RUNX2 and cleidocranial dysplasia 1: A functional study showed that the R190Q variant exhibited no DNA binding and markedly reduced transactivation activities.[25] This genotype is correlated with the classic CCD phenotype[25,26] and similar dental abnormalities.[11,27] Interestingly, heterozygotic Runx2 mice have no dental phenotypes, in contrast to the hyperdontia phenotype in humans; this may be attributable to composition differences in the mouse monophydont dentition, as it parallels the more simply patterned human primary dentition.