Linking new genes to an odontogenesis TP63-mediated gene regulatory network that is peripheral to jaw morphogenesis

Abstract

Despite that teeth and jawbones can develop and evolve independently of each other, the genetic processes that independently regulate cranial and dental morphogenesis remain unclear. Previous microarray screens indicated that a TP63-mediated gene regulatory network is integral to odontogenesis but peripheral to jaw morphogenesis. Here, I characterized the expression of four genes flagged by our lab’s previous microarray screens, comparing embryonic wild-type and TP63-null (TP63-/-) mutant mouse mandible prominences. I hypothesized that in the normal dental epithelium, TP63 up-regulates Fermt1 and Pltp and down-regulates Cbln1 and Krt8. I validated the expression domains of these genes in TP63-/- mutant and wild-type mice using RNA in-situ hybridization on paraffin tissue sections at two stages, E11.5, just after odontogenesis begins, and at E13.5, just after odontogenesis arrests in the TP63-/- mutant. My in situ results validated our lab’s previous microarray screens. My work revealed that Fermt1 is expressed in wild-type oral epithelium and dental epithelium, and that Pltp is expressed in dental epithelium. Compared to wild-type littermates, in TP63-/- mice, Fermt1 and Pltp expression intensity in the dental epithelium was decreased. Cbln1 was not expressed in wildtype dental epithelium, although it expressed intensely in the dental epithelium of TP63-/- littermates. Krt8 was expressed in the dental epithelium of both wild-type and TP63-/- embryos, with increased intensity in the TP63-/- mice. In sum, my results largely supported my hypothesis. As such, I propose that Fermt1, Pltp, Cbln1, and Krt8 belong to a TP63-mediated gene regulatory network and co-regulate odontogenesis by mediating cell adhesion, cell signaling, and epithelial-mesenchymal interactions at early stages of tooth development.