It appears that adequate RUNX2 is also dosage-dependent since haploinsufficiency of Runx2 in mice or RUNX2 in humans causes hypoplastic clavicles and delayed closure of the fontanelles, defects that are characteristic of cleidocranial dysplasia in humans [15, 16]. The gene discussed is RUNX2; the disease is cleidocranial dysplasia 1.