PHILADELPHIA – Targeted mutations to the genome can now be introduced by splitting specific mutator enzymes and then triggering them to reconstitute, according to research from the Perelman School of Medicine at the University of Pennsylvania. Led by graduate student Kiara Berríos under the supervision of Rahul Kohli, MD, PhD, an associate professor of Infectious Diseases at Penn, and Junwei Shi, PhD, an assistant professor of Cancer Biology, the investigations uncovered a novel gene editing technique that offers superior control compared to other existing techniques and has the potential to be used in-vivo. The technique has been patented, and the research is published in the latest issue of Nature Chemical Biology.
Base editors are one of the latest and most effective ways to achieve precise gene editing. In DNA targeted by base editors, C:G base pairs in DNA can be mutated to T:A or A:T base pairs can be turned to G:C. The base editors use CRISPR-Cas proteins to locate a specific DNA target and DNA deaminase enzymes to modify and mutate the target. Nevertheless, there was no way to trigger mutations at specific times or keep the editor in check to prevent undesired mutations.
The Penn researchers found that DNA deaminases can be divided into two inactive pieces, which can then be put back together using a small cell-permeable molecule called rapamycin. The new split-engineered base editors (seBEs) system can be introduced and lay dormant within a cell until the small molecule is added, at which point the base editing complex can be rapidly “turned on” to alter the genome.
“Our newly created split-engineered base editors really offer new potential for both research and therapeutics,” Kohli said. “Since we can control the time mutations are made, there is a possibility to use these seBEs in vivo to model diseases by altering a gene, similar to how scientists control the timing of gene knockouts, and even potentially someday offer clinicians the ability to control editing of a patient’s genes for treatment purposes.”
“Splitting DNA deaminase can also work outside of base editors,” said Shi. “As a cancer researcher, I see this technique as having potential in controlling genetic changes that cause cancer development and growth. It could also be used to identify vulnerabilities in cancer cells.”
Kohli’s and Shi’s labs plan to build on this research by applying controllable genome editing to cell-based screen research and by adding a layer of spatial control to accompany temporal control. A strength of the researchers’ approach is that the controllable split enzyme system can also be partnered with other new developments in the rapidly expanding CRISPR/Cas field to newly gain regulatory control over these various base editing strategies.
Penn Medicine is one of the world’s leading academic medical centers, dedicated to the related missions of medical education, biomedical research, and excellence in patient care. Penn Medicine consists of the Raymond and Ruth Perelman School of Medicine at the University of Pennsylvania (founded in 1765 as the nation’s first medical school) and the University of Pennsylvania Health System, which together form a $8.9 billion enterprise.
The Perelman School of Medicine has been ranked among the top medical schools in the United States for more than 20 years, according to U.S. News & World Report's survey of research-oriented medical schools. The School is consistently among the nation's top recipients of funding from the National Institutes of Health, with $496 million awarded in the 2020 fiscal year.
The University of Pennsylvania Health System’s patient care facilities include: the Hospital of the University of Pennsylvania and Penn Presbyterian Medical Center—which are recognized as one of the nation’s top “Honor Roll” hospitals by U.S. News & World Report—Chester County Hospital; Lancaster General Health; Penn Medicine Princeton Health; and Pennsylvania Hospital, the nation’s first hospital, founded in 1751. Additional facilities and enterprises include Good Shepherd Penn Partners, Penn Medicine at Home, Lancaster Behavioral Health Hospital, and Princeton House Behavioral Health, among others.
Penn Medicine is powered by a talented and dedicated workforce of more than 44,000 people. The organization also has alliances with top community health systems across both Southeastern Pennsylvania and Southern New Jersey, creating more options for patients no matter where they live.
Penn Medicine is committed to improving lives and health through a variety of community-based programs and activities. In fiscal year 2020, Penn Medicine provided more than $563 million to benefit our community.