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Genome architecture and totipotency: An intertwined relation during early embryonic development.

ABSTRACT: Chromosomes are not randomly packed and positioned into the nucleus but folded in higher-order chromatin structures with defined functions. However, the genome of a fertilized embryo undergoes a dramatic epigenetic reprogramming characterized by extensive chromatin relaxation and the lack of a defined three-dimensional structure. This reprogramming is followed by a slow genome refolding that gradually strengthens the chromatin architecture during preimplantation development. Interestingly, genome refolding during early development coincides with a progressive loss of developmental potential suggesting a link between chromatin organization and cell plasticity. In agreement, loss of chromatin architecture upon depletion of the insulator transcription factor CTCF in embryonic stem cells led to the upregulation of the transcriptional program found in totipotent cells of the embryo, those with the highest developmental potential. This essay will discuss the impact of genome folding in controlling the expression of transcriptional programs involved in early development and their plastic-associated features.

SUBMITTER: Olbrich T

PROVIDER: S-EPMC10281046 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Genome architecture and totipotency: An intertwined relation during early embryonic development.

Olbrich Teresa T Ruiz Sergio S

BioEssays : news and reviews in molecular, cellular and developmental biology 20220513 7

Chromosomes are not randomly packed and positioned into the nucleus but folded in higher-order chromatin structures with defined functions. However, the genome of a fertilized embryo undergoes a dramatic epigenetic reprogramming characterized by extensive chromatin relaxation and the lack of a defined three-dimensional structure. This reprogramming is followed by a slow genome refolding that gradually strengthens the chromatin architecture during preimplantation development. Interestingly, genom ...[more]

PMID: 35560026

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Project description:Histone lysine modifications are important epigenetic modifications in early embryonic development. JARID2, which is a member of the jumonji demethylase protein family, is a regulator of early embryonic development and can regulate mouse development and embryonic stem cell (ESC) differentiation by modifying histone lysines. JARID2 can affect early embryonic development by regulating the methylation level of H3K27me3, which is closely related to normal early embryonic development. To investigate the expression pattern of JARID2 and the effect of JARID2-induced H3K27 methylation in bovine oocytes and early embryonic stages, JARID2 mRNA expression and localization were detected in bovine oocytes and early embryos via qRT-PCR and immunofluorescence in the present study. The results showed that JARID2 is highly expressed in the germinal vesicle (GV), MII, 2-cell, 4-cell, 8-cell, 16-cell and blastocyst stages, but the relative expression level of JARID2 in bovine GV oocytes is significantly lower than that at other oocyte/embryonic stages (p < 0.05), and JARID2 is expressed primarily in the nucleus. We next detected the mRNA expression levels of embryonic development-related genes (OCT4, SOX2 and c-myc) after JARID2 knockdown through JARID2-2830-siRNA microinjection to investigate the molecularpathwayunderlying the regulation of H3K27me3 by JARID2 during early embryonic development. The results showed that the relative expression levels of these genes in 2-cell embryos weresignificantly higher than those in the blastocyst stage, and expression levels were significantly increased after JARID2 knockdown. In summary, the present study identified the expression pattern of JARID2 in bovine oocytes and at each early embryonic stage, and the results suggest that JARID2 plays a key role in early embryonic development by regulating the expression of OCT4, SOX2 and c-myc via modification of H3K27me3 expression. This work provides new data for improvements in the efficiency of in vitro embryo culture as well as a theoretical basis for further studying the regulatory mechanisms involved in early embryonic development.

Project description:Objectives: During human in vitro fertilisation (IVF) treatments, embryologists attempt to select the most viable embryos for embryo transfer (ET). Previously, embryos were evaluated based on light microscopic morphological parameters. However, this is currently accomplished by morphokinetic analysis of time-lapse recordings. This technique provides us the opportunity to observe cytoplasmic strings at the blastocyst stage. The aim of this work was to examine the relationship between the presence of cytoplasmic strings (CS) and the embryo viability in human in vitro fertilised embryos. Study design: Herein, we present an evaluation of the morphokinetic data on the development of embryos obtained during IVF treatments performed at the Division of Assisted Reproduction between December 2020 and March 2021. The dynamics of embryo development, embryo morphology, and morphokinetic scores generated by a time-lapse system were compared between the presence of cytoplasmic strings (CS+) and their absence (CS-) at the blastocyst stage. Results: The development of 208 embryos from 78 patients was examined. Moreover, 81.2% of the embryos had CS in the blastocyst stage; 77% of CS existed in embryos created by conventional IVF, while 86% of CS existed in embryos fertilised by intracytoplasmic sperm injection (ICSI) (p = 0.08). A greater number of CS+ embryos developed into a higher quality blastocyst (52.1% vs. 20.5%, p = 0.02). The morphokinetic score values characterising the development of embryos, such as Known Implantation Data Score (KIDScore) and Intelligent Data Analysis (iDAScore), were higher in CS+ groups (KID: 6.1 ± 2.1 vs. 4.7 ± 2.07; iDA: 8.0 ± 1.9 vs. 6.8 ± 2.3, p < 0.01). The dynamics of the early embryo development were similar between the two groups; however, CS+ embryos reached the blastocyst stage significantly earlier (tB: 103.9 h vs. tB: 107.6 h; p = 0.001). Conclusion: Based on our results, the number of embryos with cytoplasmic strings was higher than that without cytoplasmic strings, and its presence is not related to the fertilisation method. These embryos reached the blastocyst stage earlier, and their morphokinetic (KIDScore and iDAScore) parameters were better. All these results suggest that the presence of CS indicates higher embryo viability. The examination of this feature may help us make decisions about the embryos with higher implantation potential.

Dataset Information

Genome architecture and totipotency: An intertwined relation during early embryonic development.

Publications

Genome architecture and totipotency: An intertwined relation during early embryonic development.

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