Project description:Global hypermethylations of histone H3 lysine 9 (H3K9) tri- and di-methylation (H3K9me3/2) have been identified in bovine cloned embryos at the embryonic genome activation (EGA) stage (eight-cell stage), but the intrinsic reason for these anomalies remains elusive. To ascertain key factors responsible for aberrant H3K9 methylation, we performed RNA sequencing of transcripts in eight-cell bovine in vitro fertilized (IVF) and SCNT embryo. From the differentially expressed genes (DEGs) between IVF and SCNT embryos, we identified that the unsuccessful reactivation of two histone demethylases, KDM4D and KDM4E, is responsible for the incomplete H3K9me3/2 demethylation in SCNT embryos at the EGA stage. By mRNA injection, ectopic expression of either KDM4D or KDM4E could erase H3K9me3/2 barriers, improve blastocyst formation, and elevate cloning efficiency of bovine SCNT. To examine the detailed genes responsive to KDM4E overexpression, we also performed RNA sequencing of bovine eight-cell SCNT embryos with KDM4E compensation and found an obvious restoration of global transcriptional patterns in SCNT embryos. Our study first provides the transcriptome data set of bovine IVF and SCNT embryos during EGA with or without KDM4E overexpression, which advance the understanding of incomplete nuclear reprogramming, and contribute to the practical implications for genetically modified livestock breeding using SCNT.
Project description:The efficiency of somatic cell nuclear transfer (scNT) for production of viable offspring is relatively low as compared to in vitro fertilization (IVF), presumably due to deficiencies in epigenetic reprogramming of the donor cell genome. Such defects may also involve the population of small non-coding RNAs (sncRNAs), which are important during early embryonic developmeNT.The objective of this study was to examine dynamic changes in relative abundance of sncRNAs during the maternal-to embryonic transition (MET) in bovine embryos produced by scNT as compared to IVF by using RNA sequencing. When comparing populations of miRNA in scNT versus IVF embryos, only miR-2340, miR-345, and miR34a were differentially expressed in morulae, though many more miRNAs were differentially expressed when comparing across developmental stages. Also of interest, distinct populations of piwi-interacting like RNAs (pilRNAs) were identified in bovine embryos prior to and during embryonic genome activation (EGA) as compared bovine embryos post EGA and differentiated cells. Overall, sncRNA sequencing analysis of preimplantation embryos revealed largely similar profiles of sncRNAs for IVF and scNT embryos at the 2-cell, 8-cell, morula and blastocyst stages of developmeNT.However, these sncRNA profiles, including miRNA, piRNA and tRNA fragments, were notably distinct prior to and after completion of the MET.
Project description:Purpose: Embryonic stem cells (ESC) indefinitely maintain the pluripotent state of the blastocyst epiblast. Stem cells are invaluable for studying development and lineage commitment, and in livestock they constitute a useful tool for genomic improvement and in vitro breeding programs. Although these cells have been recently derived from bovine blastocysts, a detailed characterization of their molecular state is still lacking. Methods: Here, we compared the transcriptomic and epigenomic profiles of bovine ESC (bESC) obtained from in vitro fertilized (IVF), somatic cell nuclear transfer (SCNT), and parthenogenetic (PAR) embryos. Results: Bovine ESC were efficiently derived from SCNT and IVF embryos and expressed pluripotency markers while retaining genome stability. Transcriptome analysis revealed that only 46 genes were differentially expressed between IVF- and SCNT-derived bESC, which did not reflect significant deviation in cellular function. Additionally, by interrogating the histone marks H3K4me3, H3K9me3 and H3K27me3 with CUT&Tag, we found that the epigenomes of bESC subtypes were virtually indistinguishable. Minor epigenetic differences were randomly distributed throughout the genome and were not associated with differentially expressed or developmentally important genes. Finally, categorization of genomic regions according to their combined histone mark signal demonstrated that bESC subtypes shared the same epigenomic signatures, especially at promoters. Conclusions: Overall, we conclude that bESC derived from SCNT and IVF embryos are transcriptomically and epigenetically analogous.
Project description:Although somatic cell nuclear transfer (SCNT) cloning is more efficient in bovine than in all other species tested so far, there is a high rate of pregnancy failure that has been linked to structural and functional abnormalities of the placenta. We tested the hypothesis that these changes may originate from disturbed embryo-maternal interactions in the pre-implantation period. Therefore, we evaluated the transcriptome response of the endometrium to SCNT embryos (produced from five different donor cell cultures) as compared to embryos derived from in vitro fertilization (IVF). SCNT embryos and IVF embryos were cultured under identical conditions to the blastocyst stage (Day 8) and transferred to recipients. The recipients were slaughtered at day 18 of pregnancy and the uterus was recovered. Pregnancy was verified by the presence of at least one normally developed embryo. Transcriptome profiling of endometrium samples using a custom cDNA microarray covering transcripts expressed in the endometrium and/or oviduct epithelium revealed 58 transcripts that were differently abundant between endometrium samples from SCNT vs. IVF pregnancies. Prominent examples are NR2F2 (encoding the orphan nuclear receptor COUP-TFII) and GJA1 (encoding connexin 43). Both transcripts are known to play important roles in placentation and were significantly less abundant in endometrium from SCNT vs. IVF pregnancies. These findings suggest that placental failure in bovine clone pregnancies may originate from abnormal embryo-maternal communication already in the pre- or peri-implantation period. Endometrium transcriptome profiles may serve as a novel readout to evaluate SCNT embryos for their ability to induce pregnancy with a functional placenta. Keywords: response to different embryos
Project description:Although somatic cell nuclear transfer (SCNT) cloning is more efficient in bovine than in all other species tested so far, there is a high rate of pregnancy failure that has been linked to structural and functional abnormalities of the placenta. We tested the hypothesis that these changes may originate from disturbed embryo-maternal interactions in the pre-implantation period. Therefore, we evaluated the transcriptome response of the endometrium to SCNT embryos (produced from five different donor cell cultures) as compared to embryos derived from in vitro fertilization (IVF). SCNT embryos and IVF embryos were cultured under identical conditions to the blastocyst stage (Day 8) and transferred to recipients. The recipients were slaughtered at day 18 of pregnancy and the uterus was recovered. Pregnancy was verified by the presence of at least one normally developed embryo. Transcriptome profiling of endometrium samples using a custom cDNA microarray covering transcripts expressed in the endometrium and/or oviduct epithelium revealed 58 transcripts that were differently abundant between endometrium samples from SCNT vs. IVF pregnancies. Prominent examples are NR2F2 (encoding the orphan nuclear receptor COUP-TFII) and GJA1 (encoding connexin 43). Both transcripts are known to play important roles in placentation and were significantly less abundant in endometrium from SCNT vs. IVF pregnancies. These findings suggest that placental failure in bovine clone pregnancies may originate from abnormal embryo-maternal communication already in the pre- or peri-implantation period. Endometrium transcriptome profiles may serve as a novel readout to evaluate SCNT embryos for their ability to induce pregnancy with a functional placenta. Keywords: response to different embryos Nineteen German Fleckvieh (Simmental) heifers were slaughtered at day 18 of pregnancy. Cycle-synchronized recipient heifers received either IVP or SCNT embryos at day 7 of the estrous cycle. Animals were slaughtered at day 18. Endometrial (intercaruncular) tissue samples were obtained from 10 pregnant animals after transfer of IVP embryos and from 9 pregnant animals after transfer of SCNT embryos.
Project description:Somatic cell nuclear transfer (SCNT) into an enucleated oocyte can reprogram a differentiated nucleus to a totipotent state. However, the time course of transcriptional reprogramming has not been determined. To monitor the inactivation of somatic genes after SCNT in the bovine model system, we determined transcript levels of 159 genes highly expressed in fetal fibroblast nuclear donor cells, but not in metaphase II recipient oocytes. For 18 of these genes significantly higher transcript levels were found in four-cell SCNT embryos compared with four-cell embryos derived by in vitro fertilization (IVF), indicating incomplete silencing of somatic genes at this stage. RNA sequencing revealed that nearly 600 genes with no transcripts in oocytes were activated in eight-cell IVF embryos, in agreement with major embryonic genome activation (EGA). De novo transcription in SCNT embryos was delayed (16 genes before the 16-cell stage, 300 and >800 genes at the 16-cell and blastocyst stages). Intron-containing primary transcripts as another option to detect embryonic gene transcription revealed activation of >2,200 genes in IVF embryos at the eight-cell stage, while only 828 genes were activated in SCNT embryos. At the 16-cell stage, a higher number of activated genes was found in SCNT (1,917) than in IVF embryos (738). Self-organizing tree algorithm clustering confirmed that in SCNT embryos transcription of genes that are normally activated during major EGA is delayed. Our study provides detailed insight into the timing of genome activation in cloned embryos that is substantially different from IVF embryos in spite of similar developmental kinetics.
Project description:Somatic cell nuclear transfer (SCNT) into an enucleated oocyte can reprogram a differentiated nucleus to a totipotent state. However, the time course of transcriptional reprogramming has not been determined. To monitor the inactivation of somatic genes after SCNT in the bovine model system, we determined transcript levels of 159 genes highly expressed in fetal fibroblast nuclear donor cells, but not in metaphase II recipient oocytes. For 18 of these genes significantly higher transcript levels were found in four-cell SCNT embryos compared with four-cell embryos derived by in vitro fertilization (IVF), indicating incomplete silencing of somatic genes at this stage. RNA sequencing revealed that nearly 600 genes with no transcripts in oocytes were activated in eight-cell IVF embryos, in agreement with major embryonic genome activation (EGA). De novo transcription in SCNT embryos was delayed (16 genes before the 16-cell stage, 300 and >800 genes at the 16-cell and blastocyst stages). Intron-containing primary transcripts as another option to detect embryonic gene transcription revealed activation of >2,200 genes in IVF embryos at the eight-cell stage, while only 828 genes were activated in SCNT embryos. At the 16-cell stage, a higher number of activated genes was found in SCNT (1,917) than in IVF embryos (738). Self-organizing tree algorithm clustering confirmed that in SCNT embryos transcription of genes that are normally activated during major EGA is delayed. Our study provides detailed insight into the timing of genome activation in cloned embryos that is substantially different from IVF embryos in spite of similar developmental kinetics.