Fig. 6. Genetic interaction of Wnt9a and ß-catenin in chondrocyte maturation. (A) In situ hybridization for Ihh, Ptch1 and Col10a1 on alternating sections of humeri from wild type, Wnt9a^+/-;ß-cat^+/-, Wnt9a^-/- and Wnt9a^-/-;ß-cat^+/- mutant littermates. Arrowheads indicate reduced expression of Ptch1. (B) In situ hybridization on E15.5 wild-type and Wnt9a^+/-;ß-cat^+/- humeri, showing that the Ihh and Col10a1 expression domains are closer together in Wnt9a^+/-;ß-cat^+/- humeri compared with WT. (C) Immunohistochemical staining at E13.5, showing reduced ß-catenin levels in flattened and prehypertrophic chondrocytes (bracket) in Wnt9a mutants in comparison with wild type above. Similar ß-catenin levels are found in the periosteum (arrowheads). (D) Alcian Blue/Alizarin Red stained forelimbs of E15.5 wild type, Wnt9a^+/-;ß-cat^+/- and Wnt9a^-/- embryos, showing a similar size reduction of the mineralized regions of scapula and humerus in double heterozygous mutants compared with Wnt9a single mutants.