de Jong L et al. (2004) Genetics "Thiamine pyrophosphate biosynthesis and transport in the nematode Caenorhabditis elegans."

Hekimi S, de Jong L, Dent J, Meng Y

[Genetics, 2004]

Thiamine (vitamin B1) is required in the diet of animals, and thiamine deficiency leads to diseases such as beri-beri and the Wernicke-Korsakoff syndrome. Dietary thiamine (vitamin B1) consists mainly of thiamine pyrophosphate (TPP), which is transformed into thiamine by gastrointestinal phosphatases before absorption. It is believed that TPP itself cannot be transported across plasma membranes in significant amounts. We have identified a partial loss-of-function mutation in the Caenorhabditis elegans gene (tpk-1) that encodes thiamine pyrophosphokinase, which forms TPP from thiamine at the expense of ATP inside cells. The mutation slows physiological rhythms and the phenotype it produces can be rescued by TPP but not thiamine supplementation. tpk-1 functions cell nonautonomously, as the expression of wild-type tpk-1 in one tissue can rescue the function of other tissues that express only mutant tpk-1. These observations indicate that, in contrast to expectation from previous evidence, TPP can be transported across cell membranes. We also find that thiamine supplementation partially rescues the phenotype of partial loss-of-function mutants of the Na/K ATPase, providing genetic evidence that thiamine absorption, and/or redistribution from the absorbing cells, requires the full activity of this enzyme.

De Jong, Deborah L. et al. (2009) International Worm Meeting "A dsRNA-specific endocytosis pathway for environmental RNAi."

Hunter, Craig P., De Jong, Deborah L.

[International Worm Meeting, 2009]

In C. elegans, ingested double-stranded RNA (dsRNA) triggers environmental RNA interference (RNAi) which spreads systemically throughout the animal and into its progeny. Multiple SID (systemic RNAi defective) proteins are required for the first step, transport of ingested dsRNA across the intestinal lumen. One of these is SID-1, a conserved and broadly expressed transmembrane protein required for importing dsRNA into cells. Expression of SID-1 in Drosophila S2 cells, a heterologous system with no known SID homologs, enables rapid energy-independent uptake of dsRNA. However, in C. elegans, SID-1 is not sufficient to transport dsRNA across the lumenal membrane as SID-2 is also required. SID-2 is a transmembrane protein that, unlike SID-1, is expressed only in the intestine, localizes nearly exclusively to the lumenal membrane, and functions only in the internalization of ingested dsRNA. To investigate whether SID-2 acts as an accessory protein to SID-1 or if it can directly internalize dsRNA, we overexpressed SID-2 in S2 cells and measured uptake of radiolabeled dsRNA. We found that SID-2 selectively imports dsRNA independent of SID-1. In contrast to SID-1, however, SID-2-dependent uptake is energy-dependent, sensitive to endocytosis inhibitors, and requires an acidic pH similar to that found in the intestinal lumen. Additionally, fluorescently-labelled dsRNA colocalizes with vesicular-like intracellular SID-2::GFP. In contrast to C. elegans, C. briggsae is incapable of environmental RNAi and a C. briggsae SID-2 homolog, although similarly expressed and localized, does not mediate uptake of dsRNA when expressed in S2 cells. These results show that SID-1 and SID-2 act by distinct mechanisms and under different conditions and so we propose that they act sequentially. Specifically, we propose that lumenal dsRNA is selectively bound and endocytosed by SID-2 and that SID-1 subsequently transports the dsRNA into the cytoplasm. SID-1 and SID-2 interact in a yeast two-hybrid assay indicating that these internalization steps may be connected by a tissue-specific protein complex.

Deborah L. de Jong et al. (2007) International Worm Meeting "Movement of dsRNA through SID-1 requires accessory proteins."

Deborah L. de Jong, Craig P. Hunter

[International Worm Meeting, 2007]

In C. elegans, the introduction of dsRNA results in sequence-specific gene silencing that can spread between cells and into the progeny by a process known as systemic RNAi. A genetic screen identified three genes required for systemic silencing (Winston et al., Science 295, 2456-2459 2002). The first gene, sid-1 (systemic RNAi defective), encodes a conserved membrane protein expressed in the majority of cell types that is required for intercellular dsRNA transport. Expression of SID-1 in Drosophila S2 cells, a heterologous system with no SID-1 homolog, enables rapid energy-independent uptake of long dsRNA (Feinberg & Hunter, Science 301, 1545-1547 2003). Another gene identified from the screen, sid-2, encodes a membrane protein that localizes to the lumenal membrane of intestinal cells and is required for the uptake of dsRNA from the environment. (Winston et al, 2007). To identify proteins that may regulate SID-1 activity or localization, we performed a yeast two hybrid screen with a SID-1 bait. We have identified many SID-1 interacting proteins, but SID-1 itself was the most commonly recovered clone, suggesting that SID-1 may form a homomeric complex. Another protein identified in this screen was SID-2. Since SID-1 and SID-2 are both required during the import of externally provided dsRNA, their interaction suggests that uptake of dsRNA from the environment is mediated by a tissue-specific protein complex. We propose two possible mechanisms: These proteins function together at the lumenal membrane to facilitate SID-1 channel activity or SID-2 mediates an endocytosis-dependent step whereby vesicle-encased dsRNA enters the cell and is released into the cytoplasm through SID-1. To differentiate between these possibilities, we are expressing both SID-1 and SID-2 individually and together in Drosophila S2 cells and inhibiting endocytotic processes to determine what impact(s) this has on dsRNA uptake.

Eberhardt AG et al. (2008) Vet Parasitol "The Strongyloides (Nematoda) of sheep and the predominant Strongyloides of cattle form at least two different, genetically isolated populations."

Mayer WE, Eberhardt AG, Streit A, Bonfoh B

[Vet Parasitol, 2008]

Strongyloides sp. (Nematoda) are very wide spread small intestinal parasites of vertebrates that can form a facultative free-living generation. Most authors considered all Strongyloides of farm ruminants to belong to the same species, namely Strongyloides papillosus (Wedl, 1856). Here we show that, at least in southern Germany, the predominant Strongyloides found in cattle and the Strongyloides found in sheep belong to separate, genetically isolated populations. While we did find mixed infections in cattle, one form clearly dominated. This variety, in turn, was never found in sheep, indicating that the two forms have different host preferences. We also present molecular tools for distinguishing the two varieties, and an analysis of their phylogenetic relationship with the human parasite Strongyloides stercoralis and the major laboratory model species Strongyloides ratti. Based on our findings we propose that Strongyloides from sheep and the predominant Strongyloides from cattle should be considered separate species as it had already been proposed by [Brumpt, E., 1921. Recherches sur le determinisme des sexes et de l''evolution des Anguillules parasites (Strongyloides). Comptes rendu hebdomadaires des seances et memoires de la Societe de Biologie et de ses filiales 85, 149-152], but was largely ignored by later authors. For nomenclature, we follow [Brumpt, E., 1921. Recherches sur le determinisme des sexes et de l''evolution des Anguillules parasites (Strongyloides). Comptes rendu hebdomadaires des seances et memoires de la Societe de Biologie et de ses filiales 85, 149-152] and use the name S. papillosus for the Strongyloides of sheep and the name Strongyloides vituli for the predominant Strongyloides of cattle.

Artal-Sanz M et al. (2006) Biotechnol J "Caenorhabditis elegans: a versatile platform for drug discovery."

Artal-Sanz M, Tavernarakis N, de Jong L

[Biotechnol J, 2006]

Drug discovery and drug target identification are two intimately linked facets of intervention strategies aimed at effectively combating pathological conditions in humans. Simple model organisms provide attractive platforms for devising and streamlining efficient drug discovery and drug target identification methodologies. The nematode worm Caenorhabditis elegans has emerged as a particularly convenient and versatile tool that can be exploited to achieve these goals. Although C. elegans is a relatively modern addition to the arsenal of model organisms, its biology has already been investigated to an exceptional level. This, coupled with effortless handling and a notable low cost of cultivation and maintenance, allows seamless implementation of high-throughput drug screening approaches as well as in-depth genetic and biochemical studies of the molecular pathways targeted by specific drugs. In this review, we introduce C. elegans as a model organism with significant advantages toward the identification of molecular drug targets. In addition, we discuss the value of the worm in the development of drug screening and drug evaluation protocols. The unique features of C. elegans, which greatly facilitate drug studies, hold promise for both deciphering disease pathogenesis and formulating educated and effective therapeutic interventions.

Zarkower D et al. (1994) Worm Breeder's Gazette "mab-3 YAC Rescue"

De Bono M, Hodgkin JA, Zarkower D

[Worm Breeder's Gazette, 1994]

mab-3 YAC rescue David Zarkower, Mario de Bono, and Jonathan Hodgkin MRC Laboratory of Molecular Biology, Cambridge, England

Clynen E et al. (2009) Ann N Y Acad Sci "Identification of new members of the (short) neuropeptide F family in locusts and Caenorhabditis elegans."

Schoofs L, Clynen E, Husson SJ

[Ann N Y Acad Sci, 2009]

Both the long and short neuropeptides F (NPF) represent important families of invertebrate neuropeptides that have been implicated in the regulation of reproduction and feeding behavior. In the present study, two short NPFs (SNRSPS(L/I)R(L/I)RFamide and SPS(L/I)R(L/I)RFamide) were de novo sequenced by mass spectrometry in two major pest insects, the desert locust Schistocerca gregaria and the African migratory locust Locusta migratoria. They are two of the most widespread peptides in the locust neuroendocrine system. A peptide that was previously reported to accelerate egg development in S. gregaria is shown to represent a truncated form of long NPF. This peptide is most likely derived by a novel processing mechanism involving cleavage at RY. In addition, an NPF peptide from the nematode Caenorhabditis elegans was isolated and sequenced by tandem mass spectrometry.

Hunter CP et al. (1991) International C. elegans Meeting "NON-AUTONOMY OF HER-1 FUNCTION IMPLICATES CELL INTERACTIONS IN C. ELEGANS SEX DETERMINATION."

Hunter CP, Wood WB

[International C. elegans Meeting, 1991]

Activity of the her-l gene is required for normal male development in C. elegans. Loss-of-function her-l mutations cause feminization of XO animals (normally male) to produce fertile hermaphrodites, while gain-of-function her-l mutations cause masculinization of XX animals ( normally hermaphrodite) to produce pseudo-males. Genetic analysis indicated that her-l functions early in the hierarchy of regulatory interactions among the major sex determination genes (1). We have analyzed her-l genetic mosaics to determine which cells must express her-l for wild-type male development. If her-l functions cell- autonomously, then in XO animals her-l (+) cells will follow male fates, and her-1(-) cells will follow hermaphrodite fates. If her-l or a her-l regulated activity functions non-autonomously, then the her-l genotype of a cell may not determine its sexual phenotype. The phenotypes of XO her-l genetic mosaics are variable, but clearly show that both her-1(-) and her-l (+) cells can follow either hermaphrodite or male fates. We conclude that her-l is neither necessary nor sufficient to cell-autonomously determine male sexual phenotypes and, therefore, that her-l or a her-l regulated activity must be able to function non-autonomously. The observed patterns of non-autonomous effects suggest that many or all cells express and respond to her-l activity. These findings implicate cell interactions in C. elegans sex determination. Earlier genetic analysis indicated that her-l might directly control tra-2 activity (1). Molecular characterization of the gene products of her-l and tra-2 (see abstracts by M. Perry et al. and P. Kuwabara et al) is consistent with a model in which a secreted ligand encoded by her-l interacts with a cell-surface receptor encoded by tra-2. We will discuss the possible role of such an interaction in coordinating the sex determination decision.

Forrester S et al. (2007) Foodborne Pathog Dis "Evaluation of the pathogenicity of Listeria spp. in Caenorhabditis elegans."

Schwab U, Wiedmann M, Hoose WA, Milillo SR, Forrester S

[Foodborne Pathog Dis, 2007]

Caenorhabditis has proven to be a useful model for studying host-pathogen interactions as well as the ability of nematodes to serve as vectors for the dispersal of foodborne pathogens. In this study, we evaluated whether C. elegans can serve as a host for Listeria spp. While there was an effect of growth media on C. elegans killing, C. elegans exposed to L. monocytogenes and L. innocua pregrown in Luria-Bertani medium showed reduced survival when compared to nonpathogenic E. coli OP50, while L. seeligeri showed survival similar to E. coli OP50. In a preference assay, C. elegans preferred E. coli over L. monocytogenes and L. innocua, but showed no preference between L. monocytogenes and L. innocua. A gentamicin assay indicated that L. monocytogenes did not persist within the C. elegans intestinal tract. Our findings that L. monocytogenes and L. innocua strains tested have equally deleterious effects on C. elegans and that L. monocytogenes did not establish intestinal infection conflict with other recently published results, which found intestinal infection and killing of C. elegans by L. monocytogenes. Further studies are thus needed to clarify the interactions between L. monocytogenes and C. elegans, including effects of environmental conditions and strain differences on killing and intestinal infection.

De Stasio E et al. (1994) Worm Breeder's Gazette "Mutagenesis of C. elegans Using N-ethyl-N-nitrosourea."

De Stasio E, Stanislaus D, Lephoto C

[Worm Breeder's Gazette, 1994]

Mutagenesis of C. elegans using N-ethyl-N-nitrosourea Elizabeth De Stasio, Dinesh Stanislaus and Catherine Lephoto. Department of Biology, Lawrence University, Appleton, Wl 54911