Fig. 3. Aberrant hair follicle development and global expression of placode and hair shaft markers in activated β-catenin mutant embryos. (A-J) Histological analysis of dorsal skin from control littermate and KRT14-Cre Ctnnb1^(Ex3)fl/+ mutant embryos reveals the failure of hair follicle downgrowth in mutants. Mutant skin displays evaginations (B,D,J; arrows) and fails to stratify normally (H; arrow). (G,H) Higher magnification views of E and F, respectively. (K-X) The placode marker Shh (in situ hybridization, brown; K,L) and the dermal condensate marker alkaline phosphatase (AP; enzymatic assay, purple brown; M,N) are expressed broadly in the mutant. Expression of the inner root sheath marker GATA3 (O,P) and the outer root sheath marker SOX9 (Q,R; immunofluorescence, red) is reduced or absent, but hair shaft keratins (AE13 antibody, immunohistochemistry, brown) are ectopically expressed in mutant ectoderm (S,T). Proliferation is decreased (U,V; Ki67 immunofluorescence, red) and the pattern of apoptosis/terminal differentiation is altered (W,X; TUNEL staining, green) in mutant ectoderm. Arrows indicate expression; dashed lines mark dermal-epidermal boundaries. Samples were E17.5 (K-N,Q-X) or newborn (O,P). Scale bars: bar in F applies to A-F; in H, to G,H; in J, to I,J; in X, to K-X.