MEC-12, an alpha-tubulin required for touch sensitivity in C. elegans

1999 ◽  
Vol 112 (3) ◽  
pp. 395-403 ◽  
Author(s):  
T. Fukushige ◽  
Z.K. Siddiqui ◽  
M. Chou ◽  
J.G. Culotti ◽  
C.B. Gogonea ◽  
...  
Keyword(s):  
Large Diameter ◽  
Microtubule Assembly ◽  
Single Class ◽  
Alpha Tubulin ◽  
C Elegans ◽  
Tubulin Isotype ◽  
Touch Receptor Neurons ◽  
Touch Sensitivity ◽  
Similar Phenotype ◽  
Touch Receptor Neuron

mec-12 is one of a dozen genes required for touch receptor neuron function in Caenorhabditis elegans. Some mec-12 mutants (mechanosensory-defective) lack the large-diameter microtubules that are characteristic of these neurons (15 protofilaments, as opposed to 11). Mutants of mec-7, a alpha-tubulin encoding gene, have a similar phenotype. We have identified the nature of mec-12 by germline transformation rescue and characterization of a point mutation. Sequence analysis of the mec-12 encoded product (MEC-12) indicates that it corresponds to a novel C. elegans alpha-tubulin. MEC-12 is the only identified C. elegans alpha-tubulin that contains a lysine at position 40, a known site of post-translational acetylation. Some mec-12 mutations eliminate microtubule acetylation as assayed immunocyto-chemically; phenotypic rescue using a MEC-12 variant lacking the lysine-40 showed that acetylation is not required for MEC-12 activity. Although functionally needed only in the touch neurons, mec-12 is expressed in several other neuron types. These results support the notion that tubulin isotype diversity contributes to the formation of distinct classes of microtubules; 15-protofilament microtubule assembly requires MEC-12 alpha-tubulin and MEC-7 beta-tubulin, which are both highly expressed in the touch receptor neurons. MEC-12 is the first reported alpha-tubulin isotype that appears to be required in a single class of neuronal microtubules.

scholarly journals Structural and functional diversity in the neuronal microtubules of Caenorhabditis elegans.

1982 ◽  
Vol 93 (1) ◽  
pp. 15-23 ◽  
Author(s):  
M Chalfie ◽  
J N Thomson
Keyword(s):  
Caenorhabditis Elegans ◽  
Colchicine Treatment ◽  
Variable Number ◽  
Sensory Transduction ◽  
Partial Replacement ◽  
C Elegans ◽  
Touch Receptor Neurons ◽  
Touch Sensitivity ◽  
Receptor Neurons

Tannic acid fixation reveals differences in the number of protofilaments between microtubules (MTs) in the nematode Caenorhabditis elegans. Most cells have MTs with 11 protofilaments but the six touch receptor neurons (the microtubule cells) have MTs with 15 protofilaments. No 13-protofilament (13-p) MT has been seen. The modified cilia of sensory neurons also possess unusual structures. The cilia contain nine outer doublets with A subfibers of 13 protofilaments and B subfibers of 11 protofilaments and a variable number of inner singlet MTs containing 11 protofilaments. The 15-p MTs but not the 11-p MTs are eliminated by colchicine-treatment or by mutation of the gene mec-7. Concomitantly, touch sensitivity is also lost. However, whereas colchicine treatment leads to the loss of all MTs from the microtubule cells, mutations in mec-7 result in the partial replacement of the 15-p MTs with 11-p MTs. Benzimidazoles (benomyl and nocodazole) have more general effects on C. elegans (slow growth, severe uncoordination, and loss of processes from the ventral cord) but do not affect the 15-p MTs. Benomyl will, however, disrupt the replacement 11-p MTs found in the microtubule cells of mec-7 mutants. The 11-p and 15-p MTs also respond differently to temperature and fixation conditions. It is likely that either type of MT will suffice for the proper outgrowth of the microtubule cell process, but only the 15-p MT can function in the specialized role of sensory transduction of the microtubule cells.

Combinatorial control of touch receptor neuron expression in Caenorhabditis elegans

Development ◽  
1993 ◽  
Vol 119 (3) ◽  
pp. 773-783 ◽  
Author(s):  
S. Mitani ◽  
H. Du ◽  
D.H. Hall ◽  
M. Driscoll ◽  
M. Chalfie
Keyword(s):  
Caenorhabditis Elegans ◽  
Cell Types ◽  
Wild Type ◽  
Negative Regulators ◽  
C Elegans ◽  
Combinatorial Control ◽  
Touch Receptor Neurons ◽  
In The Wild ◽  
Receptor Neurons ◽  
Touch Receptor Neuron

Six touch receptor neurons with distinctive morphological features sense gentle touch in Caenorhabditis elegans. Previous studies have identified three genes (lin-32, unc-86 and mec-3) that regulate touch cell development. However, since other cell types also require these genes, we suspected that other genes help restrict the expression of touch cell characteristics to the six neurons seen in the wild type. To identify such genes, we have examined mutants defective in genes required for the development of other C. elegans cells for changes in the pattern of touch cell-specific features. Mutations in seven genes either reduce (lin-14) or increase (lin-4, egl-44, egl-46, sem-4, ced-3 and ced-4) the number of touch receptor-like cells. The combinatorial action of these genes, all of which are required for the production of many cell types, restrict the number of cells expressing touch receptor characteristics in wild-type animals by acting as positive and negative regulators and by removing cells by programmed cell death.

scholarly journals Regulated distribution of mitochondria in touch receptor neurons of C. elegans influences touch response

2020 ◽  
Author(s):  
Anjali Awasthi ◽  
Souvik Modi ◽  
Sneha Hegde ◽  
Anusheela Chatterjee ◽  
Sudip Mondal ◽  
...  
Keyword(s):  
Molecular Motors ◽  
Neuronal Function ◽  
Mitochondrial Density ◽  
Neuronal Process ◽  
C Elegans ◽  
Touch Receptor Neurons ◽  
Touch Response ◽  
Receptor Neurons ◽  
Touch Receptor Neuron

AbstractDensity of mitochondria and their localization at specific sub-cellular regions of the neurons is regulated by molecular motors, their adaptors and the cytoskeleton. However, the regulation of the mitochondrial density, the positioning of mitochondria along the neuronal process and the role of axonal mitochondria in neuronal function remain poorly understood. This study shows that the density of mitochondria in C. elegans touch receptor neuron processes remains constant through development. Simulations show that mitochondrial positioning along parts of the neuronal process that are devoid of synapses is regulated. Additionally, we also demonstrate that axonal mitochondria are necessary for maintaining touch responsiveness.

scholarly journals Six mouse alpha-tubulin mRNAs encode five distinct isotypes: testis-specific expression of two sister genes.

1986 ◽  
Vol 6 (7) ◽  
pp. 2409-2419 ◽  
Author(s):  
A Villasante ◽  
D Wang ◽  
P Dobner ◽  
P Dolph ◽  
S A Lewis ◽  
...  
Keyword(s):  
Duplication Event ◽  
Developmental Expression ◽  
Untranslated Regions ◽  
Coding Region ◽  
Specific Expression ◽  
Translational Initiation ◽  
Alpha Tubulin ◽  
Tubulin Isotypes ◽  
Tubulin Isotype ◽  
Genes Encoding

Five mouse alpha-tubulin isotypes are described, each distinguished by the presence of unique amino acid substitutions within the coding region. Most, though not all of these isotype-specific amino acids, are clustered at the carboxy terminus. One of the alpha-tubulin isotypes described is expressed exclusively in testis and is encoded by two closely related genes (M alpha 3 and M alpha 7) which have homologous 3' untranslated regions but which differ at multiple third codon positions and in their 5' untranslated regions. We show that a subfamily of alpha-tubulin genes encoding the same testis-specific isotype also exists in humans. Thus, we conclude that the duplication event leading to a pair of genes encoding a testis-specific alpha-tubulin isotype predated the mammalian radiation, and both members of the duplicated sequence have been maintained since species divergence. A second alpha-tubulin gene, M alpha 6, is expressed ubiquitously at a low level, whereas a third gene, M alpha 4, is unique in that it does not encode a carboxy-terminal tyrosine residue. This gene yields two transcripts: a 1.8-kilobase (kb) mRNA that is abundant in muscle and a 2.4-kb mRNA that is abundant in testis. Whereas the 1.8-kb mRNA encodes a distinct alpha-tubulin isotype, the 2.4-kb mRNA is defective in that the methionine residue required for translational initiation is missing. Patterns of developmental expression of the various alpha-tubulin isotypes are presented. Our data support the view that individual tubulin isotypes are capable of conferring functional specificity on different kinds of microtubules.

20. Discovery of Novel Proteins Involved the Insulin/IGF-1 Signalling Pathway

2018 ◽  
Author(s):  
David (Wen Xiao) Wei
Keyword(s):  
Protein Interactions ◽  
Mutant Form ◽  
Yeast Two Hybrid ◽  
C Elegans ◽  
Insulin Growth Factor ◽  
Novel Proteins ◽  
Similar Phenotype ◽  
Two Hybrid ◽  
Hsp90 Protein ◽  
Novel Protein

The insulin/insulin growth factor-1 (IGF-1) signalling (IIS) pathway plays a key role in metabolism, growth and development. Though research has elucidated aspects of this pathway, it is not fully characterized or understood. A better understanding of the pathway will give insight into related diseases such as cancer. To discover novel proteins involved in the IIS pathway, the C. elegans worm was used due to the homology its insulin/IGF-1 receptor shares with that of humans.  To identify novel protein interactions with the insulin/IGF-1 receptor, we performed a yeast two-hybrid screen using a library of worm proteins. We found several separate interactions with the worm homolog of the HSP90 protein. To support the involvement of HSP90 in the IIS pathway, we studied the phenotypes of worm strains with a mutant form of HSP90. They showed a similar phenotype to those that have a mutant form of the insulin/IGF-1 receptor, inappropriately entering a developmental stage known as dauer. This strongly suggests the involvement of HSP90 in the IIS pathway. Based on previous research, we hypothesized the interaction between HSP90 and the insulin/IGF-1 receptor may allow it to bind other proteins. Thus, we performed a modified yeast two-hybrid screen to identify proteins which interact with the receptor in the presence of HSP90. The screen identified 15 interactions, many more than with the insulin/IGF-1 receptor alone, supporting this hypothesis. Overall, we provide evidence of a novel interaction with insulin/IGF-1 receptor, suggesting HSP90 may be a potential target for developing therapies for IIS pathway related diseases.

Overexpression of yeast homologs of the mammalian checkpoint gene RCC1 suppresses the class of alpha-tubulin mutations that arrest with excess microtubules.

Genetics ◽  
1994 ◽  
Vol 137 (2) ◽  
pp. 381-392 ◽  
Author(s):  
D Kirkpatrick ◽  
F Solomon
Keyword(s):  
Cell Cycle ◽  
Microtubule Assembly ◽  
Functional Requirements ◽  
Cellular Regulation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Alpha Tubulin ◽  
Class 1 ◽  
Cold Sensitive ◽  
Growth Phenotype ◽  
Cytoplasmic Structures

Abstract Microtubules in eukaryotic cells participate in a variety of nuclear and cytoplasmic structures, reflecting functional requirements and cell cycle position. We are studying the cellular regulation of microtubule assembly and organization in the yeast Saccharomyces cerevisiae. We screened for genes that when overexpressed suppress the growth phenotype of conditional mutants in alpha-tubulin that arrest with excess microtubules at the nonpermissive temperature (class 2 mutations). Here we describe one such suppressing element, called ATS1 (for Alpha Tubulin Suppressor). Overexpression of this gene rescues both the growth and microtubule phenotypes of all class 2 mutations, but not the cold-sensitive mutations that arrest with no microtubules (class 1 mutations). Deletion of ATS1 confers a modest slow growth phenotype which is slightly enhanced in strains containing both a deletion of ATS1 and a class 2 tub 1 mutation. The predicted ATS1 protein contains 333 amino acids and has considerable structural homology to the products of both the mammalian mitotic control gene RCC1 and the S. cerevisiae gene SRM1/PRP20. Overexpression of SRM1/PRP20 also suppresses class 2 mutants. The results suggest that this family of genes may participate in regulatory interactions between microtubules and the cell cycle.

scholarly journals Distinct roles for innexin gap junctions and hemichannels in mechanosensation

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Denise S Walker ◽  
William R Schafer
Keyword(s):  
Blood Pressure ◽  
Heterologous Expression ◽  
Pain Perception ◽  
Mechanosensory Transduction ◽  
Wide Range ◽  
Touch Receptor Neurons ◽  
Touch Sensitivity ◽  
Range Of Functions ◽  
Receptor Neurons ◽  
And Control

Mechanosensation is central to a wide range of functions, including tactile and pain perception, hearing, proprioception, and control of blood pressure, but identifying the molecules underlying mechanotransduction has proved challenging. In Caenorhabditis elegans, the avoidance response to gentle body touch is mediated by six touch receptor neurons (TRNs), and is dependent on MEC-4, a DEG/ENaC channel. We show that hemichannels containing the innexin protein UNC-7 are also essential for gentle touch in the TRNs, as well as harsh touch in both the TRNs and the PVD nociceptors. UNC-7 and MEC-4 do not colocalize, suggesting that their roles in mechanosensory transduction are independent. Heterologous expression of unc-7 in touch-insensitive chemosensory neurons confers ectopic touch sensitivity, indicating a specific role for UNC-7 hemichannels in mechanosensation. The unc-7 touch defect can be rescued by the homologous mouse gene Panx1 gene, thus, innexin/pannexin proteins may play broadly conserved roles in neuronal mechanotransduction.

scholarly journals Alzheimer’s disease-relevant tau modifications selectively impact neurodegeneration and mitophagy in a novel C. elegans single-copy transgenic model

2020 ◽  
Author(s):  
Sanjib Guha ◽  
Sarah Fischer ◽  
Gail VW Johnson ◽  
Keith Nehrke
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Genetic Model ◽  
Neurodegenerative Disorder ◽  
Model Organism ◽  
Single Copy ◽  
Mitochondrial Stress ◽  
C Elegans ◽  
Touch Receptor Neurons ◽  
New Perspective

ABSTRACTBackgroundA defining pathological hallmark of the progressive neurodegenerative disorder Alzheimer’s disease (AD) is the accumulation of misfolded tau with abnormal post-translational modifications (PTMs). These include phosphorylation at Threonine 231 (T231) and acetylation at Lysine 274 (K274) and at Lysine 281 (K281). Although tau is recognized to play a central role in pathogenesis of AD, the precise mechanisms by which these abnormal PTMs contribute to the neural toxicity of tau is unclear.MethodsHuman 0N4R tau (wild type) was expressed in touch receptor neurons of the genetic model organism C. elegans through single-copy gene insertion. Defined mutations were then introduced into the single-copy tau transgene through CRISPR-Cas9 genome editing. These mutations included T231E and T231A, to mimic phosphorylation and phospho-ablation of a commonly observed pathological epitope, respectively, and K274/281Q, to mimic disease-associated lysine acetylation. Stereotypical touch response assays were used to assess behavioral defects in the transgenic strains as a function of age, and genetically-encoded fluorescent biosensors were used to measure the morphological dynamics and turnover of touch neuron mitochondria.ResultsUnlike existing tau overexpression models, C. elegans single-copy expression of tau did not elicit overt pathological phenotypes at baseline. However, strains expressing disease associated PTM-mimetics (T231E and K274/281Q) exhibited reduced touch sensation and morphological abnormalities that increased with age. In addition, the PTM-mimetic mutants lacked the ability to engage mitophagy in response to mitochondrial stress.ConclusionsLimiting the expression of tau results in a genetic model where pathological modifications and age result in evolving phenotypes, which may more closely resemble the normal progression of AD. The finding that disease-associated PTMs suppress compensatory responses to mitochondrial stress provides a new perspective into the pathogenic mechanisms underlying AD.

scholarly journals Identification and characterization of microtubule proteins from myxamoebae of Physarum polycephalum

1980 ◽  
Vol 189 (2) ◽  
pp. 305-312 ◽  
Author(s):  
A Roobol ◽  
C I Pogson ◽  
K Gull
Keyword(s):  
Physarum Polycephalum ◽  
Microtubule Assembly ◽  
Alpha Tubulin ◽  
Microtubule Associated Proteins ◽  
Cell Extracts ◽  
Microtubule Protein ◽  
Associated Proteins ◽  
Microtubule Formation

Cell extracts of myxamoebae of Physarum polycephalum have been prepared in such a way that they do not inhibit assembly of brain microtubule protein in vitro even at high extract-protein concentration. Co-polymers of these extracts and brain tubulin have been purified to constant stoichiometry and amoebal components identified by radiolabelling. Amoebal tubulin has been identified as having an alpha-subunit, mol.wt. 54 000, which co-migrates with brain alpha-tubulin and a beta-subunit, mol.wt. 50 000, which co-migrates with Tetrahymena ciliary beta-tubulin. Non-tubulin amoebal proteins that co-purify with tubulin during co-polymer formation have been shown to be essential for microtubule formation in the absence of glycerol and appear to be rather more effective than brain microtubule-associated proteins in stimulating assembly. The mitotic inhibitor griseofulvin (7-chloro-2′,4,6-trimethoxy-6′-methylspiro[benzofuran-2(3H),1′-cyclohex-2′-ene] −3,4′-dione), which binds to brain microtubule-associated proteins and inhibits brain microtubule assembly in vitro, affected co-polymer microtubule protein in a similar way, but to a slightly greater extent.

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