Nanobodies could help CRISPR turn genes on and off

The CRISPR genetic tool has been compared to molecular scissors for its ability to extract and replace genetic code in DNA. But CRISPR has a capacity that could make it useful beyond genetic repairs. “CRISPR can precisely locate specific genes,” says Lacramioara Bintu, assistant professor of bioengineering at Stanford. “What we did was attach CRISPR to nanobodies to help it perform specific actions when it hits the right spot on the DNA.”

His lab recently used this combined technique to transform CRISPR from a gene-editing scissor into a nanoscale control agent that can turn specific genes on and off, like a light switch, to start or stop. the flow of certain health-related proteins within a cell. .

“There are a lot of things you can’t fix with scissors,” Bintu says. The new technique that his team describes in the newspaper Nature communications could allow researchers to explore new therapeutic applications in the field of epigenetics, which is the study of the behavior of genes inside cells.

As Bintu explains, every cell in the human body has the same DNA – a complete complement of genes – but not all genes are turned on in every cell. Some cells have certain genes, which tell the cell to make specific proteins. Others have these genes turned off, but others are turned on. Sometimes, like with genetic diseases, things go wrong with this change. The new tool from the Bintu lab has the potential to correct these errors.

The new tool is more complicated than scissors because ordinary CRISPR cannot turn genes on and off in a controlled manner without breaking down DNA. To make changes without harming DNA, CRISPR needs the help of other large, complex proteins called “effectors.” With the new combo tool, CRISPR finds the right gene and the effector can flip the switch.

“But these effector molecules are usually too large to be easily delivered into a cell for therapeutic purposes,” says Ph.D. student Mike Van, the paper’s first author. To complicate matters further, multiple effectors are typically used in combination to efficiently regulate specific cellular behaviors, making the CRISPR-effector combo even larger, thus more difficult to produce and deliver.

To get around this roadblock, Bintu’s team turned to smaller proteins called nanobodies. Nanobodies do not act as replacements for effectors. Instead, they act like tiny hooks that trap the necessary effectors that are already swimming in the cell. Pick the right nanbody and it will recruit the right effector for the switching job.

The new technique could be used to correct epigenetic defects without the need to combine CRISPR with large effectors. “Cells already have these proteins,” says Bintu. “We thought, why reattach them? Let’s use nanobodies to do this.”

At this point, the technique is in the proof-of-concept stage. The next step is for the team to sort through millions of potential nanobodies and begin to determine how to attach them to CRISPR to target specific epigenetic degradations.

“We’ve just come up with a method that can test hundreds of thousands of people at a time,” says Bintu, who hopes to develop the technique further in future experiments.

Provided by Stanford University School of Engineering