Growing an Embryo from a Single Cell: A Hurdle in Animal Life: Figure 1.

O’Farrell, Patrick H.

doi:10.1101/cshperspect.a019042

Cited by 51 publications

(42 citation statements)

References 93 publications

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“…Anamniote embryos contain everything needed to fuel development until feeding structures allow them to obtain external nutrients (O’Farrell, 2015). In addition, anamniote embryos typically have a period of rapid cell divisions following fertilization, whereas amniote embryos develop more slowly.…”

Section: Two Broad Categories Of Pre-gastrulation Vertebrate Embryo Dmentioning

confidence: 99%

Zygotic Genome Activation in Vertebrates

2017

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The first major developmental transition in vertebrate embryos is the maternal-to-zygotic transition (MZT) when maternal mRNAs are degraded and zygotic transcription begins. During the MZT, the embryo takes charge of gene expression to control cell differentiation and further development. This spectacular organismal transition requires nuclear reprogramming and the initiation of RNAPII at thousands of promoters. Zygotic genome activation (ZGA) is mechanistically coordinated with other embryonic events including changes in the cell cycle, chromatin state, and nuclear-to-cytoplasmic component ratios. Here, we review progress in understanding vertebrate ZGA dynamics in frogs, fish, mice, and humans to explore differences and emphasize common features.

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Section: Two Broad Categories Of Pre-gastrulation Vertebrate Embryo Dmentioning

confidence: 99%

Zygotic Genome Activation in Vertebrates

2017

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“…Nucleoli are transcription-dependent in somatic cells 23 ; they form at the end of mitosis, coalesce into fewer and larger nucleoli in S-phase, and disassemble before M phase. The oocyte is packed with maternally provided rRNA and ribosomes, 26,31 and rDNA transcription is undetectable at the 512-cell stage. 27 However, when nucleoli form and when rDNA becomes active in the zebrafish embryo is unknown.…”

Section: Fibrillarin Resides In Cbs Until Rdna Transcription Activationmentioning

confidence: 99%

Activation of transcription enforces the formation of distinct nuclear bodies in zebrafish embryos

et al. 2016

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Nuclear bodies are cellular compartments that lack lipid bilayers and harbor specific RNAs and proteins. Recent proposals that nuclear bodies form through liquid-liquid phase separation leave the question of how different nuclear bodies maintain their distinct identities unanswered. Here we investigate Cajal bodies (CBs), histone locus bodies (HLBs) and nucleoli -involved in assembly of the splicing machinery, histone mRNA 3 0 end processing, and rRNA processing, respectively -in the embryos of the zebrafish, Danio rerio. We take advantage of the transcriptional silence of the 1-cell embryo and follow nuclear body appearance as zygotic transcription becomes activated. CBs are present from fertilization onwards, while HLB and nucleolar components formed foci several hours later when histone genes and rDNA became active. HLB formation was blocked by transcription inhibition, suggesting nascent histone transcripts recruit HLB components like U7 snRNP. Surprisingly, we found that U7 base-pairing with nascent histone transcripts was not required for localization to HLBs. Rather, the type of Sm ring assembled on U7 determined its targeting to HLBs or CBs; the spliceosomal Sm ring targeted snRNAs to CBs while the specialized U7 Sm-ring localized to HLBs, demonstrating the contribution of protein constituents to the distinction among nuclear bodies. Thus, nucleolar, HLB, and CB components can mix in early embryogenesis when transcription is naturally or artificially silenced. These data support a model in which transcription of specific gene loci nucleates nuclear body components with high specificity and fidelity to perform distinct regulatory functions.

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“…a directional deformation of a tissue in the absence of volumetric growth), such as cell rearrangement, orientated cell division or cell shape change. Vertebrate embryos develop in vastly different nutritive environments that have a large impact on the relative degree of growth occurring during development (O'Farrell, 2015). This is likely to have an impact on the degree to which volumetric growth contributes to elongation.…”

Section: Introductionmentioning

confidence: 99%

Species tailoured contribution of volumetric growth and tissue convergence to posterior body elongation in vertebrates

et al. 2016

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Posterior body elongation is a widespread mechanism propelling the generation of the metazoan body plan. The posterior growth model predicts that a posterior growth zone generates sufficient tissue volume to elongate the posterior body. However, there are energy supply-related differences between vertebrates in the degree to which growth occurs concomitantly with embryogenesis. By applying a multi-scalar morphometric analysis in zebrafish embryos, we show that posterior body elongation is generated by an influx of cells from lateral regions, by convergence-extension of cells as they exit the tailbud, and finally by a late volumetric growth in the spinal cord and notochord. Importantly, the unsegmented region does not generate additional tissue volume. Fibroblast growth factor inhibition blocks tissue convergence rather than volumetric growth, showing that a conserved molecular mechanism can control convergent morphogenesis through different cell behaviours. Finally, via a comparative morphometric analysis in lamprey, dogfish, zebrafish and mouse, we propose that elongation via posterior volumetric growth is linked to increased energy supply and is associated with an overall increase in volumetric growth and elongation.

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Growing an Embryo from a Single Cell: A Hurdle in Animal Life: Figure 1.

Cited by 51 publications

References 93 publications

Zygotic Genome Activation in Vertebrates

Zygotic Genome Activation in Vertebrates

Activation of transcription enforces the formation of distinct nuclear bodies in zebrafish embryos

Species tailoured contribution of volumetric growth and tissue convergence to posterior body elongation in vertebrates

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