AXIN2 and tooth agenesis: Mutations in two proteins of the destruction complex, AXIN-2 and APC, while both disabling β-catenin phosphorylation and promoting its nuclear localization, have completely opposite effects in humans: mutations in AXIN-2 lead to hypodontia (Lammi et al., 2004), mutations in APC to hyperdontia (Thakker et al., 1995).