Depletion of XWGEF suppressed CE movements. (A, B) XWGEF–MO suppressed axis elongation. Sixty nanograms of control MO (CtlMO) (A) or XWGEF–MO (B) were injected into dorsal blastomeres at the four-cell stage. XWGEF–MO-injected embryos showed shortened axis (58/62 embryos), whereas CtlMO-injected embryos did not shows shortened axis (0/57). (C–J) XWGEF–MO suppressed elongation of the notochord, but did not inhibit mesodermal marker expression. Sixty nanograms of CtlMO (C–F) or XWGEF–MO (G–J) were injected into dorsal blastomeres at the four-cell stage together with lacZ RNA to mark the site of injection (red). WISH is shown for Xbra (C, G), Xnot (D, H), Chd (E, I), and Otx-2 (F, J) at stage 13. (K, L) Keller sandwich explants from MO-injected embryos. Two dorsal sectors were dissected from stage-10 embryos and combined with each other. Explants injected with 60 ng of CtlMO extended (K, 42/50), whereas explants injected with 60 ng of XWGEF–MO did not extend (L, 4/41). The difference is statistically significant (P=3 × E−13; ). (M–T) XWGEF–MO inhibited CE in activin-treated animal caps, and this inhibition was rescued by expression of hWGEF, CARhoA or Rok. MOs with or without mRNA were injected into the animal region at the four-cell stage. Animal caps were dissected at stage 9, treated with activin for 3 h and photographed when sibling embryos reached stage 20. No elongation was seen without activin (M, 0/70 explants elongated), but elongation was induced by activin in uninjected (N, 73/77) or CtlMO-injected (60 ng) explants (O, 62/65). Injection of XWGEF–MO (60 ng) inhibited elongation (P, 7/80 elongated), which was rescued by co-injection of 1 or 2 pg of hWGEF mRNA (Q, 43/83), 1 pg of CARhoA mRNA (R, 33/63) or 50 pg of Rok mRNA (T, 19/41), but not CARac1 mRNA (S, 2/61). (U) Bar graph showing the percentage of elongated animal caps in the experiments shown in panels M–T. Standard error bars are shown. Co-injection of WGEF, CARho and Rok mRNA showed statistically significant rescue compared with explants injected with XWGEF–MO alone (P<0.01; ).