F-actin cables at ephrin-B1 boundaries in the embryo. Sections through the palates of control (Efnb1^lox/+) and heterozygous (Efnb1^Δ/+) embryos stained for ephrin-B1 (green) and F-actin (phalloidin; magenta). An ephrin-B1 expression boundary is indicated by white arrowheads. Numbers of embryos analyzed are presented in Table S2. Bars, 50 µm.