Histologic analysis reveals altered vessel wall architecture in magp1 morphant embryos. Elastin (van Gieson) stain was conducted on fixed sections from 48-hour wild-type and MO–injected embryos. Compared with wild-type embryos (A), magp1 MO–injected embryos (B) showed reduced elastin stain around the vasculature (arrowheads) in the intersomitic region and the connective tissues attached to the dorsal neural tube (arrows). Hematoxylin and eosin staining was performed at 40 hours after fertilization to assess vessel wall structure in magp1 morphant embryos. Compared with wild-type embryos (C, inset in the bottom panel), the vascular cells in the magp1 morphant embryos show a loose association with the surrounding tissue. Cells detaching from the underlying tissue can be observed (D, arrowheads in the inset, bottom panel). Original magnification 20 ×. Bottom panels of C and D are enlarged versions of the boxed sections of the top panels.