Reproduction, Fertility and Development Reproduction, Fertility and Development Society
Vertebrate reproductive science and technology
RESEARCH ARTICLE

Gene-specific profiling of DNA methylation and mRNA expression in bovine oocytes derived from follicles of different size categories

F. Mattern A , J. Heinzmann B C D , D. Herrmann B , A. Lucas-Hahn B , T. Haaf A and H. Niemann B
+ Author Affiliations
- Author Affiliations

A Institute of Human Genetics, Julius Maximilians University, 97070 Würzburg, Germany.

B Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, Federal Research Institute of Animal Health, Mariensee, 31535 Neustadt, Germany.

C Present address: Gynemed GmbH and CO. KG, 23738 Lensahn, Germany.

D Corresponding author. Email: heiner.niemann@fli.de

Reproduction, Fertility and Development - https://doi.org/10.1071/RD16327
Submitted: 19 August 2016  Accepted: 14 December 2016   Published online: 3 February 2017

Abstract

Epigenetic changes, such as DNA methylation, play an essential role in the acquisition of full developmental competence by mammalian oocytes during the late follicular growth phase. Here we used the bovine model to investigate the DNA methylation profiles of seven candidate genes (imprinted: bH19, bSNRPN; non-imprinted: bZAR1, bDNMT3A, bOCT4, bDNMT3 Lo and bDNMT3 Ls) and the mRNA expression of nine candidate genes (imprinted: bSNRPN, bPEG3, bIGF2R; non-imprinted: bPRDX1, bDNMT1B, bDNMT3A, bZAR1, bHSF1 and bNLRP9) in oocytes from antral follicles of three different size classes (≤2 mm, 3–5 mm, ≥6 mm) to unravel the epigenetic contribution to this process. We observed an increased number of aberrantly methylated alleles in bH19, bSNRPN and bDNMT3 Lo of oocytes from small antral follicles (≤2 mm), correlating with lower developmental competence. Furthermore, we detected an increased frequency of CpG sites with an unclear methylation status for DNMT3 Ls, specifically in oocytes from follicles ≥6 mm, predominantly at three CpG positions (CpG2, CpG7 and CpG8), of which CpG7 is a potential regulatory site. No major differences in mRNA expression were observed, indicating that the transcriptional machinery may not yet be active during the follicular growth phase. Our results support the notion that a follicle diameter of ~2 mm is a critical stage for establishing DNA methylation profiles and indicate a link between DNA methylation and the acquisition of oocyte developmental competence.

Additional keywords: abnormally methylated alleles, CpG sites, epigenetics, imprinted genes, limited dilution assay, pyro-sequencing.


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