Researchers from the Harvard's Wyss Institute for Biologically Inspired Engineering have created a new gene-editing tool that can enable scientists to perform millions of genetic experiments simultaneously. They're calling it the Retron Library Recombineering (RLR) technique, and it uses segments of bacterial DNA called retrons that can produce fragments of single-stranded DNA.
When it comes to
gene editing, CRISPR-Cas9 is probably the most well-known technique these days.
It's been making waves in the science world in the past few years, giving
researchers the tool they need to be able to easily alter DNA sequences. It's
more accurate than previously used techniques, and it has a wide variety of potential applications, including life-saving treatments for various
illnesses.
owever, the tool has some major
limitations. It could be difficult to deliver CRISPR-Cas9 materials in large
numbers, which remains a problem for studies and experiments, for one. Also,
the way the technique works can be toxic to cells, because the Cas9 enzyme —
the molecular "scissors" in charge of cutting strands of DNA — often
cuts non-target sites as well.
CRISPR-Cas9
physically cuts DNA to incorporate the mutant sequence into its genome during
the repair process. Meanwhile, retrons can introduce the mutant DNA strand into
a replicating cell, so that the strand can become incorporated into the
daughter cells' DNA. Further, retrons' sequences can serve as "barcodes"
or "name tags," allowing scientists to track individuals in a pool of
bacteria. That means they can be used for genome editing without damaging the
native DNA, and they can be used to perform multiple experiments in one big
mixture.
The Wyss Institute
scientists tested RLR on E. coli bacteria and found that 90
percent of the population incorporated the retron sequence after they made a
few tweaks. They were also able to prove how useful it can be in massive
genetic experiments. During their tests, they were able to find antibiotic
resistance mutations in E. coli by sequencing the retrons'
barcodes instead of sequencing individual mutants, making the process a lot
faster.
The study's co-first author Max Schubert,
explained:
"RLR enabled us to do something
that's impossible to do with CRISPR: we randomly chopped up a bacterial genome,
turned those genetic fragments into single-stranded DNA in situ, and used them
to screen millions of sequences simultaneously. RLR is a simpler, more flexible
gene editing tool that can be used for highly multiplexed experiments, which
eliminates the toxicity often observed with CRISPR and improves researchers’
ability to explore mutations at the genome level...
For a long time, CRISPR was just
considered a weird thing that bacteria did, and figuring out how to harness it
for genome engineering changed the world. Retrons are another bacterial
innovation that might also provide some important advances."
There's still work
to be done before RLR can be widely used, including improving and standardizing
its editing rate. The team believes, however, that it can "lead to new,
exciting and unexpected innovations."
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