Is there a more intriguingly named part of our body than the Zonule of Zinn?
This network of tiny, translucent fibers sits behind the iris, bridging the gap between the lens and the inner wall of the eye. Acting like the springs of a trampoline, these fibers enable the lens to adjust its shape to focus on objects both near and far. Though invisible at a glance, the zonular fibers play an essential role in vision, stretching the lens into a flatter shape to sharpen distant views.
The Zonule of Zinn is named after Johann Zinn, an 18th-century German scientist recognized for his major contributions to anatomy. His legacy extends beyond the eye—he is also the namesake of the zinnia flower. His detailed studies of ocular anatomy resulted in multiple eye structures bearing his name, with the Zonule being among the most well-known.
These fibers are primarily composed of fibrillin, a protein that assembles into long filaments which then bundle together to form strong, elastic fibers—similar to a rubber band. Fibrillin is not exclusive to the eye; it is a crucial component of the body’s connective tissues, including the walls of major blood vessels such as the aorta. This connection between fibrillin and organ systems carries significant medical implications.
Several inherited conditions involve abnormalities in fibrillin-rich fibers, including Marfan syndrome. Individuals with Marfan syndrome face increased risk for aortic rupture and lens dislocation. Researchers in the Bassnett Lab have been investigating Marfan syndrome using mouse models. Because the mouse eye shares key structural similarities with the human eye, scientists can introduce mutations in the fibrillin gene to study how these changes affect zonular fibers and contribute to lens dislocation. These models provide an invaluable platform for testing potential treatments.
In collaboration with St. Louis University of Health Sciences and Pharmacy, Bassnett Lab researchers have measured the biomechanical properties of mutant zonular fibers. Their findings indicate that mutant fibrillin weakens the Zonule, making it more prone to rupture. One hypothesis is that mutant fibrillin is particularly vulnerable to proteolysis, a process in which proteins are broken down.
To investigate further, the Bassnett Lab partnered with researchers at the Cleveland Clinic to map regions of fibrillin most susceptible to cleavage by enzymes in ocular fluid. Identifying these enzymes could lead to targeted inhibitors that help protect the Zonule from breakdown.
This work extends beyond vision science. If protease inhibitors can stabilize fibrillin-rich fibers in the eye, they may also help reinforce blood vessel walls in patients at elevated risk of aneurysms.
About WashU Medicine
WashU Medicine is a global leader in academic medicine, including biomedical research, patient care and educational programs with 2,900 faculty. Its National Institutes of Health (NIH) research funding portfolio is the second largest among U.S. medical schools and has grown 56% in the last seven years. Together with institutional investment, WashU Medicine commits well over $1 billion annually to basic and clinical research innovation and training. Its faculty practice is consistently within the top five in the country, with more than 1,900 faculty physicians practicing at 130 locations and who are also the medical staffs of Barnes-Jewish and St. Louis Children’s hospitals of BJC HealthCare. WashU Medicine has a storied history in MD/PhD training, recently dedicated $100 million to scholarships and curriculum renewal for its medical students, and is home to top-notch training programs in every medical subspecialty as well as physical therapy, occupational therapy, and audiology and communications sciences.