preimplantation embryo
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2021 ◽  
Vol 12 ◽  
Author(s):  
Zijing Zhang ◽  
Jiawei Xu ◽  
Shijie Lyu ◽  
Xiaoling Xin ◽  
Qiaoting Shi ◽  
...  

The early stages of mammalian embryonic development involve the participation and cooperation of numerous complex processes, including nutritional, genetic, and epigenetic mechanisms. However, in embryos cultured in vitro, a developmental block occurs that affects embryo development and the efficiency of culture. Although the block period is reported to involve the transcriptional repression of maternal genes and transcriptional activation of zygotic genes, how epigenetic factors regulate developmental block is still unclear. In this study, we systematically analyzed whole-genome methylation levels during five stages of sheep oocyte and preimplantation embryo development using single-cell level whole genome bisulphite sequencing (SC-WGBS) technology. Then, we examined several million CpG sites in individual cells at each evaluated developmental stage to identify the methylation changes that take place during the development of sheep preimplantation embryos. Our results showed that two strong waves of methylation changes occurred, namely, demethylation at the 8-cell to 16-cell stage and methylation at the 16-cell to 32-cell stage. Analysis of DNA methylation patterns in different functional regions revealed a stable hypermethylation status in 3′UTRs and gene bodies; however, significant differences were observed in intergenic and promoter regions at different developmental stages. Changes in methylation at different stages of preimplantation embryo development were also compared to investigate the molecular mechanisms involved in sheep embryo development at the methylation level. In conclusion, we report a detailed analysis of the DNA methylation dynamics during the development of sheep preimplantation embryos. Our results provide an explanation for the complex regulatory mechanisms underlying the embryo developmental block based on changes in DNA methylation levels.


2021 ◽  
Author(s):  
◽  
Shicheng Ni

<p>In recent times, cattle embryology has been under the spotlight of investigation due to its apparent economic values. This is especially relevant in the case of New Zealand, owing to its high percentage of livestock export. Specifically, the period of peri-implantation development has been of particular relevance. During this stage, the developing zygote will establish 3 key lineages – epiblast, hypoblast and trophoblast. Previous studies have elucidated that a significant number of embryos die prior to implantation, therefore highlighting the importance of correctly establishing these 3 lineages to overall embryonic survival. However, while embryological stages of the preimplantation embryo have been extensively studied in their eutherian cousin, mice, the molecular regulation of that of cattle remains much less addressed. Whereas the regulation of bovine embryo development is orchestrated by many transcriptional regulators, or genetic regulatory networks (GNP), we aimed to focus our studies on 2 key transcriptional regulators, GATA4 and GATA6. During early embryogenesis, both these transcriptional factors are known molecular regulators that drive the establishment of the hypoblast lineage in mice. By and large, while their respective expression has been documented in cattle embryos, functional studies towards these markers have not yet been performed. Latest advances in molecular biology have given us novel methods to study the mechanism of bovine embryogenesis. To this end, the continuing perfection of CRISPR technologies in the last decade - in particular its delivery through lentiviral vectors, has established an ability to generate stable, targeted knock-out mutants. Therefore, it is aimed in this thesis to design and test lentiviral particles that induce knock-out mutants of GATA4 and GATAT6, to test their efficacy in primary cell cultures (bovine cumulus cells) and to functionally analyse the effect of GATA4 and GATA6 knockdowns in early bovine embryos.</p>


2021 ◽  
Author(s):  
◽  
Shicheng Ni

<p>In recent times, cattle embryology has been under the spotlight of investigation due to its apparent economic values. This is especially relevant in the case of New Zealand, owing to its high percentage of livestock export. Specifically, the period of peri-implantation development has been of particular relevance. During this stage, the developing zygote will establish 3 key lineages – epiblast, hypoblast and trophoblast. Previous studies have elucidated that a significant number of embryos die prior to implantation, therefore highlighting the importance of correctly establishing these 3 lineages to overall embryonic survival. However, while embryological stages of the preimplantation embryo have been extensively studied in their eutherian cousin, mice, the molecular regulation of that of cattle remains much less addressed. Whereas the regulation of bovine embryo development is orchestrated by many transcriptional regulators, or genetic regulatory networks (GNP), we aimed to focus our studies on 2 key transcriptional regulators, GATA4 and GATA6. During early embryogenesis, both these transcriptional factors are known molecular regulators that drive the establishment of the hypoblast lineage in mice. By and large, while their respective expression has been documented in cattle embryos, functional studies towards these markers have not yet been performed. Latest advances in molecular biology have given us novel methods to study the mechanism of bovine embryogenesis. To this end, the continuing perfection of CRISPR technologies in the last decade - in particular its delivery through lentiviral vectors, has established an ability to generate stable, targeted knock-out mutants. Therefore, it is aimed in this thesis to design and test lentiviral particles that induce knock-out mutants of GATA4 and GATAT6, to test their efficacy in primary cell cultures (bovine cumulus cells) and to functionally analyse the effect of GATA4 and GATA6 knockdowns in early bovine embryos.</p>


Author(s):  
Yuanyuan Li ◽  
Ning-Hua Mei ◽  
Gui-Ping Cheng ◽  
Jing Yang ◽  
Li-Quan Zhou

Mitochondrion plays an indispensable role during preimplantation embryo development. Dynamic-related protein 1 (DRP1) is critical for mitochondrial fission and controls oocyte maturation. However, its role in preimplantation embryo development is still lacking. In this study, we demonstrate that inhibition of DRP1 activity by mitochondrial division inhibitor-1, a small molecule reported to specifically inhibit DRP1 activity, can cause severe developmental arrest of preimplantation embryos in a dose-dependent manner in mice. Meanwhile, DRP1 inhibition resulted in mitochondrial dysfunction including decreased mitochondrial activity, loss of mitochondrial membrane potential, reduced mitochondrial copy number and inadequate ATP by disrupting both expression and activity of DRP1 and mitochondrial complex assembly, leading to excessive ROS production, severe DNA damage and cell cycle arrest at 2-cell embryo stage. Furthermore, reduced transcriptional and translational activity and altered histone modifications in DRP1-inhibited embryos contributed to impeded zygotic genome activation, which prevented early embryos from efficient development beyond 2-cell embryo stage. These results show that DRP1 inhibition has potential cytotoxic effects on mammalian reproduction, and DRP1 inhibitor should be used with caution when it is applied to treat diseases. Additionally, this study improves our understanding of the crosstalk between mitochondrial metabolism and zygotic genome activation.


Cell Division ◽  
2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Dongjie Zhou ◽  
Ming-Hong Sun ◽  
Song-Hee Lee ◽  
Xiang-Shun Cui

Abstract Background Reactive oxygen species (ROS) modulator 1 (ROMO1) is a mitochondrial membrane protein that is essential for the regulation of mitochondrial ROS production and redox sensing. ROMO1 regulates ROS generation within cells and is involved in cellular processes, such as cell proliferation, senescence, and death. Our purpose is to investigates the impact of ROMO1 on the mitochondria during porcine embryogenesis. Results We found that high expression of ROMO1 was associated with porcine preimplantation embryo development, indicating that ROMO1 may contribute to the progression of embryogenesis. Knockdown of ROMO1 disrupted porcine embryo development and blastocyst quality, thereby inducing ROS production and decreasing mitochondrial membrane potential. Knockdown of ROMO1 induced mitochondrial dysfunction by disrupting the balance of OPA1 isoforms to release cytochrome c, reduce ATP, and induce apoptosis. Meanwhile, ROMO1 overexpression showed similar effects as ROMO1 KD on the embryos. Overexpression of ROMO1 rescued the ROMO1 KD-induced defects in embryo development, mitochondrial fragmentation, and apoptosis. Conclusions ROMO1 plays a critical role in embryo development by regulating mitochondrial morphology, function, and apoptosis in pigs.


Zygote ◽  
2021 ◽  
pp. 1-7
Author(s):  
Sara Hosseini ◽  
Mohammad Salehi

Summary It has been documented that the inefficacy of round spermatid injection (ROSI) might be caused by abnormal epigenetic modifications. Therefore, this study aimed to evaluate the effect of trichostatin A (TSA) as an epigenetic modifier of preimplantation embryo development in activated ROSI oocytes. Matured oocytes were collected from superovulated female mice. Testes were placed in human tubal fluid medium and masses were then cut into small pieces to disperse spermatogenic cells. Round spermatids were treated with TSA and subsequently injected into oocytes. The expression level of the development-related genes including Oct4, Sox2, Nanog, Dnmt and Hdac transcripts were evaluated using qRT-PCR. Immunohistochemistry was performed to confirm the presence of Oct-4 protein at the blastocyst stage. There was no statistically significant difference in fertilization rate following ROSI/+TSA compared with the non-treated ROSI and intracytoplasmic sperm injection (ICSI) groups. Importantly, TSA treatment increased blastocyst formation from 38% in non-treated ROSI to 68%. The relative expression level of developmentally related genes increased and Dnmt transcripts decreased in ROSI/+TSA-derived embryos, similar to the expression levels observed in the ICSI-derived embryos. In conclusion, our results indicate that spermatid treatment with TSA prior to ROSI would increase the success rate of development to the blastocyst stage and proportion of pluripotent cells.


2021 ◽  
pp. 1-5
Author(s):  
Jason E. Swain

With continued improvements in blastocyst culture, cell sampling approaches, and genetic analysis platforms, the resulting improvements in embryo development and the resolution and accuracy of chromosome analysis have provided valuable insights into the preimplantation embryo. This includes the impact of in vitro culture conditions on chromosomal dynamics. Specifically, through analysis of embryo aneuploidy and mosaicism, a growing number of reports indicate that rates of chromosomal abnormalities can vary between IVF centers. Because differences in mosaicism reflect mitotic errors, this endpoint analysis suggests that IVF laboratory-controlled variables during embryo development may be influencing chromosome separation and segregation. A growing body of literature suggests that culture media may be one variable influencing preimplantation embryo aneuploidy and mosaicism. However, these data are far from definitive in demonstrating cause-and-effect. Whether reported differences may be due to media formulation, use of sequential media or single-step media, or uninterrupted culture approaches is unknown. Importantly, variables directly impacting media performance and embryo development, including pH, temperature, osmolality, and oxygen concentration, must also be considered and make it difficult to isolate the impact of culture media as the sole factor responsible. These IVF laboratory variables will be reviewed and literature suggesting a possible link to mitotic aneuploidy/mosaicism will be discussed.


Andrology ◽  
2021 ◽  
Author(s):  
Jeffrey Hoek ◽  
Sam Schoenmakers ◽  
Linette Duijn ◽  
Sten. P. Willemsen ◽  
Eva S. Marion ◽  
...  

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