Identification of novel candidate genes implicated in odontogenic potential in the developing mouse tooth germ using transcriptome analysis

In tooth bioengineering for replacement therapy of missing teeth, the utilized cells must possess an inductive signal-forming ability to initiate odontogenesis. This ability is called odontogenic potential. In mice, the odontogenic potential signal is known to be translocated from the epithelium to the mesenchyme at the early bud stage in the developing molar tooth germ. However, the identity of the molecular constituents of this process remains unclear.Therefore, in this study, whole transcriptome profiles of the mouse molar tooth germ epithelium and mesenchyme were investigated using the RNA sequencing (RNA-seq) technique. The analyzed transcriptomes corresponded to two developmental stages, embryonic day 11.5 (E11.5) and 14.5 (E14.5), which represent the odontogenic potential shifts.We identified differentially expressed genes (DEGs), which were specifically overexpressed in both the E11.5 epithelium and E14.5 mesenchyme, but not expressed in their respective counterparts. Of the fifty-five DEGs identified, the top three most expressed transcription factor genes (transcription factor AP-2 beta isoform 3 [Tfap2b], developing brain homeobox protein 2 [Dbx2], and insulin gene enhancer protein ISL-1 [Isl1]) and three well-studied tooth development-related genes (transcription factor HES-5 [Hes5], platelet-derived growth factor D precursor [Pdgfd], semaphrin-3A precursor [Sema3A]) were selected and validated by quantitative RT- PCR. Using immunofluorescence staining, the Tfap2b protein expression was found to be localized only at the E11.5 epithelium and E14.5 mesenchyme. Thus, our empirical findings in the present study may provide a new perspective into the characterization of the molecules responsible for the odontogenic potential and may have an implication in the cell-based whole tooth regeneration strategy.