The mediating mechanism of Oct4 in the process of cleft palate induced by 2, 3, 7, 8-tetrachlorodibenz-p-dioxin (TCDD) and all-trans retinoic acid

Abstract

2, 3, 7, 8-tetrachlorodiphenyl-p-dioxin (TCDD) and all-trans retinoic acid (atRA) have been shown to be inducers of cleft palate (CP). Relevant studies have shown that Oct transcription factor 4 (Oct4) can regulate the expression of the aromatic hydrocarbon receptor (AhR), a target gene of TCDD, as well as influence the retinoic acid signaling pathway. However, the mechanism of Oct4 regulating the interaction between TCDD and atRA in CP pathogenesis remains unclear. In order to solve the above problems, mouse embryonic palatal mesenchymal (MEPM) cells were used for further study. The results show that, TCDD and atRA induce a similar pattern of CP in vivo and significantly inhibit the proliferation of MEPM cells. In vitro, TCDD exposure led to up-regulation of AhR and cytochrome P450 1A1 (CYP1A1) expression and down-regulation of cellular retinoic acid binding protein 2 (CRABP2) and retinoic acid receptor-alpha (RARA) expression in MEPM cells. In addition, atRA exposure resulted in decreased expression of AhR and CYP1A1, and increased protein levels of RARA and CRABP2. When Oct4 was overexpressed, the down-regulation of CRABP2 and RARA by TCDD and the down-regulation of AhR by RA were reversed. The cross results of mass spectrometry and Biogrid database show that HSP90AB1 can bind to Oct4 and AhR. Co-immunoprecipitation (Co-IP) results showed that Oct4 and CRABP2 were combined, which further suggested the mediating effects of Oct4 in CP development. In summary, we hypothesize that AhR-HSP90AB1-Oct4-CRABP2 axis may play the key role mediating the interaction between TCDD and atRA in CP pathogenesis.