Interspecific Variation in One-Carbon Metabolism within the Ovarian Follicle, Oocyte, and Preimplantation Embryo: Consequences for Epigenetic Programming of DNA Methylation

Clare, Constance E.; Pestinger, Valerie; Kwong, Wing Yee; Tutt, Desmond A. R.; Xu, Juan; Byrne, Helen M.; Barrett, David A.; Emes, Richard D.; Sinclair, Kevin D.

Abstract

One-carbon (1C) metabolism provides methyl groups for the synthesis and/or methylation 20 of purines and pyrimidines, biogenic amines, proteins and phospholipids. Our understanding of 21 how 1C pathways operate, however, pertains mostly to the (rat) liver. Here we report that 22 transcripts for all bar two genes (i.e. BHMT, MAT1A) encoding enzymes in the linked methionine-23 folate cycles are expressed in all cell types within the ovarian follicle, oocyte and blastocyst in the 24 cow, sheep and pig; as well as in rat granulosa cells (GCs) and human KGN cells. BHMT protein 25 was absent in bovine theca and GCs, as was activity of this enzyme in GCs. Mathematical modelling 26 predicted that absence of this enzyme would lead to more volatile S-adenosylmethionine-mediated 27 transmethylation in response to 1C substrate (e.g., methionine) or cofactor provision. We tested the 28 sensitivity of bovine GCs to reduced methionine (from 50 to 10 µM) and observed a diminished flux 29 of 1C units through the methionine cycle. We then used Reduced-Representation Bisulfite 30 Sequencing to demonstrate that this reduction in methionine during bovine embryo culture leads 31 to genome-wide alterations to DNA methylation in >1,600 genes, including a cohort of imprinted 32 genes linked to an abnormal fetal-overgrowth phenotype. Bovine ovarian and embryonic cells are 33 acutely sensitive to methionine, but further experimentation is required to determine the 34 significance of interspecific variation in BHMT expression. 35

Citation

Clare, C. E., Pestinger, V., Kwong, W. Y., Tutt, D. A. R., Xu, J., Byrne, H. M., …Sinclair, K. D. (2021). Interspecific Variation in One-Carbon Metabolism within the Ovarian Follicle, Oocyte, and Preimplantation Embryo: Consequences for Epigenetic Programming of DNA Methylation. International Journal of Molecular Sciences, 22(4), Article 1838. https://doi.org/10.3390/ijms22041838

• Journal Article Type: Article
• Acceptance Date: Feb 9, 2021
• Online Publication Date: Feb 12, 2021
• Publication Date: Feb 12, 2021
• Deposit Date: Feb 12, 2021
• Publicly Available Date: Feb 12, 2021
• Journal: International Journal of Molecular Sciences
• Print ISSN: 1661-6596
• Electronic ISSN: 1422-0067
• Publisher: MDPI
• Peer Reviewed: Peer Reviewed
• Volume: 22
• Issue: 4
• Article Number: 1838
• DOI: https://doi.org/10.3390/ijms22041838
• Keywords: One-carbon metabolism; Methionine; Assisted Reproduction Technologies (ART); Embryo; Epigenetics; DNA methylation; genomic imprinting
• Public URL: https://nottingham-repository.worktribe.com/output/5318680
• Publisher URL: https://www.mdpi.com/1422-0067/22/4/1838