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Abstract
Correlation between nuclear and cell size, the nucleocytoplasmic ratio, is a cellular phenomenon that has been reported throughout eukaryotes for more than a century but the mechanisms that achieve it are not well understood. Here, we review work that has shed light on the cellular processes involved in nuclear size control. These studies have implicated nucleocytoplasmic transport, LINC complexes, RNA processing, regulation of nuclear envelope expansion and partitioning of importin α in nuclear size control, moving us closer to a mechanistic understanding of this phenomenon.
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52
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Ren H, Xin G, Jia M, Zhu S, Lin Q, Wang X, Jiang Q, Zhang C. Postmitotic annulate lamellae assembly contributes to nuclear envelope reconstitution in daughter cells. J Biol Chem 2019; 294:10383-10391. [PMID: 31152066 DOI: 10.1074/jbc.ac119.008171] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 05/22/2019] [Indexed: 11/06/2022] Open
Abstract
In higher eukaryotic cells, the nuclear envelope (NE) is composed of double nuclear membranes studded with nuclear pore complexes (NPCs) and undergoes dynamic disassembly and reassembly during the cell cycle. However, how the NE and NPC reassemble remains largely unclear. Here, using HeLa, HEK293, and Drosophila cells, along with immunofluorescence microscopy and transmission EM methods, we found that postmitotic annulate lamellae (AL) assembly contributes to NE and NPC assembly. We observed that the AL are parallel membrane-pair stacks and possess regularly spaced AL pore complexes (ALPCs) that are morphologically similar to the NPCs. We found that the AL assemble in the cytoplasm during mitotic exit simultaneously with NE re-formation in daughter cells. Then, the assembled AL either bound the decondensing chromatin to directly transform into the NE or bound and fused with the outer nuclear membrane to join the assembling NE. The AL did not colocalize with sheet and tubular endoplasmic reticulum (ER) marker proteins on the ER or the lamin B receptor-localized membrane in the cytoplasm, suggesting that postmitotic AL assembly occurs independently of the chromatin and ER. Collectively, our results indicate that postmitotic AL assembly is a common cellular event and an intermediate step in NE and NPC assembly and in NE expansion in higher eukaryotic cells.
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Affiliation(s)
- He Ren
- From the Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Guangwei Xin
- From the Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Mingkang Jia
- From the Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Shicong Zhu
- From the Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Qiaoyu Lin
- From the Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Xiangyang Wang
- From the Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Qing Jiang
- From the Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Chuanmao Zhang
- From the Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
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53
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Jevtić P, Schibler AC, Wesley CC, Pegoraro G, Misteli T, Levy DL. The nucleoporin ELYS regulates nuclear size by controlling NPC number and nuclear import capacity. EMBO Rep 2019; 20:embr.201847283. [PMID: 31085625 DOI: 10.15252/embr.201847283] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 04/09/2019] [Accepted: 04/11/2019] [Indexed: 12/13/2022] Open
Abstract
How intracellular organelles acquire their characteristic sizes is a fundamental question in cell biology. Given stereotypical changes in nuclear size in cancer, it is important to understand the mechanisms that control nuclear size in human cells. Using a high-throughput imaging RNAi screen, we identify and mechanistically characterize ELYS, a nucleoporin required for post-mitotic nuclear pore complex (NPC) assembly, as a determinant of nuclear size in mammalian cells. ELYS knockdown results in small nuclei, reduced nuclear lamin B2 localization, lower NPC density, and decreased nuclear import. Increasing nuclear import by importin α overexpression rescues nuclear size and lamin B2 import, while inhibiting importin α/β-mediated nuclear import decreases nuclear size. Conversely, ELYS overexpression increases nuclear size, enriches nuclear lamin B2 at the nuclear periphery, and elevates NPC density and nuclear import. Consistent with these observations, knockdown or inhibition of exportin 1 increases nuclear size. Thus, we identify ELYS as a novel positive effector of mammalian nuclear size and propose that nuclear size is sensitive to NPC density and nuclear import capacity.
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Affiliation(s)
- Predrag Jevtić
- Department of Molecular Biology, University of Wyoming, Laramie, WY, USA
| | | | - Chase C Wesley
- Department of Molecular Biology, University of Wyoming, Laramie, WY, USA
| | - Gianluca Pegoraro
- High Throughput Imaging Facility (HiTIF), National Cancer Institute, NIH, Bethesda, MD, USA
| | - Tom Misteli
- National Cancer Institute, NIH, Bethesda, MD, USA
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY, USA
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54
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Jevtić P, Mukherjee RN, Chen P, Levy DL. Altering the levels of nuclear import factors in early Xenopus laevis embryos affects later development. PLoS One 2019; 14:e0215740. [PMID: 31009515 PMCID: PMC6476522 DOI: 10.1371/journal.pone.0215740] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 04/08/2019] [Indexed: 11/19/2022] Open
Abstract
More than just a container for DNA, the nuclear envelope carries out a wide variety of critical and highly regulated cellular functions. One of these functions is nuclear import, and in this study we investigate how altering the levels of nuclear transport factors impacts developmental progression and organismal size. During early Xenopus laevis embryogenesis, the timing of a key developmental event, the midblastula transition (MBT), is sensitive to nuclear import factor levels. How might altering nuclear import factors and MBT timing in the early embryo affect downstream development of the organism? We microinjected X. laevis two-cell embryos with mRNA to increase levels of importin α or NTF2, resulting in differential amounts of nuclear import factors in the two halves of the embryo. Compared to controls, these embryos exhibited delayed gastrulation, curved neural plates, and bent tadpoles with different sized eyes. Furthermore, embryos microinjected with NTF2 developed into smaller froglets compared to control microinjected embryos. We propose that altering nuclear import factors and nuclear size affects MBT timing, cell size, and cell number, subsequently disrupting later development. Thus, altering nuclear import factors early in development can affect function and size at the organismal level.
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Affiliation(s)
- Predrag Jevtić
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, United States of America
| | - Richik N. Mukherjee
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, United States of America
| | - Pan Chen
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, United States of America
| | - Daniel L. Levy
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, United States of America
- * E-mail:
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55
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Shindo Y, Amodeo AA. Dynamics of Free and Chromatin-Bound Histone H3 during Early Embryogenesis. Curr Biol 2019; 29:359-366.e4. [DOI: 10.1016/j.cub.2018.12.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/29/2018] [Accepted: 12/13/2018] [Indexed: 11/27/2022]
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56
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Dilsaver MR, Chen P, Thompson TA, Reusser T, Mukherjee RN, Oakey J, Levy DL. Emerin induces nuclear breakage in Xenopus extract and early embryos. Mol Biol Cell 2018; 29:3155-3167. [PMID: 30332321 PMCID: PMC6340207 DOI: 10.1091/mbc.e18-05-0277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Emerin is an inner nuclear membrane protein often mutated in Emery–Dreifuss muscular dystrophy. Because emerin has diverse roles in nuclear mechanics, cytoskeletal organization, and gene expression, it has been difficult to elucidate its contribution to nuclear structure and disease pathology. In this study, we investigated emerin’s impact on nuclei assembled in Xenopus laevis egg extract, a simplified biochemical system that lacks potentially confounding cellular factors and activities. Notably, these extracts are transcriptionally inert and lack endogenous emerin and filamentous actin. Strikingly, emerin caused rupture of egg extract nuclei, dependent on the application of shear force. In egg extract, emerin localized to nonnuclear cytoplasmic membranes, and nuclear rupture was rescued by targeting emerin to the nucleus, disrupting its membrane association, or assembling nuclei with lamin A. Furthermore, emerin induced breakage of nuclei in early-stage X. laevis embryo extracts, and embryos microinjected with emerin were inviable, with ruptured nuclei. We propose that cytoplasmic membrane localization of emerin leads to rupture of nuclei that are more sensitive to mechanical perturbation, findings that may be relevant to early development and certain laminopathies.
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Affiliation(s)
- Matthew R Dilsaver
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - Pan Chen
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - Trey A Thompson
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - Traci Reusser
- Department of Chemical Engineering, University of Wyoming, Laramie, WY 82071
| | - Richik N Mukherjee
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - John Oakey
- Department of Chemical Engineering, University of Wyoming, Laramie, WY 82071
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
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57
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Reisser M, Palmer A, Popp AP, Jahn C, Weidinger G, Gebhardt JCM. Single-molecule imaging correlates decreasing nuclear volume with increasing TF-chromatin associations during zebrafish development. Nat Commun 2018; 9:5218. [PMID: 30523256 PMCID: PMC6283880 DOI: 10.1038/s41467-018-07731-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 11/21/2018] [Indexed: 11/08/2022] Open
Abstract
Zygotic genome activation (ZGA), the onset of transcription after initial quiescence, is a major developmental step in many species, which occurs after ten cell divisions in zebrafish embryos. How transcription factor (TF)-chromatin interactions evolve during early development to support ZGA is largely unknown. We establish single molecule tracking in live developing zebrafish embryos using reflected light-sheet microscopy to visualize two fluorescently labeled TF species, mEos2-TBP and mEos2-Sox19b. We further develop a data acquisition and analysis scheme to extract quantitative information on binding kinetics and bound fractions during fast cell cycles. The chromatin-bound fraction of both TFs increases during early development, as expected from a physical model of TF-chromatin interactions including a decreasing nuclear volume and increasing DNA accessibility. For Sox19b, data suggests the increase is mainly due to the shrinking nucleus. Our single molecule approach provides quantitative insight into changes of TF-chromatin associations during the developmental period embracing ZGA.
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Affiliation(s)
- Matthias Reisser
- Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Anja Palmer
- Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Achim P Popp
- Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Christopher Jahn
- Institute of Biochemistry and Molecular Biology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Gilbert Weidinger
- Institute of Biochemistry and Molecular Biology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - J Christof M Gebhardt
- Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
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58
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Desnitskiy AG. Cell cycles during early steps of amphibian embryogenesis: A review. Biosystems 2018; 173:100-103. [DOI: 10.1016/j.biosystems.2018.09.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/14/2018] [Accepted: 09/17/2018] [Indexed: 11/24/2022]
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59
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Walters AD, Amoateng K, Wang R, Chen JH, McDermott G, Larabell CA, Gadal O, Cohen-Fix O. Nuclear envelope expansion in budding yeast is independent of cell growth and does not determine nuclear volume. Mol Biol Cell 2018; 30:131-145. [PMID: 30379612 PMCID: PMC6337908 DOI: 10.1091/mbc.e18-04-0204] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Most cells exhibit a constant ratio between nuclear and cell volume. The mechanism dictating this constant ratio and the nuclear component(s) that scale with cell size are not known. To address this, we examined the consequences to the size and shape of the budding yeast nucleus when cell expansion is inhibited by down-regulating components of the secretory pathway. We find that under conditions where cell size increase is restrained, the nucleus becomes bilobed, with the bulk of the DNA in one lobe and the nucleolus in the other. The formation of bilobed nuclei is dependent on fatty acid and phospholipid synthesis, suggesting that it is associated with nuclear membrane expansion. Bilobed nuclei appeared predominantly after spindle pole body separation, suggesting that nuclear envelope expansion follows cell-cycle cues rather than cell size. Importantly, cells with bilobed nuclei had the same nuclear:cell volume ratio as cells with round nuclei. Therefore, the bilobed nucleus could be a consequence of continued NE expansion as cells traverse the cell cycle without an accompanying increase in nuclear volume due to the inhibition of cell growth. Our data suggest that nuclear volume is not determined by nuclear envelope availability but by one or more nucleoplasmic factors.
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Affiliation(s)
- Alison D Walters
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Kwabena Amoateng
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Renjie Wang
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 31000 Toulouse, France
| | - Jian-Hua Chen
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94158.,Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Gerry McDermott
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94158.,Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Carolyn A Larabell
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94158.,Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Olivier Gadal
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 31000 Toulouse, France
| | - Orna Cohen-Fix
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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60
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Arbach HE, Harland-Dunaway M, Chang JK, Wills AE. Extreme nuclear branching in healthy epidermal cells of the Xenopus tail fin. J Cell Sci 2018; 131:jcs.217513. [PMID: 30131443 DOI: 10.1242/jcs.217513] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 08/10/2018] [Indexed: 01/09/2023] Open
Abstract
Changes in nuclear morphology contribute to the regulation of complex cell properties, including differentiation and tissue elasticity. Perturbations of nuclear morphology are associated with pathologies that include progeria, cancer and muscular dystrophy. The mechanisms governing nuclear shape changes in healthy cells remain poorly understood, partially because there are few models of nuclear shape variation in healthy cells. Here, we introduce nuclear branching in epidermal fin cells of Xenopus tropicalis as a model for extreme variation of nuclear morphology in a diverse population of healthy cells. We found that nuclear branching arises within these cells and becomes more elaborate during embryonic development. These cells contain broadly distributed marks of transcriptionally active chromatin and heterochromatin, and have active cell cycles. We found that nuclear branches are disrupted by loss of filamentous actin and depend on epidermal expression of the nuclear lamina protein Lamin B1. Inhibition of nuclear branching disrupts fin morphology, suggesting that nuclear branching may be involved in fin development. This study introduces the nuclei of the Xenopus fin as a powerful new model for extreme nuclear morphology in healthy cells to complement studies of nuclear shape variation in pathological contexts.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Hannah E Arbach
- Department of Biochemistry, University of Washington, Seattle, WA 98195-3750, USA
| | | | - Jessica K Chang
- Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Andrea E Wills
- Department of Biochemistry, University of Washington, Seattle, WA 98195-3750, USA
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61
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Heald R, Gibeaux R. Subcellular scaling: does size matter for cell division? Curr Opin Cell Biol 2018; 52:88-95. [PMID: 29501026 PMCID: PMC5988940 DOI: 10.1016/j.ceb.2018.02.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 02/05/2018] [Accepted: 02/13/2018] [Indexed: 12/14/2022]
Abstract
Among different species or cell types, or during early embryonic cell divisions that occur in the absence of cell growth, the size of subcellular structures, including the nucleus, chromosomes, and mitotic spindle, scale with cell size. Maintaining correct subcellular scales is thought to be important for many cellular processes and, in particular, for mitosis. In this review, we provide an update on nuclear and chromosome scaling mechanisms and their significance in metazoans, with a focus on Caenorhabditis elegans, Xenopus and mammalian systems, for which a common role for the Ran (Ras-related nuclear protein)-dependent nuclear transport system has emerged.
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Affiliation(s)
- Rebecca Heald
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
| | - Romain Gibeaux
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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62
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Milunovic-Jevtic A, Jevtic P, Levy DL, Gatlin JC. In vivo mitotic spindle scaling can be modulated by changing the levels of a single protein: the microtubule polymerase XMAP215. Mol Biol Cell 2018; 29:1311-1317. [PMID: 29851557 PMCID: PMC5994900 DOI: 10.1091/mbc.e18-01-0011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In many organisms, early embryonic development is characterized by a series of reductive cell divisions that result in rapid increases in cell number and concomitant decreases in cell size. Intracellular organelles, such as the nucleus and mitotic spindle, also become progressively smaller during this developmental window, but the molecular and mechanistic underpinnings of these scaling relationships are not fully understood. For the mitotic spindle, changes in cytoplasmic volume are sufficient to account for size scaling during early development in certain organisms. This observation is consistent with models that evoke a limiting component, whereby the smaller absolute number of spindle components in smaller cells limits spindle size. Here we investigate the role of a candidate factor for developmental spindle scaling, the microtubule polymerase XMAP215. Microinjection of additional XMAP215 protein into Xenopus laevis embryos was sufficient to induce the assembly of larger spindles during developmental stages 6.5, 7, and 8, whereas addition of a polymerase-incompetent XMAP215 mutant resulted in a downward shift in the in vivo spindle scaling curve. In sum, these results indicate that even small cells are able to produce larger spindles if microtubule growth rates are increased and suggest that structural components are not limiting.
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Affiliation(s)
- Ana Milunovic-Jevtic
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071.,Molecular and Cellular Life Sciences Program, University of Wyoming, Laramie, WY 82071
| | - Predrag Jevtic
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071.,Molecular and Cellular Life Sciences Program, University of Wyoming, Laramie, WY 82071
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071.,Molecular and Cellular Life Sciences Program, University of Wyoming, Laramie, WY 82071
| | - J C Gatlin
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071.,Molecular and Cellular Life Sciences Program, University of Wyoming, Laramie, WY 82071
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63
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Abstract
The activation of the zygotic genome and onset of transcription in blastula embryos is linked to changes in cell behavior and remodeling of the cell cycle and constitutes a transition from exclusive maternal to zygotic control of development. This step in development is referred to as mid-blastula transition and has served as a paradigm for the link between developmental program and cell behavior and morphology. Here, we discuss the mechanism and functional relationships between the zygotic genome activation and cell cycle control during mid-blastula transition with a focus on Drosophila embryos.
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Affiliation(s)
- Boyang Liu
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany
| | - Jörg Grosshans
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany.
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64
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Jevtić P, Milunović-Jevtić A, Dilsaver MR, Gatlin JC, Levy DL. Use of Xenopus cell-free extracts to study size regulation of subcellular structures. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2018; 60:277-288. [PMID: 27759156 DOI: 10.1387/ijdb.160158dl] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Striking size variations are prominent throughout biology, at the organismal, cellular, and subcellular levels. Important fundamental questions concern organelle size regulation and how organelle size is regulated relative to cell size, also known as scaling. Uncovering mechanisms of organelle size regulation will inform the functional significance of size as well as the implications of misregulated size, for instance in the case of nuclear enlargement in cancer. Xenopus egg and embryo extracts are powerful cell-free systems that have been utilized extensively for mechanistic and functional studies of various organelles and subcellular structures. The open biochemical nature of the extract permits facile manipulation of its composition, and in recent years extract approaches have illuminated mechanisms of organelle size regulation. This review largely focuses on in vitro Xenopus studies that have identified regulators of nuclear and spindle size. We also discuss potential relationships between size scaling of the nucleus and spindle, size regulation of other subcellular structures, and extract experiments that have clarified developmental timing mechanisms. We conclude by offering some future prospects, notably the integration of Xenopus extract with microfluidic technology.
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Affiliation(s)
- Predrag Jevtić
- Department of Molecular Biology, University of Wyoming, Laramie, WY, USA
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65
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Winata CL, Łapiński M, Pryszcz L, Vaz C, Bin Ismail MH, Nama S, Hajan HS, Lee SGP, Korzh V, Sampath P, Tanavde V, Mathavan S. Cytoplasmic polyadenylation-mediated translational control of maternal mRNAs directs maternal-to-zygotic transition. Development 2018; 145:dev.159566. [PMID: 29229769 DOI: 10.1242/dev.159566] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 11/20/2017] [Indexed: 10/18/2022]
Abstract
In the earliest stages of animal development following fertilization, maternally deposited mRNAs direct biological processes to the point of zygotic genome activation (ZGA). These maternal mRNAs undergo cytoplasmic polyadenylation (CPA), suggesting translational control of their activation. To elucidate the biological role of CPA during embryogenesis, we performed genome-wide polysome profiling at several stages of zebrafish development. Our analysis revealed a correlation between CPA and polysome-association dynamics, demonstrating a coupling of translation to the CPA of maternal mRNAs. Pan-embryonic CPA inhibition disrupted the maternal-to-zygotic transition (MZT), causing a failure of developmental progression beyond the mid-blastula transition and changes in global gene expression that indicated a failure of ZGA and maternal mRNA clearance. Among the genes that were differentially expressed were those encoding chromatin modifiers and key transcription factors involved in ZGA, including nanog, pou5f3 and sox19b, which have distinct CPA dynamics. Our results establish the necessity of CPA for ensuring progression of the MZT. The RNA-seq data generated in this study represent a valuable zebrafish resource for the discovery of novel elements of the early embryonic transcriptome.
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Affiliation(s)
- Cecilia Lanny Winata
- International Institute of Molecular and Cell Biology in Warsaw, 02-109 Warsaw, Poland .,Max-Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Maciej Łapiński
- International Institute of Molecular and Cell Biology in Warsaw, 02-109 Warsaw, Poland
| | - Leszek Pryszcz
- International Institute of Molecular and Cell Biology in Warsaw, 02-109 Warsaw, Poland
| | - Candida Vaz
- Bioinformatics Institute, Agency for Science Technology and Research, 138671 Singapore
| | | | - Srikanth Nama
- Institute of Medical Biology, Agency of Science Technology and Research, 138648 Singapore
| | - Hajira Shreen Hajan
- Genome Institute of Singapore, Agency of Science Technology and Research, 138672 Singapore
| | - Serene Gek Ping Lee
- Genome Institute of Singapore, Agency of Science Technology and Research, 138672 Singapore
| | - Vladimir Korzh
- International Institute of Molecular and Cell Biology in Warsaw, 02-109 Warsaw, Poland.,Institute of Molecular and Cell Biology, Agency of Science Technology and Research, 138673 Singapore
| | - Prabha Sampath
- Institute of Medical Biology, Agency of Science Technology and Research, 138648 Singapore.,Yong Loo Lin School of Medicine, National University of Singapore, 117596 Singapore.,Program in Cancer and Stem Cell Biology, Duke-NUS Medical School, 169857 Singapore
| | - Vivek Tanavde
- Bioinformatics Institute, Agency for Science Technology and Research, 138671 Singapore.,Institute of Medical Biology, Agency of Science Technology and Research, 138648 Singapore
| | - Sinnakaruppan Mathavan
- Genome Institute of Singapore, Agency of Science Technology and Research, 138672 Singapore .,Vision Research Foundation, Sankara Nethralaya, 600 006 Chennai, India
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66
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Meier M, Grant J, Dowdle A, Thomas A, Gerton J, Collas P, O'Sullivan JM, Horsfield JA. Cohesin facilitates zygotic genome activation in zebrafish. Development 2018; 145:dev156521. [PMID: 29158440 DOI: 10.1242/dev.156521] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Accepted: 11/07/2017] [Indexed: 02/01/2023]
Abstract
At zygotic genome activation (ZGA), changes in chromatin structure are associated with new transcription immediately following the maternal-to-zygotic transition (MZT). The nuclear architectural proteins cohesin and CCCTC-binding factor (CTCF) contribute to chromatin structure and gene regulation. We show here that normal cohesin function is important for ZGA in zebrafish. Depletion of the cohesin subunit Rad21 delays ZGA without affecting cell cycle progression. In contrast, CTCF depletion has little effect on ZGA, whereas complete abrogation is lethal. Genome-wide analysis of Rad21 binding reveals a change in distribution from pericentromeric satellite DNA and other locations, including the miR-430 locus (the products of which are responsible for maternal transcript degradation), to genes, as embryos progress through the MZT. After MZT, a subset of Rad21 binding overlaps the pioneer factor Pou5f3, which activates early expressed genes. Rad21 depletion disrupts the formation of nucleoli and RNA polymerase II foci, suggestive of global defects in chromosome architecture. We propose that Rad21/cohesin redistribution to active areas of the genome is key to the establishment of chromosome organization and the embryonic developmental program.
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Affiliation(s)
- Michael Meier
- Department of Pathology, University of Otago, Dunedin 9016, New Zealand
| | - Jenny Grant
- Department of Pathology, University of Otago, Dunedin 9016, New Zealand
| | - Amy Dowdle
- Department of Pathology, University of Otago, Dunedin 9016, New Zealand
| | - Amarni Thomas
- Department of Pathology, University of Otago, Dunedin 9016, New Zealand
| | - Jennifer Gerton
- Stowers Institute for Medical Research, 1000 E 50th Street, Kansas City, MO 64110, USA
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Philippe Collas
- Department of Molecular Medicine, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Oslo 0316, Norway
| | - Justin M O'Sullivan
- Liggins Institute, The University of Auckland, Private Bag 92019, Auckland 1023, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
| | - Julia A Horsfield
- Department of Pathology, University of Otago, Dunedin 9016, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
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67
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Breaking the scale: how disrupting the karyoplasmic ratio gives cancer cells an advantage for metastatic invasion. Biochem Soc Trans 2017; 45:1333-1344. [PMID: 29150524 DOI: 10.1042/bst20170153] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 09/28/2017] [Accepted: 10/16/2017] [Indexed: 01/03/2023]
Abstract
Nuclear size normally scales with the size of the cell, but in cancer this 'karyoplasmic ratio' is disrupted. This is particularly so in more metastatic tumors where changes in the karyoplasmic ratio are used in both diagnosis and prognosis for several tumor types. However, the direction of nuclear size changes differs for particular tumor types: for example in breast cancer, larger nuclear size correlates with increased metastasis, while for lung cancer smaller nuclear size correlates with increased metastasis. Thus, there must be tissue-specific drivers of the nuclear size changes, but proteins thus far linked to nuclear size regulation are widely expressed. Notably, for these tumor types, ploidy changes have been excluded as the basis for nuclear size changes, and so, the increased metastasis is more likely to have a basis in the nuclear morphology change itself. We review what is known about nuclear size regulation and postulate how such nuclear size changes can increase metastasis and why the directionality can differ for particular tumor types.
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68
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Abstract
Background. Nuclear size is a tightly regulated cellular feature. Mechanisms that regulate nuclear size and the functional significance of this regulation are largely unknown. Nuclear size and morphology are often altered in many diseases, such as cancer. Therefore, understanding the mechanisms that regulate nuclear size is crucial to provide insight into the role of nuclear size in disease. Scope and Approach. The goal of this review is to summarize the most recent studies about the mechanisms and functional significance of nuclear size control using the Xenopus model system. First, this review describes how Xenopus egg extracts, embryos, and embryo extracts are prepared and used in scientific research. Next, the review focuses on the mechanisms and functional effects of proper nuclear size control that have been learned using the Xenopus system. Key Findings and Conclusions. Xenopus is an excellent in vivo and in vitro experimental platform to study mechanisms of nuclear size control. Given its close evolutionary relationship with mammals and that most cellular processes and pathways are highly conserved between Xenopus and humans, the Xenopus system has been a valuable tool to advance biomedical research. Some of the mechanisms that regulate nuclear size include components of nuclear import such as importin α and NTF2, nuclear lamins, nucleoporins, proteins that regulate the morphology of the endoplasmic reticulum, and cytoskeletal elements.
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69
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Abstract
In this issue of Developmental Cell, Kyogoku and Kitajima (2017) investigate the effect of cytoplasmic volume on the fidelity of chromosome segregation during meiosis in mouse oocytes. The authors find that large cytoplasmic volume affects spindle pole morphology, chromosome alignment, and stringency of checkpoint signaling, resulting in error-prone chromosome segregation.
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Affiliation(s)
- Predrag Jevtić
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
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70
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Jukam D, Shariati SAM, Skotheim JM. Zygotic Genome Activation in Vertebrates. Dev Cell 2017; 42:316-332. [PMID: 28829942 PMCID: PMC5714289 DOI: 10.1016/j.devcel.2017.07.026] [Citation(s) in RCA: 246] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/25/2017] [Accepted: 07/28/2017] [Indexed: 12/12/2022]
Abstract
The first major developmental transition in vertebrate embryos is the maternal-to-zygotic transition (MZT) when maternal mRNAs are degraded and zygotic transcription begins. During the MZT, the embryo takes charge of gene expression to control cell differentiation and further development. This spectacular organismal transition requires nuclear reprogramming and the initiation of RNAPII at thousands of promoters. Zygotic genome activation (ZGA) is mechanistically coordinated with other embryonic events, including changes in the cell cycle, chromatin state, and nuclear-to-cytoplasmic component ratios. Here, we review progress in understanding vertebrate ZGA dynamics in frogs, fish, mice, and humans to explore differences and emphasize common features.
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Affiliation(s)
- David Jukam
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - S Ali M Shariati
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
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71
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Both Nuclear Size and DNA Amount Contribute to Midblastula Transition Timing in Xenopus laevis. Sci Rep 2017; 7:7908. [PMID: 28801588 PMCID: PMC5554259 DOI: 10.1038/s41598-017-08243-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 07/10/2017] [Indexed: 11/08/2022] Open
Abstract
During early Xenopus laevis embryogenesis both nuclear and cell volumes decrease with the nuclear-to-cytoplasmic (N/C) volume ratio reaching a maximum at the midblastula transition (MBT). At the MBT, embryonic transcription is upregulated and cell cycles lengthen. Early studies demonstrated a role for the DNA-to-cytoplasmic ratio in the control of MBT timing. By altering nuclear size, we previously showed that the N/C volume ratio also contributes to proper MBT timing. Here we examine the relative contributions of nuclear size and DNA amount to MBT timing by simultaneously altering nuclear size and ploidy in X. laevis embryos. Compared to diploid embryos, haploids exhibited a delay in both zygotic gene expression and cell cycle lengthening, while diploid embryos with increased N/C volume ratios showed early expression of zygotic genes and premature lengthening of cell cycles. Interestingly, haploids with increased N/C volume ratios exhibited an intermediate effect on the timing of zygotic gene expression and cell cycle lengthening. Decreasing nuclear size in post-MBT haploid embryos caused a further delay in cell cycle lengthening and the expression of some zygotic genes. Our data suggest that both the N/C volume ratio and DNA amount contribute to the regulation of MBT timing with neither parameter being dominant.
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72
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Edens LJ, Dilsaver MR, Levy DL. PKC-mediated phosphorylation of nuclear lamins at a single serine residue regulates interphase nuclear size in Xenopus and mammalian cells. Mol Biol Cell 2017; 28:1389-1399. [PMID: 28356420 PMCID: PMC5426852 DOI: 10.1091/mbc.e16-11-0786] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 03/15/2017] [Accepted: 03/21/2017] [Indexed: 01/01/2023] Open
Abstract
How nuclear size is regulated is a fundamental cell-biological question with relevance to cancers, which often exhibit enlarged nuclei. We previously reported that conventional protein kinase C (cPKC) contributes to nuclear size reductions that occur during early Xenopus development. Here we report that PKC-mediated phosphorylation of lamin B3 (LB3) contributes to this mechanism of nuclear size regulation. By mapping PKC phosphorylation sites on LB3 and testing the effects of phosphomutants in Xenopus laevis embryos, we identify the novel site S267 as being an important determinant of nuclear size. Furthermore, FRAP studies demonstrate that phosphorylation at this site increases lamina dynamics, providing a mechanistic explanation for how PKC activity influences nuclear size. We subsequently map this X. laevis LB3 phosphorylation site to a conserved site in mammalian lamin A (LA), S268. Manipulating PKC activity in cultured mammalian cells alters nuclear size, as does expression of LA-S268 phosphomutants. Taken together, these data demonstrate that PKC-mediated lamin phosphorylation is a conserved mechanism of nuclear size regulation.
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Affiliation(s)
- Lisa J Edens
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - Matthew R Dilsaver
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
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73
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Joseph SR, Pálfy M, Hilbert L, Kumar M, Karschau J, Zaburdaev V, Shevchenko A, Vastenhouw NL. Competition between histone and transcription factor binding regulates the onset of transcription in zebrafish embryos. eLife 2017; 6. [PMID: 28425915 PMCID: PMC5451213 DOI: 10.7554/elife.23326] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 04/19/2017] [Indexed: 01/09/2023] Open
Abstract
Upon fertilization, the genome of animal embryos remains transcriptionally inactive until the maternal-to-zygotic transition. At this time, the embryo takes control of its development and transcription begins. How the onset of zygotic transcription is regulated remains unclear. Here, we show that a dynamic competition for DNA binding between nucleosome-forming histones and transcription factors regulates zebrafish genome activation. Taking a quantitative approach, we found that the concentration of non-DNA-bound core histones sets the time for the onset of transcription. The reduction in nuclear histone concentration that coincides with genome activation does not affect nucleosome density on DNA, but allows transcription factors to compete successfully for DNA binding. In agreement with this, transcription factor binding is sensitive to histone levels and the concentration of transcription factors also affects the time of transcription. Our results demonstrate that the relative levels of histones and transcription factors regulate the onset of transcription in the embryo. DOI:http://dx.doi.org/10.7554/eLife.23326.001 The DNA in a fertilized egg contains all the information required to form an animal’s body. In order for the animal to develop properly, particular genes encoded in the DNA are only active at specific times. The DNA is wrapped around proteins called histones, which allows the DNA to be tightly packed inside the cell. However, histones can block other proteins called transcription factors from binding to the DNA to activate the genes. Young embryos initially develop with all of their genes switched off, relying on the nutrients and other molecules provided by their mother. After some time, the embryo starts to switch on its own genes to take control of its own development, but it was not clear how this happens. Joseph et al. investigated how genes are activated in zebrafish embryos, which are often used as models to study how animals develop. The experiments show that competition between histones and transcription factors for binding to DNA controls when genes are switched on. In young fish embryos, there are so many histones present that transcription factors have no opportunity to bind to DNA. Over time, however, the numbers of histones decrease, allowing transcription factors to bind to DNA and switch on genes. Histones and transcription factors regulate the activity of genes throughout the life of the animal. Therefore, competition between these two types of protein may also control gene activity in other situations. A better understanding of how gene activity is controlled could allow researchers to more easily grow different types of cell in the laboratory or to reprogram specific cells in the body. As such, these new findings may aid the development of therapies to regenerate organs or tissues that have been damaged by injury or disease. DOI:http://dx.doi.org/10.7554/eLife.23326.002
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Affiliation(s)
- Shai R Joseph
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Máté Pálfy
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Lennart Hilbert
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Center for Systems Biology Dresden, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Mukesh Kumar
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Jens Karschau
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Vasily Zaburdaev
- Center for Systems Biology Dresden, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Andrej Shevchenko
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Nadine L Vastenhouw
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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74
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Oda H, Shirai N, Ura N, Ohsumi K, Iwabuchi M. Chromatin tethering to the nuclear envelope by nuclear actin filaments: a novel role of the actin cytoskeleton in the Xenopus blastula. Genes Cells 2017; 22:376-391. [PMID: 28318078 DOI: 10.1111/gtc.12483] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 01/30/2017] [Indexed: 12/17/2022]
Abstract
The Xenopus oocyte is known to accumulate filamentous or F-actin in the nucleus, but it is currently unknown whether F-actin also accumulates in embryo nuclei. Using fluorescence-labeled actin reporters, we examined the actin distribution in Xenopus embryonic cells and found that F-actin accumulates in nuclei during the blastula stage but not during the gastrula stage. To further investigate nuclear F-actin, we devised a Xenopus egg extract that reproduces the formation of nuclei in which F-actin accumulates. Using this extract, we found that F-actin accumulates primarily at the subnuclear membranous region and is essential to maintain chromatin binding to the nuclear envelope in well-developed nuclei. We also provide evidence that nuclear F-actin increases the structural stability of nuclei and contributes to chromosome alignment on the mitotic spindle at the following M phase. These results suggest the physiological importance of nuclear F-actin accumulation in rapidly dividing large Xenopus blastula cells.
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Affiliation(s)
- Haruka Oda
- Group of Developmental Cell Biology, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Natsuki Shirai
- Group of Developmental Cell Biology, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Naoko Ura
- Group of Developmental Cell Biology, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Keita Ohsumi
- Group of Developmental Cell Biology, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Mari Iwabuchi
- Group of Developmental Cell Biology, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
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75
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Pálfy M, Joseph SR, Vastenhouw NL. The timing of zygotic genome activation. Curr Opin Genet Dev 2017; 43:53-60. [PMID: 28088031 DOI: 10.1016/j.gde.2016.12.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 12/01/2016] [Accepted: 12/02/2016] [Indexed: 12/20/2022]
Abstract
After fertilization, the embryonic genome is inactive until transcription is initiated during the maternal-to-zygotic transition. How the onset of transcription is regulated in a precisely timed manner, however, is a long standing question in biology. Several mechanisms have been shown to contribute to the temporal regulation of genome activation but none of them can fully explain the general absence of transcription as well the gene specific onset that follows. Here we review the work that has been done toward elucidating the mechanisms underlying the temporal regulation of transcription in embryos.
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Affiliation(s)
- Máté Pálfy
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Shai R Joseph
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Nadine L Vastenhouw
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
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76
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Zhang M, Skirkanich J, Lampson MA, Klein PS. Cell Cycle Remodeling and Zygotic Gene Activation at the Midblastula Transition. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 953:441-487. [DOI: 10.1007/978-3-319-46095-6_9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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77
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Lin H, Min Z, Tao Q. The MLL/Setd1b methyltransferase is required for the Spemann's organizer gene activation in Xenopus. Mech Dev 2016; 142:1-9. [DOI: 10.1016/j.mod.2016.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 08/07/2016] [Accepted: 08/08/2016] [Indexed: 01/22/2023]
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78
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The Ciona intestinalis cleavage clock is independent of DNA methylation. Genomics 2016; 108:168-176. [DOI: 10.1016/j.ygeno.2016.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 09/01/2016] [Accepted: 10/02/2016] [Indexed: 11/20/2022]
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79
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Zeng W, Jiang S, Kong X, El-Ali N, Ball AR, Ma CIH, Hashimoto N, Yokomori K, Mortazavi A. Single-nucleus RNA-seq of differentiating human myoblasts reveals the extent of fate heterogeneity. Nucleic Acids Res 2016; 44:e158. [PMID: 27566152 PMCID: PMC5137429 DOI: 10.1093/nar/gkw739] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 08/09/2016] [Accepted: 08/12/2016] [Indexed: 01/05/2023] Open
Abstract
Myoblasts are precursor skeletal muscle cells that differentiate into fused, multinucleated myotubes. Current single-cell microfluidic methods are not optimized for capturing very large, multinucleated cells such as myotubes. To circumvent the problem, we performed single-nucleus transcriptome analysis. Using immortalized human myoblasts, we performed RNA-seq analysis of single cells (scRNA-seq) and single nuclei (snRNA-seq) and found them comparable, with a distinct enrichment for long non-coding RNAs (lncRNAs) in snRNA-seq. We then compared snRNA-seq of myoblasts before and after differentiation. We observed the presence of mononucleated cells (MNCs) that remained unfused and analyzed separately from multi-nucleated myotubes. We found that while the transcriptome profiles of myoblast and myotube nuclei are relatively homogeneous, MNC nuclei exhibited significant heterogeneity, with the majority of them adopting a distinct mesenchymal state. Primary transcripts for microRNAs (miRNAs) that participate in skeletal muscle differentiation were among the most differentially expressed lncRNAs, which we validated using NanoString. Our study demonstrates that snRNA-seq provides reliable transcriptome quantification for cells that are otherwise not amenable to current single-cell platforms. Our results further indicate that snRNA-seq has unique advantage in capturing nucleus-enriched lncRNAs and miRNA precursors that are useful in mapping and monitoring differential miRNA expression during cellular differentiation.
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Affiliation(s)
- Weihua Zeng
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697-2300, USA.,Center for Complex Biological Systems, University of California Irvine, Irvine, CA 92697-2280, USA
| | - Shan Jiang
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697-2300, USA.,Center for Complex Biological Systems, University of California Irvine, Irvine, CA 92697-2280, USA
| | - Xiangduo Kong
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA 92697-1700, USA
| | - Nicole El-Ali
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697-2300, USA.,Center for Complex Biological Systems, University of California Irvine, Irvine, CA 92697-2280, USA
| | - Alexander R Ball
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA 92697-1700, USA
| | - Christopher I-Hsing Ma
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA 92697-1700, USA
| | - Naohiro Hashimoto
- Department of Regenerative Medicine, National Center for Geriatrics and Gerontology, 7-430 Morioka, Oobu, Aichi 474-8522, Japan
| | - Kyoko Yokomori
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA 92697-1700, USA
| | - Ali Mortazavi
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697-2300, USA .,Center for Complex Biological Systems, University of California Irvine, Irvine, CA 92697-2280, USA
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80
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Edens LJ, Levy DL. A Cell-Free Assay Using Xenopus laevis Embryo Extracts to Study Mechanisms of Nuclear Size Regulation. J Vis Exp 2016. [PMID: 27584618 DOI: 10.3791/54173] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
A fundamental question in cell biology is how cell and organelle sizes are regulated. It has long been recognized that the size of the nucleus generally scales with the size of the cell, notably during embryogenesis when dramatic reductions in both cell and nuclear sizes occur. Mechanisms of nuclear size regulation are largely unknown and may be relevant to cancer where altered nuclear size is a key diagnostic and prognostic parameter. In vivo approaches to identifying nuclear size regulators are complicated by the essential and complex nature of nuclear function. The in vitro approach described here to study nuclear size control takes advantage of the normal reductions in nuclear size that occur during Xenopus laevis development. First, nuclei are assembled in X. laevis egg extract. Then, these nuclei are isolated and resuspended in cytoplasm from late stage embryos. After a 30 - 90 min incubation period, nuclear surface area decreases by 20 - 60%, providing a useful assay to identify cytoplasmic components present in late stage embryos that contribute to developmental nuclear size scaling. A major advantage of this approach is the relative facility with which the egg and embryo extracts can be biochemically manipulated, allowing for the identification of novel proteins and activities that regulate nuclear size. As with any in vitro approach, validation of results in an in vivo system is important, and microinjection of X. laevis embryos is particularly appropriate for these studies.
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Affiliation(s)
- Lisa J Edens
- Department of Molecular Biology, University of Wyoming
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming;
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81
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Abstract
Cells of a given type maintain a characteristic cell size to function efficiently in their ecological or organismal context. They achieve this through the regulation of growth rates or by actively sensing size and coupling this signal to cell division. We focus this review on potential size-sensing mechanisms, including geometric, external cue, and titration mechanisms. Mechanisms that titrate proteins against DNA are of particular interest because they are consistent with the robust correlation of DNA content and cell size. We review the literature, which suggests that titration mechanisms may underlie cell-size sensing in Xenopus embryos, budding yeast, and Escherichia coli, whereas alternative mechanisms may function in fission yeast.
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Affiliation(s)
- Amanda A Amodeo
- Department of Biology, Stanford University, Stanford, California 94305
| | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, California 94305
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82
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Abstract
Size and shape are important aspects of nuclear structure. While normal cells maintain nuclear size within a defined range, altered nuclear size and shape are associated with a variety of diseases. It is unknown if altered nuclear morphology contributes to pathology, and answering this question requires a better understanding of the mechanisms that control nuclear size and shape. In this review, we discuss recent advances in our understanding of the mechanisms that regulate nuclear morphology, focusing on nucleocytoplasmic transport, nuclear lamins, the endoplasmic reticulum, the cell cycle, and potential links between nuclear size and size regulation of other organelles. We then discuss the functional significance of nuclear morphology in the context of early embryonic development. Looking toward the future, we review new experimental approaches that promise to provide new insights into mechanisms of nuclear size control, in particular microfluidic-based technologies, and discuss how altered nuclear morphology might impact chromatin organization and physiology of diseased cells.
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Affiliation(s)
- Richik N Mukherjee
- a Department of Molecular Biology , University of Wyoming , Laramie , WY USA
| | - Pan Chen
- a Department of Molecular Biology , University of Wyoming , Laramie , WY USA
| | - Daniel L Levy
- a Department of Molecular Biology , University of Wyoming , Laramie , WY USA
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83
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Novakova L, Kovacovicova K, Dang-Nguyen TQ, Sodek M, Skultety M, Anger M. A Balance between Nuclear and Cytoplasmic Volumes Controls Spindle Length. PLoS One 2016; 11:e0149535. [PMID: 26886125 PMCID: PMC4757572 DOI: 10.1371/journal.pone.0149535] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 02/02/2016] [Indexed: 01/02/2023] Open
Abstract
Proper assembly of the spindle apparatus is crucially important for faithful chromosome segregation during anaphase. Thanks to the effort over the last decades, we have very detailed information about many events leading to spindle assembly and chromosome segregation, however we still do not understand certain aspects, including, for example, spindle length control. When tight regulation of spindle size is lost, chromosome segregation errors emerge. Currently, there are several hypotheses trying to explain the molecular mechanism of spindle length control. The number of kinetochores, activity of molecular rulers, intracellular gradients, cell size, limiting spindle components, and the balance of the spindle forces seem to contribute to spindle size regulation, however some of these mechanisms are likely specific to a particular cell type. In search for a general regulatory mechanism, in our study we focused on the role of cell size and nuclear to cytoplasmic ratio in this process. To this end, we used relatively large cells isolated from 2-cell mouse embryos. Our results showed that the spindle size upper limit is not reached in these cells and suggest that accurate control of spindle length requires balanced ratio between nuclear and cytoplasmic volumes.
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Affiliation(s)
- Lucia Novakova
- Central European Institute of Technology - Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics AS CR, Rumburska 89, 277 21 Libechov, Czech Republic
| | - Kristina Kovacovicova
- Central European Institute of Technology - Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics AS CR, Rumburska 89, 277 21 Libechov, Czech Republic
| | - Thanh Quang Dang-Nguyen
- Central European Institute of Technology - Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic
| | - Martin Sodek
- Central European Institute of Technology - Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics AS CR, Rumburska 89, 277 21 Libechov, Czech Republic
| | - Michal Skultety
- Central European Institute of Technology - Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic
| | - Martin Anger
- Central European Institute of Technology - Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics AS CR, Rumburska 89, 277 21 Libechov, Czech Republic
- * E-mail:
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84
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Vuković LD, Jevtić P, Zhang Z, Stohr BA, Levy DL. Nuclear size is sensitive to NTF2 protein levels in a manner dependent on Ran binding. J Cell Sci 2016; 129:1115-27. [PMID: 26823604 DOI: 10.1242/jcs.181263] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 01/20/2016] [Indexed: 12/20/2022] Open
Abstract
Altered nuclear size is associated with many cancers, and determining whether cancer-associated changes in nuclear size contribute to carcinogenesis necessitates an understanding of mechanisms of nuclear size regulation. Although nuclear import rates generally positively correlate with nuclear size, NTF2 levels negatively affect nuclear size, despite the role of NTF2 (also known as NUTF2) in nuclear recycling of the import factor Ran. We show that binding of Ran to NTF2 is required for NTF2 to inhibit nuclear expansion and import of large cargo molecules in Xenopus laevis egg and embryo extracts, consistent with our observation that NTF2 reduces the diameter of the nuclear pore complex (NPC) in a Ran-binding-dependent manner. Furthermore, we demonstrate that ectopic NTF2 expression in Xenopus embryos and mammalian tissue culture cells alters nuclear size. Finally, we show that increases in nuclear size during melanoma progression correlate with reduced NTF2 expression, and increasing NTF2 levels in melanoma cells is sufficient to reduce nuclear size. These results show a conserved capacity for NTF2 to impact on nuclear size, and we propose that NTF2 might be a new cancer biomarker.
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Affiliation(s)
- Lidija D Vuković
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - Predrag Jevtić
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - Zhaojie Zhang
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
| | - Bradley A Stohr
- Department of Pathology, University of California, San Francisco, CA 94143, USA
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
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85
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Vuković LD, Jevtić P, Edens LJ, Levy DL. New Insights into Mechanisms and Functions of Nuclear Size Regulation. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 322:1-59. [PMID: 26940517 DOI: 10.1016/bs.ircmb.2015.11.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Nuclear size is generally maintained within a defined range in a given cell type. Changes in cell size that occur during cell growth, development, and differentiation are accompanied by dynamic nuclear size adjustments in order to establish appropriate nuclear-to-cytoplasmic volume relationships. It has long been recognized that aberrations in nuclear size are associated with certain disease states, most notably cancer. Nuclear size and morphology must impact nuclear and cellular functions. Understanding these functional implications requires an understanding of the mechanisms that control nuclear size. In this review, we first provide a general overview of the diverse cellular structures and activities that contribute to nuclear size control, including structural components of the nucleus, effects of DNA amount and chromatin compaction, signaling, and transport pathways that impinge on the nucleus, extranuclear structures, and cell cycle state. We then detail some of the key mechanistic findings about nuclear size regulation that have been gleaned from a variety of model organisms. Lastly, we review studies that have implicated nuclear size in the regulation of cell and nuclear function and speculate on the potential functional significance of nuclear size in chromatin organization, gene expression, nuclear mechanics, and disease. With many fundamental cell biological questions remaining to be answered, the field of nuclear size regulation is still wide open.
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Affiliation(s)
- Lidija D Vuković
- Department of Molecular Biology, University of Wyoming, Laramie, WY, United States of America
| | - Predrag Jevtić
- Department of Molecular Biology, University of Wyoming, Laramie, WY, United States of America
| | - Lisa J Edens
- Department of Molecular Biology, University of Wyoming, Laramie, WY, United States of America
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY, United States of America.
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86
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87
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Jevtić P, Edens LJ, Li X, Nguyen T, Chen P, Levy DL. Concentration-dependent Effects of Nuclear Lamins on Nuclear Size in Xenopus and Mammalian Cells. J Biol Chem 2015; 290:27557-71. [PMID: 26429910 DOI: 10.1074/jbc.m115.673798] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Indexed: 12/17/2022] Open
Abstract
A fundamental question in cell biology concerns the regulation of organelle size. While nuclear size is exquisitely controlled in different cell types, inappropriate nuclear enlargement is used to diagnose and stage cancer. Clarifying the functional significance of nuclear size necessitates an understanding of the mechanisms and proteins that control nuclear size. One structural component implicated in the regulation of nuclear morphology is the nuclear lamina, a meshwork of intermediate lamin filaments that lines the inner nuclear membrane. However, there has not been a systematic investigation of how the level and type of lamin expression influences nuclear size, in part due to difficulties in precisely controlling lamin expression levels in vivo. In this study, we circumvent this limitation by studying nuclei in Xenopus laevis egg and embryo extracts, open biochemical systems that allow for precise manipulation of lamin levels by the addition of recombinant proteins. We find that nuclear growth and size are sensitive to the levels of nuclear lamins, with low and high concentrations increasing and decreasing nuclear size, respectively. Interestingly, each type of lamin that we tested (lamins B1, B2, B3, and A) similarly affected nuclear size whether added alone or in combination, suggesting that total lamin concentration, and not lamin type, is more critical to determining nuclear size. Furthermore, we show that altering lamin levels in vivo, both in Xenopus embryos and mammalian tissue culture cells, also impacts nuclear size. These results have implications for normal development and carcinogenesis where both nuclear size and lamin expression levels change.
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Affiliation(s)
- Predrag Jevtić
- From the Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
| | - Lisa J Edens
- From the Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
| | - Xiaoyang Li
- From the Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
| | - Thang Nguyen
- From the Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
| | - Pan Chen
- From the Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
| | - Daniel L Levy
- From the Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
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88
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Yang J, Aguero T, King ML. The Xenopus Maternal-to-Zygotic Transition from the Perspective of the Germline. Curr Top Dev Biol 2015; 113:271-303. [PMID: 26358876 DOI: 10.1016/bs.ctdb.2015.07.021] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In Xenopus, the germline is specified by the inheritance of germ-plasm components synthesized at the beginning of oogenesis. Only the cells in the early embryo that receive germ plasm, the primordial germ cells (PGCs), are competent to give rise to the gametes. Thus, germ-plasm components continue the totipotent potential exhibited by the oocyte into the developing embryo at a time when most cells are preprogrammed for somatic differentiation as dictated by localized maternal determinants. When zygotic transcription begins at the mid-blastula transition, the maternally set program for somatic differentiation is realized. At this time, genetic control is ceded to the zygotic genome, and developmental potential gradually becomes more restricted within the primary germ layers. PGCs are a notable exception to this paradigm and remain transcriptionally silent until the late gastrula. How the germ-cell lineage retains full potential while somatic cells become fate restricted is a tale of translational repression, selective degradation of somatic maternal determinants, and delayed activation of zygotic transcription.
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Affiliation(s)
- Jing Yang
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Tristan Aguero
- Department of Cell Biology, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Mary Lou King
- Department of Cell Biology, University of Miami, Miller School of Medicine, Miami, Florida, USA.
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89
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Levy DL, Heald R. Biological Scaling Problems and Solutions in Amphibians. Cold Spring Harb Perspect Biol 2015; 8:a019166. [PMID: 26261280 DOI: 10.1101/cshperspect.a019166] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Size is a primary feature of biological systems that varies at many levels, from the organism to its constituent cells and subcellular structures. Amphibians populate some of the extremes in biological size and have provided insight into scaling mechanisms, upper and lower size limits, and their physiological significance. Body size variation is a widespread evolutionary tactic among amphibians, with miniaturization frequently correlating with direct development that occurs without a tadpole stage. The large genomes of salamanders lead to large cell sizes that necessitate developmental modification and morphological simplification. Amphibian extremes at the cellular level have provided insight into mechanisms that accommodate cell-size differences. Finally, how organelles scale to cell size between species and during development has been investigated at the molecular level, because subcellular scaling can be recapitulated using Xenopus in vitro systems.
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Affiliation(s)
- Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
| | - Rebecca Heald
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720
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90
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Ladouceur AM, Dorn JF, Maddox PS. Mitotic chromosome length scales in response to both cell and nuclear size. J Cell Biol 2015; 209:645-51. [PMID: 26033258 PMCID: PMC4460153 DOI: 10.1083/jcb.201502092] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Accepted: 05/05/2015] [Indexed: 11/30/2022] Open
Abstract
Quantitative analysis relating cell, nuclear, and chromosome size in C. elegans embryos predicts two levels of chromosome length regulation in response to both cell and nuclear size. Multicellular development requires that cells reduce in size as a result of consecutive cell divisions without increase in embryo volume. To maintain cellular integrity, organelle size adapts to cell size throughout development. During mitosis, the longest chromosome arm must be shorter than half of the mitotic spindle for proper chromosome segregation. Using high-resolution time-lapse microscopy of living Caenorhabditis elegans embryos, we have quantified the relation between cell size and chromosome length. In control embryos, chromosome length scaled to cell size. Artificial reduction of cell size resulted in a shortening of chromosome length, following a trend predicted by measurements from control embryos. Disturbing the RAN (Ras-related nuclear protein)-GTP gradient decoupled nuclear size from cell size and resulted in chromosome scaling to nuclear size rather than cell size; smaller nuclei contained shorter chromosomes independent of cell size. In sum, quantitative analysis relating cell, nuclear, and chromosome size predicts two levels of chromosome length regulation: one through cell size and a second in response to nuclear size.
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Affiliation(s)
- Anne-Marie Ladouceur
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Jonas F Dorn
- Institute for Research in Immunology and Cancer (IRIC), Faculty of Medicine, University of Montreal, Montreal, Quebec H3T 1J4, Canada
| | - Paul S Maddox
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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91
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Hara Y, Merten CA. Dynein-Based Accumulation of Membranes Regulates Nuclear Expansion in Xenopus laevis Egg Extracts. Dev Cell 2015; 33:562-75. [PMID: 26004509 DOI: 10.1016/j.devcel.2015.04.016] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/02/2015] [Accepted: 04/22/2015] [Indexed: 10/23/2022]
Abstract
Nuclear size changes dynamically during development and has long been observed to correlate with the space surrounding the nucleus, as well as with the volume of the cell. Here we combine an in vitro cell-free system of Xenopus laevis egg extract with microfluidic devices to systematically analyze the effect of spatial constraints. The speed of nuclear expansion depended on the available space surrounding the nucleus up to a threshold volume in the nanoliter range, herein referred to as the nuclear domain. Under spatial constraints smaller than this nuclear domain, the size of microtubule-occupied space surrounding the nucleus turned out to be limiting for the accumulation of membranes around the nucleus via the motor protein dynein, therefore determining the speed of nuclear expansion. This mechanism explains how spatial information surrounding the nucleus, such as the positioning of the nucleus inside the cell, can control nuclear expansion.
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Affiliation(s)
- Yuki Hara
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany.
| | - Christoph A Merten
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany.
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92
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Arata Y, Takagi H, Sako Y, Sawa H. Power law relationship between cell cycle duration and cell volume in the early embryonic development of Caenorhabditis elegans. Front Physiol 2015; 5:529. [PMID: 25674063 PMCID: PMC4309120 DOI: 10.3389/fphys.2014.00529] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 12/27/2014] [Indexed: 11/13/2022] Open
Abstract
Cell size is a critical factor for cell cycle regulation. In Xenopus embryos after midblastula transition (MBT), the cell cycle duration elongates in a power law relationship with the cell radius squared. This correlation has been explained by the model that cell surface area is a candidate to determine cell cycle duration. However, it remains unknown whether this second power law is conserved in other animal embryos. Here, we found that the relationship between cell cycle duration and cell size in Caenorhabditis elegans embryos exhibited a power law distribution. Interestingly, the powers of the time-size relationship could be grouped into at least three classes: highly size-correlated, moderately size-correlated, and potentially a size-non-correlated class according to C. elegans founder cell lineages (1.2, 0.81, and <0.39 in radius, respectively). Thus, the power law relationship is conserved in Xenopus and C. elegans, while the absolute powers in C. elegans were different from that in Xenopus. Furthermore, we found that the volume ratio between the nucleus and cell exhibited a power law relationship in the size-correlated classes. The power of the volume relationship was closest to that of the time-size relationship in the highly size-correlated class. This correlation raised the possibility that the time-size relationship, at least in the highly size-correlated class, is explained by the volume ratio of nuclear size and cell size. Thus, our quantitative measurements shed a light on the possibility that early embryonic C. elegans cell cycle duration is coordinated with cell size as a result of geometric constraints between intracellular structures.
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Affiliation(s)
- Yukinobu Arata
- Laboratory for Cell Fate Decision, Center for Developmental Biology, RIKEN Hyogo, Japan ; Cellular Informatics Laboratory, RIKEN Saitama, Japan
| | - Hiroaki Takagi
- Department of Physics, School of Medicine, Nara Medical University Nara, Japan
| | - Yasushi Sako
- Cellular Informatics Laboratory, RIKEN Saitama, Japan
| | - Hitoshi Sawa
- Laboratory for Cell Fate Decision, Center for Developmental Biology, RIKEN Hyogo, Japan ; Multicellular Organization Laboratory, National Institute of Genetics Shizuoka, Japan
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Coordinating Cell Cycle Remodeling with Transcriptional Activation at the Drosophila MBT. Curr Top Dev Biol 2015; 113:113-48. [DOI: 10.1016/bs.ctdb.2015.06.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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