Fig. 2. (A) Soluble recombinant FGFR2b extracellular domain significantly inhibits branching morphogenesis of E13.5 submandibular glands, while rFGFR1b and rFGFR3c have lesser effects (all 10 µg/ml). Taken together, these results suggest that multiple FGFRs are involved in branching morphogenesis. (B) The number of buds was expressed as a ratio of the number of buds at 44 hours/number of buds at 2 hours (T44/T2). At least 5 glands/condition were used for quantitation, and the experiments were repeated at least three times (ANOVA, ^*P<0.05, ^**P<0.01). (C) Hematoxylin and Eosin stained sections show that although rFGFR2b inhibits branching and end bud formation, duct and lumen formation (arrows) still occur. The higher magnification shows duct lumen formation. See Movie 1 in supplementary material of control and rFGFR2b-treated SMGs cultured for 36 hours.