Prrx2, the paired-related homeobox transcription factor, functions as a potential regulator of pannexin 3 expression in odontoblast differentiation

Objectives: This study aimed to elucidate the roles of Prrx1 and Prrx2, homeobox transcription factors, in tooth development and determine whether Prrx2 regulates pannexin 3 (Panx3) expression, which is important in preodontoblasts.

Methods: Tooth sections were prepared from 13.5-, 15.5-, and 18.5-day-old embryonic ICR mice, and Prrx1- and Prrx2-expressing cells were identified by in situ hybridization. To clarify the direct relationship between Prrx2 and Panx3, dual-luciferase reporter assay and electrophoretic mobility shift assay (EMSA) were performed. The effect of endogenous Prrx2 suppression on Panx3 expression was analyzed using an siRNA assay.

Results: In situ hybridization revealed that in the molars, Prrx1 and Prrx2 were similarly expressed in the bud and cap stages; however, only Prrx2 was expressed in preodontoblasts at the bell stage. In the incisors, Prrx2-expressing cells were observed from dental papilla cells to preodontoblasts. In serial sections, Prrx2-expressing cells in preodontoblasts corresponded to Panx3-expressing cells. Luciferase reporter assay using luciferase reporter plasmids containing Panx3 promoter revealed that Prrx2 overexpression in HEK293 cells significantly increased luciferase activity. EMSA of nuclear extract proteins from Prrx2-overexpressing HEK293 cells or mouse dental papilla-derived cells to the Panx3 promoter showed the protein-probe complex bands. SiRNA assay revealed that Prrx2 knockdown inhibited Panx3 expression.

Conclusions: Our results suggest that Prrx2 may regulate Panx3 expression during odontoblastic differentiation.