Fig. 7. Dependence of spr2 expression on Nodal, Fgf and Wnt signals. (A–F) 50% epiboly stage. (G–L) 75% epiboly stage. (A–I) Animal-pole views with dorsal to the right. (J–L) Lateral views with dorsal to the right. (O and P) Dorsal views. Injection with 1pg sqt or 10 pg of fgf17b mRNA caused ectopic expression of spr2 (B, E, H and K). When injected with 100 pg of lefty1 mRNA, spr2 expression was abolished on the dorsal side and reduced in the ventral germ ring (C). When injected with 100 pg XFD mRNA, spr2 expression was eliminated on the ventral side and dramatically decreased on the dorsal side (F, I and L). A section revealed that spr2 expression on the dorsal of XFD-injected embryos persisted in the epiblast layer only (N). Injection with mouse Axin mRNA led to suppression of spr2 expression on the dorsal side (O), while co-injection with Axin and XFD mRNAs resulted in elimination of spr2 expression in some of the embryos (P).