DLX3 and tricho-dento-osseous syndrome: The distal-less homeobox 3 (DLX3) gene causes AI as a part of trichodento-osseous (TDO) syndrome.60If the hair and bone abnormalities in TDO are not noticeable, the condition is designated AI hypoplastic hypomaturation with taurodontism (AIHHT).61, 62