RUNX2 is expressed in fusing cranial sutures and is upregulated in mice with heterozygous knock-in mutations of Fgfr1 and Pfeiffer-type craniosynostosis [Zhou et al., 2000] and in patients with non-syndromic craniosynostosis [Nacamuli et al., 2003]. Here, FGFR1 is linked to craniosynostosis.