Collectively, both animal model studies and cell or molecular biology studies suggest that Runx2 haploinsufficiency or mutation leads to impaired RANKL/OPG, MMP9, and RANK/RANKL signaling during osteoclastogenesis, which partly results in arrested tooth eruption in patients with CCD [36]. The gene discussed is TNFSF11; the disease is cleidocranial dysplasia 1.