Fig. 9.

Activated β-catenin is dramatically reduced in Sost^–/–; Sostdc1^–/– limbs. Lack of Sost up-regulates WNT signaling as evidenced by increased staining for activated β-catenin in the ectoderm (marked by dashed lines) and underlining mesenchyme (B). Sost^–/– ectoderm also appears thicker than all other genotypes; lack of Sostdc1 has little effect on ectodermal β-catenin (C), but causes a slight reduction in the mesenchyme; removing both Sost and Sostdc1 dramatically reduces both ectodermal and mesenchymal activated β-catenin protein (D).