scholarly journals Chromatin remodeling in bovine embryos indicates species-specific regulation of genome activation

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Michelle M. Halstead ◽  
Xin Ma ◽  
Chuan Zhou ◽  
Richard M. Schultz ◽  
Pablo J. Ross
Keyword(s):  
Preimplantation Development ◽  
Open Chromatin ◽  
Bovine Embryos ◽  
Embryonic Genome ◽  
Epigenetic Remodeling ◽  
Profile Changes ◽  
Specific Regulation ◽  
Species Specific ◽  
Genome Activation ◽  
Cross Species Comparison

Abstract The shift from maternal to embryonic control is a critical developmental milestone in preimplantation development. Widespread transcriptomic and epigenetic remodeling facilitate this transition from terminally differentiated gametes to totipotent blastomeres, but the identity of transcription factors (TF) and genomic elements regulating embryonic genome activation (EGA) are poorly defined. The timing of EGA is species-specific, e.g., the timing of murine and human EGA differ significantly. To deepen our understanding of mammalian EGA, here we profile changes in open chromatin during bovine preimplantation development. Before EGA, open chromatin is enriched for maternal TF binding, similar to that observed in humans and mice. During EGA, homeobox factor binding becomes more prevalent and requires embryonic transcription. A cross-species comparison of open chromatin during preimplantation development reveals strong similarity in the regulatory circuitry underlying bovine and human EGA compared to mouse. Moreover, TFs associated with murine EGA are not enriched in cattle or humans, indicating that cattle may be a more informative model for human preimplantation development than mice.

scholarly journals Chromatin remodeling in bovine embryos indicates species-specific regulation of genome activation

2019 ◽  
Author(s):  
Michelle M Halstead ◽  
Xin Ma ◽  
Richard M Schultz ◽  
Pablo J Ross
Keyword(s):  
Chromatin Remodeling ◽  
Preimplantation Embryos ◽  
Open Chromatin ◽  
Developmental Transitions ◽  
Embryonic Genome ◽  
Maternal To Zygotic Transition ◽  
Specific Regulation ◽  
Species Specific ◽  
Genome Activation ◽  
Accessible Chromatin

AbstractThe maternal-to-zygotic transition (MZT) is underpinned by wide-spread transcriptomic and epigenomic remodeling that facilitates totipotency acquisition. Factors regulating MZT vary across species and differences in timing of developmental transitions and motif enrichment at accessible chromatin between human and mouse embryos suggest a distinct regulatory circuitry. Profiling accessible chromatin in bovine preimplantation embryos—timing of developmental transitions in bovine closely resembles that in human—indicated that prior to embryonic genome activation (EGA) accessible chromatin is enriched in maternal transcription factor recognition sites, e.g., CTCF, KLFs, NFY, and SP1, echoing observations in humans and mice, and suggesting that a conserved set of maternal factors regulate chromatin remodeling prior to EGA. In contrast, open chromatin established during EGA was primarily enriched for homeobox motifs and showed remarkable similarities between cattle and humans, indicating that cattle could be a more relevant model for human preimplantation development than mice.

69 GLOBAL H3k9ac AND H3k27me3 EXPRESSION IN BLASTOMERES FROM 8- TO 16-CELL STAGE BOVINE EMBRYOS

2014 ◽  
Vol 26 (1) ◽  
pp. 148
Author(s):  
C. S. Oliveira ◽  
N. Z. Saraiva ◽  
L. Z. Oliveira ◽  
R. V. Serapião ◽  
M. R. de Lima ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Histone Modifications ◽  
Pearson Correlation ◽  
Developmental Competence ◽  
Bovine Embryos ◽  
Cell Stage ◽  
Embryonic Genome Activation ◽  
Embryonic Genome ◽  
Group A ◽  
Genome Activation

Embryonic genome activation is a crucial step in early embryo development, and is accompanied by a dramatic change in the epigenetic profile of blastomeres. Histone modifications related to euchromatin and heterochromatin can be important parameters to infer developmental competence, as they are affected by manipulation and environmental stress conditions. The aim of this study was to characterise permissive (H3k9ac) and repressive (H3k27me3) histone modifications during the embryonic genome activation cell cycle in bovine embryos, regarding correlation between those marks and variance among blastomeres. For that, bovine embryos were produced by IVF and cultured in SOF medium supplemented with 5 mg mL–1 of BSA and 2.5% FCS in 5% O2 in an air atmosphere for 5 days (70 h after IVF). The 8 to 16 cell embryos were fixed in 4% paraformaldehyde and submitted to H3k9ac and H3k27me3 immunofluorescence assay (mouse anti-H3K9ac monoclonal antibody, 1 : 200; Sigma; rabbit anti-H3k27me3 monoclonal antibody, 1 : 200; Upstate, Charlottesville, VA, USA). Nuclei were counterstained with Hoechst 33342. Images of each embryo were captured (AxioCam, Carl Zeiss, São Paulo, Brazil) and measured for nuclear fluorescence intensity in each blastomere using Adobe Photoshop CS3 (Adobe Systems, San Jose, CA, USA). Mean levels were compared using the Mann-Whitney test and variances were compared using F-test (SAS 9.1, SAS Institute Inc., Cary, NC, USA; P = 0.05). We evaluated 2 replicates and 12 embryos during the transition from the 8 to 16 cell stages, totaling 169 blastomeres. Global H3k27me3 levels varied accordingly to H3k9ac levels, as indicated by a high Pearson correlation coefficient (r = 0.913). Levels of each blastomere were normalized to the lowest level obtained within each embryo. Some embryos displayed a high variation between blastomeres, and, for further analysis, we divided the embryos into groups: group A for embryos that presented similar H3k9ac levels between blastomeres (8 embryos, 66%), and group B for embryos that exhibited higher heterogeneity between blastomeres (at least 2 blastomeres presenting a 2-fold increase compared to the lowest blastomere; 4 embryos, 33%). Mean H3k9ac and H3k27me3 normalized levels were lower for group A [H3k9ac: 1.35 ± 0.29 (A), 1.94 ± 1.02* (B); H3k27me3: 1.33 ± 0.24 (A), 1.99 ± 0.77 (B)], and group A displayed lower variance values (H3k9ac: 0.07 (A), 1.05* (B); H3k27me3: 0.06 (A), 0.60 (B)]. Within each embryo, blastomeres were sorted in ascending order for H3k9ac level (1 to 16), and compared between groups A and B. We detected that mean levels differed (P < 0.05) between groups from blastomere 9 to 16 for H3k9ac and 10 to 16 for H3k27me3. Therefore, in 8- to 16-cell stage embryos, the H3k27me3 repressive mark is highly correlated with the H3k9ac permissive mark. Also, our results describe the presence of 2 distinguishable populations of bovine embryos at this stage, considering their epigenetic status. One population presented similar levels of repressive and permissive marks among blastomeres, whereas the second one displayed a remarkable variation among their blastomeres. This observation should be further studied, as it might reflect distinct cleavage pattern embryos and blastomere competence. The authors acknowledge FAPESP, FAPERJ and CNPq for financial support.

The role of RNA-polymerase II transcription in embryonic nucleologenesis by bovine embryos

Biologia ◽  
2010 ◽  
Vol 65 (3) ◽  
Author(s):  
Mária Kovalská ◽  
Ida Petrovičová ◽  
František Strejček ◽  
Marian Adamkov ◽  
Erika Halašová ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
De Novo ◽  
Control Group ◽  
Bovine Embryos ◽  
Embryonic Genome Activation ◽  
Embryonic Genome ◽  
Autoradiographic Labeling ◽  
Genome Activation

AbstractThe early stages of embryonic development are maternally driven. As development proceeds, maternally inherited informational molecules decay, and embryogenesis becomes dependent on de novo synthesized RNAs of embryonic genome. The aim of the present study is to investigate the role of de novo transcription in the development of embryos during embryonic genome activation. Autoradiography for detection of transcriptional activity and transmission electron microscopy were applied in in vitro produced bovine embryos cultured to the late 8-cell stage with or without (control group) α-amanitin, specific inhibitor of RNA-polymerases II and III transcription. The α-amanitin (AA) groups presented three sets of embryos cultivated with AA in different time intervals (6, 9 and 12 h). In control group, nucleoplasm and nucleolar structures displayed strong autoradiographic labeling and showed initial development of fibrillo-granular nucleoli. In α-amanitin groups, lack of autoradiographic labeling and disintegrated nucleolus precursor bodies (NPBs) stage were observed. Inhibition of RNA polymerase II (RNA pol II) already in the early phases of embryonic genome activation has detrimental effect on nucleolar formation and embryo survival, what was shown for the first time.

90 TRANSCRIPTION OF USP9Y AND ZFY IN DEVELOPING AND ARRESTED BOVINE EMBRYOS IN VITRO

2013 ◽  
Vol 25 (1) ◽  
pp. 193
Author(s):  
J. Caudle ◽  
C. K. Hamilton ◽  
F. A. Ashkar ◽  
W. A. King
Keyword(s):  
Embryo Development ◽  
Blastocyst Stage ◽  
Early Embryo ◽  
Bovine Embryos ◽  
Cell Stage ◽  
Male Embryo ◽  
Male Development ◽  
Embryonic Genome ◽  
Genome Activation

Sexual dimorphisms such as differences in growth rate and metabolism have been observed in the early embryo, suggesting that sex chromosome-linked gene expression may play an active role in early embryo development. Furthermore, in vitro sex ratios are often skewed toward males, indicating that Y-linked genes may benefit development. While little attention has been paid to the Y chromosome, expression of some Y-linked genes such as SRY and ZFY has been identified in the early embryo, and only a few studies have systematically examined early stages. Identification of transcripts of Y-linked genes in the early embryo may provide insights into male development and provide markers of embryonic genome activation in male embryos. The objectives of this study were i) to examine the timing of transcription of 2 Y chromosome-linked genes involved with sperm production and male development, ubiquitin-specific peptidase 9 (USP9Y) and zinc finger protein (ZFY), in in vitro-produced bovine embryos from the 2-cell stage to the blastocyst stage and ii) to determine if USP9Y and ZFY transcripts are present in in vitro-produced embryos arrested at the 2- to 8-cell stages. To examine the chronology of transcription of these genes, pools of 30 embryos for each developmental stage, 2-cell, 4-cell, 8-cell, 16-cell, morula, and blastocyst, were produced by bovine standard in vitro embryo production (Ashkar et al. 2010 Hum. Reprod. 252, 334–344) using semen from a single bull. Pools of 30 were used to balance sex ratios and to account for naturally arresting embryos. Embryos for each developmental stage were harvested and snap frozen. Total RNA was extracted from each pool, reverse transcribed to cDNA and by using PCR, and transcripts of USP9Y and ZFY were detected as positive or negative. In addition pools of 30 embryos arrested at the 2- to 8-cell stage harvested 7 days after IVF were processed and analysed in the same way to determine if transcripts from the Y chromosomes are present in developmentally arrested embryos. Transcripts of USP9Y and ZFY were detected in the pooled embryos from the 8-cell stage through to the blastocyst stage, but none were detected in the 2-cell or 4-cell pools. Transcripts of ZFY were detected in the arrested 2- to 8-cell embryo pool, but transcripts of USP9Y were not detected. Given that these Y genes begin expression at the 8-cell stage, coincident with embryonic genome activation, it was concluded that these genes may be important for early male embryo development. Furthermore, the results suggest that arrested embryos that have stopped cleaving before the major activation of the embryonic genome are still capable of transcribing at least some of these genes. The absence of USP9Y transcripts in the arrested embryos suggests that it may be important for early male embryo development. Funding was provided by NSERC, the CRC program, and the OVC scholarship program.

Gene expression in the in vitro-produced preimplantation bovine embryos

Zygote ◽  
2007 ◽  
Vol 15 (4) ◽  
pp. 355-367 ◽  
Author(s):  
H. Badr ◽  
G. Bongioni ◽  
A.S.S. Abdoon ◽  
O. Kandil ◽  
R. Puglisi
Keyword(s):  
Gene Expression ◽  
Expression Pattern ◽  
Gene Expression Profile ◽  
Expression Profile ◽  
Gene Expression Pattern ◽  
Bovine Embryos ◽  
Embryonic Genome ◽  
Altered Gene ◽  
Genome Activation

SummaryRecent studies have demonstrated the relevance of a gene expression profile as a clinically important key feature determining embryo quality during the in vitro preimplantation period. Although the oocyte origin can play a crucial role in blastocyst yield, the postfertilization culture period has a profound effect in determining the blastocyst quality with particular regard to the relative abundance of many developmentally and clinically important candidate genes. During the preimplantation period, the embryo undergoes several morphogenetic developmental events including oocyte maturation, minor and major forms of embryonic genome activation and transition of transcription from maternal to embryonic control. The effect of an altered gene expression pattern on the in vitro-produced bovine embryos, particularly when cultured under suboptimal conditions, was reflected by the occurrence of clinically important phenomena like apoptosis and the large offspring syndrome. This review attempts to focus on the morphogenetic embryo development and gene expression profile in the in vitro-produced bovine embryos, with special emphasis on the different parameters that may alter gene expression pattern during the critical period of in vitro culture. The effect of the in vitro system, as reflected by some clinically important phenomena like apoptosis, is also discussed.

The stage of embryonic genome activation in bovine embryos following in vitro fertilization

1999 ◽  
Vol 51 (1) ◽  
pp. 188 ◽  
Author(s):  
E-H Park ◽  
R-C Chian ◽  
H-M Chung ◽  
J-G Lim ◽  
J-J Ko ◽  
...  
Keyword(s):  
In Vitro Fertilization ◽  
Bovine Embryos ◽  
Vitro Fertilization ◽  
Embryonic Genome Activation ◽  
Embryonic Genome ◽  
Genome Activation

Zygotic and embryonic gene expression in cow: a review of timing and mechanisms of early gene expression as compared with other species

Zygote ◽  
2000 ◽  
Vol 8 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Erdogan Memili ◽  
Neal L. First
Keyword(s):  
Gene Expression ◽  
Early Embryogenesis ◽  
Early Gene ◽  
Modern Biology ◽  
Cell Stage ◽  
Zygotic Transcription ◽  
Embryonic Genome ◽  
Core Histones ◽  
Species Specific ◽  
Genome Activation

Early embryonic development is largely dependent on maternal RNAs and proteins synthesised during oogenesis. Zygotic transcription is an essential event that occurs at a species-specific time after fertilisation. In the absence of zygotic transcription the embryo dies since it can no longer support requirements for successful embryo development. Molecular genetics of gene expression during early embryogenesis, especially in the bovine species, remain one of the unsolved questions in modern biology. Earlier studies suggested that embryonic transcription in cattle begins at the late 4-cell or 8-cell stage. However, more recent studies suggest that bovine zygotes and 2-cell embryos are both transcriptionally and translationally active. Moreover, changes in chromatin structure due to acetylation of core histones and DNA replication play important roles in the regulation of zygotic/embryonic gene expression. This review will summarise results of recent studies about the timing and mechanisms of zygotic/embryonic gene expression in cattle. In addition, terminology in the literature regarding gene expression during early embryogenesis will be clarified. These terminologies include: ‘zygotic/embryonic gene expression’, ‘maternal to embryonic transition in control of development (MET)’ and ‘zygotic/embryonic genome activation (ZEGA)’.

67 CORRELATION OF ARCHITECTURAL AND FUNCTIONAL REPROGRAMMING OF NUCLEI DURING EMBRYONIC GENOME ACTIVATION OF EARLY BOVINE EMBRYOS GENERATED BY IVF AND SCNT

2014 ◽  
Vol 26 (1) ◽  
pp. 147
Author(s):  
J. Popken ◽  
D. Koehler ◽  
A. Brero ◽  
A. Wuensch ◽  
T. Thormeyer ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Nuclear Architecture ◽  
Nuclear Space ◽  
Structured Illumination ◽  
Bovine Embryos ◽  
Structured Illumination Microscopy ◽  
Nuclear Compartment ◽  
Nuclear Interior ◽  
Embryonic Genome ◽  
Genome Activation

Development of mammalian pre-implantation embryos provides an excellent model to explore interactions of nuclear organisation and nuclear functions. Based on light optical sectioning with confocal laser scanning microscopy and structured illumination microscopy, we performed a quantitative three-dimensional image analysis of nuclei in early bovine embryos generated by in vitro fertilization (IVF) and somatic cell nuclear transfer (SCNT) of bovine fibroblast nuclei. The same sequence of changes was observed in nuclei of both IVF and SCNT embryos during embryonic genome activation (EGA) is that typically achieved in embryos between 8 and 16 cells. In both pre-EGA IVF and SCNT embryos, chromosome territories (CT) were assembled as spatially distinct entities at the nuclear periphery, whereas the nuclear interior was typically occupied by a mostly chromatin free lacuna enriched with splicing factors. Detection of H3K4m3 demonstrates the presence of transcriptionally competent chromatin before EGA, which was correlated with large-scale movements of CT into the nuclear interior and a several-fold decrease of nuclear volumes. Post-EGA nuclei are characterised by a conventional nuclear architecture with chromatin distributed throughout the nuclear space, heterochromatin enriched with histone markers for transcriptionally silent chromatin beneath the nuclear lamina and around nucleoli, as well as heterochromatin clusters and chromocenters throughout the nuclear interior. Pre- and post-EGA nuclei were recorded with the superior resolution of structured illumination microscopy to allow a quantitative analysis of the nuclear topography of H3K4me3 and RNAP II signals. These signals were highly significantly enriched in the perichromatin region (PR) surrounding the compact, transcriptionally silent interior of megabase-sized chromatin domains, which form the basic structural units of CT. The PR is in direct contact with interchromatin compartment (IC) channels starting at nuclear pores, permeating the nuclear space and harboring nuclear bodies in IC lacunas. Our findings support a model for the functional nuclear architecture based on spatially distinct, but co-aligned three-dimensional networks of an active and an inactive nuclear compartment. The active nuclear compartment is built up from the structurally and functionally interacting IC and PR, whereas the inactive nuclear compartment consists of the compact, transcriptionally silent core of chromatin domain clusters. This work is supported by the DFG (ZA 425/1-3, CR 59/29-2).

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