Fig. 5. Rescue of MAPK activity and eomesodermin expression by FGF3 and Xnr1. (A) P-MAPK blot of stage 9.25 extracts: P-MAPK was decreased by dominant-negative XTFC3 mRNA (dnXTCF, 4 × 2 ng mRNA) but could be rescued by co-expression of FGF3 (4 × 10 pg mRNA). Control, uninjected; H₂O, water injected. (B) RT–PCR: expression of eomesodermin at stage 9.25 was strongly inhibited by dnXTCF (4 × 2 ng mRNA). Co-expression of FGF3 (4 × 10 pg mRNA) and Xnr1 (4 × 5 pg mRNA) could rescue normal levels of eomesodermin. FGF3 alone had no effect. Partial rescue was observed with Xnr1 alone, which was completely blocked by dominant-negative FGF receptor (dnFGF-R, 4 × 2 ng mRNA).