scholarly journals Cargo crowding, stationary clusters and dynamical reservoirs in axonal transport

2021 ◽  
Author(s):  
Vinod Kumar ◽  
Amruta Vasudevan ◽  
Keertana Venkatesh ◽  
Reshma Maiya ◽  
Parul Sood ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Molecular Motors ◽  
Experimental System ◽  
C Elegans ◽  
On Demand ◽  
Motion State ◽  
State Switching ◽  
Cargo Transport ◽  
Functional Relevance

AbstractMolecular motors drive the directed transport of presynaptic vesicles along the narrow axons of nerve cells. Stationary clusters of such vesicles are a prominent feature of axonal transport, but little is known about their physiological and functional relevance. Here, we develop a simulation model describing key features of axonal cargo transport with a view to addressing this question, benchmarking the model against our experiments in the touch neurons of C. elegans. Our simulations provide for multiple microtubule tracks and varied cargo motion states while also incorporating cargo-cargo interactions. Our model also incorporates obstacles to vesicle transport in the form of microtubule ends, stalled vesicles, and stationary mitochondria. We devise computational methodologies to simulate both axonal bleaching and axotomy, showing that our results reproduce the properties of both moving as well as stationary cargo in vivo. Increasing vesicle numbers leads to larger and more long-lived stationary clusters of vesicular cargo. Vesicle clusters are dynamically stable, explaining why they are ubiquitously seen. Modulating the rates of cargo motion-state switching allows cluster lifetimes and flux to be tuned both in simulations and experiments. We demonstrate, both in simulations and in an experimental system, that suppressing reversals leads to larger stationary vesicle clusters being formed while also reducing flux. Our simulation results support the view that the physiological significance of clusters is located in their role as dynamic reservoirs of cargo vesicles, capable of being released or sequestered on demand.

scholarly journals Topoisomerases I and II facilitate condensin DC translocation to organize and repress X chromosomes in C. elegans

2021 ◽  
Author(s):  
Ana Karina Morao ◽  
Jun Kim ◽  
Daniel Obaji ◽  
Siyu Sun ◽  
Sevinc Ercan
Keyword(s):  
Long Range ◽  
X Chromosome ◽  
Molecular Motors ◽  
Topoisomerase Ii ◽  
Dna Looping ◽  
Loop Formation ◽  
X Chromosomes ◽  
C Elegans ◽  
And Control

Condensin complexes are evolutionarily conserved molecular motors that translocate along DNA and form loops. While condensin-mediated DNA looping is thought to direct the chain-passing activity of topoisomerase II to separate sister chromatids, it is not known if topological constraints in turn regulate loop formation in vivo. Here we applied auxin inducible degradation of topoisomerases I and II to determine how DNA topology affects the translocation of an X chromosome specific condensin that represses transcription for dosage compensation in C. elegans (condensin DC). We found that both topoisomerases colocalize with condensin DC and control its movement at different genomic scales. TOP-2 depletion hindered condensin DC translocation over long distances, resulting in accumulation around its X-specific recruitment sites and shorter Hi-C interactions. In contrast, TOP-1 depletion did not affect long-range spreading but resulted in accumulation of condensin DC within expressed gene bodies. Both TOP-1 and TOP-2 depletions resulted in X chromosome transcriptional upregulation indicating that condensin DC translocation at both scales is required for its function in gene repression. Together the distinct effects of TOP-1 and TOP-2 on condensin DC distribution revealed two distinct modes of condensin DC association with chromatin: long-range translocation that requires decatenation/unknotting of DNA and short-range translocation across genes that requires resolution of transcription-induced supercoiling.

scholarly journals Condensin DC spreads linearly and bidirectionally from recruitment sites to create loop-anchored TADs in C. elegans

2021 ◽  
Author(s):  
David Sebastian Jimenez ◽  
Jun Kim ◽  
Bhavana Ragipani ◽  
Bo Zhang ◽  
Lena Annika Street ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
X Chromosome ◽  
Molecular Motors ◽  
Sequence Motif ◽  
X Chromosomes ◽  
C Elegans ◽  
Eukaryotic Chromosome ◽  
Multiple Copies

AbstractCondensins are molecular motors that compact DNA for chromosome segregation and gene regulation. In vitro experiments have begun to elucidate the mechanics of condensin function but how condensin loading and translocation along DNA controls eukaryotic chromosome structure in vivo remains poorly understood. To address this question, we took advantage of a specialized condensin, which organizes the 3D conformation of X chromosomes to mediate dosage compensation (DC) in C. elegans. Condensin DC is recruited and spreads from a small number of recruitment elements on the X chromosome (rex). We found that ectopic insertion of rex sites on an autosome leads to bidirectional spreading of the complex over hundreds of kilobases. On the X chromosome, strong rex sites contain multiple copies of a 12-bp sequence motif and act as TAD borders. Inserting a strong rex and ectopically recruiting the complex on the X chromosome or an autosome creates a loop-anchored TAD. Unlike the CTCF system, which controls TAD formation by cohesin, direction of the 12-bp motif does not control the specificity of loops. In an X;V fusion chromosome, condensin DC linearly spreads into V and increases 3D DNA contacts, but fails to form TADs in the absence of rex sites. Finally, we provide in vivo evidence for the loop extrusion hypothesis by targeting multiple dCas9-Suntag complexes to an X chromosome repeat region. Consistent with linear translocation along DNA, condensin DC accumulates at the block site. Together, our results support a model whereby strong rex sites act as insulation elements through recruitment and bidirectional spreading of condensin DC molecules and form loop-anchored TADs.

An on-demand gas segmented flow generator with high spatiotemporal resolution for in vivo analysis of neuronal response in C. elegans

Lab on a Chip ◽  
2016 ◽  
Vol 16 (20) ◽  
pp. 4020-4027 ◽  
Author(s):  
Liang Hu ◽  
Anle Ge ◽  
Xixian Wang ◽  
Shanshan Wang ◽  
Yue Gao ◽  
...  
Keyword(s):  
Neuronal Response ◽  
Neuronal Responses ◽  
Segmented Flow ◽  
Spatiotemporal Resolution ◽  
C Elegans ◽  
On Demand ◽  
High Spatiotemporal Resolution ◽  
Flow Generator ◽  
In Vivo Analysis

We report an on-demand gas segmented flow generator with high spatiotemporal resolution to analyze neuronal responses of C. elegans to fluctuating gas cues.

scholarly journals Myosin Va binding to neurofilaments is essential for correct myosin Va distribution and transport and neurofilament density

2002 ◽  
Vol 159 (2) ◽  
pp. 279-290 ◽  
Author(s):  
Mala V. Rao ◽  
Linda J. Engle ◽  
Panaiyur S. Mohan ◽  
Aidong Yuan ◽  
Dike Qiu ◽  
...  
Keyword(s):  
Normal Distribution ◽  
Axonal Transport ◽  
Immunoelectron Microscopy ◽  
Molecular Motors ◽  
Peripheral Nerves ◽  
Molecular Motor ◽  
Neurofilament Proteins ◽  
Myosin Va ◽  
Slow Transport

The identification of molecular motors that modulate the neuronal cytoskeleton has been elusive. Here, we show that a molecular motor protein, myosin Va, is present in high proportions in the cytoskeleton of mouse CNS and peripheral nerves. Immunoelectron microscopy, coimmunoprecipitation, and blot overlay analyses demonstrate that myosin Va in axons associates with neurofilaments, and that the NF-L subunit is its major ligand. A physiological association is indicated by observations that the level of myosin Va is reduced in axons of NF-L–null mice lacking neurofilaments and increased in mice overexpressing NF-L, but unchanged in NF-H–null mice. In vivo pulse-labeled myosin Va advances along axons at slow transport rates overlapping with those of neurofilament proteins and actin, both of which coimmunoprecipitate with myosin Va. Eliminating neurofilaments from mice selectively accelerates myosin Va translocation and redistributes myosin Va to the actin-rich subaxolemma and membranous organelles. Finally, peripheral axons of dilute-lethal mice, lacking functional myosin Va, display selectively increased neurofilament number and levels of neurofilament proteins without altering axon caliber. These results identify myosin Va as a neurofilament-associated protein, and show that this association is essential to establish the normal distribution, axonal transport, and content of myosin Va, and the proper numbers of neurofilaments in axons.

In silico and In vivo Evaluation of Oxidative Stress Inhibitors Against Parkinson`s Disease using the C. elegans Model

2020 ◽  
Vol 23 (8) ◽  
pp. 814-826
Author(s):  
Pradeep Hanumanthappa ◽  
Arpitha Ashok ◽  
Inderjit Prakash ◽  
Carmel I. Priya ◽  
Julie Zinzala ◽  
...  
Keyword(s):  
Neuronal Death ◽  
Neurodegenerative Disorder ◽  
In Vivo Evaluation ◽  
Neuroprotective Effects ◽  
Ample Evidence ◽  
C Elegans ◽  
Rational Drug ◽  
Cullin 3 ◽  
Anti Oxidant

Background: Parkinson’s disease ranks second, after Alzheimer’s as the major neurodegenerative disorder, for which no cure or disease-modifying therapies exist. Ample evidence indicate that PD manifests as a result of impaired anti-oxidative machinery leading to neuronal death wherein Cullin-3 has ascended as a potential therapeutic target for diseases involving damaged anti-oxidative machinery. Objective: The design of target specific inhibitors for the Cullin-3 protein might be a promising strategy to increase the Nrf2 levels and to decrease the possibility of “off-target” toxic properties. Methods: In the present study, an integrated computational and wet lab approach was adopted to identify small molecule inhibitors for Cullin-3. The rational drug designing process comprised homology modeling and derivation of the pharmacophore for Cullin-3, virtual screening of Zinc natural compound database, molecular docking and Molecular dynamics based screening of ligand molecules. In vivo validations of an identified lead compound were conducted in the PD model of C. elegans. Results and Discussion: Our strategy yielded a potential inhibitor; (Glide score = -12.31), which was evaluated for its neuroprotective efficacy in the PD model of C. elegans. The inhibitor was able to efficiently defend against neuronal death in PD model of C. elegans and the neuroprotective effects were attributed to its anti-oxidant activities, supported by the increase in superoxide dismutase, catalase and the diminution of acetylcholinesterase and reactive oxygen species levels. In addition, the Cullin-3 inhibitor significantly restored the behavioral deficits in the transgenic C. elegans. Conclusion: Taken together, these findings highlight the potential utility of Cullin-3 inhibition to block the persistent neuronal death in PD. Further studies focusing on Cullin-3 and its mechanism of action would be interesting.

Delivery Efficacy Differences of Intravenous and Intraperitoneal Injection of Exosomes: Perspectives from Tracking Dye Labeled and MiRNA Encapsulated Exosomes

2020 ◽  
Vol 17 (3) ◽  
pp. 186-194 ◽  
Author(s):  
Xueying Zhou ◽  
Zhelong Li ◽  
Wenqi Sun ◽  
Guodong Yang ◽  
Changyang Xing ◽  
...  
Keyword(s):  
Intraperitoneal Injection ◽  
Drug Delivery Vehicles ◽  
C Elegans ◽  
Administration Routes ◽  
In Vivo Distribution ◽  
Obesity Therapy ◽  
Delivery Vehicles ◽  
Visceral Adipose ◽  
Mirna Abundance

Background: Exosomes are cell-derived nanovesicles that play vital roles in intercellular communication. Recently, exosomes are recognized as promising drug delivery vehicles. Up till now, how the in vivo distribution of exosomes is affected by different administration routes has not been fully understood. Methods: In the present study, in vivo distribution of exosomes following intravenous and intraperitoneal injection approaches was systemically analyzed by tracking the fluorescence-labeled exosomes and qPCR analysis of C. elegans specific miRNA abundance delivered by exosomes in different organs. Results: The results showed that exosomes administered through tail vein were mostly taken up by the liver, spleen and lungs while exosomes injected intraperitoneally were more dispersedly distributed. Besides the liver, spleen, and lungs, intraperitoneal injection effectively delivered exosomes into the visceral adipose tissue, making it a promising strategy for obesity therapy. Moreover, the results from fluorescence tracking and qPCR were slightly different, which could be explained by systemic errors. Conclusion: Together, our study reveals that different administration routes cause a significant differential in vivo distribution of exosomes, suggesting that optimization of the delivery route is prerequisite to obtain rational delivery efficiency in detailed organs.

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