Activation of the Wnt/β-catenin and retinoic acid signaling pathways in the Fgf15 mutants. (a-d) Retinoic acid pathway activation was determined at E12.5 (a, b) and E14.5 (c, d) by β-galactosidase staining of coronal sections of Fgf15-/-; RL+ embryos (RL, RARE LacZ, retinoic acid reporter). (e-h) The Wnt/β-catenin pathway activation was revealed by β-galactosidase staining of coronal sections of Fgf15-/-; BG+ (BG, BATgal, Wnt/β-catenin reporter) at E12.5 (e, f) and E14.5 (g, h). Arrows indicate the regions that show the largest changes in the extent and/or intensity of expression. Three separate cases were analyzed for each genotype. Bar in (a, c) is 200 μm.