RUNX2 and cleidocranial dysplasia 1: Unlike other knockout model of downstream osteogenic gene of Runx2, animal knockout models [55] showed that loss of Nell-1 results in reduced thickness and density of calvarial bones in ENU-induced Nell-1–deficient (END) mice, similar to CCD-like calvarial phenotypes, in addition to rib cage and vertebral abnormalities [64].