Figure 6. EGF specifically antagonizes sFPR-3 effects in Xenopus embryos.

(A) Lateral view of a normal embryo at stage 28/29 NF un-injected. (B) Embryo injected with 4 ng of mouse sFPR-3 mRNA at stage 28/29 NF, showing a remarkable shortened of the trunk and the tail and a reduced muscle differentiation. (C) Rescue of the shortened phenotype by co-injection of 4 ng of sFPR-3 and 8 ng of EGF mouse mRNAs. (D–I) Whole mount immunostaining with 12–101 specific amphibians muscle monoclonal antibody, peroxidase detected. (D) Normal embryo un-injected at stage 35/36 NF, showing black labeling in the trunk and tail muscles and in the parietal muscle (black arrow). (E) Injected embryo with mouse sFPR-3 mRNA at stage 35/36, presenting a shortened trunk and a kinky tail; furthermore the parietal muscles (black arrow) are remarkably reduced. (F) Rescue of the shortened kinky phenotype, showing completely restored muscle differentiation also in the parietal muscle (red arrow). (G–I) High power magnification respectively of D–F, showing in detail the chevron like organization of the tail muscles of un-injected normal larvae (G), missing in the sFRP-3 treated tadpole tail (H) and restored in the co-injected larvae with EGF mouse mRNA (I). (J) Lateral view of a co-injected embryo with 4 ng of sFRP-3 and 8 ng of FGF-8 mouse coding mRNAs, showing no rescue of the sFRP-3 phenotype. (K) Quantization of multiple injections (n = 3) showing the rate of the phenotype rescue by co-injection with 8 ng of EGF mouse mRNA after the injection of sFPR-3 (asterisk indicates statistical significance P<0.001).