Hemizygosity of the elastin gene in animals (Eln+/- mice) or humans, e.g., patients with Williams–Beuren syndrome (WBS) or isolated supravalvular aortic stenosis (SVAS), leads to narrower arteries, lower arterial elastin content, degraded, thinner and/or more numerous elastic lamellae, abnormal/stiffened elastic lamellae and large arteries, altered hemodynamics, cardiac hypertrophy and hypertension, as well as, in human patients, large artery stenoses [9,12,14,15,16,17,18,19]. The gene discussed is ELN; the disease is Williams syndrome.