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Lookup NU author(s): Dr Miguel Velazquez
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Background: Exposure to elevated levels of non-esterified fatty acids (NEFA) such as steric acid (SA), palmitic acid (PA]) and oleic acid (OA) during in vitro oocyte maturation (IVM) and embryo culture can impair preimplantation embryo development in cattle. However, the effect of high NEFA during the fertilization process per se have been less studied. In the present study histone H3 at lysine 27 trimethylation (H3K27me3) was analysed in bovine embryos exposed to high NEFA during in vitro fertilisation (IVF). H3K27me3 is a repressive epigenetic mark that undergoes gradual erasure from fertilization to the time of embryonic genome activation (EGA) to allow a correct EGA and progression to the blastocyst stage. Methods: After IVM, IVF took place under different NEFA levels representing physiological (Control-1[C1], 28μM SA, 23μM PA, 21μM OA) and pathophysiological (High-NEFA, 280μM SA, 230μM PA, 210μM OA, levels found in cows experiencing negative energy balance) concentrations. A second control (C2) group contained solvent. Presumptive zygotes were then culture, and resultant 2- and 4-cell embryos were collected on day 2 (IVF=day 0) to examine H3K27me3 protein expression by immunofluorescence and confocal microscopy. Fluorescence levels were quantified with the Imaris software. Data were analysed by ANOVA and T-test (mean±SEM), with percentage data arcsine transformed before analysis. Results: Cleavage rate was decreased in the high-NEFA group compared to controls (C1=57.1±7.4%, C2=59.1±7.1%, NEFA=29.8±2.6%, P=0.012). H3K27me3 levels (Log10 transformed data) in 2- (C1; n=31, C2; n=29, NEFA; n=29) and 4-cell (C1; n=23, C2; n=32, High-NEFA; n=13) embryos were not different between the groups. There was no difference in H3K27me3 expression between 2-cell and 4-cell embryos in the control groups. However, in the High-NEFA group, 2-cell embryos displayed a higher H3K27me3 expression than 4-cell embryos. Conclusion: Our data suggest that activation of key developmental genes may be delayed in embryos experiencing a high NEFA microenvironment during fertilization, which partially explain the decreased blastocyst formation previously observed in this model of high NEFA exposure (ESHRE meeting 2021, P-176).
Author(s): Idriss A, Okello E, Sturmey R, Velazquez MA
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: 19th International Congress on Animal Reproduction (ICAR)
Year of Conference: 2022
Pages: 170-170
Acceptance date: 01/03/2022
Publisher: International Congress on Animal Reproduction
