AXIN2 and tooth agenesis: The early molecular diagnosis of tooth agenesis may enable to improve patient care29 and to alert clinicians to counsel patients to have regular colonoscopies in early diagnosis of AXIN2 mutations.30 Moreover, the identification of causality for agenesis of the mandibular incisors, referred to herein as SMIA, may enable us to elucidate the precise molecular mechanisms of spatial gene regulation in the distinctive development of human dentition.