PI(4,5)P2forms dynamic cortical structures and directs actin distribution and cell polarity in C. elegans embryos

AbstractAsymmetric division is crucial for embryonic development and stem cell lineages. In the one-cellC. elegansembryo, a contractile cortical actomyosin network contributes to anterior-posterior (A-P) polarity and asymmetric division by segregating PAR proteins to discrete cortical domains. Here, we discovered that the plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) forms dynamic structures inC. eleganszygotes, distributing in a polarized and PAR-dependent manner along the A-P axis. PIP2cortical structures overlap with F-actin and coincide with the actin regulators RHO-1, CDC-42 and ECT-2. Particle image velocimetry analysis revealed that PIP2and F-actin cortical movements are coupled, with PIP2structures moving slightly ahead. Importantly, we established that PIP2cortical structures form in an actin-dependent manner and, conversely, that decreasing or increasing the level of PIP2results in severe F-actin disorganization, revealing the interdependence between these components. Furthermore, we uncovered that PIP2regulates the sizing of PAR cortical domains. Overall, our work establishes for the first time that a lipid membrane component, PIP2, is a critical modulator of actin organization and cell polarity inC. elegansembryos.Summary statementPI(4,5)P2is distributed in dynamic cortical structures and regulates asymmetric division by controlling actin organization and cell polarity in the one-cellC. elegansembryo.

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Compartmentalization of the endoplasmic reticulum in the early C. elegans embryos

The Journal of Cell Biology ◽

10.1083/jcb.201601047 ◽

2016 ◽

Vol 214 (6) ◽

pp. 665-676 ◽

Cited By ~ 8

Author(s):

Zuo Yen Lee ◽

Manoël Prouteau ◽

Monica Gotta ◽

Yves Barral

Keyword(s):

Endoplasmic Reticulum ◽

Cleavage Plane ◽

Morphological Transition ◽

Dependent Manner ◽

Cell Lineages ◽

C Elegans ◽

Nuclear Envelope Breakdown ◽

The One ◽

Fate Determinants ◽

Er Membrane

The one-cell Caenorhabditis elegans embryo is polarized to partition fate determinants between the cell lineages generated during its first division. Using fluorescence loss in photobleaching, we find that the endoplasmic reticulum (ER) of the C. elegans embryo is physically continuous throughout the cell, but its membrane is compartmentalized shortly before nuclear envelope breakdown into an anterior and a posterior domain, indicating that a diffusion barrier forms in the ER membrane between these two domains. Using mutants with disorganized ER, we show that ER compartmentalization is independent of the morphological transition that the ER undergoes in mitosis. In contrast, compartmentalization takes place at the position of the future cleavage plane in a par-3–dependent manner. Together, our data indicate that the ER membrane is compartmentalized in cells as diverse as budding yeast, mouse neural stem cells, and the early C. elegans embryo.

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Testicular membrane lipid damage by complex mixture of leachate from municipal battery recycling site as indication of idiopathic male infertility in rat

Interdisciplinary Toxicology ◽

10.2478/intox-2013-0028 ◽

2013 ◽

Vol 6 (4) ◽

pp. 192-197 ◽

Cited By ~ 11

Author(s):

Jacob K. Akintunde ◽

Ganiyu Oboh ◽

Akintunde A. Akindahunsi

Keyword(s):

Male Infertility ◽

Lipid Membrane ◽

Complex Mixture ◽

Membrane Lipid ◽

Metal Exposure ◽

Dependent Manner ◽

Mixed Metal ◽

Lipid Damage ◽

Battery Recycling

ABSTRACT Leachate from a municipal battery recycling site is a potent source of mixed-metal released into the environment. The present study investigated the degree at which mixed-metal exposure to the municipal auto-battery leachate (MABL) and to the Elewi Odo municipal auto-battery recycling site leachate (EOMABRL) affected the lipid membrane of the testes in in vitro experiment. The results showed elevated level of mixed-metals over the permissible levels in drinking water, as recommended by regulatory authorities. In the leachate samples, the levels of malondialdehyde (MDA), a biomarker of lipid damage, was significantly (p<0.05) increased in rat testes in a dose-dependent manner. MDA induced by the municipal auto-battery leachate (MABL) was significantly (p<0.05) higher than the leachate from Elewi Odo municipal auto-battery recycling site (EOMABRL). The testicular lipid membrane capacity was compromised following treatment with leachate from the municipal battery recycling site, implicating mixed-metal exposure as the causative agent of testicular damage and male infertility.

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Defects in Structural Integrity of Ergosterol and the Cdc50p-Drs2p Putative Phospholipid Translocase Cause Accumulation of Endocytic Membranes, onto Which Actin Patches Are Assembled in Yeast

Molecular Biology of the Cell ◽

10.1091/mbc.e05-05-0452 ◽

2005 ◽

Vol 16 (12) ◽

pp. 5592-5609 ◽

Cited By ~ 35

Author(s):

Takuma Kishimoto ◽

Takaharu Yamamoto ◽

Kazuma Tanaka

Keyword(s):

Lipid Bilayers ◽

Cell Polarity ◽

Structural Integrity ◽

Membrane Lipid ◽

Actin Organization ◽

Ergosterol Synthesis ◽

Simultaneous Loss ◽

Synthetically Lethal ◽

Golgi Network ◽

And Control

Specific changes in membrane lipid composition are implicated in actin cytoskeletal organization, vesicle formation, and control of cell polarity. Cdc50p, a membrane protein in the endosomal/trans-Golgi network compartments, is a noncatalytic subunit of Drs2p, which is implicated in translocation of phospholipids across lipid bilayers. We found that the cdc50Δ mutation is synthetically lethal with mutations affecting the late steps of ergosterol synthesis (erg2 to erg6). Defects in cell polarity and actin organization were observed in the cdc50Δ erg3Δ mutant. In particular, actin patches, which are normally found at cortical sites, were assembled intracellularly along with their assembly factors, including Las17p, Abp1p, and Sla2p. The exocytic SNARE Snc1p, which is recycled by an endocytic route, was also intracellularly accumulated, and inhibition of endocytic internalization suppressed the cytoplasmic accumulation of both Las17p and Snc1p. Simultaneous loss of both phospholipid asymmetry and sterol structural integrity could lead to accumulation of endocytic intermediates capable of initiating assembly of actin patches in the cytoplasm.

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Cell polarity–dependent centrosome separation in the C. elegans embryo

The Journal of Cell Biology ◽

10.1083/jcb.201902109 ◽

2019 ◽

Vol 218 (12) ◽

pp. 4112-4126

Author(s):

Alexandra Bondaz ◽

Luca Cirillo ◽

Patrick Meraldi ◽

Monica Gotta

Keyword(s):

Cell Polarity ◽

Cell Biology ◽

Dependent Manner ◽

Animal Cells ◽

Cell Stage ◽

C Elegans ◽

Mitotic Kinase ◽

Centrosome Separation ◽

A Cell ◽

Cortical Localization

In animal cells, faithful chromosome segregation depends on the assembly of a bipolar spindle driven by the timely separation of the two centrosomes. Here we took advantage of the highly stereotypical cell divisions in Caenorhabditis elegans embryos to identify new regulators of centrosome separation. We find that at the two-cell stage, the somatic AB cell initiates centrosome separation later than the germline P1 cell. This difference is strongly exacerbated by the depletion of the kinesin-13 KLP-7/MCAK, resulting in incomplete centrosome separation at NEBD in AB but not P1. Our genetic and cell biology data indicate that this phenotype depends on cell polarity via the enrichment in AB of the mitotic kinase PLK-1, which itself limits the cortical localization of the dynein-binding NuMA orthologue LIN-5. We postulate that the timely separation of centrosomes is regulated in a cell type–dependent manner.

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The kinases PIG-1 and PAR-1 act in redundant pathways to regulate asymmetric division in the EMS blastomere of C. elegans

10.1101/191866 ◽

2017 ◽

Author(s):

Malgorzata J. Liro ◽

Diane G. Morton ◽

Lesilee S. Rose

Keyword(s):

Wnt Pathway ◽

Asymmetric Division ◽

Spindle Orientation ◽

Cell Stage ◽

Spindle Positioning ◽

C Elegans ◽

Stage Embryo ◽

Cell Embryo ◽

The One

AbstractThe PAR-1 kinase of C. elegans is localized to the posterior of the one-cell embryo and its mutations affect asymmetric spindle placement and partitioning of cytoplasmic components in the first cell cycle. However, unlike mutations in the posteriorly localized PAR-2 protein, par-1 mutations do not cause failure to restrict the anterior PAR polarity complex. Further, it has been difficult to examine the role of PAR-1 in subsequent divisions due to the early defects in par-1 mutant embryos. Here we show that the PIG-1 kinase acts redundantly with PAR-1 to restrict the anterior PAR-3 protein for polarity maintenance in the one-cell embryo. By using a weak allele of par-1 that exhibits enhanced lethality when combined with a pig-1 mutation we have further explored roles for these genes in subsequent divisions. We find that both PIG-1 and PAR-1 regulate spindle orientation in the EMS blastomere of the four-cell stage embryo to ensure that it undergoes an asymmetric division. In this cell, PIG-1 and PAR-1 act in parallel pathways for spindle positioning, PIG-1 in the MES-1/SRC-1 pathway and PAR-1 in the Wnt pathway.

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The Transforming Rho Family GTPase Wrch-1 Disrupts Epithelial Cell Tight Junctions and Epithelial Morphogenesis

Molecular and Cellular Biology ◽

10.1128/mcb.00336-08 ◽

2008 ◽

Vol 29 (4) ◽

pp. 1035-1049 ◽

Cited By ~ 36

Author(s):

Donita C. Brady ◽

Jamie K. Alan ◽

James P. Madigan ◽

Alan S. Fanning ◽

Adrienne D. Cox

Keyword(s):

Epithelial Cell ◽

Cell Polarity ◽

Rho Gtpase ◽

Mdck Cells ◽

3D Culture ◽

Cell Polarization ◽

Epithelial Morphogenesis ◽

Detectable Effect ◽

Dependent Manner ◽

Actin Organization

ABSTRACT Wrch-1, an atypical and transforming Rho GTPase, regulates cellular activities including proliferation and actin organization, but its functions and effectors remain poorly characterized. We show here that Wrch-1 distributes along the apical and basolateral membranes in MDCK cells and binds the cell polarity protein Par6 in a GTP-dependent manner. Activated Wrch-1 negatively regulates the kinetics of tight junction (TJ) assembly during epithelial cell polarization but has no detectable effect on overall cell polarity in confluent monolayers. It also causes a dramatic cytoskeletal reorganization and multilayering in cells grown in two-dimensional culture and disrupts cystogenesis of cells grown in three-dimensional (3D) culture. Similarly, short hairpin RNA-mediated knockdown of Wrch-1 perturbs cystogenesis in 3D culture, suggesting that tight regulation of Wrch-1 activity is necessary for normal epithelial morphogenesis. A weakly transforming effector domain mutant of activated Wrch-1 that inhibits Par6 binding abrogates the ability of Wrch-1 to disrupt TJ formation, actin organization, and epithelial morphogenesis. We hypothesize that Wrch-1-induced morphological and growth transformation may occur in part through Par6-mediated disruption of TJs and actin organization.

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