TRF2 protein crucial for muscle regeneration, Penn study finds
Researchers at the University of Pennsylvania's Perelman School of Medicine have discovered that the protein TRF2, previously known for protecting chromosome ends, is essential for muscle stem cells to maintain their identity and repair injured tissue. Without it, damaged muscle fills with fat and scar tissue.
A protein long associated with safeguarding chromosome ends also plays an unexpected part in keeping muscle stem cells functional, according to a new study from the Perelman School of Medicine at the University of Pennsylvania. Published in Science Advances, the research shows that TRF2 does far more than shield telomeres — it helps preserve the genetic programming that lets muscle stem cells regenerate damaged tissue.
Muscle stem cells usually stay inactive until an injury occurs, then activate, multiply, rebuild the affected area, and some return to a resting state. The scientists observed that TRF2 levels rise and fall in a carefully timed sequence as cells move through those stages, suggesting the protein helps coordinate the repair process. To test its role, the team removed TRF2 from muscle stem cells in mice. Initially, the muscles looked normal, but the stem cell population gradually shrank. The cells did not die, which was surprising given TRF2 loss in other tissues; instead, they lost the molecular characteristics that define muscle stem cells. After injury, the damaged regions accumulated fat and scar tissue rather than healthy muscle.
“This completely changes how we think about TRF2's role in these cells,” said senior author Foteini Mourkioti, an associate professor of Orthopedic Surgery at Penn Medicine. “The loss of identity has severe implications for whether recovery from injury is even possible.”
The team also studied a mouse model of Duchenne muscular dystrophy. When TRF2 was removed, the disease advanced much more rapidly, with more severe muscle deterioration and shorter lifespans. Further experiments revealed that TRF2 does not work only at chromosome ends. It also binds to regulatory regions throughout the genome that control genes needed to preserve muscle stem cell identity. Many of these regions contain secondary DNA structures called G-quadruplexes, which are also being explored as targets for cancer therapies.
The findings may help address a long-standing puzzle: skeletal muscle regenerates exceptionally well, yet muscle-origin cancers are rare. Understanding how muscle stem cells use TRF2 differently could eventually allow researchers to promote tissue repair without increasing cancer risk. Mourkioti and colleagues are now investigating whether this unusual TRF2 function could lead to new treatments for muscular dystrophy and provide insights into cancer biology in more vulnerable tissues. The research received support from the National Institutes of Health and the National Institute of Arthritis and Musculoskeletal and Skin Diseases.
