Harvard’s Wyss Institute has created a new gene-editing tool that enable scientist to perform millions of genetic experiments simultaneously.

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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.

However, 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.

While the CRISPR-Cas9 gene editing system has become the poster child for innovation in synthetic biology, it has some major limitations. CRISPR-Cas9 can be programmed to find and cut specific pieces of DNA, but editing the DNA to create desired mutations requires tricking the cell into using a new piece of DNA to repair the break. This bait-and-switch can be complicated to orchestrate, and can even be toxic to cells because Cas9 often cuts unintended, off-target sites as well.

Alternative gene editing techniques called recombineering instead perform this bait-and-switch by introducing an alternate piece of DNA while a cell is replicating its genome, efficiently creating genetic mutations without breaking DNA. These methods are simple enough that they can be used in many cells at once to create complex pools of mutations for researchers to study. Figuring out what the effects of those mutations are, however, requires that each mutant be isolated, sequenced, and characterized: a time-consuming and impractical task.

Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University and Harvard Medical School (HMS) have created a new gene editing tool called Retron Library Recombineering (RLR) that makes this task easier. RLR generates up to millions of mutations simultaneously, and “barcodes” mutant cells so that the entire pool can be screened at once, enabling massive amounts of data to be easily generated and analyzed. The achievement, which has been accomplished in bacterial cells, is described in a recent paper in PNAS.

New, reversible CRISPR method can control gene expression while leaving underlying DNA sequence unchanged.

Over the past decade, the CRISPR-Cas9 gene editing system has revolutionized genetic engineering, allowing scientists to make targeted changes to organisms’ DNA. While the system could potentially be useful in treating a variety of diseases, CRISPR-Cas9 editing involves cutting DNA strands, leading to permanent changes to the cell’s genetic material.

Now, in a paper published online in Cell on April 9, researchers describe a new gene editing technology called CRISPRoff that allows researchers to control gene expression with high specificity while leaving the sequence of the DNA unchanged. Designed by Whitehead Institute Member Jonathan Weissman, University of California San Francisco assistant professor Luke Gilbert, Weissman lab postdoc James Nuñez and collaborators, the method is stable enough to be inherited through hundreds of cell divisions, and is also fully reversible.