scholarly journals Characterization of the elastic properties of the nuclear envelope

2005 ◽  
Vol 2 (2) ◽  
pp. 63-69 ◽  
Author(s):  
A.C Rowat ◽  
L.J Foster ◽  
M.M Nielsen ◽  
M Weiss ◽  
J.H Ipsen
Keyword(s):  
Nuclear Envelope ◽  
Structural Stability ◽  
Large Scale ◽  
Critical Role ◽  
Coiled Coil ◽  
Nuclear Lamina ◽  
Elastic Behaviour ◽  
Nuclear Pore ◽  
Two Dimensional ◽  
Intermediate Filament Proteins

Underlying the nuclear envelope (NE) of most eukaryotic cells is the nuclear lamina, a meshwork consisting largely of coiled-coil nuclear intermediate filament proteins that play a critical role in nuclear organization and gene expression, and are vital for the structural stability of the NE/nucleus. By confocal microscopy and micromanipulation of the NE in living cells and isolated nuclei, we show that the NE undergoes deformations without large-scale rupture and maintains structural stability when exposed to mechanical stress. In conjunction with image analysis, we have developed theory for a two-dimensional elastic material to quantify NE elastic behaviour. We show that the NE is elastic and exhibits characteristics of a continuous two-dimensional solid, including connections between lamins and the embedded nuclear pore complexes. Correlating models of NE lateral organization to the experimental findings indicates a heterogeneous lateral distribution of NE components on a mesoscopic scale.

Nuclear envelope disassembly in mitotic extract requires functional nuclear pores and a nuclear lamina

1998 ◽  
Vol 111 (9) ◽  
pp. 1293-1303 ◽  
Author(s):  
P. Collas
Keyword(s):  
Nuclear Envelope ◽  
Sea Urchin ◽  
Nuclear Membrane ◽  
Critical Role ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Nuclear Pores ◽  
Lamin B ◽  
Nuclear Membranes

Using sea urchin embryonic and in-vitro-assembled nuclei incubated in sea urchin mitotic extract, I provide evidence for a requirement for functional nuclear pores and a nuclear lamina for nuclear envelope disassembly in vitro. In interphase gastrula nuclei, lamin B interacts with p56, an integral protein of inner nuclear membrane cross-reacting with antibodies to human lamin B receptor. Incubation of gastrula nuclei in mitotic cytosol containing an ATP-generating system rapidly induces hyperphosphorylation of p56 and lamin B. Subsequently, p56-lamin B interactions are weakened and the two proteins segregate into distinct nuclear envelope-derived vesicles upon disassembly of nuclear membranes and of the lamina. Nuclear disassembly is accompanied by chromatin condensation. Blocking nuclear pore function with wheat germ agglutinin or antibodies to nucleoporins prevents p56 and lamin B hyperphosphorylation, nuclear membrane breakdown and lamina solubilization. These events are not rescued by permeabilization of nuclear membranes to molecules of 150, 000 Mr with lysolecithin. In-vitro-assembled nuclei containing nuclear membranes with functional pores but no lamina do not disassemble in mitotic cytosol in spite of p56 hyperphosphorylation. Nuclear import of soluble lamin B and reformation of a lamina in interphase extract restores nuclear disassembly in mitotic cytosol. The data indicate a role for functional nuclear pores in nuclear disassembly in vitro. They show that p56 hyperphosphorylation is not sufficient for nuclear membrane disassembly in mitotic cytosol and argue that the nuclear lamina plays a critical role in nuclear disassembly at mitosis.

scholarly journals Nuclear envelope organization in Dictyostelium discoideum

2019 ◽  
Vol 63 (8-9-10) ◽  
pp. 509-519 ◽  
Author(s):  
Petros Batsios ◽  
Ralph Gräf ◽  
Michael P. Koonce ◽  
Denis A. Larochelle ◽  
Irene Meyer
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Nuclear Lamina ◽  
Major Constituent ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Linc Complex ◽  
Family Protein ◽  
Import And Export ◽  
Pore Complexes

The nuclear envelope consists of the outer and the inner nuclear membrane, the nuclear lamina and the nuclear pore complexes, which regulate nuclear import and export. The major constituent of the nuclear lamina of Dictyostelium is the lamin NE81. It can form filaments like B-type lamins and it interacts with Sun1, as well as with the LEM/HeH-family protein Src1. Sun1 and Src1 are nuclear envelope transmembrane proteins involved in the centrosome-nucleus connection and nuclear envelope stability at the nucleolar regions, respectively. In conjunction with a KASH-domain protein, Sun1 usually forms a so-called LINC complex. Two proteins with functions reminiscent of KASH-domain proteins at the outer nuclear membrane of Dictyostelium are known; interaptin which serves as an actin connector and the kinesin Kif9 which plays a role in the microtubule-centrosome connector. However, both of these lack the conserved KASH-domain. The link of the centrosome to the nuclear envelope is essential for the insertion of the centrosome into the nuclear envelope and the appropriate spindle formation. Moreover, centrosome insertion is involved in permeabilization of the mitotic nucleus, which ensures access of tubulin dimers and spindle assembly factors. Our recent progress in identifying key molecular players at the nuclear envelope of Dictyostelium promises further insights into the mechanisms of nuclear envelope dynamics.

scholarly journals High resolution scanning electron microscopy of the nuclear envelope: demonstration of a new, regular, fibrous lattice attached to the baskets of the nucleoplasmic face of the nuclear pores.

1992 ◽  
Vol 119 (6) ◽  
pp. 1429-1440 ◽  
Author(s):  
M W Goldberg ◽  
T D Allen
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Nuclear Envelope ◽  
Nuclear Lamina ◽  
Objective Lens ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Triturus Cristatus ◽  
Scanning Electron

The nuclear envelope (NE) of amphibian oocytes can be readily isolated in relatively structurally intact and pure form and has been used extensively for structural studies. Using high resolution scanning electron microscopy (HRSEM), both surfaces of the NE can be visualized in detail. Here, we demonstrate the use of HRSEM to obtain high resolution information of NE structure, confirming previous data and providing some new information. NEs, manually isolated from Triturus cristatus oocytes, have been mounted on conductive silicon chips, fixed, critical point dried and coated with a thin, continuous film of chromium or tantalum and viewed at relatively high accelerating voltage in a field emission scanning electron microscope with the sample within the objective lens. Both nucleoplasmic and cytoplasmic surfaces of the nuclear pore complexes (NPC) have been visualized, revealing the cytoplasmic coaxial ring, associated particles, central plug/transporter and spokes. The nucleoplasmic face is dominated by the previously described basketlike structure attached to the nucleoplasmic coaxial ring. In Triturus, a novel, highly regular flat sheet of fibers, termed the NE lattice (NEL) has been observed attached to the distal ring of the NPC basket. The NEL appears to be distinct from the nuclear lamina. Evidence for the NEL is also presented in thin TEM sections from Triturus oocytes and GVs and in spread NEs from Xenopus. A model is presented for NEL structure and its interaction with the NPCs is discussed.

scholarly journals Chromosome length and gene density contribute to micronuclear membrane stability

2021 ◽  
Author(s):  
Anna Mammel ◽  
Heather Z Huang ◽  
Amanda L Gunn ◽  
Emma Choo ◽  
Emily M Hatch
Keyword(s):  
Nuclear Envelope ◽  
Membrane Integrity ◽  
Nuclear Lamina ◽  
Chromosome Length ◽  
Gene Density ◽  
Membrane Stability ◽  
Nuclear Pore ◽  
Membrane Rupture ◽  
Lamin B1 ◽  
Nuclear Envelope Assembly

Micronuclei are derived from missegregated chromosomes and frequently lose membrane integrity, leading to DNA damage, innate immune activation, and metastatic signaling. Here we demonstrate that two characteristics of the trapped chromosome, length and gene density, are key contributors to micronuclei membrane stability in human cells. Chromosome length is proportional to micronuclei size, and gene density has an additive effect with micronucleus size on membrane stability. We demonstrate that these results are not due to chromosome-specific differences in spindle position or initial nuclear pore complex recruitment during post-mitotic nuclear envelope assembly. We find that chromosome length and micronuclei size strongly correlate with lamin B1 and nuclear pore density in intact micronuclei. Unexpectedly, lamin B1 levels do not predict nuclear lamina organization and membrane stability. Instead, small gene-dense micronuclei have decreased nuclear lamina gaps compared to large micronuclei, despite very low levels of lamin B1. Our data strongly suggest that nuclear envelope composition defects previously correlated with membrane rupture only partly explain membrane stability in micronuclei. We propose that an unknown factor linked to gene density has a separate function that inhibits the appearance of nuclear lamina gaps and delays membrane rupture until late in the cell cycle.

scholarly journals Chromosome length and gene density contribute to micronuclear membrane stability

2021 ◽  
Vol 5 (2) ◽  
pp. e202101210
Author(s):  
Anna E Mammel ◽  
Heather Z Huang ◽  
Amanda L Gunn ◽  
Emma Choo ◽  
Emily M Hatch
Keyword(s):  
Nuclear Envelope ◽  
Membrane Integrity ◽  
Nuclear Lamina ◽  
Chromosome Length ◽  
Gene Density ◽  
Membrane Stability ◽  
Nuclear Pore ◽  
Membrane Rupture ◽  
Lamin B1 ◽  
Nuclear Envelope Assembly

Micronuclei are derived from missegregated chromosomes and frequently lose membrane integrity, leading to DNA damage, innate immune activation, and metastatic signaling. Here, we demonstrate that two characteristics of the trapped chromosome, length and gene density, are key contributors to micronuclei membrane stability and determine the timing of micronucleus rupture. We demonstrate that these results are not due to chromosome-specific differences in spindle position or initial protein recruitment during post-mitotic nuclear envelope assembly. Micronucleus size strongly correlates with lamin B1 levels and nuclear pore density in intact micronuclei, but, unexpectedly, lamin B1 levels do not completely predict nuclear lamina organization or membrane stability. Instead, small gene-dense micronuclei have decreased nuclear lamina gaps compared to large micronuclei, despite very low levels of lamin B1. Our data strongly suggest that nuclear envelope composition defects previously correlated with membrane rupture only partly explain membrane stability in micronuclei. We propose that an unknown factor linked to gene density has a separate function that inhibits the appearance of nuclear lamina gaps and delays membrane rupture until late in the cell cycle.

scholarly journals Decreased mechanotransduction prevents nuclear collapse in aCaenorhabditis eleganslaminopathy

2020 ◽  
Vol 117 (49) ◽  
pp. 31301-31308
Author(s):  
Gabriela Huelgas-Morales ◽  
Mark Sanders ◽  
Gemechu Mekonnen ◽  
Tatsuya Tsukamoto ◽  
David Greenstein
Keyword(s):  
Nuclear Envelope ◽  
Complex Function ◽  
Nuclear Lamina ◽  
Premature Aging ◽  
Nuclear Pore ◽  
Linc Complex ◽  
Force Transmission ◽  
Cell Nuclei ◽  
Aaa Atpase ◽  
C Elegans

The function of the nucleus depends on the integrity of the nuclear lamina, an intermediate filament network associated with the linker of nucleoskeleton and cytoskeleton (LINC) complex. The LINC complex spans the nuclear envelope and mediates nuclear mechanotransduction, the process by which mechanical signals and forces are transmitted across the nuclear envelope. In turn, the AAA+ ATPase torsinA is thought to regulate force transmission from the cytoskeleton to the nucleus. In humans, mutations affecting nuclear envelope-associated proteins cause laminopathies, including progeria, myopathy, and dystonia, though the extent to which endogenous mechanical stresses contribute to these pathologies is unclear. Here, we use theCaenorhabditis elegansgermline as a model to investigate mechanisms that maintain nuclear integrity as germ cell nuclei progress through meiotic development and migrate for gametogenesis—processes that require LINC complex function. We report that decreasing the function of theC. eleganstorsinA homolog, OOC-5, rescues the sterility and premature aging caused by a null mutation in the single worm lamin homolog. We show that decreasing OOC-5/torsinA activity prevents nuclear collapse in lamin mutants by disrupting the function of the LINC complex. At a mechanistic level, OOC-5/torsinA promotes the assembly or maintenance of the lamin-associated LINC complex and this activity is also important for interphase nuclear pore complex insertion into growing germline nuclei. These results demonstrate that LINC complex-transmitted forces damage nuclei with a compromised nuclear lamina. Thus, the torsinA–LINC complex nexus might comprise a therapeutic target for certain laminopathies by preventing damage from endogenous cellular forces.

Relationships at the nuclear envelope: lamins and nuclear pore complexes in animals and plants

2010 ◽  
Vol 38 (3) ◽  
pp. 829-831 ◽  
Author(s):  
Jindriska Fiserova ◽  
Martin W. Goldberg
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Periphery ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nucleocytoplasmic Trafficking ◽  
Animal Cells ◽  
Cellular Processes ◽  
Associated Proteins ◽  
Pore Complexes

The nuclear envelope comprises a distinct compartment at the nuclear periphery that provides a platform for communication between the nucleus and cytoplasm. Signal transfer can proceed by multiple means. Primarily, this is by nucleocytoplasmic trafficking facilitated by NPCs (nuclear pore complexes). Recently, it has been indicated that signals can be transmitted from the cytoskeleton to the intranuclear structures via interlinking transmembrane proteins. In animal cells, the nuclear lamina tightly underlies the inner nuclear membrane and thus represents the protein structure located at the furthest boundary of the nucleus. It enables communication between the nucleus and the cytoplasm via its interactions with chromatin-binding proteins, transmembrane and membrane-associated proteins. Of particular interest is the interaction of the nuclear lamina with NPCs. As both structures fulfil essential roles in close proximity at the nuclear periphery, their interactions have a large impact on cellular processes resulting in affects on tissue differentiation and development. The present review concentrates on the structural and functional lamina–NPC relationship in animal cells and its potential implications to plants.

scholarly journals The Role of Nucleoporin Elys in Nuclear Pore Complex Assembly and Regulation of Genome Architecture

2020 ◽  
Vol 21 (24) ◽  
pp. 9475
Author(s):  
Yuri Y. Shevelyov
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Genome Architecture ◽  
Nuclear Pore Complexes ◽  
Current State ◽  
Long Time ◽  
Pore Complexes

For a long time, the nuclear lamina was thought to be the sole scaffold for the attachment of chromosomes to the nuclear envelope (NE) in metazoans. However, accumulating evidence indicates that nuclear pore complexes (NPCs) comprised of nucleoporins (Nups) participate in this process as well. One of the Nups, Elys, initiates NPC reassembly at the end of mitosis. Elys directly binds the decondensing chromatin and interacts with the Nup107–160 subcomplex of NPCs, thus serving as a seeding point for the subsequent recruitment of other NPC subcomplexes and connecting chromatin with the re-forming NE. Recent studies also uncovered the important functions of Elys during interphase where it interacts with chromatin and affects its compactness. Therefore, Elys seems to be one of the key Nups regulating chromatin organization. This review summarizes the current state of our knowledge about the participation of Elys in the post-mitotic NPC reassembly as well as the role that Elys and other Nups play in the maintenance of genome architecture.

scholarly journals Nuclear pore complex evolution: a trypanosome Mlp analogue functions in chromosomal segregation but lacks transcriptional barrier activity

2014 ◽  
Vol 25 (9) ◽  
pp. 1421-1436 ◽  
Author(s):  
Jennifer M. Holden ◽  
Ludek Koreny ◽  
Samson Obado ◽  
Alexander V. Ratushny ◽  
Wei-Ming Chen ◽  
...  
Keyword(s):  
Nuclear Pore Complex ◽  
Mitotic Spindle ◽  
Nuclear Periphery ◽  
Coiled Coil ◽  
Nuclear Lamina ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Dependent Manner ◽  
Major Barrier ◽  
African Trypanosomes

The nuclear pore complex (NPC) has dual roles in nucleocytoplasmic transport and chromatin organization. In many eukaryotes the coiled-coil Mlp/Tpr proteins of the NPC nuclear basket have specific functions in interactions with chromatin and defining specialized regions of active transcription, whereas Mlp2 associates with the mitotic spindle/NPC in a cell cycle–dependent manner. We previously identified two putative Mlp-related proteins in African trypanosomes, TbNup110 and TbNup92, the latter of which associates with the spindle. We now provide evidence for independent ancestry for TbNup92/TbNup110 and Mlp/Tpr proteins. However, TbNup92 is required for correct chromosome segregation, with knockout cells exhibiting microaneuploidy and lowered fidelity of telomere segregation. Further, TbNup92 is intimately associated with the mitotic spindle and spindle anchor site but apparently has minimal roles in control of gene transcription, indicating that TbNup92 lacks major barrier activity. TbNup92 therefore acts as a functional analogue of Mlp/Tpr proteins, and, together with the lamina analogue NUP-1, represents a cohort of novel proteins operating at the nuclear periphery of trypanosomes, uncovering complex evolutionary trajectories for the NPC and nuclear lamina.

HRSEM of the nuclear envelope (NE): Nuclear pore substructure; baskets and fibrous components

1992 ◽  
Vol 50 (1) ◽  
pp. 492-493 ◽  
Author(s):  
Martin W. Goldberg ◽  
Terence D. Allen
Keyword(s):  
Nuclear Envelope ◽  
Low Voltage ◽  
Ion Beam ◽  
Membrane Surface ◽  
Three Dimensional ◽  
Nuclear Lamina ◽  
Ring Structure ◽  
Objective Lens ◽  
Nuclear Pore ◽  
Three Dimensional Model

The nuclear envelope (NE) of eukaryotic cells has been studied for many years by a variety of em techniques yielding a three dimensional model of the nuclear pore complex (NPC) consisting of two rings (∼120nm diameter), one at the outer NE and one at the inner NE. Between the rings are eight spoke structures and a central plug. The cytoplasmic ring may be decorated with up to eight particles. The NPCs are embedded in a proteinaceous network: the nuclear lamina. Recently, low voltage HRSEM was used to show the existence of a basket-like structure attached to the nucleoplasmic ring. SEM is an ideal technique for the study of membrane surfaces. High resolution can be achieved in SEMs by the use of a field emission source which produces a high brightness probe of less than lnm diameter and a specimen stage within the objective lens, reducing chromatic abberations and production of SEIII electrons. Resolution of biological specimens can be further enhanced by coating with thin, continuous films of refractory metals such as chromium or tantalum which allows the use of higher accelerating voltages and magnifications. The NEs of Xenopus oocyte germinal vesicles have been prepared as previously described for HRSEM without detergent except they have been coated nominally with 3nm of tantalum by magnetron sputtering instead of ion beam sputtered platinum. NEs have then been examined at 30kV. The ring, plug/spoke complex and particles can all be seen at the cytoplasmic surface as well as details of the outer membrane structure and particles associated with it (Fig. 1). On the nucleoplasmic surface (Fig. 2) the inner ring is observed. It has a subunit appearance with eight filaments extending from between the subunits to a third ring structure: these make up the basket-like structure. When ‘baskets’ are close together they are joined by fibres at the ‘basket ring’ (Fig. 2). When several baskets are in close proximity these fibres form a network like a canopy over the baskets (Fig. 3). Other fibres are present on the inner membrane surface which may be membrane associated fibres or canopy fibres that have collapsed. It is uncertain which, if any, of these fibres are lamins as a further level of fibres is observed at the level of the nucleoplasmic ring when the membrane is removed with detergent (Fig. 4). These fibres are consistent with previously described lamina.

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