scholarly journals Tau, XMAP215/Msps and Eb1 co-operate interdependently to regulate microtubule polymerisation and bundle formation in axons

PLoS Genetics ◽  
2021 ◽  
Vol 17 (7) ◽  
pp. e1009647
Author(s):  
Ines Hahn ◽  
Andre Voelzmann ◽  
Jill Parkin ◽  
Judith B. Fülle ◽  
Paula G. Slater ◽  
...  
Keyword(s):  
Axon Growth ◽  
Axon Development ◽  
Conceptual Explanations ◽  
Mutant Phenotypes ◽  
In Cells

The formation and maintenance of microtubules requires their polymerisation, but little is known about how this polymerisation is regulated in cells. Focussing on the essential microtubule bundles in axons of Drosophila and Xenopus neurons, we show that the plus-end scaffold Eb1, the polymerase XMAP215/Msps and the lattice-binder Tau co-operate interdependently to promote microtubule polymerisation and bundle organisation during axon development and maintenance. Eb1 and XMAP215/Msps promote each other’s localisation at polymerising microtubule plus-ends. Tau outcompetes Eb1-binding along microtubule lattices, thus preventing depletion of Eb1 tip pools. The three factors genetically interact and show shared mutant phenotypes: reductions in axon growth, comet sizes, comet numbers and comet velocities, as well as prominent deterioration of parallel microtubule bundles into disorganised curled conformations. This microtubule curling is caused by Eb1 plus-end depletion which impairs spectraplakin-mediated guidance of extending microtubules into parallel bundles. Our demonstration that Eb1, XMAP215/Msps and Tau co-operate during the regulation of microtubule polymerisation and bundle organisation, offers new conceptual explanations for developmental and degenerative axon pathologies.

scholarly journals Tau, XMAP215/Msps and Eb1 jointly regulate microtubule polymerisation and bundle formation in axons

2020 ◽  
Author(s):  
Ines Hahn ◽  
Andre Voelzmann ◽  
Jill Parkin ◽  
Judith Fuelle ◽  
Paula G Slater ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Functional Unit ◽  
Axon Growth ◽  
Loss Of Function ◽  
Cellular Processes ◽  
Axon Development ◽  
Key Players ◽  
Summary Statement ◽  
High Age ◽  
Mutant Phenotypes

AbstractAxons are the enormously long cable-like cellular processes of neurons that wire nervous systems and have to survive for up to a century in humans. We lose ~40% of axons towards high age and far more in neurodegenerative diseases. Sustaining axons requires axonal transport and dynamic morphogenetic changes, both crucially dependent on bundles of microtubules that run all along axons. How polymerisation is regulated to form, repair and replace microtubules in these bundles during axon development and maintenance is virtually unknown. Here, we show in axons of Drosophila and Xenopus neurons alike that Eb1, XMAP215/Msps and Tau are key players which operate as one functional unit to promote microtubule polymerisation. Eb1 and XMAP215/Msps are interdependent core factors at the microtubule tip, whereas Tau outcompetes Eb1 binding at microtubule lattices, thus preventing its pool depletion at polymerising plus ends. In agreement with their closely interwoven functions, the three factors show the same combination of axonal loss-of-function mutant phenotypes including: (1) reduced microtubule polymerisation dynamics and shorter axon growth, indicating their importance for upholding microtubule mass in axons; (2) prominent deterioration of parallel microtubule bundles into disorganised curled conformations, indicating their key roles in promoting essential axonal architecture. We show the latter to occur through Eb1- and spectraplakin-dependent guidance of extending microtubules. We conclude that Eb1, XMAP215/Msps and Tau jointly promote microtubule polymerisation, important to regulate the quantity and bundled organisation of microtubules and offering new ways to think about developmental and degenerative axon pathologies and how to treat them.Summary statementEb1, XMAP215 and tau operate as a functional unit in axons to promote the polymerisation of microtubules and their organisation into the parallel bundles essential for axonal transport.

Sensory activity affects sensory axon development in C. elegans

Development ◽  
1999 ◽  
Vol 126 (9) ◽  
pp. 1891-1902 ◽  
Author(s):  
E.L. Peckol ◽  
J.A. Zallen ◽  
J.C. Yarrow ◽  
C.I. Bargmann
Keyword(s):  
Nervous System ◽  
Molecular Mechanisms ◽  
Sensory Deprivation ◽  
Axon Growth ◽  
System Structure ◽  
Sensory Axon ◽  
C Elegans ◽  
Sensory Axons ◽  
Axon Development ◽  
Sensory Activity

The simple nervous system of the nematode C. elegans consists of 302 neurons with highly reproducible morphologies, suggesting a hard-wired program of axon guidance. Surprisingly, we show here that sensory activity shapes sensory axon morphology in C. elegans. A class of mutants with deformed sensory cilia at their dendrite endings have extra axon branches, suggesting that sensory deprivation disrupts axon outgrowth. Mutations that alter calcium channels or membrane potential cause similar defects. Cell-specific perturbations of sensory activity can cause cell-autonomous changes in axon morphology. Although the sensory axons initially reach their targets in the embryo, the mutations that alter sensory activity cause extra axon growth late in development. Thus, perturbations of activity affect the maintenance of sensory axon morphology after an initial pattern of innervation is established. This system provides a genetically tractable model for identifying molecular mechanisms linking neuronal activity to nervous system structure.

scholarly journals Molecular cloning and characterization of a transcription factor for the copia retrotransposon with homology to the BTB-containing lola neurogenic factor.

1997 ◽  
Vol 17 (1) ◽  
pp. 482-494 ◽  
Author(s):  
L Cavarec ◽  
S Jensen ◽  
J F Casella ◽  
S A Cristescu ◽  
T Heidmann
Keyword(s):  
Transcription Factor ◽  
Transcriptional Activation ◽  
Axon Growth ◽  
Expression Vectors ◽  
Recognition Sequence ◽  
Enhancer Sequence ◽  
Cells In Culture ◽  
Copia Retrotransposon ◽  
Gel Shift ◽  
In Cells

By transfection experiments, we previously identified a 72-bp enhancer sequence within the Drosophila copia retrotransposon which is involved in the control of the transcription level of this mobile element in cells in culture. Gel shift assays with nuclear extracts from Drosophila hydei-derived DH-33 cells further demonstrated specific interactions of at least two nuclear factors with this enhancer sequence. Using this sequence as a probe for the screening of an expression cDNA library that we constructed from DH-33 cells RNA, we have isolated a cDNA clone encoding a 110-kDa protein with features common to those of known transcription factors; these include a two-zinc-finger motif at the C terminus, three glutamine-rich domains in the presumptive activation domain of the protein, and an N-terminal domain which shares homology with the Bric-à-brac, Tramtrack, and Broad-Complex BTB boxes. The precise DNA recognition sequence for this transcription factor has been determined by both gel shift assays and footprinting experiments with a recombinant protein made in bacteria. The functionality of the cloned element was demonstrated upon transcriptional activation of copia reporter genes, as well as of a minimal promoter coupled with the identified target DNA sequence, in cotransfection assays in cells in culture with an expression vector for the cloned factor. Southern blot and nucleotide sequence analyses revealed a related gene in Drosophila melanogaster (the lola gene) previously identified by a genetic approach as involved in axon growth and guidance. Transfection assays in cells in culture with lola gene expression vectors and in situ hybridization experiments with lola gene mutants finally provided evidence that the copia retrotransposon is regulated by this neurogenic gene in D.melanogaster, with a repressor effect in the central nervous systems of the embryos.

scholarly journals Temperature-Dependent Conjugative Transfer of R27: Role of Chromosome- and Plasmid-Encoded Hha and H-NS Proteins

2005 ◽  
Vol 187 (12) ◽  
pp. 3950-3959 ◽  
Author(s):  
Núria Forns ◽  
Rosa C. Baños ◽  
Carlos Balsalobre ◽  
Antonio Juárez ◽  
Cristina Madrid
Keyword(s):  
Open Reading Frame ◽  
Nonpermissive Temperature ◽  
Multiple Antibiotic Resistance ◽  
Temperature Dependent ◽  
Reading Frame ◽  
Transfer Region ◽  
Relevant Role ◽  
Mutant Phenotypes ◽  
In Cells

ABSTRACT IncHI plasmids encode multiple-antibiotic resistance in Salmonella enterica serovar Typhi. These plasmids have been considered to play a relevant role in the persistence and reemergence of this microorganism. The IncHI1 plasmid R27, which can be considered the prototype of IncHI plasmids, is thermosensitive for transfer. Conjugation frequency is highest at low temperature (25 to 30°C), decreasing when temperature increases. R27 codifies an H-NS-like protein (open reading frame 164 [ORF164]) and an Hha-like protein (ORF182). The H-NS and Hha proteins participate in the thermoregulation of gene expression in Escherichia coli. Here we investigated the hypothetical role of such proteins in thermoregulation of R27 conjugation. At a nonpermissive temperature (33°C), transcription of several ORFs in both transfer region 1 (Tra1) and Tra2 from R27 is upregulated in cells depleted of Hha-like and H-NS-like proteins. Both chromosome- and plasmid-encoded Hha and H-NS proteins appear to potentially modulate R27 transfer. The function of R27-encoded Hha-like and H-NS proteins is not restricted to modulation of R27 transfer. Different mutant phenotypes associated with both chromosomal hha and hns mutations are compensated in cells harboring R27.

Characterization of presynaptic septin complexes in mammalian hippocampal neurons

2011 ◽  
Vol 392 (8-9) ◽  
pp. 739-749 ◽  
Author(s):  
Christopher W. Tsang ◽  
Mathew P. Estey ◽  
Jessica E. DiCiccio ◽  
Hong Xie ◽  
Dana Patterson ◽  
...  
Keyword(s):  
Brain Tissue ◽  
Neurological Disorders ◽  
Hippocampal Neurons ◽  
Axon Growth ◽  
Vesicle Traffic ◽  
Axon Development ◽  
Mammalian Tissues ◽  
Unique Composition ◽  
Cultured Nerve Cells

Abstract Septins are GTPases that form heteromeric complexes and are linked to neurological disorders. Although several septin subcomplexes have been reported in various mammalian tissues, the cellular and subcellular distribution of these complexes is largely unexplored. Using antibodies against ten mammalian septins, we show that septins diverge with respect to their tissue distribution implying that septin complexes in various tissues have unique composition. Although all ten septins examined were expressed in brain tissue, we describe septin complex(es) including SEPT3, SEPT5, SEPT6, SEPT7 and SEPT11 that could be functional within the presynapse because, unlike other septins they: (1) showed an increase in expression from embryonic day 15 to post-natal day 70, (2) were abundantly expressed in axons and growth cones of developing hippocampal neurons, (3) were found in presynaptic terminals of mature synapses, (4) were enriched in a preparation of synaptic vesicles and (5) immunoprecipitated together from brain tissue and cultured nerve cells. Knockdown of SEPT5 or SEPT7 in developing hippocampal neurons impaired axon growth. Because septins are functionally linked to the cytoskeleton and vesicle traffic, presynaptic neuronal septin complexes could be important for ensuring proper axon development and neurotransmitter release.

scholarly journals Autophagy is required for midbrain dopaminergic axon development and their responsiveness to guidance cues

2020 ◽  
Author(s):  
M.S. Profes ◽  
A. Saghatelyan ◽  
M. Lévesque
Keyword(s):  
Molecular Mechanisms ◽  
Axon Growth ◽  
Brain Functions ◽  
Guidance Cues ◽  
Axon Development ◽  
Wide Range ◽  
Growth Guidance ◽  
Circuit Formation

AbstractMesodiencephalic dopamine (mDA) neurons play a wide range of brain functions. Distinct subtypes of mDA neurons regulate these functions but the molecular mechanisms that drive the mDA circuit formation are largely unknown. Here we show that autophagy, the main recycling cellular pathway, is present in the growth cones of developing mDA neurons and its level changes dynamically in response to guidance cues. To characterize the role of autophagy in mDA axon growth/guidance, we knocked-out (KO) essential autophagy genes (Atg12, Atg5) in mice mDA neurons. Autophagy deficient mDA axons exhibit axonal swellings and decreased branching both in vitro and in vivo, likely due to aberrant microtubule looping. Strikingly, deletion of autophagy-related genes, blunted completely the response of mDA neurons to chemo-repulsive and chemo-attractive guidance cues. Our data demonstrate that autophagy plays a central role in regulating mDA neurons development, orchestrating axonal growth and guidance.

scholarly journals From whole organism to ultrastructure: progress in axonal imaging for decoding circuit development

Development ◽  
2021 ◽  
Vol 148 (18) ◽  
Author(s):  
Cory J. Weaver ◽  
Fabienne E. Poulain
Keyword(s):  
Neural Circuit ◽  
Super Resolution ◽  
Axon Growth ◽  
Light Sheet ◽  
Growth Cones ◽  
Novel Technologies ◽  
Future Technology ◽  
Axon Development ◽  
Circuit Formation ◽  
Super Resolution Microscopy

ABSTRACT Since the pioneering work of Ramón y Cajal, scientists have sought to unravel the complexities of axon development underlying neural circuit formation. Micrometer-scale axonal growth cones navigate to targets that are often centimeters away. To reach their targets, growth cones react to dynamic environmental cues that change in the order of seconds to days. Proper axon growth and guidance are essential to circuit formation, and progress in imaging has been integral to studying these processes. In particular, advances in high- and super-resolution microscopy provide the spatial and temporal resolution required for studying developing axons. In this Review, we describe how improved microscopy has revolutionized our understanding of axonal development. We discuss how novel technologies, specifically light-sheet and super-resolution microscopy, led to new discoveries at the cellular scale by imaging axon outgrowth and circuit wiring with extreme precision. We next examine how advanced microscopy broadened our understanding of the subcellular dynamics driving axon growth and guidance. We finally assess the current challenges that the field of axonal biology still faces for imaging axons, and examine how future technology could meet these needs.

Cytoplasmic Tubules in Cells Infected with Laryngotracheitis Virus

1969 ◽  
Vol 27 ◽  
pp. 376-377
Author(s):  
A. M. Watrach
Keyword(s):  
Tissue Culture ◽  
Small Proportion ◽  
Chicken Embryo ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
Morphologic Characteristics ◽  
Infectious Laryngotracheitis ◽  
Laryngotracheitis Virus ◽  
In Cells

During a study of the development of infectious laryngotracheitis (LT) virus in tissue culture cells, unusual tubular formations were found in the cytoplasm of a small proportion of the affected cells. It is the purpose of this report to describe the morphologic characteristics of the tubules and to discuss their possible association with the development of virus.The source and maintenance of the strain of LT virus have been described. Prior to this study, the virus was passed several times in chicken embryo kidney (CEK) tissue culture cells.

Effect of Some Metabolic Inhibitors on Vinblastine-Induced Ribosomal-Granular Material Complexes

1971 ◽  
Vol 29 ◽  
pp. 548-549
Author(s):  
Awtar Krishan ◽  
Dora Hsu
Keyword(s):  
Granular Material ◽  
Rna Synthesis ◽  
Culture Medium ◽  
Actinomycin D ◽  
Metabolic Inhibitors ◽  
Protein And Rna Synthesis ◽  
Apparent Reduction ◽  
Plant Alkaloids ◽  
In Cells

Cells exposed to antitumor plant alkaloids, vinblastine and vincristine sulfate have large proteinacious crystals and complexes of ribosomes, helical polyribosomes and electron-dense granular material (ribosomal complexes) in their cytoplasm, Binding of H3-colchicine by the in vivo crystals shows that they contain microtubular proteins. Association of ribosomal complexes with the crystals suggests that these structures may be interrelated.In the present study cultured human leukemic lymphoblasts (CCRF-CEM), were incubated with protein and RNA-synthesis inhibitors, p. fluorophenylalanine, puromycin, cycloheximide or actinomycin-D before the addition of crystal-inducing doses of vinblastine to the culture medium. None of these compounds could completely prevent the formation of the ribosomal complexes or the crystals. However, in cells pre-incubated with puromycin, cycloheximide, or actinomycin-D, a reduction in the number and size of the ribosomal complexes was seen. Large helical polyribosomes were absent in the ribosomal complexes of cells treated with puromycin, while in cells exposed to cycloheximide, there was an apparent reduction in the number of ribosomes associated with the ribosomal complexes (Fig. 2).

Detection of Nucleic Acids in Cells or Tissue Sections Using In situ Polymerase Chain Reaction (PCR)

1996 ◽  
Vol 54 ◽  
pp. 16-17
Author(s):  
J. R. Hully ◽  
K. R. Luehrsen ◽  
K. Aoyagi ◽  
C. Shoemaker ◽  
R. Abramson
Keyword(s):  
Nucleic Acids ◽  
Viral Infections ◽  
Anatomical Location ◽  
Rt Pcr ◽  
Reverse Transcription Pcr ◽  
Cellular Source ◽  
Gene Transcripts ◽  
Initial Description ◽  
In Cells

The development of PCR technology has greatly accelerated medical research at the genetic and molecular levels. Until recently, the inherent sensitivity of this technique has been limited to isolated preparations of nucleic acids which lack or at best have limited morphological information. With the obvious exception of cell lines, traditional PCR or reverse transcription-PCR (RT-PCR) cannot identify the cellular source of the amplified product. In contrast, in situ hybridization (ISH) by definition, defines the anatomical location of a gene and/or it’s product. However, this technique lacks the sensitivity of PCR and cannot routinely detect less than 10 to 20 copies per cell. Consequently, the localization of rare transcripts, latent viral infections, foreign or altered genes cannot be identified by this technique. In situ PCR or in situ RT-PCR is a combination of the two techniques, exploiting the sensitivity of PCR and the anatomical definition provided by ISH. Since it’s initial description considerable advances have been made in the application of in situ PCR, improvements in protocols, and the development of hardware dedicated to in situ PCR using conventional microscope slides. Our understanding of the importance of viral latency or viral burden in regards to HIV, HPV, and KSHV infections has benefited from this technique, enabling detection of single viral copies in cells or tissue otherwise thought to be normal. Clearly, this technique will be useful tool in pathobiology especially carcinogenesis, gene therapy and manipulations, the study of rare gene transcripts, and forensics.

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