DPPA2 and DPPA4 are dispensable for mouse zygotic genome activation and preimplantation development

Genome Activation ◽

How maternal factors in oocytes initiate zygotic genome activation (ZGA) remains elusive in mammals, partly due to the challenge of de novo identification of key factors using scarce materials. The 2-cell (2C) embryo like cells has been widely used as an in vitro model to understand mouse ZGA and totipotency given its expression of a group of 2C embryo-specific genes and its simplicity for genetic manipulation. Recent studies indicate that DPPA2 and DPPA4 are required for establishing the 2C-like state in mouse embryonic stem cells (ESCs) in a DUX-dependent manner. These results suggest that DPPA2 and DPPA4 are essential maternal factors that regulate Dux and ZGA in embryos. By analyzing maternal knockout and maternal-zygotic knockout embryos, we unexpectedly found that DPPA2 and DPPA4 are dispensable for Dux activation, ZGA, and preimplantation development. Our study suggests that 2C-like cells do not fully recapitulate 2-cell embryos in terms of 2C-gene regulation and cautions should be taken when studying ZGA and totipotency using 2C-like cells as the model system.

DPPA2 and DPPA4 are dispensable for mouse zygotic genome activation and preimplantation development

10.1101/2021.08.19.457017 ◽

2021 ◽

Author(s):

Zhiyuan Chen ◽

Zhenfei Xie ◽

Yi Zhang

Keyword(s):

Stem Cells ◽

Embryonic Stem Cells ◽

Embryonic Stem ◽

Preimplantation Development ◽

Dependent Manner ◽

Maternal Factors ◽

Cell Embryo ◽

Genome Activation ◽

How maternal factors in oocytes initiate zygotic genome activation (ZGA) remains elusive. Recent studies indicate that DPPA2 and DPPA4 are required for establishing a 2-cell embryo-like (2C-like) state in mouse embryonic stem cells (ESCs) in a DUX-dependent manner. These results suggest that DPPA2 and DPPA4 are essential maternal factors that regulate Dux and ZGA in embryos. By analyzing maternal knockout and maternal-zygotic knockout embryos, we unexpectedly found that Dux activation, ZGA, and preimplantation development are normal in embryos without DPPA2 or DPPA4. Thus, unlike in ESCs/2C-like cells, DPPA2 and DPPA4 are dispensable for ZGA and preimplantation development.

Maternal Dppa2 and Dppa4 are dispensable for zygotic genome activation but important for offspring survival

Development ◽

10.1242/dev.200191 ◽

2021 ◽

Vol 148 (24) ◽

Author(s):

Oana Kubinyecz ◽

Fatima Santos ◽

Deborah Drage ◽

Wolf Reik ◽

Melanie A. Eckersley-Maslin

Keyword(s):

Null Allele ◽

Embryonic Stem ◽

Offspring Survival ◽

Molecular Events ◽

Genome Activation ◽

Mitotic Chromatin ◽

ABSTRACT Zygotic genome activation (ZGA) represents the initiation of transcription following fertilisation. Despite its importance, we know little of the molecular events that initiate mammalian ZGA in vivo. Recent in vitro studies in mouse embryonic stem cells have revealed developmental pluripotency associated 2 and 4 (Dppa2/4) as key regulators of ZGA-associated transcription. However, their roles in initiating ZGA in vivo remain unexplored. We reveal that Dppa2/4 proteins are present in the nucleus at all stages of preimplantation development and associate with mitotic chromatin. We generated conditional single and double maternal knockout mouse models to deplete maternal stores of Dppa2/4. Importantly, Dppa2/4 maternal knockout mice were fertile when mated with wild-type males. Immunofluorescence and transcriptome analyses of two-cell embryos revealed that, although ZGA took place, there were subtle defects in embryos that lacked maternal Dppa2/4. Strikingly, heterozygous offspring that inherited the null allele maternally had higher preweaning lethality than those that inherited the null allele paternally. Together, our results show that although Dppa2/4 are dispensable for ZGA transcription, maternal stores have an important role in offspring survival, potentially via epigenetic priming of developmental genes.

Transposable Element Dynamics and Regulation during Zygotic Genome Activation in Mammalian Embryos and Embryonic Stem Cell Model Systems

Stem Cells International ◽

10.1155/2021/1624669 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Yixuan Low ◽

Dennis Eng Kiat Tan ◽

Zhenhua Hu ◽

Shawn Ying Xuan Tan ◽

Wee-Wei Tee

Keyword(s):

Cell Model ◽

Embryonic Stem ◽

Model Systems ◽

Specific Class ◽

Mammalian Development ◽

Somatic Tissues ◽

Genome Activation ◽

Transposable elements (TEs) are mobile genetic sequences capable of duplicating and reintegrating at new regions within the genome. A growing body of evidence has demonstrated that these elements play important roles in host genome evolution, despite being traditionally viewed as parasitic elements. To prevent ectopic activation of TE transposition and transcription, they are epigenetically silenced in most somatic tissues. Intriguingly, a specific class of TEs—retrotransposons—is transiently expressed at discrete phases during mammalian development and has been linked to the establishment of totipotency during zygotic genome activation (ZGA). While mechanisms controlling TE regulation in somatic tissues have been extensively studied, the significance underlying the unique transcriptional reactivation of retrotransposons during ZGA is only beginning to be uncovered. In this review, we summarize the expression dynamics of key retrotransposons during ZGA, focusing on findings from in vivo totipotent embryos and in vitro totipotent-like embryonic stem cells (ESCs). We then dissect the functions of retrotransposons and discuss how their transcriptional activities are finetuned during early stages of mammalian development.

Maternal Dppa2 and Dppa4 are dispensable for zygotic genome activation but important for offspring survival

10.1101/2021.09.13.460183 ◽

2021 ◽

Author(s):

Oana Kubinyecz ◽

Fatima Santos ◽

Deborah Drage ◽

Wolf Reik ◽

Melanie A Eckersley-Maslin

Keyword(s):

Null Allele ◽

Embryonic Stem ◽

Offspring Survival ◽

Molecular Events ◽

Genome Activation ◽

Mitotic Chromatin ◽

Zygotic Genome Activation (ZGA) represents the initiation of transcription following fertilisation. Despite its importance in shifting developmental control from primarily maternal stores in the oocyte to the embryo proper, we know little of the molecular events that initiate ZGA in vivo. Recent in vitro studies in mouse embryonic stem cells (ESCs) have revealed Developmental Pluripotency Associated 2 and 4 (Dppa2/4) as key regulators of ZGA-associated transcription. However, their roles in initiating ZGA in vivo remain unexplored. We reveal Dppa2/4 proteins are present in the nucleus at all stages of preimplantation development and associate with mitotic chromatin. We generated single and double maternal knockout mouse models to deplete maternal stores of Dppa2/4. Importantly, while fertile, Dppa2/4 maternal knockout mice had reduced litter sizes, indicating decreased offspring survival. Immunofluorescence and transcriptome analyses of 2-cell embryos revealed while ZGA took place there were subtle defects in embryos lacking maternal Dppa2/4. Strikingly, heterozygous offspring that inherited the null allele maternally had higher preweaning lethality than those that inherited the null allele paternally. Together our results show that while Dppa2/4 are dispensable for ZGA transcription, maternal stores have an important role in offspring survival, potentially via epigenetic priming of developmental genes.

Inhibition of DRP1 Impedes Zygotic Genome Activation and Preimplantation Development in Mice

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.788512 ◽

2021 ◽

Vol 9 ◽

Author(s):

Yuanyuan Li ◽

Ning-Hua Mei ◽

Gui-Ping Cheng ◽

Jing Yang ◽

Li-Quan Zhou

Keyword(s):

Embryo Development ◽

Preimplantation Embryo ◽

Preimplantation Embryos ◽

Dependent Manner ◽

Preimplantation Embryo Development ◽

Cell Embryo ◽

Embryo Stage ◽

Genome Activation ◽

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.

Expression of eukaryotic elongation initiation factor 1A differentially marks zygotic genome activation in biparental and parthenogenetic porcine embryos and correlates with in vitro developmental potential

Reproduction Fertility and Development ◽

10.1071/rd08072 ◽

2008 ◽

Vol 20 (7) ◽

pp. 818 ◽

Cited By ~ 14

Author(s):

Luca Magnani ◽

Christine M. Johnson ◽

Ryan A. Cabot

Keyword(s):

Expression Profile ◽

Initiation Factor ◽

In Vitro Fertilisation ◽

Cell Stage ◽

Developmental Potential ◽

Genome Activation ◽

Parthenogenetic Embryos ◽

Zygotic genome activation (ZGA) is a major event during cleavage development. In vitro manipulation of mammalian embryos (including embryo culture) can result in developmental arrest around the time of ZGA. Eukaryotic elongation initiation factor 1A (eIF1A) has been used as a marker for ZGA in some mammalian species. We hypothesised expression of eIF1A can be used to assess ZGA in the pig; we also hypothesised that the expression profile of eIF1A can be used to assess developmental potential in vitro. The aims of the present study were to determine the expression pattern of eIF1A during porcine cleavage development and to assess its expression levels in embryos of different quality. We used a real-time reverse transcription–polymerase chain reaction assay to quantify eIF1A transcripts at different time points during cleavage development in porcine embryos produced by parthenogenetic activation (PA) and in vitro fertilisation (IVF). We found that eIF1A is activated at the two-cell stage in IVF embryos and at the four-cell stage in PA embryos. We showed that the increase in transcript levels observed in parthenogenetic embryos is dependent on de novo transcription. We found altered levels of eIF1A transcripts in parthenogenetic embryos that presented as either two- or eight-cell embryos 48 h after activation compared with four-cell embryos at the same time point. Our work supports the hypothesis that eIF1A is a marker of porcine ZGA and its expression profile can be used to assess embryo quality.

Zscan4 binds nucleosomal microsatellite DNA and protects mouse two-cell embryos from DNA damage

Science Advances ◽

10.1126/sciadv.aaz9115 ◽

2020 ◽

Vol 6 (12) ◽

pp. eaaz9115 ◽

Cited By ~ 3

Author(s):

Rajini Srinivasan ◽

Nataliya Nady ◽

Neha Arora ◽

Laura J. Hsieh ◽

Tomek Swigut ◽

...

Keyword(s):

Dna Damage ◽

Zinc Finger Protein ◽

Embryonic Stem ◽

Dependent Manner ◽

Developmentally Regulated ◽

Torsional Strain ◽

Genomic Stress ◽

Genomic Regions ◽

Genome Activation

Zinc finger protein Zscan4 is selectively expressed in mouse two-cell (2C) embryos undergoing zygotic genome activation (ZGA) and in a rare subpopulation of embryonic stem cells with 2C-like features. Here, we show that Zscan4 specifically recognizes a subset of (CA)n microsatellites, repeat sequences prone to genomic instability. Zscan4-associated microsatellite regions are characterized by low nuclease sensitivity and high histone occupancy. In vitro, Zscan4 binds nucleosomes and protects them from disassembly upon torsional strain. Furthermore, Zscan4 depletion leads to elevated DNA damage in 2C mouse embryos in a transcription-dependent manner. Together, our results identify Zscan4 as a DNA sequence–dependent microsatellite binding factor and suggest a developmentally regulated mechanism, which protects fragile genomic regions from DNA damage at a time of embryogenesis associated with high transcriptional burden and genomic stress.

Histone variant H2A.Z regulates zygotic genome activation

Nature Communications ◽

10.1038/s41467-021-27125-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Dafne Ibarra-Morales ◽

Michael Rauer ◽

Piergiuseppe Quarato ◽

Leily Rabbani ◽

Fides Zenk ◽

...

Keyword(s):

Rna Polymerase Ii ◽

De Novo ◽

Housekeeping Genes ◽

Histone Variant ◽

Small Subset ◽

Transcription Start Sites ◽

Genome Activation ◽

AbstractDuring embryogenesis, the genome shifts from transcriptionally quiescent to extensively active in a process known as Zygotic Genome Activation (ZGA). In Drosophila, the pioneer factor Zelda is known to be essential for the progression of development; still, it regulates the activation of only a small subset of genes at ZGA. However, thousands of genes do not require Zelda, suggesting that other mechanisms exist. By conducting GRO-seq, HiC and ChIP-seq in Drosophila embryos, we demonstrate that up to 65% of zygotically activated genes are enriched for the histone variant H2A.Z. H2A.Z enrichment precedes ZGA and RNA Polymerase II loading onto chromatin. In vivo knockdown of maternally contributed Domino, a histone chaperone and ATPase, reduces H2A.Z deposition at transcription start sites, causes global downregulation of housekeeping genes at ZGA, and compromises the establishment of the 3D chromatin structure. We infer that H2A.Z is essential for the de novo establishment of transcriptional programs during ZGA via chromatin reorganization.

Reciprocal zebrafish-medaka hybrids reveal maternal control of zygotic genome activation timing

10.1101/2021.11.03.467109 ◽

2021 ◽

Author(s):

Krista R Gert ◽

Luis Enrique Cabrera Quio ◽

Maria Novatchkova ◽

Yixuan Guo ◽

Bradley R Cairns ◽

...

Keyword(s):

Early Development ◽

Hybrid System ◽

Control Mechanisms ◽

Zygotic Transcription ◽

Versatile Tool ◽

Paternal Control ◽

Genome Activation ◽

After fertilization, the sperm and egg contribute unequally to the newly formed zygote. While the sperm contributes mainly paternal DNA, the egg provides both maternal DNA and the bulk of the future embryonic cytoplasm. Most embryonic processes (like the onset of zygotic transcription) depend on maternally-provided cytoplasmic components, and it is largely unclear whether paternal components besides the centrosome play a role in the regulation of early embryogenesis. Here we report a reciprocal zebrafish-medaka hybrid system as a powerful tool to investigate paternal vs. maternal influence during early development. By combining expression of zebrafish Bouncer on the medaka egg with artificial egg activation, we demonstrate the in vitro generation of paternal zebrafish x maternal medaka (reripes) hybrids. These hybrids complement the previously established paternal medaka x maternal zebrafish (latio) hybrids (Herberg et al., 2018). As proof of concept, we investigated maternal vs. paternal control of zygotic genome activation (ZGA) timing using this reciprocal hybrid system. RNA-seq analysis of the purebred fish species and hybrids revealed that the onset of ZGA is primarily governed by the egg. Overall, our study establishes the reciprocal zebrafish-medaka hybrid system as a versatile tool to dissect parental control mechanisms during early development.

Characterization of zygotic genome activation-dependent maternal mRNA clearance in mouse

Nucleic Acids Research ◽

10.1093/nar/gkz1111 ◽

2019 ◽

Vol 48 (2) ◽

pp. 879-894 ◽

Cited By ~ 5

Author(s):

Qian-Qian Sha ◽

Ye-Zhang Zhu ◽

Sen Li ◽

Yu Jiang ◽

Lu Chen ◽

...

Keyword(s):

De Novo ◽

Mouse Embryos ◽

Developmental Competence ◽

Preimplantation Embryos ◽

Cell Stage ◽

Maternal Mrna ◽

Maternal Transcripts ◽

Genome Activation ◽

Abstract An important event of the maternal-to-zygotic transition (MZT) in animal embryos is the elimination of a subset of the maternal transcripts that accumulated during oogenesis. In both invertebrates and vertebrates, a maternally encoded mRNA decay pathway (M-decay) acts before zygotic genome activation (ZGA) while a second pathway, which requires zygotic transcription, subsequently clears additional mRNAs (Z-decay). To date the mechanisms that activate the Z-decay pathway in mammalian early embryos have not been investigated. Here, we identify murine maternal transcripts that are degraded after ZGA and show that inhibition of de novo transcription stabilizes these mRNAs in mouse embryos. We show that YAP1-TEAD4 transcription factor-mediated transcription is essential for Z-decay in mouse embryos and that TEAD4-triggered zygotic expression of terminal uridylyltransferases TUT4 and TUT7 and mRNA 3′-oligouridylation direct Z-decay. Components of the M-decay pathway, including BTG4 and the CCR4-NOT deadenylase, continue to function in Z-decay but require reinforcement from the zygotic factors for timely removal of maternal mRNAs. A long 3′-UTR and active translation confer resistance of Z-decay transcripts to M-decay during oocyte meiotic maturation. The Z-decay pathway is required for mouse embryo development beyond the four-cell stage and contributes to the developmental competence of preimplantation embryos.