Patterning of the murine dentition by homeobox genes.

Homeobox genes have been shown to be important for the regulation of pattern formation of many systems during embryogenesis. Overlapping domains of Hox gene expression in the paraxial mesoderm have been suggested to create a combinatorial code of expression (Hox code) specifying the structures of individual segments such as the vertebrae. Hox genes are not expressed in the neural crest cells contributing to tooth formation, and so a Hox code can not be involved in patterning the dentition. It has previously been proposed that other, non-Hox homeobox genes may pattern the dentition. Expression data in this paper shows that there is a pattern of overlapping domains of homeobox gene expression in facial mesenchyme prior to the initiation of tooth development. We propose that expression of these genes constitutes an odontogenic homeobox code which patterns the dentition.