scholarly journals Spatial organization of cortical actin alignments for the ooplasmic segregation of ascidian Ciona eggs

2019 ◽  
Author(s):  
Hirokazu Ishii ◽  
Tomomi Tani
Keyword(s):  
Fluorescence Polarization ◽  
Spatial Organization ◽  
The Body ◽  
Cell Cortex ◽  
Polarization Microscopy ◽  
Cortical Actin ◽  
Local Contraction ◽  
Spatial Reorganization ◽  
Vegetal Pole ◽  
Ooplasmic Segregation

ABSTRACTSpatial reorganization of cytoplasm in zygotic cells is critically important for establishing the body plans of many animal species. In ascidian zygotes, maternal determinants (mRNAs) are first transported to the vegetal pole a few minutes after the fertilization, and then to the future posterior side of the zygotes in later phase of the cytoplasmic reorganization, before the first cell division. Here, by using a novel fluorescence polarization microscope that reports the position and the orientation of fluorescently labeled proteins in living cells, we mapped the local alignments and the time-dependent changes of cortical actin networks in Ciona eggs. The initial cytoplasmic reorganization started with the contraction of vegetal hemisphere ∼20s after the fertilization induced [Ca2+] increase. Timing of the vegetal contraction was consistent with the emergence of highly aligned actin filaments at the cell cortex of vegetal hemisphere which ran perpendicular to the animal-vegetal axis. We propose that the first ooplasmic segregation is initiated by the local contraction of laterally aligned cortical actomyosin in the vegetal hemisphere, which in turn generates the convectional flow of cytoplasm within whole eggs.SUMMARY STATEMENTLocally distinct, transient emergence of cortical F-actin alignments were observed in live ascidian Ciona eggs during the first ooplasmic segregation by using fluorescence polarization microscopy.

scholarly journals Dynamic organization of cortical actin filaments during the ooplasmic segregation of ascidian Ciona eggs

2020 ◽  
pp. mbc.E20-01-0083
Author(s):  
Hirokazu Ishii ◽  
Tomomi Tani
Keyword(s):  
Actin Filaments ◽  
The Body ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Local Contraction ◽  
Directional Movement ◽  
Spatial Reorganization ◽  
Vegetal Pole ◽  
Ooplasmic Segregation ◽  
Maternal Determinants

Spatial reorganization of cytoplasm in zygotic cells is critically important for establishing the body plans of many animal species. In ascidian zygotes, maternal determinants (mRNAs) are first transported to the vegetal pole a few minutes after the fertilization, and then to the future posterior side of the zygotes in later phase of the cytoplasmic reorganization, before the first cell division. Here, by using a novel fluorescence polarization microscope that reports the position and the orientation of fluorescently labeled proteins in living cells, we mapped the local alignments and the time-dependent changes of cortical actin networks in Ciona eggs. The initial cytoplasmic reorganization started with the contraction of vegetal hemisphere approximately 20 s after the fertilization induced [Ca2+] increase. Timing of the vegetal contraction was consistent with the emergence of highly aligned actin filaments at the cell cortex of vegetal hemisphere which ran perpendicular to the animal-vegetal axis. We propose that the cytoplasmic reorganization is initiated by the local contraction of laterally aligned cortical actomyosin in the vegetal hemisphere, which in turn generates the directional movement of cytoplasm within whole egg. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text]

scholarly journals Pan1p, End3p, and Sla1p, Three Yeast Proteins Required for Normal Cortical Actin Cytoskeleton Organization, Associate with Each Other and Play Essential Roles in Cell Wall Morphogenesis

2000 ◽  
Vol 20 (1) ◽  
pp. 12-25 ◽  
Author(s):  
Hsin-Yao Tang ◽  
Jing Xu ◽  
Mingjie Cai
Keyword(s):  
Cell Wall ◽  
Actin Cytoskeleton ◽  
Normal Cell ◽  
Cell Cortex ◽  
Repeat Region ◽  
Cortical Actin ◽  
Cytoskeleton Organization ◽  
Eh Domain ◽  
Actin Cytoskeleton Organization ◽  
Cell Wall Morphogenesis

ABSTRACT The EH domain proteins Pan1p and End3p of budding yeast have been known to form a complex in vivo and play important roles in organization of the actin cytoskeleton and endocytosis. In this report, we describe new findings concerning the function of the Pan1p-End3p complex. First, we found that the Pan1p-End3p complex associates with Sla1p, another protein known to be required for the assembly of cortical actin structures. Sla1p interacts with the first long repeat region of Pan1p and the N-terminal EH domain of End3p, thus leaving the Pan1p-End3p interaction, which requires the second long repeat of Pan1p and the C-terminal repeat region of End3p, undisturbed. Second, Pan1p, End3p, and Sla1p are also required for normal cell wall morphogenesis. Each of the Pan1-4, sla1Δ, andend3Δ mutants displays the abnormal cell wall morphology previously reported for the act1-1 mutant. These cell wall defects are also exhibited by wild-type cells overproducing the C-terminal region of Sla1p that is responsible for interactions with Pan1p and End3p. These results indicate that the functions of Pan1p, End3p, and Sla1p in cell wall morphogenesis may depend on the formation of a heterotrimeric complex. Interestingly, the cell wall abnormalities exhibited by these cells are independent of the actin cytoskeleton organization on the cell cortex, as they manifest despite the presence of apparently normal cortical actin cytoskeleton. Examination of several act1 mutants also supports this conclusion. These observations suggest that the Pan1p-End3p-Sla1p complex is required not only for normal actin cytoskeleton organization but also for normal cell wall morphogenesis in yeast.

scholarly journals Mechanism of the formation of contractile ring in dividing cultured animal cells. II. Cortical movement of microinjected actin filaments.

1990 ◽  
Vol 111 (5) ◽  
pp. 1905-1911 ◽  
Author(s):  
L G Cao ◽  
Y L Wang
Keyword(s):  
Actin Filaments ◽  
Average Rate ◽  
Rat Kidney ◽  
Equatorial Region ◽  
Cell Cortex ◽  
Polar Regions ◽  
Cortical Actin ◽  
Animal Cells ◽  
Contractile Ring ◽  
Directional Movement

The contractile ring in dividing animal cells is formed primarily through the reorganization of existing actin filaments (Cao, L.-G., and Y.-L. Wang. 1990. J. Cell Biol. 110:1089-1096), but it is not clear whether the process involves a random recruitment of diffusible actin filaments from the cytoplasm, or a directional movement of cortically associated filaments toward the equator. We have studied this question by observing the distribution of actin filaments that have been labeled with fluorescent phalloidin and microinjected into dividing normal rat kidney (NRK) cells. The labeled filaments are present primarily in the cytoplasm during prometaphase and early metaphase, but become associated extensively with the cell cortex 10-15 min before the onset of anaphase. This process is manifested both as an increase in cortical fluorescence intensity and as movements of discrete aggregates of actin filaments toward the cortex. The concentration of actin fluorescence in the equatorial region, accompanied by a decrease of fluorescence in polar regions, is detected 2-3 min after the onset of anaphase. By directly tracing the distribution of aggregates of labeled actin filaments, we are able to detect, during anaphase and telophase, movements of cortical actin filaments toward the equator at an average rate of 1.0 micron/min. Our results, combined with previous observations, suggest that the organization of actin filaments during cytokinesis probably involves an association of cytoplasmic filaments with the cortex, a movement of cortical filaments toward the cleavage furrow, and a dissociation of filaments from the equatorial cortex.

scholarly journals Cell-state transitions and collective cell movement generate an endoderm-like region in gastruloids

2020 ◽  
Author(s):  
Ali Hashmi ◽  
Sham Tlili ◽  
Pierre Perrin ◽  
Alfonso Martinez-Arias ◽  
Pierre-François Lenne
Keyword(s):  
Spatial Organization ◽  
Embryonic Stem ◽  
Cell Movement ◽  
Body Plan ◽  
The Body ◽  
State Transitions ◽  
Sequence Of Events ◽  
Complex Process ◽  
Cell Layers ◽  
Sorting Process

AbstractShaping the animal body plan is a complex process that involves the spatial organization and patterning of different cell layers. Recent advances in live imaging have started to unravel the cellular choreography underlying this process in mammals, however, the sequence of events transforming an unpatterned cell ensemble into structured territories is largely unknown. Here, using 3D aggregates of mouse embryonic stem cells, we study the formation of one of the three germ layers, the endoderm. We show that the endoderm is generated from an epiblast-like state by a three-step mechanism: a release of islands of Ecadherin expressing cells, their flow toward the aggregate tip, and their segregation. Unlike the prevailing view, this mechanism does not require epithelial-to-mesenchymal transitions and vice-versa but rather a fragmentation, which is mediated by Wnt/β-catenin, and a sorting process. Our data emphasize the role of signaling and cell flows in the establishment of the body plan.

Fertilization and ooplasmic movements in the ascidian egg

Development ◽  
1989 ◽  
Vol 105 (2) ◽  
pp. 237-249 ◽  
Author(s):  
C. Sardet ◽  
J. Speksnijder ◽  
S. Inoue ◽  
L. Jaffe
Keyword(s):  
Polar Body ◽  
Surface Velocity ◽  
Second Phase ◽  
Animal Pole ◽  
Male Pronucleus ◽  
Vegetal Pole ◽  
Female Pronucleus ◽  
Ooplasmic Segregation ◽  
Second Polar Body ◽  
Sperm Aster

Using light microscopy techniques, we have studied the movements that follow fertilization in the denuded egg of the ascidian Phallusia mammillata. In particular, our observations show that, as a result of a series of movements described below, the mitochondria-rich subcortical myoplasm is split in two parts during the second phase of ooplasmic segregation. This offers a potential explanation for the origin of larval muscle cells from both posterior and anterior blastomeres. The first visible event at fertilization is a bulging at the animal pole of the egg, which is immediately followed by a wave of contraction, travelling towards the vegetal pole with a surface velocity of 1.4 microns s-1. This wave accompanies the first phase of ooplasmic segregation of the mitochondria-rich subcortical myoplasm. After this contraction wave has reached the vegetal pole after about 2 min, a transient cytoplasmic lobe remains there until 6 min after fertilization. Several new features of the morphogenetic movements were then observed: between the extrusion of the first and second polar body (at 5 and 24–29 min, respectively), a series of transient animal protrusions form at regular intervals. Each animal protrusion involves a flow of the centrally located cytoplasm in the animal direction. Shortly before the second polar body is extruded, a second transient vegetal lobe (‘the vegetal button’) forms, which, like the first, resembles a protostome polar lobe. Immediately after the second polar body is extruded, three events occur almost simultaneously: first, the sperm aster moves from the vegetal hemisphere to the equator. Second, the bulk of the vegetally located myoplasm moves with the sperm aster towards the future posterior pole, but interestingly about 20% remains behind at the anterior side of the embryo. This second phase of myoplasmic movement shows two distinct subphases: a first, oscillatory subphase with an average velocity of about 6 microns min-1, and a second steady subphase with a velocity of about 26 microns min-1. The myoplasm reaches its final position as the male pronucleus with its surrounding aster moves towards the centre of the egg. Third, the female pronucleus moves towards the centre of the egg to meet with the male pronucleus. Like the myoplasm, the migrations of both the sperm aster and the female pronucleus shows two subphases with distinctly different velocities. Finally, the pronuclear membranes dissolve, a small mitotic spindle is formed with very large asters, and at about 60–65 min after fertilization, the egg cleaves.

A gastrulation center in the ascidian egg

Development ◽  
1992 ◽  
Vol 116 (Supplement) ◽  
pp. 53-63 ◽  
Author(s):  
William R. Jeffery
Keyword(s):  
Nervous System ◽  
Uv Irradiation ◽  
Second Phase ◽  
Uv Sensitivity ◽  
Maternal Mrna ◽  
Free Translation ◽  
Vegetal Pole ◽  
Cell Embryo ◽  
Ooplasmic Segregation ◽  
Uv Dose

A gastrulation center is described in ascidian eggs. Extensive cytoplasmic rearrangements occur in ascidian eggs between fertilization and first cleavage. During ooplasmic segregation, a specific cytoskeletal domain (the myoplasm) is translocated first to the vegetal pole (VP) and then to the posterior region of the zygote. A few hours later, gastrulation is initiated by invagination of endoderm cells in the VP region of the 110-cell embryo. After the completion of gastrulation, the embryonic axis is formed, which includes induction of the nervous system, morphogenesis of the larval tail and differentiation of tail muscle cells. Microsurgical deletion or ultraviolet (UV) irradiation of the VP region during the first phase of myoplasmic segregation prevents gastrulation, nervous system induction and tail formation, without affecting muscle cell differentiation. Similar manipulations of unfertilized eggs or uncleaved zygotes after the second phase of segregation have no effect on development, suggesting that a gastrulation center is established by transient localization of myoplasm in the VP region. The function of the gastrulation center was investigated by comparing protein synthesis in normal and UV-irradiated embryos. About 5% of 433 labelled polypeptides detected in 2D gels were affected by UV irradiation. The most prominent protein is a 30 kDa cytoskeletal component (p30), whose synthesis is abolished by UV irradiation. p30 synthesis peaks during gastrulation, is affected by the same UV dose and has the same UV-sensitivity period as gastrulation. However, p30 is not a UV-sensitive target because it is absent during ooplasmic segregation, the UV-sensitivity period. Moreover, the UV target has the absorption maximum of a nucleic acid rather than a protein. Cell-free translation studies indicate that p30 is encoded by a maternal mRNA. UV irradiation inhibits the ability of this transcript to direct p30 synthesis, indicating that p30 mRNA is a UV-sensitive target The gastrulation center may function by sequestration or activation of maternal mRNAs encoding proteins that function during embryogenesis.

Sla1p couples the yeast endocytic machinery to proteins regulating actin dynamics

2002 ◽  
Vol 115 (8) ◽  
pp. 1703-1715 ◽  
Author(s):  
Derek T. Warren ◽  
Paul D. Andrews ◽  
Campbell W. Gourlay ◽  
Kathryn R. Ayscough
Keyword(s):  
Immunofluorescence Microscopy ◽  
Fluid Phase ◽  
Actin Dynamics ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Binding Studies ◽  
Endocytic Machinery ◽  
Single Complex ◽  
Actin Patch ◽  
First Time

Sla1p is a protein required for cortical actin patch structure and organisation in budding yeast. Here we use a combination of immunofluorescence microscopy and biochemical approaches to demonstrate interactions of Sla1p both with proteins regulating actin dynamics and with proteins required for endocytosis. Using Sla1p-binding studies we reveal association of Sla1p with two proteins known to be important for activation of the Arp2/3 complex in yeast, Abp1p and the yeast WASP homologue Las17p/Bee1p. A recent report of Sla1p association with Pan1p puts Sla1p in the currently unique position of being the only yeast protein known to interact with all three known Arp2/3-activating proteins in yeast. Localisation of Sla1p at the cell cortex is, however, dependent on the EH-domain-containing protein End3p, which is part of the yeast endocytic machinery. Using spectral variants of GFP on Sla1p(YFP) and on Abp1p (CFP) we show for the first time that these proteins can exist in discrete complexes at the cell cortex. However, the detection of a significant FRET signal means that these proteins also come close together in a single complex, and it is in this larger complex that we propose that Sla1p binding to Abp1p and Las17p/Bee1p is able to link actin dynamics to the endocytic machinery. Finally, we demonstrate marked defects in both fluid-phase and receptor-mediated endocytosis in cells that do not express SLA1, indicating that Sla1p is central to the requirement in yeast to couple endocytosis with the actin cytoskeleton.

scholarly journals Vimentin filaments interact with the actin cortex in mitosis allowing normal cell division

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Sofia Duarte ◽  
Álvaro Viedma-Poyatos ◽  
Elena Navarro-Carrasco ◽  
Alma E. Martínez ◽  
María A. Pajares ◽  
...  
Keyword(s):  
Cell Division ◽  
Cell Types ◽  
Hiv Protease ◽  
Cell Cortex ◽  
Tail Domain ◽  
Cellular Functions ◽  
Cortical Actin ◽  
Intrinsically Disordered ◽  
Actin Cortex ◽  
Vimentin Filaments

Abstract The vimentin network displays remarkable plasticity to support basic cellular functions and reorganizes during cell division. Here, we show that in several cell types vimentin filaments redistribute to the cell cortex during mitosis, forming a robust framework interwoven with cortical actin and affecting its organization. Importantly, the intrinsically disordered tail domain of vimentin is essential for this redistribution, which allows normal mitotic progression. A tailless vimentin mutant forms curly bundles, which remain entangled with dividing chromosomes leading to mitotic catastrophes or asymmetric partitions. Serial deletions of vimentin tail domain gradually impair cortical association and mitosis progression. Disruption of f-actin, but not of microtubules, causes vimentin bundling near the chromosomes. Pathophysiological stimuli, including HIV-protease and lipoxidation, induce similar alterations. Interestingly, full filament formation is dispensable for cortical association, which also occurs in vimentin particles. These results unveil implications of vimentin dynamics in cell division through its interplay with the actin cortex.

scholarly journals The Northwestern Amazon malocas: Craft now and then

2019 ◽  
Vol 25 (1) ◽  
pp. 3-35
Author(s):  
Maria Paz Gutierrez
Keyword(s):  
Material Culture ◽  
Social Engagement ◽  
Spatial Organization ◽  
Economic Cost ◽  
The Body ◽  
Galvanized Steel ◽  
Social Characteristics ◽  
Human Comfort ◽  
Technical Practice ◽  
Living Entity

In the Northwestern Amazon, resilience in construction has been traditionally conceived as a capacity for social, climatic, and spatial adaptability. Through methods of seasonal reconstruction based on lightweight enclosures made mainly from palms, vernacular housing, or malocas, in the region have proven efficient from environmental, human comfort, and cultural perspectives. Intricately woven palms, layered to shape roofs and walls, form enclosures that repel water, insulate heat, and reflect light while embodying specific projections of the body in space as the basis of unique cosmological perspectives of spatial organization. The palm-weave is the very root of the construction ethos of Northwestern Amazon housing. In the last few decades, these complex woven enclosures have been progressively replaced with industrial panels made of materials such as galvanized steel or cement, simply because of their low economic cost and availability. The loss of the palm-weave in roof-walls is not a mere replacement but a supplantation of material culture and has profound environmental, human comfort, and social implications. In a context where resilience has been shaped cognitively and physically through a plant-based material culture of adaptability, what is the extent of a potential craft disruption? The supplantation of the palm-weave technical practice implies a loss of social engagement in a craft that has defined an understanding of belonging and inhabitation. This article addresses how the geometric, scale, and spatial characteristics originating from the distinctive palm-weave craft of the Western Amazon malocas of the Bora, Miraña, Muiname (Witoto), Murui (Witoto), Yukuna, Tikuna, and Makuna groups perform as a living entity. By questioning the differences between craft preservation vis-à-vis reclamation, the author explores the specific architectural and social characteristics that are locally valued in the inherited craft to create a path for discussing future generations of palm-weave in the Northwestern Amazon.

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