In a new study, North Carolina State University researchers characterize a range of molecular tools to rewrite -- not just edit -- large chunks of an organism's DNA, based on CRISPR-Cas systems associated with selfish genetic "hitchhikers" called transposons.

 

The researchers investigate diverse Type I-F CRISPR-Cas systems and engineer them to add genetic cargo -- up to 10,000 additional genetic code letters -- to the transposon's cargo to make desired changes to a bacterium -- in this case, E. coli.

 

The findings expand the CRISPR toolbox and could have significant implications in the manipulation of bacteria and other organisms at a time of need for flexible genome editing in therapeutics, biotechnology and more sustainable and efficient agriculture.

 

Bacteria use CRISPR-Cas as adaptive immune systems to withstand attacks from enemies like viruses. These systems have been adapted by scientists to remove or cut and replace specific genetic code sequences in a variety of organisms. The new finding shows that exponentially larger amounts of genetic code can be moved or added, potentially increasing CRISPR's functionality.

 

"In nature, transposons have co-opted CRISPR systems to, selfishly, move themselves around an organism's genome to help themselves survive. We're in turn co-opting what occurs in nature by integrating with transposons a programmable CRISPR-Cas system that can move around genetic cargo that we design to perform some function," said Rodolphe Barrangou, the Todd R. Klaenhammer Distinguished Professor of Food, Bioprocessing and Nutrition Sciences at NC State and corresponding author of a paper describing the research.

 

"Using this method, we showed that we can engineer genomes by moving chunks of DNA up to 10,000 letters," Barrangou said. "Nature already does this -- the bioinformatic data shows examples of up to 100,000 genetic letters moved around by transposon-based CRISPR systems -- but now we can control and engineer it by using this system.