Development of a Blood Test to Assess Fibrillin Fragmentation in the Marfan Syndrome
By Lynn Sakai, Ph.D., Shriners Hospital for Children, Portland, OR
My laboratory at Shriners Hospital for Children, Portland, OR, has been working on the development of a simple test, different from DNA analysis, to aid in the diagnosis and management of the Marfan syndrome. Our studies have suggested that, in the Marfan syndrome, most mutations in the fibrillin-1 gene result in breakdown or loss of fibrillin fibrils in skin and a failure to assemble fibrillin fibrils in cell culture. We have devised a test (called a sandwich ELISA) that will help us to determine whether fibrillin-1 mutations compromise the stability of fibrillin fibrils or interfere with the assembly of fibrils.
The sandwich ELISA is a specific test to determine the presence and concentration of fibrillin-1 fragments in various liquid samples. Samples of bodily fluids, such as blood, or samples from cells in culture can be used. This assay is enabling us to study the differences between how cells from individuals with the Marfan syndrome and cells from unaffected individuals assemble fibrillin-1 into fibrils.
In addition, we are using the sandwich ELISA to test our hypothesis that disease progression in the Marfan syndrome is due to breakdown of fibrillin-1 by enzymes called proteases. We are testing blood samples from people with the Marfan syndrome and from unaffected individuals to determine whether fragments of fibrillin-1 are present. Normally, connective tissue proteins, including fibrillin, form the structures (fibrils) that serve as the body's framework, designed to hold us together for life. Therefore, fragments of fibrillin should not be present in bodily fluids, unless a disease process is occurring that breaks the fibrillin into pieces, which are then released into bodily fluids.
We have hypothesized that a mutation in the fibrillin-1 gene creates a weak point within the fibrillin-1 molecule. This weakened area may be attacked by proteases that then break fibrillin-1 into pieces. By testing blood samples, we can compare the amounts of fibrillin-1 fragments in persons with severe and mild Marfan syndrome with other persons with other types of cardiovascular diseases and with control groups of healthy people. We can also test how the amounts of fibrillin-1 fragments in the blood may change during an individual's lifetime.
By collecting lots of data from the sandwich ELISAs, we may be able to determine in the future whether certain levels of fibrillin-1 fragments correlate with the progression of aortic disease. If this proves to be true, a blood test may be a useful addition to the multi-faceted clinical exam that is currently required for diagnosis and management of the Marfan syndrome.
Current Status
Our work in this area has just begun. We have developed the test and we are trying it out, benefiting greatly from the volunteers of the Oregon Chapter of the National Marfan Foundation. With our clinical collaborator, Dr. Susan Hayflick, a geneticist at Oregon Health and Science University, we have much to do and many results to analyze before we know whether our blood test can contribute to clinical care for individuals with the Marfan syndrome. Our hope is that this line of research will now direct us toward finding and inhibiting the destructive proteases that may be playing significant roles in the progression of disease in the Marfan syndrome. If we can identify and inhibit these proteases, new medicines based upon these inhibitors may be developed, and we may take another important step toward curing the Marfan syndrome.
Our hope is that this line of research will now direct us toward finding and inhibiting the destructive proteases that may be playing significant roles in the progression of disease in the Marfan syndrome. If we can identify and inhibit these proteases, new medicines based upon these inhibitors may be developed, and we may take another important step toward curing the Marfan syndrome.
Lynn Y. Sakai, Ph.D.
Associate Professor of Biochemistry and Molecular Biology
Oregon Health Sciences University and Shriners Hospital for Children
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