Fig. 1.

Synergy between loss of Wnt7a and loss of Wnt7b in the severity of limb development phenotypes. (A) Littermate WT (left) and Cdx2-Cre;Wnt7a^−/−;Wnt7b^CKO/− (right) E18 mice showing severe truncations of fore and hind limbs (white arrows) following efficient Cre-mediated recombination in the caudal embryo and less efficient Cre-mediated recombination in the rostral embryo. Front and side views of one WT and two mutant embryos. (B) Alcian Blue staining at E15 showing progressively more severe truncations with progressively reduced Wnt7a and Wnt7b function (from left to right). Insets, images of the foot rotated to more clearly show the digits. (C) Quantification of E15 limb skeletal defects with progressively reduced Wnt7a and Wnt7b function (from left-to-right). The scoring procedure is described in the Materials and Methods section. In C, a comparison between the fourth and fifth genotypes (Wnt7a^−/−;Wnt7b^+/+ versus Wnt7a^−/−;Wnt7b^CKO/+) and between the eighth and ninth genotypes (Wnt7a^−/−;Wnt7b^+/− versus Wnt7a^−/−;Wnt7b^CKO/−) shows a modestly greater phenotype score with the Wnt7b CKO allele compared with the WT allele, suggesting that the introduction of loxP sites may be reducing Wnt7b expression. P-values were calculated using the non-parametric Mann–Whitney–Wilcoxon test. Error bars show the mean±s.d. Each circle represents a single limb.