scholarly journals Sequential accumulation of dynein and its regulatory proteins at the spindle region in the Caenorhabditis elegans embryo

2021 ◽  
Author(s):  
Takayuki Torisawa ◽  
Akatsuki Kimura
Keyword(s):  
Caenorhabditis Elegans ◽  
Cytoplasmic Dynein ◽  
Early Embryo ◽  
Regulatory Proteins ◽  
Cellular Regulation ◽  
Cellular Processes ◽  
Nuclear Envelope Breakdown ◽  
Spatiotemporal Localization ◽  
Region Ii

Cytoplasmic dynein is responsible for various cellular processes during the cell cycle. The mechanism by which its activity is regulated spatially and temporarily inside the cell remains elusive. There are various regulatory proteins of dynein, including dynactin, NDEL1/NUD-2, and LIS1. Characterizing the spatiotemporal localization of regulatory proteins in vivo will aid understanding of the cellular regulation of dynein. Here, we focused on spindle formation in the Caenorhabditis elegans early embryo, wherein dynein and its regulatory proteins translocated from the cytoplasm to the spindle region upon nuclear envelope breakdown (NEBD). We found that (i) a limited set of dynein regulatory proteins accumulated in the spindle region, (ii) the spatial localization patterns were distinct among the regulators, and (iii) the regulatory proteins did not accumulate in the spindle region simultaneously but sequentially. Furthermore, the accumulation of NUD-2 was unique among the regulators. NUD-2 started to accumulate before NEBD (pre-NEBD accumulation), and exhibited the highest enrichment compared to the cytoplasmic concentration. Using a protein injection approach, we revealed that the C-terminal helix of NUD-2 was responsible for pre-NEBD accumulation. These findings suggest a fine temporal control of the subcellular localization of regulatory proteins.

scholarly journals Intracellular organelles mediate cytoplasmic pulling force for centrosome centration in the Caenorhabditis elegans early embryo

2010 ◽  
Vol 108 (1) ◽  
pp. 137-142 ◽  
Author(s):  
Kenji Kimura ◽  
Akatsuki Kimura
Keyword(s):  
Caenorhabditis Elegans ◽  
Mammalian Cells ◽  
Cytoplasmic Dynein ◽  
Early Embryo ◽  
Organelle Transport ◽  
Animal Cells ◽  
C Elegans ◽  
Cell Functions ◽  
Intracellular Organelles ◽  
Pulling Force

The centrosome is generally maintained at the center of the cell. In animal cells, centrosome centration is powered by the pulling force of microtubules, which is dependent on cytoplasmic dynein. However, it is unclear how dynein brings the centrosome to the cell center, i.e., which structure inside the cell functions as a substrate to anchor dynein. Here, we provide evidence that a population of dynein, which is located on intracellular organelles and is responsible for organelle transport toward the centrosome, generates the force required for centrosome centration in Caenorhabditis elegans embryos. By using the database of full-genome RNAi in C. elegans, we identified dyrb-1, a dynein light chain subunit, as a potential subunit involved in dynein anchoring for centrosome centration. DYRB-1 is required for organelle movement toward the minus end of the microtubules. The temporal correlation between centrosome centration and the net movement of organelle transport was found to be significant. Centrosome centration was impaired when Rab7 and RILP, which mediate the association between organelles and dynein in mammalian cells, were knocked down. These results indicate that minus end-directed transport of intracellular organelles along the microtubules is required for centrosome centration in C. elegans embryos. On the basis of this finding, we propose a model in which the reaction forces of organelle transport generated along microtubules act as a driving force that pulls the centrosomes toward the cell center. This is the first model, to our knowledge, providing a mechanical basis for cytoplasmic pulling force for centrosome centration.

Centrosome dynamics in early embryos of Caenorhabditis elegans

1998 ◽  
Vol 111 (20) ◽  
pp. 3027-3033 ◽  
Author(s):  
H.H. Keating ◽  
J.G. White
Keyword(s):  
Caenorhabditis Elegans ◽  
Imaging Techniques ◽  
Early Embryo ◽  
Developmental Potential ◽  
Centrosome Separation ◽  
Early Embryos ◽  
Cell Embryo ◽  
Multiple Interactions

The early Caenorhabditis elegans embryo divides with a stereotyped pattern of cleavages to produce cells that vary in developmental potential. Differences in cleavage plane orientation arise between the anterior and posterior cells of the 2-cell embryo as a result of asymmetries in centrosome positioning. Mechanisms that position centrosomes are thought to involve interactions between microtubules and the cortex, however, these mechanisms remain poorly defined. Interestingly, in the early embryo the shape of the centrosome predicts its subsequent movement. We have used rhodamine-tubulin and live imaging techniques to study the development of asymmetries in centrosome morphology and positioning. In contrast to studies using fixed embryos, our images provide a detailed characterization of the dynamics of centrosome flattening. In addition, our observations of centrosome behavior in vivo challenge previous assumptions regarding centrosome separation by illustrating that centrosome flattening and daughter centrosome separation are distinct processes, and by revealing that nascent daughter centrosomes may become separated from the nucleus. Finally, we provide evidence that the midbody specifies a region of the cortex that directs rotational alignment of the centrosome-nucleus complex and that the process is likely to involve multiple interactions between microtubules and the cortex; the process of alignment involves oscillations and overshoots, suggesting a multiplicity of cortical sites that interact with microtubules.

scholarly journals In vivo imaging of cell morphology and cellular processes in Caenorhabditis elegans, using non-linear phenomena

Micron ◽  
2009 ◽  
Vol 40 (8) ◽  
pp. 876-880 ◽  
Author(s):  
G. Filippidis ◽  
E.J. Gualda ◽  
M. Mari ◽  
K. Troulinaki ◽  
C. Fotakis ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Cell Morphology ◽  
In Vivo Imaging ◽  
Cellular Processes ◽  
Non Linear

scholarly journals The kinetically dominant assembly pathway for centrosomal asters in Caenorhabditis elegans is γ-tubulin dependent

2002 ◽  
Vol 157 (4) ◽  
pp. 591-602 ◽  
Author(s):  
Eva Hannak ◽  
Karen Oegema ◽  
Matthew Kirkham ◽  
Pierre Gönczy ◽  
Bianca Habermann ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Cytoplasmic Dynein ◽  
Self Organization ◽  
Mutant Form ◽  
C Elegans ◽  
Assembly Pathway

γ-Tubulin–containing complexes are thought to nucleate and anchor centrosomal microtubules (MTs). Surprisingly, a recent study (Strome, S., J. Powers, M. Dunn, K. Reese, C.J. Malone, J. White, G. Seydoux, and W. Saxton. Mol. Biol. Cell. 12:1751–1764) showed that centrosomal asters form in Caenorhabditis elegans embryos depleted of γ-tubulin by RNA-mediated interference (RNAi). Here, we investigate the nucleation and organization of centrosomal MT asters in C. elegans embryos severely compromised for γ-tubulin function. We characterize embryos depleted of ∼98% centrosomal γ-tubulin by RNAi, embryos expressing a mutant form of γ-tubulin, and embryos depleted of a γ-tubulin–associated protein, CeGrip-1. In all cases, centrosomal asters fail to form during interphase but assemble as embryos enter mitosis. The formation of these mitotic asters does not require ZYG-9, a centrosomal MT-associated protein, or cytoplasmic dynein, a minus end–directed motor that contributes to self-organization of mitotic asters in other organisms. By kinetically monitoring MT regrowth from cold-treated mitotic centrosomes in vivo, we show that centrosomal nucleating activity is severely compromised by γ-tubulin depletion. Thus, although unknown mechanisms can support partial assembly of mitotic centrosomal asters, γ-tubulin is the kinetically dominant centrosomal MT nucleator.

scholarly journals Caenorhabditis elegans Models to Investigate the Mechanisms Underlying Tau Toxicity in Tauopathies

2020 ◽  
Vol 10 (11) ◽  
pp. 838
Author(s):  
Carmina Natale ◽  
Maria Monica Barzago ◽  
Luisa Diomede
Keyword(s):  
Caenorhabditis Elegans ◽  
Relevant Information ◽  
Disease Genes ◽  
Structural Determinants ◽  
Significant Information ◽  
C Elegans ◽  
Cellular Processes ◽  
Tau Aggregation ◽  
Transgenic Strains

The understanding of the genetic, biochemical, and structural determinants underlying tau aggregation is pivotal in the elucidation of the pathogenic process driving tauopathies and the design of effective therapies. Relevant information on the molecular basis of human neurodegeneration in vivo can be obtained using the nematode Caenorhabditis elegans (C. elegans). To this end, two main approaches can be applied: the overexpression of genes/proteins leading to neuronal dysfunction and death, and studies in which proteins prone to misfolding are exogenously administered to induce a neurotoxic phenotype. Thanks to the easy generation of transgenic strains expressing human disease genes, C. elegans allows the identification of genes and/or proteins specifically associated with pathology and the specific disruptions of cellular processes involved in disease. Several transgenic strains expressing human wild-type or mutated tau have been developed and offer significant information concerning whether transgene expression regulates protein production and aggregation in soluble or insoluble form, onset of the disease, and the degenerative process. C. elegans is able to specifically react to the toxic assemblies of tau, thus developing a neurodegenerative phenotype that, even when exogenously administered, opens up the use of this assay to investigate in vivo the relationship between the tau sequence, its folding, and its proteotoxicity. These approaches can be employed to screen drugs and small molecules that can interact with the biogenesis and dynamics of formation of tau aggregates and to analyze their interactions with other cellular proteins.

scholarly journals Myosin 1b flattens and prunes branched actin filaments

2020 ◽  
Vol 133 (18) ◽  
pp. jcs247403 ◽  
Author(s):  
Julien Pernier ◽  
Antoine Morchain ◽  
Valentina Caorsi ◽  
Aurélie Bertin ◽  
Hugo Bousquet ◽  
...  
Keyword(s):  
Total Internal Reflection ◽  
Essential Role ◽  
Molecular Motor ◽  
Regulatory Proteins ◽  
Actin Network ◽  
Actin Networks ◽  
Cellular Processes ◽  
Branch Angle

ABSTRACTMotile and morphological cellular processes require a spatially and temporally coordinated branched actin network that is controlled by the activity of various regulatory proteins, including the Arp2/3 complex, profilin, cofilin and tropomyosin. We have previously reported that myosin 1b regulates the density of the actin network in the growth cone. Here, by performing in vitro F-actin gliding assays and total internal reflection fluorescence (TIRF) microscopy, we show that this molecular motor flattens (reduces the branch angle) in the Arp2/3-dependent actin branches, resulting in them breaking, and reduces the probability of new branches forming. This experiment reveals that myosin 1b can produce force sufficient enough to break up the Arp2/3-mediated actin junction. Together with the former in vivo studies, this work emphasizes the essential role played by myosins in the architecture and dynamics of actin networks in different cellular regions.This article has an associated First Person interview with the first author of the paper.

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