1
|
Aronson BE, Scourzic L, Shah V, Swanzey E, Kloetgen A, Polyzos A, Sinha A, Azziz A, Caspi I, Li J, Pelham-Webb B, Glenn RA, Vierbuchen T, Wichterle H, Tsirigos A, Dawlaty MM, Stadtfeld M, Apostolou E. A bipartite element with allele-specific functions safeguards DNA methylation imprints at the Dlk1-Dio3 locus. Dev Cell 2021; 56:3052-3065.e5. [PMID: 34710357 PMCID: PMC8628258 DOI: 10.1016/j.devcel.2021.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 08/06/2021] [Accepted: 10/04/2021] [Indexed: 11/23/2022]
Abstract
Loss of imprinting (LOI) results in severe developmental defects, but the mechanisms preventing LOI remain incompletely understood. Here, we dissect the functional components of the imprinting control region of the essential Dlk1-Dio3 locus (called IG-DMR) in pluripotent stem cells. We demonstrate that the IG-DMR consists of two antagonistic elements: a paternally methylated CpG island that prevents recruitment of TET dioxygenases and a maternally unmethylated non-canonical enhancer that ensures expression of the Gtl2 lncRNA by counteracting de novo DNA methyltransferases. Genetic or epigenetic editing of these elements leads to distinct LOI phenotypes with characteristic alternations of allele-specific gene expression, DNA methylation, and 3D chromatin topology. Although repression of the Gtl2 promoter results in dysregulated imprinting, the stability of LOI phenotypes depends on the IG-DMR, suggesting a functional hierarchy. These findings establish the IG-DMR as a bipartite control element that maintains imprinting by allele-specific restriction of the DNA (de)methylation machinery.
Collapse
Affiliation(s)
- Boaz E Aronson
- Sanford I Weill Department of Medicine, Division of Hematology/Oncology, Sandra and Edward Meyer Cancer Center, New York, NY 10021, USA
| | - Laurianne Scourzic
- Sanford I Weill Department of Medicine, Division of Hematology/Oncology, Sandra and Edward Meyer Cancer Center, New York, NY 10021, USA
| | - Veevek Shah
- Sanford I Weill Department of Medicine, Division of Hematology/Oncology, Sandra and Edward Meyer Cancer Center, New York, NY 10021, USA
| | - Emily Swanzey
- Sanford I Weill Department of Medicine, Division of Regenerative Medicine, Weill Cornell Medicine, New York, NY 10021, USA; The Jackson Laboratory, Bar Harbor, ME, USA
| | - Andreas Kloetgen
- Department of Pathology, New York University School of Medicine, New York, NY 10016, USA; Department of Computational Biology of Infection Research, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Alexander Polyzos
- Sanford I Weill Department of Medicine, Division of Hematology/Oncology, Sandra and Edward Meyer Cancer Center, New York, NY 10021, USA
| | - Abhishek Sinha
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Annabel Azziz
- Weill Cornell Graduate School of Medical Sciences, Weill Cornell Medicine, New York, NY 10065, USA
| | - Inbal Caspi
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Jiexi Li
- Sanford I Weill Department of Medicine, Division of Hematology/Oncology, Sandra and Edward Meyer Cancer Center, New York, NY 10021, USA
| | - Bobbie Pelham-Webb
- Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD program, New York, NY, USA
| | - Rachel A Glenn
- Weill Cornell Graduate School of Medical Sciences, Weill Cornell Medicine, New York, NY 10065, USA; Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Center for Stem Cell Biology and Center for Epigenetics Research, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Thomas Vierbuchen
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Center for Stem Cell Biology and Center for Epigenetics Research, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Hynek Wichterle
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Neurology, Neuroscience and Rehabilitation and Regenerative Medicine, Columbia University Irving Medical Center, Center for Motor Neuron Biology and Disease and Columbia Stem Cell Initiative, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Aristotelis Tsirigos
- Department of Pathology, New York University School of Medicine, New York, NY 10016, USA; Institute for Computational Medicine and Applied Bioinformatics Laboratories, New York University School of Medicine, New York, NY 10016, USA
| | - Meelad M Dawlaty
- Ruth L and David S. Gottesman Institute for Stem Cell and Regenerative Medicine Research, Bronx, NY 10461, USA; Department of Genetics, Department of Developmental & Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Matthias Stadtfeld
- Sanford I Weill Department of Medicine, Division of Regenerative Medicine, Weill Cornell Medicine, New York, NY 10021, USA.
| | - Effie Apostolou
- Sanford I Weill Department of Medicine, Division of Hematology/Oncology, Sandra and Edward Meyer Cancer Center, New York, NY 10021, USA.
| |
Collapse
|
2
|
Pelham-Webb B, Polyzos A, Wojenski L, Kloetgen A, Li J, Di Giammartino DC, Sakellaropoulos T, Tsirigos A, Core L, Apostolou E. H3K27ac bookmarking promotes rapid post-mitotic activation of the pluripotent stem cell program without impacting 3D chromatin reorganization. Mol Cell 2021; 81:1732-1748.e8. [PMID: 33730542 PMCID: PMC8052294 DOI: 10.1016/j.molcel.2021.02.032] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 01/15/2021] [Accepted: 02/22/2021] [Indexed: 01/19/2023]
Abstract
During self-renewal, cell-type-defining features are drastically perturbed in mitosis and must be faithfully reestablished upon G1 entry, a process that remains largely elusive. Here, we characterized at a genome-wide scale the dynamic transcriptional and architectural resetting of mouse pluripotent stem cells (PSCs) upon mitotic exit. We captured distinct waves of transcriptional reactivation with rapid induction of stem cell genes and transient activation of lineage-specific genes. Topological reorganization at different hierarchical levels also occurred in an asynchronous manner and showed partial coordination with transcriptional resetting. Globally, rapid transcriptional and architectural resetting associated with mitotic retention of H3K27 acetylation, supporting a bookmarking function. Indeed, mitotic depletion of H3K27ac impaired the early reactivation of bookmarked, stem-cell-associated genes. However, 3D chromatin reorganization remained largely unaffected, suggesting that these processes are driven by distinct forces upon mitotic exit. This study uncovers principles and mediators of PSC molecular resetting during self-renewal.
Collapse
Affiliation(s)
- Bobbie Pelham-Webb
- Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA; Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD program, New York, NY 10021, USA
| | - Alexander Polyzos
- Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA.
| | - Luke Wojenski
- Department of Molecular and Cellular Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Andreas Kloetgen
- Department of Pathology, NYU School of Medicine, New York, NY 10016, USA; Department of Computational Biology of Infection Research, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Jiexi Li
- Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | - Dafne Campigli Di Giammartino
- Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | | | - Aristotelis Tsirigos
- Department of Pathology, NYU School of Medicine, New York, NY 10016, USA; Laura and Isaac Perlmutter Cancer Center and Helen L. and Martin S. Kimmel Center for Stem Cell Biology, NYU School of Medicine, New York, NY 10016, USA; Applied Bioinformatics Laboratories, NYU School of Medicine, New York, NY 10016, USA
| | - Leighton Core
- Department of Molecular and Cellular Biology, University of Connecticut, Storrs, CT 06269, USA; Institute for Systems Genomics, University of Connecticut, Storrs, CT 06269, USA
| | - Effie Apostolou
- Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA.
| |
Collapse
|
3
|
Pelham-Webb B, Murphy D, Apostolou E. Dynamic 3D Chromatin Reorganization during Establishment and Maintenance of Pluripotency. Stem Cell Reports 2020; 15:1176-1195. [PMID: 33242398 PMCID: PMC7724465 DOI: 10.1016/j.stemcr.2020.10.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 10/25/2020] [Accepted: 10/27/2020] [Indexed: 12/12/2022] Open
Abstract
Higher-order chromatin structure is tightly linked to gene expression and therefore cell identity. In recent years, the chromatin landscape of pluripotent stem cells has become better characterized, and unique features at various architectural levels have been revealed. However, the mechanisms that govern establishment and maintenance of these topological characteristics and the temporal and functional relationships with transcriptional or epigenetic features are still areas of intense study. Here, we will discuss progress and limitations of our current understanding regarding how the 3D chromatin topology of pluripotent stem cells is established during somatic cell reprogramming and maintained during cell division. We will also discuss evidence and theories about the driving forces of topological reorganization and the functional links with key features and properties of pluripotent stem cell identity.
Collapse
Affiliation(s)
- Bobbie Pelham-Webb
- Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA; Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY 10021, USA
| | - Dylan Murphy
- Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | - Effie Apostolou
- Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA.
| |
Collapse
|
4
|
Liu Y, Pelham-Webb B, Di Giammartino DC, Li J, Kim D, Kita K, Saiz N, Garg V, Doane A, Giannakakou P, Hadjantonakis AK, Elemento O, Apostolou E. Widespread Mitotic Bookmarking by Histone Marks and Transcription Factors in Pluripotent Stem Cells. Cell Rep 2018; 19:1283-1293. [PMID: 28514649 DOI: 10.1016/j.celrep.2017.04.067] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 03/17/2017] [Accepted: 04/24/2017] [Indexed: 10/19/2022] Open
Abstract
During mitosis, transcription is halted and many chromatin features are lost, posing a challenge for the continuity of cell identity, particularly in fast cycling stem cells, which constantly balance self-renewal with differentiation. Here we show that, in pluripotent stem cells, certain histone marks and stem cell regulators remain associated with specific genomic regions of mitotic chromatin, a phenomenon known as mitotic bookmarking. Enhancers of stem cell-related genes are bookmarked by both H3K27ac and the master regulators OCT4, SOX2, and KLF4, while promoters of housekeeping genes retain high levels of mitotic H3K27ac in a cell-type invariant manner. Temporal degradation of OCT4 during mitotic exit compromises its ability both to maintain and induce pluripotency, suggesting that its regulatory function partly depends on its bookmarking activity. Together, our data document a widespread yet specific bookmarking by histone modifications and transcription factors promoting faithful and efficient propagation of stemness after cell division.
Collapse
Affiliation(s)
- Yiyuan Liu
- Joan & Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | - Bobbie Pelham-Webb
- Joan & Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA; Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY 10021, USA
| | - Dafne Campigli Di Giammartino
- Joan & Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | - Jiexi Li
- Joan & Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | - Daleum Kim
- Joan & Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | - Katsuhiro Kita
- Joan & Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | - Nestor Saiz
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Vidur Garg
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Ashley Doane
- Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - Paraskevi Giannakakou
- Joan & Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA
| | - Anna-Katerina Hadjantonakis
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Olivier Elemento
- Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - Effie Apostolou
- Joan & Sanford I. Weill Department of Medicine, Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10021, USA.
| |
Collapse
|
5
|
Verma N, Pan H, Doré LC, Shukla A, Li QV, Pelham-Webb B, Teijeiro V, González F, Krivtsov A, Chang CJ, Papapetrou EP, He C, Elemento O, Huangfu D. Publisher Correction: TET proteins safeguard bivalent promoters from de novo methylation in human embryonic stem cells. Nat Genet 2017; 50:764. [PMID: 29255266 DOI: 10.1038/s41588-017-0024-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The version of the Supplementary Text and Figures file initially posted was missing Supplementary Tables 1-6 and the Supplementary Note and used incorrect versions of the supplementary figures.
Collapse
Affiliation(s)
- Nipun Verma
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.,Weill Graduate School of Medical Sciences at Cornell University/The Rockefeller University/Sloan Kettering Institute Tri-Institutional MD-PhD Program, New York, NY, USA
| | - Heng Pan
- Department of Physiology and Biophysics, Englander Institute for Precision Medicine, Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY, USA.,Weill Cornell Graduate School of Medical Sciences, Weill Cornell Medical College, New York, NY, USA
| | - Louis C Doré
- Department of Chemistry, Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, Howard Hughes Medical Institute, University of Chicago, Chicago, IL, USA
| | - Abhijit Shukla
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Qing V Li
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.,Louis V. Gerstner Jr. Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Bobbie Pelham-Webb
- Weill Graduate School of Medical Sciences at Cornell University/The Rockefeller University/Sloan Kettering Institute Tri-Institutional MD-PhD Program, New York, NY, USA
| | - Virginia Teijeiro
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.,Weill Cornell Graduate School of Medical Sciences, Weill Cornell Medical College, New York, NY, USA
| | - Federico González
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.,Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain
| | - Andrei Krivtsov
- Cancer Biology and Genetics Program, Sloan Kettering Institute, New York, NY, USA
| | - Chan-Jung Chang
- Department of Oncological Sciences and Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Eirini P Papapetrou
- Department of Oncological Sciences and Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Chuan He
- Department of Chemistry, Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, Howard Hughes Medical Institute, University of Chicago, Chicago, IL, USA
| | - Olivier Elemento
- Department of Physiology and Biophysics, Englander Institute for Precision Medicine, Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY, USA.
| | - Danwei Huangfu
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.
| |
Collapse
|
6
|
Verma N, Pan H, Doré LC, Shukla A, Li QV, Pelham-Webb B, Teijeiro V, González F, Krivtsov A, Chang CJ, Papapetrou EP, He C, Elemento O, Huangfu D. TET proteins safeguard bivalent promoters from de novo methylation in human embryonic stem cells. Nat Genet 2017; 50:83-95. [PMID: 29203910 PMCID: PMC5742051 DOI: 10.1038/s41588-017-0002-y] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 10/25/2017] [Indexed: 12/22/2022]
Abstract
The TET enzymes oxidize 5-methylcytosine to 5-hydroxymethylcytosine, which can lead to DNA demethylation. However, direct connections between TET-mediated DNA demethylation and transcriptional output are difficult to establish due to challenges of distinguishing global versus locus-specific effects. Here we show that TET1/2/3 triple knockout (TKO) human embryonic stem cells (hESCs) exhibit prominent bivalent promoter hypermethylation without an overall corresponding gene expression decrease in the undifferentiated state. Focusing on the bivalent PAX6 locus, we find increased DNMT3B binding is associated with promoter hypermethylation, which precipitates a neural differentiation defect and failure of PAX6 induction during differentiation. dCas9-mediated locus-specific demethylation and global inactivation of DNMT3B in TKO hESCs partially reverses the hypermethylation at the PAX6 promoter and improves differentiation to neuroectoderm. Taken together with further genome-wide methylation and TET1 and DNMT3B ChIP-Seq analysis, we conclude that the TET proteins safeguard bivalent promoters from de novo methylation to ensure robust lineage-specific transcription upon differentiation.
Collapse
Affiliation(s)
- Nipun Verma
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.,Weill Graduate School of Medical Sciences at Cornell University/The Rockefeller University/Sloan Kettering Institute Tri-Institutional MD-PhD Program, New York, NY, USA
| | - Heng Pan
- Department of Physiology and Biophysics, Englander Institute for Precision Medicine, Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY, USA.,Weill Cornell Graduate School of Medical Sciences, Weill Cornell Medical College, New York, NY, USA
| | - Louis C Doré
- Department of Chemistry, Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, Howard Hughes Medical Institute, University of Chicago, Chicago, IL, USA
| | - Abhijit Shukla
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Qing V Li
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.,Louis V. Gerstner Jr. Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Bobbie Pelham-Webb
- Weill Graduate School of Medical Sciences at Cornell University/The Rockefeller University/Sloan Kettering Institute Tri-Institutional MD-PhD Program, New York, NY, USA
| | - Virginia Teijeiro
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.,Weill Cornell Graduate School of Medical Sciences, Weill Cornell Medical College, New York, NY, USA
| | - Federico González
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.,Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain
| | - Andrei Krivtsov
- Cancer Biology and Genetics Program, Sloan Kettering Institute, New York, NY, USA
| | - Chan-Jung Chang
- Department of Oncological Sciences and Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Eirini P Papapetrou
- Department of Oncological Sciences and Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Chuan He
- Department of Chemistry, Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, Howard Hughes Medical Institute, University of Chicago, Chicago, IL, USA
| | - Olivier Elemento
- Department of Physiology and Biophysics, Englander Institute for Precision Medicine, Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY, USA.
| | - Danwei Huangfu
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.
| |
Collapse
|
7
|
Falahati H, Pelham-Webb B, Blythe S, Wieschaus E. Nucleation by rRNA Dictates the Precision of Nucleolus Assembly. Curr Biol 2016; 26:277-85. [PMID: 26776729 DOI: 10.1016/j.cub.2015.11.065] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 10/27/2015] [Accepted: 11/25/2015] [Indexed: 02/05/2023]
Abstract
Membrane-less organelles are intracellular compartments specialized to carry out specific cellular functions. There is growing evidence supporting the possibility that such organelles form as a new phase, separating from cytoplasm or nucleoplasm. However, a main challenge to such phase separation models is that the initial assembly, or nucleation, of the new phase is typically a highly stochastic process and does not allow for the spatiotemporal precision observed in biological systems. Here, we investigate the initial assembly of the nucleolus, a membrane-less organelle involved in different cellular functions including ribosomal biogenesis. We demonstrate that the nucleolus formation is precisely timed in D. melanogaster embryos and follows the transcription of rRNA. We provide evidence that transcription of rRNA is necessary for overcoming the highly stochastic nucleation step in the formation of the nucleolus, through a seeding mechanism. In the absence of rDNA, the nucleolar proteins studied are able to form high-concentration assemblies. However, unlike the nucleolus, these assemblies are highly variable in number, location, and time at which they form. In addition, quantitative study of the changes in the nucleoplasmic concentration and distribution of these nucleolar proteins in the wild-type embryos is consistent with the role of rRNA in seeding the nucleolus formation.
Collapse
Affiliation(s)
- Hanieh Falahati
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Bobbie Pelham-Webb
- Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY 10065, USA
| | - Shelby Blythe
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA
| | - Eric Wieschaus
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA.
| |
Collapse
|