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Gregory EF, Luxton GWG, Starr DA. Anchorage of H3K9-methylated heterochromatin to the nuclear periphery helps mediate P-cell nuclear migration though constricted spaces in Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.22.595380. [PMID: 38826247 PMCID: PMC11142143 DOI: 10.1101/2024.05.22.595380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Nuclei adjust their deformability while migrating through constrictions to enable structural changes and maintain nuclear integrity. The effect of heterochromatin anchored at the nucleoplasmic face of the inner nuclear membrane on nuclear morphology and deformability during in vivo nuclear migration through constricted spaces remains unclear. Here, we show that abolishing peripheral heterochromatin anchorage by eliminating CEC-4, a chromodomain protein that tethers H3K9-methylated chromatin to the nuclear periphery, disrupts constrained P-cell nuclear migration in Caenorhabditis elegans larvae in the absence of the established LINC complex-dependent pathway. CEC-4 acts in parallel to an actin and CDC-42-based pathway. We also demonstrate the necessity for the chromatin methyltransferases MET-2 and JMJD-1.2 during P-cell nuclear migration in the absence of functional LINC complexes. We conclude that H3K9-nethylated chromatin needs to be anchored to the nucleoplasmic face of the inner nuclear membrane to help facilitate nuclear migration through constricted spaces in vivo .
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Ma L, Kuhn J, Chang YT, Elnatan D, Luxton GWG, Starr DA. FLN-2 functions in parallel to LINC complexes and Cdc42/actin pathways during P-cell nuclear migration through constricted spaces in Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.04.552041. [PMID: 37577634 PMCID: PMC10418278 DOI: 10.1101/2023.08.04.552041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Nuclear migration through narrow constrictions is important for development, metastasis, and pro-inflammatory responses. Studies performed in tissue culture cells have implicated LINC (linker of nucleoskeleton and cytoskeleton) complexes, microtubule motors, the actin cytoskeleton, and nuclear envelope repair machinery as important mediators of nuclear movements through constricted spaces. However, little is understood about how these mechanisms operate to move nuclei in vivo. In C. elegans larvae, 6 pairs of hypodermal P cells migrate from lateral to ventral positions through a constricted space between the body wall muscles and the cuticle. P-cell nuclear migration is mediated in part by LINC complexes using a microtubule-based pathway and by an independent CDC-42/actin-based pathway. However, when both LINC complex and actin-based pathways are knocked out, many nuclei still migrate, suggesting the existence of additional pathways. Here we show that FLN-2 functions in a third pathway to mediate P-cell nuclear migration. The predicted N-terminal actin binding domain in FLN-2 that is found in canonical filamins is dispensable for FLN-2 function, this and structural predictions suggest that FLN-2 is not a divergent filamin. The immunoglobulin (Ig)-like repeats 4-8 of FLN-2 were necessary for P-cell nuclear migration. Furthermore, in the absence of the LINC complex component unc-84, fln-2 mutants had an increase in P-cell nuclear rupture. We conclude that FLN-2 functions to maintain the integrity of the nuclear envelope in parallel with the LINC complex and CDC-42/actin-based pathways to move P-cell nuclei through constricted spaces.
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Affiliation(s)
- Linda Ma
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Jonathan Kuhn
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Yu-Tai Chang
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Daniel Elnatan
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - G W Gant Luxton
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
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Pawar S, Kutay U. The Diverse Cellular Functions of Inner Nuclear Membrane Proteins. Cold Spring Harb Perspect Biol 2021; 13:a040477. [PMID: 33753404 PMCID: PMC8411953 DOI: 10.1101/cshperspect.a040477] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The nuclear compartment is delimited by a specialized expanded sheet of the endoplasmic reticulum (ER) known as the nuclear envelope (NE). Compared to the outer nuclear membrane and the contiguous peripheral ER, the inner nuclear membrane (INM) houses a unique set of transmembrane proteins that serve a staggering range of functions. Many of these functions reflect the exceptional position of INM proteins at the membrane-chromatin interface. Recent research revealed that numerous INM proteins perform crucial roles in chromatin organization, regulation of gene expression, genome stability, and mediation of signaling pathways into the nucleus. Other INM proteins establish mechanical links between chromatin and the cytoskeleton, help NE remodeling, or contribute to the surveillance of NE integrity and homeostasis. As INM proteins continue to gain prominence, we review these advancements and give an overview on the functional versatility of the INM proteome.
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Affiliation(s)
- Sumit Pawar
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Ulrike Kutay
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
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Fan J, Jin H, Koch BA, Yu HG. Mps2 links Csm4 and Mps3 to form a telomere-associated LINC complex in budding yeast. Life Sci Alliance 2020; 3:3/12/e202000824. [PMID: 32967926 PMCID: PMC7536833 DOI: 10.26508/lsa.202000824] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 09/10/2020] [Accepted: 09/11/2020] [Indexed: 11/24/2022] Open
Abstract
The canonical LINC complex is composed of two different transmembrane proteins; this work reveals the heterotrimeric composition of the telomere-associated LINC complex in budding yeast. The linker of the nucleoskeleton and cytoskeleton (LINC) complex is composed of two transmembrane proteins: the KASH domain protein localized to the outer nuclear membrane and the SUN domain protein to the inner nuclear membrane. In budding yeast, the sole SUN domain protein, Mps3, is thought to pair with either Csm4 or Mps2, two KASH-like proteins, to form two separate LINC complexes. Here, we show that Mps2 mediates the interaction between Csm4 and Mps3 to form a heterotrimeric telomere-associated LINC (t-LINC) complex in budding yeast meiosis. Mps2 binds to Csm4 and Mps3, and all three are localized to the telomere. Telomeric localization of Csm4 depends on both Mps2 and Mps3; in contrast, Mps2’s localization depends on Mps3 but not Csm4. Mps2-mediated t-LINC complex regulates telomere movement and meiotic recombination. By ectopically expressing CSM4 in vegetative yeast cells, we reconstitute the heterotrimeric t-LINC complex and demonstrate its ability to tether telomeres. Our findings therefore reveal the heterotrimeric composition of the t-LINC complex in budding yeast and have implications for understanding variant LINC complex formation.
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Affiliation(s)
- Jinbo Fan
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Hui Jin
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Bailey A Koch
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Hong-Guo Yu
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
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Bone CR, Chang YT, Cain NE, Murphy SP, Starr DA. Nuclei migrate through constricted spaces using microtubule motors and actin networks in C. elegans hypodermal cells. Development 2016; 143:4193-4202. [PMID: 27697906 DOI: 10.1242/dev.141192] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/20/2016] [Indexed: 12/22/2022]
Abstract
Cellular migrations through constricted spaces are a crucial aspect of many developmental and disease processes including hematopoiesis, inflammation and metastasis. A limiting factor in these events is nuclear deformation. Here, we establish an in vivo model in which nuclei can be visualized while moving through constrictions and use it to elucidate mechanisms for nuclear migration. C. elegans hypodermal P-cell larval nuclei traverse a narrow space that is about 5% their width. This constriction is blocked by fibrous organelles, structures that pass through P cells to connect the muscles to cuticle. Fibrous organelles are removed just prior to nuclear migration, when nuclei and lamins undergo extreme morphological changes to squeeze through the space. Both actin and microtubule networks are organized to mediate nuclear migration. The LINC complex, consisting of the SUN protein UNC-84 and the KASH protein UNC-83, recruits dynein and kinesin-1 to the nuclear surface. Both motors function in P-cell nuclear migration, but dynein, functioning through UNC-83, plays a more central role as nuclei migrate towards minus ends of polarized microtubule networks. Thus, the nucleoskeleton and cytoskeleton are coordinated to move nuclei through constricted spaces.
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Affiliation(s)
- Courtney R Bone
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Yu-Tai Chang
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Natalie E Cain
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Shaun P Murphy
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
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Fridolfsson HN, Starr DA. Kinesin-1 and dynein at the nuclear envelope mediate the bidirectional migrations of nuclei. ACTA ACUST UNITED AC 2010; 191:115-28. [PMID: 20921138 PMCID: PMC2953438 DOI: 10.1083/jcb.201004118] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Kinesin-1 and dynein are recruited to the nuclear envelope by the Caenorhabditis elegans klarsicht/ANC-1/Syne homology (KASH) protein UNC-83 to move nuclei. The mechanisms of how these motors are coordinated to mediate nuclear migration are unknown. Time-lapse differential interference contrast and fluorescence imaging of embryonic hypodermal nuclear migration events were used to characterize the kinetics of nuclear migration and determine microtubule dynamics and polarity. Wild-type nuclei display bidirectional movements during migration and are also able to roll past cytoplasmic granules. unc-83, unc-84, and kinesin-1 mutants have severe nuclear migration defects. Without dynein, nuclear migration initiates normally but lacks bidirectional movement and shows defects in nuclear rolling, implicating dynein in resolution of cytoplasmic roadblocks. Microtubules are highly dynamic during nuclear migration. EB1::green fluorescence protein imaging demonstrates that microtubules are polarized in the direction of nuclear migration. This organization of microtubules fits with our model that kinesin-1 moves nuclei forward and dynein functions to move nuclei backward for short stretches to bypass cellular roadblocks.
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Affiliation(s)
- Heidi N Fridolfsson
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA
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Starr DA, Fridolfsson HN. Interactions between nuclei and the cytoskeleton are mediated by SUN-KASH nuclear-envelope bridges. Annu Rev Cell Dev Biol 2010; 26:421-44. [PMID: 20507227 DOI: 10.1146/annurev-cellbio-100109-104037] [Citation(s) in RCA: 420] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The nuclear envelope links the cytoskeleton to structural components of the nucleus. It functions to coordinate nuclear migration and anchorage, organize chromatin, and aid meiotic chromosome pairing. Forces generated by the cytoskeleton are transferred across the nuclear envelope to the nuclear lamina through a nuclear-envelope bridge consisting of SUN (Sad1 and UNC-84) and KASH (Klarsicht, ANC-1 and Syne/Nesprin homology) proteins. Some KASH-SUN combinations connect microtubules, centrosomes, actin filaments, or intermediate filaments to the surface of the nucleus. Other combinations are used in cell cycle control, nuclear import, or apoptosis. Interactions between the cytoskeleton and the nucleus also affect global cytoskeleton organization. SUN and KASH proteins were identified through genetic screens for mispositioned nuclei in model organisms. Knockouts of SUN or KASH proteins disrupt neurological and muscular development in mice. Defects in SUN and KASH proteins have been linked to human diseases including muscular dystrophy, ataxia, progeria, lissencephaly, and cancer.
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Affiliation(s)
- Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
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Abstract
Positioning the nucleus is essential for the formation of polarized cells, pronuclear migration, cell division, cell migration and the organization of specialized syncytia such as mammalian skeletal muscles. Proteins that are required for nuclear positioning also function during chromosome movement and pairing in meiosis. Defects in these processes lead to human diseases including laminopathies. To properly position the nucleus or move chromosomes within the nucleus, the cell must specify the outer surface of the nucleus and transfer forces across both membranes of the nuclear envelope. KASH proteins are specifically recruited to the outer nuclear membrane by SUN proteins, which reside in the inner nuclear membrane. KASH and SUN proteins physically interact in the perinuclear space, forming a bridge across the two membranes of the nuclear envelope. The divergent N-terminal domains of KASH proteins extend from the surface of the nucleus into the cytoplasm and interact with the cytoskeleton, whereas the N-termini of SUN proteins extend into the nucleoplasm to interact with the lamina or chromatin. The bridge of SUN and KASH across the nuclear envelope functions to transfer forces that are generated in the cytoplasm into the nucleoplasm during nuclear migration, nuclear anchorage, centrosome attachment, intermediate-filament association and telomere clustering.
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Affiliation(s)
- Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA.
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Disturbed nuclear orientation and cellular migration in A-type lamin deficient cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:312-24. [DOI: 10.1016/j.bbamcr.2008.10.003] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Revised: 08/26/2008] [Accepted: 10/08/2008] [Indexed: 11/20/2022]
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Batrakou DG, Kerr ARW, Schirmer EC. Comparative proteomic analyses of the nuclear envelope and pore complex suggests a wide range of heretofore unexpected functions. J Proteomics 2008; 72:56-70. [PMID: 18852071 DOI: 10.1016/j.jprot.2008.09.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 08/26/2008] [Accepted: 09/18/2008] [Indexed: 12/31/2022]
Abstract
Since the discovery of several inherited diseases linked to the nuclear envelope the number of functions ascribed to this subcellular organelle has skyrocketed. However the molecular pathways underlying these functions are not clear in most cases, perhaps because of missing components. Several recent proteomic analyses of the nuclear envelope and nuclear pore complex proteomes have yielded not only enough missing components to potentially elucidate these pathways, but suggest an exponentially greater number of functions at the nuclear periphery than ever imagined. Many of these functions appear to derive from recapitulation of pathways utilized at the plasma membrane and from other membrane systems. Additionally, many proteins identified in the comparative nuclear envelope studies have sequence characteristics suggesting that they might also contribute to nuclear pore complex functions. In particular, the striking enrichment for proteins in the nuclear envelope fractions that carry phenylalanine-glycine (FG) repeats may be significant for the mechanism of nuclear transport. In retrospect, these findings are only surprising in context of the notion held for many years that the nuclear envelope was only a barrier protecting the genome. In fact, it is arguably the most complex membrane organelle in the cell.
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Affiliation(s)
- Dzmitry G Batrakou
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK
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