DNA Methylation Is Not Involved in Preovulatory Down-Regulation of CYP11A1, HSD3B1, and CYP19A1 in Bovine Follicles but May Have a Role in Permanent Silencing of CYP19A1 in Large Granulosa Lutein Cells1

Abstract

The luteinizing hormone-induced morphological and physiological reorganization of the bovine follicle is preceded by a profound and well-orchestrated modulation of gene expression. In the present study, the cell type-specific methylation profiles of CYP11A1, HSD3B1, and CYP19A1, genes that encode key enzymes of steroid hormone biosynthesis, were analyzed to elucidate whether epigenetic parameters such as DNA methylation might be involved in gene regulation during luteinization. Transcript abundance and DNA methylation levels were determined in granulosa and theca of large dominant and late preovulatory follicles and in large granulosa lutein cells isolated from corpora lutea cyclica and graviditatis. Levels of the steroid hormones progesterone and estradiol-17beta were monitored to assess the physiological status of individual follicles. From our results, we conclude that (1) individual, even closely neighboring, CpG dinucleotides can show very different methylation levels; (2) proximal (<300 base pair [bp] from the respective transcription start sites) but not distal CpGs show cell type-specific methylation levels; (3) higher methylation levels suggestively preclude high levels of gene expression; (4) DNA methylation is not involved in the transient (HSD3B1 and CYP11A1) respectively permanent (CYP19A1) down-regulation of gene expression in late preovulatory follicles; and (5) DNA methylation may have a role in the permanent shutdown of promoter 2-directed CYP19A1 expression in large (granulosa derived) lutein cells.

Profiling of Luteal Transcriptome during Prostaglandin F2-Alpha Treatment in Buffalo Cows: Analysis of Signaling Pathways Associated with Luteolysis

“…It has been established that in response to LH surge, CYP19A1 expression gets down regulated and may even be absent post ovulation [85]–[87]. However, others [36] and we (in the present study) have observed CYP19A1 expression in the non-pregnant CL.…”

Environmental enrichment attenuates the age-related decline in the mRNA expression of steroidogenic enzymes and reduces the methylation state of the steroid 5α-reductase type 1 gene in the rat hippocampus

“…Modifications in the methylation state of the steroidogenic enzyme genes P450scc and 3β-HSD have been previously described (Vanselow et al, 2010;Zhang and Ho, 2011). In addition, changes in the DNA methylation of the P450(17α) gene were observed during cellular senescence in bovine adrenocortical cells.…”

Bioengineering the Ovarian Follicle Microenvironment

“…In the past 15 years, there has been an explosion in the “omics” world, including transcriptomics, proteomics (115, 116), metabolomics (117), and epigenomics (118). Microarrays have been used extensively to study folliculogenesis in isolated ovaries (119), follicles (120), oocytes (121), and granulosa or theca cells (122) and in untreated (123, 124) or treated cell lines (125–127).…”