FTO protein regulates the TGF-β signalling pathway through RNA N6-methyladenosine modification to induce unexplained recurrent spontaneous abortion

Recent studies have revealed the involvement of RNA m6A modification in embryonic development; however, the relationship between aberrant RNA m6A modification and unexplained recurrent spontaneous abortion (URSA) remains unclear. In this study, we analysed the level of RNA m6A modification in trophoblasts using dot blot, RNA m6A quantification, and MeRIP assays. By integrating data from the GEO database, RNA-Seq, and MeRIP-Seq, we examined the aberrant expression of m6A methyltransferases and their downstream molecules in chorionic villus (placental) tissues. RNA pull-down, RIP, and electrophoretic mobility shift assay were used to analyse the binding relationship between the YTHDC1 protein and MEG3. Additionally, RNA stability and BrU immunoprecipitation chase assays were utilised to elucidate the regulation of MEG3 stability by YTHDC1. ChIP and DNA pull-down RNA experiments were performed to elucidate the mechanism by which MEG3 targets EZH2 to the TGF-β1 promoter. The results showed that the expression of the m6A demethylase FTO protein was significantly increased in URSA trophoblasts, leading to inhibition of the MEG3 m6A modification and weakening of the stabilising effect of the m6A binding protein YTHDC1 on MEG3. Furthermore, MEG3 was found to bind simultaneously with the EZH2 protein and the TGF-β1 gene promoter, enabling the localisation of EZH2 protein to the TGF-β1 gene promoter and subsequent inhibition of TGF-β1 gene expression. In summary, our findings elucidate the mechanism by which FTO protein regulates the MEG3-TGF-β signalling pathway, thereby suppressing trophoblast invasion and proliferation in URSA trophoblast cells. These findings provide new insights for the treatment of URSA.