FBN1 and Marfan syndrome: For example, mutations in FBN1 (an extracellular glycoprotein of the ECM that acts to maintain tissue elasticity of the valve leaflets and aortic wall by linking smooth muscle cells to adjacent elastin fibrils) have been observed in patients with Marfan syndrome (MFS), a genetic disorder of the connective tissue characterized by mitral valve prolapse, BAV, and/or aortic dissection and aneurysm [28–30].