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[
Dev Biol,
2006]
The development of multicellular organisms requires precise spatiotemporal gene expression and the expression of cell/tissue specific isoforms of some genes. This task may require more efficient genome organization in Caenorhabditis elegans and other organisms with relatively small genome size. The SL1 leader sequence is trans-spliced to many mRNAs in C. elegans. We hypothesize that introns coupled to internal SL1 acceptors contain independent promoters. We identify 238 genes that have introns coupled to internal SL1 acceptors. We find that the mean length of the internal SL1-coupled introns is significantly longer than the genome mean. For twelve of the genes, evidence exists that the intronic promoter provides tissue specificity different from that of the primary promoter. We estimate that 2.7% of the genome is regulated through this two-promoter system. We propose that internal SL1-coupled introns function as independent promoters and that this two-promoter system represents a major mechanism in C. elegans, in addition to alternative splicing, that serves to promote tissue-specific expression of protein isoforms. Our finding of the frequent coupling between an internal SL1 and a large immediately upstream intron will make promoters and transcription start sites predictable.
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[
Dev Biol,
2006]
The fusion of the Caenorhabditis elegans uterine anchor cell (AC) with the uterine-seam cell (utse) is an excellent model system for studying cell-cell fusion, which is essential to animal development. We obtained an egg-laying defective (Egl) mutant in which the AC fails to fuse with the utse. This defect is highly specific: other aspects of utse development and other cell fusions appear to occur normally. We find that defect is due to a missense mutation in the
nsf-1 gene, which encodes N-ethylmaleimide-sensitive factor (NSF), an intracellular membrane fusion factor. There are two NSF-1 isoforms, which are expressed in distinct tissues through two separate promoters. NSF-1L is expressed in the uterus, including the AC. We find that
nsf-1 is required cell-autonomously in the AC for its fusion with the utse. Our results establish AC fusion as a paradigm for studying cell fusion at single cell resolution and demonstrate that the NSF ATPase is a key player in this process.
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[
Int J Mol Sci,
2020]
The epidermal growth factor receptor (EGFR) signaling is important for normal development, such as vulval development in <i>Caenorhabditis elegans</i>, and hyperactivation of the EGFR is often associated with cancer development. Our previous report demonstrated the multivulva (Muv) phenotype, a tumor model in <i>C. elegans</i> (<i>jgIs25</i> strain) by engineering LET-23/EGFR with a TKI-resistant human EGFR T790-L858 mutant. Because Rab proteins regulate vesicle transport, which is important for receptor signaling, we screened the RNAi in the <i>jgIs25</i> strain to find the Rabs critical for Muv formation. Herein, we show that <i>
rab-8</i> RNAi and the <i>
rab-8 (-/-)</i> mutation effectively reduce Muv formation. We demonstrate that RABN-8, an ortholog of Rabin8, known as a GEF for Rab8, is also required for Muv formation by promoting the secretion of EGL-17/FGF from vulval precursor cells. In addition, FGFR inhibitors decreased Muv formation mediated by mutant EGFR. Our data suggest that Rab8 and Rabin8 mediate Muv formation through FGF secretion in the EGFR-TKI-resistant nematode model. Furthermore, FGFR-TKIs more effectively inhibit the growth of lung cancer cell lines in H1975 (EGFR T790M-L858R; EGFR-TKI-resistant) than H522 (wild-type EGFR) and H1650 (EGFR exon 19 deletion; EGFR-TKI-sensitive) cells, suggesting that FGFR-TKIs could be used to control cancers with EGFR-TKI-resistant mutations.
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Von Stetina SE, Needleman DJ, Lukin MD, Wu HY, Choi J, Zhou H, Mango SE, Samuel ADT, Landig R, Yu X, Park H, Kucsko G, Maurer PC
[
Proc Natl Acad Sci U S A,
2020]
Understanding the coordination of cell-division timing is one of the outstanding questions in the field of developmental biology. One active control parameter of the cell-cycle duration is temperature, as it can accelerate or decelerate the rate of biochemical reactions. However, controlled experiments at the cellular scale are challenging, due to the limited availability of biocompatible temperature sensors, as well as the lack of practical methods to systematically control local temperatures and cellular dynamics. Here, we demonstrate a method to probe and control the cell-division timing in <i>Caenorhabditis elegans</i> embryos using a combination of local laser heating and nanoscale thermometry. Local infrared laser illumination produces a temperature gradient across the embryo, which is precisely measured by in vivo nanoscale thermometry using quantum defects in nanodiamonds. These techniques enable selective, controlled acceleration of the cell divisions, even enabling an inversion of division order at the two-cell stage. Our data suggest that the cell-cycle timing asynchrony of the early embryonic development in <i>C. elegans</i> is determined independently by individual cells rather than via cell-to-cell communication. Our method can be used to control the development of multicellular organisms and to provide insights into the regulation of cell-division timings as a consequence of local perturbations.
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[
J Bacteriol,
2002]
Pseudomonas aeruginosa is an opportunistic pathogen that may cause severe infections in humans and other vertebrates. In addition, a human clinical isolate of P. aeruginosa, strain PA14, also causes disease in a variety of nonvertebrate hosts, including plants, Caenorhabditis elegans, and the greater wax moth, Galleria mellonella. This has led to the development of a multihost pathogenesis system in which plants, nematodes, and insects have been used as adjuncts to animal models for the identification of P. aeruginosa virulence factors. Another approach to identifying virulence genes in bacteria is to take advantage of the natural differences in pathogenicity between isolates of the same species and to use a subtractive hybridization technique to recover relevant genomic differences. The sequenced strain of P. aeruginosa, strain PAO1, has substantial differences in virulence from strain PA14 in several of the multihost models of pathogenicity, and we have utilized the technique of representational difference analysis (RDA) to directly identify genomic differences between P. aeruginosa strains PA14 and PAO1. We have found that the pilC, pilA, and uvrD genes in strain PA14 differ substantially from their counterparts in strain PAO1. In addition, we have recovered a gene homologous to the ybtQ gene from Yersinia, which is specifically present in strain PA14 but absent in strain PAO1. Mutation of the ybtQ homolog in P. aeruginosa strain PA14 significantly attenuates the virulence of this strain in both G. mellonella and a burned mouse model of sepsis to levels comparable to those seen with PAO1. This suggests that the increased virulence of P. aeruginosa strain PA14 compared to PAO1 may relate to specific genomic differences identifiable by RDA.
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[
ISME J,
2015]
Animal predators can track prey using their keen sense of smell. The bacteriovorous nematode Caenorhabditis elegans employs sensitive olfactory sensory neurons that express vertebrate-like odor receptors to locate bacteria. C. elegans displays odor-related behaviors such as attraction, aversion and adaptation, but the ecological significance of these behaviors is not known. Using a combination of food microbiology and genetics, we elucidate a possible predator-prey relationship between C. elegans and lactic acid bacteria (LAB) in rotting citrus fruit. LAB produces the volatile odor diacetyl as an oxidized by-product of fermentation in the presence of citrate. We show that C. elegans is attracted to LAB when grown on citrate media or Citrus medica L, commonly known as yuzu, a citrus fruit native to East Asia, and this attraction is mediated by the diacetyl odor receptor, ODR-10. We isolated a wild LAB strain and a wild C. elegans-related nematode from rotten yuzu, and demonstrate that the wild nematode was attracted to the diacetyl produced by LAB. These results not only identify an ecological function for a C. elegans olfactory behavior, but contribute to the growing understanding of ecological relationships between the microbial and metazoan worlds.
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[
J Anim Sci Technol,
2023]
The rumen fluids contain a wide range of bacteria, protozoa, fungi, and viruses. The various ruminal microorganisms in the rumen provide nutrients by fermenting the forage they eat. During metabolic processes, microorganisms present in the rumen release diverse vesicles during the fermentation process. Therefore, in this study, we confirmed the function of rumen extracellular vesicles (EVs) and their interaction with the host. We confirmed the structure of the rumen EVs by transmission electron microscope (TEM) and the size of the particles using nanoparticle tracking analysis (NTA). Rumen EVs range in size from 100 nm to 400 nm and are composed of microvesicles, microparticles, and ectosomes. Using the <i>Caenorhabditis elegans</i> smart animal model, we verified the interaction between the host and rumen EVs. Exposure of <i>C. elegans</i> to rumen EVs did not significantly enhance longevity, whereas exposure to the pathogenic bacteria <i>Escherichia coli</i> O157:H7 and <i>Staphylococcus aureus</i> significantly increased lifespan. Furthermore, transcriptome analysis showed gene expression alterations in <i>C. elegans</i> exposed to rumen EVs, with significant changes in the metabolic pathway, fatty acid degradation, and biosynthesis of cofactors. Our study describes the effect of rumen EV interactions with the host and provides novel insights for discovering biotherapeutic agents in the animal industry.
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[
Int J Mol Sci,
2018]
Lymphatic filariasis and onchocerciasis caused by filarial nematodes are important diseases leading to considerable morbidity throughout tropical countries. Diethylcarbamazine (DEC), albendazole (ALB), and ivermectin (IVM) used in massive drug administration are not highly effective in killing the long-lived adult worms, and there is demand for the development of novel macrofilaricidal drugs affecting new molecular targets. A Ca<sup>2+</sup> binding protein, calumenin, was identified as a novel and nematode-specific drug target for filariasis, due to its involvement in fertility and cuticle development in nematodes. As sterilizing and killing effects of the adult worms are considered to be ideal profiles of new drugs, calumenin could be an eligible drug target. Indeed, the <i>Caenorhabditis elegans</i> mutant model of calumenin exhibited enhanced drug acceptability to both microfilaricidal drugs (ALB and IVM) even at the adult stage, proving the roles of the nematode cuticle in efficient drug entry. Molecular modeling revealed that structural features of calumenin were only conserved among nematodes (<i>C. elegans</i>, <i>Brugia malayi</i>, and <i>Onchocerca volvulus</i>). Structural conservation and the specificity of nematode calumenins enabled the development of drugs with good target selectivity between parasites and human hosts. Structure-based virtual screening resulted in the discovery of itraconazole (ITC), an inhibitor of sterol biosynthesis, as a nematode calumenin-targeting ligand. The inhibitory potential of ITC was tested using a nematode mutant model of calumenin.
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[
Food Funct,
2016]
Tsai Tai is one of the most widely consumed Brassica vegetables in Asian countries because of its good taste and its nutritional benefits. This study evaluated the antioxidant capacity and possible associated health benefits of 3 Tsai Tai (Brassica chinensis) varieties, namely, Hon Tsai Tai, Pak Choi and Choi Sum. The DPPH radical scavenging ability and reducing power assays were performed to evaluate the in vitro activities of the extracts. Caenorhabditis elegans was used as an in vivo model for evaluation of beneficial health effects, including antioxidant activity and delayed aging. In vitro, the Hon Tsai Tai extract exhibited higher antioxidant activities than Pak Choi and Choi Sum, and the total phenolic contents were significantly correlated with the DPPH and RP values. In vivo, the three assayed Tsai Tai extracts significantly increased resistance against paraquat-induced oxidative stress with an increase in survival rates from 15% to 28% compared with controls. However, only the extract from Hon Tsai Tai significantly prolonged the lifespan of Caenorhabditis elegans, with an 8% increase in the mean lifespan with respect to controls. Further evidence of antioxidant protection was obtained by assessing ROS production via the DCF assay. The analyses of intracellular SOD activity and MDA content confirmed the existence of an antioxidant protective effect. These results suggest that Tsai Tai might serve as a good source of natural antioxidants, and in particular, Hon Tsai Tai could be explored as a potential dietary supplement to retard aging.
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[
Biochemistry,
1987]
The major intestinal esterase from the nematode Caenorhabditis elegans has been purified to essential homogeneity. Starting from whole worms, the overall purification is 9000-fold with a 10% recovery of activity. The esterase is a single polypeptide chain of Mr 60,000 and is stoichiometrically inhibited by organophosphates. Substrate preferences and inhibition patterns classify the enzyme as a carboxylesterase (EC 3.1.1.1), but the physiological function is unknown. The sequence of 13 amino acid residues at the esterase N- terminus has been determined. This partial sequence shows a surprisingly high degree of similarity to the N-terminal sequence of two carboxylesterases recently isolated from Drosophila mojavensis [Pen, J., van Beeumen, J., & Beintema, J. J. (1986) Biochem. J. 238, 691-699].