scholarly journals Calcineurin homologous proteins regulate the membrane localization and activity of sodium/proton exchangers in C. elegans

2016 ◽  
Vol 310 (3) ◽  
pp. C233-C242 ◽  
Author(s):  
Erik Allman ◽  
Qian Wang ◽  
Rachel L. Walker ◽  
Molly Austen ◽  
Maureen A. Peters ◽  
...  
Keyword(s):  
Genetic Model ◽  
Expression Patterns ◽  
Critical Role ◽  
Model Organism ◽  
Loss Of Function ◽  
Homologous Proteins ◽  
Relative Significance ◽  
C Elegans ◽  
Fluorescent Tags

Calcineurin B homologous proteins (CHP) are N-myristoylated, EF-hand Ca2+-binding proteins that bind to and regulate Na+/H+ exchangers, which occurs through a variety of mechanisms whose relative significance is incompletely understood. Like mammals, Caenorhabditis elegans has three CHP paralogs, but unlike mammals, worms can survive CHP loss-of-function. However, mutants for the CHP ortholog PBO-1 are unfit, and PBO-1 has been shown to be required for proton signaling by the basolateral Na+/H+ exchanger NHX-7 and for proton-coupled intestinal nutrient uptake by the apical Na+/H+ exchanger NHX-2. Here, we have used this genetic model organism to interrogate PBO-1's mechanism of action. Using fluorescent tags to monitor Na+/H+ exchanger trafficking and localization, we found that loss of either PBO-1 binding or activity caused NHX-7 to accumulate in late endosomes/lysosomes. In contrast, NHX-2 was stabilized at the apical membrane by a nonfunctional PBO-1 protein and was only internalized following its complete loss. Additionally, two pbo-1 paralogs were identified, and their expression patterns were analyzed. One of these contributed to the function of the excretory cell, which acts like a kidney in worms, establishing an alternative model for testing the role of this protein in membrane transporter trafficking and regulation. These results lead us to conclude that the role of CHP in Na+/H+ exchanger regulation differs between apical and basolateral transporters. This further emphasizes the importance of proper targeting of Na+/H+ exchangers and the critical role of CHP family proteins in this process.

scholarly journals SOS2 Comes to the Fore: Differential Functionalities in Physiology and Pathology

2021 ◽  
Vol 22 (12) ◽  
pp. 6613
Author(s):  
Fernando C. Baltanás ◽  
Rósula García-Navas ◽  
Eugenio Santos
Keyword(s):  
Expression Patterns ◽  
Critical Role ◽  
Ras Signaling ◽  
Epidermal Stem Cell ◽  
Functional Specificity ◽  
Functional Roles ◽  
Signaling Axis ◽  
Therapy Target ◽  
External Stimuli

The SOS family of Ras-GEFs encompasses two highly homologous and widely expressed members, SOS1 and SOS2. Despite their similar structures and expression patterns, early studies of constitutive KO mice showing that SOS1-KO mutants were embryonic lethal while SOS2-KO mice were viable led to initially viewing SOS1 as the main Ras-GEF linking external stimuli to downstream RAS signaling, while obviating the functional significance of SOS2. Subsequently, different genetic and/or pharmacological ablation tools defined more precisely the functional specificity/redundancy of the SOS1/2 GEFs. Interestingly, the defective phenotypes observed in concomitantly ablated SOS1/2-DKO contexts are frequently much stronger than in single SOS1-KO scenarios and undetectable in single SOS2-KO cells, demonstrating functional redundancy between them and suggesting an ancillary role of SOS2 in the absence of SOS1. Preferential SOS1 role was also demonstrated in different RASopathies and tumors. Conversely, specific SOS2 functions, including a critical role in regulation of the RAS–PI3K/AKT signaling axis in keratinocytes and KRAS-driven tumor lines or in control of epidermal stem cell homeostasis, were also reported. Specific SOS2 mutations were also identified in some RASopathies and cancer forms. The relevance/specificity of the newly uncovered functional roles suggests that SOS2 should join SOS1 for consideration as a relevant biomarker/therapy target.

AMPK blocks chromatin activation and consequent R-loop formation to protect genome stability following acute starvation

2021 ◽  
Author(s):  
Bing Sun ◽  
McLean Sherrin ◽  
Richard Roy
Keyword(s):  
Dna Damage ◽  
Genome Stability ◽  
Germ Line ◽  
Critical Role ◽  
Significant Proportion ◽  
Loop Formation ◽  
C Elegans ◽  
Chromatin Activation ◽  
Acute Starvation

Abstract During periods of starvation organisms must modify both gene expression and metabolic pathways to adjust to the energy stress. We previously reported that C. elegans that lack AMPK have transgenerational reproductive defects that result from abnormally elevated H3K4me3 levels in the germ line following recovery from acute starvation1. Here we show that H3K4me3 is dramatically increased at promoters, driving aberrant transcription elongation that results in the accumulation of R-loops in the starved AMPK mutants. DRIP-seq analysis demonstrated that a significant proportion of the genome was affected by R-loop formation with a dramatic expansion in the number of R-loops at numerous loci, most pronounced at the promoter-TSS regions of genes in the starved AMPK mutants. The R-loops are transmissible into subsequent generations, likely contributing to the transgenerational reproductive defects typical of these mutants following starvation. Strikingly, AMPK null germ lines show considerably more RAD-51 foci at sites of R-loop formation, potentially sequestering it from its critical role at meiotic breaks and/or at sites of induced DNA damage. Our study reveals a previously unforeseen role of AMPK in maintaining genome stability following starvation, where in its absence R-loops accumulate, resulting in reproductive compromise and DNA damage hypersensitivity.

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 The Critical Role of Institutional Services in Open Access Advocacy

2013 ◽  
Vol 8 (1) ◽  
pp. 84-106 ◽  
Author(s):  
Tomasz Neugebauer ◽  
Annie Murray
Keyword(s):  
Open Access ◽  
Critical Role ◽  
Text Data ◽  
Relative Significance ◽  
Institutional Repositories ◽  
Time Commitment ◽  
Institutional Services ◽  
Service Oriented ◽  
User Friendly

This paper examines the development of the Open Access movement in scholarly communication, with particular attention to some of the rhetorical strategies and policy mechanisms used to promote it to scholars and scientists. Despite the majority of journal publishers’ acceptance of author self-archiving practices, and the minimal time commitment required by authors to successfully self-archive their work in disciplinary or institutional repositories, the majority of authors still by and large avoid participation. The paper reviews the strategies and arguments used for increasing author participation in open access, including the role of open access mandates. We recommend a service-oriented approach towards increasing participation in open access, rather than rhetoric that speculates on the benefits that open access will have on text/data mining innovation. In advocating for open access participation, we recommend focusing on its most universal and tangible purpose: increasing public open (gratis) access to the published results of publicly funded research. Researchers require strong institutional support to understand the copyright climate of open access self-archiving, user-friendly interfaces and useful metrics, such as repository usage statistics. We recommend that mandates and well-crafted and responsive author support services at universities will ultimately be required to ensure the growth of open access. We describe the mediated deposit service that was developed to support author self-archiving in Spectrum: Concordia University Research Repository. By comparing the number of deposits of non-thesis materials (e.g. articles and conference presentations) that were accomplished through the staff-mediated deposit service to the number of deposits that were author-initiated, we demonstrate the relative significance of this service to the growth of the repository.

scholarly journals Multicellular rosettes organize neuropil formation

2020 ◽  
Author(s):  
Christopher A. Brittin ◽  
Anthony Santella ◽  
Kristopher Barnes ◽  
Mark W. Moyle ◽  
Li Fan ◽  
...  
Keyword(s):  
Functional Organization ◽  
Critical Role ◽  
Ring Structure ◽  
Nerve Ring ◽  
Cell Behaviors ◽  
Dense Networks ◽  
C Elegans ◽  
Single Axon ◽  
Organizational Features

SummaryNeuropils are compartments in the nervous system containing dense networks of neurites and synapses which function as information processing centers. Neuropil formation requires structural and functional organization at and across different scales, achieving single-axon precision for circuits that carry out the core functions while simultaneously accommodating variability among individuals [1; 2; 3; 4]. How these organizational features emerge over development is poorly understood. The nerve ring is the primary neuropil in C. elegans, and its structure is thoroughly mapped [5; 6]. We show that prior to axon outgrowth, nerve ring neurons form a ring of multicellular rosettes with surrounding cells to organize the stratified nerve ring structure [7; 8]. Axon bundles which correspond to future nerve ring strata grow from rosette centers, travel along the ring on “bridge” cells that are simultaneously engaged in adjacent rosettes, and assemble into a topographic scaffold of the nerve ring. SAX-3/Robo is required for proper rosette formation and outgrowth from the center. Furthermore, axon contact sites that form early in development are more conserved than the later ones, indicating a temporal component in neuropil structural variability. Our results reveal an unexpected and critical role of collective cell behaviors prior to innervation to pattern a complex neuropil and orchestrate its formation across scales.

scholarly journals Thymus leukemia antigen controls intraepithelial lymphocyte function and inflammatory bowel disease

2008 ◽  
Vol 105 (46) ◽  
pp. 17931-17936 ◽  
Author(s):  
Danyvid Olivares-Villagómez ◽  
Yanice V. Mendez-Fernandez ◽  
Vrajesh V. Parekh ◽  
Saif Lalani ◽  
Tiffaney L. Vincent ◽  
...  
Keyword(s):  
Inflammatory Bowel Disease ◽  
Bowel Disease ◽  
Intestinal Inflammation ◽  
Genetic Model ◽  
Critical Role ◽  
Intraepithelial Lymphocytes ◽  
Lymphocyte Function ◽  
Intestinal Epithelial ◽  
Inflammatory Bowel

Intestinal intraepithelial lymphocytes (IEL) bear a partially activated phenotype that permits them to rapidly respond to antigenic insults. However, this phenotype also implies that IEL must be highly controlled to prevent misdirected immune reactions. It has been suggested that IEL are regulated through the interaction of the CD8αα homodimer with the thymus leukemia (TL) antigen expressed by intestinal epithelial cells. We have generated and characterized mice genetically-deficient in TL expression. Our findings show that TL expression has a critical role in maintaining IEL effector functions. Also, TL deficiency accelerated colitis in a genetic model of inflammatory bowel disease. These findings reveal an important regulatory role of TL in controlling IEL function and intestinal inflammation.

The C. elegans NeuroD homolog cnd-1 functions in multiple aspects of motor neuron fate specification

Development ◽  
2000 ◽  
Vol 127 (19) ◽  
pp. 4239-4252 ◽  
Author(s):  
S. Hallam ◽  
E. Singer ◽  
D. Waring ◽  
Y. Jin
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Expression Patterns ◽  
Loss Of Function ◽  
Variable Expression ◽  
C Elegans ◽  
Helix Loop Helix ◽  
Ventral Cord ◽  
Bhlh Proteins ◽  
Neuronal Type

The basic helix-loop-helix transcription factor NeuroD (Neurod1) has been implicated in neuronal fate determination, differentiation and survival. Here we report the expression and functional analysis of cnd-1, a C. elegans NeuroD homolog. cnd-1 expression was first detected in neuroblasts of the AB lineage in 14 cell embryos and maintained in many neuronal descendants of the AB lineage during embryogenesis, diminishing in most terminally differentiated neurons prior to hatching. Specifically, cnd-1 reporter genes were expressed in the precursors of the embryonic ventral cord motor neurons and their progeny. A loss-of-function mutant, cnd-1(ju29), exhibited multiple defects in the ventral cord motor neurons. First, the number of motor neurons was reduced, possibly caused by the premature withdrawal of the precursors from mitotic cycles. Second, the strict correlation between the fate of a motor neuron with respect to its lineage and position in the ventral cord was disrupted, as manifested by the variable expression pattern of motor neuron fate specific markers. Third, motor neurons also exhibited defects in terminal differentiation characteristics including axonal morphology and synaptic connectivity. Finally, the expression patterns of three neuronal type-specific transcription factors, unc-3, unc-4 and unc-30, were altered. Our data suggest that cnd-1 may specify the identity of ventral cord motor neurons both by maintaining the mitotic competence of their precursors and by modulating the expression of neuronal type-specific determination factors. cnd-1 appears to have combined the functions of several vertebrate neurogenic bHLH proteins and may represent an ancestral form of this protein family.

scholarly journals Caenorhabditis elegans as a Model Organism to Evaluate the Antioxidant Effects of Phytochemicals

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3194
Author(s):  
Begoña Ayuda-Durán ◽  
Susana González-Manzano ◽  
Ana M. González-Paramás ◽  
Celestino Santos-Buelga
Keyword(s):  
Oxidative Stress ◽  
Caenorhabditis Elegans ◽  
Model Organism ◽  
Lipid Peroxides ◽  
Biological Research ◽  
Loss Of Function ◽  
Fluorescent Reporters ◽  
C Elegans ◽  
High Degree

The nematode Caenorhabditis elegans was introduced as a model organism in biological research by Sydney Brenner in the 1970s. Since then, it has been increasingly used for investigating processes such as ageing, oxidative stress, neurodegeneration, or inflammation, for which there is a high degree of homology between C. elegans and human pathways, so that the worm offers promising possibilities to study mechanisms of action and effects of phytochemicals of foods and plants. In this paper, the genes and pathways regulating oxidative stress in C. elegans are discussed, as well as the methodological approaches used for their evaluation in the worm. In particular, the following aspects are reviewed: the use of stress assays, determination of chemical and biochemical markers (e.g., ROS, carbonylated proteins, lipid peroxides or altered DNA), influence on gene expression and the employment of mutant worm strains, either carrying loss-of-function mutations or fluorescent reporters, such as the GFP.

scholarly journals Caenorhabditits elegans LRK-1 and PINK-1 Act Antagonistically in Stress Response and Neurite Outgrowth

2009 ◽  
Vol 284 (24) ◽  
pp. 16482-16491 ◽  
Author(s):  
Julia Sämann ◽  
Jan Hegermann ◽  
Erika von Gromoff ◽  
Stefan Eimer ◽  
Ralf Baumeister ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Stress Response ◽  
Parkinson Disease ◽  
Neurite Outgrowth ◽  
Physiological Role ◽  
Model Organisms ◽  
Loss Of Function ◽  
C Elegans ◽  
Genes Encoding

Mutations in two genes encoding the putative kinases LRRK2 and PINK1 have been associated with inherited variants of Parkinson disease. The physiological role of both proteins is not known at present, but studies in model organisms have linked their mutants to distinct aspects of mitochondrial dysfunction, increased vulnerability to oxidative and endoplasmic reticulum stress, and intracellular protein sorting. Here, we show that a mutation in the Caenorhabditits elegans homologue of the PTEN-induced kinase pink-1 gene resulted in reduced mitochondrial cristae length and increased paraquat sensitivity of the nematode. Moreover, the mutants also displayed defects in axonal outgrowth of a pair of canal-associated neurons. We demonstrate that in the absence of lrk-1, the C. elegans homologue of human LRRK2, all phenotypic aspects of pink-1 loss-of-function mutants were suppressed. Conversely, the hypersensitivity of lrk-1 mutant animals to the endoplasmic reticulum stressor tunicamycin was reduced in a pink-1 mutant background. These results provide the first evidence of an antagonistic role of PINK-1 and LRK-1. Due to the similarity of the C. elegans proteins to human LRRK2 and PINK1, we suggest a common role of both factors in cellular functions including stress response and regulation of neurite outgrowth. This study might help to link pink-1/PINK1 and lrk-1/LRRK2 function to the pathological processes resulting from Parkinson disease-related mutants in both genes, the first manifestations of which are cytoskeletal defects in affected neurons.

scholarly journals Tissue- and paralogue-specific functions of acyl-CoA-binding proteins in lipid metabolism in Caenorhabditis elegans

2011 ◽  
Vol 437 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Ida C. Elle ◽  
Karina T. Simonsen ◽  
Louise C. B. Olsen ◽  
Pernille K. Birck ◽  
Sidse Ehmsen ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Unsaturated Fatty Acids ◽  
Expression Patterns ◽  
High Specificity ◽  
Tissue Expression ◽  
Yeast Cells ◽  
Loss Of Function ◽  
C Elegans ◽  
Eukaryotic Species ◽  
Quadruple Mutant

ACBP (acyl-CoA-binding protein) is a small primarily cytosolic protein that binds acyl-CoA esters with high specificity and affinity. ACBP has been identified in all eukaryotic species, indicating that it performs a basal cellular function. However, differential tissue expression and the existence of several ACBP paralogues in many eukaryotic species indicate that these proteins serve distinct functions. The nematode Caenorhabditis elegans expresses seven ACBPs: four basal forms and three ACBP domain proteins. We find that each of these paralogues is capable of complementing the growth of ACBP-deficient yeast cells, and that they exhibit distinct temporal and tissue expression patterns in C. elegans. We have obtained loss-of-function mutants for six of these forms. All single mutants display relatively subtle phenotypes; however, we find that functional loss of ACBP-1 leads to reduced triacylglycerol (triglyceride) levels and aberrant lipid droplet morphology and number in the intestine. We also show that worms lacking ACBP-2 show a severe decrease in the β-oxidation of unsaturated fatty acids. A quadruple mutant, lacking all basal ACBPs, is slightly developmentally delayed, displays abnormal intestinal lipid storage, and increased β-oxidation. Collectively, the present results suggest that each of the ACBP paralogues serves a distinct function in C. elegans.

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