RUNX2 and cleidocranial dysplasia 1: Mice heterozygous for mutant RUNX2 recapitulate human CCD, and mice homozygous for mutant RUNX2 were deficient in osteoblasts and vascularisation of marrow due to a lack of osteoblast and endothelial differentiation of periosteal mesenchymal stem cells (MSCs) [38, 39, 62, 63].