How a mini CRISPR Cas9 system is revolutionizing gene therapy!

Hello fellow biotech lovers! In May of this year, you might have heard
the incredible news that researchers from Temple University have, for the first time
in history, successfully removed the AIDS-causing HIV-1 DNA from the genome of living animals! What extraordinary technology made this breakthrough
possible? CRISPR Cas9, of course! But, we’re not talking about Cas9 derived
from Streptococcus pyogenes that usually comes to mind when we think of CRISPR. We’re talking about a more recently discovered
“miniature” Cas9 from staphylococcus aureus identified by MIT’s Zhang team in
collaboration with Harvard University and the National Institute of Health. This little nuclease has big potential to
change the game in biomedical research by making CRISPR-based gene editing in living
organisms that much more feasible! This is Molecular Minutes, bringing you breakthroughs
at breakneck speeds. In this video, we’ll introduce you to saCas9,
a nuclease that’s making waves as a powerful tool in gene therapy and one we’re excited
to say will be available soon, here at Applied Biological Materials. So, what’s the deal with saCas9? According to the original paper, published
in April 2015 in Nature, saCas9 is the only other known Cas9 nuclease that can target and
cleave DNA in vivo with about the same efficiency as spCas9. In fact, there are only two major differences
that set them apart from each other. First, saCas9 has a different PAM sequence
compared to spCas9. And second, saCas9 is about ~1 kb smaller
than spCas9! If you’ve watched our last episode of Molecular
Minutes about the CRISPR Cpf1 system, you’ll know that in gene therapy, great things come
in small packages–packages about the size of the adeno-associated virus, to be exact. Scientists like using AAVs because they are
non-pathogenic, don’t trigger strong immune responses, and allow for tissue-specific infection. But, AAVs are like sports cars–they have
great performance but limited space in the trunk! Because AAVs can only fit 4.5 kb worth of
DNA, spCas9 barely fits–if at all– and definitely doesn’t leave any room for extra baggage such
as regulatory expression elements which is pretty inconvenient. Because saCas9 is only ~3.3 kb, it fits snugly
within the AAV vector and even allows for one or two gRNAs to be included in the same
construct! So, how does saCas9 perform in vivo? In the original Nature paper, the authors
injected AAVs carrying saCas9 into mice to disrupt the PCSK9 gene, a gene linked to high
cholesterol and genetic conditions such as familial hypercholesterolemia. They saw an increase of 40% indel formation
in liver tissue after only 1 week and no signs of toxicity 4 weeks after injection. In the more recent study done by Temple University
scientists, saCas9 was able to remove the HIV-1 DNA inside every tissue of transgenic
mice only 2 weeks after injection. Although it was later found that the HIV molecule
was able to resist these first editing attempts, the idea of using CRISPR to one day eradicate
HIV is one that remains full of potential! In fact, CRISPR-based medicine is so promising
that Editas Medicine, the CRISPR-based therapeutics company founded by Feng Zhang himself, is
already experimenting with saCas9 to discover new treatments for other diseases, such as
Cystic Fibrosis. There may soon be a time when personalized
therapy can be delivered faster than you can say “Search and Destroy”. Eager to get started with saCas9? So are we! That’s why saCas9 will be available at abm
very soon! But, if you want to begin your gene editing
adventures right now, we’ve got an entire portfolio of CRISPR tools at your disposal,
including our new CRISPR Knockout cell lines. So, go knock yourself out! Thanks for watching Molecular Minutes–stay
tuned for more newsflashes as we follow the latest movers and shakers in the biotech industry.

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