Study shows TALEN is five times more efficient than CRISPR-Cas9 tool

Using single-molecule imaging, scientists have compared the CRISPR-Cas9 and TALEN genome editing tools. According to the researchers’ experiments, TALEN is up to five-fold more effective than CRISPR-Cas9 in segments of the genome, termed heterochromatin, that are packed closely.

The research team included, from left, postdoctoral researcher Saurabh Shukla, graduate student Che Yang, chemical and biomolecular engineering professor Huimin Zhao, physics professor Paul Selvin, postdoctoral researcher Zia Fatma, graduate student Xiong Xiong, and Surbhi Jain, a former doctoral student at the U. of I. who is now a group lead in cancer biology at Northwestern University. Composite image from separate photos, in compliance with COVID-19 safety protocols. Image Credit: Composite photo by L. Brian Stauffer.

Many diseases, including, beta-thalassemia, sickle cell anemia, and fragile X syndrome, are caused by genetic flaws in heterochromatin. The team has reported their latest observations in the Nature Communications journal,

The new study supports the evidence that a wider selection of genome-editing methods is required to target all segments of the genome, stated Huimin Zhao, a professor of chemical and biomolecular engineering from the University of Illinois Urbana-Champaign, who headed the latest study.

CRISPR is a very powerful tool that led to a revolution in genetic engineering. But it still has some limitations.”

Huimin Zhao, Professor of Chemical and Biomolecular Engineering, University of Illinois, Urbana-Champaign

Being a bacterial molecule, CRISPR identifies foreign viruses and can carry one of the many enzymes, like Cas-9, that enable it to cut viral genomes at certain locations. TALEN also screens DNA to identify and target particular genes. Both TALEN and CRISPR tools can be designed to target particular genes to combat disease, enhance the characteristics of plants, or other similar applications.

Along with his collaborators, Zhao utilized single-molecule fluorescence microscopy to immediately visualize how the two genome-editing techniques worked in living mammalian cells. With the help of fluorescent-labeled tags, the team was able to calculate the time taken by TALEN and CRISPR to travel along with the DNA and to identify and cut the target sites.

We found that CRISPR works better in the less-tightly wound regions of the genome, but TALEN can access those genes in the heterochromatin region better than CRISPR. We also saw that TALEN can have higher editing efficiency than CRISPR. It can cut the DNA and then make changes more efficiently than CRISPR.”

Huimin Zhao, Professor of Chemical and Biomolecular Engineering, University of Illinois, Urbana-Champaign

In numerous experiments, Talen was found to be as much as five-fold more effective than CRISPR. These results would lead to better methods for targeting different sections of the genome, added Zhao.

Either we can use TALEN for certain applications, or we could try to make CRISPR work better in the heterochromatin.”

Huimin Zhao, Professor, Chemical and Biomolecular Engineering, University of Illinois, Urbana-Champaign