) of any extra bases. These can cause frame shifts which will lead to a mutation of the protein for that gene.

11/ Base editing is capable of base modification and correction. Its capable of gene silencing and activation. Its not capable of gene insertion which is its limitation.

12/ To ensure the broadest use of their base editing technology, they are embracing the use of a wide range of delivery methods. This includes electroporation for ex-vivo delivery, LNP for non viral delivery and AAV vectors for delivery into the eye and CNS.