scholarly journals Structural and Functional Insights into the Microtubule Organizing Centers of Toxoplasma gondii and Plasmodium spp.

2021 ◽  
Vol 9 (12) ◽  
pp. 2503
Author(s):  
Ramiro Tomasina ◽  
Fabiana C. González ◽  
Maria E. Francia
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Large Body ◽  
Plasmodium Species ◽  
Single Species ◽  
Sexual Life ◽  
Cellular Functions ◽  
Microtubule Organization ◽  
Microtubule Organizing Centers ◽  
Causative Agents

Microtubule organizing centers (MTOCs) perform critical cellular tasks by nucleating, stabilizing, and anchoring microtubule’s minus ends. These capacities impact tremendously a wide array of cellular functions ranging from ascribing cell shape to orchestrating cell division and generating motile structures, among others. The phylum Apicomplexa comprises over 6000 single-celled obligate intracellular parasitic species. Many of the apicomplexan are well known pathogens such as Toxoplasma gondii and the Plasmodium species, causative agents of toxoplasmosis and malaria, respectively. Microtubule organization in these parasites is critical for organizing the cortical cytoskeleton, enabling host cell penetration and the positioning of large organelles, driving cell division and directing the formation of flagella in sexual life stages. Apicomplexans are a prime example of MTOC diversity displaying multiple functional and structural MTOCs combinations within a single species. This diversity can only be fully understood in light of each organism’s specific MT nucleation requirements and their evolutionary history. Insight into apicomplexan MTOCs had traditionally been limited to classical ultrastructural work by transmission electron microscopy. However, in the past few years, a large body of molecular insight has emerged. In this work we describe the latest insights into nuclear MTOC biology in two major human and animal disease causing Apicomplexans: Toxoplasma gondii and Plasmodium spp.

scholarly journals Structural and Functional Insights into the Microtubule Organizing Centers of Toxoplasma gondii and Plasmodium spp.

2021 ◽  
Author(s):  
Ramiro Tomasina ◽  
Fabiana González ◽  
Maria E. Francia
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Large Body ◽  
Plasmodium Species ◽  
Single Species ◽  
Sexual Life ◽  
Cellular Functions ◽  
Microtubule Organization ◽  
Microtubule Organizing Centers ◽  
Causative Agents

Microtubule organizing centers (MTOCs) perform critical cellular tasks by nucleating, stabilizing and anchoring microtubule’s minus ends. These capacities impact tremendously a wide array of cellular functions ranging from ascribing cell shape to orchestrating cell division and generating motile structures, among others. The phylum Apicomplexa comprises over 6000 single-celled obligate intracellular parasitic species. Many of the apicomplexan are well known pathogens such as Toxoplasma gondii and the Plasmodium species, causative agents of toxoplasmosis and malaria, respectively. Microtubule organization in these parasites is critical for organizing the cortical cytoskeleton, enabling host cell penetration and the positioning of large organelles, drive cell division and direct the formation of flagella in sexual life stages. Apicomplexans are a prime example of MTOC diversity displaying multiple functional and structural MTOCs combinations within a single species. This diversity can only be fully understood in light of each organism's specific MT nucleation requirements and their evolutionary history. Insight into apicomplexan MTOCs had traditionally been limited to classical ultrastructural work by transmission electron microscopy. However, in the past few years, a large body of molecular insight has emerged. In this work we describe the latest insights into nuclear MTOC biology in two major human and animal disease causing Apicomplexans; Toxoplasma gondii and Plasmodium spp.

scholarly journals The Plastid of Toxoplasma gondii Is Divided by Association with the Centrosomes

2000 ◽  
Vol 151 (7) ◽  
pp. 1423-1434 ◽  
Author(s):  
Boris Striepen ◽  
Michael J. Crawford ◽  
Michael K. Shaw ◽  
Lewis G. Tilney ◽  
Frank Seeber ◽  
...  
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Genetic Manipulation ◽  
Fluorescent Proteins ◽  
Recombinant Expression ◽  
Molecular Genetic ◽  
Time Lapse ◽  
Microtubule Organization ◽  
Apicomplexan Parasites ◽  
Daughter Cells

Apicomplexan parasites harbor a single nonphotosynthetic plastid, the apicoplast, which is essential for parasite survival. Exploiting Toxoplasma gondii as an accessible system for cell biological analysis and molecular genetic manipulation, we have studied how these parasites ensure that the plastid and its 35-kb circular genome are faithfully segregated during cell division. Parasite organelles were labeled by recombinant expression of fluorescent proteins targeted to the plastid and the nucleus, and time-lapse video microscopy was used to image labeled organelles throughout the cell cycle. Apicoplast division is tightly associated with nuclear and cell division and is characterized by an elongated, dumbbell-shaped intermediate. The plastid genome is divided early in this process, associating with the ends of the elongated organelle. A centrin-specific antibody demonstrates that the ends of dividing apicoplast are closely linked to the centrosomes. Treatment with dinitroaniline herbicides (which disrupt microtubule organization) leads to the formation of multiple spindles and large reticulate plastids studded with centrosomes. The mitotic spindle and the pellicle of the forming daughter cells appear to generate the force required for apicoplast division in Toxoplasma gondii. These observations are discussed in the context of autonomous and FtsZ-dependent division of plastids in plants and algae.

scholarly journals Self-Organization of Spindle-Like Microtubule Structures

2019 ◽  
Author(s):  
Bianca Edozie ◽  
Sumon Sahu ◽  
Miranda Pitta ◽  
Anthony Englert ◽  
Carline Fermino do Rosario ◽  
...  
Keyword(s):  
Cell Division ◽  
Motor Activity ◽  
Motor Proteins ◽  
The Self ◽  
Self Organization ◽  
Shape Prior ◽  
Cellular Functions ◽  
Microtubule Organization ◽  
Self Organized ◽  
Crosslinker Concentration

ABSTRACTMicrotubule self-organization is an important physical process underlying a number of essential cellular functions including cell division. In cell division, the dominant organization is the mitotic spindle, a football-shaped microtubule organization. We are interested in the underlying fundamental principles behind the self-organization of the spindle shape. Prior biological works have hypothesized that motor proteins are required for the proper formation of the spindle. Many of these motor proteins are also microtubule-crosslinkers, so it is unclear if the important aspect is the motor activity or the crosslinking. In this study, we seek to address this question by examining the self-organization of microtubules using crosslinkers alone. We use a minimal system composed of tubulin, an antiparallel microtubule-crosslinking protein, and a crowding agent to explore the phase space of organizations as a function of tubulin and crosslinker concentration. We find that the concentration of the antiparallel crosslinker, MAP65, has a significant effect on the organization and resulted in spindle-like organizations at relatively low concentration without the need for motor activity. Surprisingly, the length of the microtubules only moderately affects the equilibrium organization. We characterize both the shape and dynamics of these spindle-like organizations. We find that they are birefringent homogeneous tactoids. The microtubules have slow mobility, but the crosslinkers have fast mobility within the tactoids. These structures represent a first step in the recapitulation of self-organized spindles of microtubules that can be used as initial structures for further biophysical and active matter studies relevant to the biological process of cell division.

scholarly journals Cytokinesis and Midzone Microtubule Organization inCaenorhabditis elegans Require the Kinesin-like Protein ZEN-4

1998 ◽  
Vol 9 (8) ◽  
pp. 2037-2049 ◽  
Author(s):  
William B. Raich ◽  
Adrienne N. Moran ◽  
Joel H. Rothman ◽  
Jeff Hardin
Keyword(s):  
Cell Division ◽  
Null Allele ◽  
Time Lapse ◽  
Equatorial Region ◽  
Microtubule Organization ◽  
Dividing Cells ◽  
Spindle Midzone ◽  
Cross Links ◽  
Complete Cell

Members of the MKLP1 subfamily of kinesin motor proteins localize to the equatorial region of the spindle midzone and are capable of bundling antiparallel microtubules in vitro. Despite these intriguing characteristics, it is unclear what role these kinesins play in dividing cells, particularly within the context of a developing embryo. Here, we report the identification of a null allele ofzen-4, an MKLP1 homologue in the nematodeCaenorhabditis elegans, and demonstrate that ZEN-4 is essential for cytokinesis. Embryos deprived of ZEN-4 form multinucleate single-celled embryos as they continue to cycle through mitosis but fail to complete cell division. Initiation of the cytokinetic furrow occurs at the normal time and place, but furrow propagation halts prematurely. Time-lapse recordings and microtubule staining reveal that the cytokinesis defect is preceded by the dissociation of the midzone microtubules. We show that ZEN-4 protein localizes to the spindle midzone during anaphase and persists at the midbody region throughout cytokinesis. We propose that ZEN-4 directly cross-links the midzone microtubules and suggest that these microtubules are required for the completion of cytokinesis.

scholarly journals Toxoplasma gondii myosins B/C

2001 ◽  
Vol 155 (4) ◽  
pp. 613-624 ◽  
Author(s):  
Frédéric Delbac ◽  
Astrid Sänger ◽  
Eva M. Neuhaus ◽  
Rolf Stratmann ◽  
James W. Ajioka ◽  
...  
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Daughter Cell ◽  
Gliding Motility ◽  
Apicomplexan Parasites ◽  
Daughter Cells ◽  
Membrane Complex ◽  
Alternatively Spliced ◽  
Butanedione Monoxime ◽  
Inner Membrane Complex

In apicomplexan parasites, actin-disrupting drugs and the inhibitor of myosin heavy chain ATPase, 2,3-butanedione monoxime, have been shown to interfere with host cell invasion by inhibiting parasite gliding motility. We report here that the actomyosin system of Toxoplasma gondii also contributes to the process of cell division by ensuring accurate budding of daughter cells. T. gondii myosins B and C are encoded by alternatively spliced mRNAs and differ only in their COOH-terminal tails. MyoB and MyoC showed distinct subcellular localizations and dissimilar solubilities, which were conferred by their tails. MyoC is the first marker selectively concentrated at the anterior and posterior polar rings of the inner membrane complex, structures that play a key role in cell shape integrity during daughter cell biogenesis. When transiently expressed, MyoB, MyoC, as well as the common motor domain lacking the tail did not distribute evenly between daughter cells, suggesting some impairment in proper segregation. Stable overexpression of MyoB caused a significant defect in parasite cell division, leading to the formation of extensive residual bodies, a substantial delay in replication, and loss of acute virulence in mice. Altogether, these observations suggest that MyoB/C products play a role in proper daughter cell budding and separation.

scholarly journals EB1 and EB3 regulate microtubule minus end organization and Golgi morphology

2017 ◽  
Vol 216 (10) ◽  
pp. 3179-3198 ◽  
Author(s):  
Chao Yang ◽  
Jingchao Wu ◽  
Cecilia de Heus ◽  
Ilya Grigoriev ◽  
Nalan Liv ◽  
...  
Keyword(s):  
Cell Division ◽  
Cell Lines ◽  
Protein Complexes ◽  
Focal Adhesions ◽  
Microtubule Organization ◽  
The Core ◽  
Microtubule Polymerization ◽  
Golgi Membranes ◽  
Core Components ◽  
Knockout Technology

End-binding proteins (EBs) are the core components of microtubule plus end tracking protein complexes, but it is currently unknown whether they are essential for mammalian microtubule organization. Here, by using CRISPR/Cas9-mediated knockout technology, we generated stable cell lines lacking EB2 and EB3 and the C-terminal partner-binding half of EB1. These cell lines show only mild defects in cell division and microtubule polymerization. However, the length of CAMSAP2-decorated stretches at noncentrosomal microtubule minus ends in these cells is reduced, microtubules are detached from Golgi membranes, and the Golgi complex is more compact. Coorganization of microtubules and Golgi membranes depends on the EB1/EB3–myomegalin complex, which acts as membrane–microtubule tether and counteracts tight clustering of individual Golgi stacks. Disruption of EB1 and EB3 also perturbs cell migration, polarity, and the distribution of focal adhesions. EB1 and EB3 thus affect multiple interphase processes and have a major impact on microtubule minus end organization.

scholarly journals The 3D architecture and molecular foundations of de novo centriole assembly via bicentrioles

2020 ◽  
Author(s):  
Sónia Gomes Pereira ◽  
Ana Laura Sousa ◽  
Catarina Nabais ◽  
Tiago Paixão ◽  
Alexander. J. Holmes ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Division ◽  
De Novo ◽  
Cellular Functions ◽  
Spindle Poles ◽  
3D Architecture ◽  
Centriole Assembly ◽  
Work Supports ◽  
Wall Components

Abstract/SummaryCentrioles are structurally conserved organelles, composing both centrosomes and cilia. In animal cycling cells, centrioles often form through a highly characterized process termed canonical duplication. However, a large diversity of eukaryotes form centrioles de novo through uncharacterized pathways. This unexplored diversity is key to understanding centriole assembly mechanisms and how they evolved to assist specific cellular functions. Here, combining electron microscopy and tomography, we show that during spermatogenesis of the moss Physcomitrium patens, centrioles are born as a co-axially oriented centriole pair united by a cartwheel. We observe that microtubules emanate from those bicentrioles, which localize to the spindle poles during cell division. Thereafter, each bicentriole breaks apart, and the two resulting sister centrioles mature asymmetrically, elongating specific microtubule triplets and a naked cartwheel. Subsequently, two cilia are assembled which are capable of beating asynchronously. We further show that conserved cartwheel and centriole wall components, SAS6, BLD10 and POC1 are expressed during spermatogenesis and are required for this de novo biogenesis pathway. Our work supports a scenario where centriole biogenesis is more diverse than previously thought and that conserved molecular modules underlie diversification of this essential pathway.

scholarly journals Microtubule organization: A complex solution

2016 ◽  
Vol 213 (6) ◽  
pp. 609-612 ◽  
Author(s):  
Paul T. Conduit
Keyword(s):  
Complex Solution ◽  
Microtubule Nucleation ◽  
Microtubule Organization ◽  
Microtubule Organizing Centers ◽  
Cell Biol ◽  
Ring Complexes ◽  
And Function

Microtubule nucleation within cells is catalyzed by γ-tubulin ring complexes localized at specific microtubule-organizing centers. In this issue, Muroyama et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201601099) reveal heterogeneity in the composition and function of these complexes, with wide implications for how cells organize their microtubule arrays.

An ultradian clock controls locomotor behaviour and cell division in isolated cells of Paramecium tetraurelia

1996 ◽  
Vol 109 (4) ◽  
pp. 867-873 ◽  
Author(s):  
F. Kippert
Keyword(s):  
Cell Division ◽  
Time Window ◽  
Phase Relationship ◽  
Paramecium Tetraurelia ◽  
Temporal Control ◽  
Cellular Functions ◽  
Isolated Cells ◽  
Optimum Growth Temperature ◽  
Locomotor Behaviour ◽  
Generation Times

An ultradian clock operates in fast growing cells of the large ciliate, Paramecium tetraurelia. The period of around 70 minutes is well temperature-compensated over the temperature range tested, i.e. between 18 degrees C and 33 degrees C. The Q10 between 18 degrees C and 27 degrees C is 1.08; above 27 degrees C there is a slight overcompensation. The investigation of individual cells has revealed that two different cellular functions are under temporal control by this ultradian clock. First, locomotor behaviour, which is an alternation between a phase of fast swimming with only infrequent turning, and a phase of slow swimming with frequent spontaneous changes of direction. In addition, the ultradian clock is involved in the timing of cell division. Generation times are not randomly distributed, but occur in well separated clusters. At all of the six temperatures tested, the clusters are separated by around 70 minutes which corresponds well to the period of the locomotor behaviour rhythm at the respective temperatures. Whereas the interdivision times were gradually lengthened both above and below the optimum growth temperature, the underlying periodicity remained unaffected. Also cells of different clonal age had identical periods, suggesting that neither the differences in DNA content, not other changes associated with ageing in Paramecium have an effect on the clock. A constant phase relationship was observed between the rhythm in locomotor behaviour and the time window for cell division; this strongly suggests that the same ultradian clock exerts temporal control over both processes.

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