Runt-Related Transcription Factor 2 (RUNX2), a gene implicated in cleidocranial dysplasia (Online Mendelian Inheritance in Man; OMIM #119600), is a crucial transcription factor of osteoblast and chondrocyte differentiation (Ducy et al., 1997; Komori et al., 1997; Yoshida et al., 2004). The gene discussed is RUNX2; the disease is cleidocranial dysplasia 1.