Altered m ⁶ A modification is involved in up-regulated expression of FOXO3 in luteinized granulosa cells of non-obese polycystic ovary syndrome patients

The pathophysiology of polycystic ovary syndrome (PCOS) is characterized by granulosa cell (GC) dysfunction. m⁶ A modification affects GC function in patients with premature ovarian insufficiency (POI), but the role of m⁶ A modification in PCOS is unknown. The purpose of the prospective comparative study was to analyse the m⁶ A profile of the luteinized GCs from normovulatory women and non-obese PCOS patients following controlled ovarian hyperstimulation. RNA m⁶ A methylation levels were measured by m⁶ A quantification assay in the luteinized GCs of the controls and PCOS patients. Then, m⁶ A profiles were analysed by methylated RNA immunoprecipitation sequencing (MeRIP-seq). We reported that the m⁶ A level was increased in the luteinized GCs of PCOS patients. Comparative analysis revealed differences between the m⁶ A profiles from the luteinized GC of the controls and PCOS patients. We identified FOXO3 mRNA with reduced m⁶ A modification in the luteinized GCs of PCOS patients. Selectively knocking down m⁶ A methyltransferases or demethylases altered expression of FOXO3 in the luteinized GCs from the controls, but did not in PCOS patients. These suggested an absence of m⁶ A-mediated transcription of FOXO3 in the luteinized GCs of PCOS patients. Furthermore, we demonstrated that the involvement of m⁶ A in the stability of the FOXO3 mRNA that is regulated via a putative methylation site in the 3'-UTR only in the luteinized GCs of the controls. In summary, our findings showed that altered m⁶ A modification was involved in up-regulated expression of FOXO3 mRNA in the luteinized GCs from non-obese PCOS patients following controlled ovarian hyperstimulation.

Keywords: FOXO3; N6-methyladenosine; luteinized granulosa cells; mRNA decay; polycystic ovary syndrome.