Additional studies of mice hypomorphic for fibrillin-1 or heterozygous for a structural fibrillin-1 mutation (Fbn1mgR/mgR mice and Fbn1C1041G/+ mice, respectively) correlated aneurysm progression with improper stimulation of angiotensin II (AngII) type 1 receptor (At1r) signaling [6,7]. The gene discussed is AGTR1; the disease is aneurysm.