Somite morphogenesis is sensitive to genetic interaction between itgα5 and ephrinB2a, but not rap1b and ephrinB2a. A-C: Lateral view DIC images showing complete disruption of somite borders in (A) itgα5-/-; ephrinB2a MO embryos (7 experiments, 27.9% affected compared to an expected 25% for homozygotes, n = 605) and proper maintenance of somite borders in (B) ephrinB2a MO + rap1b MO1 (5 experiments, no synergy, n = 455) and (C) ephrinB2a MO + rap1b DN embryos (3 experiments, no synergy). Dorsal (D-F:) and higher magnification dorsal (D′-F′) views of Fibronectin localization for (D-D′) itgα5-/-; ephrinB2a MO, (E-E′) ephrinB2a MO + rap1b MO1, and (F-F′) ephrinB2a MO + rap1b DN embryos at the 12–15-somite stage. FN matrix formation is lost only in itgα5-/-; ephrinB2a MO embryos. For all images, anterior is left.
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