AXIN2 and tooth agenesis: As mutations in several other genes involved in WNT signaling have also been shown to cause genetic disorders featured by tooth agenesis, such as AXIN2 [7] and KREMEN1 [23], it is plausible to speculate that various combinations of sequence variants in these genes could generate a range of WNT signaling activity and cause a wide spectrum of severity in tooth agenesis.