In order to compare Wnt/ β-catenin expression in mouse and chick facial primordia during development, we performed an immunohistochemical analysis of both protein expressions in E12 to E17 mouse embryos and in E3 and E10 chick embryos. During odontogenesis, from bud to bell stage, both proteins exhibit similar fixation patterns, with epithelial and mesenchymal immunoreactivity, consistant with literature data. Double labelling demonstrates that the same cells express both antigens, even in undif ferentiated mesenchyme. The enamel knot, and the ameloblastic and odontoblastic layers are stained at the same manner. In the chick, Wnt and β-catenin are diffusely present on craniofacial mesenchyme. In both species, premuscular blastemata express Wnt and β-catenin, but Wnt is specifically expressed on the perichondrium and ossification centers, suggesting a role independent from β-catenin pathway.

KEY WORDS: Mouse; Chick; Embryo; Wnt; β-catenin; Tooth.