Evidence for TET-mediated DNA demethylation as an epigenetic alteration in cumulus granulosa cells of women with polycystic ovary syndrome

Abstract

Peripheral and tissue-specific alterations in global DNA methylation (5mC) and hydroxymethylation (5hmC) profiles have been charted as biomarkers for disease prediction and as hallmarks of dysregulated localized gene networks. Global and gene-specific epigenetic alterations in the 5mC profiles have shown widespread implications in etiology of polycystic ovary syndrome (PCOS). However, there has been no study in PCOS that integrates the quantification of 5mC and 5hmC signatures alongside the expression levels of DNA methylating and demethylating enzymes as respective indicators of methylation and demethylation pathways. Having previously shown that the 5mC signatures are not greatly altered in PCOS, we assessed the global 5hmC levels in peripheral blood leukocytes (PBLs) and cumulus granulosa cells (CGCs) of 40 controls and 40 women with PCOS. This analysis revealed higher 5hmC levels in CGCs of PCOS women, indicating a more dominant demethylation pathway. Further, we assessed the transcript and protein expression levels of DNA demethylating and methylating enzymes, i.e. ten-eleven translocation methylcytosine dioxygenases (TET1, TET2, TET3) and DNA methyltransferases (DNMT1, DNMT3A and DNMT3B), respectively, in CGCs. The relative transcript and protein expression levels of all three TETs were found to be higher in women with PCOS; and the TET mRNA expression profiles were positively correlated with 5hmC levels in CGCs. Also, all three DNMT genes showed altered transcript expression in PCOS, although only the downregulated DNMT3A transcript was correlated with decreasing 5mC levels. At the protein level, the expression of DNMT1 (maintenance methylation enzyme) was higher, while that of DNMT3A (denovo methylation enzyme) was found to be lower in PCOS compared to controls. Overall, these results indicate that DNA methylation changes in CGCs of PCOS women may arise partly due to intrinsic alterations in the transcriptional regulation of TETs and DNMT3A.

Bioinformatics Analysis of the Role of Rna Modification Regulators in Polycystic Ovary Syndrome

“…Previous studies have reported ALYREF expression in ovarian cancer [38] [39]. AGO2 dysfunction plays a signi cant role in obesity in PCOS patients [40,41] and TET2 may indicate epigenetic alterations in the cumulus granulosa cells of women with PCOS [42]. Conversely, YTHDF2 is believed to suppress tumor growth through immune reprogramming to enhance CD8 + T cell-mediated antitumor immunity [43].…”

“…Pathway enrichment analyses indicated the involvement of various pathways, including the Notch, Wnt, IL2, and IL6 signaling pathways. Recent studies have further demonstrated Notch signaling plays a signi cant role in the ovary [42,47,48] ,while Wnt signaling has been linked to the effect of speci c treatments for PCOS [44]. Further, a clinical study found that letrozole activated the Wnt/B-catenin pathway, leading to full endometrial proliferation in women with PCOS receiving letrozole [49].IL-6 signal,ing is associated with in ammation in ovarian syndrome [50].…”

Polycystic Ovary Syndrome: Challenges and Possible Solutions

“…Furthermore, treatment of these third-generation prenatal Anti-Mullerian Hormone (AMH) exposed mice female offspring with methylating medication can reverse their PCOS-like neuroendocrine and metabolic alterations [ 16 ]. Sagvekar et al [ 17 ] revealed that the alternation in transcriptional regulation of translocation methylcytosine dioxygenases (TETs) and DNA methyltransferases 3A (DNMT3A) may contribute to DNA methylation changes in cumulus granulosa cells of PCOS women. Nowadays, an increasing number of genome-wide association studies on prenatal hyperandrogenism-induced methylation in the ovarian tissue of PCOS rats are emerging, which will provide a more experimental basis for future PCOS treatment.…”