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Microtubules

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Articles 1 - 26 of 26

Full-Text Articles in Cell Biology

Temporal Coordination Of Mitotic Chromosome Alignment And Segregation: Structural And Functional Studies Of Kif18a, Haein Kim Jan 2018

Temporal Coordination Of Mitotic Chromosome Alignment And Segregation: Structural And Functional Studies Of Kif18a, Haein Kim

Graduate College Dissertations and Theses

Chromosome alignment is highly conserved in all eukaryotic cell divisions. Microtubule (MT) -based forces generated by the mitotic spindle are integral for proper chromosome alignment and equal chromosome segregation. The kinetochore is a multi-subunit protein complex that assembles on centromeric regions of chromosomes. Kinetochores tether chromosomes to MTs (K fibers) that emanate from opposite poles, in a process called biorientation. This linkage translates K fiber dynamics into chromosome movements during alignment and segregation. Stable, high-affinity kinetochore attachments promote spindle assembly checkpoint (SAC) silencing, which is active when unattached kinetochores are present. During chromosome alignment, 1) K fiber plus-end dynamics decrease ...


Tno1, A Tgn-Localized Snare-Interacting Protein, Modulates Root Skewing In Arabidopsis Thaliana, Rahul Roy, Diane C. Bassham Jan 2017

Tno1, A Tgn-Localized Snare-Interacting Protein, Modulates Root Skewing In Arabidopsis Thaliana, Rahul Roy, Diane C. Bassham

Genetics, Development and Cell Biology Publications

Background: The movement of plant roots within the soil is key to their ability to interact with the environment and maximize anchorage and nutrient acquisition. Directional growth of roots occurs by a combination of sensing external cues, hormonal signaling and cytoskeletal changes in the root cells. Roots growing on slanted, impenetrable growth medium display a characteristic waving and skewing, and mutants with deviations in these phenotypes assist in identifying genes required for root movement. Our study identifies a role for a trans-Golgi network-localized protein in root skewing.

Results: We found that Arabidopsis thaliana TNO1 (TGN-localized SYP41-interacting protein), a putative tethering ...


4-Nonylphenol Induces Neurodegeneration By Altering Cytoskeleton, Cynthia Carreon Jan 2017

4-Nonylphenol Induces Neurodegeneration By Altering Cytoskeleton, Cynthia Carreon

Open Access Theses & Dissertations

4-nonylphenol (4-NP), an endocrine-disrupting compound (EDC), has been shown to affect brain development and may cause neurodegeneration. In the environment, 4-NP arises as a degradation product of alkylphenol polyethoxylates, compounds widely used as nonionic surfactants in commercial production, as well as in herbicides, pesticides, polystyrene plastics, and paints and has been shown to undergo a high level of accumulation in biological tissues. However, the mechanism by which 4-NP exerts its effect is not understood. Recent results from our laboratory indicate that Gβγ, an important component of the G protein-signaling pathway, induces neuronal outgrowth and differentiation by modulating microtubule (MT) assembly ...


The Far C-Terminus Of Tpx2 Contributes To Spindle Morphogenesis, Brett Estes Jan 2017

The Far C-Terminus Of Tpx2 Contributes To Spindle Morphogenesis, Brett Estes

Masters Theses

A cell must build a bipolar mitotic spindle in order to faithfully segregate replicated DNA. To do so, multiple microtubule nucleation pathways are utilized to generate the robust spindle apparatus. TPX2, a microtubule binding protein, holds crucial roles in both the Ran-dependent and Augmin-dependent pathways where microtubules are nucleated near the chromosomes and from pre-existing microtubules. However, the exact role TPX2 plays in branching microtubules is less understood. Here, we explored the effect of truncating the essential TPX2 C-terminal 37 amino acids on Augmin localization and branching microtubule activity. First, we depleted LLC-Pk1 cells of the Augmin subunit HAUS6 and ...


Mxa Is A Novel Regulator Of Endosome-Associated Transcriptional Signaling By Bone Morphogenetic Proteins 4 And 9 (Bmp4 And Bmp9), Huijuan Yuan, Pravin B. Sehgal Nov 2016

Mxa Is A Novel Regulator Of Endosome-Associated Transcriptional Signaling By Bone Morphogenetic Proteins 4 And 9 (Bmp4 And Bmp9), Huijuan Yuan, Pravin B. Sehgal

NYMC Faculty Publications

There is confusion about the role that IFN-α plays in the pathogenesis of pulmonary arterial hypertension (PAH) with different investigators reporting a causative or a protective role. There is now clear evidence in PAH pathogenesis for the involvement of BMP4 and BMP9 signaling, and its disruption by mutations in BMPR2. In the present study, we investigated MxA, an IFN-α-inducible cytoplasmic dynamin-family GTPase for effects on BMP4/9 signaling, including in the presence of PAH-disease-associated mutants of BMPR2. In human pulmonary arterial endothelial cells (HPAECs), IFN-α-induced endogenous as well as exogenously expressed MxA was associated with endosomes that aligned alongside microtubules ...


Roles Of The Mother Centriole Appendage Protein Cenexin In Microtubule Organization During Cell Migration And Cell Division: A Dissertation, Hui-Fang Hung Aug 2016

Roles Of The Mother Centriole Appendage Protein Cenexin In Microtubule Organization During Cell Migration And Cell Division: A Dissertation, Hui-Fang Hung

GSBS Dissertations and Theses

Epithelial cells are necessary building blocks of the organs they line. Their apicalbasolateral polarity, characterized by an asymmetric distribution of cell components along their apical-basal axis, is a requirement for normal organ function. Although the centrosome, also known as the microtubule organizing center, is important in establishing cell polarity the mechanisms through which it achieves this remain unclear. It has been suggested that the centrosome influences cell polarity through microtubule cytoskeleton organization and endosome trafficking. In the first chapter of this thesis, I summarize the current understanding of the mechanisms regulating cell polarity and review evidence for the role of ...


An In Vivo Study Of Cortical Dynein Dynamics And Its Contribution To Microtubule Sliding In The Midzone, Heather M. Jordan Jan 2016

An In Vivo Study Of Cortical Dynein Dynamics And Its Contribution To Microtubule Sliding In The Midzone, Heather M. Jordan

Masters Theses

In LLC-Pk1 cells, and most cultured mammalian cells, cell division is highly regulated to achieve equal sized daughter cells. During this process, duplicated centrosomes separate and establish a bipolar array called the mitotic spindle. The mitotic spindle is responsible for aligning the chromosomes at the metaphase plate, and separating sister chromatids during anaphase. Spindle positioning and elongation are thought to be driven by the interaction between dynamic astral microtubules and cortical dynein. Extensive research has revealed that dynein is anchored to the cortex via the highly conserved NuMA/LGN/Gαi ternary complex in metaphase and the additional PIP/PIP2/NuMA ...


Ciliary Proteins Bbs8 And Ift20 Promote Planar Cell Polarity In The Cochlea, Helen L. May-Simera, Ronald S. Petralia, Mireille Montcouquiol, Ya-Xian Wang, Katherine B. Szarama, Yun Liu, Weichun Lin, Michael R. Deans, Gregory J. Pazour, Matthew W. Kelley Feb 2015

Ciliary Proteins Bbs8 And Ift20 Promote Planar Cell Polarity In The Cochlea, Helen L. May-Simera, Ronald S. Petralia, Mireille Montcouquiol, Ya-Xian Wang, Katherine B. Szarama, Yun Liu, Weichun Lin, Michael R. Deans, Gregory J. Pazour, Matthew W. Kelley

Program in Molecular Medicine Publications and Presentations

Primary cilia have been implicated in the generation of planar cell polarity (PCP). However, variations in the severity of polarity defects in different cilia mutants, coupled with recent demonstrations of non-cilia-related actions of some cilia genes, make it difficult to determine the basis of these polarity defects. To address this issue, we evaluated PCP defects in cochlea from a selection of mice with mutations in cilia-related genes. Results indicated notable PCP defects, including mis-oriented hair cell stereociliary bundles, in Bbs8 and Ift20 single mutants that are more severe than in other cilia gene knockouts. In addition, deletion of either Bbs8 ...


Genetic Analysis Of Ton2 Dependent Processes In Microtubule Organization In Arabidopsis Thaliana, Samantha Nicole Atkinson Oct 2014

Genetic Analysis Of Ton2 Dependent Processes In Microtubule Organization In Arabidopsis Thaliana, Samantha Nicole Atkinson

Theses and Dissertations

Microtubules carry out many functions within the cell. They're used during mitosis and meiosis to move chromosomes to opposite sides of the cell so that cell division can occur. They're also used as structural support for the cell and are involved in establishing the cell shape. Microtubules are also able to reorient from a longitudinal orientation to a transverse orientation in response to gibberellic acid and auxin (two hormones that are involved in cell elongation). The mechanism for how this reorientation occurs is unknown. The TONNEAU2 (TON2) protein is necessary for proper microtubule organization. We looked at how ...


A Rhog/Ilk/Elmo2/Rac1 Pathways Modulates Microtubule Stability, Bradley C. Jackson Sep 2014

A Rhog/Ilk/Elmo2/Rac1 Pathways Modulates Microtubule Stability, Bradley C. Jackson

Electronic Thesis and Dissertation Repository

Integrin-linked kinase (ILK) is a widely expressed scaffold protein important for cell adhesion, migration, and phagocytosis. ILK and its interacting partner, engulfment and cell motility protein 2 (ELMO2), may also modulate microtubule dynamics. Here, I show that sustained microtubule growth and acetylated tubulin levels are reduced in the absence of ILK and, conversely, that exogenous ILK exerts a stabilizing effect on microtubules. Further, exogenous ELMO2, ras homology growth related protein (RHOG) and ras-related C3 botulinum toxin substrate 1 (RAC1) stabilize microtubules in an ILK-dependent manner. Potential downstream effectors of the effect of ILK on microtubule stability include glycogen synthase kinase- ...


Microtubule Motors Drive Nuclear Dynamics And Positioning In Developing Skeletal Muscle Cells, Meredith Hayley Wilson Jan 2014

Microtubule Motors Drive Nuclear Dynamics And Positioning In Developing Skeletal Muscle Cells, Meredith Hayley Wilson

Publicly Accessible Penn Dissertations

Dynamic interactions with the cytoskeleton are essential to move and anchor nuclei during tissue development, and defects resulting in nuclear mispositioning are often associated with human disease, such as muscular dystrophy and myopathy. Skeletal muscle cells are large syncytia formed by fusion of myoblasts, and contain hundreds of nuclei positioned regularly along the length the cell. During muscle cell development, nuclear movement in myotubes requires microtubules, but the mechanisms involved have not been elucidated. Here, we find that nuclei actively translocate through myotubes. As they translocate, they also rotate in three-dimensions. These movements require an intact microtubule cytoskeleton, which forms ...


Gbetagamma-Microtubule Mediated Mechanism Of Neuronal Differentiation, Jorge Anibal Sierra Fonseca Jan 2014

Gbetagamma-Microtubule Mediated Mechanism Of Neuronal Differentiation, Jorge Anibal Sierra Fonseca

Open Access Theses & Dissertations

Neurodegeneration, a progressive loss of nerve cells (neurons), occurs in many neurological disorders, including Alzheimer's and Parkinson's diseases, as well as in the aging brain. Disruption of microtubules in neurons and the aggregation of proteins associated with them is the hallmark of neurodegeneration. Nevertheless, the cause of this disorder is largely unknown, and no effective drugs are available to treat the disease processes. Therefore, there is a need to understand the molecular mechanisms that drive the assembly and disassembly of microtubules during neurite outgrowth and differentiation. Evidence suggests that nerve growth factor (NGF) induces neurite outgrowth from PC12 ...


Microtubule Severing At Crossover Sites By Katanin Generates Ordered Cortical Microtubule Arrays In Arabidopsis, Quan Zhang, Erica Fishel, Tyler Bertroche, Ram Dixit Nov 2013

Microtubule Severing At Crossover Sites By Katanin Generates Ordered Cortical Microtubule Arrays In Arabidopsis, Quan Zhang, Erica Fishel, Tyler Bertroche, Ram Dixit

Biology Faculty Publications & Presentations

Highlights

  • Severing primarily depolymerizes the overlying CMT at crossover sites
  • Severing probability increases nonlinearly with crossover time
  • Katanin localizes to crossover sites and is required for severing
  • Loss of katanin activity prevents the formation of coaligned CMT arrays

Summary
The noncentrosomal cortical microtubules (CMTs) of land plants form highly ordered parallel arrays that mediate cell morphogenesis by orienting cellulose deposition [1, 2 and 3]. Since new CMTs initiate from dispersed cortical sites at random orientations [4], parallel array organization is hypothesized to require selective pruning of CMTs that are not in the dominant orientation. Severing of CMTs at crossover sites ...


Plant Cytoskeleton: Della Connects Gibberellins To Microtubules, Ram Dixit Jun 2013

Plant Cytoskeleton: Della Connects Gibberellins To Microtubules, Ram Dixit

Biology Faculty Publications & Presentations

A new study reveals that DELLA proteins directly interact with the prefoldin complex, thus regulating tubulin subunit availability in a gibberellin-dependent manner. This finding provides a mechanistic link between the growth-promoting plant hormone gibberellin and cortical microtubule organization.


A Nuclear-Derived Proteinaceous Matrix Embeds The Microtubule Spindle Apparatus During Mitosis, Changfu Yao Jan 2013

A Nuclear-Derived Proteinaceous Matrix Embeds The Microtubule Spindle Apparatus During Mitosis, Changfu Yao

Graduate Theses and Dissertations

ABSTRACT<

The nucleus undergoes a dramatic reorganization as the cell prepares to segregate its duplicated chromosomes during cell division. For many years s, the prevailing view was that in open mitosis the nucleus completely disassembled during early mitotic stages, thus enabling cytoplasmic microtubules emanating from the separated centrosomes to form a mitotic spindle. This cytocentric view largely discounted any nuclear contributions to regulation of mitotic progression (Johansen and Johansen, 2009; De Souza and Osmani, 2009; Simon and Wilson, 2011; Sandquist et al., 2011). A spindle matrix has long been proposed to serve as a relatively stable or elastic molecular matrix ...


Computer Simulation And Mathematical Models Of The Noncentrosomal Plant Cortical Microtubule Cytoskeleton, Ezgi Can Eren, Natarajan Gautam, Ram Dixit Mar 2012

Computer Simulation And Mathematical Models Of The Noncentrosomal Plant Cortical Microtubule Cytoskeleton, Ezgi Can Eren, Natarajan Gautam, Ram Dixit

Biology Faculty Publications & Presentations

There is rising interest in modeling the noncentrosomal cortical microtubule cytoskeleton of plant cells, particularly its organization into ordered arrays and the mechanisms that facilitate this organization. In this review, we discuss quantitative models of this highly complex and dynamic structure both at a cellular and molecular level. We report differences in methodologies and assumptions of different models as well as their controversial results. Our review provides insights for future studies to resolve these controversies, in addition to underlining the common results between various models. We also highlight the need to compare the results from simulation and mathematical models with ...


Putting A Bifunctional Motor To Work: Insights Into The Role Of Plant Kch Kinesins, Ram Dixit Feb 2012

Putting A Bifunctional Motor To Work: Insights Into The Role Of Plant Kch Kinesins, Ram Dixit

Biology Faculty Publications & Presentations

Comment on: A novel actin-microtubule cross-linking kinesin, NtKCH, functions in cell expansion and division. [New Phytol. 2012 Feb;193(3):576-89. doi: 10.1111/j.1469-8137.2011.03944.x. ]


Single-Molecule Analysis Of The Microtubule Cross-Linking Protein Map65-1 Reveals A Molecular Mechanism For Contact-Angle-Dependent Microtubule Bundling, Amanda Tulin, Sheri Mcclerklin, Yue Huang, Ram Dixit Feb 2012

Single-Molecule Analysis Of The Microtubule Cross-Linking Protein Map65-1 Reveals A Molecular Mechanism For Contact-Angle-Dependent Microtubule Bundling, Amanda Tulin, Sheri Mcclerklin, Yue Huang, Ram Dixit

Biology Faculty Publications & Presentations

Bundling of microtubules (MTs) is critical for the formation of complex MT arrays. In land plants, the interphase cortical MTs form bundles specifically following shallow-angle encounters between them. To investigate how cells select particular MT contact angles for bundling, we used an in vitro reconstitution approach consisting of dynamic MTs and the MT-cross-linking protein MAP65-1. We found that MAP65-1 binds to MTs as monomers and inherently targets antiparallel MTs for bundling. Dwell-time analysis showed that the affinity of MAP65-1 for antiparallel overlapping MTs is about three times higher than its affinity for single MTs and parallel overlapping MTs. We also ...


Chapter 27 – Studying Plus-End Tracking At Single Molecule Resolution Using Tirf Microscopy, Ram Dixit, Jennifer L. Ross Jan 2010

Chapter 27 – Studying Plus-End Tracking At Single Molecule Resolution Using Tirf Microscopy, Ram Dixit, Jennifer L. Ross

Biology Faculty Publications & Presentations

The highly dynamic microtubule plus-ends are key sites of regulation that impact the organization and function of the microtubule cytoskeleton. Much of this regulation is performed by the microtubule plus-end tracking (+TIP) family of proteins. +TIPs are a structurally diverse group of proteins that bind to and track with growing microtubule plus-ends in cells. +TIPs regulate microtubule dynamics as well as mediate interactions between microtubule tips and other cellular structures. Most +TIPs can directly bind to microtubules in vitro; however, the mechanisms for their plus-end specificity are not fully understood. Cellular studies of +TIP activity are complicated by the fact ...


A Conserved Cam- And Radial Spoke–Associated Complex Mediates Regulation Of Flagellar Dynein Activity, Erin E. Dymek, Elizabeth F. Smith Nov 2007

A Conserved Cam- And Radial Spoke–Associated Complex Mediates Regulation Of Flagellar Dynein Activity, Erin E. Dymek, Elizabeth F. Smith

Open Dartmouth: Faculty Open Access Scholarship

For virtually all cilia and eukaryotic flagella, the second messengers calcium and cyclic adenosine monophosphate are implicated in modulating dynein- driven microtubule sliding to regulate beating. Calmodulin (CaM) localizes to the axoneme and is a key calcium sensor involved in regulating motility. Using immunoprecipitation and mass spectrometry, we identify members of a CaM-containing complex that are involved in regulating dynein activity. This complex includes flagellar-associated protein 91 (FAP91), which shares considerable sequence similarity to AAT-1, a protein originally identified in testis as an A-kinase anchor protein (AKAP)- binding protein. FAP91 directly interacts with radial spoke protein 3 (an AKAP), which ...


Calmodulin And Pf6 Are Components Of A Complex That Localizes To The C1 Microtubule Of The Flagellar Central Apparatus, Matthew J. Wargo, Erin E. Dymek, Elizabeth F. Smith Jul 2005

Calmodulin And Pf6 Are Components Of A Complex That Localizes To The C1 Microtubule Of The Flagellar Central Apparatus, Matthew J. Wargo, Erin E. Dymek, Elizabeth F. Smith

Open Dartmouth: Faculty Open Access Scholarship

Studies of flagellar motility in Chlamydomonas mutants lacking specific central apparatus components have supported the hypothesis that the inherent asymmetry of this structure provides important spatial cues for asymmetric regulation of dynein activity. These studies have also suggested that specific projections associated with the C1 and C2 central tubules make unique contributions to modulating motility; yet, we still do not know the identities of most polypeptides associated with the central tubules. To identify components of the C1a projection, we took an immunoprecipitation approach using antibodies generated against PF6. The pf6 mutant lacks the C1a projection and possesses flagella that only ...


Analysis Of Microtubule Sliding Patterns In Chlamydomonas Flagellar Axonemes Reveals Dynein Activity On Specific Doublet Microtubules, M. J. Wargo, Mark A. Mcpeek, Elizabeth F. Smith Jan 2004

Analysis Of Microtubule Sliding Patterns In Chlamydomonas Flagellar Axonemes Reveals Dynein Activity On Specific Doublet Microtubules, M. J. Wargo, Mark A. Mcpeek, Elizabeth F. Smith

Open Dartmouth: Faculty Open Access Scholarship

Generating the complex waveforms characteristic of beating eukaryotic cilia and flagella requires spatial regulation of dynein-driven microtubule sliding. To generate bending, one prediction is that dynein arms alternate between active and inactive forms on specific subsets of doublet microtubules. Using an in vitro microtubule sliding assay combined with a structural approach, we determined that ATP induces sliding between specific subsets of doublet microtubules, apparently capturing one phase of the beat cycle. These studies were also conducted using high Ca2+ conditions. InChlamydomonas, high Ca2+ induces changes in waveform which are predicted to result from regulating dynein

activity on specific microtubules. Our ...


Minus-End Capture Of Preformed Kinetochore Fibers Contributes To Spindle Morphogenesis, Alexey Khodjakov, Lily Copenagle, Michael B. Gordon, Duane A. Compton, Tarun M. Kapoor Mar 2003

Minus-End Capture Of Preformed Kinetochore Fibers Contributes To Spindle Morphogenesis, Alexey Khodjakov, Lily Copenagle, Michael B. Gordon, Duane A. Compton, Tarun M. Kapoor

Open Dartmouth: Faculty Open Access Scholarship

Near-simultaneous three-dimensional fluorescence/differential interference contrast microscopy was used to follow the behavior of microtubules and chromosomes in living alpha-tubulin/GFP-expressing cells after inhibition of the mitotic kinesin Eg5 with monastrol. Kinetochore fibers (K-fibers) were frequently observed forming in association with chromosomes both during monastrol treatment and after monastrol removal. Surprisingly, these K-fibers were oriented away from, and not directly connected to, centrosomes and incorporated into the spindle by the sliding of their distal ends toward centrosomes via a NuMA-dependent mechanism. Similar preformed K-fibers were also observed during spindle formation in untreated cells. In addition, upon monastrol removal, centrosomes established ...


Asymmetry Of The Central Apparatus Defines The Location Of Active Microtubule Sliding In Chlamydomonas Flagella, Matthew J. Wargo, Elizabeth F. Smith Jan 2003

Asymmetry Of The Central Apparatus Defines The Location Of Active Microtubule Sliding In Chlamydomonas Flagella, Matthew J. Wargo, Elizabeth F. Smith

Open Dartmouth: Faculty Open Access Scholarship

Regulation of ciliary and flagellar motility requires spatial control of dynein-driven microtubule sliding. However, the mechanism for regulating the location and symmetry of dynein activity is not understood. One hypothesis is that the asymmetrically organized central apparatus, through interactions with the radial spokes, transmits a signal to regulate dynein-driven microtubule sliding between subsets of doublet microtubules. Based on this model, we hypothesized that the orientation of the central apparatus defines positions of active microtubule sliding required to control bending in the axoneme. To test this, we induced microtubule sliding in axonemes isolated from wild-type and mutant Chlamydomonas cells, and then ...


Atp-Dependent Formation And Motility Of Aster-Like Structures With Isolated Calf Brain Microtubule Proteins., Richard C. Weisenberg, Robert D. Allen, Shinya Inoue Mar 1986

Atp-Dependent Formation And Motility Of Aster-Like Structures With Isolated Calf Brain Microtubule Proteins., Richard C. Weisenberg, Robert D. Allen, Shinya Inoue

Open Dartmouth: Faculty Open Access Scholarship

Microtubule proteins isolated from calf brain will undergo gelation-contraction in the presence of ATP. We have now examined this process by video-enhanced contrast microscopy. After ATP addition to steady-state microtubules, slow (1-5 micron/min), linear movements of particles and microtubules toward aggregation centers occur. The resulting structures resemble mitotic spindle asters. During the time when gel contraction occurs, asters move (at 1-5 micron/min) toward other nearby asters. This is accompanied by the apparent shortening of the microtubules running between the asters. This is the first example of isolated microtubules undergoing a process that has similarities to half-spindle shortening during ...


Chlamydomonas Moewusii Pairing: Optimal Conditions And Drug Effects, Thomas Michael Lembo Jan 1978

Chlamydomonas Moewusii Pairing: Optimal Conditions And Drug Effects, Thomas Michael Lembo

Biology Master’s Theses

The effect of various mating conditions on the pairing percentages in Chlamydomonas moewusii were determined. A pairing percentage of 43% was obtained when gametes induced at 21°c were shifted to a mating temperature of 19°c for 1 hour. The lowest pairing percentage was obtained when cells were induced at 30°c and shifted to 19°c for 1 hour. The anti-microtubule agent colchicine and the anti-microfilament agent cytochalasin B were employed to determine their effect on pairing in C. moewusii. Both drugs demonstrated an inhibitory effect on pairing in Chlamydomonas. The inhibition of gametic pairing in cells treated ...