1
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Kojima ML, Hoppe C, Giraldez AJ. The maternal-to-zygotic transition: reprogramming of the cytoplasm and nucleus. Nat Rev Genet 2025; 26:245-267. [PMID: 39587307 PMCID: PMC11928286 DOI: 10.1038/s41576-024-00792-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2024] [Indexed: 11/27/2024]
Abstract
A fertilized egg is initially transcriptionally silent and relies on maternally provided factors to initiate development. For embryonic development to proceed, the oocyte-inherited cytoplasm and the nuclear chromatin need to be reprogrammed to create a permissive environment for zygotic genome activation (ZGA). During this maternal-to-zygotic transition (MZT), which is conserved in metazoans, transient totipotency is induced and zygotic transcription is initiated to form the blueprint for future development. Recent technological advances have enhanced our understanding of MZT regulation, revealing common themes across species and leading to new fundamental insights about transcription, mRNA decay and translation.
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Affiliation(s)
- Mina L Kojima
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Caroline Hoppe
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Antonio J Giraldez
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA.
- Yale Stem Cell Center, Yale University School of Medicine, New Haven, CT, USA.
- Yale Cancer Center, Yale University School of Medicine, New Haven, CT, USA.
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2
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Cardamone F, Piva A, Löser E, Eichenberger B, Romero-Mulero MC, Zenk F, Shields EJ, Cabezas-Wallscheid N, Bonasio R, Tiana G, Zhan Y, Iovino N. Chromatin landscape at cis-regulatory elements orchestrates cell fate decisions in early embryogenesis. Nat Commun 2025; 16:3007. [PMID: 40148291 PMCID: PMC11950382 DOI: 10.1038/s41467-025-57719-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2024] [Accepted: 03/03/2025] [Indexed: 03/29/2025] Open
Abstract
The establishment of germ layers during early development is crucial for body formation. The Drosophila zygote serves as a model for investigating these transitions in relation to the chromatin landscape. However, the cellular heterogeneity of the blastoderm embryo poses a challenge for gaining mechanistic insights. Using 10× Multiome, we simultaneously analyzed the in vivo epigenomic and transcriptomic states of wild-type, E(z)-, and CBP-depleted embryos during zygotic genome activation at single-cell resolution. We found that pre-zygotic H3K27me3 safeguards tissue-specific gene expression by modulating cis-regulatory elements. Furthermore, we demonstrate that CBP is essential for cell fate specification functioning as a transcriptional activator by stabilizing transcriptional factors binding at key developmental genes. Surprisingly, while CBP depletion leads to transcriptional arrest, chromatin accessibility continues to progress independently through the retention of stalled RNA Polymerase II. Our study reveals fundamental principles of chromatin-mediated gene regulation essential for establishing and maintaining cellular identities during early embryogenesis.
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Affiliation(s)
- Francesco Cardamone
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
- International Max Planck Research School of Immunobiology, Epigenetics and Metabolism (IMPRS-IEM), Freiburg, Germany
| | - Annamaria Piva
- Department of Experimental Oncology, European Institute of Oncology, IRCCS, Milan, Italy
| | - Eva Löser
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
| | - Bastian Eichenberger
- Department of Experimental Oncology, European Institute of Oncology, IRCCS, Milan, Italy
| | - Mari Carmen Romero-Mulero
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Fides Zenk
- Epigenomics of Neurodevelopment, Brain Mind Institute, School of Life Sciences, EPFL - Ecole Polytechnique Federal Lusanne, Ecublens, Switzerland
| | - Emily J Shields
- Epigenetics Institute, Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
- Department of Urology and Institute of Neuropathology, Medical Center-University of Freiburg, Freiburg, Germany
| | - Nina Cabezas-Wallscheid
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
- Laboratory of Stem Cell Biology and Ageing, Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETH Zürich), Zürich, Switzerland
- Centre for Integrative Biological Signalling Studies (CIBSS), Freiburg, Germany
| | - Roberto Bonasio
- Epigenetics Institute, Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Guido Tiana
- Università degli Studi di Milano and INFN, Milan, Italy
| | - Yinxiu Zhan
- Department of Experimental Oncology, European Institute of Oncology, IRCCS, Milan, Italy.
| | - Nicola Iovino
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany.
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3
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Amiri EE, Tenger-Trolander A, Li M, Thomas Julian A, Kasan K, Sanders SA, Blythe S, Schmidt-Ott U. Conservation of symmetry breaking at the level of chromatin accessibility between fly species with unrelated anterior determinants. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2025.01.13.632851. [PMID: 39868093 PMCID: PMC11760685 DOI: 10.1101/2025.01.13.632851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/28/2025]
Abstract
Establishing the anterior-posterior body axis is a fundamental process during embryogenesis, and the fruit fly, Drosophila melanogaster, provides one of the best-known case studies of this process. In Drosophila, localized mRNA of bicoid serves as anterior determinant (AD). Bicoid engages in a concentration-dependent competition with nucleosomes and initiates symmetry-breaking along the AP axis by promoting chromatin accessibility at the loci of transcription factor (TF) genes that are expressed in the anterior of the embryo. However, ADs of other fly species are unrelated and structurally distinct, and little is known about how they function. We addressed this question in the moth fly, Clogmia albipunctata, in which a maternally expressed transcript isoform of the pair-rule segmentation gene odd-paired is localized in the anterior egg and has been co-opted as AD. We provide a de novo assembly and annotation of the Clogmia genome and describe how knockdown of zelda and maternal odd-paired transcript affect chromatin accessibility and expression of TF-encoding loci. The results of these experiments suggest direct roles of Cal-Zld in opening and closing chromatin during nuclear cleavage cycles and show that Clogmia's maternal odd-paired activity promotes chromatin accessibility and anterior expression during the early phase of zygotic genome activation at Clogmia's homeobrain and sloppy-paired loci. We conclude that unrelated dipteran ADs initiate anterior-posterior axis-specification at the level of enhancer accessibility and that homeobrain and sloppy-paired homologs may serve a more widely conserved role in the initiation of anterior pattern formation given their early anterior expression and function in head development in other insects.
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Affiliation(s)
- Ezra E. Amiri
- The University of Chicago, Department of Organismal Biology and Anatomy, 1027 East 57 Street, Chicago, Illinois 60637, USA
| | - Ayse Tenger-Trolander
- The University of Chicago, Department of Organismal Biology and Anatomy, 1027 East 57 Street, Chicago, Illinois 60637, USA
| | - Muzi Li
- The University of Chicago, Department of Organismal Biology and Anatomy, 1027 East 57 Street, Chicago, Illinois 60637, USA
| | - Alexander Thomas Julian
- Illinois Institute of Technology, Department of Biology, 3105 South Dearborn Street, Chicago, Illinois 60616, USA
| | - Koray Kasan
- The University of Chicago, Department of Organismal Biology and Anatomy, 1027 East 57 Street, Chicago, Illinois 60637, USA
| | - Sheri A. Sanders
- Notre Dame University, 252 Galvin Life Science Center/Freimann Life Science Center, Notre Dame, Indiana 46556, USA
| | - Shelby Blythe
- Northwestern University, Department of Molecular Biosciences, 2205 Tech Drive, Evanston, Illinois 60208, USA
- Northwestern University and The University of Chicago, National Institute for Theory and Mathematics in Biology, 875 North Michigan Avenue, Suite 3500, Chicago, Illinois 60611, USA
| | - Urs Schmidt-Ott
- The University of Chicago, Department of Organismal Biology and Anatomy, 1027 East 57 Street, Chicago, Illinois 60637, USA
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4
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Biel N, Rashid F, Natua S, Wang TY, Chou TF, Nguyen TVP, Golding I, Kalsotra A, Sokac AM. Reducing Cofilin dosage makes embryos resilient to heat stress. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2025.01.02.631102. [PMID: 39803506 PMCID: PMC11722379 DOI: 10.1101/2025.01.02.631102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/23/2025]
Abstract
In addition to regulating the actin cytoskeleton, Cofilin also senses and responds to environmental stress. Cofilin can promote cell survival or death depending on context. Yet, many aspects of Cofilin's role in survival need clarification. Here, we show that exposing early Drosophila embryos to mild heat stress (32°C) induces a Cofilin-mediated Actin Stress Response and upregulation of heat- and ER- stress response genes. However, these responses do not alleviate the negative impacts of heat exposure. Instead, heat stressed embryos show downregulation of hundreds of developmental genes, including determinants of the embryonic body plan, and are less likely to hatch as larvae and adults. Remarkably, reducing Cofilin dosage blunts induction of all stress response pathways, mitigates downregulation of developmental genes, and completely rescues survival. Thus, Cofilin intersects with multiple stress response pathways, and modulates the transcriptomic response to heat stress. Strikingly, Cofilin knockdown emerges as a potent pro-survival manipulation for embryos.
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Affiliation(s)
- Natalie Biel
- Integrative Molecular and Biomedical Sciences Program, Baylor College of Medicine, Houston, TX, 77030 USA
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Faizan Rashid
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- These authors contributed equally
| | - Subhashis Natua
- Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- These authors contributed equally
| | - Ting-Yu Wang
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Tsui-Fen Chou
- Proteome Exploration Laboratory, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Thu Vu Phuc Nguyen
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Present address: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Ido Golding
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Department of Microbiology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Auinash Kalsotra
- Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Division of Nutritional Sciences, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Anna Marie Sokac
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Lead contact
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5
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Kemp JP, Geisler MS, Hoover M, Cho CY, O'Farrell PH, Marzluff WF, Duronio RJ. Cell cycle-regulated transcriptional pausing of Drosophila replication-dependent histone genes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.12.16.628706. [PMID: 39763942 PMCID: PMC11702538 DOI: 10.1101/2024.12.16.628706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/18/2025]
Abstract
Coordinated expression of replication-dependent (RD) histones genes occurs within the Histone Locus Body (HLB) during S phase, but the molecular steps in transcription that are cell cycle regulated are unknown. We report that Drosophila RNA Pol II promotes HLB formation and is enriched in the HLB outside of S phase, including G1-arrested cells that do not transcribe RD histone genes. In contrast, the transcription elongation factor Spt6 is enriched in HLBs only during S phase. Proliferating cells in the wing and eye primordium express full-length histone mRNAs during S phase but express only short nascent transcripts in cells in G1 or G2 consistent with these transcripts being paused and then terminated. Full-length transcripts are produced when Cyclin E/Cdk2 is activated as cells enter S phase. Thus, activation of transcription elongation by Cyclin E/Cdk2 and not recruitment of RNA pol II to the HLB is the critical step that links histone gene expression to cell cycle progression in Drosophila.
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Affiliation(s)
- James P Kemp
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, 27599 USA
| | - Mark S Geisler
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, 27599 USA
| | - Mia Hoover
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599 USA
| | - Chun-Yi Cho
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158
| | - Patrick H O'Farrell
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158
| | - William F Marzluff
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, 27599 USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, 27599 USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599 USA
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, 27599 USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599 USA
| | - Robert J Duronio
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, 27599 USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, 27599 USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599 USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599 USA
- Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599 USA
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6
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Bhatt AD, Brown MG, Wackford AB, Shindo Y, Amodeo AA. Local nuclear to cytoplasmic ratio regulates H3.3 incorporation via cell cycle state during zygotic genome activation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.15.603602. [PMID: 39071352 PMCID: PMC11275841 DOI: 10.1101/2024.07.15.603602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Early embryos often have unique chromatin states prior to zygotic genome activation (ZGA). In Drosophila, ZGA occurs after 13 reductive nuclear divisions during which the nuclear to cytoplasmic (N/C) ratio grows exponentially. Previous work found that histone H3 chromatin incorporation decreases while its variant H3.3 increases leading up to ZGA. In other cell types, H3.3 is associated with sites of active transcription and heterochromatin, suggesting a link between H3.3 and ZGA. Here, we test what factors regulate H3.3 incorporation at ZGA. We find that H3 nuclear availability falls more rapidly than H3.3 leading up to ZGA. We generate H3/H3.3 chimeric proteins at the endogenous H3.3A locus and observe that chaperone binding, but not gene structure, regulates H3.3 behavior. We identify the N/C ratio as a major determinant of H3.3 incorporation. To isolate how the N/C ratio regulates H3.3 incorporation we test the roles of genomic content, zygotic transcription, and cell cycle state. We determine that cell cycle regulation, but not H3 availability or transcription, controls H3.3 incorporation. Overall, we propose that local N/C ratios control histone variant usage via cell cycle state during ZGA.
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Affiliation(s)
- Anusha D. Bhatt
- Department of Biological sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Madeleine G. Brown
- Department of Biological sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Aurora B. Wackford
- Department of Biological sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Yuki Shindo
- Department of Biological sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Amanda A. Amodeo
- Department of Biological sciences, Dartmouth College, Hanover, NH 03755, USA
- Lead contact
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7
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Degen EA, Croslyn C, Mangan NM, Blythe SA. Bicoid-nucleosome competition sets a concentration threshold for transcription constrained by genome replication. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.12.10.627802. [PMID: 39713295 PMCID: PMC11661180 DOI: 10.1101/2024.12.10.627802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/24/2024]
Abstract
Transcription factors (TFs) regulate gene expression despite constraints from chromatin structure and the cell cycle. Here we examine the concentration-dependent regulation of hunchback by the Bicoid morphogen through a combination of quantitative imaging, mathematical modeling and epigenomics in Drosophila embryos. By live imaging of MS2 reporters, we find that, following mitosis, the timing of transcriptional activation driven by the hunchback P2 (hb P2) enhancer directly reflects Bicoid concentration. We build a stochastic model that can explain in vivo onset time distributions by accounting for both the competition between Bicoid and nucleosomes at hb P2 and a negative influence of DNA replication on transcriptional elongation. Experimental modulation of nucleosome stability alters onset time distributions and the posterior boundary of hunchback expression. We conclude that TF-nucleosome competition is the molecular mechanism whereby the Bicoid morphogen gradient specifies the posterior boundary of hunchback expression.
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Affiliation(s)
- Eleanor A Degen
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston Illinois 60208, USA
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA
| | - Corinne Croslyn
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston Illinois 60208, USA
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA
| | - Niall M Mangan
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois 60208, USA
- National Institute for Theory and Mathematics in Biology, Northwestern University and The University of Chicago, Chicago, IL, USA
| | - Shelby A Blythe
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA
- National Institute for Theory and Mathematics in Biology, Northwestern University and The University of Chicago, Chicago, IL, USA
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8
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Zhang G, Miao Y, Song Y, Wang L, Li Y, Zhu Y, Zhang W, Sun Q, Chen D. HIRA and dPCIF1 coordinately establish totipotent chromatin and control orderly ZGA in Drosophila embryos. Proc Natl Acad Sci U S A 2024; 121:e2410261121. [PMID: 39541353 PMCID: PMC11588057 DOI: 10.1073/pnas.2410261121] [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: 05/23/2024] [Accepted: 09/24/2024] [Indexed: 11/16/2024] Open
Abstract
Early embryos undergo profound changes in their genomic architecture to establish the totipotent state, enabling pioneer factors to access chromatin and drive zygotic genome activation (ZGA). However, the mechanisms by which the totipotent state is established and properly interpreted by pioneer factors to allow orderly ZGA remain unknown. Here, we identify the H3.3-specific chaperone HIRA as a factor involving establishing totipotent-state chromatin in Drosophila early embryos. Through cophase separation with HIRA, the pioneer factor GAGA factor (GAF) efficiently binds to H3.3-marked nucleosomes to activate major-wave zygotic genes. Importantly, dPCIF1, a chromatin-associated protein, antagonized the GAF-HIRA interaction by competitively binding to HIRA, thereby restricting GAF on earlier chromatin and avoiding premature ZGA. Hence, the coordinated action of HIRA and dPCIF1 ensures sequential ZGA from the minor to major wave in early embryos. This study provides insights into understanding how a totipotent state is established and properly controlled during ZGA.
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Affiliation(s)
- Guoqiang Zhang
- Institute of Biomedical Research, Yunnan University, Kunming650500, China
| | - Yaqi Miao
- Institute of Biomedical Research, Yunnan University, Kunming650500, China
| | - Yuan Song
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
- School of Life Sciences, University of Chinese Academy of Sciences, Beijing100049, China
| | - Liangliang Wang
- Institute of Biomedical Research, Yunnan University, Kunming650500, China
| | - Yawei Li
- Institute of Biomedical Research, Yunnan University, Kunming650500, China
| | - Yuanxiang Zhu
- Institute of Biomedical Research, Yunnan University, Kunming650500, China
| | - Wenxin Zhang
- Institute of Biomedical Research, Yunnan University, Kunming650500, China
| | - Qinmiao Sun
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
- School of Life Sciences, University of Chinese Academy of Sciences, Beijing100049, China
- Institute of Stem Cells and Regeneration, Chinese Academy of Sciences, Beijing100101, China
| | - Dahua Chen
- Institute of Biomedical Research, Yunnan University, Kunming650500, China
- Southwest United Graduate School, Kunming650500, China
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9
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Ciabrelli F, Atinbayeva N, Pane A, Iovino N. Epigenetic inheritance and gene expression regulation in early Drosophila embryos. EMBO Rep 2024; 25:4131-4152. [PMID: 39285248 PMCID: PMC11467379 DOI: 10.1038/s44319-024-00245-z] [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: 02/22/2024] [Revised: 05/13/2024] [Accepted: 08/21/2024] [Indexed: 10/12/2024] Open
Abstract
Precise spatiotemporal regulation of gene expression is of paramount importance for eukaryotic development. The maternal-to-zygotic transition (MZT) during early embryogenesis in Drosophila involves the gradual replacement of maternally contributed mRNAs and proteins by zygotic gene products. The zygotic genome is transcriptionally activated during the first 3 hours of development, in a process known as "zygotic genome activation" (ZGA), by the orchestrated activities of a few pioneer factors. Their decisive role during ZGA has been characterized in detail, whereas the contribution of chromatin factors to this process has been historically overlooked. In this review, we aim to summarize the current knowledge of how chromatin regulation impacts the first stages of Drosophila embryonic development. In particular, we will address the following questions: how chromatin factors affect ZGA and transcriptional silencing, and how genome architecture promotes the integration of these processes early during development. Remarkably, certain chromatin marks can be intergenerationally inherited, and their presence in the early embryo becomes critical for the regulation of gene expression at later stages. Finally, we speculate on the possible roles of these chromatin marks as carriers of epialleles during transgenerational epigenetic inheritance (TEI).
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Affiliation(s)
- Filippo Ciabrelli
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany
| | - Nazerke Atinbayeva
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany
| | - Attilio Pane
- Institute of Biomedical Sciences/UFRJ, 21941902, Rio de Janeiro, Brazil
| | - Nicola Iovino
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany.
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10
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McCaw BA, Leonard AM, Stevenson TJ, Lancaster LT. A role of epigenetic mechanisms in regulating female reproductive responses to temperature in a pest beetle. INSECT MOLECULAR BIOLOGY 2024; 33:516-533. [PMID: 38864655 DOI: 10.1111/imb.12933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 05/23/2024] [Indexed: 06/13/2024]
Abstract
Many species are threatened by climate change and must rapidly respond to survive in changing environments. Epigenetic modifications, such as DNA methylation, can facilitate plastic responses by regulating gene expression in response to environmental cues. Understanding epigenetic responses is therefore essential for predicting species' ability to rapidly adapt in the context of global environmental change. Here, we investigated the functional significance of different methylation-associated cellular processes on temperature-dependent life history in seed beetles, Callosobruchus maculatus Fabricius 1775 (Coleoptera: Bruchidae). We assessed changes under thermal stress in (1) DNA methyltransferase (Dnmt1 and Dnmt2) expression levels, (2) genome-wide methylation and (3) reproductive performance, with (2) and (3) following treatment with 3-aminobenzamide (3AB) and zebularine (Zeb) over two generations. These drugs are well-documented to alter DNA methylation across the tree of life. We found that Dnmt1 and Dnmt2 were expressed throughout the body in males and females, but were highly expressed in females compared with males and exhibited temperature dependence. However, whole-genome methylation did not significantly vary with temperature, and only marginally or inconclusively with drug treatment. Both 3AB and Zeb led to profound temperature-dependent shifts in female reproductive life history trade-off allocation, often increasing fitness compared with control beetles. Mismatch between magnitude of treatment effects on DNA methylation versus life history effects suggest potential of 3AB and Zeb to alter reproductive trade-offs via changes in DNA repair and recycling processes, rather than or in addition to (subtle) changes in DNA methylation. Together, our results suggest that epigenetic mechanisms relating to Dnmt expression, DNA repair and recycling pathways, and possibly DNA methylation, are strongly implicated in modulating insect life history trade-offs in response to temperature change.
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Affiliation(s)
- Beth A McCaw
- School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland
| | - Aoife M Leonard
- Centre for Evolutionary Hologenomics, GLOBE Institute, University of Copenhagen, Copenhagen, Denmark
| | - Tyler J Stevenson
- School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland
| | - Lesley T Lancaster
- School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland
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11
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Goyal M, Maggert K. Maternally-Activated Lineage Tracing ( Raeppli ) To Determine Anlagen Size in Drosophila. MICROPUBLICATION BIOLOGY 2024; 2024. [PMID: 39267614 PMCID: PMC11391275 DOI: 10.17912/micropub.biology.001185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2024] [Revised: 05/14/2024] [Accepted: 08/24/2024] [Indexed: 09/15/2024]
Abstract
We used Raeppli , a sophisticated fluorescent lineage tracing system developed for Drosophila , to map cell clones beginning at the earliest possible stage in development. By expression of the ϕC31 Integrase (the final step in activating lineage marking) in nurse cells and oocytes, we reduced the methodological and biological variation in cell lineage analysis. We characterized the number of cells in fully-developed larval salivary glands, and thereby inferred the number of cells in embryonic anlage, the number of divisions during differentiation, and the variation in clonal behavior. This approach - novel for Raeppli - represents a powerful addition to lineage analysis in Drosophila .
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Affiliation(s)
- Michell Goyal
- University of Arizona, Tucson, Arizona, United States
| | - Keith Maggert
- Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States
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12
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Hurton MD, Miller JM, Lee MT. H3K4me2 distinguishes a distinct class of enhancers during the maternal-to-zygotic transition. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.26.609713. [PMID: 39253505 PMCID: PMC11383010 DOI: 10.1101/2024.08.26.609713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/11/2024]
Abstract
After egg fertilization, an initially silent embryonic genome is transcriptionally activated during the maternal-to-zygotic transition. In zebrafish, maternal vertebrate pluripotency factors Nanog, Pou5f3 (OCT4 homolog), and Sox19b (SOX2 homolog) (NPS) play essential roles in orchestrating embryonic genome activation, acting as "pioneers" that open condensed chromatin and mediate acquisition of activating histone modifications. However, some embryonic gene transcription still occurs in the absence of these factors, suggesting the existence of other mechanisms regulating genome activation. To identify chromatin signatures of these unknown pathways, we profiled the histone modification landscape of zebrafish embryos using CUT&RUN. Our regulatory map revealed two subclasses of enhancers distinguished by presence or absence of H3K4me2. Enhancers lacking H3K4me2 tend to require NPS factors for de novo activation, while enhancers bearing H3K4me2 are epigenetically bookmarked by DNA hypomethylation to recapitulate gamete activity in the embryo, independent of NPS pioneering. Thus, parallel enhancer activation pathways combine to induce transcriptional reprogramming to pluripotency in the early embryo.
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Affiliation(s)
- Matthew D Hurton
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh PA 15213 U.S.A
| | - Jennifer M Miller
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh PA 15213 U.S.A
| | - Miler T Lee
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh PA 15213 U.S.A
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13
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Mikucki EE, O’Leary TS, Lockwood BL. Heat tolerance, oxidative stress response tuning and robust gene activation in early-stage Drosophila melanogaster embryos. Proc Biol Sci 2024; 291:20240973. [PMID: 39163981 PMCID: PMC11335408 DOI: 10.1098/rspb.2024.0973] [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: 04/26/2024] [Revised: 06/11/2024] [Accepted: 07/26/2024] [Indexed: 08/22/2024] Open
Abstract
In organisms with complex life cycles, life stages that are most susceptible to environmental stress may determine species persistence in the face of climate change. Early embryos of Drosophila melanogaster are particularly sensitive to acute heat stress, yet tropical embryos have higher heat tolerance than temperate embryos, suggesting adaptive variation in embryonic heat tolerance. We compared transcriptomic responses to heat stress among tropical and temperate embryos to elucidate the gene regulatory basis of divergence in embryonic heat tolerance. The transcriptomes of tropical and temperate embryos differed in both constitutive and heat-stress-induced responses of the expression of relatively few genes, including genes involved in oxidative stress. Most of the transcriptomic response to heat stress was shared among all embryos. Embryos shifted the expression of thousands of genes, including increases in the expression of heat shock genes, suggesting robust zygotic gene activation and demonstrating that, contrary to previous reports, early embryos are not transcriptionally silent. The involvement of oxidative stress genes corroborates recent reports on the critical role of redox homeostasis in coordinating developmental transitions. By characterizing adaptive variation in the transcriptomic basis of embryonic heat tolerance, this study is a novel contribution to the literature on developmental physiology and developmental genetics.
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Affiliation(s)
- Emily E. Mikucki
- Department of Biology, University of Vermont, Burlington, VT, USA
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14
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Munshi R. How Transcription Factor Clusters Shape the Transcriptional Landscape. Biomolecules 2024; 14:875. [PMID: 39062589 PMCID: PMC11274464 DOI: 10.3390/biom14070875] [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: 06/01/2024] [Revised: 07/14/2024] [Accepted: 07/16/2024] [Indexed: 07/28/2024] Open
Abstract
In eukaryotic cells, gene transcription typically occurs in discrete periods of promoter activity, interspersed with intervals of inactivity. This pattern deviates from simple stochastic events and warrants a closer examination of the molecular interactions that activate the promoter. Recent studies have identified transcription factor (TF) clusters as key precursors to transcriptional bursting. Often, these TF clusters form at chromatin segments that are physically distant from the promoter, making changes in chromatin conformation crucial for promoter-TF cluster interactions. In this review, I explore the formation and constituents of TF clusters, examining how the dynamic interplay between chromatin architecture and TF clustering influences transcriptional bursting. Additionally, I discuss techniques for visualizing TF clusters and provide an outlook on understanding the remaining gaps in this field.
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Affiliation(s)
- Rahul Munshi
- Joseph Henry Laboratories of Physics and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
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15
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Brantley S, Di Talia S. The maternal-to-zygotic transition. Curr Biol 2024; 34:R519-R523. [PMID: 38834020 DOI: 10.1016/j.cub.2024.04.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
Rapid cleavage divisions and the transition from maternal to zygotic control of gene expression are the hallmarks of early embryonic development in most species. Early development in insects, fish and amphibians is characterized by several short cell cycles with no gap phases, necessary for the rapid production of cells prior to patterning and morphogenesis. Maternal mRNAs and proteins loaded into the egg during oogenesis are essential to drive these rapid early divisions. Once the function of these maternal inputs is complete, the maternal-to-zygotic transition (MZT) marks the handover of developmental control to the gene products synthesized from the zygotic genome. The MZT requires three major events: the removal of a subset of maternal mRNAs, the initiation of zygotic transcription, and the remodeling of the cell cycle. In each species, the MZT occurs at a highly reproducible time during development due to a series of feedback mechanisms that tightly couple these three processes. Dissecting these feedback mechanisms and their spatiotemporal control will be essential to understanding the control of the MZT. In this primer, we outline the mechanisms that govern the major events of the MZT across species and highlight the role of feedback mechanisms that ensure the MZT is precisely timed and orchestrated.
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Affiliation(s)
- Susanna Brantley
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27705, USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27705, USA.
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16
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Stoeber S, Godin H, Xu C, Bai L. Pioneer factors: nature or nurture? Crit Rev Biochem Mol Biol 2024; 59:139-153. [PMID: 38778580 PMCID: PMC11444900 DOI: 10.1080/10409238.2024.2355885] [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: 03/03/2024] [Revised: 04/30/2024] [Accepted: 05/13/2024] [Indexed: 05/25/2024]
Abstract
Chromatin is densely packed with nucleosomes, which limits the accessibility of many chromatin-associated proteins. Pioneer factors (PFs) are usually viewed as a special group of sequence-specific transcription factors (TFs) that can recognize nucleosome-embedded motifs, invade compact chromatin, and generate open chromatin regions. Through this process, PFs initiate a cascade of events that play key roles in gene regulation and cell differentiation. A current debate in the field is if PFs belong to a unique subset of TFs with intrinsic "pioneering activity", or if all TFs have the potential to function as PFs within certain cellular contexts. There are also different views regarding the key feature(s) that define pioneering activity. In this review, we present evidence from the literature related to these alternative views and discuss how to potentially reconcile them. It is possible that both intrinsic properties, like tight nucleosome binding and structural compatibility, and cellular conditions, like concentration and co-factor availability, are important for PF function.
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Affiliation(s)
- Shane Stoeber
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA
| | - Holly Godin
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA
| | - Cheng Xu
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA
| | - Lu Bai
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
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17
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Budzyński MA, Wong AK, Faghihi A, Teves SS. A dynamic role for transcription factors in restoring transcription through mitosis. Biochem Soc Trans 2024; 52:821-830. [PMID: 38526206 PMCID: PMC11088908 DOI: 10.1042/bst20231022] [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: 12/11/2023] [Revised: 03/01/2024] [Accepted: 03/06/2024] [Indexed: 03/26/2024]
Abstract
Mitosis involves intricate steps, such as DNA condensation, nuclear membrane disassembly, and phosphorylation cascades that temporarily halt gene transcription. Despite this disruption, daughter cells remarkably retain the parent cell's gene expression pattern, allowing for efficient transcriptional memory after division. Early studies in mammalian cells suggested that transcription factors (TFs) mark genes for swift reactivation, a phenomenon termed 'mitotic bookmarking', but conflicting data emerged regarding TF presence on mitotic chromosomes. Recent advancements in live-cell imaging and fixation-free genomics challenge the conventional belief in universal formaldehyde fixation, revealing dynamic TF interactions during mitosis. Here, we review recent studies that provide examples of at least four modes of TF-DNA interaction during mitosis and the molecular mechanisms that govern these interactions. Additionally, we explore the impact of these interactions on transcription initiation post-mitosis. Taken together, these recent studies call for a paradigm shift toward a dynamic model of TF behavior during mitosis, underscoring the need for incorporating dynamics in mechanistic models for re-establishing transcription post-mitosis.
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Affiliation(s)
- Marek A. Budzyński
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Alexander K.L. Wong
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Armin Faghihi
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Sheila S. Teves
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
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18
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Ahmad K, Brahma S, Henikoff S. Epigenetic pioneering by SWI/SNF family remodelers. Mol Cell 2024; 84:194-201. [PMID: 38016477 PMCID: PMC10842064 DOI: 10.1016/j.molcel.2023.10.045] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/20/2023] [Accepted: 10/31/2023] [Indexed: 11/30/2023]
Abstract
In eukaryotic genomes, transcriptional machinery and nucleosomes compete for binding to DNA sequences; thus, a crucial aspect of gene regulatory element function is to modulate chromatin accessibility for transcription factor (TF) and RNA polymerase binding. Recent structural studies have revealed multiple modes of TF engagement with nucleosomes, but how initial "pioneering" results in steady-state DNA accessibility for further TF binding and RNA polymerase II (RNAPII) engagement has been unclear. Even less well understood is how distant sites of open chromatin interact with one another, such as when developmental enhancers activate promoters to release RNAPII for productive elongation. Here, we review evidence for the centrality of the conserved SWI/SNF family of nucleosome remodeling complexes, both in pioneering and in mediating enhancer-promoter contacts. Consideration of the nucleosome unwrapping and ATP hydrolysis activities of SWI/SNF complexes, together with their architectural features, may reconcile steady-state TF occupancy with rapid TF dynamics observed by live imaging.
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Affiliation(s)
- Kami Ahmad
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Sandipan Brahma
- University of Nebraska Medical Center, Department of Genetics, Cell Biology & Anatomy, Omaha, NE, USA
| | - Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA; Howard Hughes Medical Institute, Chevy Chase, MD, USA.
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19
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Hunt G, Vaid R, Pirogov S, Pfab A, Ziegenhain C, Sandberg R, Reimegård J, Mannervik M. Tissue-specific RNA Polymerase II promoter-proximal pause release and burst kinetics in a Drosophila embryonic patterning network. Genome Biol 2024; 25:2. [PMID: 38166964 PMCID: PMC10763363 DOI: 10.1186/s13059-023-03135-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Accepted: 11/30/2023] [Indexed: 01/05/2024] Open
Abstract
BACKGROUND Formation of tissue-specific transcriptional programs underlies multicellular development, including dorsoventral (DV) patterning of the Drosophila embryo. This involves interactions between transcriptional enhancers and promoters in a chromatin context, but how the chromatin landscape influences transcription is not fully understood. RESULTS Here we comprehensively resolve differential transcriptional and chromatin states during Drosophila DV patterning. We find that RNA Polymerase II pausing is established at DV promoters prior to zygotic genome activation (ZGA), that pausing persists irrespective of cell fate, but that release into productive elongation is tightly regulated and accompanied by tissue-specific P-TEFb recruitment. DV enhancers acquire distinct tissue-specific chromatin states through CBP-mediated histone acetylation that predict the transcriptional output of target genes, whereas promoter states are more tissue-invariant. Transcriptome-wide inference of burst kinetics in different cell types revealed that while DV genes are generally characterized by a high burst size, either burst size or frequency can differ between tissues. CONCLUSIONS The data suggest that pausing is established by pioneer transcription factors prior to ZGA and that release from pausing is imparted by enhancer chromatin state to regulate bursting in a tissue-specific manner in the early embryo. Our results uncover how developmental patterning is orchestrated by tissue-specific bursts of transcription from Pol II primed promoters in response to enhancer regulatory cues.
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Affiliation(s)
- George Hunt
- Department Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Roshan Vaid
- Department Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Sergei Pirogov
- Department Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Alexander Pfab
- Department Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | | | - Rickard Sandberg
- Department Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
| | - Johan Reimegård
- Department Cell and Molecular Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Mattias Mannervik
- Department Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
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20
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Geisler MS, Kemp JP, Duronio RJ. Histone locus bodies: a paradigm for how nuclear biomolecular condensates control cell cycle regulated gene expression. Nucleus 2023; 14:2293604. [PMID: 38095604 PMCID: PMC10730174 DOI: 10.1080/19491034.2023.2293604] [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] [Received: 09/29/2023] [Accepted: 12/07/2023] [Indexed: 12/18/2023] Open
Abstract
Histone locus bodies (HLBs) are biomolecular condensates that assemble at replication-dependent (RD) histone genes in animal cells. These genes produce unique mRNAs that are not polyadenylated and instead end in a conserved 3' stem loop critical for coordinated production of histone proteins during S phase of the cell cycle. Several evolutionarily conserved factors necessary for synthesis of RD histone mRNAs concentrate only in the HLB. Moreover, because HLBs are present throughout the cell cycle even though RD histone genes are only expressed during S phase, changes in HLB composition during cell cycle progression drive much of the cell cycle regulation of RD histone gene expression. Thus, HLBs provide a powerful opportunity to determine the cause-and-effect relationships between nuclear body formation and cell cycle regulated gene expression. In this review, we focus on progress during the last five years that has advanced our understanding of HLB biology.
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Affiliation(s)
- Mark S. Geisler
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, USA
| | - James P. Kemp
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
| | - Robert J. Duronio
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, USA
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
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21
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Messina O, Raynal F, Gurgo J, Fiche JB, Pancaldi V, Nollmann M. 3D chromatin interactions involving Drosophila insulators are infrequent but preferential and arise before TADs and transcription. Nat Commun 2023; 14:6678. [PMID: 37865700 PMCID: PMC10590426 DOI: 10.1038/s41467-023-42485-y] [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: 12/07/2022] [Accepted: 10/12/2023] [Indexed: 10/23/2023] Open
Abstract
In mammals, insulators contribute to the regulation of loop extrusion to organize chromatin into topologically associating domains. In Drosophila the role of insulators in 3D genome organization is, however, under current debate. Here, we addressed this question by combining bioinformatics analysis and multiplexed chromatin imaging. We describe a class of Drosophila insulators enriched at regions forming preferential chromatin interactions genome-wide. Notably, most of these 3D interactions do not involve TAD borders. Multiplexed imaging shows that these interactions occur infrequently, and only rarely involve multiple genomic regions coalescing together in space in single cells. Finally, we show that non-border preferential 3D interactions enriched in this class of insulators are present before TADs and transcription during Drosophila development. Our results are inconsistent with insulators forming stable hubs in single cells, and instead suggest that they fine-tune existing 3D chromatin interactions, providing an additional regulatory layer for transcriptional regulation.
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Affiliation(s)
- Olivier Messina
- Centre de Biologie Structurale, Univ Montpellier, CNRS UMR 5048, INSERM U1054, 34090, Montpellier, France
| | - Flavien Raynal
- CRCT, Université de Toulouse, Inserm, CNRS, Université Toulouse III-Paul Sabatier, Centre de Recherches en Cancérologie de Toulouse, Toulouse, France
| | - Julian Gurgo
- Centre de Biologie Structurale, Univ Montpellier, CNRS UMR 5048, INSERM U1054, 34090, Montpellier, France
| | - Jean-Bernard Fiche
- Centre de Biologie Structurale, Univ Montpellier, CNRS UMR 5048, INSERM U1054, 34090, Montpellier, France
| | - Vera Pancaldi
- CRCT, Université de Toulouse, Inserm, CNRS, Université Toulouse III-Paul Sabatier, Centre de Recherches en Cancérologie de Toulouse, Toulouse, France.
- Barcelona Supercomputing Center, Barcelona, Spain.
| | - Marcelo Nollmann
- Centre de Biologie Structurale, Univ Montpellier, CNRS UMR 5048, INSERM U1054, 34090, Montpellier, France.
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22
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Brennan KJ, Weilert M, Krueger S, Pampari A, Liu HY, Yang AWH, Morrison JA, Hughes TR, Rushlow CA, Kundaje A, Zeitlinger J. Chromatin accessibility in the Drosophila embryo is determined by transcription factor pioneering and enhancer activation. Dev Cell 2023; 58:1898-1916.e9. [PMID: 37557175 PMCID: PMC10592203 DOI: 10.1016/j.devcel.2023.07.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 05/09/2023] [Accepted: 07/13/2023] [Indexed: 08/11/2023]
Abstract
Chromatin accessibility is integral to the process by which transcription factors (TFs) read out cis-regulatory DNA sequences, but it is difficult to differentiate between TFs that drive accessibility and those that do not. Deep learning models that learn complex sequence rules provide an unprecedented opportunity to dissect this problem. Using zygotic genome activation in Drosophila as a model, we analyzed high-resolution TF binding and chromatin accessibility data with interpretable deep learning and performed genetic validation experiments. We identify a hierarchical relationship between the pioneer TF Zelda and the TFs involved in axis patterning. Zelda consistently pioneers chromatin accessibility proportional to motif affinity, whereas patterning TFs augment chromatin accessibility in sequence contexts where they mediate enhancer activation. We conclude that chromatin accessibility occurs in two tiers: one through pioneering, which makes enhancers accessible but not necessarily active, and the second when the correct combination of TFs leads to enhancer activation.
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Affiliation(s)
- Kaelan J Brennan
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Melanie Weilert
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Sabrina Krueger
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Anusri Pampari
- Department of Computer Science, Stanford University, Palo Alto, CA 94305, USA
| | - Hsiao-Yun Liu
- Department of Biology, New York University, New York, NY 10003, USA
| | - Ally W H Yang
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Jason A Morrison
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Timothy R Hughes
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | | | - Anshul Kundaje
- Department of Computer Science, Stanford University, Palo Alto, CA 94305, USA; Department of Genetics, Stanford University, Palo Alto, CA 94305, USA
| | - Julia Zeitlinger
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Pathology & Laboratory Medicine, The University of Kansas Medical Center, Kansas City, KS 66160, USA.
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23
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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 53706 USA
| | - Audrey J Marsh
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706 USA
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24
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Phelps WA, Hurton MD, Ayers TN, Carlson AE, Rosenbaum JC, Lee MT. Hybridization led to a rewired pluripotency network in the allotetraploid Xenopus laevis. eLife 2023; 12:e83952. [PMID: 37787392 PMCID: PMC10569791 DOI: 10.7554/elife.83952] [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: 10/04/2022] [Accepted: 10/02/2023] [Indexed: 10/04/2023] Open
Abstract
After fertilization, maternally contributed factors to the egg initiate the transition to pluripotency to give rise to embryonic stem cells, in large part by activating de novo transcription from the embryonic genome. Diverse mechanisms coordinate this transition across animals, suggesting that pervasive regulatory remodeling has shaped the earliest stages of development. Here, we show that maternal homologs of mammalian pluripotency reprogramming factors OCT4 and SOX2 divergently activate the two subgenomes of Xenopus laevis, an allotetraploid that arose from hybridization of two diploid species ~18 million years ago. Although most genes have been retained as two homeologous copies, we find that a majority of them undergo asymmetric activation in the early embryo. Chromatin accessibility profiling and CUT&RUN for modified histones and transcription factor binding reveal extensive differences in predicted enhancer architecture between the subgenomes, which likely arose through genomic disruptions as a consequence of allotetraploidy. However, comparison with diploid X. tropicalis and zebrafish shows broad conservation of embryonic gene expression levels when divergent homeolog contributions are combined, implying strong selection to maintain dosage in the core vertebrate pluripotency transcriptional program, amid genomic instability following hybridization.
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Affiliation(s)
- Wesley A Phelps
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
| | - Matthew D Hurton
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
| | - Taylor N Ayers
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
| | - Anne E Carlson
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
| | - Joel C Rosenbaum
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
| | - Miler T Lee
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
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25
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Ho EK, Oatman HR, McFann SE, Yang L, Johnson HE, Shvartsman SY, Toettcher JE. Dynamics of an incoherent feedforward loop drive ERK-dependent pattern formation in the early Drosophila embryo. Development 2023; 150:dev201818. [PMID: 37602510 PMCID: PMC10482391 DOI: 10.1242/dev.201818] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 08/11/2023] [Indexed: 08/22/2023]
Abstract
Positional information in development often manifests as stripes of gene expression, but how stripes form remains incompletely understood. Here, we use optogenetics and live-cell biosensors to investigate the posterior brachyenteron (byn) stripe in early Drosophila embryos. This stripe depends on interpretation of an upstream ERK activity gradient and the expression of two target genes, tailless (tll) and huckebein (hkb), that exert antagonistic control over byn. We find that high or low doses of ERK signaling produce transient or sustained byn expression, respectively. Although tll transcription is always rapidly induced, hkb converts graded ERK inputs into a variable time delay. Nuclei thus interpret ERK amplitude through the relative timing of tll and hkb transcription. Antagonistic regulatory paths acting on different timescales are hallmarks of an incoherent feedforward loop, which is sufficient to explain byn dynamics and adds temporal complexity to the steady-state model of byn stripe formation. We further show that 'blurring' of an all-or-none stimulus through intracellular diffusion non-locally produces a byn stripe. Overall, we provide a blueprint for using optogenetics to dissect developmental signal interpretation in space and time.
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Affiliation(s)
- Emily K. Ho
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Harrison R. Oatman
- Program in Quantitative and Computational Biology, Princeton University, Princeton, NJ 08544, USA
| | - Sarah E. McFann
- Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Liu Yang
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Heath E. Johnson
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Stanislav Y. Shvartsman
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Center for Computational Biology, Flatiron Institute - Simons Foundation, New York, NY 10010, USA
| | - Jared E. Toettcher
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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26
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Zhou CY, Heald R. Principles of genome activation in the early embryo. Curr Opin Genet Dev 2023; 81:102062. [PMID: 37339553 PMCID: PMC11419330 DOI: 10.1016/j.gde.2023.102062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 05/17/2023] [Accepted: 05/18/2023] [Indexed: 06/22/2023]
Abstract
A major hurdle in an embryo's life is the initiation of its own transcriptional program, a process termed Zygotic Genome Activation (ZGA). In many species, ZGA is intricately timed, with bulk transcription initiating at the end of a series of reductive cell divisions when cell cycle duration increases. At the same time, major changes in genome architecture give rise to chromatin states that are permissive to RNA polymerase II activity. Yet, we still do not understand the series of events that trigger gene expression at the right time and in the correct sequence. Here we discuss new discoveries that deepen our understanding of how zygotic genes are primed for transcription, and how these events are regulated by the cell cycle and nuclear import. Finally, we speculate on the evolutionary basis of ZGA timing as an exciting future direction for the field.
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Affiliation(s)
- Coral Y Zhou
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
| | - Rebecca Heald
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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27
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Ciabrelli F, Rabbani L, Cardamone F, Zenk F, Löser E, Schächtle MA, Mazina M, Loubiere V, Iovino N. CBP and Gcn5 drive zygotic genome activation independently of their catalytic activity. SCIENCE ADVANCES 2023; 9:eadf2687. [PMID: 37083536 PMCID: PMC10121174 DOI: 10.1126/sciadv.adf2687] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 03/17/2023] [Indexed: 05/03/2023]
Abstract
Zygotic genome activation (ZGA) is a crucial step of embryonic development. So far, little is known about the role of chromatin factors during this process. Here, we used an in vivo RNA interference reverse genetic screen to identify chromatin factors necessary for embryonic development in Drosophila melanogaster. Our screen reveals that histone acetyltransferases (HATs) and histone deacetylases are crucial ZGA regulators. We demonstrate that Nejire (CBP/EP300 ortholog) is essential for the acetylation of histone H3 lysine-18 and lysine-27, whereas Gcn5 (GCN5/PCAF ortholog) for lysine-9 of H3 at ZGA, with these marks being enriched at all actively transcribed genes. Nonetheless, these HATs activate distinct sets of genes. Unexpectedly, individual catalytic dead mutants of either Nejire or Gcn5 can activate zygotic transcription (ZGA) and transactivate a reporter gene in vitro. Together, our data identify Nejire and Gcn5 as key regulators of ZGA.
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Affiliation(s)
- Filippo Ciabrelli
- Department of Chromatin Regulation, Max Planck Institute for Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
| | - Leily Rabbani
- Department of Chromatin Regulation, Max Planck Institute for Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
| | - Francesco Cardamone
- Department of Chromatin Regulation, Max Planck Institute for Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
- University of Freiburg, Faculty of Biology, Freiburg im Breisgau, Germany
| | - Fides Zenk
- Department of Chromatin Regulation, Max Planck Institute for Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
| | - Eva Löser
- Department of Chromatin Regulation, Max Planck Institute for Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
| | - Melanie A. Schächtle
- Department of Chromatin Regulation, Max Planck Institute for Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
| | - Marina Mazina
- Department of Chromatin Regulation, Max Planck Institute for Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
| | | | - Nicola Iovino
- Department of Chromatin Regulation, Max Planck Institute for Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
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28
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Hadzhiev Y, Wheatley L, Cooper L, Ansaloni F, Whalley C, Chen Z, Finaurini S, Gustincich S, Sanges R, Burgess S, Beggs A, Müller F. The miR-430 locus with extreme promoter density forms a transcription body during the minor wave of zygotic genome activation. Dev Cell 2023; 58:155-170.e8. [PMID: 36693321 PMCID: PMC9904021 DOI: 10.1016/j.devcel.2022.12.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 08/10/2022] [Accepted: 12/16/2022] [Indexed: 01/24/2023]
Abstract
In anamniote embryos, the major wave of zygotic genome activation starts during the mid-blastula transition. However, some genes escape global genome repression, are activated substantially earlier, and contribute to the minor wave of genome activation. The mechanisms underlying the minor wave of genome activation are little understood. We explored the genomic organization and cis-regulatory mechanisms of a transcription body, in which the minor wave of genome activation is first detected in zebrafish. We identified the miR-430 cluster as having excessive copy number and the highest density of Pol-II-transcribed promoters in the genome, and this is required for forming the transcription body. However, this transcription body is not essential for, nor does it encompasse, minor wave transcription globally. Instead, distinct minor-wave-specific promoter architecture suggests that promoter-autonomous mechanisms regulate the minor wave of genome activation. The minor-wave-specific features also suggest distinct transcription initiation mechanisms between the minor and major waves of genome activation.
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Affiliation(s)
- Yavor Hadzhiev
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Lucy Wheatley
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Ledean Cooper
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Federico Ansaloni
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK; Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy; Central RNA Laboratory, Istituto Italiano di Tecnologia (IIT), 16163 Genoa, Italy
| | - Celina Whalley
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Zhelin Chen
- South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; Translational and Functional Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892-2152, USA
| | - Sara Finaurini
- Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
| | - Stefano Gustincich
- Central RNA Laboratory, Istituto Italiano di Tecnologia (IIT), 16163 Genoa, Italy
| | - Remo Sanges
- Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy; Central RNA Laboratory, Istituto Italiano di Tecnologia (IIT), 16163 Genoa, Italy
| | - Shawn Burgess
- Translational and Functional Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892-2152, USA
| | - Andrew Beggs
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Ferenc Müller
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK.
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29
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Colonnetta MM, Schedl P, Deshpande G. Germline/soma distinction in Drosophila embryos requires regulators of zygotic genome activation. eLife 2023; 12:78188. [PMID: 36598809 PMCID: PMC9812407 DOI: 10.7554/elife.78188] [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: 02/25/2022] [Accepted: 12/23/2022] [Indexed: 01/05/2023] Open
Abstract
In Drosophila melanogaster embryos, somatic versus germline identity is the first cell fate decision. Zygotic genome activation (ZGA) orchestrates regionalized gene expression, imparting specific identity on somatic cells. ZGA begins with a minor wave that commences at nuclear cycle (NC)8 under the guidance of chromatin accessibility factors (Zelda, CLAMP, GAF), followed by the major wave during NC14. By contrast, primordial germ cell (PGC) specification requires maternally deposited and posteriorly anchored germline determinants. This is accomplished by a centrosome coordinated release and sequestration of germ plasm during the precocious cellularization of PGCs in NC10. Here, we report a novel requirement for Zelda and CLAMP during the establishment of the germline/soma distinction. When their activity is compromised, PGC determinants are not properly sequestered, and specification is disrupted. Conversely, the spreading of PGC determinants from the posterior pole adversely influences transcription in the neighboring somatic nuclei. These reciprocal aberrations can be correlated with defects in centrosome duplication/separation that are known to induce inappropriate transmission of the germ plasm. Interestingly, consistent with the ability of bone morphogenetic protein (BMP) signaling to influence specification of embryonic PGCs, reduction in the transcript levels of a BMP family ligand, decapentaplegic (dpp), is exacerbated at the posterior pole.
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Affiliation(s)
- Megan M Colonnetta
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Paul Schedl
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Girish Deshpande
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
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30
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Datta RR, Onal P. In Situ Hybridization as a Method to Examine Gene Regulatory Activity In Vivo. Methods Mol Biol 2023; 2599:241-254. [PMID: 36427154 DOI: 10.1007/978-1-0716-2847-8_17] [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] [Indexed: 06/16/2023]
Abstract
Transcription factor-enhancer binding events are among the most well-studied protein-DNA interactions, allowing researchers to determine mechanisms of transcriptional activation or repression during development. While large-scale ChIP-sequence datasets, together with computational predictions and chromatin accessibility data, yield information on potential transcription factor binding activities, reporter gene assays provide measurable information on whether these binding activities are functional in particular cell types during development. Here, we present a detailed protocol to examine enhancer activity in Drosophila embryos using cloning, transgenesis, and in situ hybridization.
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Affiliation(s)
- Rhea R Datta
- Department of Biology, Hamilton College, Clinton, NY, USA.
| | - Pinar Onal
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA.
- Department of Molecular Biology and Genetics, Ihsan Dogramaci Bilkent University, Ankara, Turkey.
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31
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Abstract
The control of gene expression in eukaryotes relies on how transcription factors and RNA polymerases manipulate the structure of chromatin. These interactions are especially important in development as gene expression programs change. Chromatin generally limits the accessibility of DNA, and thus exposing sequences at regulatory elements is critical for gene expression. However, it is challenging to understand how transcription factors manipulate chromatin structure and the sequence of regulatory events. The Drosophila embryo has provided a powerful setting to directly observe the establishment and elaboration of chromatin features and experimentally test the causality of transcriptional events that are shared among many metazoans. The large embryo is tractable by live imaging, and a variety of well-developed tools allow the manipulation of factors during early development. The early embryo develops as a syncytium with rapid nuclear divisions and no zygotic transcription, with largely featureless chromatin. Thus, studies in this system have revealed the progression of genome activation triggered by pioneer factors that initiate DNA exposure at regulatory elements and the establishment of chromatin domains, including heterochromatin, the nucleolus, and nuclear bodies. The de novo emergence of nuclear structures in the early embryo reveals features of chromatin dynamics that are likely to be central to transcriptional regulation in all cells.
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Affiliation(s)
- Kami Ahmad
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA
| | - Steven Henikoff
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA
- Howard Hughes Medical Institute, 4000 Jones Bridge Road Chevy Chase, MD 20815-6789, USA
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32
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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: 27] [Impact Index Per Article: 9.0] [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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33
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A Tremendous Reorganization Journey for the 3D Chromatin Structure from Gametes to Embryos. Genes (Basel) 2022; 13:genes13101864. [PMID: 36292750 PMCID: PMC9602195 DOI: 10.3390/genes13101864] [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: 09/17/2022] [Revised: 10/02/2022] [Accepted: 10/12/2022] [Indexed: 11/04/2022] Open
Abstract
The 3D chromatin structure within the nucleus is important for gene expression regulation and correct developmental programs. Recently, the rapid development of low-input chromatin conformation capture technologies has made it possible to study 3D chromatin structures in gametes, zygotes and early embryos in a variety of species, including flies, vertebrates and mammals. There are distinct 3D chromatin structures within the male and female gametes. Following the fertilization of male and female gametes, fertilized eggs undergo drastic epigenetic reprogramming at multi levels, including the 3D chromatin structure, to convert the terminally differentiated gamete state into the totipotent state, which can give rise to an individual. However, to what extent the 3D chromatin structure reorganization is evolutionarily conserved and what the underlying mechanisms are for the tremendous reorganization in early embryos remain elusive. Here, we review the latest findings on the 3D chromatin structure reorganization during embryogenesis, and discuss the convergent and divergent reprogramming patterns and key molecular mechanisms for the 3D chromatin structure reorganization from gametes to embryos in different species. These findings shed light on how the 3D chromatin structure reorganization contribute to embryo development in different species. The findings also indicate the role of the 3D chromatin structure on the acquisition of totipotent developmental potential.
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34
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Chen H, Good MC. Nascent transcriptome reveals orchestration of zygotic genome activation in early embryogenesis. Curr Biol 2022; 32:4314-4324.e7. [PMID: 36007528 PMCID: PMC9560990 DOI: 10.1016/j.cub.2022.07.078] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/25/2022] [Accepted: 07/29/2022] [Indexed: 12/14/2022]
Abstract
Early embryo development requires maternal-to-zygotic transition, during which transcriptionally silent nuclei begin widespread gene expression during zygotic genome activation (ZGA).1-3 ZGA is vital for early cell fating and germ-layer specification,3,4 and ZGA timing is regulated by multiple mechanisms.1-5 However, controversies remain about whether these mechanisms are interrelated and vary among species6-10 and whether the timing of germ-layer-specific gene activation is temporally ordered.11,12 In some embryonic models, widespread ZGA onset is spatiotemporally graded,13,14 yet it is unclear whether the transcriptome follows this pattern. A major challenge in addressing these questions is to accurately measure the timing of each gene activation. Here, we metabolically label and identify the nascent transcriptome using 5-ethynyl uridine (5-EU) in Xenopus blastula embryos. We find that EU-RNA-seq outperforms total RNA-seq in detecting the ZGA transcriptome, which is dominated by transcription from maternal-zygotic genes, enabling improved ZGA timing determination. We uncover discrete spatiotemporal patterns for individual gene activation, a majority following a spatial pattern of ZGA that is correlated with a cell size gradient.14 We further reveal that transcription necessitates a period of developmental progression and that ZGA can be precociously induced by cycloheximide, potentially through elongation of interphase. Finally, most ectodermal genes are activated earlier than endodermal genes, suggesting a temporal orchestration of germ-layer-specific genes, potentially linked to the spatially graded pattern of ZGA. Together, our study provides fundamental new insights into the composition and dynamics of the ZGA transcriptome, mechanisms regulating ZGA timing, and its role in the onset of early cell fating.
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Affiliation(s)
- Hui Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Matthew C Good
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA.
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35
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Calderon D, Blecher-Gonen R, Huang X, Secchia S, Kentro J, Daza RM, Martin B, Dulja A, Schaub C, Trapnell C, Larschan E, O’Connor-Giles KM, Furlong EEM, Shendure J. The continuum of Drosophila embryonic development at single-cell resolution. Science 2022; 377:eabn5800. [PMID: 35926038 PMCID: PMC9371440 DOI: 10.1126/science.abn5800] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Drosophila melanogaster is a powerful, long-standing model for metazoan development and gene regulation. We profiled chromatin accessibility in almost 1 million and gene expression in half a million nuclei from overlapping windows spanning the entirety of embryogenesis. Leveraging developmental asynchronicity within embryo collections, we applied deep neural networks to infer the age of each nucleus, resulting in continuous, multimodal views of molecular and cellular transitions in absolute time. We identify cell lineages; infer their developmental relationships; and link dynamic changes in enhancer usage, transcription factor (TF) expression, and the accessibility of TFs' cognate motifs. With these data, the dynamics of enhancer usage and gene expression can be explored within and across lineages at the scale of minutes, including for precise transitions like zygotic genome activation.
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Affiliation(s)
- Diego Calderon
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Ronnie Blecher-Gonen
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
- The Crown Genomics Institute of the Nancy and Stephen Grand Israel National Center for Personalized Medicine, Weizmann Institute of Science, Rehovot, Israel
| | - Xingfan Huang
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
- Paul G. Allen School of Computer Science & Engineering, University of Washington, Seattle, WA 98195, USA
| | - Stefano Secchia
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - James Kentro
- Molecular Biology, Cell Biology, and Biochemistry Graduate Program, Brown University, Providence, RI 02912, USA
| | - Riza M. Daza
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Beth Martin
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Alessandro Dulja
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Christoph Schaub
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Cole Trapnell
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
- Brotman Baty Institute for Precision Medicine, University of Washington, Seattle, WA 98195, USA
- Allen Discovery Center for Cell Lineage Tracing, Seattle, WA 98195, USA
| | - Erica Larschan
- Molecular Biology, Cell Biology, and Biochemistry Graduate Program, Brown University, Providence, RI 02912, USA
| | - Kate M. O’Connor-Giles
- Department of Neuroscience and Carney Institute for Brain Science, Brown University, Providence, RI 02912, USA
| | - Eileen E. M. Furlong
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Jay Shendure
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
- Brotman Baty Institute for Precision Medicine, University of Washington, Seattle, WA 98195, USA
- Allen Discovery Center for Cell Lineage Tracing, Seattle, WA 98195, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
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36
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Merrill CB, Montgomery AB, Pabon MA, Shabalin AA, Rodan AR, Rothenfluh A. Harnessing changes in open chromatin determined by ATAC-seq to generate insulin-responsive reporter constructs. BMC Genomics 2022; 23:399. [PMID: 35614386 PMCID: PMC9134605 DOI: 10.1186/s12864-022-08637-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 05/12/2022] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Gene regulation is critical for proper cellular function. Next-generation sequencing technology has revealed the presence of regulatory networks that regulate gene expression and essential cellular functions. Studies investigating the epigenome have begun to uncover the complex mechanisms regulating transcription. Assay for transposase-accessible chromatin by sequencing (ATAC-seq) is quickly becoming the assay of choice for many epigenomic investigations. However, whether intervention-mediated changes in accessible chromatin determined by ATAC-seq can be harnessed to generate intervention-inducible reporter constructs has not been systematically assayed. RESULTS We used the insulin signaling pathway as a model to investigate chromatin regions and gene expression changes using ATAC- and RNA-seq in insulin-treated Drosophila S2 cells. We found correlations between ATAC- and RNA-seq data, especially when stratifying differentially-accessible chromatin regions by annotated feature type. In particular, our data demonstrated a weak but significant correlation between chromatin regions annotated to enhancers (1-2 kb from the transcription start site) and downstream gene expression. We cloned candidate enhancer regions upstream of luciferase and demonstrate insulin-inducibility of several of these reporters. CONCLUSIONS Insulin-induced chromatin accessibility determined by ATAC-seq reveals enhancer regions that drive insulin-inducible reporter gene expression.
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Affiliation(s)
- Collin B Merrill
- Department of Psychiatry, Huntsman Mental Health Institute, University of Utah, Salt Lake City, UT, 84108, USA.
| | - Austin B Montgomery
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, 84112, USA
| | - Miguel A Pabon
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, 84112, USA
| | - Andrey A Shabalin
- Department of Psychiatry, Huntsman Mental Health Institute, University of Utah, Salt Lake City, UT, 84108, USA
| | - Aylin R Rodan
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, 84112, USA
- Division of Nephrology, Department of Internal Medicine, University of Utah, Salt Lake City, UT, 84112, USA
- Department of Human Genetics, University of Utah, Salt Lake City, UT, 84112, USA
| | - Adrian Rothenfluh
- Department of Psychiatry, Huntsman Mental Health Institute, University of Utah, Salt Lake City, UT, 84108, USA.
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, 84112, USA.
- Department of Human Genetics, University of Utah, Salt Lake City, UT, 84112, USA.
- Department of Neurobiology, University of Utah, Salt Lake City, UT, 84112, USA.
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37
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Wang J, Zhang S, Lu H, Xu H. Differential regulation of alternative promoters emerges from unified kinetics of enhancer-promoter interaction. Nat Commun 2022; 13:2714. [PMID: 35581264 PMCID: PMC9114328 DOI: 10.1038/s41467-022-30315-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 04/25/2022] [Indexed: 11/25/2022] Open
Abstract
Many eukaryotic genes contain alternative promoters with distinct expression patterns. How these promoters are differentially regulated remains elusive. Here, we apply single-molecule imaging to quantify the transcriptional regulation of two alternative promoters (P1 and P2) of the Bicoid (Bcd) target gene hunchback in syncytial blastoderm Drosophila embryos. Contrary to the previous notion that Bcd only activates P2, we find that Bcd activates both promoters via the same two enhancers. P1 activation is less frequent and requires binding of more Bcd molecules than P2 activation. Using a theoretical model to relate promoter activity to enhancer states, we show that the two promoters follow common transcription kinetics driven by sequential Bcd binding at the two enhancers. Bcd binding at either enhancer primarily activates P2, while P1 activation relies more on Bcd binding at both enhancers. These results provide a quantitative framework for understanding the kinetic mechanisms of complex eukaryotic gene regulation. Alternative promoters differ in their expression patterns, whose mechanisms are not well understood. Here the authors show that alternative promoters of a Drosophila embryonic gene hunchback are regulated by different action modes of two enhancers.
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Affiliation(s)
- Jingyao Wang
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, China.,Institute of Natural Sciences, Shanghai Jiao Tong University, 200240, Shanghai, China
| | - Shihe Zhang
- Institute of Natural Sciences, Shanghai Jiao Tong University, 200240, Shanghai, China. .,School of Physics and Astronomy, Shanghai Jiao Tong University, 200240, Shanghai, China.
| | - Hongfang Lu
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, China.,Institute of Natural Sciences, Shanghai Jiao Tong University, 200240, Shanghai, China
| | - Heng Xu
- Institute of Natural Sciences, Shanghai Jiao Tong University, 200240, Shanghai, China. .,School of Physics and Astronomy, Shanghai Jiao Tong University, 200240, Shanghai, China.
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38
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Ranjan R, Snedeker J, Wooten M, Chu C, Bracero S, Mouton T, Chen X. Differential condensation of sister chromatids acts with Cdc6 to ensure asynchronous S-phase entry in Drosophila male germline stem cell lineage. Dev Cell 2022; 57:1102-1118.e7. [PMID: 35483360 PMCID: PMC9134767 DOI: 10.1016/j.devcel.2022.04.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 01/16/2022] [Accepted: 04/05/2022] [Indexed: 01/06/2023]
Abstract
During Drosophila melanogaster male germline stem cell (GSC) asymmetric division, preexisting old versus newly synthesized histones H3 and H4 are asymmetrically inherited. However, the biological outcomes of this phenomenon have remained unclear. Here, we tracked old and new histones throughout the GSC cell cycle through the use of high spatial and temporal resolution microscopy. We found unique features that differ between old and new histone-enriched sister chromatids, including differences in nucleosome density, chromosomal condensation, and H3 Ser10 phosphorylation. These distinct chromosomal features lead to their differential association with Cdc6, a pre-replication complex component, and subsequent asynchronous DNA replication initiation in the resulting daughter cells. Disruption of asymmetric histone inheritance abolishes differential Cdc6 association and asynchronous S-phase entry, demonstrating that histone asymmetry acts upstream of these critical cell-cycle progression events. Furthermore, disruption of these GSC-specific chromatin features leads to GSC defects, indicating a connection between histone inheritance, cell-cycle progression, and cell fate determination.
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Affiliation(s)
- Rajesh Ranjan
- Howard Hughes Medical Institute, Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA; Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
| | - Jonathan Snedeker
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Matthew Wooten
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Carolina Chu
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Sabrina Bracero
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Taylar Mouton
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Xin Chen
- Howard Hughes Medical Institute, Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA; Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
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39
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Bellec M, Dufourt J, Hunt G, Lenden-Hasse H, Trullo A, Zine El Aabidine A, Lamarque M, Gaskill MM, Faure-Gautron H, Mannervik M, Harrison MM, Andrau JC, Favard C, Radulescu O, Lagha M. The control of transcriptional memory by stable mitotic bookmarking. Nat Commun 2022; 13:1176. [PMID: 35246556 PMCID: PMC8897465 DOI: 10.1038/s41467-022-28855-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 02/15/2022] [Indexed: 01/23/2023] Open
Abstract
To maintain cellular identities during development, gene expression profiles must be faithfully propagated through cell generations. The reestablishment of gene expression patterns upon mitotic exit is mediated, in part, by transcription factors (TF) mitotic bookmarking. However, the mechanisms and functions of TF mitotic bookmarking during early embryogenesis remain poorly understood. In this study, taking advantage of the naturally synchronized mitoses of Drosophila early embryos, we provide evidence that GAGA pioneer factor (GAF) acts as a stable mitotic bookmarker during zygotic genome activation. We show that, during mitosis, GAF remains associated to a large fraction of its interphase targets, including at cis-regulatory sequences of key developmental genes with both active and repressive chromatin signatures. GAF mitotic targets are globally accessible during mitosis and are bookmarked via histone acetylation (H4K8ac). By monitoring the kinetics of transcriptional activation in living embryos, we report that GAF binding establishes competence for rapid activation upon mitotic exit.
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Affiliation(s)
- Maëlle Bellec
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - Jérémy Dufourt
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - George Hunt
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691, Stockholm, Sweden
| | - Hélène Lenden-Hasse
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - Antonio Trullo
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - Amal Zine El Aabidine
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - Marie Lamarque
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - Marissa M Gaskill
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Heloïse Faure-Gautron
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - Mattias Mannervik
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691, Stockholm, Sweden
| | - Melissa M Harrison
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Jean-Christophe Andrau
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - Cyril Favard
- Institut de Recherche en Infectiologie de Montpellier, CNRS UMR 9004, University of Montpellier, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France
| | - Ovidiu Radulescu
- LPHI, UMR CNRS 5235, University of Montpellier, Place E. Bataillon - Bât. 24 cc 107, Montpellier, 34095, Cedex 5, France
| | - Mounia Lagha
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS-UMR 5535, 1919 Route de Mende, Montpellier, 34293, Cedex 5, France.
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Miao L, Tang Y, Bonneau AR, Chan SH, Kojima ML, Pownall ME, Vejnar CE, Gao F, Krishnaswamy S, Hendry CE, Giraldez AJ. The landscape of pioneer factor activity reveals the mechanisms of chromatin reprogramming and genome activation. Mol Cell 2022; 82:986-1002.e9. [PMID: 35182480 PMCID: PMC9327391 DOI: 10.1016/j.molcel.2022.01.024] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 01/25/2022] [Accepted: 01/26/2022] [Indexed: 10/19/2022]
Abstract
Upon fertilization, embryos undergo chromatin reprogramming and genome activation; however, the mechanisms that regulate these processes are poorly understood. Here, we generated a triple mutant for Nanog, Pou5f3, and Sox19b (NPS) in zebrafish and found that NPS pioneer chromatin opening at >50% of active enhancers. NPS regulate acetylation across core histones at enhancers and promoters, and their function in gene activation can be bypassed by recruiting histone acetyltransferase to individual genes. NPS pioneer chromatin opening individually, redundantly, or additively depending on sequence context, and we show that high nucleosome occupancy facilitates NPS pioneering activity. Nucleosome position varies based on the input of different transcription factors (TFs), providing a flexible platform to modulate pioneering activity. Altogether, our results illuminate the sequence of events during genome activation and offer a conceptual framework to understand how pioneer factors interpret the genome and integrate different TF inputs across cell types and developmental transitions.
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Affiliation(s)
- Liyun Miao
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA.
| | - Yin Tang
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Ashley R Bonneau
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Shun Hang Chan
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Mina L Kojima
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Mark E Pownall
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Charles E Vejnar
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Feng Gao
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Smita Krishnaswamy
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA; Department of Computer Science, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Caroline E Hendry
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Antonio J Giraldez
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA; Yale Stem Cell Center, Yale University School of Medicine, New Haven, CT 06510, USA; Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06510, USA.
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41
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Emerging mechanisms and dynamics of three-dimensional genome organisation at zygotic genome activation. Curr Opin Cell Biol 2022; 74:37-46. [DOI: 10.1016/j.ceb.2021.12.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 12/10/2021] [Accepted: 12/13/2021] [Indexed: 02/07/2023]
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Prudêncio P, Savisaar R, Rebelo K, Martinho RG, Carmo-Fonseca M. Transcription and splicing dynamics during early Drosophila development. RNA (NEW YORK, N.Y.) 2022; 28:139-161. [PMID: 34667107 PMCID: PMC8906543 DOI: 10.1261/rna.078933.121] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 09/23/2021] [Indexed: 05/03/2023]
Abstract
Widespread cotranscriptional splicing has been demonstrated from yeast to human. However, most studies to date addressing the kinetics of splicing relative to transcription used either Saccharomyces cerevisiae or metazoan cultured cell lines. Here, we adapted native elongating transcript sequencing technology (NET-seq) to measure cotranscriptional splicing dynamics during the early developmental stages of Drosophila melanogaster embryos. Our results reveal the position of RNA polymerase II (Pol II) when both canonical and recursive splicing occur. We found heterogeneity in splicing dynamics, with some RNAs spliced immediately after intron transcription, whereas for other transcripts no splicing was observed over the first 100 nt of the downstream exon. Introns that show splicing completion before Pol II has reached the end of the downstream exon are necessarily intron-defined. We studied the splicing dynamics of both nascent pre-mRNAs transcribed in the early embryo, which have few and short introns, as well as pre-mRNAs transcribed later in embryonic development, which contain multiple long introns. As expected, we found a relationship between the proportion of spliced reads and intron size. However, intron definition was observed at all intron sizes. We further observed that genes transcribed in the early embryo tend to be isolated in the genome whereas genes transcribed later are often overlapped by a neighboring convergent gene. In isolated genes, transcription termination occurred soon after the polyadenylation site, while in overlapped genes, Pol II persisted associated with the DNA template after cleavage and polyadenylation of the nascent transcript. Taken together, our data unravel novel dynamic features of Pol II transcription and splicing in the developing Drosophila embryo.
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Affiliation(s)
- Pedro Prudêncio
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
- Algarve Biomedical Center Research Institute (ABC-RI), Universidade do Algarve, 8005-139 Faro, Portugal
| | - Rosina Savisaar
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Kenny Rebelo
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Rui Gonçalo Martinho
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
- Algarve Biomedical Center Research Institute (ABC-RI), Universidade do Algarve, 8005-139 Faro, Portugal
- Department of Medical Sciences and Institute for Biomedicine (iBiMED), Universidade de Aveiro, 3810-193 Aveiro, Portugal
| | - Maria Carmo-Fonseca
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
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43
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Liaw GJ. Polycomb repressive complex 1 initiates and maintains tailless repression in Drosophila embryo. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2022; 1865:194786. [PMID: 35032681 DOI: 10.1016/j.bbagrm.2022.194786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 12/29/2021] [Accepted: 01/05/2022] [Indexed: 06/14/2023]
Abstract
Maternally-deposited morphogens specify the fates of embryonic cells via hierarchically regulating the expression of zygotic genes that encode various classes of developmental regulators. Once the cell fates are determined, Polycomb-group proteins frequently maintain the repressed state of the genes. This study investigates how Polycomb-group proteins repress the expression of tailless, which encodes a developmental regulator in Drosophila embryo. Previous studies have shown that maternal Tramtrack69 facilitates maternal GAGA-binding factor and Heat shock factor binding to the torso response element (tor-RE) to initiate tailless repression in the stage-4 embryo. Chromatin-immunoprecipitation and genetic-interaction studies exhibit that maternally-deposited Polycomb repressive complex 1 (PRC1) recruited by the tor-RE-associated Tramtrack69 represses tailless expression in the stage-4 embryo. A noncanonical Polycomb-group response element (PRE) is mapped to the tailless proximal region. High levels of Bric-a-brac, Tramtrack, and Broad (BTB)-domain proteins are fundamental for maintaining tailless repression in the stage-8 to -10 embryos. Trmtrack69 sporadically distributes in the linear BTB-domain oligomer, which recruits and retains a high level of PRC1 near the GCCAT cluster for repressing tll expression in the stage-14 embryos. Disrupting the retention of PRC1 decreases the levels of PRC1 and Pleiohomeotic protein substantially on the PRE and causes tailless derepression in the stage-14 embryo. Furthermore, the retained PRC1 potentially serves as a second foundation for assembling the well-characterized polymer of the Sterile alpha motif domain in Polyhomeotic protein, which compacts chromatin to maintain the repressed state of tailless in the embryos after stage 14.
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Affiliation(s)
- Gwo-Jen Liaw
- Department of Life Sciences and Institute of Genomic Sciences, National Yang Ming Chiao Tung University, Yangming Campus, No. 155, Sec. 2, Linong St., Taipei 112, Taiwan.
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44
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Cornejo-Paramo P, Roper K, Degnan S, Degnan B, Wong ES. Distal regulation, silencers, and a shared combinatorial syntax are hallmarks of animal embryogenesis. Genome Res 2022; 32:474-487. [PMID: 35045977 PMCID: PMC8896464 DOI: 10.1101/gr.275864.121] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 01/12/2022] [Indexed: 11/25/2022]
Abstract
The chromatin environment plays a central role in regulating developmental gene expression in metazoans. Yet, the ancestral regulatory landscape of metazoan embryogenesis is unknown. Here, we generate chromatin accessibility profiles for six embryonic, plus larval and adult stages in the sponge Amphimedon queenslandica. These profiles are reproducible within stages, reflect histone modifications, and identify transcription factor (TF) binding sequence motifs predictive of cis-regulatory elements operating during embryogenesis in other metazoans, but not the unicellular relative Capsaspora. Motif analysis of chromatin accessibility profiles across Amphimedon embryogenesis identifies three major developmental periods. As in bilaterian embryogenesis, early development in Amphimedon involves activating and repressive chromatin in regions both proximal and distal to transcription start sites. Transcriptionally repressive elements (“silencers”) are prominent during late embryogenesis. They coincide with an increase in cis-regulatory regions harboring metazoan TF binding motifs, as well as an increase in the expression of metazoan-specific genes. Changes in chromatin state and gene expression in Amphimedon suggest the conservation of distal enhancers, dynamically silenced chromatin, and TF-DNA binding specificity in animal embryogenesis.
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45
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Larson ED, Komori H, Gibson TJ, Ostgaard CM, Hamm DC, Schnell JM, Lee CY, Harrison MM. Cell-type-specific chromatin occupancy by the pioneer factor Zelda drives key developmental transitions in Drosophila. Nat Commun 2021; 12:7153. [PMID: 34887421 PMCID: PMC8660810 DOI: 10.1038/s41467-021-27506-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 11/24/2021] [Indexed: 12/14/2022] Open
Abstract
During Drosophila embryogenesis, the essential pioneer factor Zelda defines hundreds of cis-regulatory regions and in doing so reprograms the zygotic transcriptome. While Zelda is essential later in development, it is unclear how the ability of Zelda to define cis-regulatory regions is shaped by cell-type-specific chromatin architecture. Asymmetric division of neural stem cells (neuroblasts) in the fly brain provide an excellent paradigm for investigating the cell-type-specific functions of this pioneer factor. We show that Zelda synergistically functions with Notch to maintain neuroblasts in an undifferentiated state. Zelda misexpression reprograms progenitor cells to neuroblasts, but this capacity is limited by transcriptional repressors critical for progenitor commitment. Zelda genomic occupancy in neuroblasts is reorganized as compared to the embryo, and this reorganization is correlated with differences in chromatin accessibility and cofactor availability. We propose that Zelda regulates essential transitions in the neuroblasts and embryo through a shared gene-regulatory network driven by cell-type-specific enhancers.
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Affiliation(s)
- Elizabeth D Larson
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Hideyuki Komori
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Tyler J Gibson
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Cyrina M Ostgaard
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Danielle C Hamm
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Jack M Schnell
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
- Department of Stem Cell and Regenerative Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Cheng-Yu Lee
- Division of Genetic Medicine, Department of Internal Medicine and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA.
| | - Melissa M Harrison
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
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46
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Conserved and species-specific chromatin remodeling and regulatory dynamics during mouse and chicken limb bud development. Nat Commun 2021; 12:5685. [PMID: 34584102 PMCID: PMC8479071 DOI: 10.1038/s41467-021-25935-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 09/07/2021] [Indexed: 12/13/2022] Open
Abstract
Chromatin remodeling and genomic alterations impact spatio-temporal regulation of gene expression, which is central to embryonic development. The analysis of mouse and chicken limb development provides important insights into the morphoregulatory mechanisms, however little is known about the regulatory differences underlying their morphological divergence. Here, we identify the underlying shared and species-specific epigenomic and genomic variations. In mouse forelimb buds, we observe striking synchrony between the temporal dynamics of chromatin accessibility and gene expression, while their divergence in chicken wing buds uncovers species-specific regulatory heterochrony. In silico mapping of transcription factor binding sites and computational footprinting establishes the developmental time-restricted transcription factor-DNA interactions. Finally, the construction of target gene networks for HAND2 and GLI3 transcriptional regulators reveals both conserved and species-specific interactions. Our analysis reveals the impact of genome evolution on the regulatory interactions orchestrating vertebrate limb bud morphogenesis and provides a molecular framework for comparative Evo-Devo studies. The vertebrate limb bud is a paradigm to uncover the fundamental mechanisms that govern embryogenesis and evolutionary diversification. Here the authors compare mouse and chicken limb bud development to study the impact of genome evolution on conserved and divergent gene regulatory interactions.
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Perutka Z, Kaduchová K, Chamrád I, Beinhauer J, Lenobel R, Petrovská B, Bergougnoux V, Vrána J, Pecinka A, Doležel J, Šebela M. Proteome Analysis of Condensed Barley Mitotic Chromosomes. FRONTIERS IN PLANT SCIENCE 2021; 12:723674. [PMID: 34497629 PMCID: PMC8419432 DOI: 10.3389/fpls.2021.723674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 07/21/2021] [Indexed: 06/13/2023]
Abstract
Proteins play a major role in the three-dimensional organization of nuclear genome and its function. While histones arrange DNA into a nucleosome fiber, other proteins contribute to higher-order chromatin structures in interphase nuclei, and mitotic/meiotic chromosomes. Despite the key role of proteins in maintaining genome integrity and transferring hereditary information to daughter cells and progenies, the knowledge about their function remains fragmentary. This is particularly true for the proteins of condensed chromosomes and, in particular, chromosomes of plants. Here, we purified barley mitotic metaphase chromosomes by a flow cytometric sorting and characterized their proteins. Peptides from tryptic protein digests were fractionated either on a cation exchanger or reversed-phase microgradient system before liquid chromatography coupled to tandem mass spectrometry. Chromosomal proteins comprising almost 900 identifications were classified based on a combination of software prediction, available database localization information, sequence homology, and domain representation. A biological context evaluation indicated the presence of several groups of abundant proteins including histones, topoisomerase 2, POLYMERASE 2, condensin subunits, and many proteins with chromatin-related functions. Proteins involved in processes related to DNA replication, transcription, and repair as well as nucleolar proteins were found. We have experimentally validated the presence of FIBRILLARIN 1, one of the nucleolar proteins, on metaphase chromosomes, suggesting that plant chromosomes are coated with proteins during mitosis, similar to those of human and animals. These results improve significantly the knowledge of plant chromosomal proteins and provide a basis for their functional characterization and comparative phylogenetic analyses.
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Affiliation(s)
- Zdeněk Perutka
- Department of Protein Biochemistry and Proteomics, Faculty of Science, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Olomouc, Czechia
| | - Kateřina Kaduchová
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Ivo Chamrád
- Department of Protein Biochemistry and Proteomics, Faculty of Science, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Olomouc, Czechia
| | - Jana Beinhauer
- Department of Protein Biochemistry and Proteomics, Faculty of Science, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Olomouc, Czechia
| | - René Lenobel
- Department of Protein Biochemistry and Proteomics, Faculty of Science, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Olomouc, Czechia
| | - Beáta Petrovská
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Véronique Bergougnoux
- Department of Molecular Biology, Faculty of Science, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Olomouc, Czechia
| | - Jan Vrána
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Ales Pecinka
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Jaroslav Doležel
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Marek Šebela
- Department of Protein Biochemistry and Proteomics, Faculty of Science, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Olomouc, Czechia
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48
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Duan J, Rieder L, Colonnetta MM, Huang A, Mckenney M, Watters S, Deshpande G, Jordan W, Fawzi N, Larschan E. CLAMP and Zelda function together to promote Drosophila zygotic genome activation. eLife 2021; 10:e69937. [PMID: 34342574 PMCID: PMC8367384 DOI: 10.7554/elife.69937] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/02/2021] [Indexed: 12/22/2022] Open
Abstract
During the essential and conserved process of zygotic genome activation (ZGA), chromatin accessibility must increase to promote transcription. Drosophila is a well-established model for defining mechanisms that drive ZGA. Zelda (ZLD) is a key pioneer transcription factor (TF) that promotes ZGA in the Drosophila embryo. However, many genomic loci that contain GA-rich motifs become accessible during ZGA independent of ZLD. Therefore, we hypothesized that other early TFs that function with ZLD have not yet been identified, especially those that are capable of binding to GA-rich motifs such as chromatin-linked adaptor for male-specific lethal (MSL) proteins (CLAMP). Here, we demonstrate that Drosophila embryonic development requires maternal CLAMP to (1) activate zygotic transcription; (2) increase chromatin accessibility at promoters of specific genes that often encode other essential TFs; and (3) enhance chromatin accessibility and facilitate ZLD occupancy at a subset of key embryonic promoters. Thus, CLAMP functions as a pioneer factor that plays a targeted yet essential role in ZGA.
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Affiliation(s)
- Jingyue Duan
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
| | - Leila Rieder
- Department of Biology, Emory UniversityAtlantaUnited States
| | - Megan M Colonnetta
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Annie Huang
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
| | - Mary Mckenney
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
| | - Scott Watters
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown UniversityProvidenceUnited States
| | - Girish Deshpande
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - William Jordan
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
| | - Nicolas Fawzi
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown UniversityProvidenceUnited States
| | - Erica Larschan
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
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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: 5] [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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Fan T, Huang Y. Accessible chromatin reveals regulatory mechanisms underlying cell fate decisions during early embryogenesis. Sci Rep 2021; 11:7896. [PMID: 33846424 PMCID: PMC8042068 DOI: 10.1038/s41598-021-86919-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 03/22/2021] [Indexed: 02/01/2023] Open
Abstract
This study was conducted to investigate epigenetic landscape across multiple species and identify transcription factors (TFs) and their roles in controlling cell fate decision events during early embryogenesis. We made a comprehensively joint-research of chromatin accessibility of five species during embryogenesis by integration of ATAC-seq and RNA-seq datasets. Regulatory roles of candidate early embryonic TFs were investigated. Widespread accessible chromatin in early embryos overlapped with putative cis-regulatory sequences. Sets of cell-fate-determining TFs were identified. YOX1, a key cell cycle regulator, were found to homologous to clusters of TFs that are involved in neuron and epidermal cell-fate determination. Our research provides an intriguing insight into evolution of cell-fate decision during early embryogenesis among organisms.
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Affiliation(s)
- Tongqiang Fan
- grid.443483.c0000 0000 9152 7385State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Hangzhou, 311300 People’s Republic of China
| | - Youjun Huang
- grid.443483.c0000 0000 9152 7385State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Hangzhou, 311300 People’s Republic of China
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