Overexpression of wild-type and mutant RGMa perturbs morphogenesis in neurulating Xenopus embryos. (A to D) Unilateral overexpression of FL-RGMa induces severe defects in developing Xenopus embryos by neurulation stages 19 to 21. Panels A′ to D′ show fluorescent images of the same embryos shown in panels A to D, respectively. (A) Control EGFP-injected embryo. (B to D) Unilateral overexpression of RGMa causes neurulation phenotypes. RGMa-overexpressing embryos showed the ring embryo phenotype (B and C) or an underdeveloped neural tube (D). Arrows in panels B to D indicate prominent abnormalities. (E and F) Penetration of neurulation (E) and endoderm-exposing ring (F) phenotypes from control, FL-RGMa, RGMa-ΔvWF, and RGMa-ΔRGD embryos. Bar, 300 μm. ***, P < 0.001; **, P < 0.01; *, P < 0.05.