Results: During early limb development (HH24-HH30) Dact1 and Dact2 were mainly expressed in the cartilaginous rudiments of the appendicular skeleton and perichondrium, presenting expression profiles related, but distinct. At later stages of development (HH31-HH35), the main sites of Dact1 and Dact2 expression were the developing synovial joints. In this context, Dact1 expression was shown to co-localize with regions enriched in the nuclear β-catenin protein, such as developing joint capsule and interzone. In contrast, Dact2 expression was restricted to the interzone surrounding the domains of bmpR-1b expression, a TGF-β receptor with crucial roles during digit morphogenesis. Additional sites of Dact expression were the developing tendons and digit blastemas.
Conclusions: Our data indicate that Dact genes are good candidates to modulate and, possibly, integrate Wnt and TGF-β signaling during limb development, bringing new and interesting perspectives about the roles of Dact molecules in limb birth defects and human diseases.