PTH regulates osteogenesis and suppresses adipogenesis through Zfp 467 in a feed-forward, cyclic AMP-dependent manner

Abstract

AbstractConditional deletion of the PTH1R in mesenchymal progenitors reduces osteoblast differentiation, enhances marrow adipogenesis and increases zinc finger protein 467 (Zfp467) expression. In contrast, genetic loss ofZfp467increasedPth1rexpression and shifts mesenchymal progenitor cell fate towards osteogenesis and higher bone mass. In this study we hypothesized that PTH1R and ZFP467 could constitute a feedback loop that facilitates PTH-induced osteogenesis and that conditional deletion ofZfp467in osteogenic precursors would lead to high bone mass. We report thatPrrxCre Zfp467but notAdipoCre Zfp467mice exhibit an identical phenotype to theZfp467-/-mice with high bone mass and greater osteogenic differentiation We also found that PTH suppressedZfp467expression primarily via the cyclic AMP/PKA pathway. Not surprisingly, PKA activation inhibited the expression ofZfp467and gene silencing ofPth1rcaused an increase inZfp467mRNA transcription. Dual fluorescence reporter assays and confocal immunofluorescence demonstrated that genetic deletion ofZfp467resulted in higher nuclear translocation of p50 that binds to the P2 promoter of thePth1rand increased its transcription. As expected,Zfp467-/-cells had enhanced production of cyclic AMP and increased glycolysis in response to exogenous PTH. Additionally, the osteogenic response to PTH was also enhanced inZfp467-/-calvarial osteoblasts, and the pro-osteogenic effect ofZfp467deletion was blocked by gene silencing ofPth1ror a PKA inhibitor. In conclusion, our findings suggest that loss or PTH1R-mediated repression ofZfp467results in a pathway that increasesPth1rtranscription via p50 and thus cellular responsiveness to PTH, ultimately leading to enhanced bone formation.