RUNX2 and cleidocranial dysplasia 1: Remarkably, 16 of the 22 Runx2+/−/CMV-Nell-1 mice demonstrated “rescue” of calvarial bone defects associated with the CCD phenotype on skeletal or μCT analyses (Fig. 3C, D), whereas Nell-1 did not rescue bone formation in the Runx2 null mice (data not shown).