Epitranscriptome marks detection and localization of RNA modifying proteins in mammalian ovarian follicles

• Published in: Journal of ovarian research Vol. 16; no. 1; p. 90
• Main Authors: Dubuc, Karine, Marchais, Mathilde, Gilbert, Isabelle, Bastien, Alexandre, Nenonene, Karen E, Khandjian, Edward W, Viger, Robert S, Delbes, Géraldine, Robert, Claude
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 10.05.2023; BioMed Central; BMC
• Subjects: 3' Untranslated regions; Animals; Antibodies; Binding proteins; Cattle; Confocal microscopy; DNA methylation; Embryonic development; Enzymes; Epigenetic inheritance; Epigenetics; Epitranscriptome; Female; Follicles; Folliculogenesis; Gene expression; Gene silencing; Genetic transcription; Genomes; Genomics; Immunofluorescence; Liver; Localization; Mammals - genetics; Mammals - metabolism; Messenger RNA; Methylation; Methyltransferases; Mice; N6-methyladenosine; Oocytes; Oocytes - metabolism; Ovarian Follicle - metabolism; Ovaries; Physiological aspects; Polyadenylation; Polyvinyl alcohol; Post-transcription; Protein binding; Proteins; RNA - metabolism; RNA methylation; RNA modifying enzyme; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Messenger, Stored - metabolism; Scientific equipment and supplies industry; Somatic cells; Swine; Transzonal projections; Canada; United States; United States > US; Transzonal projections; Somatic cells; Epitranscriptome; RNA modifying enzyme; Oocytes; RNA methylation
• ISSN: 1757-2215; 1757-2215
• DOI: 10.1186/s13048-023-01172-8

Most of the resources that support the early development of the embryo are stored in the oocyte. Clearing of maternal resources and activation of the embryonic genome to produce its own mRNA transcripts marks the maternal-to-embryo transition. Dependence on stored mRNA can last from a few hours to several days, depending on animal species. The mechanisms regulating stabilization and recruitment of stored maternal transcripts have not yet been described in full detail but are known to involve reversible polyadenylation and modulation of 3'UTR-mediated elements. RNA epigenetic modifications, new players in this field, have an important role in RNA regulation and stabilization. The objectives of this study were first to determine if some of post-transcriptional methylation of stored mRNA is greater in oocytes than in somatic cells. We found that m A, known to be the most prevalent and involved in various aspects of RNA metabolism and physiological functions, is particularly abundant in porcine oocyte mRNA compared to liver used as a somatic tissue reference. The second objective was to compare the epitranscriptome machinery, such as methyltransferases ("writers"), binding proteins ("readers") and demethylases ("erasers") catalyzing the different process, in follicles and oocytes of different mammalian species by immunofluorescence and confocal microscopy. The expression and localization patterns of these proteins differ between mice, pigs and cows ovaries and oocytes. m C-associated proteins were generally less abundant. In contrast, m A-associated proteins were expressed strongly during the early and late stages of folliculogenesis. Transzonal projections were found to contain more granules bearing the m C mark in mice but both m C and m A methylation marks in association with mature oocytes of pigs and cows. Eraser proteins showed the greatest interspecies diversity in terms of distribution in the germinal tissues. So far, few studies have looked at the oocyte and ovarian epitranscriptomic profile. Our findings indicate that a hitherto unrecognized species-specific layer of transcript regulation occurs at the RNA level and might be consequential during the oocyte transcriptional silencing period.