The vascular basement membrane functionally regulates aortic diameter and stability. Impaired basement membrane assembly leads to increased aortic diameter and elasticity. (A,B) Quantification of dorsal aorta (A) and posterior cardinal vein (B) diameter in 4 dpf col4a1 morpholino-injected or col4a1st93/st93 mutant animals compared with control wild-type animals. A minimum of four fish were measured per sample, with ten separate dorsal aorta measurements per fish. N.S., not significant. (C-J) Representative transmitted light (C,D) and confocal (E-J) images of 4 dpf control (C,E,G,I), col4a1 morpholino-injected (D,F,H), or col4a1st93 mutant (J) animals, showing lateral views of entire animal (C,D) lateral views of the trunk vasculature (E,F) and higher-magnification lateral images of the dorsal aorta (G-J). Brackets indicate diameter of dorsal aorta. (K,L) Quantification of dorsal aorta elasticity in 4 dpf col4a1 morpholino-injected (K) or col4a1st93 mutant (L) animals compared with control wild-type animals, using SPIM. Data are reported as percentage diameter change. A minimum of four fish were measured per sample, with three separate dorsal aorta measurements made per fish. Scale bars: 50 µm. Values are mean±s.e.m.