scholarly journals Myosin concentration underlies cell size–dependent scalability of actomyosin ring constriction

2011 ◽  
Vol 195 (5) ◽  
pp. 799-813 ◽  
Author(s):  
Meredith E.K. Calvert ◽  
Graham D. Wright ◽  
Fong Yew Leong ◽  
Keng-Hwee Chiam ◽  
Yinxiao Chen ◽  
...  
Keyword(s):  
Filamentous Fungus ◽  
Mechanical Characteristics ◽  
Cell Types ◽  
Contractile Ring ◽  
C Elegans ◽  
Size Dependent ◽  
Wide Range ◽  
Similar Mode ◽  
Ring Constriction ◽  
Myosin Motors

In eukaryotes, cytokinesis is accomplished by an actomyosin-based contractile ring. Although in Caenorhabditis elegans embryos larger cells divide at a faster rate than smaller cells, it remains unknown whether a similar mode of scalability operates in other cells. We investigated cytokinesis in the filamentous fungus Neurospora crassa, which exhibits a wide range of hyphal circumferences. We found that N. crassa cells divide using an actomyosin ring and larger rings constricted faster than smaller rings. However, unlike in C. elegans, the total amount of myosin remained constant throughout constriction, and there was a size-dependent increase in the starting concentration of myosin in the ring. We predict that the increased number of ring-associated myosin motors in larger rings leads to the increased constriction rate. Accordingly, reduction or inhibition of ring-associated myosin slows down the rate of constriction. Because the mechanical characteristics of contractile rings are conserved, we predict that these findings will be relevant to actomyosin ring constriction in other cell types.

scholarly journals Kinesin-6 regulates cell-size-dependent spindle elongation velocity to keep mitosis duration constant in fission yeast

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Lara Katharina Krüger ◽  
Jérémie-Luc Sanchez ◽  
Anne Paoletti ◽  
Phong Thanh Tran
Keyword(s):  
Fission Yeast ◽  
Cell Size ◽  
Temporal Regulation ◽  
C Elegans ◽  
Size Dependent ◽  
Affect Cell Viability ◽  
Wide Range ◽  
Speed Up ◽  
Spindle Elongation ◽  
Anaphase B

The length of the mitotic spindle scales with cell size in a wide range of organisms during embryonic development. Interestingly, in C. elegans embryos, this goes along with temporal regulation: larger cells speed up spindle assembly and elongation. We demonstrate that, similarly in fission yeast, spindle length and spindle dynamics adjust to cell size, which allows to keep mitosis duration constant. Since prolongation of mitosis was shown to affect cell viability, this may resemble a mechanism to regulate mitosis duration. We further reveal how the velocity of spindle elongation is regulated: coupled to cell size, the amount of kinesin-6 Klp9 molecules increases, resulting in an acceleration of spindle elongation in anaphase B. In addition, the number of Klp9 binding sites to microtubules increases overproportionally to Klp9 molecules, suggesting that molecular crowding inversely correlates to cell size and might have an impact on spindle elongation velocity control.

scholarly journals Forkhead transcription factor FKH-8 is a master regulator of primary cilia in C. elegans

2021 ◽  
Author(s):  
Rebeca Brocal-Ruiz ◽  
Ainara Esteve-Serrano ◽  
Carlos Mora-Martinez ◽  
Peter Swoboda ◽  
Juan Tena ◽  
...  
Keyword(s):  
Primary Cilia ◽  
Genetic Diseases ◽  
Ciliated Cell ◽  
Cell Types ◽  
Forkhead Transcription Factor ◽  
Master Regulator ◽  
C Elegans ◽  
Direct Activation ◽  
Wide Range ◽  
Motile Cilia

SUMMARYCilia, either motile or non-motile (a.k.a primary or sensory), are complex evolutionary conserved eukaryotic structures composed of hundreds of proteins required for their assembly, structure and function that are collectively known as the ciliome. Ciliome mutations underlie a group of pleiotropic genetic diseases known as ciliopathies. Proper cilium function requires the tight coregulation of ciliome gene transcription, which is only fragmentarily understood. RFX transcription factors (TF) have an evolutionarily conserved role in the direct activation of ciliome genes both in motile and non-motile cilia cell types. In vertebrates, FoxJ1 and FoxN4 Forkhead (FKH) TFs work with RFX in the direct activation of ciliome genes, exclusively in motile cilia cell-types. No additional TFs have been described to act together with RFX in primary cilia cell-types in any organism. Here we describe FKH-8, a FKH TF, as master regulator of the primary ciliome in Caenorhabditis elegans. fkh-8 is expressed in all ciliated neurons in C. elegans, binds the regulatory regions of ciliome genes, regulates ciliome gene expression, cilium morphology and a wide range of behaviours mediated by sensory cilia. Importantly, we find FKH-8 function can be replaced by mouse FOXJ1 and FOXN4 but not by members of other mouse FKH subfamilies. In conclusion, our results show that RFX and FKH TF families act as master regulators of ciliogenesis also in sensory ciliated cell types and suggest that this regulatory logic could be an ancient trait predating functional cilia sub-specialization.

scholarly journals Diverse mechanisms regulate contractile ring assembly for cytokinesis in the two-cell C. elegans embryo

2022 ◽  
Author(s):  
Imge Ozugergin ◽  
Karina Mastronardi ◽  
Chris Law ◽  
Alisa Piekny
Keyword(s):  
Cell Types ◽  
Somatic Tissue ◽  
Ring Closure ◽  
Contractile Ring ◽  
C Elegans ◽  
Daughter Cells ◽  
The Core ◽  
Ring Assembly ◽  
Different Cell Types ◽  
Ring Position

Cytokinesis occurs at the end of mitosis due to the ingression of a contractile ring that cleaves the daughter cells. The core machinery regulating this crucial process is conserved among metazoans. Multiple pathways control ring assembly, but their contribution in different cell types is not known. We found that in the C. elegans embryo, AB and P1 cells fated to be somatic tissue and germline, respectively, have different cytokinesis kinetics supported by distinct myosin levels and organization. Through perturbation of RhoA or polarity regulators and the generation of tetraploid strains, we found that ring assembly is controlled by multiple fate-dependent factors that include myosin-levels, and mechanisms that respond to cell size. Active Ran coordinates ring position with the segregating chromatids in HeLa cells by forming an inverse gradient with importins that control the cortical recruitment of anillin. We found that the Ran pathway regulates anillin in AB cells, but functions differently in P1 cells. We propose that ring assembly delays in P1 cells caused by low myosin and Ran signaling coordinate the timing of ring closure with their somatic neighbours.

scholarly journals The Ran pathway uniquely regulates cytokinesis in cells with different fates in the early C. elegans embryo

2021 ◽  
Author(s):  
Imge Ozugergin ◽  
Karina Mastronardi ◽  
Chris Law ◽  
Alisa Piekny
Keyword(s):  
Cell Fate ◽  
Cell Types ◽  
Contractile Ring ◽  
C Elegans ◽  
Multiple Parameters ◽  
Daughter Cells ◽  
The Core ◽  
Cortical Patterning ◽  
Different Cell Types ◽  
In Cells

ABSTRACTCytokinesis occurs at the end of mitosis and occurs due to the ingression of a contractile ring that cleaves the daughter cells. This process is tightly controlled to prevent cell fate changes or aneuploidy, and the core machinery is highly conserved among metazoans. Multiple mechanisms regulate cytokinesis, but their requirement in different cell types is not known. Here, we show that differently fated AB and P1 cells in the early C. elegans embryo have unique cytokinesis kinetics supported by distinct levels and cortical patterning of myosin. Through perturbation of polarity regulators and the generation of stable tetraploid strains, we demonstrate that these differences depend on both cell fate and size. Additionally, these parameters could influence the Ran pathway, which coordinates the contractile ring with chromatin position, and controls cytokinesis differently in AB and P1 cells. Our findings demonstrate the need to consider multiple parameters when modeling ring kinetics.

scholarly journals Distinct gating mechanism of SOC channel involving STIM–Orai coupling and an intramolecular interaction of Orai in Caenorhabditis elegans

2018 ◽  
Vol 115 (20) ◽  
pp. E4623-E4632 ◽  
Author(s):  
Kyu Min Kim ◽  
Tharaka Wijerathne ◽  
Jin-Hoe Hur ◽  
Uk Jung Kang ◽  
Ihn Hyeong Kim ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Intramolecular Interaction ◽  
Interaction Mechanism ◽  
Cell Types ◽  
C Elegans ◽  
Gating Mechanism ◽  
Wide Range ◽  
Store Operated Calcium Entry ◽  
Cellular Compartments ◽  
Orai Channels

Store-operated calcium entry (SOCE), an important mechanism of Ca2+ signaling in a wide range of cell types, is mediated by stromal interaction molecule (STIM), which senses the depletion of endoplasmic reticulum Ca2+ stores and binds and activates Orai channels in the plasma membrane. This inside-out mechanism of Ca2+ signaling raises an interesting question about the evolution of SOCE: How did these two proteins existing in different cellular compartments evolve to interact with each other? We investigated the gating mechanism of Caenorhabditis elegans Orai channels. Our analysis revealed a mechanism of Orai gating by STIM binding to the intracellular 2–3 loop of Orai in C. elegans that is radically different from Orai gating by STIM binding to the N and C termini of Orai in mammals. In addition, we found that the conserved hydrophobic amino acids in the 2–3 loop of Orai1 are important for the oligomerization and gating of channels and are regulated via an intramolecular interaction mechanism mediated by the N and C termini of Orai1. This study identifies a previously unknown SOCE mechanism in C. elegans and suggests that, while the STIM–Orai interaction is conserved between invertebrates and mammals, the gating mechanism for Orai channels differs considerably.

Patterns in diversity and composition of the microbenthos of subarctic intertidal beaches with different morphodynamics

2020 ◽  
Vol 648 ◽  
pp. 19-38
Author(s):  
AI Azovsky ◽  
YA Mazei ◽  
MA Saburova ◽  
PV Sapozhnikov
Keyword(s):  
Species Abundance ◽  
Abundance Ratio ◽  
Wave Action ◽  
Coarse Grained ◽  
Sediment Properties ◽  
Β Diversity ◽  
Α Diversity ◽  
Wide Range ◽  
Similar Mode ◽  
Abundance And Diversity

Diversity and composition of benthic diatom algae and ciliates were studied at several beaches along the White and Barents seas: from highly exposed, reflective beaches with coarse-grained sands to sheltered, dissipative silty-sandy flats. For diatoms, the epipelic to epipsammic species abundance ratio was significantly correlated with the beach index and mean particle size, while neither α-diversity measures nor mean cell length were related to beach properties. In contrast, most of the characteristics of ciliate assemblages (diversity, total abundance and biomass, mean individual weight and percentage of karyorelictids) demonstrated a strong correlation to beach properties, remaining low at exposed beaches but increasing sharply in more sheltered conditions. β-diversity did not correlate with beach properties for either diatoms or ciliates. We suggest that wave action and sediment properties are the main drivers controlling the diversity and composition of the intertidal microbenthos. Diatoms and ciliates, however, demonstrated divergent response to these factors. Epipelic and epipsammic diatoms exhibited 2 different strategies to adapt to their environments and therefore were complementarily distributed along the environmental gradient and compensated for each other in diversity. Most ciliates demonstrated a similar mode of habitat selection but differed in their degree of tolerance. Euryporal (including mesoporal) species were relatively tolerant to wave action and therefore occurred under a wide range of beach conditions, though their abundance and diversity were highest in fine, relatively stable sediments on sheltered beaches, whereas the specific interstitial (i.e. genuine microporal) species were mostly restricted to only these habitats.

Solvent-Ligand Interactions in Colloidal Nanocrystals

2018 ◽  
Author(s):  
Jonathan De Roo ◽  
Nuri Yazdani ◽  
Emile Drijvers ◽  
Alessandro Lauria ◽  
Jorick Maes ◽  
...  
Keyword(s):  
Direct Method ◽  
Line Broadening ◽  
H Nmr ◽  
Size Dependent ◽  
Line Shape Analysis ◽  
Wide Range ◽  
Nanocrystal Synthesis ◽  
Ligand Interactions ◽  
Indispensable Tool ◽  
Theoretical Evidence

<p>Although solvent-ligand interactions play a major role in nanocrystal synthesis, dispersion formulation and assembly, there is currently no direct method to study this. Here we examine the broadening of <sup>1</sup>H NMR resonances associated with bound ligands, and turn this poorly understood descriptor into a tool to assess solvent-ligand interactions. We show that the line broadening has both a homogeneous and a heterogeneous component. The former is nanocrystal-size dependent and the latter results from solvent-ligand interactions. Our model is supported by experimental and theoretical evidence that correlates broad NMR lines with poor ligand solvation. This correlation is found across a wide range of solvents, extending from water to hexane, for both hydrophobic and hydrophilic ligand types, and for a multitude of oxide, sulfide and selenide nanocrystals. Our findings thus put forward NMR line shape analysis as an indispensable tool to form, investigate and manipulate nanocolloids.</p>

A Deficiency Screen for Zygotic Loci Required for Establishment and Patterning of the Epidermis in Caenorhabditis elegans

Genetics ◽  
1997 ◽  
Vol 146 (1) ◽  
pp. 185-206 ◽  
Author(s):  
Rebecca M Terns ◽  
Peggy Kroll-Conner ◽  
Jiangwen Zhu ◽  
Sooyoun Chung ◽  
Joel H Rothman
Keyword(s):  
Caenorhabditis Elegans ◽  
Cell Types ◽  
Epidermal Cells ◽  
Epidermal Differentiation ◽  
Apparent Effect ◽  
Internal Organs ◽  
C Elegans ◽  
Seam Cell ◽  
Genomic Regions ◽  
Caenorhabditis Elegans Genome

To identify genomic regions required for establishment and patterning of the epidermis, we screened 58 deficiencies that collectively delete at least ∼67% of the Caenorhabditis elegans genome. The epidermal pattern of deficiency homozygous embryos was analyzed by examining expression of a marker specific for one of the three major epidermal cell types, the seam cells. The organization of the epidermis and internal organs was also analyzed using a monoclonal antibody specific for epithelial adherens junctions. While seven deficiencies had no apparent effect on seam cell production, 21 were found to result in subnormal, and five in excess numbers of these cells. An additional 23 deficiencies blocked expression of the seam cell marker, in some cases without preventing cell proliferation. Two deficiencies result in multinucleate seam cells. Deficiencies were also identified that result in subnormal numbers of epidermal cells, hyperfusion of epidermal cells into a large syncytium, or aberrant epidermal differentiation. Finally, analysis of internal epithelia revealed deficiencies that cause defects in formation of internal organs, including circularization of the intestine and bifurcation of the pharynx lumen. This study reveals that many regions of the C. elegans genome are required zygotically for patterning of the epidermis and other epithelia.

scholarly journals Isolation and Characterization of Strain Exiguobacterium sp. KRL4, a Producer of Bioactive Secondary Metabolites from a Tibetan Glacier

2021 ◽  
Vol 9 (5) ◽  
pp. 890
Author(s):  
Pietro Tedesco ◽  
Fortunato Palma Esposito ◽  
Antonio Masino ◽  
Giovanni Andrea Vitale ◽  
Emiliana Tortorella ◽  
...  
Keyword(s):  
Phenotypic Analysis ◽  
Biological Assays ◽  
C Elegans ◽  
Isolation And Characterization ◽  
Wide Range ◽  
Protein Encoding ◽  
Nematocidal Activity ◽  
Extremophilic Microorganisms ◽  
Unique Source

Extremophilic microorganisms represent a unique source of novel natural products. Among them, cold adapted bacteria and particularly alpine microorganisms are still underexplored. Here, we describe the isolation and characterization of a novel Gram-positive, aerobic rod-shaped alpine bacterium (KRL4), isolated from sediments from the Karuola glacier in Tibet, China. Complete phenotypic analysis was performed revealing the great adaptability of the strain to a wide range of temperatures (5–40 °C), pHs (5.5–8.5), and salinities (0–15% w/v NaCl). Genome sequencing identified KRL4 as a member of the placeholder genus Exiguobacterium_A and annotation revealed that only half of the protein-encoding genes (1522 of 3079) could be assigned a putative function. An analysis of the secondary metabolite clusters revealed the presence of two uncharacterized phytoene synthase containing pathways and a novel siderophore pathway. Biological assays confirmed that the strain produces molecules with antioxidant and siderophore activities. Furthermore, intracellular extracts showed nematocidal activity towards C. elegans, suggesting that strain KRL4 is a source of anthelmintic compounds.

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