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Herrick J. DNA Damage, Genome Stability, and Adaptation: A Question of Chance or Necessity? Genes (Basel) 2024; 15:520. [PMID: 38674454 PMCID: PMC11049855 DOI: 10.3390/genes15040520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2024] [Revised: 04/14/2024] [Accepted: 04/18/2024] [Indexed: 04/28/2024] Open
Abstract
DNA damage causes the mutations that are the principal source of genetic variation. DNA damage detection and repair mechanisms therefore play a determining role in generating the genetic diversity on which natural selection acts. Speciation, it is commonly assumed, occurs at a rate set by the level of standing allelic diversity in a population. The process of speciation is driven by a combination of two evolutionary forces: genetic drift and ecological selection. Genetic drift takes place under the conditions of relaxed selection, and results in a balance between the rates of mutation and the rates of genetic substitution. These two processes, drift and selection, are necessarily mediated by a variety of mechanisms guaranteeing genome stability in any given species. One of the outstanding questions in evolutionary biology concerns the origin of the widely varying phylogenetic distribution of biodiversity across the Tree of Life and how the forces of drift and selection contribute to shaping that distribution. The following examines some of the molecular mechanisms underlying genome stability and the adaptive radiations that are associated with biodiversity and the widely varying species richness and evenness in the different eukaryotic lineages.
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Affiliation(s)
- John Herrick
- Independent Researcher at 3, Rue des Jeûneurs, 75002 Paris, France
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2
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Schindler-Johnson M, Petridou NI. Collective effects of cell cleavage dynamics. Front Cell Dev Biol 2024; 12:1358971. [PMID: 38559810 PMCID: PMC10978805 DOI: 10.3389/fcell.2024.1358971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 03/05/2024] [Indexed: 04/04/2024] Open
Abstract
A conserved process of early embryonic development in metazoans is the reductive cell divisions following oocyte fertilization, termed cell cleavages. Cell cleavage cycles usually start synchronously, lengthen differentially between the embryonic cells becoming asynchronous, and cease before major morphogenetic events, such as germ layer formation and gastrulation. Despite exhibiting species-specific characteristics, the regulation of cell cleavage dynamics comes down to common controllers acting mostly at the single cell/nucleus level, such as nucleus-to-cytoplasmic ratio and zygotic genome activation. Remarkably, recent work has linked cell cleavage dynamics to the emergence of collective behavior during embryogenesis, including pattern formation and changes in embryo-scale mechanics, raising the question how single-cell controllers coordinate embryo-scale processes. In this review, we summarize studies across species where an association between cell cleavages and collective behavior was made, discuss the underlying mechanisms, and propose that cell-to-cell variability in cell cleavage dynamics can serve as a mechanism of long-range coordination in developing embryos.
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Affiliation(s)
- Magdalena Schindler-Johnson
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Faculty of Biosciences, Heidelberg University, Heidelberg, Germany
| | - Nicoletta I. Petridou
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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3
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Bakshi A, Iturra FE, Alamban A, Rosas-Salvans M, Dumont S, Aydogan MG. Cytoplasmic division cycles without the nucleus and mitotic CDK/cyclin complexes. Cell 2023; 186:4694-4709.e16. [PMID: 37832525 PMCID: PMC10659773 DOI: 10.1016/j.cell.2023.09.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Revised: 05/11/2023] [Accepted: 09/12/2023] [Indexed: 10/15/2023]
Abstract
Cytoplasmic divisions are thought to rely on nuclear divisions and mitotic signals. We demonstrate in Drosophila embryos that cytoplasm can divide repeatedly without nuclei and mitotic CDK/cyclin complexes. Cdk1 normally slows an otherwise faster cytoplasmic division cycle, coupling it with nuclear divisions, and when uncoupled, cytoplasm starts dividing before mitosis. In developing embryos where CDK/cyclin activity can license mitotic microtubule (MT) organizers like the spindle, cytoplasmic divisions can occur without the centrosome, a principal organizer of interphase MTs. However, centrosomes become essential in the absence of CDK/cyclin activity, implying that the cytoplasm can employ either the centrosome-based interphase or CDK/cyclin-dependent mitotic MTs to facilitate its divisions. Finally, we present evidence that autonomous cytoplasmic divisions occur during unperturbed fly embryogenesis and that they may help extrude mitotically stalled nuclei during blastoderm formation. We postulate that cytoplasmic divisions occur in cycles governed by a yet-to-be-uncovered clock mechanism autonomous from CDK/cyclin complexes.
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Affiliation(s)
- Anand Bakshi
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Fabio Echegaray Iturra
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Andrew Alamban
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA; Biophysics Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Miquel Rosas-Salvans
- Department of Bioengineering and Therapeutic Science, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Sophie Dumont
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA
| | - Mustafa G Aydogan
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA; Biophysics Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA.
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4
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Harrison MM, Marsh AJ, Rushlow CA. Setting the stage for development: the maternal-to-zygotic transition in Drosophila. Genetics 2023; 225:iyad142. [PMID: 37616526 PMCID: PMC10550319 DOI: 10.1093/genetics/iyad142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 07/18/2023] [Indexed: 08/26/2023] Open
Abstract
The zygote has a daunting task ahead of itself; it must develop from a single cell (fertilized egg) into a fully functioning adult with a multitude of different cell types. In the beginning, the zygote has help from its mother, in the form of gene products deposited into the egg, but eventually, it must rely on its own resources to proceed through development. The transfer of developmental control from the mother to the embryo is called the maternal-to-zygotic transition (MZT). All animals undergo this transition, which is defined by two main processes-the degradation of maternal RNAs and the synthesis of new RNAs from the zygote's own genome. Here, we review the regulation of the MZT in Drosophila, but given the broad conservation of this essential process, much of the regulation is shared among metazoans.
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Affiliation(s)
- Melissa M Harrison
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706USA
| | - Audrey J Marsh
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706USA
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5
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Balachandra S, Sarkar S, Amodeo AA. The Nuclear-to-Cytoplasmic Ratio: Coupling DNA Content to Cell Size, Cell Cycle, and Biosynthetic Capacity. Annu Rev Genet 2022; 56:165-185. [PMID: 35977407 PMCID: PMC10165727 DOI: 10.1146/annurev-genet-080320-030537] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Though cell size varies between different cells and across species, the nuclear-to-cytoplasmic (N/C) ratio is largely maintained across species and within cell types. A cell maintains a relatively constant N/C ratio by coupling DNA content, nuclear size, and cell size. We explore how cells couple cell division and growth to DNA content. In some cases, cells use DNA as a molecular yardstick to control the availability of cell cycle regulators. In other cases, DNA sets a limit for biosynthetic capacity. Developmentally programmed variations in the N/C ratio for a given cell type suggest that a specific N/C ratio is required to respond to given physiological demands. Recent observations connecting decreased N/C ratios with cellular senescence indicate that maintaining the proper N/C ratio is essential for proper cellular functioning. Together, these findings suggest a causative, not simply correlative, role for the N/C ratio in regulating cell growth and cell cycle progression.
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Affiliation(s)
- Shruthi Balachandra
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA; ,
| | - Sharanya Sarkar
- Department of Microbiology and Immunology, Dartmouth College, Hanover, New Hampshire, USA;
| | - Amanda A Amodeo
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA; ,
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6
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Warecki B, Titen SWA, Alam MS, Vega G, Lemseffer N, Hug K, Minden JS, Sullivan W. Wolbachia action in the sperm produces developmentally deferred chromosome segregation defects during the Drosophila mid-blastula transition. eLife 2022; 11:81292. [PMID: 36149408 PMCID: PMC9507124 DOI: 10.7554/elife.81292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 09/09/2022] [Indexed: 11/29/2022] Open
Abstract
Wolbachia, a vertically transmitted endosymbiont infecting many insects, spreads rapidly through uninfected populations by a mechanism known as cytoplasmic incompatibility (CI). In CI, a paternally delivered modification of the sperm leads to chromatin defects and lethality during and after the first mitosis of embryonic development in multiple species. However, whether CI-induced defects in later stage embryos are a consequence of the first division errors or caused by independent defects remains unresolved. To address this question, we focused on ~1/3 of embryos from CI crosses in Drosophila simulans that develop apparently normally through the first and subsequent pre-blastoderm divisions before exhibiting mitotic errors during the mid-blastula transition and gastrulation. We performed single embryo PCR and whole genome sequencing to find a large percentage of these developed CI-derived embryos bypass the first division defect. Using fluorescence in situ hybridization, we find increased chromosome segregation errors in gastrulating CI-derived embryos that had avoided the first division defect. Thus, Wolbachia action in the sperm induces developmentally deferred defects that are not a consequence of the first division errors. Like the immediate defect, the delayed defect is rescued through crosses to infected females. These studies inform current models on the molecular and cellular basis of CI.
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Affiliation(s)
- Brandt Warecki
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Simon William Abraham Titen
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States.,Department of Biology and Chemistry, California State University Monterey Bay, Seaside, United States
| | - Mohammad Shahriyar Alam
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Giovanni Vega
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Nassim Lemseffer
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Karen Hug
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Jonathan S Minden
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, United States
| | - William Sullivan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
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7
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Cho CY, Seller CA, O’Farrell PH. Temporal control of late replication and coordination of origin firing by self-stabilizing Rif1-PP1 hubs in Drosophila. Proc Natl Acad Sci U S A 2022; 119:e2200780119. [PMID: 35733247 PMCID: PMC9245680 DOI: 10.1073/pnas.2200780119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 05/19/2022] [Indexed: 12/25/2022] Open
Abstract
In the metazoan S phase, coordinated firing of clusters of origins replicates different parts of the genome in a temporal program. Despite advances, neither the mechanism controlling timing nor that coordinating firing of multiple origins is fully understood. Rif1, an evolutionarily conserved inhibitor of DNA replication, recruits protein phosphatase 1 (PP1) and counteracts firing of origins by S-phase kinases. During the midblastula transition (MBT) in Drosophila embryos, Rif1 forms subnuclear hubs at each of the large blocks of satellite sequences and delays their replication. Each Rif1 hub disperses abruptly just prior to the replication of the associated satellite sequences. Here, we show that the level of activity of the S-phase kinase, DDK, accelerated this dispersal program, and that the level of Rif1-recruited PP1 retarded it. Further, Rif1-recruited PP1 supported chromatin association of nearby Rif1. This influence of nearby Rif1 can create a "community effect" counteracting kinase-induced dissociation such that an entire hub of Rif1 undergoes switch-like dispersal at characteristic times that shift in response to the balance of Rif1-PP1 and DDK activities. We propose a model in which the spatiotemporal program of late replication in the MBT embryo is controlled by self-stabilizing Rif1-PP1 hubs, whose abrupt dispersal synchronizes firing of associated late origins.
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Affiliation(s)
- Chun-Yi Cho
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
| | - Charles A. Seller
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
| | - Patrick H. O’Farrell
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
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8
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S Phase Duration Is Determined by Local Rate and Global Organization of Replication. BIOLOGY 2022; 11:biology11050718. [PMID: 35625446 PMCID: PMC9139170 DOI: 10.3390/biology11050718] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 04/29/2022] [Accepted: 05/03/2022] [Indexed: 11/17/2022]
Abstract
Simple Summary In order for a cell to divide into two cells, it must first copy its DNA. Although the time required for this process tends not to vary much, many examples of the importance of variability have been reported. In this review, we discuss the methods used to study this question, present some of the examples of variation, and attempt to explain the factors that determine the time required in simple terms. We will show that the overall time depends on the rate of DNA replication within a region, and on the temporal organization of the regions relative to each other. Abstract The duration of the cell cycle has been extensively studied and a wide degree of variability exists between cells, tissues and organisms. However, the duration of S phase has often been neglected, due to the false assumption that S phase duration is relatively constant. In this paper, we describe the methodologies to measure S phase duration, summarize the existing knowledge about its variability and discuss the key factors that control it. The local rate of replication (LRR), which is a combination of fork rate (FR) and inter-origin distance (IOD), has a limited influence on S phase duration, partially due to the compensation between FR and IOD. On the other hand, the organization of the replication program, specifically the amount of replication domains that fire simultaneously and the degree of overlap between the firing of distinct replication timing domains, is the main determinant of S phase duration. We use these principles to explain the variation in S phase length in different tissues and conditions.
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9
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Ferree PL, Xing M, Zhang JQ, Di Talia S. Structure-function analysis of Cdc25 Twine degradation at the Drosophila maternal-to-zygotic transition. Fly (Austin) 2022; 16:111-117. [PMID: 35227166 PMCID: PMC8890428 DOI: 10.1080/19336934.2022.2043095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Downregulation of protein phosphatase Cdc25Twine activity is linked to remodelling of the cell cycle during the Drosophila maternal-to-zygotic transition (MZT). Here, we present a structure-function analysis of Cdc25Twine. We use chimeras to show that the N-terminus regions of Cdc25Twine and Cdc25String control their differential degradation dynamics. Deletion of different regions of Cdc25Twine reveals a putative domain involved in and required for its rapid degradation during the MZT. Notably, a very similar domain is present in Cdc25String and deletion of the DNA replication checkpoint results in similar dynamics of degradation of both Cdc25String and Cdc25Twine. Finally, we show that Cdc25Twine degradation is delayed in embryos lacking the left arm of chromosome III. Thus, we propose a model for the differential regulation of Cdc25 at the Drosophila MZT.
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Affiliation(s)
- Patrick L Ferree
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Maggie Xing
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Jenny Q Zhang
- Department of Surgery, Alpert Medical School, Brown University, Providence, RI, USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
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10
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Ma X, Øvrebø JI, Thompson EM. Evolution of CDK1 Paralog Specializations in a Lineage With Fast Developing Planktonic Embryos. Front Cell Dev Biol 2022; 9:770939. [PMID: 35155443 PMCID: PMC8832800 DOI: 10.3389/fcell.2021.770939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Accepted: 12/27/2021] [Indexed: 12/03/2022] Open
Abstract
The active site of the essential CDK1 kinase is generated by core structural elements, among which the PSTAIRE motif in the critical αC-helix, is universally conserved in the single CDK1 ortholog of all metazoans. We report serial CDK1 duplications in the chordate, Oikopleura. Paralog diversifications in the PSTAIRE, activation loop substrate binding platform, ATP entrance site, hinge region, and main Cyclin binding interface, have undergone positive selection to subdivide ancestral CDK1 functions along the S-M phase cell cycle axis. Apparent coevolution of an exclusive CDK1d:Cyclin Ba/b pairing is required for oogenic meiosis and early embryogenesis, a period during which, unusually, CDK1d, rather than Cyclin Ba/b levels, oscillate, to drive very rapid cell cycles. Strikingly, the modified PSTAIRE of odCDK1d shows convergence over great evolutionary distance with plant CDKB, and in both cases, these variants exhibit increased specialization to M-phase.
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Affiliation(s)
- Xiaofei Ma
- College of Life Sciences, Northwest Normal University, Lanzhou, China
- Sars International Centre, University of Bergen, Bergen, Norway
- *Correspondence: Xiaofei Ma, , ; Eric M. Thompson,
| | - Jan Inge Øvrebø
- Sars International Centre, University of Bergen, Bergen, Norway
- Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Eric M. Thompson
- Sars International Centre, University of Bergen, Bergen, Norway
- Department of Biological Sciences, University of Bergen, Bergen, Norway
- *Correspondence: Xiaofei Ma, , ; Eric M. Thompson,
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11
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Abstract
Understanding the mechanisms of embryonic cell cycles is a central goal of developmental biology, as the regulation of the cell cycle must be closely coordinated with other events during early embryogenesis. Quantitative imaging approaches have recently begun to reveal how the cell cycle oscillator is controlled in space and time, and how it is integrated with mechanical signals to drive morphogenesis. Here, we discuss how the Drosophila embryo has served as an excellent model for addressing the molecular and physical mechanisms of embryonic cell cycles, with comparisons to other model systems to highlight conserved and species-specific mechanisms. We describe how the rapid cleavage divisions characteristic of most metazoan embryos require chemical waves and cytoplasmic flows to coordinate morphogenesis across the large expanse of the embryo. We also outline how, in the late cleavage divisions, the cell cycle is inter-regulated with the activation of gene expression to ensure a reliable maternal-to-zygotic transition. Finally, we discuss how precise transcriptional regulation of the timing of mitosis ensures that tissue morphogenesis and cell proliferation are tightly controlled during gastrulation.
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Affiliation(s)
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27705, USA
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12
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Liu B, Zhao H, Wu K, Großhans J. Temporal Gradients Controlling Embryonic Cell Cycle. BIOLOGY 2021; 10:biology10060513. [PMID: 34207742 PMCID: PMC8228447 DOI: 10.3390/biology10060513] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 06/05/2021] [Accepted: 06/07/2021] [Indexed: 12/17/2022]
Abstract
Simple Summary Embryonic cells sense temporal gradients of regulatory signals to determine whether and when to proceed or remodel the cell cycle. Such a control mechanism is allowed to accurately link the cell cycle with the developmental program, including cell differentiation, morphogenesis, and gene expression. The mid-blastula transition has been a paradigm for timing in early embryogenesis in frog, fish, and fly, among others. It has been argued for decades now if the events associated with the mid-blastula transition, i.e., the onset of zygotic gene expression, remodeling of the cell cycle, and morphological changes, are determined by a control mechanism or by absolute time. Recent studies indicate that multiple independent signals and mechanisms contribute to the timing of these different processes. Here, we focus on the mechanisms for cell cycle remodeling, specifically in Drosophila, which relies on gradual changes of the signal over time. We discuss pathways for checkpoint activation, decay of Cdc25 protein levels, as well as depletion of deoxyribonucleotide metabolites and histone proteins. The gradual changes of these signals are linked to Cdk1 activity by readout mechanisms involving thresholds. Abstract Cell proliferation in early embryos by rapid cell cycles and its abrupt pause after a stereotypic number of divisions present an attractive system to study the timing mechanism in general and its coordination with developmental progression. In animals with large eggs, such as Xenopus, zebrafish, or Drosophila, 11–13 very fast and synchronous cycles are followed by a pause or slowdown of the cell cycle. The stage when the cell cycle is remodeled falls together with changes in cell behavior and activation of the zygotic genome and is often referred to as mid-blastula transition. The number of fast embryonic cell cycles represents a clear and binary readout of timing. Several factors controlling the cell cycle undergo dynamics and gradual changes in activity or concentration and thus may serve as temporal gradients. Recent studies have revealed that the gradual loss of Cdc25 protein, gradual depletion of free deoxyribonucleotide metabolites, or gradual depletion of free histone proteins impinge on Cdk1 activity in a threshold-like manner. In this review, we will highlight with a focus on Drosophila studies our current understanding and recent findings on the generation and readout of these temporal gradients, as well as their position within the regulatory network of the embryonic cell cycle.
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Affiliation(s)
- Boyang Liu
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Han Zhao
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Keliang Wu
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Jörg Großhans
- Department of Biology, Philipps University, 35043 Marburg, Germany
- Correspondence:
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13
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Gaggioli V, Kieninger MR, Klucnika A, Butler R, Zegerman P. Identification of the critical replication targets of CDK reveals direct regulation of replication initiation factors by the embryo polarity machinery in C. elegans. PLoS Genet 2020; 16:e1008948. [PMID: 33320862 PMCID: PMC7771872 DOI: 10.1371/journal.pgen.1008948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 12/29/2020] [Accepted: 11/02/2020] [Indexed: 12/26/2022] Open
Abstract
During metazoan development, the cell cycle is remodelled to coordinate proliferation with differentiation. Developmental cues cause dramatic changes in the number and timing of replication initiation events, but the mechanisms and physiological importance of such changes are poorly understood. Cyclin-dependent kinases (CDKs) are important for regulating S-phase length in many metazoa, and here we show in the nematode Caenorhabditis elegans that an essential function of CDKs during early embryogenesis is to regulate the interactions between three replication initiation factors SLD-3, SLD-2 and MUS-101 (Dpb11/TopBP1). Mutations that bypass the requirement for CDKs to generate interactions between these factors is partly sufficient for viability in the absence of Cyclin E, demonstrating that this is a critical embryonic function of this Cyclin. Both SLD-2 and SLD-3 are asymmetrically localised in the early embryo and the levels of these proteins inversely correlate with S-phase length. We also show that SLD-2 asymmetry is determined by direct interaction with the polarity protein PKC-3. This study explains an essential function of CDKs for replication initiation in a metazoan and provides the first direct molecular mechanism through which polarization of the embryo is coordinated with DNA replication initiation factors. How and when a cell divides changes as the cell assumes different fates. How these changes in cell division are brought about are poorly understood, but are critical to ensure that cells do not over-proliferate leading to cancer. The nematode C. elegans is an excellent system to study the role of cell cycle changes during animal development. Here we show that two factors SLD-2 and SLD-3 are critical to control the decision to begin genome duplication. We show that these factors are differently distributed to different cell lineages in the early embryo, which may be a key event in determining the cell cycle rate in these cells. For the first time we show that, PKC-3, a key component of the machinery that determines the front (anterior) from the back (posterior) of the embryo directly controls SLD-2 distribution, which might explain how the polarisation of the embryo causes changes in the proliferation of different cell lineages. As PKC-3 is frequently mutated in human cancers, how this factor controls cell proliferation may be important to understand tumour progression.
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Affiliation(s)
- Vincent Gaggioli
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Manuela R. Kieninger
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Anna Klucnika
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
- Department of Genetics, University of Cambridge, United Kingdom
| | - Richard Butler
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Philip Zegerman
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry, University of Cambridge, United Kingdom
- * E-mail:
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14
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Strong IJT, Lei X, Chen F, Yuan K, O’Farrell PH. Interphase-arrested Drosophila embryos activate zygotic gene expression and initiate mid-blastula transition events at a low nuclear-cytoplasmic ratio. PLoS Biol 2020; 18:e3000891. [PMID: 33090988 PMCID: PMC7608951 DOI: 10.1371/journal.pbio.3000891] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 11/03/2020] [Accepted: 09/14/2020] [Indexed: 11/18/2022] Open
Abstract
Externally deposited eggs begin development with an immense cytoplasm and a single overwhelmed nucleus. Rapid mitotic cycles restore normality as the ratio of nuclei to cytoplasm (N/C) increases. A threshold N/C has been widely proposed to activate zygotic genome transcription and onset of morphogenesis at the mid-blastula transition (MBT). To test whether a threshold N/C is required for these events, we blocked N/C increase by down-regulating cyclin/Cdk1 to arrest early cell cycles in Drosophila. Embryos that were arrested two cell cycles prior to the normal MBT activated widespread transcription of the zygotic genome including genes previously described as N/C dependent. Zygotic transcription of these genes largely retained features of their regulation in space and time. Furthermore, zygotically regulated post-MBT events such as cellularization and gastrulation movements occurred in these cell cycle-arrested embryos. These results are not compatible with models suggesting that these MBT events are directly coupled to N/C. Cyclin/Cdk1 activity normally declines in tight association with increasing N/C and is regulated by N/C. By experimentally promoting the decrease in cyclin/Cdk1, we uncoupled MBT from N/C increase, arguing that N/C-guided down-regulation of cyclin/Cdk1 is sufficient for genome activation and MBT.
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Affiliation(s)
- Isaac J. T. Strong
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Xiaoyun Lei
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Fang Chen
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Kai Yuan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
- Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Patrick H. O’Farrell
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
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15
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Toralova T, Kinterova V, Chmelikova E, Kanka J. The neglected part of early embryonic development: maternal protein degradation. Cell Mol Life Sci 2020; 77:3177-3194. [PMID: 32095869 PMCID: PMC11104927 DOI: 10.1007/s00018-020-03482-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 01/24/2020] [Accepted: 02/07/2020] [Indexed: 12/28/2022]
Abstract
The degradation of maternally provided molecules is a very important process during early embryogenesis. However, the vast majority of studies deals with mRNA degradation and protein degradation is only a very little explored process yet. The aim of this article was to summarize current knowledge about the protein degradation during embryogenesis of mammals. In addition to resuming of known data concerning mammalian embryogenesis, we tried to fill the gaps in knowledge by comparison with facts known about protein degradation in early embryos of non-mammalian species. Maternal protein degradation seems to be driven by very strict rules in terms of specificity and timing. The degradation of some maternal proteins is certainly necessary for the normal course of embryonic genome activation (EGA) and several concrete proteins that need to be degraded before major EGA have been already found. Nevertheless, the most important period seems to take place even before preimplantation development-during oocyte maturation. The defects arisen during this period seems to be later irreparable.
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Affiliation(s)
- Tereza Toralova
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, Libechov, Czech Republic
| | - Veronika Kinterova
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, Libechov, Czech Republic.
- Department of Veterinary Sciences, Czech University of Life Sciences in Prague, Prague, Czech Republic.
| | - Eva Chmelikova
- Department of Veterinary Sciences, Czech University of Life Sciences in Prague, Prague, Czech Republic
| | - Jiri Kanka
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, Libechov, Czech Republic
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16
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Tang R, Jiang Z, Chen F, Yu W, Fan K, Tan J, Zhang Z, Liu X, Li P, Yuan K. The Kinase Activity of Drosophila BubR1 Is Required for Insulin Signaling-Dependent Stem Cell Maintenance. Cell Rep 2020; 31:107794. [PMID: 32579921 DOI: 10.1016/j.celrep.2020.107794] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 04/29/2020] [Accepted: 05/31/2020] [Indexed: 02/06/2023] Open
Abstract
As a core component of the mitotic checkpoint complex, BubR1 has a modular organization of molecular functions, with KEN box and other motifs at the N terminus inhibiting the anaphase-promoting complex/cyclosome, and a kinase domain at the C terminus, whose function remains unsettled, especially at organismal levels. We generate knock-in BubR1 mutations in the Drosophila genome to separately disrupt the KEN box and the kinase domain. All of the mutants are homozygously viable and fertile and show no defects in mitotic progression. The mutants without kinase activity have an increased lifespan and phenotypic changes associated with attenuated insulin signaling, including reduced InR on the cell membrane, weakened PI3K and AKT activity, and elevated expression of dFoxO targets. The BubR1 kinase-dead mutants have a reduced cap cell number in female germaria, which can be rescued by expressing a constitutively active InR. We conclude that one major physiological role of BubR1 kinase in Drosophila is to modulate insulin signaling.
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Affiliation(s)
- Ruijun Tang
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Zhenghui Jiang
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Fang Chen
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Weiyu Yu
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Kaijing Fan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Jieqiong Tan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Zhuohua Zhang
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Xing Liu
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China.
| | - Pishun Li
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Kai Yuan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China; Center for Clinical Biorepositories and Biospecimens, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.
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17
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Hur W, Kemp JP, Tarzia M, Deneke VE, Marzluff WF, Duronio RJ, Di Talia S. CDK-Regulated Phase Separation Seeded by Histone Genes Ensures Precise Growth and Function of Histone Locus Bodies. Dev Cell 2020; 54:379-394.e6. [PMID: 32579968 DOI: 10.1016/j.devcel.2020.06.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 02/17/2020] [Accepted: 05/30/2020] [Indexed: 10/24/2022]
Abstract
Many membraneless organelles form through liquid-liquid phase separation, but how their size is controlled and whether size is linked to function remain poorly understood. The histone locus body (HLB) is an evolutionarily conserved nuclear body that regulates the transcription and processing of histone mRNAs. Here, we show that Drosophila HLBs form through phase separation. During embryogenesis, the size of HLBs is controlled in a precise and dynamic manner that is dependent on the cell cycle and zygotic histone gene activation. Control of HLB growth is achieved by a mechanism integrating nascent mRNAs at the histone locus, which facilitates phase separation, and the nuclear concentration of the scaffold protein multi-sex combs (Mxc), which is controlled by the activity of cyclin-dependent kinases. Reduced Cdk2 activity results in smaller HLBs and the appearance of nascent, misprocessed histone mRNAs. Thus, our experiments identify a mechanism linking nuclear body growth and size with gene expression.
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Affiliation(s)
- Woonyung Hur
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27705, USA
| | - James P Kemp
- Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Marco Tarzia
- LPTMC, CNRS-UMR 7600, Sorbonne Université, 4 Pl. Jussieu, 75005 Paris, France
| | - Victoria E Deneke
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27705, USA
| | - William F Marzluff
- Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Robert J Duronio
- Department of Biology, Department of Genetics, Integrative Program for Biological and Genome Sciences, Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27705, USA.
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18
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Liu B, Gregor I, Müller HA, Großhans J. Fluorescence fluctuation analysis reveals PpV dependent Cdc25 protein dynamics in living embryos. PLoS Genet 2020; 16:e1008735. [PMID: 32251417 PMCID: PMC7162543 DOI: 10.1371/journal.pgen.1008735] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 04/16/2020] [Accepted: 03/25/2020] [Indexed: 12/21/2022] Open
Abstract
The protein phosphatase Cdc25 is a key regulator of the cell cycle by activating Cdk-cyclin complexes. Cdc25 is regulated by its expression levels and post-translational mechanisms. In early Drosophila embryogenesis, Cdc25/Twine drives the fast and synchronous nuclear cycles. A pause in the cell cycle and the remodeling to a more generic cell cycle mode with a gap phase are determined by Twine inactivation and destruction in early interphase 14, in response to zygotic genome activation. Although the pseudokinase Tribbles contributes to the timely degradation of Twine, Twine levels are controlled by additional yet unknown post-translational mechanisms. Here, we apply a non-invasive method based on fluorescence fluctuation analysis (FFA) to record the absolute concentration profiles of Twine with minute-scale resolution in single living embryos. Employing this assay, we found that Protein phosphatase V (PpV), the homologue of the catalytic subunit of human PP6, ensures appropriately low Twine protein levels at the onset of interphase 14. PpV controls directly or indirectly the phosphorylation of Twine at multiple serine and threonine residues as revealed by phosphosite mapping. Mutational analysis confirmed that these sites are involved in control of Twine protein dynamics, and cell cycle remodeling is delayed in a fraction of the phosphosite mutant embryos. Our data reveal a novel mechanism for control of Twine protein levels and their significance for embryonic cell cycle remodeling.
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Affiliation(s)
- Boyang Liu
- Fachbereich Biologie (FB17), Philipps-Universität Marburg, Marburg, Germany
- Institut für Entwicklungsbiochemie, Universitätsmedizin, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Ingo Gregor
- Drittes Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, Germany
| | - H.-Arno Müller
- Fachgebiet Entwicklungsgenetik, Institut für Biologie, Universität Kassel, Kassel, Germany
| | - Jörg Großhans
- Fachbereich Biologie (FB17), Philipps-Universität Marburg, Marburg, Germany
- Institut für Entwicklungsbiochemie, Universitätsmedizin, Georg-August-Universität Göttingen, Göttingen, Germany
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19
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Seller CA, Cho CY, O'Farrell PH. Rapid embryonic cell cycles defer the establishment of heterochromatin by Eggless/SetDB1 in Drosophila. Genes Dev 2019; 33:403-417. [PMID: 30808658 PMCID: PMC6446540 DOI: 10.1101/gad.321646.118] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/14/2019] [Indexed: 12/15/2022]
Abstract
Acquisition of chromatin modifications during embryogenesis distinguishes different regions of an initially naïve genome. In many organisms, repetitive DNA is packaged into constitutive heterochromatin that is marked by di/trimethylation of histone H3K9 and the associated protein HP1a. These modifications enforce the unique epigenetic properties of heterochromatin. However, in the early Drosophila melanogaster embryo, the heterochromatin lacks these modifications, which appear only later, when rapid embryonic cell cycles slow down at the midblastula transition (MBT). Here we focus on the initial steps restoring heterochromatic modifications in the embryo. We describe the JabbaTrap, a technique for inactivating maternally provided proteins in embryos. Using the JabbaTrap, we reveal a major requirement for the methyltransferase Eggless/SetDB1 in the establishment of heterochromatin. In contrast, other methyltransferases contribute minimally. Live imaging reveals that endogenous Eggless gradually accumulates on chromatin in interphase but then dissociates in mitosis, and its accumulation must restart in the next cell cycle. Cell cycle slowing as the embryo approaches the MBT permits increasing accumulation and action of Eggless at its targets. Experimental manipulation of interphase duration shows that cell cycle speed regulates Eggless. We propose that developmental slowing of the cell cycle times embryonic heterochromatin formation.
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Affiliation(s)
- Charles A Seller
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Chun-Yi Cho
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Patrick H O'Farrell
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
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20
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Hamm DC, Harrison MM. Regulatory principles governing the maternal-to-zygotic transition: insights from Drosophila melanogaster. Open Biol 2018; 8:180183. [PMID: 30977698 PMCID: PMC6303782 DOI: 10.1098/rsob.180183] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 11/09/2018] [Indexed: 12/19/2022] Open
Abstract
The onset of metazoan development requires that two terminally differentiated germ cells, a sperm and an oocyte, become reprogrammed to the totipotent embryo, which can subsequently give rise to all the cell types of the adult organism. In nearly all animals, maternal gene products regulate the initial events of embryogenesis while the zygotic genome remains transcriptionally silent. Developmental control is then passed from mother to zygote through a process known as the maternal-to-zygotic transition (MZT). The MZT comprises an intimately connected set of molecular events that mediate degradation of maternally deposited mRNAs and transcriptional activation of the zygotic genome. This essential developmental transition is conserved among metazoans but is perhaps best understood in the fruit fly, Drosophila melanogaster. In this article, we will review our understanding of the events that drive the MZT in Drosophila embryos and highlight parallel mechanisms driving this transition in other animals.
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Affiliation(s)
| | - Melissa M. Harrison
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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21
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Seller CA, O’Farrell PH. Rif1 prolongs the embryonic S phase at the Drosophila mid-blastula transition. PLoS Biol 2018; 16:e2005687. [PMID: 29746464 PMCID: PMC5963817 DOI: 10.1371/journal.pbio.2005687] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/22/2018] [Accepted: 04/23/2018] [Indexed: 01/09/2023] Open
Abstract
In preparation for dramatic morphogenetic events of gastrulation, rapid embryonic cell cycles slow at the mid-blastula transition (MBT). In Drosophila melanogaster embryos, down-regulation of cyclin-dependent kinase 1 (Cdk1) activity initiates this slowing by delaying replication of heterochromatic satellite sequences and extending S phase. We found that Cdk1 activity inhibited the chromatin association of Rap1 interacting factor 1 (Rif1), a candidate repressor of replication. Furthermore, Rif1 bound selectively to satellite sequences following Cdk1 down-regulation at the MBT. In the next S phase, Rif1 dissociated from different satellites in an orderly schedule that anticipated their replication. Rif1 lacking potential phosphorylation sites failed to dissociate and dominantly prevented completion of replication. Loss of Rif1 in mutant embryos shortened the post-MBT S phase and rescued embryonic cell cycles disrupted by depletion of the S phase–promoting kinase, cell division cycle 7 (Cdc7). Our work shows that Rif1 and S phase kinases compose a replication timer controlling first the developmental onset of late replication and then the precise schedule of replication within S phase. In addition, we describe how onset of late replication fits into the progressive maturation of heterochromatin during development. Cells divide rapidly in the early embryos of most animals. However, during a conserved period of development known as the mid-blastula transition (MBT), the cell cycle slows down dramatically. In Drosophila embryos, genome duplication abruptly slows to initiate this cell cycle prolongation. This is achieved through the onset of late replication, a well-recognized phenomenon in which specific sequences of the genome await replication until long after other sequences have finished. Even though this temporal program of replication is a major determinant of the duration of S phase, the factors involved in this process remain unknown. Here, we use genetics and real-time microscopy to visualize replication in developing fly embryos and show that the protein Rap1 interacting factor 1 (Rif1) mediates the introduction of late replication at the MBT. We find that at this stage, Rif1 binds to and selectively delays the replication of large blocks of repetitive DNA known as satellite sequences. During the rapid cell cycles before the MBT, we show that the cyclin-dependent kinase 1 (Cdk1) prevents Rif1 from slowing down DNA replication by driving its removal from the chromatin. The developmental down-regulation of Cdk1 at the MBT allows Rif1 to associate with the satellite sequences and initiate cell cycle slowing. Our work provides new insights into the temporal programming of S phase and into the embryonic origin of late replication.
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Affiliation(s)
- Charles A. Seller
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Patrick H. O’Farrell
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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22
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Abstract
The activation of the zygotic genome and onset of transcription in blastula embryos is linked to changes in cell behavior and remodeling of the cell cycle and constitutes a transition from exclusive maternal to zygotic control of development. This step in development is referred to as mid-blastula transition and has served as a paradigm for the link between developmental program and cell behavior and morphology. Here, we discuss the mechanism and functional relationships between the zygotic genome activation and cell cycle control during mid-blastula transition with a focus on Drosophila embryos.
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Affiliation(s)
- Boyang Liu
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany
| | - Jörg Grosshans
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany.
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23
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Ter Huurne M, Chappell J, Dalton S, Stunnenberg HG. Distinct Cell-Cycle Control in Two Different States of Mouse Pluripotency. Cell Stem Cell 2017; 21:449-455.e4. [PMID: 28985526 PMCID: PMC5658514 DOI: 10.1016/j.stem.2017.09.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 06/02/2017] [Accepted: 09/06/2017] [Indexed: 11/17/2022]
Abstract
Mouse embryonic stem cells (ESCs) cultured in serum are characterized by hyper-phosphorylated RB protein, lack of G1 control, and rapid progression through the cell cycle. Here, we show that ESCs grown in the presence of two small-molecule inhibitors (2i ESCs) have a longer G1-phase with hypo-phosphorylated RB, implying that they have a functional G1 checkpoint. Deletion of RB, P107, and P130 in 2i ESCs results in a G1-phase similar to that of serum ESCs. Inhibition of the ERK signaling pathway in serum ESCs results in the appearance of hypo-phosphorylated RB and the reinstatement of a G1 checkpoint. In addition, induction of a dormant state by the inhibition of MYC, resembling diapause, requires the presence of the RB family proteins. Collectively, our data show that RB-dependent G1 restriction point signaling is active in mouse ESCs grown in 2i but abrogated in serum by ERK-dependent phosphorylation.
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Affiliation(s)
- Menno Ter Huurne
- Department of Molecular Biology, Faculty of Science, Radboud University, 6525GA Nijmegen, the Netherlands
| | - James Chappell
- Paul D. Coverdell Center for Biomedical and Health Sciences, Department of Biochemistry and Molecular Biology, The University of Georgia, Athens, GA 30602, USA
| | - Stephen Dalton
- Paul D. Coverdell Center for Biomedical and Health Sciences, Department of Biochemistry and Molecular Biology, The University of Georgia, Athens, GA 30602, USA
| | - Hendrik G Stunnenberg
- Department of Molecular Biology, Faculty of Science, Radboud University, 6525GA Nijmegen, the Netherlands.
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24
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Chk1 Inhibition of the Replication Factor Drf1 Guarantees Cell-Cycle Elongation at the Xenopus laevis Mid-blastula Transition. Dev Cell 2017; 42:82-96.e3. [PMID: 28697335 PMCID: PMC5505860 DOI: 10.1016/j.devcel.2017.06.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 04/19/2017] [Accepted: 06/07/2017] [Indexed: 12/21/2022]
Abstract
The early cell divisions of many metazoan embryos are rapid and occur in the near absence of transcription. At the mid-blastula transition (MBT), the cell cycle elongates and several processes become established including the onset of bulk transcription and cell-cycle checkpoints. How these events are timed and coordinated is poorly understood. Here we show in Xenopus laevis that developmental activation of the checkpoint kinase Chk1 at the MBT results in the SCFβ-TRCP-dependent degradation of a limiting replication initiation factor Drf1. Inhibition of Drf1 is the primary mechanism by which Chk1 blocks cell-cycle progression in the early embryo and is an essential function of Chk1 at the blastula-to-gastrula stage of development. This study defines the downregulation of Drf1 as an important mechanism to coordinate the lengthening of the cell cycle and subsequent developmental processes. Activation of Chk1 at the Xenopus MBT results in the degradation of Drf1 Drf1 degradation is SCFβ-TRCP dependent Chk1 blocks the cell cycle in the early embryo through inhibition of Drf1 Inhibition of Drf1 is an essential function of Chk1 during gastrulation
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25
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Michael WM. Cyclin CYB-3 controls both S-phase and mitosis and is asymmetrically distributed in the early C. elegans embryo. Development 2017; 143:3119-27. [PMID: 27578178 DOI: 10.1242/dev.141226] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 07/21/2016] [Indexed: 12/20/2022]
Abstract
In early C. elegans embryos the timing of cell division is both invariant and developmentally regulated, yet how the cell cycle is controlled in the embryo and how cell cycle timing impacts early development remain important, unanswered questions. Here, I focus on the cyclin B3 ortholog CYB-3, and show that this cyclin has the unusual property of controlling both the timely progression through S-phase and mitotic entry, suggesting that CYB-3 is both an S-phase-promoting and mitosis-promoting factor. Furthermore, I find that CYB-3 is asymmetrically distributed in the two-cell embryo, such that the somatic precursor AB cell contains ∼2.5-fold more CYB-3 than its sister cell, the germline progenitor P1 CYB-3 is not only physically limited in P1 but also functionally limited, and this asymmetry is controlled by the par polarity network. These findings highlight the importance of the CYB-3 B3-type cyclin in cell cycle regulation in the early embryo and suggest that CYB-3 asymmetry helps establish the well-documented cell cycle asynchrony that occurs during cell division within the P-lineage.
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Affiliation(s)
- W Matthew Michael
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
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26
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Deneke VE, Melbinger A, Vergassola M, Di Talia S. Waves of Cdk1 Activity in S Phase Synchronize the Cell Cycle in Drosophila Embryos. Dev Cell 2017; 38:399-412. [PMID: 27554859 DOI: 10.1016/j.devcel.2016.07.023] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 06/13/2016] [Accepted: 07/26/2016] [Indexed: 01/16/2023]
Abstract
Embryos of most metazoans undergo rapid and synchronous cell cycles following fertilization. While diffusion is too slow for synchronization of mitosis across large spatial scales, waves of Cdk1 activity represent a possible process of synchronization. However, the mechanisms regulating Cdk1 waves during embryonic development remain poorly understood. Using biosensors of Cdk1 and Chk1 activities, we dissect the regulation of Cdk1 waves in the Drosophila syncytial blastoderm. We show that Cdk1 waves are not controlled by the mitotic switch but by a double-negative feedback between Cdk1 and Chk1. Using mathematical modeling and surgical ligations, we demonstrate a fundamental distinction between S phase Cdk1 waves, which propagate as active trigger waves in an excitable medium, and mitotic Cdk1 waves, which propagate as passive phase waves. Our findings show that in Drosophila embryos, Cdk1 positive feedback serves primarily to ensure the rapid onset of mitosis, while wave propagation is regulated by S phase events.
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Affiliation(s)
- Victoria E Deneke
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Anna Melbinger
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Massimo Vergassola
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
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27
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Hwang Y, Futran M, Hidalgo D, Pop R, Iyer DR, Scully R, Rhind N, Socolovsky M. Global increase in replication fork speed during a p57 KIP2-regulated erythroid cell fate switch. SCIENCE ADVANCES 2017; 3:e1700298. [PMID: 28560351 PMCID: PMC5446218 DOI: 10.1126/sciadv.1700298] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 03/28/2017] [Indexed: 06/07/2023]
Abstract
Cell cycle regulators are increasingly implicated in cell fate decisions, such as the acquisition or loss of pluripotency and self-renewal potential. The cell cycle mechanisms that regulate these cell fate decisions are largely unknown. We studied an S phase-dependent cell fate switch, in which murine early erythroid progenitors transition in vivo from a self-renewal state into a phase of active erythroid gene transcription and concurrent maturational cell divisions. We found that progenitors are dependent on p57KIP2-mediated slowing of replication forks for self-renewal, a novel function for cyclin-dependent kinase inhibitors. The switch to differentiation entails rapid down-regulation of p57KIP2 with a consequent global increase in replication fork speed and an abruptly shorter S phase. Our work suggests that cell cycles with specialized global DNA replication dynamics are integral to the maintenance of specific cell states and to cell fate decisions.
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Affiliation(s)
- Yung Hwang
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Melinda Futran
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Daniel Hidalgo
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Ramona Pop
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Divya Ramalingam Iyer
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Ralph Scully
- Division of Hematology-Oncology, Department of Medicine, and Cancer Research Institute, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA
| | - Nicholas Rhind
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Merav Socolovsky
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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28
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Andreyeva EN, Bernardo TJ, Kolesnikova TD, Lu X, Yarinich LA, Bartholdy BA, Guo X, Posukh OV, Healton S, Willcockson MA, Pindyurin AV, Zhimulev IF, Skoultchi AI, Fyodorov DV. Regulatory functions and chromatin loading dynamics of linker histone H1 during endoreplication in Drosophila. Genes Dev 2017; 31:603-616. [PMID: 28404631 PMCID: PMC5393055 DOI: 10.1101/gad.295717.116] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Accepted: 03/03/2017] [Indexed: 12/22/2022]
Abstract
Here, Andreyeva et al. show that linker histone H1 is required for the underreplicated phenomenon in Drosophila salivary glands, in which tissues undergo endoreplication without cell division, and the latest replicating regions occasionally fail to complete endoreplication, resulting in underreplicated domains of polytene chromosomes. They demonstrate that H1 directly interacts with the suppressor of underreplication (SUUR) protein and is required for SUUR binding to chromatin in vivo and that the localization of H1 in chromatin changes profoundly during the endocycle. Eukaryotic DNA replicates asynchronously, with discrete genomic loci replicating during different stages of S phase. Drosophila larval tissues undergo endoreplication without cell division, and the latest replicating regions occasionally fail to complete endoreplication, resulting in underreplicated domains of polytene chromosomes. Here we show that linker histone H1 is required for the underreplication (UR) phenomenon in Drosophila salivary glands. H1 directly interacts with the Suppressor of UR (SUUR) protein and is required for SUUR binding to chromatin in vivo. These observations implicate H1 as a critical factor in the formation of underreplicated regions and an upstream effector of SUUR. We also demonstrate that the localization of H1 in chromatin changes profoundly during the endocycle. At the onset of endocycle S (endo-S) phase, H1 is heavily and specifically loaded into late replicating genomic regions and is then redistributed during the course of endoreplication. Our data suggest that cell cycle-dependent chromosome occupancy of H1 is governed by several independent processes. In addition to the ubiquitous replication-related disassembly and reassembly of chromatin, H1 is deposited into chromatin through a novel pathway that is replication-independent, rapid, and locus-specific. This cell cycle-directed dynamic localization of H1 in chromatin may play an important role in the regulation of DNA replication timing.
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Affiliation(s)
- Evgeniya N Andreyeva
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russian Federation
| | - Travis J Bernardo
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Tatyana D Kolesnikova
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russian Federation.,Novosibirsk State University, Novosibirsk 630090, Russian Federation
| | - Xingwu Lu
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Lyubov A Yarinich
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russian Federation.,Novosibirsk State University, Novosibirsk 630090, Russian Federation
| | - Boris A Bartholdy
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Xiaohan Guo
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Olga V Posukh
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russian Federation
| | - Sean Healton
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Michael A Willcockson
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Alexey V Pindyurin
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russian Federation
| | - Igor F Zhimulev
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russian Federation.,Novosibirsk State University, Novosibirsk 630090, Russian Federation
| | - Arthur I Skoultchi
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Dmitry V Fyodorov
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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29
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Regulation of DNA Replication in Early Embryonic Cleavages. Genes (Basel) 2017; 8:genes8010042. [PMID: 28106858 PMCID: PMC5295036 DOI: 10.3390/genes8010042] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 01/06/2017] [Accepted: 01/11/2017] [Indexed: 11/18/2022] Open
Abstract
Early embryonic cleavages are characterized by short and highly synchronous cell cycles made of alternating S- and M-phases with virtually absent gap phases. In this contracted cell cycle, the duration of DNA synthesis can be extraordinarily short. Depending on the organism, the whole genome of an embryo is replicated at a speed that is between 20 to 60 times faster than that of a somatic cell. Because transcription in the early embryo is repressed, DNA synthesis relies on a large stockpile of maternally supplied proteins stored in the egg representing most, if not all, cellular genes. In addition, in early embryonic cell cycles, both replication and DNA damage checkpoints are inefficient. In this article, we will review current knowledge on how DNA synthesis is regulated in early embryos and discuss possible consequences of replicating chromosomes with little or no quality control.
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30
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Zhang M, Skirkanich J, Lampson MA, Klein PS. Cell Cycle Remodeling and Zygotic Gene Activation at the Midblastula Transition. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 953:441-487. [DOI: 10.1007/978-3-319-46095-6_9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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31
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Covert Prepatterning of a Cell Division Wave. Dev Cell 2016; 37:107-8. [PMID: 27093077 DOI: 10.1016/j.devcel.2016.04.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
A directional wave of mitosis, progressing posterior to anterior across the epidermis, is important for neural tube closure in the invertebrate chordate Ciona intestinalis. In this issue of Developmental Cell, Ogura and Sasakura (2016) show that the patterning of this wave unexpectedly has complex origins in the previous cell cycle.
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32
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Deneke VE, Melbinger A, Vergassola M, Di Talia S. Waves of Cdk1 Activity in S Phase Synchronize the Cell Cycle in Drosophila Embryos. Dev Cell 2016. [PMID: 27554859 DOI: 10.1016/j.devcel.2016.07.0240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
Embryos of most metazoans undergo rapid and synchronous cell cycles following fertilization. While diffusion is too slow for synchronization of mitosis across large spatial scales, waves of Cdk1 activity represent a possible process of synchronization. However, the mechanisms regulating Cdk1 waves during embryonic development remain poorly understood. Using biosensors of Cdk1 and Chk1 activities, we dissect the regulation of Cdk1 waves in the Drosophila syncytial blastoderm. We show that Cdk1 waves are not controlled by the mitotic switch but by a double-negative feedback between Cdk1 and Chk1. Using mathematical modeling and surgical ligations, we demonstrate a fundamental distinction between S phase Cdk1 waves, which propagate as active trigger waves in an excitable medium, and mitotic Cdk1 waves, which propagate as passive phase waves. Our findings show that in Drosophila embryos, Cdk1 positive feedback serves primarily to ensure the rapid onset of mitosis, while wave propagation is regulated by S phase events.
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Affiliation(s)
- Victoria E Deneke
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Anna Melbinger
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Massimo Vergassola
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
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33
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Ferree PL, Deneke VE, Di Talia S. Measuring time during early embryonic development. Semin Cell Dev Biol 2016; 55:80-8. [PMID: 26994526 PMCID: PMC4903905 DOI: 10.1016/j.semcdb.2016.03.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 03/15/2016] [Indexed: 11/27/2022]
Abstract
In most metazoans, embryonic development is orchestrated by a precise series of cellular behaviors. Understanding how such events are regulated to achieve a stereotypical temporal progression is a fundamental problem in developmental biology. In this review, we argue that studying the regulation of the cell cycle in early embryonic development will reveal novel principles of how embryos accurately measure time. We will discuss the strategies that have emerged from studying early development of Drosophila embryos. By comparing the development of flies to that of other metazoans, we will highlight both conserved and alternative mechanisms to generate precision during embryonic development.
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Affiliation(s)
- Patrick L Ferree
- Department of Cell Biology, Duke University Medical Center, Durham NC, United States
| | - Victoria E Deneke
- Department of Cell Biology, Duke University Medical Center, Durham NC, United States
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham NC, United States.
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34
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Yuan K, Seller CA, Shermoen AW, O'Farrell PH. Timing the Drosophila Mid-Blastula Transition: A Cell Cycle-Centered View. Trends Genet 2016; 32:496-507. [PMID: 27339317 DOI: 10.1016/j.tig.2016.05.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 05/19/2016] [Accepted: 05/23/2016] [Indexed: 11/18/2022]
Abstract
At the mid-blastula transition (MBT), externally developing embryos refocus from increasing cell number to elaboration of the body plan. Studies in Drosophila reveal a sequence of changes in regulators of Cyclin:Cdk1 that increasingly restricts the activity of this cell cycle kinase to slow cell cycles during early embryogenesis. By reviewing these events, we provide an outline of the mechanisms slowing the cell cycle at and around the time of MBT. The perspectives developed should provide a guiding paradigm for the study of other MBT changes as the embryo transits from maternal control to a regulatory program centered on the expression of zygotic genes.
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Affiliation(s)
- Kai Yuan
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Charles A Seller
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Antony W Shermoen
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Patrick H O'Farrell
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA 94158, USA.
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35
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Yuan K, O'Farrell PH. TALE-light imaging reveals maternally guided, H3K9me2/3-independent emergence of functional heterochromatin in Drosophila embryos. Genes Dev 2016; 30:579-93. [PMID: 26915820 PMCID: PMC4782051 DOI: 10.1101/gad.272237.115] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 01/26/2016] [Indexed: 11/25/2022]
Abstract
In this study, Yuan and O'Farrell investigated how heterochromatin is established during development. Using new methodology for live imaging that allows spatial and temporal resolution of heterochromatin formation during normal Drosophila embryogenesis, they show that a maternal signal can act transgenerationally to influence the formation of heterochromatin on a satellite sequence. Metazoans start embryogenesis with a relatively naïve genome. The transcriptionally inert, late-replicating heterochromatic regions, including the constitutive heterochromatin on repetitive sequences near centromeres and telomeres, need to be re-established during development. To explore the events initiating heterochromatin formation and examine their temporal control, sequence specificity, and immediate regulatory consequence, we established a live imaging approach that enabled visualization of steps in heterochromatin emergence on specific satellite sequences during the mid-blastula transition (MBT) in Drosophila. Unexpectedly, only a subset of satellite sequences, including the 359-base-pair (bp) repeat sequence, recruited HP1a at the MBT. The recruitment of HP1a to the 359-bp repeat was dependent on HP1a's chromoshadow domain but not its chromodomain and was guided by maternally provided signals. HP1a recruitment to the 359-bp repeat was required for its programmed shift to later replication, and ectopic recruitment of HP1a was sufficient to delay replication timing of a different repeat. Our results reveal that emergence of constitutive heterochromatin follows a stereotyped developmental program in which different repetitive sequences use distinct interactions and independent pathways to arrive at a heterochromatic state. This differential emergence of heterochromatin on various repetitive sequences changes their replication order and remodels the DNA replication schedule during embryonic development.
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Affiliation(s)
- Kai Yuan
- Department of Biochemistry, University of California at San Francisco, San Francisco, California 94158, USA
| | - Patrick H O'Farrell
- Department of Biochemistry, University of California at San Francisco, San Francisco, California 94158, USA
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36
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Park H, Yoo S. vnd and its target gene twine are required for cell cycle progression during embryonic nervous system development in Drosophila melanogaster. Genes Genomics 2016. [DOI: 10.1007/s13258-015-0371-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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37
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Siefert JC, Clowdus EA, Sansam CL. Cell cycle control in the early embryonic development of aquatic animal species. Comp Biochem Physiol C Toxicol Pharmacol 2015; 178:8-15. [PMID: 26475527 PMCID: PMC4755307 DOI: 10.1016/j.cbpc.2015.10.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 10/07/2015] [Accepted: 10/09/2015] [Indexed: 01/02/2023]
Abstract
The cell cycle is integrated with many aspects of embryonic development. Not only is proper control over the pace of cell proliferation important, but also the timing of cell cycle progression is coordinated with transcription, cell migration, and cell differentiation. Due to the ease with which the embryos of aquatic organisms can be observed and manipulated, they have been a popular choice for embryologists throughout history. In the cell cycle field, aquatic organisms have been extremely important because they have played a major role in the discovery and analysis of key regulators of the cell cycle. In particular, the frog Xenopus laevis has been instrumental for understanding how the basic embryonic cell cycle is regulated. More recently, the zebrafish has been used to understand how the cell cycle is remodeled during vertebrate development and how it is regulated during morphogenesis. This review describes how some of the unique strengths of aquatic species have been leveraged for cell cycle research and suggests how species such as Xenopus and zebrafish will continue to reveal the roles of the cell cycle in human biology and disease.
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Affiliation(s)
- Joseph C Siefert
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, OK, USA; University of Oklahoma Health Sciences Center, Department of Cell Biology, Oklahoma City, OK, USA
| | - Emily A Clowdus
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, OK, USA; University of Oklahoma Health Sciences Center, Department of Cell Biology, Oklahoma City, OK, USA
| | - Christopher L Sansam
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, OK, USA; University of Oklahoma Health Sciences Center, Department of Cell Biology, Oklahoma City, OK, USA.
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38
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Ayeni JO, Campbell SD. "Ready, set, go": checkpoint regulation by Cdk1 inhibitory phosphorylation. Fly (Austin) 2015; 8:140-7. [PMID: 25483135 DOI: 10.4161/19336934.2014.969147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
ABSTRACT Cell cycle checkpoints prevent mitosis from occurring before DNA replication and repair are completed during S and G2 phases. The checkpoint mechanism involves inhibitory phosphorylation of Cdk1, a conserved kinase that regulates the onset of mitosis. Metazoans have two distinct Cdk1 inhibitory kinases with specialized developmental functions: Wee1 and Myt1. Ayeni et al used transgenic Cdk1 phospho-acceptor mutants to analyze how the distinct biochemical properties of these kinases affected their functions. They concluded from their results that phosphorylation of Cdk1 on Y15 was necessary and sufficient for G2/M checkpoint arrest in imaginal wing discs, whereas phosphorylation on T14 promoted chromosome stability by a different mechanism. A curious relationship was also noted between Y15 inhibitory phosphorylation and T161 activating phosphorylation. These unexpected complexities in Cdk1 inhibitory phosphorylation demonstrate that the checkpoint mechanism is not a simple binary "off/on" switch, but has at least three distinct states: "Ready", to prevent chromosome damage and apoptosis, "Set", for developmentally regulated G2 phase arrest, and "Go", when Cdc25 phosphatases remove inhibitory phosphates to trigger Cdk1 activation at the G2/M transition.
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Affiliation(s)
- J O Ayeni
- a Department of Biological Sciences ; University of Alberta ; Edmonton , AB , Canada
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39
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Gitlin AD, Mayer CT, Oliveira TY, Shulman Z, Jones MJK, Koren A, Nussenzweig MC. HUMORAL IMMUNITY. T cell help controls the speed of the cell cycle in germinal center B cells. Science 2015; 349:643-6. [PMID: 26184917 DOI: 10.1126/science.aac4919] [Citation(s) in RCA: 160] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Accepted: 07/08/2015] [Indexed: 12/20/2022]
Abstract
The germinal center (GC) is a microanatomical compartment wherein high-affinity antibody-producing B cells are selectively expanded. B cells proliferate and mutate their antibody genes in the dark zone (DZ) of the GC and are then selected by T cells in the light zone (LZ) on the basis of affinity. Here, we show that T cell help regulates the speed of cell cycle phase transitions and DNA replication of GC B cells. Genome sequencing and single-molecule analyses revealed that T cell help shortens S phase by regulating replication fork progression, while preserving the relative order of replication origin activation. Thus, high-affinity GC B cells are selected by a mechanism that involves prolonged dwell time in the DZ where selected cells undergo accelerated cell cycles.
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Affiliation(s)
- Alexander D Gitlin
- Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA
| | - Christian T Mayer
- Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA
| | - Thiago Y Oliveira
- Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA
| | - Ziv Shulman
- Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA
| | - Mathew J K Jones
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Amnon Koren
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Michel C Nussenzweig
- Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA. Howard Hughes Medical Institute (HHMI), The Rockefeller University, New York, NY 10065, USA.
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40
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Yamamoto K, Chikaoka Y, Hayashi G, Sakamoto R, Yamamoto R, Sugiyama A, Kodama T, Okamoto A, Kawamura T. Middle-Down and Chemical Proteomic Approaches to Reveal Histone H4 Modification Dynamics in Cell Cycle: Label-Free Semi-Quantification of Histone Tail Peptide Modifications Including Phosphorylation and Highly Sensitive Capture of Histone PTM Binding Proteins Using Photo-Reactive Crosslinkers. ACTA ACUST UNITED AC 2015; 4:A0039. [PMID: 26819910 DOI: 10.5702/massspectrometry.a0039] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 05/04/2015] [Indexed: 12/13/2022]
Abstract
Mass spectrometric proteomics is an effective approach for identifying and quantifying histone post-translational modifications (PTMs) and their binding proteins, especially in the cases of methylation and acetylation. However, another vital PTM, phosphorylation, tends to be poorly quantified because it is easily lost and inefficiently ionized. In addition, PTM binding proteins for phosphorylation are sometimes resistant to identification because of their variable binding affinities. Here, we present our efforts to improve the sensitivity of detection of histone H4 tail peptide phosphorylated at serine 1 (H4S1ph) and our successful identification of an H4S1ph binder candidate by means of a chemical proteomics approach. Our nanoLC-MS/MS system permitted semi-quantitative label-free analysis of histone H4 PTM dynamics of cell cycle-synchronized HeLa S3 cells, including phosphorylation, methylation, and acetylation. We show that H4S1ph abundance on nascent histone H4 unmethylated at lysine 20 (H4K20me0) peaks from late S-phase to M-phase. We also attempted to characterize effects of phosphorylation at H4S1 on protein-protein interactions. Specially synthesized photoaffinity bait peptides specifically captured 14-3-3 proteins as novel H4S1ph binding partners, whose interaction was otherwise undetectable by conventional peptide pull-down experiments. This is the first report that analyzes dynamics of PTM pattern on the whole histone H4 tail during cell cycle and enables the identification of PTM binders with low affinities using high-resolution mass spectrometry and photo-affinity bait peptides.
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Affiliation(s)
- Kazuki Yamamoto
- Department of Systems Biology and Medicine, Research Center for Advanced Science and Technology,
The University of Tokyo; The Translational Systems Biology and Medicine Initiative Center for Disease Biology and Integrative Medicine,
Faculty of Medicine, University of Tokyo
| | - Yoko Chikaoka
- Department of Systems Biology and Medicine, Research Center for Advanced Science and Technology,
The University of Tokyo; The Translational Systems Biology and Medicine Initiative Center for Disease Biology and Integrative Medicine,
Faculty of Medicine, University of Tokyo
| | - Gosuke Hayashi
- Department of Chemistry and Biotechnology, The University of Tokyo
| | - Ryosuke Sakamoto
- Department of Chemistry and Biotechnology, The University of Tokyo
| | - Ryuji Yamamoto
- Department of Systems Biology and Medicine, Research Center for Advanced Science and Technology,
The University of Tokyo
| | | | - Tatsuhiko Kodama
- Department of Systems Biology and Medicine, Research Center for Advanced Science and Technology,
The University of Tokyo
| | - Akimitsu Okamoto
- Research Center for Advanced Science and Technology, The University of Tokyo
| | - Takeshi Kawamura
- Department of Systems Biology and Medicine, Research Center for Advanced Science and Technology,
The University of Tokyo; The Translational Systems Biology and Medicine Initiative Center for Disease Biology and Integrative Medicine,
Faculty of Medicine, University of Tokyo
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41
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Martinho RG, Guilgur LG, Prudêncio P. How gene expression in fast-proliferating cells keeps pace. Bioessays 2015; 37:514-24. [PMID: 25823409 DOI: 10.1002/bies.201400195] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The development of living organisms requires a precise coordination of all basic cellular processes, in space and time. Early embryogenesis of most species with externally deposited eggs starts with a series of extremely fast cleavage cycles. These divisions have a strong influence on gene expression as mitosis represses transcription and pre-mRNA processing. In this review, we will describe the distinct adaptations for efficient gene expression and discuss the emerging role of the multifunctional NineTeen Complex (NTC) in gene expression and genomic stability during fast proliferation.
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Affiliation(s)
- Rui G Martinho
- Departamento de Ciências Biomédicas e Medicina, Regenerative Medicine Program, Universidade do Algarve, Campus de Gambelas, Faro, Portugal; Center for Biomedical Research, Universidade do Algarve, Campus de Gambelas, Faro, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal
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42
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Amodeo AA, Jukam D, Straight AF, Skotheim JM. Histone titration against the genome sets the DNA-to-cytoplasm threshold for the Xenopus midblastula transition. Proc Natl Acad Sci U S A 2015; 112:E1086-95. [PMID: 25713373 PMCID: PMC4364222 DOI: 10.1073/pnas.1413990112] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During early development, animal embryos depend on maternally deposited RNA until zygotic genes become transcriptionally active. Before this maternal-to-zygotic transition, many species execute rapid and synchronous cell divisions without growth phases or cell cycle checkpoints. The coordinated onset of transcription, cell cycle lengthening, and cell cycle checkpoints comprise the midblastula transition (MBT). A long-standing model in the frog, Xenopus laevis, posits that MBT timing is controlled by a maternally loaded inhibitory factor that is titrated against the exponentially increasing amount of DNA. To identify MBT regulators, we developed an assay using Xenopus egg extract that recapitulates the activation of transcription only above the DNA-to-cytoplasm ratio found in embryos at the MBT. We used this system to biochemically purify factors responsible for inhibiting transcription below the threshold DNA-to-cytoplasm ratio. This unbiased approach identified histones H3 and H4 as concentration-dependent inhibitory factors. Addition or depletion of H3/H4 from the extract quantitatively shifted the amount of DNA required for transcriptional activation in vitro. Moreover, reduction of H3 protein in embryos induced premature transcriptional activation and cell cycle lengthening, and the addition of H3/H4 shortened post-MBT cell cycles. Our observations support a model for MBT regulation by DNA-based titration and suggest that depletion of free histones regulates the MBT. More broadly, our work shows how a constant concentration DNA binding molecule can effectively measure the amount of cytoplasm per genome to coordinate division, growth, and development.
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Blythe SA, Wieschaus EF. Zygotic genome activation triggers the DNA replication checkpoint at the midblastula transition. Cell 2015; 160:1169-81. [PMID: 25748651 DOI: 10.1016/j.cell.2015.01.050] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 11/03/2014] [Accepted: 01/08/2015] [Indexed: 11/16/2022]
Abstract
A conserved feature of the midblastula transition (MBT) is a requirement for a functional DNA replication checkpoint to coordinate cell-cycle remodeling and zygotic genome activation (ZGA). We have investigated what triggers this checkpoint during Drosophila embryogenesis. We find that the magnitude of the checkpoint scales with the quantity of transcriptionally engaged DNA. Measuring RNA polymerase II (Pol II) binding at 20 min intervals over the course of ZGA reveals that the checkpoint coincides with widespread de novo recruitment of Pol II that precedes and does not require a functional checkpoint. This recruitment drives slowing or stalling of DNA replication at transcriptionally engaged loci. Reducing Pol II recruitment in zelda mutants both reduces replication stalling and bypasses the requirement for a functional checkpoint. This suggests a model where the checkpoint functions as a feedback mechanism to remodel the cell cycle in response to nascent ZGA.
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Affiliation(s)
- Shelby A Blythe
- Department of Molecular Biology, Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA
| | - Eric F Wieschaus
- Department of Molecular Biology, Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA.
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44
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Sansam CG, Goins D, Siefert JC, Clowdus EA, Sansam CL. Cyclin-dependent kinase regulates the length of S phase through TICRR/TRESLIN phosphorylation. Genes Dev 2015; 29:555-66. [PMID: 25737283 PMCID: PMC4358407 DOI: 10.1101/gad.246827.114] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 01/23/2015] [Indexed: 12/22/2022]
Abstract
S-phase cyclin-dependent kinases (CDKs) stimulate replication initiation and accelerate progression through the replication timing program, but it is unknown which CDK substrates are responsible for these effects. CDK phosphorylation of the replication factor TICRR (TopBP1-interacting checkpoint and replication regulator)/TRESLIN is required for DNA replication. We show here that phosphorylated TICRR is limiting for S-phase progression. Overexpression of a TICRR mutant with phosphomimetic mutations at two key CDK-phosphorylated residues (TICRR(TESE)) stimulates DNA synthesis and shortens S phase by increasing replication initiation. This effect requires the TICRR region that is necessary for its interaction with MDM two-binding protein. Expression of TICRR(TESE) does not grossly alter the spatial organization of replication forks in the nucleus but does increase replication clusters and the number of replication forks within each cluster. In contrast to CDK hyperactivation, the acceleration of S-phase progression by TICRR(TESE) does not induce DNA damage. These results show that CDK can stimulate initiation and compress the replication timing program by phosphorylating a single protein, suggesting a simple mechanism by which S-phase length is controlled.
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Affiliation(s)
- Courtney G Sansam
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA;
| | - Duane Goins
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA
| | - Joseph C Siefert
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | - Emily A Clowdus
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | - Christopher L Sansam
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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Ma Y, Kanakousaki K, Buttitta L. How the cell cycle impacts chromatin architecture and influences cell fate. Front Genet 2015; 6:19. [PMID: 25691891 PMCID: PMC4315090 DOI: 10.3389/fgene.2015.00019] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/14/2015] [Indexed: 01/17/2023] Open
Abstract
Since the earliest observations of cells undergoing mitosis, it has been clear that there is an intimate relationship between the cell cycle and nuclear chromatin architecture. The nuclear envelope and chromatin undergo robust assembly and disassembly during the cell cycle, and transcriptional and post-transcriptional regulation of histone biogenesis and chromatin modification is controlled in a cell cycle-dependent manner. Chromatin binding proteins and chromatin modifications in turn influence the expression of critical cell cycle regulators, the accessibility of origins for DNA replication, DNA repair, and cell fate. In this review we aim to provide an integrated discussion of how the cell cycle machinery impacts nuclear architecture and vice-versa. We highlight recent advances in understanding cell cycle-dependent histone biogenesis and histone modification deposition, how cell cycle regulators control histone modifier activities, the contribution of chromatin modifications to origin firing for DNA replication, and newly identified roles for nucleoporins in regulating cell cycle gene expression, gene expression memory and differentiation. We close with a discussion of how cell cycle status may impact chromatin to influence cell fate decisions, under normal contexts of differentiation as well as in instances of cell fate reprogramming.
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Affiliation(s)
- Yiqin Ma
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor, MI, USA
| | - Kiriaki Kanakousaki
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor, MI, USA
| | - Laura Buttitta
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor, MI, USA
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46
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Coordinating Cell Cycle Remodeling with Transcriptional Activation at the Drosophila MBT. Curr Top Dev Biol 2015; 113:113-48. [DOI: 10.1016/bs.ctdb.2015.06.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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47
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Yuan K, Shermoen AW, O'Farrell PH. Illuminating DNA replication during Drosophila development using TALE-lights. Curr Biol 2014; 24:R144-5. [PMID: 24556431 DOI: 10.1016/j.cub.2014.01.023] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Kai Yuan
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Antony W Shermoen
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Patrick H O'Farrell
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
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48
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Farrell JA, O'Farrell PH. From egg to gastrula: how the cell cycle is remodeled during the Drosophila mid-blastula transition. Annu Rev Genet 2014; 48:269-94. [PMID: 25195504 DOI: 10.1146/annurev-genet-111212-133531] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Many, if not most, embryos begin development with extremely short cell cycles that exhibit unusually rapid DNA replication and no gap phases. The commitment to the cell cycle in the early embryo appears to preclude many other cellular processes that only emerge as the cell cycle slows just prior to gastrulation at a major embryonic transition known as the mid-blastula transition (MBT). As reviewed here, genetic and molecular studies in Drosophila have identified changes that extend S phase and introduce a post-replicative gap phase, G2, to slow the cell cycle. Although many mysteries remain about the upstream regulators of these changes, we review the core mechanisms of the change in cell cycle regulation and discuss advances in our understanding of how these might be timed and triggered. Finally, we consider how the elements of this program may be conserved or changed in other organisms.
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Affiliation(s)
- Jeffrey A Farrell
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138;
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Bouldin CM, Snelson CD, Farr GH, Kimelman D. Restricted expression of cdc25a in the tailbud is essential for formation of the zebrafish posterior body. Genes Dev 2014; 28:384-95. [PMID: 24478331 PMCID: PMC3937516 DOI: 10.1101/gad.233577.113] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The vertebrate body forms from a multipotent stem cell-like progenitor population that contributes newly differentiated cells to the posterior end of the embryo. Here, in vivo analyses show that proliferation is compartmentalized at the posterior end of the zebrafish embryo via regulated expression of mitotic factor Cdc25a. Furthermore, compartmentalization of proliferation during embryogenesis is critical to both body extension and muscle cell fate. This study reveals an unexpected link between precise regulation of the cell cycle and differentiation from multipotency in the vertebrate embryo. The vertebrate body forms from a multipotent stem cell-like progenitor population that progressively contributes newly differentiated cells to the most posterior end of the embryo. How the progenitor population balances proliferation and other cellular functions is unknown due to the difficulty of analyzing cell division in vivo. Here, we show that proliferation is compartmentalized at the posterior end of the embryo during early zebrafish development by the regulated expression of cdc25a, a key controller of mitotic entry. Through the use of a transgenic line that misexpresses cdc25a, we show that this compartmentalization is critical for the formation of the posterior body. Upon misexpression of cdc25a, several essential T-box transcription factors are abnormally expressed, including Spadetail/Tbx16, which specifically prevents the normal onset of myoD transcription, leading to aberrant muscle formation. Our results demonstrate that compartmentalization of proliferation during early embryogenesis is critical for both extension of the vertebrate body and differentiation of the multipotent posterior progenitor cells to the muscle cell fate.
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Affiliation(s)
- Cortney M Bouldin
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
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Dumollard R, Hebras C, Besnardeau L, McDougall A. Beta-catenin patterns the cell cycle during maternal-to-zygotic transition in urochordate embryos. Dev Biol 2013; 384:331-42. [PMID: 24140189 DOI: 10.1016/j.ydbio.2013.10.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 09/18/2013] [Accepted: 10/03/2013] [Indexed: 11/18/2022]
Abstract
During the transition from maternal to zygotic control of development, cell cycle length varies in different lineages, and this is important for their fates and functions. The maternal to zygotic transition (MZT) in metazoan embryos involves a profound remodeling of the cell cycle: S phase length increases then G2 is introduced. Although β-catenin is the master regulator of endomesoderm patterning at MZT in all metazoans, the influence of maternal β-catenin on the cell cycle at MZT remains poorly understood. By studying urochordate embryogenesis we found that cell cycle remodeling during MZT begins with the formation of 3 mitotic domains at the 16-cell stage arising from differential S phase lengthening, when endomesoderm is specified. Then, at the 64-cell stage, a G2 phase is introduced in the endoderm lineage during its specification. Strikingly, these two phases of cell cycle remodeling are patterned by β-catenin-dependent transcription. Functional analysis revealed that, at the 16-cell stage, β-catenin speeds up S phase in the endomesoderm. In contrast, two cell cycles later at gastrulation, nuclear β-catenin induces endoderm fate and delays cell division. Such interphase lengthening in invaginating cells is known to be a requisite for gastrulation movements. Therefore, in basal chordates β-catenin has a dual role to specify germ layers and remodel the cell cycle.
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Affiliation(s)
- Rémi Dumollard
- UMR 7009, UPMC University, Paris 06, France; Centre National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France.
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