90 Influence of the maternal environment during the period of embryonic genome activation on the Day-4 embryo transcriptome
M. B. Rabaglino A , N. Forde B , U. Besenfelder C , V. Havlicek C , H. Blum D , A. Graf D , E. Wolf D and P. Lonergan AA School of Agriculture and Food Science, University College Dublin, Belfield, Dublin, Ireland
B Division of Reproduction and Early Development, School of Medicine, University of Leeds, Leeds, UK
C Reproduction Centre Wieselburg, Institute for Animal Breeding and Genetics, University of Veterinary Medicine, Vienna, Austria
D Laboratory for Functional Genome Analysis, Gene Center, Ludwig Maximilian University of Munich, Munich, Germany
Reproduction, Fertility and Development 35(2) 171-171 https://doi.org/10.1071/RDv35n2Ab90
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
In high-producing dairy cows, milk production during the early postpartum period impacts the circulating metabolites and negatively affects embryo survival. We have previously reported the effect of the dam metabolic status on embryo survival to the blastocyst stage; however, the molecular consequences on the embryo during its development in the oviduct are still unknown. The objective was to determine the impact of metabolic status on embryonic genome activation (EGA) using high-throughput sequencing to generate comprehensive transcriptome profiles of bovine 16-cell stage embryos which had undergone EGA in vitro or in the oviducts of primiparous postpartum dry or postpartum lactating Holstein Friesian cows. Two days after synchronised oestrus, in vitro-produced (IVP) embryos were transferred in pools of 50 four- to eight-cell stage embryos into the oviduct ipsilateral to the corpus luteum of postpartum dairy cows who were either milked (i.e. lactating) post-calving (LACT, n = 3) or were dried off immediately at calving (i.e. non-lactating; DRY, n = 3) via transvaginal endoscopic transfer. On Day 4, the oviducts were flushed, and 16-cell stage embryos were snap frozen in pools of five on an individual animal basis and stored at −80°C before analysis by RNA Seq. A control group was maintained in vitro (IV, n = 3). After quality control steps, raw files were aligned to the Bos taurus genome (ARS-UCD1.3). Raw counts were processed with the edgeR package for R. Contrasts were done between the three groups to identify differentially expressed genes (DEG) based on a false discovery rate (FDR) < 0.1 and fold change (FC) > 2. Functional analysis of the DEG was performed with the DAVID database. There were 110 DEG between DRY versus IV. Interestingly, the 54 DEG upregulated in DRY strongly enriched respiratory chain (FDR = 8.5 × 10−16), oxidative phosphorylation (5.9 × 10−16), and mitochondrial electron transport (FDR = 6.1 × 10−5). Furthermore, all DEG involved in these biological terms had a FDR < 0.05. These terms were also enriched by the 17 upregulated DEG in DRY compared with LACT (P < 0.05). Downregulated DEG in both comparisons (56 and 27, respectively) did not enrich any functional term. There were only two DEG when comparing LACT with IV. A heat map of all the DEG showed that the 13 DEG involved in mitochondrial respiration were strongly expressed in DRY, followed by LACT, and then IV (average FC was 2.9 ± 0.5 for DRY vs IV; 2.1 ± 0.4 for DRY vs LACT; and 1.4 ± 0.1 for LACT vs IV). Considering the critical role of mitochondrial respiration in embryo survival, this study demonstrates that exposure of the embryo to a favourable maternal metabolic status during EGA influences its transcriptome and, potentially, the embryonic competence for pregnancy establishment.
Funded by the European Union Seventh Framework Program FP7/2007–2013 under grant agreement 312097 (‘FECUND’).
