Marfan syndrome is a connective tissue disorder caused by mutations in FBN1, and the most severe clinical manifestations include aortic aneurysms and dissections22.Thoracic aortas of Marfan mice exhibited a reduction of 64 to 81% reduced contraction upon KCl and phenylephrine compared to age matched control mice23. Here, FBN1 is linked to aortic aneurysm.