FBN1 and Marfan syndrome: Both FBN1, which encodes fibrillin-1 and is associated with Marfan syndrome, and ELN, which encodes elastin and is associated with the cutis-laxa syndrome gene, are known for their importance in syndromic thoracic aneurysms.53, 54, 55, 56, 57 The COL6A3 gene encodes the alpha-3 chain of type VI collagen and to date there are no studies which describe a role in AAo anatomy or function.