Fig. 5.

Epithelial HS modulates Fgf signaling activity in embryonic stomach. (A) Representative image of western blot of p-Erk shows a reduction in its protein level. Graph shows the quantification of band intensity from three independent western blots. C, control; M, mutant (n=3). (B) p-Erk signals are absent in mutant glandular epithelium. Asterisks indicate epithelium. (C) Analysis of Fgf signaling targets. qPCR shows decreased expression of Etv4, Etv5 and Spry1 in mutant stomach in spite of elevated Fgf10 mRNA level (n=5 per group). (D) LACE staining of Fgf10 and Fgfr2b in forestomach and hindstomach. Strong signals near the basement membrane, as well as in the epithelial cells both in the forestomach and hindstomach are detected in the control, which is rarely observed in the mutant. Magnified views of the boxed areas are shown in the insets. (E,F) Fgfr inhibitor (SU5402) treatment leads to enhanced Sox2 expression in a concentration-dependent manner shown by ISH and immunostaining. Organ culture experiments were performed independently three times (n=6 under each control condition; n=2 for mutant). fs, forestomach; hs, hindstomach. The dashed lines outline the gastric epithelium. **P<0.05 and *P<0.01. Error bars indicate s.e.m. Scale bars: 50 μm.