With the discovery of dysregulated TGF-β signaling in Fbn1 knockout mice, the TGF-β pathway was revealed as a key player in the pathogenesis of thoracic aortic aneurysm development in Marfan syndrome (MFS; [Mendelian Inheritance in Man (MIM) 154700]) 2, 3. This evidence concerns the gene FBN1 and Marfan syndrome.