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Methods Mol Biol,
2006]
Whether by patch-clamp techniques or the use of fluorescent vital dyes, measurements of transepithelial ion flux in mammals are limited by cell accessibility. Furthermore, redundant functions and complex regulatory mechanisms can mask loss-of-function phenotypes through compensatory mechanisms. In this chapter, we present a technique whereby the optically transparent nematode Caenorhabditis elegans, engineered to express a fluorescent pH indicator protein, can be used to study how intracellular pH (pHi) fluctuates in response to environmental and/or experimental challenge. By using a live whole animal model, systemic, and even behavioral relationships to individual cellular pHi can be inferred. In combination with dye loading of excised or cultured cells, this technique also provides a powerful means of contrasting these relationships to biophysical measurements of ion flux.
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Curr Biol,
2003]
In touch receptor cells of the nematode, two channel subunits of the DEG/ENaC family have long been thought to carry out mechanotransduction. New work shows that these channel subunits are responsible for events that occur within 50 milliseconds of transduction, and may be the transduction channel subunits themselves.
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Curr Opin Genet Dev,
1996]
The sequencing of the 100 Mb Caenorhabditis elegans genome-containing approximately 14,000 genes-is approximately 50% complete. One of its most interesting features is its compactness; introns and intergenic distances are unusually small and, surprisingly, approximately 25% of genes are contained in polycistronic transcription units (operons) with only approximately 100 bp between genes.
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Semin Nephrol,
2006]
The vacuolar H(+)-ATPase is a multisubunit protein consisting of a peripheral catalytic domain (V(1)) that binds and hydrolyzes adenosine triphosphate (ATP) and provides energy to pump H(+) through the transmembrane domain (V(0)) against a large gradient. This proton-translocating vacuolar H(+)-ATPase is present in both intracellular compartments and the plasma membrane of eukaryotic cells. Mutations in genes encoding kidney intercalated cell-specific V(0)
a4 and V(1) B1 subunits of the vacuolar H(+)-ATPase cause the syndrome of distal tubular renal acidosis. This review focuses on the function, regulation, and the role of vacuolar H(+)-ATPases in renal physiology. The localization of vacuolar H(+)-ATPases in the kidney, and their role in intracellular pH (pHi) regulation, transepithelial proton transport, and acid-base homeostasis are discussed.
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Curr Opin Cell Biol,
2013]
With its invariant cell lineage, easy genetics and small genome, the nematode Caenorhabditis elegans has emerged as one of the prime models in developmental biology over the last 50 years. Surprisingly however, until a decade ago very little was known about nuclear organization in worms, even though it is an ideal model system to explore the link between nuclear organization and cell fate determination. Here, we review the latest findings that exploit the repertoire of genetic tools developed in worms, leading to the identification of important sequences and signals governing the changes in chromatin tridimensional architecture. We also highlight parallels and differences to other model systems.
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[
Science,
1998]
Neurotransmitter receptors, neurotransmitter synthesis and release pathways, and heterotrimeric GTP-binding protein (G protein)-coupled second messenger pathways are highly conserved between Caenorhabditis elegans and mammals, but gap junctions and chemosensory receptors have independent origins in vertebrates and nematodes. Most ion channels are similar to vertebrate channels but there are no predicted voltage-activated sodium channels. The C. elegans genome encodes at least 80 potassium channels, 90 neurotransmitter-gated ion channels, 50 peptide receptors, and up to 1000 orphan receptors that may be chemoreceptors. For many gene families, C. elegans has both conventional members and divergent outliers with weak homology to known genes; these outliers may provide insights into previously unknown functions of conserved protein families.
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Trends Genet,
2001]
Large-scale sequencing efforts are providing new perspectives on similarities and differences among species. Sequences encoding nuclear receptor (NR) transcription factors furnish one striking example of this. The three complete or nearly complete metazoan genome sequences - those of the nematode Caenorhabditis elegans, the fruit fly (Drosophila melanogaster) and the human - reveal dramatically different numbers of predicted NR genes: 270 for the nematode, 21 for the fruit fly and similar to 50 for the human. Although some classes of NRs present in insects and mammals are also represented among the nematode genes, most of the C. elegans NR sequences are distinct from those known in other phyla. Questions regarding the evolution and function of NR genes in nematodes, framed by the abundance and diversity of these genes in the C. elegans genome, are the focus of this article.
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[
Nippon Yakurigaku Zasshi,
2003]
Ivermectin is an oral semi-synthetic lactone anthelmintic agent derived from avermectins isolated from fermentation products of Streptomyces avermitilis. Ivermectin showed a concentration-dependent inhibitory effect on motility of a free-living nematode, Caenorhabditis elegans (C. elegans). There exist specific binding sites having a high affinity for ivermectin in the membrane fraction of C. elegans, and a strong positive correlation was detected between the affinity for these binding sites and the suppressive effect on motility of C. elegans in several ivermectin-related substances. These results suggested that the binding to these binding sites is important for the nematocidal activity of ivermectin. In oocytes of Xenopus laevis injected with the Poly (A)(+) RNA of C. elegans, expression of a chloride channel, which is irreversibly activated by ivermectin, was recognized. The pharmacological properties of this channel suggest that the ivermectin-sensitive channel is a glutamate-activated chloride channel. As to the glutamate-activated chloride channel, two subtypes (GluCl-alpha and GluCl-beta) were cloned, suggesting these subtypes constitute the glutamate-activated chloride channel. These findings suggest that ivermectin binds to glutamate-activated chloride channels existing in nerve or muscle cells of nematode with a specific and high affinity, causing hyperpolarization of nerve or muscle cells by increasing permeability of chloride ion through the cell membrane, and as a result, the parasites are paralyzed to death. In experimental infections in sheep and cattle, ivermectin exhibited potent dose-dependent anthelmintic effects on Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Oesphagostomum, and Dictyocaulus. Anthelmintic effects were reported also in dogs, horses, and humans infected with Strongyloides. In the clinical Phase III trial in Japan, 50 patients infected with Strongyloides stercoralis were administered approx. 200 micro g/kg of ivermectin to be given orally twice at an interval of 2 weeks. As a result, the Strongyloides stercoralis-eradicating rate was 98.0% (49/50).
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Nucleus,
2015]
The nuclear envelope consists of 2 membranes separated by 30-50 nm, but how the 2 membranes are evenly spaced has been an open question in the field. Nuclear envelope bridges composed of inner nuclear membrane SUN proteins and outer nuclear membrane KASH proteins have been proposed to set and regulate nuclear envelope spacing. We tested this hypothesis directly by examining nuclear envelope spacing in Caenorhabditis elegans animals lacking UNC-84, the sole somatic SUN protein. SUN/KASH bridges are not required to maintain even nuclear envelope spacing in most tissues. However, UNC-84 is required for even spacing in body wall muscle nuclei. Shortening UNC-84 by 300 amino acids did not narrow the nuclear envelope space. While SUN proteins may play a role in maintaining nuclear envelope spacing in cells experiencing forces, our data suggest they are dispensable in most cells.
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Genetics,
2016]
Sleep is widely recognized as essential, but without a clear singular function. Inadequate sleep impairs cognition, metabolism, immune function, and many other processes. Work in genetic model systems has greatly expanded our understanding of basic sleep neurobiology as well as introduced new concepts for why we sleep. Among these is an idea with its roots in human work nearly 50 years old: sleep in early life is crucial for normal brain maturation. Nearly all known species that sleep do so more while immature, and this increased sleep coincides with a period of exuberant synaptogenesis and massive neural circuit remodeling. Adequate sleep also appears critical for normal neurodevelopmental progression. This article describes recent findings regarding molecular and circuit mechanisms of sleep, with a focus on development and the insights garnered from models amenable to detailed genetic analyses.