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[
Curr Biol,
2002]
Transcriptional/translational feedback loops between clock genes such as per and tim - first cloned in Drosophila - and their protein products are thought to constitute the core of the circadian clock. A representative of the early metazoan body plan, the nematode (roundworm) Caenorhabditis elegans has had its complete cell lineage traced and it is known that it has many molecular components in common with those of the vertebrates. Recent studies have shown that C. elegans carries a per hmologue,
lin-42, and that its mRNA levels oscillate synchronously with approximately 6 hr molting cycles at the postembyronic developmental stage.
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[
Chronobiol Int,
2005]
The roundworm, Caenorhabditis elegans, is known to carry homologues of clock genes such as per (=period) and tim (=timeless), which constitute the core of the circadian clock in Drosophila and mammals:
lin-42 and
tim-1. Analyses using WormBase (C. elegans gene database) have identified with relatively high identity analogous of the clock genes recognized in Drosophila and mammals, with the notable exception of cry (=cryptochrome), which is lacking in C. elegans. All of these C. elegans cognates of the clock genes appear to belong to members of the PAS-superfamily and to participate in development or responsiveness to the environment but apparently are not involved in the C. elegans circadian clock. Nevertheless, C. elegans exhibits convincing circadian rhythms in locomotor behavior in the adult stage and in resistance to hyperosmotic stress in starved larvae (L1) after hatching, indicating that it has a circadian clock with a core design entirely different from that of Drosophila and mammals. Here two possibilities are considered. First, the core of the C. elegans circadian clock includes transcriptional/translational feedback loops between genes and their protein products that are entirely different from those of Drosophila and mammals. Second, a more basic principle such as homeostasis governs the circadian cellular physiology, and was established primarily to minimize the accumulation of DNA damage in response to an environment cycling at 24 h intervals.
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[
International Worm Meeting,
2007]
The automated tracking of locomotor behaviors is a fundamental tool for genetics, pharmacological and physiological studies. In this work we show the development and implementation of a new tracking system based on infrared microbeam scattering for the study of locomotor behavior in C. elegans. Adult worms were cultured individually in 96-plate wells (U-shape) with liquid medium, and their locomotor activity was tracked for more than 15 days. We tested E. coli OP50 solution, Leibovitzs L15 and CeMM culture medium, being CeMM the optimal for long-term experiments. To prevent self-reproduction, 40uM of Fluorodeoxyuridine (FuDR) was added at L4 stage. We used 1.5x Antibiotic-Antimycotic, silicone oil, and scotch tape to avoid contamination and desiccation. Since circadian rhythmicity was recently reported in C. elegans (1,2), we employed this method to characterize locomotor activity rhythms. Circadian rhythms were found to be entrained by diurnal light cycles (light:Dark 12:12 400:0 lux) peaking at the end of the night, analyzed by phase histograms. When entrained by temperature cycles they show maximum activity at the middle of the day . Indeed, when worms are entrained to high amplitude cycles of temperature (delta T=4 C) locomotor activity appears to be masked, observed as a significative decrease in locomotion for 1 hour when the temperature decreases. These rhythms still persist in constant conditions (continuous darkness, temperature set at 16; 18 or 20 C), with an average period of 23 h (37.5% of the worms exhibited significant circadian rhythms as analyzed by Lomb-Scargle periodogram), but with a high variation in their inter-individual period. Our system is therefore capable of determining circadian behaviors in this model and might be useful for its genetic and neural characterization. 1. Kippert F et al . 2002. Current biology 2. Saigusa T et al . 2002. Current biology.
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[
J Neurosci,
2003]
Thermotactic behavior in Caenorhabditis elegans is sensitive to both a worm's ambient temperature (T-amb) and its memory of the temperature of its cultivation (T-cult). The AFD neuron is part of a neural circuit that underlies thermotactic behavior. By monitoring the fluorescence of pH-sensitive green fluorescent protein localized to synaptic vesicles, we measured the rate of the synaptic release of AFD in worms cultivated at temperatures between 15 and 25degreesC, and subjected to fixed, ambient temperatures in the same range. We found that the rate of AFD synaptic release is high if either T-amb > T-cult or T-amb > T-cult, but AFD synaptic release is low if T-amb congruent to T-cult. This suggests that AFD encodes a direct comparison between T-amb and T-cult.
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[
Trends Mol Med,
2007]
Transforming growth factor beta1 (TGFbeta1), an important pleiotropic, immunoregulatory cytokine, uses distinct signaling mechanisms in lymphocytes to affect T-cell homeostasis, regulatory T (T(reg))-cell and effector-cell function and tumorigenesis. Defects in TGFbeta1 expression or its signaling in T cells correlate with the onset of several autoimmune diseases. TGFbeta1 prevents abnormal T-cell activation through the modulation of Ca(2+)-calcineurin signaling in a Caenorhabditis elegans Sma and Drosophila Mad proteins (SMAD)3 and SMAD4-independent manner; however, in T(reg) cells, its effects are mediated, at least in part, through SMAD signaling. TGFbeta1 also acts as a pro-inflammatory cytokine and induces interleukin (IL)-17-producing pathogenic T-helper cells (T(h) IL-17 cells) synergistically during an inflammatory response in which IL-6 is produced. Here, we will review TGFbeta1 and its signaling in T cells with an emphasis on the regulatory arm of immune tolerance.
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[
Genomics,
1995]
Recently, a novel family of genes with a region of homology to the mouse T locus, which is known to play a crucial, and conserved, role in vertebrate development, has been discovered. The region of homology has been named the T-box. The T-box domain of the prototypical T locus product is associated with sequence-specific DNA binding activity. In this report, we have characterized four members of the T-box gene family from the nematode Caenorhabditis elegans. All lie in close proximity to each other in the middle of chromosome III. Homology analysis among all completely sequenced T-box products indicates a larger size for the conserved T-box domain (166 to 203 residues) than previously reported. Phylogenetic analysis suggests that one C. elegans T-box gene may be a direct ortholog of the mouse Tbx2 and Drosophila omb genes. The accumulated data demonstrate the ancient nature of the T-box gene family and suggest the existence of at least three separate T-box-containing genes in a common early metazoan ancestor to nematodes and vertebrates.
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[
Glycobiology,
2006]
The common O-glycan core structure in animal glycoproteins is the core 1 disaccharide Galbeta1-3GalNAcalpha1-Ser/Thr, which is generated by addition of Gal to GalNAcalpha1-Ser/Thr by core 1 UDP-Gal:GalNAcalpha1-Ser/Thr beta1,3-galactosyltransferase (core 1 beta3-Gal-T or T-synthase, EC2.4.1.122)(2). Although O-glycans play important roles in vertebrates, much remains to be learned from model organisms such as the free-living nematode Caenorhabditis elegans, which offer many advantages in exploring O-glycan structure/function. Here we report the cloning and enzymatic characterization of T-synthase from C. elegans (Ce-T-synthase). A putative C. elegans gene for T-synthase, C38H2.2, was identified in GenBank by a BlastP search using the human T-synthase protein sequence. The full-length cDNA for Ce-T-synthase, which was generated by PCR using a C. elegans cDNA library as the template, contains 1,170 bp including the stop TAA. The cDNA encodes a protein of 389 amino acids with typical type-II membrane topology and a remarkable 42.7% identity to the human T-synthase. Ce-T-synthase has 7 Cys residues in the lumenal domain including 6 conserved Cys residues in all of the orthologs. The Ce-T-synthase has 4 potential N-glycosylation sequons, whereas the mammalian orthologs lack N-glycosylation sequons. Only one gene for Ce-T-synthase was identified in the genome-wide search and it contains 8 exons. Promoter analysis of the Ce-T-synthase using green fluorescent protein constructs show that the gene is expressed at all developmental stages and appears to be in all cells. Unexpectedly, only minimal activity was recovered in the recombinant, soluble Ce-T-synthase secreted from a wide variety of mammalian cell lines, whereas robust enzyme activity was recovered in the soluble Ce-T-synthase expressed in Hi-5 insect cells. Vertebrate T-synthase requires the molecular chaperone Cosmc, but our results show that Ce-T-synthase does not require Cosmc, and might require invertebrate-specific factors for formation of the optimally active enzyme. These results show that the Ce-T-synthase is a functional ortholog to the human T-synthase in generating core 1 O-glycans and opens new avenues to explore O-glycan function in this model organism.
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[
Int J Syst Evol Microbiol,
2007]
A yellow-pigmented, Gram-positive, aerobic, non-motile, non-spore-forming, irregular rod-shaped bacterium (strain TAN 31504(T)) was isolated from the bacteriophagous nematode Caenorhabditis elegans. Based on 16S rRNA gene sequence similarity, DNA G+C content of 69.5 mol%, 2,4-diaminobutyric acid in the cell-wall peptidoglycan, major menaquinone MK-11, abundance of anteiso- and iso-fatty acids, polar lipids diphosphatidylglycerol and phosphatidylglycerol and a number of shared biochemical characteristics, strain TAN 31504(T) was placed in the genus Leucobacter. DNA-DNA hybridization comparisons demonstrated a 91 % DNA-DNA relatedness between strain TAN 31504(T) and Leucobacter chromiireducens LMG 22506(T) indicating that these two strains belong to the same species, when the recommended threshold value of 70 % DNA-DNA relatedness for the definition of a bacterial species by the ad hoc committee on reconciliation of approaches to bacterial systematics is considered. Based on distinct differences in morphology, physiology, chemotaxonomic markers and various biochemical characteristics, it is proposed to split the species L. chromiireducens into two novel subspecies, Leucobacter chromiireducens subsp. chromiireducens subsp. nov. (type strain L-1(T)=CIP 108389(T)=LMG 22506(T)) and Leucobacter chromiireducens subsp. solipictus subsp. nov. (type strain TAN 31504(T)=DSM 18340(T)=ATCC BAA-1336(T)).
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[
International Worm Meeting,
2007]
Circadian clocks control the daily rhythms in physiology and behavior of organisms ranging from bacteria to mammals, as an adaptation to the earths 24-hour rotation. The basic mechanism underlying these circadian rhythms follows a similar general plan across the phylogenetic spectrum. In the fruit fly Drosophila melanogaster, a neuropeptide called pigment dispersing factor (PDF) is the key outgoing signal of the circadian system. Caenorhabditis elegans also exhibits a convincing circadian rhythm in locomotor behavior and in resistance to hyperosmotic stress (1-2), but the underlying mechanism still remains elusive. Here, we report the identification and characterization of a neuropeptide signaling system, similar to the key output signals of the circadian clock in Drosophila melanogaster. We identified three pigment dispersing factors (Ce-PDF-1a, b and Ce-PDF-2) and their G protein-coupled receptors in C. elegans, and demonstrate their involvement in the regulation of locomotor behavior (3). The three C. elegans PDFs were isolated from a peptide-enriched extract and identified by LC-MS. GFP fusions show that they are primarily expressed in specific head and tail neurons. The three identified GPCRs all display a specific affinity for each of the 3 Ce-PDFs. Receptor expression was observed in particular neurons and all somatic muscle cells. Many of the PDF and/or PDF-receptor expressing cells play a role in the integration of environmental stimuli and the control of locomotion. Overexpression of PDF-2 phenocopies the locomotor defects of a PDF-1 null mutant, suggesting that they elicit antagonistic effects on locomotion. These findings indicate that the Ce-PDFs may be a key outgoing signal in the C. elegans circadian clock, changing the locomotor behavior by acting through these (muscle) receptors. Our findings suggest that PDF signaling might be well conserved during evolution, at least in invertebrates (3). 1. Kippert,F. et al. Caenorhabditis elegans has a circadian clock. Curr. Biol. 12, R47-R49 (2002). 2. Saigusa,T. et al. Circadian behavioural rhythm in Caenorhabditis elegans. Curr. Biol. 12, R46-R47 (2002). 3. Janssen et al. The clock ticks on with the discovery of PDF and its receptors in the nematode Caenorhabditis elegans. Neuron submitted.
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[
Genome,
1997]
The T-box gene family consists of members that share a unique DNA binding domain. The best characterized T-box gene, Brachyury or T, encodes a transcription factor that plays an important role in early vertebrate development. Seven other recently described mouse T-box genes are also expressed during development. In the nematode Caenorhabditis elegans, four T-box genes have been characterized to date. In this study, we describe three new C. elegans T-box genes, named
Ce-tbx-11,
Ce-tbx-12, and
Ce-tbx-17.
Ce-tbx-11 and
Ce-tbx-17 were uncovered through the sequencing efforts of the C. elegans Genome Project.
Ce-tbx-12 was uncovered through degenerate PCR analysis of C. elegans genomic DNA.
Ce-tbx-11 and
Ce-tbx-17 are located in close proximity to the four other previously described T-box genes in the central region of chromosome III. In contrast,
Ce-tbx-12 maps alone to chromosome II. Phylogenetic analysis of all known T-box domain sequences provides evidence of an ancient origin for this gene family.