Department of Molecular Endocrinology, National Institute for Research in Reproductive Health (ICMR-NIRRH), Mumbai, Maharashtra, India.
Fertility Clinic and IVF Center, Mumbai, Maharashtra, India.
Mol Hum Reprod. 2022 Jun 30;28(7). doi: 10.1093/molehr/gaac019.
Peripheral and tissue-specific alterations in global DNA methylation (5-methylcytosine (5mC)) and DNA hydroxymethylation (5-hydroxymethylcytosine (5hmC)) profiles have been identified as both 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 the 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 substantially altered in PCOS, we assessed the global 5hmC levels in peripheral blood leukocytes 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. Furthermore, 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 (de novo 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.
外周组织和组织特异性的全基因组 DNA 甲基化（5-甲基胞嘧啶（5mC））和 DNA 羟甲基化（5-羟甲基胞嘧啶（5hmC））谱的改变已被鉴定为疾病预测的生物标志物，也是失调的局部基因网络的特征。5mC 谱中的全基因组和基因特异性表观遗传改变在多囊卵巢综合征（PCOS）的发病机制中具有广泛的影响。然而，在 PCOS 中，没有研究将 5mC 和 5hmC 特征的定量与 DNA 甲基化和去甲基化酶的表达水平相结合，作为甲基化和去甲基化途径的各自指标。我们之前已经表明，PCOS 中 5mC 特征没有明显改变，因此我们评估了 40 名对照和 40 名 PCOS 妇女的外周血白细胞和卵丘颗粒细胞（CGC）中的全基因组 5hmC 水平。这项分析显示 PCOS 妇女的 CGC 中 5hmC 水平更高，表明去甲基化途径更为活跃。此外，我们评估了 DNA 去甲基化和甲基化酶的转录和蛋白表达水平，即 ten-eleven translocation methylcytosine dioxygenases（TET1、TET2、TET3）和 DNA methyltransferases（DNMT1、DNMT3A 和 DNMT3B）。发现 PCOS 妇女的所有三种 TET 的相对转录和蛋白表达水平都较高，TET mRNA 表达谱与 CGC 中的 5hmC 水平呈正相关。此外，PCOS 中所有三种 DNMT 基因的转录表达都发生了改变，尽管只有下调的 DNMT3A 转录与 5mC 水平降低相关。在蛋白水平上，DNMT1（维持甲基化酶）的表达更高，而 DNMT3A（从头甲基化酶）的表达则低于对照组。总的来说，这些结果表明 PCOS 妇女的 CGC 中 DNA 甲基化的改变可能部分是由于 TET 和 DNMT3A 的转录调控内在改变所致。
