A CRISPR alternative to edit genes without cutting



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Scientists who want to use CRISPR-Cas9 gene editing technology to treat a variety of diseases face the well-known challenge of cutting DNA, which can lead to errors. Scientists at Columbia University's College of Physicians and Surgeons Vagelos are now proposing an alternative system of gene editing, a system that completely eliminates the need to cut DNA.

Researchers use a "jumper gene," or transposon, derived from a bacterium called Vibrio cholerae. The transposon is able to insert into different regions of the genome and can be programmed to transport any DNA sequence to any site. That's why their technology, dubbed INTEGRATE, acts less like a molecular chisel than as a molecular glue, they explained in the journal Nature.

"Rather than introducing DNA breaks and relying on the cell to repair them, INTEGRATE directly inserts a user-defined DNA sequence at a specific location in the genome, a capability sought for decades by molecular biologists, "said lead author Sam Sternberg. Ph.D., assistant professor of biochemistry and molecular biophysics in Columbia, in a statement. Sternberg recently joined Columbia after a stay in the laboratory of Jennifer Doudna, a CRISPR pioneer, at the University of California at Berkeley.

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Since CRISPR is a natural process in bacteria, the Sternberg team decided to look for other gene editing systems in V. cholerae. They discovered that the jumping gene uses an enzyme to slip into the genome rather than cut off the DNA. They then created a gene editing system that combines this ability to integrate with a DNA payload and an RNA guide to help the tool find the right place to insert the gene. # 39; edit.

From there, they sequenced the modified bacteria to confirm that the changes had been made correctly and that there was no copy of the DNA payloads inserted into unintentional sites.

RELATED: Fred Hutchinson's team uses gold nanoparticles to improve gene editing CRISPR

Despite the well-known concerns about CRISPR, the enthusiasm for technology has not wavered. In fact, last week Vertex Pharmaceuticals agreed to pay $ 420 million to acquire Exonics and expand its partnership with CRISPR Therapeutics. The agreement puts in place a CRISPR utilization plan for the treatment of Duchenne muscular dystrophy and myotonic dystrophy type 1.

Nevertheless, university labs around the world are pursuing numerous projects aimed at making gene editing safer. In May, a team at the Fred Hutchinson Cancer Research Center described a method developed for the use of gold nanoparticles to carry CRISPR components in cells and for the use of the enzyme Cas12a to perform sharper cuts than Cas9. GenEdit, a fallout from UC, in Berkeley, is also developing a CRISPR system based on gold.

Other ideas recently proposed to improve CRISPR include fixing a hairpin guide on RNA to improve the precision of DNA sections and adding an on-off switch to Cas9 enzymes. to prevent changes made elsewhere than on the targeted sites.

The next step for the Sternberg team in Columbia is to test INTEGRATE technology in mammalian cells. They believe that the technique could possibly be applied to a variety of products, such as gene therapies and modified cultures.

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