"Gene Magic Scissors" is safer and more effective in editing genes

10 years ago, we saw a breakthrough
in modern biology.

An American scientist discovered that the manipulation of the Cas9 protein has produced a genetic technology that can almost be shown in science fiction movies: CRISPR
.
Think of it as a pair of "molecular scissors" capable of cutting and editing the DNA
of humans, animals, plants, bacteria, and even viruses.
Its potential and versatility range from the elimination of genetic diseases to the creation
of crops that are resilient to climate change.

However, like any other new technology, CRISPR faces challenges
.
One of the main challenges is how to make the technology as effective as possible and ensure that the "scissors" only cut
where they are wanted.

Describe the new mechanisms behind CRISPR

New research by researchers from the University of Copenhagen and Aarhus University in Denmark may address these issues
.

The researchers say they have been able to describe the mechanism
behind CRISPR.
"We are now able to explain why some off-target, accidental cuts elsewhere in the genome, are more effective
than cuts at predetermined locations.
" We also learned how different DNA sequences around the target affect the efficiency with
which the Cas9 protein cuts DNA.
This knowledge will pave the way
for more effective and safer use of CRISPR.
”

So how does CRISPR work? First, scientists will design a piece of guide RNA and then attach it to the Cas9 protein, which will perform the task
of cutting DNA.
Guide RNA to find matching parts of
DNA.
Once it finds the right place, Cas9 cuts the DNA strand
.
Now, scientists are able to insert any synthetic piece of DNA into the vacated spot
.

Today, CRISPR is mostly used in a medical context to study how genes and drugs work in the laboratory, but it is still not widely used in human treatment
.
In the long term, however, scientists still aim to use CRISPR to treat genetic diseases
in humans.

Effectively solve the mystery of off-target

In a new study described above, researchers sought to determine the best way to direct RNA attachment to DNA to make the cutting as efficient as possible
.
Because if the cutting is not effective enough, scientists will not be able to edit DNA
.

Studies have found that CRISPR doesn't work when the bond between the guide RNA and DNA is too weak, but neither does the bond that is too strong
.

The researchers then determined that the spacing between the guiding RNA and the DNA was neither too strong nor too weak, just enough to give the scissors the perfect sharpness
.
"Interestingly, this observation could also be used to explain why some off-target objects showed stronger CRISPR activity than their intended targets, i.
e.
why 'scissors' were sharper
on some off-targets than on targets.
"

The study also identified the optimal location of the Cas9 protein to achieve the most efficient cleavage
.
Before Cas9 can cut DNA, the protein must bind
to a specific part of the DNA strand.
DNA is composed of 4 different nucleotides: A, C, G, and T, and Cas9 can only bind
to sequences with two consecutive G nucleotides.

The team determined the effects
of multiple consecutive G nucleotides on Cas9.
It's hard to hit the target in this case, as every two successive Gs compete to combine
with Cas9.

This new knowledge about how CRISPR works will make it easier for scientists to identify the right place for Cas9 and help minimize side effects
.

At the same time, there is a promise for accurate prediction of cuts, improved target editing, and elimination of off-target in the future, which complicates the development of new drugs
.

Off target can also be harmful

Another study by the team focused on off-target
.

To perform quality control on CRISPR experiments, scientists typically select a small number of computer-predicted off-target tests
.
Using the new technology, however, they were able to test more off-target, which would help develop new drugs
with fewer side effects.

In the experiment, the researchers tested 8,000 potential off-target
110 CRISPR-guided RNAs.
They found that about 10 percent of the 8,000 potential targets were actually off-target
.
There are many
more newly discovered off-target targets than with existing methods.

They also found that 37 of these off-target genes were located in cancer-related genes, and the side effects of accidental cutting of these genes could even lead to cancer
.

Therefore, one must identify this off-target
more.

The researchers say existing gene-editing studies often lack complete tools and analysis to prove that there are no off-target effects
in these studies.
The new method allows for a better examination of this and will have a significant impact
in the future.

They say that in the past 10 years, people have taken a big step
forward in editing genomes.
Now, people are making the technology better, safer, and more effective
.
The new approach could also support the green transition, as genomic modifications, such as those used in cells, could make resource use more cost-effective
.

Both studies were published in
Nature Communications.