Fibrillin-1 is a protein that in humans is encoded by the FBN1gene, located on chromosome 15.[5][6] It is a large, extracellular matrixglycoprotein 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. Mutations altering the protein can result in a variety of phenotypic effects differing widely in their severity, including fetal death, developmental problems, Marfan syndrome or in some cases Weill-Marchesani syndrome.