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Current Opinion in Cell Biology Jun 2020The fusion of two transcriptionally silent gametes, egg and sperm, generates a totipotent zygote that activates zygotic transcription to support further development.... (Review)
Review
The fusion of two transcriptionally silent gametes, egg and sperm, generates a totipotent zygote that activates zygotic transcription to support further development. Although the molecular details of zygotic genome activation (ZGA) are not well understood in most species, an emerging concept is that one or more pioneer transcription factors trigger zygotic transcription. Concomitantly, extensive changes in 3D chromatin organization occur during development. In this review, we discuss recent advances in understanding when and how genome architecture emerges in early metazoan embryos, how the zygotic genome is activated, and how these events might be coordinated. We also highlight some of the unknowns that may be critical to address in the future.
Topics: Animals; Chromatin; Embryonic Development; Gene Expression Regulation, Developmental; Genome; Transcription Factors; Zygote
PubMed: 32220807
DOI: 10.1016/j.ceb.2020.02.002 -
Genes Oct 2022The 3D chromatin structure within the nucleus is important for gene expression regulation and correct developmental programs. Recently, the rapid development of... (Review)
Review
The 3D chromatin structure within the nucleus is important for gene expression regulation and correct developmental programs. Recently, the rapid development of low-input chromatin conformation capture technologies has made it possible to study 3D chromatin structures in gametes, zygotes and early embryos in a variety of species, including flies, vertebrates and mammals. There are distinct 3D chromatin structures within the male and female gametes. Following the fertilization of male and female gametes, fertilized eggs undergo drastic epigenetic reprogramming at multi levels, including the 3D chromatin structure, to convert the terminally differentiated gamete state into the totipotent state, which can give rise to an individual. However, to what extent the 3D chromatin structure reorganization is evolutionarily conserved and what the underlying mechanisms are for the tremendous reorganization in early embryos remain elusive. Here, we review the latest findings on the 3D chromatin structure reorganization during embryogenesis, and discuss the convergent and divergent reprogramming patterns and key molecular mechanisms for the 3D chromatin structure reorganization from gametes to embryos in different species. These findings shed light on how the 3D chromatin structure reorganization contribute to embryo development in different species. The findings also indicate the role of the 3D chromatin structure on the acquisition of totipotent developmental potential.
Topics: Animals; Male; Female; Germ Cells; Chromatin; Embryonic Development; Zygote; Cell Nucleus; Mammals
PubMed: 36292750
DOI: 10.3390/genes13101864 -
Biology of Reproduction Apr 2020Alternative splicing (AS) of mRNA precursors allows the synthesis of multiple mRNAs from a single primary transcript, significantly expanding the information content and...
Alternative splicing (AS) of mRNA precursors allows the synthesis of multiple mRNAs from a single primary transcript, significantly expanding the information content and regulatory possibilities of higher eukaryotic genomes. During mammalian development, AS drives certain decisive changes in different physiological processes. As development progresses, the maternal-to-zygotic transition (MZT) will trigger two processes: elimination of a subset of maternal mRNA and transcription of the zygote genome begins. Recent high-throughput technological advancements have facilitated genome-wide AS, whereas its analysis in mouse oocyte transition to the zygote stage has not been reported. We present a high-resolution global analysis of AS transitions and discovered extensive AS transitions between mouse oocyte and zygote. The difference of AS patterns was further confirmed using reverse transcription-polymerase chain reaction analysis. Many genes with specific AS events in mouse oocytes are differentially expressed between oocyte and zygote, but only a few genes with specific AS events in zygote are differentially expressed between oocyte and zygote. We provide a landscape of AS events in mouse oocyte and zygote. Our results advance the understanding of AS transitions during mouse fertilization and its potential functions for MZT and further development.
Topics: Alternative Splicing; Animals; Embryo, Mammalian; Embryonic Development; Female; Gene Expression Regulation; Genome-Wide Association Study; Male; Mice; Mice, Inbred C57BL; Oocytes; Protein Isoforms; RNA, Messenger; Zygote
PubMed: 31950147
DOI: 10.1093/biolre/ioaa004 -
International Journal of Molecular... Jan 2021The maternal-to-zygotic transition (MZT), which controls maternal signaling to synthesize zygotic gene products, promotes the preimplantation development of mouse...
The maternal-to-zygotic transition (MZT), which controls maternal signaling to synthesize zygotic gene products, promotes the preimplantation development of mouse zygotes to the two-cell stage. Our previous study reported that mouse granzyme g (Gzmg), a serine-type protease, is required for the MZT. In this study, we further identified the maternal factors that regulate the promoter activity in the zygote to the two-cell stage of mouse embryos. A full-length promoter from mouse genomic DNA, FL-p (-1696~+28 nt), was cloned, and four deletion constructs of this promoter, Δ1-p (-1369~+28 nt), Δ2-p (-939~+28 nt), Δ3-p (-711~+28 nt) and Δ4-p (-417~+28 nt), were subsequently generated. Different-sized promoters were used to perform promoter assays of mouse zygotes and two-cell stage embryos. The results showed that Δ4-p promoted the highest expression level of the enhanced green fluorescent protein (EGFP) reporter in the zygotes and two-cell embryos. The data suggested that time-specific transcription factors upregulated by binding cis-elements in the -417~+28-nt promoter region. According to the results of the promoter assay, the transcription factor binding sites were predicted and analyzed with the JASPAR database, and two transcription factors, signal transducer and activator of transcription 3 (STAT3) and GA-binding protein alpha (GABPα), were identified. Furthermore, STAT3 and GABPα are expressed and located in zygote pronuclei and two-cell nuclei were confirmed by immunofluorescence staining; however, only STAT3 was recruited to the mouse zygote pronuclei and two-cell nuclei injected with the Δ4-p reporter construct. These data indicated that STAT3 is a maternal transcription factor and may upregulate to promote the MZT. Furthermore, treatment with a STAT3 inhibitor, S3I-201, caused mouse embryonic arrest at the zygote and two-cell stages. These results suggest that STAT3, a maternal protein, is a critical transcription factor and regulates transcription activity in preimplantation mouse embryos. It plays an important role in the maternal-to-zygotic transition during early embryonic development.
Topics: Animals; Blastocyst; Cell Nucleus; Embryonic Development; Female; Gene Expression Regulation, Developmental; Granzymes; Green Fluorescent Proteins; Male; Mice; Mice, Inbred ICR; Pregnancy; Promoter Regions, Genetic; STAT3 Transcription Factor; Transcription Factors; Transcriptional Activation; Zygote
PubMed: 33466434
DOI: 10.3390/ijms22010460 -
STAR Protocols Mar 2023Cattle embryos represent a useful model for understanding parts of human embryogenesis due to various biological similarities. We describe a protocol to mature and...
Cattle embryos represent a useful model for understanding parts of human embryogenesis due to various biological similarities. We describe a protocol to mature and fertilize bovine oocytes followed by culture of resulting presumptive zygotes up until the blastocyst stage. Our protocol features a unique procedure for washing and moving oocytes and zygotes between their respective dishes using a cell strainer. A thorough troubleshooting section will help users optimize embryo development with cleavage and blastocyst rates exceeding 70% and 20%, respectively. For complete details on the use and execution of this protocol, please refer to Wooldridge and Ealy (2019)..
Topics: Cattle; Animals; Humans; Embryo, Mammalian; Embryonic Development; Zygote; Blastocyst; Oocytes
PubMed: 36520625
DOI: 10.1016/j.xpro.2022.101924 -
Nature Cell Biology Jan 2023
Topics: Active Transport, Cell Nucleus; Embryonic Development; Zygote; Gene Expression Regulation, Developmental
PubMed: 36650379
DOI: 10.1038/s41556-022-01080-x -
The Keio Journal of Medicine Jun 2020We present the most recent research results on the creation of pigs that can accept human cells. Pigs in which grafted human cells can flourish are essential for studies... (Review)
Review
We present the most recent research results on the creation of pigs that can accept human cells. Pigs in which grafted human cells can flourish are essential for studies of the production of human organs in the pig and for verification of the efficacy of cells and tissues of human origin for use in regenerative therapy. First, against the background of a worldwide shortage of donor organs, the need for future medical technology to produce human organs for transplantation is discussed. We then describe proof-of-concept studies in small animals used to produce human organs. An overview of the history of studies examining the induction of immune tolerance by techniques involving fertilized animal eggs and the injection of human cells into fetuses or neonatal animals is also presented. Finally, current and future prospects for producing pigs that can accept human cells and tissues for experimental purposes are discussed.
Topics: Animals; Animals, Genetically Modified; Animals, Newborn; Bioreactors; Blastocyst; Embryo Transfer; Fetus; Humans; Immune Tolerance; Induced Pluripotent Stem Cells; Organ Transplantation; Regenerative Medicine; Swine; Transplantation, Heterologous; Zygote
PubMed: 31391348
DOI: 10.2302/kjm.2019-0006-OA -
The Journal of Reproduction and... Apr 2022The zygotic genome is transcriptionally silent immediately after fertilization. In mice, initial activation of the zygotic genome occurs in the middle of the one-cell... (Review)
Review
The zygotic genome is transcriptionally silent immediately after fertilization. In mice, initial activation of the zygotic genome occurs in the middle of the one-cell stage. At the mid-to-late two-cell stage, a burst of gene activation occurs after the second round of DNA replication, and the profile of transcribed genes changes dramatically. These two phases of gene activation are called minor and major zygotic gene activation (ZGA), respectively. As they mark the beginning of the gene expression program, it is important to elucidate gene expression regulation during these stages. This article reviews the outcomes of studies that have clarified the profiles and regulatory mechanisms of ZGA.
Topics: Animals; DNA Replication; Embryonic Development; Gene Expression Regulation, Developmental; Genome; Mice; Transcriptional Activation; Zygote
PubMed: 35034936
DOI: 10.1262/jrd.2021-129 -
Nature Communications Jun 2023Acquisition of new stem cell fates relies on the dissolution of the prior regulatory network sustaining the existing cell fates. Currently, extensive insights have been...
Acquisition of new stem cell fates relies on the dissolution of the prior regulatory network sustaining the existing cell fates. Currently, extensive insights have been revealed for the totipotency regulatory network around the zygotic genome activation (ZGA) period. However, how the dissolution of the totipotency network is triggered to ensure the timely embryonic development following ZGA is largely unknown. In this study, we identify the unexpected role of a highly expressed 2-cell (2C) embryo specific transcription factor, ZFP352, in facilitating the dissolution of the totipotency network. We find that ZFP352 has selective binding towards two different retrotransposon sub-families. ZFP352 coordinates with DUX to bind the 2C specific MT2_Mm sub-family. On the other hand, without DUX, ZFP352 switches affinity to bind extensively onto SINE_B1/Alu sub-family. This leads to the activation of later developmental programs like ubiquitination pathways, to facilitate the dissolution of the 2C state. Correspondingly, depleting ZFP352 in mouse embryos delays the 2C to morula transition process. Thus, through a shift of binding from MT2_Mm to SINE_B1/Alu, ZFP352 can trigger spontaneous dissolution of the totipotency network. Our study highlights the importance of different retrotransposons sub-families in facilitating the timely and programmed cell fates transition during early embryogenesis.
Topics: Animals; Mice; Embryonic Development; Gene Expression Regulation, Developmental; Retroelements; Solubility; Transcription Factors; Zygote
PubMed: 37339952
DOI: 10.1038/s41467-023-39344-1 -
Molecular Reproduction and Development Mar 2020The union between a sperm and an egg nucleus in egg fertilization is necessary to mix genetic materials to create a new diploid genome for the next generation. In most... (Review)
Review
The union between a sperm and an egg nucleus in egg fertilization is necessary to mix genetic materials to create a new diploid genome for the next generation. In most animals, only one sperm is incorporated into the egg (monospermy), but several animals exhibit physiological polyspermy in which several sperms enter the egg during normal fertilization. However, only one sperm nucleus forms the zygote nucleus with the egg nucleus, even in a polyspermic egg. The cellular and molecular mechanisms involved in the selection of sperm nuclei in the egg cytoplasm have been well investigated in urodele amphibians. The principal sperm nucleus develops a larger sperm aster and contacts the egg nucleus to form a zygote nucleus, whereas other accessory sperm nuclei are unable to approach the egg nucleus. The diploid zygote nucleus induces cleavage and participates in embryonic development, whereas the accessory sperm nuclei undergo pyknosis and degenerate. We propose several models to account for the mechanisms of the selection of one sperm nucleus and the degeneration of accessory sperm nuclei. The roles of physiological polyspermy in animal reproduction are discussed by comparison with other polyspermic species.
Topics: Amphibians; Animals; Cell Nucleus; Cytoplasm; Diploidy; Female; Genome; Male; Oocytes; Sperm-Ovum Interactions; Spermatozoa; Zygote
PubMed: 31310413
DOI: 10.1002/mrd.23235