Dysfunctional Connections Between the Nucleus and the Actin and Microtubule Networks in Laminopathic Models

Hale, Christopher M.; Shrestha, Arun L.; Khatau, Shyam B.; Stewart-Hutchinson, Phillip J.; Hernandez, Lídia; Stewart, Colin L.; Hodzic, Didier; Wirtz, Denis

doi:10.1529/biophysj.108.139428

Cited by 185 publications

(229 citation statements)

References 61 publications

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“…We have recently shown that LINC complex proteins are displaced from the nucleus to the ER and cytoplasm in a majority of Lmna L530P/L530P cells (17). Similarly to Lmna Ϫ/Ϫ cells, Lmna L530P/L530P cells show no overt disorganization of their basal stress fibers compared to control WT cells (17).…”

Section: Resultsmentioning

confidence: 94%

“…Because the NE distribution of LINC complex proteins is altered in embryonic fibroblasts derived from mice lacking A-type lamins, a model of dilated cardiomyopathy and muscular dystrophy (15,16), we hypothesized that the depletion of lamin A/C from the nucleus would disrupt the organization of the actin cap and the regulation of nuclear shape by cell shape. While the organization of actin fibers away from the nucleus in Lmna Ϫ/Ϫ cells (imaged by focusing on the bottom of the cell) remained largely unchanged indeed (17,18), the actin cap disappeared in a majority of Lmna Ϫ/Ϫ cells (Fig. 4 A and C, Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, we investigated the organization of the actin filament network in primary fibroblasts harvested from an Lmna L530P/L530P mouse, a model of accelerated aging (progeria) (17,22,23). We have recently shown that LINC complex proteins are displaced from the nucleus to the ER and cytoplasm in a majority of Lmna L530P/L530P cells (17).…”

Section: Resultsmentioning

confidence: 99%

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A perinuclear actin cap regulates nuclear shape

Khatau¹,

Hale²,

Stewart-Hutchinson

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Defects in nuclear morphology often correlate with the onset of disease, including cancer, progeria, cardiomyopathy, and muscular dystrophy. However, the mechanism by which a cell controls its nuclear shape is unknown. Here, we use adhesive micropatterned surfaces to control the overall shape of fibroblasts and find that the shape of the nucleus is tightly regulated by the underlying cell adhesion geometry. We found that this regulation occurs through a dome-like actin cap that covers the top of the nucleus. This cap is composed of contractile actin filament bundles containing phosphorylated myosin, which form a highly organized, dynamic, and oriented structure in a wide variety of cells. The perinuclear actin cap is specifically disorganized or eliminated by inhibition of actomyosin contractility and rupture of the LINC complexes, which connect the nucleus to the actin cap. The organization of this actin cap and its nuclear shape-determining function are disrupted in cells from mouse models of accelerated aging (progeria) and muscular dystrophy with distorted nuclei caused by alterations of A-type lamins. These results highlight the interplay between cell shape, nuclear shape, and cell adhesion mediated by the perinuclear actin cap.LINC complexes ͉ nucleus I n 1921, Champy and Carleton suggested an apparent correlation between the shape of various types of animal cells and the shape of their respective nuclei (1). Moreover, defects in nuclear shape are routinely used in the lab and in clinical settings as markers of disease and differentiation in human cells and tissues (2). However, remarkably little is known about the factors that determine nuclear morphology in living cells. In particular, the molecular mechanisms that govern the shape of the interphase nucleus are unknown. Here we show that an actin filament structure that forms a cap or dome located above the apical surface of the nucleus tightly controls nuclear shape and identify key associated cytoskeletal regulators of its organization and nuclear shape-determining function. The organization and function of the perinuclear actin cap are deregulated in diseased cells with distorted nuclei. Results and DiscussionTo test the hypothesis of a correlation between the shape of the nucleus and the overall cell shape, mouse embryonic fibroblasts were dispersed on fibronectin (FN)-coated glass substrates. Using morphometric analysis, we found that nuclear shape and cellular shape correlated ( Fig. 1 A and B). Shape factor, defined as 4 A/P 2 (where A and P are the nuclear area and perimeter), approaches 1 for a rounded nucleus and approaches 0 for an elongated nucleus. Elongated cells typically showed an elongated nucleus of low shape factor; rounded cells showed a rounded nucleus of high shape factor (Fig. 1 A). To control cell shape and, therefore, be able to quantify nuclear shape as a function of cell shape, we developed adhesive FN-coated micropatterned stripes of width ranging between 10 and 50 m, which alternated with stripes covered with nonadhesive poly...

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

A perinuclear actin cap regulates nuclear shape

Khatau¹,

Hale²,

Stewart-Hutchinson

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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536

602

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show abstract

“…Indeed, mounting evidence indicates that www.cell-research.com | Cell Research Wenjia Wang et al 1441 npg LINC complexes function in multiple biological processes, including nuclear migration and repositioning, meiotic telomere tethering and chromatin organization, centrosome migration and attachment, nucleokinesis and cellular rigidity homeostasis [1][2][3]. Recently, LINC complexes have been implicated in the regulation of apoptosis [4,5], the maturation and survival of germlines [6], and in the pathology of human diseases linked to mutations of A-type lamins, such as laminopathies and Emery-Dreifuss muscular dystrophy [7][8][9]. During a study of centrosome-related proteins that were affected by erbB transformation, we cloned and identified the SUN domain protein SUN2 [10].…”

Section: Introductionmentioning

confidence: 99%

Structural insights into SUN-KASH complexes across the nuclear envelope

et al. 2012

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Linker of the nucleoskeleton and the cytoskeleton (LINC) complexes are composed of SUN and KASH domaincontaining proteins and bridge the inner and outer membranes of the nuclear envelope. LINC complexes play critical roles in nuclear positioning, cell polarization and cellular stiffness. Previously, we reported the homotrimeric structure of human SUN2. We have now determined the crystal structure of the human SUN2-KASH complex. In the complex structure, the SUN domain homotrimer binds to three independent "hook"-like KASH peptides. The overall conformation of the SUN domain in the complex closely resembles the SUN domain in its apo state. A major conformational change involves the AA'-loop of KASH-bound SUN domain, which rearranges to form a mini β-sheet that interacts with the KASH peptide. The PPPT motif of the KASH domain fits tightly into a hydrophobic pocket on the homotrimeric interface of the SUN domain, which we termed the BI-pocket. Moreover, two adjacent protomers of the SUN domain homotrimer sandwich the KASH domain by hydrophobic interaction and hydrogen bonding. Mutations of these binding sites disrupt or reduce the association between the SUN and KASH domains in vitro. In addition, transfection of wild-type, but not mutant, SUN2 promotes cell migration in Ovcar-3 cells. These results provide a structural model of the LINC complex, which is essential for additional study of the physical and functional coupling between the cytoplasm and the nucleoplasm.

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“…Furthermore, perturbations of the intermediate filament network could alter the positioning of the nucleus in both migrating and immobile astrocytes, suggesting that cytoplasmic intermediate filaments are involved in actin-dependent positioning of the nucleus 20 . Concomitant with these recent discoveries, significant advances have been made in terms of identifying the molecular links between the nuclear envelope and the cytoplasmic filaments [21][22][23][24][25] , and new insights have been gained into the mechanistic maintenance of the nucleus 3,23,24,26,27 . Emerging evidence is now accumulating that cytoplasmic filaments are exploited by cells to govern nuclear morphology and finely tune gene expression in response to cell shape changes.…”

mentioning

confidence: 99%

Spatial coordination between cell and nuclear shape within micropatterned endothelial cells

2012

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Growing evidence suggests that cytoplasmic actin filaments are essential factors in the modulation of nuclear shape and function. However, the mechanistic understanding of the internal orchestration between cell and nuclear shape is still lacking. Here we show that orientation and deformation of the nucleus are regulated by lateral compressive forces driven by tension in central actomyosin fibres. By using a combination of micro-manipulation tools, our study reveals that tension in central stress fibres is gradually generated by anisotropic force contraction dipoles, which expand as the cell elongates and spreads. our findings indicate that large-scale cell shape changes induce a drastic condensation of chromatin and dramatically affect cell proliferation. on the basis of these findings, we propose a simple mechanical model that quantitatively accounts for our experimental data and provides a conceptual framework for the mechanistic coordination between cell and nuclear shape.

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Dysfunctional Connections Between the Nucleus and the Actin and Microtubule Networks in Laminopathic Models

Cited by 185 publications

References 61 publications

A perinuclear actin cap regulates nuclear shape

A perinuclear actin cap regulates nuclear shape

Structural insights into SUN-KASH complexes across the nuclear envelope

Spatial coordination between cell and nuclear shape within micropatterned endothelial cells

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