scholarly journals Zebrafish Nanog is not required in embryonic cells

2016 ◽  
Author(s):  
James A. Gagnon ◽  
Kamal Obbad ◽  
Alexander F. Schier
Keyword(s):  
Embryonic Cell ◽  
Embryonic Cells ◽  
Blastula Stage ◽  
Embryonic Tissues ◽  
Zygotic Transcription ◽  
Summary Statement ◽  
Genome Activation ◽  
Mutant Cells ◽  
Zygotic Genome

SUMMARY STATEMENTThe study of nanog mutants reveals that Nanog is required only for extraembryonic tissue development, not in embryonic cells.ABSTRACTThe role of the zebrafish transcription factor Nanog has been controversial. It has been suggested that Nanog is primarily required for the formation of the extraembryonic yolk syncytial layer (YSL) and only indirectly regulates gene expression in embryonic cells. By contrast, a more recent study has proposed that Nanog directly regulates transcription in embryonic cells during zygotic genome activation. To clarify the roles of Nanog, we performed a detailed analysis of zebrafish nanog mutants. While zygotic nanog mutants survive to adulthood, maternal-zygotic and maternal mutants exhibit developmental arrest at the blastula stage. In the absence of Nanog, the YSL fails to form and embryonic tissue detaches from the yolk. Zygotic transcription of a subset of embryonic genes is affected in nanog mutants but both the YSL and embryonic phenotype can be rescued by providing nanog mRNA in YSL precursors. Notably, nanog mutant cells transplanted into wild-type hosts proliferate and contribute to embryonic tissues from all germ layers. These results indicate that zebrafish Nanog is necessary for YSL formation but is not directly required for embryonic cell differentiation.

CLAMP regulates Zygotic Genome Activation in Drosophila embryos

Genetics ◽  
2021 ◽  
Author(s):  
Megan M Colonnetta ◽  
Juan E Abrahante ◽  
Paul Schedl ◽  
Daryl M Gohl ◽  
Girish Deshpande
Keyword(s):  
Temporal Dynamics ◽  
Embryonic Patterning ◽  
Zygotic Genome Activation ◽  
Promoter Sequences ◽  
Genome Wide ◽  
Zygotic Transcription ◽  
Pioneer Factor ◽  
Genome Activation ◽  
Drosophila Embryos ◽  
Zygotic Genome

Abstract Embryonic patterning is critically dependent on zygotic genome activation (ZGA). In Drosophila melanogaster embryos, the pioneer factor Zelda directs ZGA, possibly in conjunction with other factors. Here we have explored novel involvement of Chromatin-Linked Adapter for MSL Proteins (CLAMP) during ZGA. CLAMP binds thousands of sites genome-wide throughout early embryogenesis. Interestingly, CLAMP relocates to target promoter sequences across the genome when ZGA is initiated. Although there is a considerable overlap between CLAMP and Zelda binding sites, the proteins display distinct temporal dynamics. To assess whether CLAMP occupancy affects gene expression, we analyzed transcriptomes of embryos zygotically compromised for either clamp or zelda and found that transcript levels of many zygotically-activated genes are similarly affected. Importantly, compromising either clamp or zelda disrupted the expression of critical segmentation and sex determination genes bound by CLAMP (and Zelda). Furthermore, clamp knockdown embryos recapitulate other phenotypes observed in Zelda-depleted embryos, including nuclear division defects, centrosome aberrations, and a disorganized actomyosin network. Based on these data, we propose that CLAMP acts in concert with Zelda to regulate early zygotic transcription.

scholarly journals Pluripotency factors select gene expression repertoire at Zygotic Genome Activation

2020 ◽  
Author(s):  
Meijiang Gao ◽  
Marina Veil ◽  
Marcus Rosenblatt ◽  
Anna Gebhard ◽  
Helge Hass ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Early Gene ◽  
Zebrafish Embryos ◽  
Fate Specification ◽  
Pluripotency Factors ◽  
Zygotic Transcription ◽  
Simultaneous Loss ◽  
Genome Activation ◽  
Zygotic Genome

AbstractAwakening of zygotic transcription in animal embryos relies on maternal pioneer transcription factors. The interplay of global and specific functions of these proteins remains poorly understood. Here, we analyzed nucleosome positioning, H3K27 acetylation, transcription, and gastrulation rates in zebrafish embryos lacking pluripotency factors Pou5f3 and Sox19b. We show that the bulk transcriptional onset does not require Sox19b and Pou5f3, but is sensitive to their balance. Pou5f3 docks H3K27ac on the enhancers of genes involved in gastrulation and ventral fate specification. Sox19b facilitates Pou5f3 access to one-third of these enhancers. The genes regulating mesendodermal and dorsal fates are primed for activation independently on Pou5f3 and Sox19b. Strikingly, the loss of either factor results in activation of silent enhancers; simultaneous loss of both leads to premature expression of differentiation genes. Our results uncover how independent activities of maternal Pou5f3 and Sox19b add up or antagonize to determine the early gene expression repertoire.

scholarly journals Whole-Transcriptome Sequencing-Based Analysis of DAZL and Its Interacting Genes during Germ Cells Specification and Zygotic Genome Activation in Chickens

2020 ◽  
Vol 21 (21) ◽  
pp. 8170
Author(s):  
Deivendran Rengaraj ◽  
Sohyoung Won ◽  
Jong Won Han ◽  
DongAhn Yoo ◽  
Heebal Kim ◽  
...  
Keyword(s):  
Germ Cells ◽  
Transcriptome Sequencing ◽  
Germ Plasm ◽  
Prediction Method ◽  
Zygotic Genome Activation ◽  
Zygotic Transcription ◽  
Whole Transcriptome Sequencing ◽  
Genome Activation ◽  
Whole Transcriptome ◽  
Zygotic Genome

The deleted in azoospermia like (DAZL) is required for germ cells development and maintenance. In chickens, the mRNA and protein of DAZL, a representative maternally inherited germ plasm factor, are detected in the germ plasm of oocyte, zygote, and all stages of the intrauterine embryos. However, it is still insufficient to explain the origin and specification process of chicken germ cells, because the stage at which the zygotic transcription of DAZL occurs and the stage at which the maternal DAZL RNA/protein clears have not yet been fully identified. Moreover, a comprehensive understanding of the expression of DAZL interacting genes during the germ cells specification and development and zygotic genome activation (ZGA) is lacking in chickens. In this study, we identified a set of DAZL interacting genes in chickens using in silico prediction method. Then, we analyzed the whole-transcriptome sequencing (WTS)-based expression of DAZL and its interacting genes in the chicken oocyte, zygote, and Eyal-Giladi and Kochav (EGK) stage embryos (EGK.I to EGK.X). In the results, DAZL transcripts are increased in the zygote (onset of transcription), maintained the increased level until EGK.VI, and decreased from EGK.VIII (possible clearance of maternal RNAs). Among the DAZL interacting genes, most of them are increased either at 1st ZGA or 2nd ZGA, indicating their involvement in germ cells specification and development.

scholarly journals Chromatin tethering to the nuclear envelope by nuclear actin filaments: a novel role of the actin cytoskeleton in the Xenopus blastula

2017 ◽  
Author(s):  
Haruka Oda ◽  
Natsuki Shirai ◽  
Naoko Ura ◽  
Keita Ohsumi ◽  
Mari Iwabuchi
Keyword(s):  
Nuclear Envelope ◽  
Mitotic Spindle ◽  
Chromatin Binding ◽  
Embryonic Cells ◽  
Blastula Stage ◽  
Physiological Importance ◽  
Egg Extract ◽  
Chromosome Alignment ◽  
M Phase

AbstractThe Xenopus oocyte is known to accumulate filamentous or F-actin in the nucleus, but it is currently unknown whether F-actin also accumulates in embryo nuclei. Using fluorescence-labeled actin reporters, we examined the actin distribution in Xenopus embryonic cells and found that F-actin accumulates in nuclei during the blastula stage but not during the gastrula stage. To further investigate nuclear F-actin, we devised a Xenopus egg extract that reproduces the formation of nuclei in which F-actin accumulates. Using this extract, we found that F-actin accumulates primarily at the sub-nuclear membranous region and is essential to maintain chromatin binding to the nuclear envelope in well-developed nuclei. We also provide evidence that nuclear F-actin increases the structural stability of nuclei and contributes to chromosome alignment on the mitotic spindle at the following M phase. These results suggest the physiological importance of nuclear F-actin accumulation in rapidly dividing, large Xenopus blastula cells.

scholarly journals Conservation and divergence of poly(A) tail regulation during the mammalian oocyte-to-embryo transition

2021 ◽  
Author(s):  
Yusheng Liu ◽  
Junxue Jin ◽  
Yiwei Zhang ◽  
Le-Yun Wang ◽  
Chuanxin Zhang ◽  
...  
Keyword(s):  
Length Distribution ◽  
Tail Length ◽  
Mammal Species ◽  
Mammalian Oocyte ◽  
Maternal Mrna ◽  
Post Transcriptional Regulation ◽  
Genome Activation ◽  
Parthenogenetic Embryos ◽  
Zygotic Genome

SUMMARYPoly(A) tail length and non-A residues are vital for oocyte-to-embryo transition (OET) in mice and humans1–5. However, the role of poly(A) tail length and non-A residues during OET in other commonly used mammalian animal models for human diseases remains unexplored. In addition, the degree of conservation in maternal mRNA poly(A) tail dynamics during OET across different mammal species is unknown. Here, we conduct a comparative analysis of the poly(A) tails during OET across four species: mice, rats, pigs, and humans. Dynamics during OET found to be conserved across all four species include: maternal mRNA deadenylation during oocyte maturation and re-polyadenylation after fertilization; a fall-rise trend in poly(A) tail length distribution; a rise-fall trend in the ratio of poly(A) tails with non-A residues; higher abundance of non-A residues in poly(A) tails of maternal mRNA than in zygotic genome activation (ZGA) mRNA; maternal mRNA with U residues degrades faster than those without U residues at the stage when ZGA takes place. While in mice and rats maternal mRNA deadenylation is impaired in parthenogenetic embryos and ZGA inhibition leads to blocked maternal mRNA deadenylation in mice and humans. In contrast, the length of consecutive U residues and the duration time of U residues in poly(A) tail diverges across the four species. Together, these findings reveal that the poly(A) tail mediated maternal mRNA post-transcriptional regulation is highly conserved in mammals with unique divergences in the length and life-span of U residues, providing new insights for the further understanding of OET across different mammals.

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

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 Genome Activation ◽  
Zygotic Transcription ◽  
Versatile Tool ◽  
Paternal Control ◽  
Genome Activation ◽  
Zygotic Genome

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.

scholarly journals Knockdown of Dnmt1 links Gene body DNA methylation to regulation of gene expression and maternal-zygotic transition in the wasp Nasonia

2021 ◽  
Author(s):  
Deanna Arsala ◽  
Xin Wu ◽  
Soojin V. Yi ◽  
Jeremy A. Lynch
Keyword(s):  
Dna Methylation ◽  
Bisulfite Sequencing ◽  
Regulation Of Gene Expression ◽  
Gene Body ◽  
Nasonia Vitripennis ◽  
Gene Body Methylation ◽  
Genome Bisulfite Sequencing ◽  
Genome Activation ◽  
Zygotic Genome

AbstractGene body methylation (GBM) is an ancestral form of DNA methylation whose role in development has remained unclear. Unlike vertebrates, DNA methylation is found exclusively in gene bodies in the wasp Nasonia vitripennis, which provides a unique opportunity to interpret the role of GBM in development. We confirmed that parental RNAi (pRNAi) knockdown of a DNMT1 ortholog (Nv-Dnmt1a) in Nasonia leads to embryonic lethality and failures in cellularization and morphogenesis. Using whole-genome bisulfite sequencing, we found a widespread loss of GBM in Nv-Dnmt1a pRNAi embryos. Using RNAseq, we found that methylated genes that lost GBM in the pRNAi samples were exclusively downregulated during zygotic genome activation. Unexpectedly, nearly all affected unmethylated genes were up-regulated after pRNAi. Lack of proper clearance of mRNAs and abnormal activation drive this up-regulation, indicating critical roles for Nv-Dnmt1a and GBM in the maternal-zygotic transition (MZT) in the wasp, despite their absence in Drosophila.

scholarly journals The DNA-to-cytoplasm ratio broadly activates zygotic gene expression in Xenopus

2021 ◽  
Author(s):  
David Jukam ◽  
Rishabh Kapoor ◽  
Aaron F Straight ◽  
Jan Skotheim
Keyword(s):  
Cycle Duration ◽  
Zygotic Genome Activation ◽  
Maternal Genome ◽  
Tropicalis Genome ◽  
Nuclear Component ◽  
Zygotic Gene ◽  
Component C ◽  
Genome Activation ◽  
Zygotic Genome

In multicellular animals, the first major event after fertilization is the switch from maternal to zygotic control of development. During this transition, zygotic gene transcription is broadly activated in an otherwise quiescent genome in a process known as zygotic genome activation (ZGA). In fast developing embryos, ZGA often overlaps with the slowing of initially synchronous cell divisions at the mid-blastula transition (MBT). Initial studies of the MBT led to the nuclear-to-cytoplasmic ratio model where MBT timing is regulated by the exponentially increasing amounts of some nuclear component N titrated against a fixed cytoplasmic component C. However, more recent experiments have been interpreted to suggest that ZGA is independent of the N/C ratio. To determine the role of the N/C ratio in ZGA, we generated Xenopus frog embryos with ~3-fold differences in genomic DNA (i.e., N) by using X. tropicalis sperm to fertilize X. laevis eggs with or without their maternal genome. Resulting embryos have otherwise identical X. tropicalis genome template amounts, embryo sizes, and X. laevis maternal environments. We used the X. tropicalis paternally derived mRNA to identify a high confidence set of exclusively zygotic transcripts. Both ZGA and the increase in cell cycle duration are delayed in embryos with ~3-fold less DNA per cell. Thus, DNA is an important component of the N/C ratio, which is indeed a critical regulator of zygotic genome activation in Xenopus embryos.

scholarly journals CLAMP and Zelda function together to promote Drosophila zygotic genome activation

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Jingyue Duan ◽  
Leila Rieder ◽  
Megan M Colonnetta ◽  
Annie Huang ◽  
Mary Mckenney ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Embryonic Development ◽  
Essential Role ◽  
Chromatin Accessibility ◽  
Zygotic Genome Activation ◽  
Zygotic Transcription ◽  
Pioneer Factor ◽  
Pioneer Transcription Factor ◽  
Genome Activation ◽  
Zygotic Genome

During the essential and conserved process of zygotic genome activation (ZGA), chromatin accessibility must increase to promote transcription. Drosophila is a well-established model for defining mechanisms that drive ZGA. Zelda (ZLD) is a key pioneer transcription factor (TF) that promotes ZGA in the Drosophila embryo. However, many genomic loci that contain GA-rich motifs become accessible during ZGA independent of ZLD. Therefore, we hypothesized that other early TFs that function with ZLD have not yet been identified, especially those that are capable of binding to GA-rich motifs such as CLAMP. Here, we demonstrate that Drosophila embryonic development requires maternal CLAMP to: 1) activate zygotic transcription; 2) increase chromatin accessibility at promoters of specific genes that often encode other essential TFs; 3) enhance chromatin accessibility and facilitate ZLD occupancy at a subset of key embryonic promoters. Thus, CLAMP functions as a pioneer factor which plays a targeted yet essential role in ZGA.

The role of cell lineage in development

1985 ◽  
Vol 312 (1153) ◽  
pp. 3-19 ◽  
Keyword(s):  
Cell Fate ◽  
Cell Lineage ◽  
Early Embryo ◽  
Embryonic Cell ◽  
Evolutionary Divergence ◽  
Causative Role ◽  
Embryonic Cells ◽  
Developmental Potential ◽  
Cell Lineages

Studies of the role of cell lineage in development began in the latter part of the 19th century, fell into decline in the early part of the 20th, and were revived about 20 years ago. This recent revival was accompanied by the introduction of new and powerful analytical techniques. Concepts of importance for cell lineage studies include the principal division modes by which a cell may give rise to its descendant clone (proliferative, stem cell and diversifying); developmental determinacy , or indeterminacy , which refer to the degree to which the normal cleavage pattern of the early embryo and the developmental fate of its individual cells is, or is not, the same in specimen after specimen; commitment , which refers to the restriction of the developmental potential of a pluripotent embryonic cell; and equivalence group , which refers to two or more equivalently pluripotent cell clones that normally take on different fates but of which under abnormal conditions one clone can take on the fate of another. Cell lineage can be inferred to have a causative role in developmental cell fate in embryos in which induced changes in cell division patterns lead to changes in cell fate. Moreover, such a causative role of cell lineage is suggested by cases where homologous cell types characteristic of a symmetrical and longitudinally metameric body plan arise via homologous cell lineages. The developmental pathways of commitment to particular cell fates proceed according to a mixed typologic and topographic hierarchy, which appears to reflect an evolutionary compromise between maximizing the ease of ordering the spatial distribution of the determinants of commitment and minimizing the need for migration of differentially committed embryonic cells. Comparison of the developmental cell lineages in leeches and insects indicates that the early course of embryogenesis is radically different in these phyletically related taxa. This evolutionary divergence of the course of early embryogenesis appears to be attributable to an increasing prevalence of polyclonal rather than monoclonal commitment in the phylogenetic line leading from an annelid-like ancestor to insects.

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