Investigators at Weill Cornell Medicine have developed a versatile and non-toxic technology for controlling the activity of any gene in a cell. Such "gene-switch" tools allow scientists to "turn on" or "turn off" a target gene to study how it works, model diseases and design new therapies. The tool potentially could be adopted throughout biomedical research, including in the development of gene therapies.
The new tool, called Cyclone (acyclovir-controlled poison exon), is described in a paper published Nov. 3 in Nature Methods. The tool was inspired by a natural feature of some genes, a DNA segment called a "poison exon," which under certain conditions can block the gene from being translated into a protein. To make Cyclone, the researchers engineered a poison exon that can be inserted into any target gene to suppress its activity. When the researchers are ready to turn up gene activity, a drug that binds to the poison exon is introduced and activity resumes. Unlike existing popular gene-switch tools, Cyclone uses a relatively non-toxic molecule, the antiviral drug acyclovir, to switch on the target gene.
"We think the Cyclone concept has great potential for diverse applications requiring the safe and precise control of gene activity," said study senior author Dr. Samie Jaffrey , the Greenberg-Starr Professor in the Department of Pharmacology and a member of the Sandra and Edward Meyer Cancer Center at Weill Cornell Medicine.
The study's first author was Qian Hou, a PhD candidate in the Jaffrey Laboratory.
Cyclone is a substantial improvement over existing gene-switch technologies, which have significant drawbacks. For instance, some of the drugs used to control gene expression, like tetracycline, can have unwanted, even toxic effects on cells. Existing tools also often end up modifying RNA transcripts—the blueprints of the protein being produced by the target gene. In contrast, acyclovir is considered safe even at high doses and leaves the RNA transcripts and resulting proteins intact when activating a target gene.
The researchers showed that Cyclone can dial up gene activity from virtually 0% to more than 300% of normal, depending on the acyclovir dose. They demonstrated that the Cyclone system could be used with artificial genes, or the natural ones present in cells and could work with switch molecules other than acyclovir. This raises the possibility of using different Cyclone-type systems to manipulate multiple genes simultaneously.
The researchers noted that in the future Cyclone-type systems could be used in gene therapies as a reversible safety mechanism to control the activity of a therapeutic gene.
Cornell University has filed a patent application covering the Cyclone technology for which Dr. Samie R. Jaffrey and Qian Hou are listed inventors. Dr. Jaffrey is also founder and equity holder in Lucerna Technologies and Chimerna Therapeutics.
This work was supported by the National Institutes of Health grant numbers R35NS111631, S10 OD030335, RM1 HG011563, F31NS139612 and T32 GM115327 Chemistry-Biology Interface Training Grant to the Tri-Institutional PhD Program in Chemical Biology.
