Loss of function of the α-subunit of Runx2 due to mutation, if the identical β-subunit is preserved (Runx2+/−), results in the formation of cleidocranial dysplasia (dysostosis) [89, 90], whereas the Runx2−/− genotype is nonsurvivable [91]. The gene discussed is RUNX2; the disease is cleidocranial dysplasia 1.