Fibrillin-1 is a protein that in humans is encoded by the FBN1gene, located on chromosome 15.
FBN1 is a 230-kb gene with 65 coding exons that encode a 2,871-amino-acid long proprotein called profibrillin which is proteolytically cleaved near its C-terminus by the enzyme furin convertase to give fibrillin-1, a member of the fibrillin family, and the 140-amino-acid long protein hormone asprosin.
Fibrillin-1 is a large, extracellular matrix glycoprotein that serves as a structural component of 10-12 nm calcium-binding microfibrils. These microfibrils provide force bearing structural support in elastic and nonelastic connective tissue throughout the body.
The FBN-1 gene is involved in a variety of embryonic developmental programs. The microfibrils that are made from fibrillin-1 contribute to both elastic and non-elastic structures. The formation of the elastic fibers in the heart valves and the aorta require the involvement of both FBN-1 and FBN-2. It has been shown that both FBN-1 and FBN-2, along with the other components of elastic fibers, are expressed in the embryonic semilunar valves as early as 4 weeks of gestation. These molecules interact to form the elastic fibers in the ventricularis layer of the semilunar valves. Fibrillin-1 and fibrillin-2 are also crucial for the development of elastic fibers in the aorta. While expression of fibrillin-2 decreases significantly after fetal development, the expression of fibrillin-1 continues into adulthood. This supports the idea that fibrilin-2 dictates the development of early elastic fibers, while fibrillin-1 provides the structural support of mature elastic fibers.
When mutations in the FBN-1 or FBN-2 genes occur, significant deformations can result from the damage to the extracellular matrix. Marfan Syndrome is a congenital disease that arises from a mutation in the FBN-1 gene. This leads to the malformation and subsequent weakening of the microfibrils in the patient’s body, including the structures of the cardiovascular system. The weakened elastic fibers will result in an impaired durability and distensibility in the heart valves and aorta. This provides the explanation for the aortic aneurysms and prolapsed valves that are commonly associated with Marfan Syndrome.
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