scholarly journals Aurora A depletion reveals centrosome-independent polarization mechanism in Caenorhabditis elegans

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Kerstin Klinkert ◽  
Nicolas Levernier ◽  
Peter Gross ◽  
Christian Gentili ◽  
Lukas von Tobel ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Symmetry Breaking ◽  
Break Symmetry ◽  
Dependent Manner ◽  
Aurora A Kinase ◽  
Aurora A ◽  
Physical Description ◽  
C Elegans ◽  
Actin Cortex ◽  
Polarization Mechanism

How living systems break symmetry in an organized manner is a fundamental question in biology. In wild-type Caenorhabditis elegans zygotes, symmetry breaking during anterior-posterior axis specification is guided by centrosomes, resulting in anterior-directed cortical flows and a single posterior PAR-2 domain. We uncover that C. elegans zygotes depleted of the Aurora A kinase AIR-1 or lacking centrosomes entirely usually establish two posterior PAR-2 domains, one at each pole. We demonstrate that AIR-1 prevents symmetry breaking early in the cell cycle, whereas centrosomal AIR-1 instructs polarity initiation thereafter. Using triangular microfabricated chambers, we establish that bipolarity of air-1(RNAi) embryos occurs effectively in a cell-shape and curvature-dependent manner. Furthermore, we develop an integrated physical description of symmetry breaking, wherein local PAR-2-dependent weakening of the actin cortex, together with mutual inhibition of anterior and posterior PAR proteins, provides a mechanism for spontaneous symmetry breaking without centrosomes.

scholarly journals Aurora A depletion reveals centrosome-independent polarization mechanism in C.elegans

2018 ◽  
Author(s):  
K. Klinkert ◽  
N. Levernier ◽  
P. Gross ◽  
C. Gentili ◽  
L. von Tobel ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Transgenic Animals ◽  
Break Symmetry ◽  
Dependent Manner ◽  
Aurora A Kinase ◽  
Aurora A ◽  
C Elegans ◽  
Actin Cortex ◽  
Self Organized ◽  
Polarization Mechanism

AbstractHow living systems break symmetry in an organized manner is an important question in biology. In C. elegans zygotes, symmetry breaking normally occurs in the vicinity of centrosomes, resulting in anterior-directed cortical flows and establishment of a single posterior PAR-2 domain. Here, we report that zygotes depleted of the Aurora A kinase AIR-1 or of centrosomes establish two posterior domains, one at each pole. Using transgenic animals and microfabricated triangular chambers, we establish that such bipolarity occurs in a PAR-2- and curvature-dependent manner. Furthermore, we develop an integrated physical model of symmetry breaking, establishing that local PAR-dependent weakening of the actin cortex, together with mutual inhibition of anterior and posterior PAR proteins, provides a mechanism for self-organized PAR polarization without functional centrosomes in C. elegans.One Sentence SummaryWe uncover a novel centrosome-independent mechanism of polarization in C. elegans zygotes

Centrosome Aurora A gradient ensures single polarity axis in C. elegans embryos

2020 ◽  
Vol 48 (3) ◽  
pp. 1243-1253 ◽  
Author(s):  
Sukriti Kapoor ◽  
Sachin Kotak
Keyword(s):  
Symmetry Breaking ◽  
Cell Fate ◽  
Cell Cortex ◽  
Axis Formation ◽  
Aurora A Kinase ◽  
Aurora A ◽  
C Elegans ◽  
Cell Embryo ◽  
Polarity Establishment

Cellular asymmetries are vital for generating cell fate diversity during development and in stem cells. In the newly fertilized Caenorhabditis elegans embryo, centrosomes are responsible for polarity establishment, i.e. anterior–posterior body axis formation. The signal for polarity originates from the centrosomes and is transmitted to the cell cortex, where it disassembles the actomyosin network. This event leads to symmetry breaking and the establishment of distinct domains of evolutionarily conserved PAR proteins. However, the identity of an essential component that localizes to the centrosomes and promotes symmetry breaking was unknown. Recent work has uncovered that the loss of Aurora A kinase (AIR-1 in C. elegans and hereafter referred to as Aurora A) in the one-cell embryo disrupts stereotypical actomyosin-based cortical flows that occur at the time of polarity establishment. This misregulation of actomyosin flow dynamics results in the occurrence of two polarity axes. Notably, the role of Aurora A in ensuring a single polarity axis is independent of its well-established function in centrosome maturation. The mechanism by which Aurora A directs symmetry breaking is likely through direct regulation of Rho-dependent contractility. In this mini-review, we will discuss the unconventional role of Aurora A kinase in polarity establishment in C. elegans embryos and propose a refined model of centrosome-dependent symmetry breaking.

scholarly journals Aurora-A kinase is required for centrosome maturation in Caenorhabditis elegans

2001 ◽  
Vol 155 (7) ◽  
pp. 1109-1116 ◽  
Author(s):  
Eva Hannak ◽  
Matthew Kirkham ◽  
Anthony A. Hyman ◽  
Karen Oegema
Keyword(s):  
Caenorhabditis Elegans ◽  
Fluorescence Intensity ◽  
Maturation Process ◽  
Aurora A Kinase ◽  
Aurora A ◽  
Wild Type ◽  
C Elegans ◽  
Nuclear Envelope Breakdown ◽  
Pericentriolar Material

Centrosomes mature as cells enter mitosis, accumulating γ-tubulin and other pericentriolar material (PCM) components. This occurs concomitant with an increase in the number of centrosomally organized microtubules (MTs). Here, we use RNA-mediated interference (RNAi) to examine the role of the aurora-A kinase, AIR-1, during centrosome maturation in Caenorhabditis elegans. In air-1(RNAi) embryos, centrosomes separate normally, an event that occurs before maturation in C. elegans. After nuclear envelope breakdown, the separated centrosomes collapse together, and spindle assembly fails. In mitotic air-1(RNAi) embryos, centrosomal α-tubulin fluorescence intensity accumulates to only 40% of wild-type levels, suggesting a defect in the maturation process. Consistent with this hypothesis, we find that AIR-1 is required for the increase in centrosomal γ-tubulin and two other PCM components, ZYG-9 and CeGrip, as embryos enter mitosis. Furthermore, the AIR-1–dependent increase in centrosomal γ-tubulin does not require MTs. These results suggest that aurora-A kinases are required to execute a MT-independent pathway for the recruitment of PCM during centrosome maturation.

scholarly journals Mechanochemical Control of Symmetry Breaking in the Caenorhabditis elegans Zygote

2021 ◽  
Vol 8 ◽  
Author(s):  
Wan Jun Gan ◽  
Fumio Motegi
Keyword(s):  
Caenorhabditis Elegans ◽  
Symmetry Breaking ◽  
Actin Cytoskeleton ◽  
Cell Polarity ◽  
Break Symmetry ◽  
Cell Cortex ◽  
Aurora A Kinase ◽  
Advective Flow ◽  
Polar State ◽  
Cellular Components

Cell polarity is the asymmetric organization of cellular components along defined axes. A key requirement for polarization is the ability of the cell to break symmetry and achieve a spatially biased organization. Despite different triggering cues in various systems, symmetry breaking (SB) usually relies on mechanochemical modulation of the actin cytoskeleton, which allows for advected movement and reorganization of cellular components. Here, the mechanisms underlying SB in Caenorhabditis elegans zygote, one of the most popular models to study cell polarity, are reviewed. A zygote initiates SB through the centrosome, which modulates mechanics of the cell cortex to establish advective flow of cortical proteins including the actin cytoskeleton and partitioning defective (PAR) proteins. The chemical signaling underlying centrosomal control of the Aurora A kinase–mediated cascade to convert the organization of the contractile actomyosin network from an apolar to polar state is also discussed.

A Cuticle Collagen Encoded by the lon-3 Gene May Be a Target of TGF-β Signaling in Determining Caenorhabditis elegans Body Shape

Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1631-1639
Author(s):  
Yo Suzuki ◽  
Gail A Morris ◽  
Min Han ◽  
William B Wood
Keyword(s):  
Caenorhabditis Elegans ◽  
Body Shape ◽  
Small Body ◽  
Dependent Manner ◽  
Loss Of Function ◽  
Cellular Mechanisms ◽  
C Elegans ◽  
Gene Expression Analyses ◽  
Dose Dependent

Abstract The signaling pathway initiated by the TGF-β family member DBL-1 in Caenorhabditis elegans controls body shape in a dose-dependent manner. Loss-of-function (lf) mutations in the dbl-1 gene cause a short, small body (Sma phenotype), whereas overexpression of dbl-1 causes a long body (Lon phenotype). To understand the cellular mechanisms underlying these phenotypes, we have isolated suppressors of the Sma phenotype resulting from a dbl-1(lf) mutation. Two of these suppressors are mutations in the lon-3 gene, of which four additional alleles are known. We show that lon-3 encodes a collagen that is a component of the C. elegans cuticle. Genetic and reporter-gene expression analyses suggest that lon-3 is involved in determination of body shape and is post-transcriptionally regulated by the dbl-1 pathway. These results support the possibility that TGF-β signaling controls C. elegans body shape by regulating cuticle composition.

scholarly journals The nucleoporin Nup205/NPP-3 is lost near centrosomes at mitotic onset and can modulate the timing of this process in Caenorhabditis elegans embryos

2012 ◽  
Vol 23 (16) ◽  
pp. 3111-3121 ◽  
Author(s):  
Virginie Hachet ◽  
Coralie Busso ◽  
Mika Toya ◽  
Asako Sugimoto ◽  
Peter Askjaer ◽  
...  
Keyword(s):  
Cell Division ◽  
Rna Interference ◽  
Caenorhabditis Elegans ◽  
Nuclear Envelope ◽  
Aurora A Kinase ◽  
Aurora A ◽  
Time And Space ◽  
Local Loss ◽  
Necessary And Sufficient

Regulation of mitosis in time and space is critical for proper cell division. We conducted an RNA interference–based modifier screen to identify novel regulators of mitosis in Caenorhabditis elegans embryos. Of particular interest, this screen revealed that the Nup205 nucleoporin NPP-3 can negatively modulate the timing of mitotic onset. Furthermore, we discovered that NPP-3 and nucleoporins that are associated with it are lost from the nuclear envelope (NE) in the vicinity of centrosomes at the onset of mitosis. We demonstrate that centrosomes are both necessary and sufficient for NPP-3 local loss, which also requires the activity of the Aurora-A kinase AIR-1. Our findings taken together support a model in which centrosomes and AIR-1 promote timely onset of mitosis by locally removing NPP-3 and associated nucleoporins from the NE.

scholarly journals In the Model Host Caenorhabditis elegans, Sphingosine-1-Phosphate-Mediated Signaling Increases Immunity toward Human Opportunistic Bacteria

2020 ◽  
Vol 21 (21) ◽  
pp. 7813
Author(s):  
Kiho Lee ◽  
Iliana Escobar ◽  
Yeeun Jang ◽  
Wooseong Kim ◽  
Frederick M. Ausubel ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Stress Responses ◽  
Mapk Signaling ◽  
Dependent Manner ◽  
Cellular Functions ◽  
Kinase Gene ◽  
Concentration Dependent Manner ◽  
C Elegans ◽  
Opportunistic Bacteria ◽  
Free Living Nematode

Sphingosine-1-phophate (S1P) is a sphingolipid-derived signaling molecule that controls diverse cellular functions including cell growth, homeostasis, and stress responses. In a variety of metazoans, cytosolic S1P is transported into the extracellular space where it activates S1P receptors in a concentration-dependent manner. In the free-living nematode Caenorhabditis elegans, the spin-2 gene, which encodes a S1P transporter, is activated during Gram-positive or Gram-negative bacterial infection of the intestine. However, the role during infection of spin-2 and three additional genes in the C. elegans genome encoding other putative S1P transporters has not been elucidated. Here, we report an evolutionally conserved function for S1P and a non-canonical role for S1P transporters in the C. elegans immune response to bacterial pathogens. We found that mutations in the sphingosine kinase gene (sphk-1) or in the S1P transporter genes spin-2 or spin-3 decreased nematode survival after infection with Pseudomonas aeruginosa or Enterococcus faecalis. In contrast to spin-2 and spin-3, mutating spin-1 leads to an increase in resistance to P. aeruginosa. Consistent with these results, when wild-type C. elegans were supplemented with extracellular S1P, we found an increase in their lifespan when challenged with P. aeruginosa and E. faecalis. In comparison, spin-2 and spin-3 mutations suppressed the ability of S1P to rescue the worms from pathogen-mediated killing, whereas the spin-1 mutation had no effect on the immune-enhancing activity of S1P. S1P demonstrated no antimicrobial activity toward P. aeruginosa and Escherichia coli and only minimal activity against E. faecalis MMH594 (40 µM). These data suggest that spin-2 and spin-3, on the one hand, and spin-1, on the other hand, transport S1P across cellular membranes in opposite directions. Finally, the immune modulatory effect of S1P was diminished in C. eleganssek-1 and pmk-1 mutants, suggesting that the immunomodulatory effects of S1P are mediated by the p38 MAPK signaling pathway.

scholarly journals Embryonic extracts derived from the nematode Caenorhabditis elegans remove uracil from DNA by the sequential action of uracil-DNA glycosylase and AP (apurinic/apyrimidinic) endonuclease

2002 ◽  
Vol 365 (2) ◽  
pp. 547-553 ◽  
Author(s):  
Andrea SHATILLA ◽  
Dindial RAMOTAR
Keyword(s):  
Caenorhabditis Elegans ◽  
Excision Repair ◽  
Specific Inhibitor ◽  
Dna Glycosylase ◽  
Dependent Manner ◽  
Nematode Caenorhabditis Elegans ◽  
Uracil Dna Glycosylase ◽  
Ap Endonuclease ◽  
C Elegans ◽  
Ap Site

DNA bases continuously undergo modifications in response to endogenous reactions such as oxidation, alkylation or deamination. The modified bases are primarily removed by DNA glycosylases, which cleave the N-glycosylic bond linking the base to the sugar, to generate an apurinic/apyrimidinic (AP) site, and this latter lesion is highly mutagenic. Previously, no study has demonstrated the processing of these lesions in the nematode Caenorhabditis elegans. Herein, we report the existence of uracil-DNA glycosylase and AP endonuclease activities in extracts derived from embryos of C. elegans. These enzyme activities were monitored using a defined 5′-end 32P-labelled 42-bp synthetic oligonucleotide substrate bearing a single uracil residue opposite guanine at position 21. The embryonic extract rapidly cleaved the substrate in a time-dependent manner to produce a 20-mer product. The extract did not excise adenine or thymine opposite guanine, although uracil opposite either adenine or thymine was processed. Addition of the highly specific inhibitor of uracil-DNA glycosylase produced by Bacillus subtilis to the extract prevented the formation of the 20-mer product, indicating that removal of uracil is catalysed by uracil-DNA glycosylase. The data suggest that the 20-mer product was generated by a sequential reaction, i.e., removal of the uracil base followed by 5′-cleavage of the AP site. Further analysis revealed that product formation was dependent upon the presence of Mg2+, suggesting that cleavage of the AP site, following uracil excision, is carried out by a Mg2+-dependent AP endonuclease. It would appear that these activities correspond to the first two steps of a putative base-excision-repair pathway in C. elegans.

scholarly journals Memory of recent oxygen experience switches pheromone valence in Caenorhabditis elegans

2017 ◽  
Vol 114 (16) ◽  
pp. 4195-4200 ◽  
Author(s):  
Lorenz A. Fenk ◽  
Mario de Bono
Keyword(s):  
Caenorhabditis Elegans ◽  
Behavioral Plasticity ◽  
Prior Experience ◽  
Sensory Information ◽  
Dependent Manner ◽  
Oxygen Environment ◽  
C Elegans ◽  
Sustained Change ◽  
Context Dependent ◽  
Physiological Correlate

Animals adjust their behavioral priorities according to momentary needs and prior experience. We show that Caenorhabditis elegans changes how it processes sensory information according to the oxygen environment it experienced recently. C. elegans acclimated to 7% O2 are aroused by CO2 and repelled by pheromones that attract animals acclimated to 21% O2. This behavioral plasticity arises from prolonged activity differences in a circuit that continuously signals O2 levels. A sustained change in the activity of O2-sensing neurons reprograms the properties of their postsynaptic partners, the RMG hub interneurons. RMG is gap-junctionally coupled to the ASK and ADL pheromone sensors that respectively drive pheromone attraction and repulsion. Prior O2 experience has opposite effects on the pheromone responsiveness of these neurons. These circuit changes provide a physiological correlate of altered pheromone valence. Our results suggest C. elegans stores a memory of recent O2 experience in the RMG circuit and illustrate how a circuit is flexibly sculpted to guide behavioral decisions in a context-dependent manner.

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