Support for this mechanism comes from premature activation of Runx2 in embryonic day (E) 9.5 mice, as well as from the deletion of one allele of Twist1 both of which result in enhanced osteogenesis and craniosynostosis (Bourgeois et al., 1998; Maeno et al., 2011). This evidence concerns the gene RUNX2 and craniosynostosis.