Unknown,Transcriptomics,Genomics,Proteomics

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Exposure of bovine oocytes and embryos to elevated non-esterified fatty acid concentrations: integration of epigenetic and transcriptomic signatures in resultant blastocysts [gene expression]

ABSTRACT: Metabolic stress associated with negative energy balance in high producing dairy cattle and obesity in women is a risk factor for decreased fertility. Non-esterified fatty acids (NEFA) are involved in this pathogenesis as they jeopardize oocyte and embryo development. Growing evidence indicates that maternal metabolic disorders can disturb epigenetic programming, and more specifically DNA methylation, in the offspring. Final oocyte maturation and early embryo development coincide with specific methylation changes and both time periods are sensitive to adverse environments. Therefore, we investigated whether elevated NEFA concentrations affect the establishment and maintenance of DNA methylation patterns in oocytes and embryos and subsequently alter transcriptomic profiles and developmental competence of the resultant blastocysts. To do this, bovine oocytes and embryos were exposed to different NEFA concentrations in two separate experiments. In the first experiment, oocytes were matured in vitro for 24 hours in medium containing: 1) physiological (âBASALâ) concentrations of oleic (OA), palmitic (PA) and stearic (SA) or 2) elevated (pathophysiological or âHIGH COMBIâ) concentrations of OA, PA and SA. In the second experiment, zygotes were cultivated in vitro for 6.5 days under BASAL or HIGH COMBI conditions. The developmental competence was evaluated by assessing cleavage and blastocyst rate. Overall gene expression and DNA methylation of resultant blastocysts were analyzed using microarray techniques. Data regarding DNA methylation were re-evaluated by pyrosequencing. HIGH COMBI-exposed oocytes and embryos displayed a lower competence to develop into blastocysts compared to their BASAL-exposed counterparts (19.3 % compared to 23.2 % and 18.2 % compared to 25.3 %, respectively) (P < 0.05). HIGH COMBI-exposed oocytes and embryos resulted in blastocysts with altered DNA methylation profiles and transcriptomic fingerprints, compared to BASAL-exposed counterparts. Differences in gene expression and methylation were more pronounced after exposure during culture compared to maturation suggesting that zygotes are more susceptible to an adverse environment. Main gene networks affected were related to lipid and carbohydrate metabolism, cell death, immune response and metabolic disorders. This may offer clues regarding the high rate of embryonic loss and metabolic diseases during later stages of life observed in offspring from mothers displaying lipolytic disorders. The effect of elevated NEFA exposure during embryo culture (6.5 days) on gene expression was evaluated by exposing embryos to the BASAL or HIGH COMBI conditions. A total of 1412 oocytes were used, equally distributed between treatments in 4 replicates. Resultant day 7.5 blastocysts were snap frozen for subsequent transcriptome analysis (80 blastocysts in each experiments, equally collected between treatments in 4 replicates).

ORGANISM(S): Bos taurus

SUBMITTER: Karolien Desmet

PROVIDER: E-GEOD-83767 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Metabolic stress associated with negative energy balance in high producing dairy cattle and obesity in women is a risk factor for decreased fertility. Non-esterified fatty acids (NEFA) are involved in this pathogenesis as they jeopardize oocyte and embryo development. Growing evidence indicates that maternal metabolic disorders can disturb epigenetic programming, and more specifically DNA methylation, in the offspring. Final oocyte maturation and early embryo development coincide with specific methylation changes and both time periods are sensitive to adverse environments. Therefore, we investigated whether elevated NEFA concentrations affect the establishment and maintenance of DNA methylation patterns in oocytes and embryos and subsequently alter transcriptomic profiles and developmental competence of the resultant blastocysts. To do this, bovine oocytes and embryos were exposed to different NEFA concentrations in two separate experiments. In the first experiment, oocytes were matured in vitro for 24 hours in medium containing: 1) physiological (âBASALâ) concentrations of oleic (OA), palmitic (PA) and stearic (SA) or 2) elevated (pathophysiological or âHIGH COMBIâ) concentrations of OA, PA and SA. In the second experiment, zygotes were cultivated in vitro for 6.5 days under BASAL or HIGH COMBI conditions. The developmental competence was evaluated by assessing cleavage and blastocyst rate. Overall gene expression and DNA methylation of resultant blastocysts were analyzed using microarray techniques. Data regarding DNA methylation were re-evaluated by pyrosequencing. HIGH COMBI-exposed oocytes and embryos displayed a lower competence to develop into blastocysts compared to their BASAL-exposed counterparts (19.3 % compared to 23.2 % and 18.2 % compared to 25.3 %, respectively) (P < 0.05). HIGH COMBI-exposed oocytes and embryos resulted in blastocysts with altered DNA methylation profiles and transcriptomic fingerprints, compared to BASAL-exposed counterparts. Differences in gene expression and methylation were more pronounced after exposure during culture compared to maturation suggesting that zygotes are more susceptible to an adverse environment. Main gene networks affected were related to lipid and carbohydrate metabolism, cell death, immune response and metabolic disorders. This may offer clues regarding the high rate of embryonic loss and metabolic diseases during later stages of life observed in offspring from mothers displaying lipolytic disorders. Two experiments were set up to characterize the epigenomic profile of the resultant day 7.5 blastocysts. In the first (in vitro maturation or IVM) experiment, the effect of elevated NEFA exposure during oocyte maturation (24 h) on DNA methylation profiles was evaluated by exposing oocytes to the BASAL or HIGH COMBI conditions. In the second (in vitro culture or IVC) experiment, the effect of elevated NEFA exposure during embryo culture (6.5 days) on DNA methylation marks was evaluated by exposing embryos to the BASAL or HIGH COMBI conditions. A total of 1039 and 1412 oocytes were used in the IVM and IVC experiment, respectively, equally distributed between treatments in 4 replicates. Resultant day 7.5 blastocysts were snap frozen for subsequent DNA methylation analysis (80 blastocysts in each experiments, equally collected between treatments in 4 replicates).

Project description:Metabolic stress associated with negative energy balance in high producing dairy cattle and obesity in women is a risk factor for decreased fertility. Non-esterified fatty acids (NEFA) are involved in this pathogenesis as they jeopardize oocyte and embryo development. Growing evidence indicates that maternal metabolic disorders can disturb epigenetic programming, and more specifically DNA methylation, in the offspring. Final oocyte maturation and early embryo development coincide with specific methylation changes and both time periods are sensitive to adverse environments. Therefore, we investigated whether elevated NEFA concentrations affect the establishment and maintenance of DNA methylation patterns in oocytes and embryos and subsequently alter transcriptomic profiles and developmental competence of the resultant blastocysts. To do this, bovine oocytes and embryos were exposed to different NEFA concentrations in two separate experiments. In the first experiment, oocytes were matured in vitro for 24 hours in medium containing: 1) physiological (“BASAL”) concentrations of oleic (OA), palmitic (PA) and stearic (SA) or 2) elevated (pathophysiological or “HIGH COMBI”) concentrations of OA, PA and SA. In the second experiment, zygotes were cultivated in vitro for 6.5 days under BASAL or HIGH COMBI conditions. The developmental competence was evaluated by assessing cleavage and blastocyst rate. Overall gene expression and DNA methylation of resultant blastocysts were analyzed using microarray techniques. Data regarding DNA methylation were re-evaluated by pyrosequencing. HIGH COMBI-exposed oocytes and embryos displayed a lower competence to develop into blastocysts compared to their BASAL-exposed counterparts (19.3 % compared to 23.2 % and 18.2 % compared to 25.3 %, respectively) (P < 0.05). HIGH COMBI-exposed oocytes and embryos resulted in blastocysts with altered DNA methylation profiles and transcriptomic fingerprints, compared to BASAL-exposed counterparts. Differences in gene expression and methylation were more pronounced after exposure during culture compared to maturation suggesting that zygotes are more susceptible to an adverse environment. Main gene networks affected were related to lipid and carbohydrate metabolism, cell death, immune response and metabolic disorders. This may offer clues regarding the high rate of embryonic loss and metabolic diseases during later stages of life observed in offspring from mothers displaying lipolytic disorders.

Project description:An important facet of the oocyte to embryo transition in mammals is the rapid elimination of a subset of the maternal products that got accumulated during oogenesis. RNA studies support a view that the transition occurs quite rapidly. Whether this applies also for proteins remains to be determined beyond the very few cases known to date. We report that COPS3, the 3rd subunit of the COP9 signalosome complex, forms a large protein deposit in mouse oocytes (94th percentile of the riBAQ distribution). The one and only knock-out study had previously shown that Cops3 null (-/-) mouse embryos obtained from heterozygous intercrosses arrested after 5.5 dpc and were resorbed by 8.5 dpc mainly due to increased cell death in the epiblast (PMID: 12972600). However, more recent studies from our group ascribed Cops3 gene with a developmental role already at the 2-cell stage. Specifically, the sister blastomeres differ from each other in Cops3 mRNA levels and distribution, preceding the discordance of epiblast formation in derivative twin blastocysts, and implicating Cops3 in the molecular underpinnings of totipotency. This discrepancy between original knock-out result and recent observations can be resolved if we posit that the first requirement for Cops3 gene function was bridged by maternal protein that outlived the locus excision, consistent with the observation that Cops3 -/- blastocysts had the same immunostaining intensity as the +/- or +/+ counterparts in the original knock-out study. Thus, these contradicting observations support a hypothesis that 5.5 dpc may not have been the first time when the gene function was needed in development, but the second time. To test this hypothesis, pronuclear-stage mouse oocytes were subjected to an immunological method that directly targets the protein of interest by way of proteasomal degradation of the COPS3-antibody-TRIM21 complex. Briefly, pronuclear-stage mouse oocytes were microinjected with a mixture of the COPS3-specific purified monoclonal IgG antibody, mCherry-Trim21 mRNA and Oregon Green dextran beads (inert tracer). Injected oocytes were then allowed to develop and collected for lysis 24 hours later, when they reached the 2-cell stage but were not able to progress further. In addition to the COPS3, we targeted two additional proteins, OCT4 and TEAD4. The following seven experimental groups were examined by liquid chromatography-mass spectrometry (LC-MS/MS) using the pipeline described previously by Israel et al.: 1) non-manipulated 2-cell embryos; 2) 2-cell embryos from oocytes injected with Oregon Green dextran beads; 3) 2-cell embryos from oocytes injected with mCherry-Trim21 mRNA and Oregon Green; 4) 2-cell embryos from oocytes injected with mCherry-Trim21 mRNA, Oregon Green and anti-COPS3 (Abcam 79698); 5) 2-cell embryos from oocytes injected with anti-COPS3 (Abcam 79698) and Oregon Green; 6) 2-cell embryos from oocytes injected with mCherry-Trim21 mRNA, Oregon Green and anti-TEAD4 (Abcam 58310); 7) 2-cell embryos from oocytes injected with mCherry-Trim21 mRNA, Oregon Green and anti-OCT4 (Abcam 181557).

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Exposure of bovine oocytes and embryos to elevated non-esterified fatty acid concentrations: integration of epigenetic and transcriptomic signatures in resultant blastocysts [gene expression]

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