RUNX2 and ankylosis: A failure in growth, chondrogenesis, and endochondral ossification occurred in the mutant stylopodial cartilaginous element, accompanied by a down-regulation of several genes that are known to be essential for skeletogenesis, including Runx2, Runx3 and Ihh. Indeed, besides the limb phenotype, Shox2-deficient mice exhibit severe defects in a number of developing organs (heart and palate), as well as the TMJ that exhibits dysplasia and ankylosis [10,11,12].