Du, Lawrence et al. (2015) International Worm Meeting "Transcriptional control of the C. elegans endoderm master regulator elt-2."

Wu, Allison, Du, Lawrence, Tracy, Sharon, Rifkin, Scott

[International Worm Meeting, 2015]

Cis-regulatory elements are the fundamental control units of gene regulatory networks. They integrate information from transcription factors to organize the expression of a gene in time and space. However, our understanding of how cis-regulatory elements produce a specific spatio-temporal pattern of gene expression is often limited to semi-quantitative descriptions of gene activation. In this study, we determined the quantitative impact of cis-regulatory mutations with single-molecule resolution on the expression levels and variability of elt-2, the key switch for the C. elegans endoderm cell-fate decision and the master regulator of endoderm differentiation. We fused wild-type and mutant versions of the elt-2 promoter to a gfp reporter and inserted these constructs as single copies into a defined location in the C. elegans genome. We then measured early embryonic gfp transcript levels by single-molecule RNA FISH (smFISH). Although the GATA transcription factors that activate elt-2 can bind in vitro to many HGATAR motifs within the elt-2 promoter, mutation of one particular motif had a disproportionate impact on in vivo gene expression. Mutation or deletion of a single highly conserved ACTGATAAG motif at -527 bp upstream of the start codon within the elt-2 promoter abolished the vast majority of embryonic, larval, and adult reporter expression. Absence of this critical motif revealed the presence of low-level, temporally-ectopic, stochastic transcription occurring from secondary HGATAR motifs and proximal promoter regions. Our results indicate that multiple GATA factors converge on a single non-redundant cis-regulatory motif to drive both early embryonic activation as well as later maintenance of gene expression.

Lu M et al. (2020) ACS Omega "Exploring the Toxicology of Depleted Uranium with Caenorhabditis elegans."

Li Y, Lu Y, Li H, Lu M, Wang X, Wang H

[ACS Omega, 2020]

Depleted uranium (DU) is an emerging heavy metal pollutant with considerable environmental and occupational concerns. Its radiotoxicity is known to be low. However, its chemical toxicity should not be ignored. In order to explore the chemical toxicity of DU, the effects of uranyl nitrate, prepared from DU, on the model organism <i>Caenorhabditis elegans</i> were investigated. Chronic exposure to DU did not affect the lifespan or reproduction of the worm. DU had little effect on the physiological processes of <i>C. elegans</i>. Additionally, DU treatment did not make <i>C. elegans</i> more susceptible to UV, heat, or oxidative stress. Interestingly, chronic exposure of DU decreased the <i>in vivo</i> reactive oxygen species-scavenging ability through inhibiting the expression of antioxidant genes <i>ctl</i>-1, <i>ctl</i>-2, <i>ctl</i>-3, <i>gst</i>-7, and <i>gst</i>-10. Chronic but not acute exposure of DU induced a statistically significant degeneration of the dopaminergic (DAergic) neurons of treated worms and promoted the increase of -synuclein aggregation and DAergic neurotoxicity. These findings may raise the public concerns regarding DU as an etiologic agent of Parkinson's disease and underline its potential neurotoxicity.

Jiang GC et al. (2009) Toxicol Sci "Caenorhabditis elegans metallothioneins protect against toxicity induced by depleted uranium."

Evje L, Aschner M, Sturzenbaum SR, Jiang GC, Syversen T, Hughes S

[Toxicol Sci, 2009]

Depleted uranium (DU) is a dense and heavy metal used in armor, ammunition, radiation shielding, and counterbalances. The military usage has led to growing public concern regarding the health effects of DU. In this study, we used the nematode, Caenorhabditis elegans, to evaluate the toxicity of DU and its effects in knockout strains of metallothioneins (MTs), which are small thiol-rich proteins that have numerous functions, such as metal sequestration, transport, and detoxification. We examined nematode viability, the accumulation of uranium, changes in MT gene expression by quantitative reverse transcription-PCR, and the induction of green fluorescent protein under the control of the MT promoters, following exposure to DU. Our results indicate that (1) DU causes toxicity in a dose-dependent manner; (2) MTs are protective against DU exposure; and (3) nematode death by DU is not solely a reflection of intracellular uranium concentration. (4) Furthermore, only one of the isoforms of MTs, metallothionein-1 (mtl-1), appears to be important for uranium accumulation in C. elegans. These findings suggest that these highly homologous proteins may have subtle functional differences and indicate that MTs mediate the response to DU.

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

Aschner M et al. (2009) J Toxicol Environ Health B Crit Rev "Toxicity studies on depleted uranium in primary rat cortical neurons and in Caenorhabditis elegans: what have we learned?"

Jiang GC, Aschner M

[J Toxicol Environ Health B Crit Rev, 2009]

Depleted uranium (DU) is the major by-product of the uranium enrichment process for its more radioactive isotopes, retaining approximately 60% of its natural radioactivity. Given its properties as a pyrophoric and dense metal, it has been extensively used in armor and ammunitions. Questions have been raised regarding the possible neurotoxic effects of DU in humans based on follow-up studies in Gulf War veterans, where a decrease in neurocognitive behavior in a small population was noted. Additional studies in rodents indicated that DU readily traverses the blood-brain barrier, accumulates in specific brain regions, and results in increased oxidative stress, altered electrophysiological profiles, and sensorimotor deficits. This review summarizes the toxic potential of DU with emphasis on studies on thiol metabolite levels, high-energy phosphate levels, and isoprostane levels in primary rat cortical neurons. Studies in Caenorhabditis elegans detail the role of metallothioneins, small thiol-rich proteins, in protecting against DU exposure. In addition, recent studies also demonstrate that only one of the two forms, metallothionein-1, is important in the accumulation of uranium in worms.

Jiang GC et al. (2007) Toxicol Sci "Neurotoxic potential of depleted uranium effects in primary cortical neuron cultures and in Caenorhabditis elegans."

McLaughlin B, Milatovic D, Aschner M, Nass R, Cai J, Gupta RC, Tidwell K, Jiang GC

[Toxicol Sci, 2007]

Depleted uranium (DU) is an extremely dense metal that is used in radiation shielding, counterbalances, armor and ammunition. In light of the public concerns about exposure to DU and its potential role in Gulf War Syndrome, this study evaluated the neurotoxic potential of DU using focused studies on primary rat cortical neurons and the nematode C. elegans. We examined cell viability, cellular energy metabolism, thiol metabolite oxidation, and lipid peroxidation following exposure of cultured neurons to DU, in the form of uranyl acetate. We concurrently evaluated the neurotoxicity of uranyl acetate in C. elegans using various neuronal-green fluourescent protein reporter strains to visualize neurodegeneration. Our studies indicate that uranyl acetate has low cytotoxic potential, and uranium exposure does not result in significant changes in cellular energy metabolism, thiol metabolite oxidation, or lipid peroxidation. Furthermore, our C. elegans studies do not show any significant neurodegeneration following uranyl acetate exposure. Together, these studies suggest that DU, in the form of uranyl acetate, has low neurotoxic potential. These findings should alleviate the some of public concerns regarding depleted uranium as an etiologic agent of neurodegenerative conditions associated with Gulf War Syndrome.

Wu, Allison et al. (2011) International Worm Meeting "Comparing gene expression pattern in the skn-1 intestinal developmental network in C. briggsae, C. remanei, and C. elegans to gain insights into the dynamical functional roles of orthologous genes."

Rifkin, Scott, Wu, Allison, Du, Lawrence

[International Worm Meeting, 2011]

Previous studies have shown that, in the C.elegans skn-1 network, the most downstream gene elt-2 determines the onset of gut development while end-3, end-1, and med-1/2 constrain the gene expression variability. Inboth C. briggsae and C. remanei, there has been a large amount of copy number evolution in this network: there are 5 functionally similar med paralogs in C. remanei , 4 med paralogs in C. briggsae and two orthologs of end-3 in C. briggsae. These potentially functionally similar homologs add extra connections to this intestinal specification network. We want to know how and why these redundant genes are preserved, whether these seemingly redundant connections are really redundant, and whether these connections add to or strengthen specific dynamical network properties, such as buffering of noise or environmenal variation or feedback strength. In this study, we use single-molecule fluorescence in situ hybridization (smFISH) to measure the expression pattern of genes in the skn-1 network in these three species, including end-3 orthologs, end-1 and elt-2. By quantitatively measuring the expression dynamics of these genes, we willustrate the dynamical roles these orthologs play in the intestine development in different nematode species and reveal the effects of gene duplication on dynamical network properties.

Silva N et al. (2016) J Cell Biol "UNC-84: "LINC-ing" chromosome movement and double strand break repair."

Silva N, Jantsch V

[J Cell Biol, 2016]

Assaults to our DNA take place at a high frequency and are incompatible with life. In this issue, Lawrence et al. (2016. J. Cell Biol https://doi.org/10.1083/jcb.201604112) demonstrate that a novel complex links the nucleus with cytoplasmic microtubules for the promotion of DNA repair by homologous recombination.

Felix MA et al. (2002) Hermann, Editeurs des Sciences et des Arts. Paris, France. "Caenorhabditis elegans. Un organisme modele en biologie."

Labouesse M, Segalat L, Felix MA

[Hermann, Editeurs des Sciences et des Arts. Paris, France., 2002]

L'espce Caenorhabditis elegans fut dcrite en 1900 Alger par E. Maupas, qui s'intressait son mode de reproduction hermaphrodite. Plus tard, vers le milieu du vingtime sicle, V. Nigon et ses collaboratuers Lyon tudirent les reorganizations cellulaires accompagnant la fecundation et les premiers clivages. J. Brun isola les preiers mutants morpholgiques.

Sulston JE et al. (1992) Nature "The C. elegans genome sequencing project: a beginning."

Wilson RK, Metzstein MM, Ainscough R, Waterston RH, Coulson AR, Craxton M, Thomas K, Dear S, Qiu L, Staden R, Berks M, Halloran N, Thierry-Mieg J, Hillier L, Sulston JE, Du Z, Durbin RM, Hawkins TL, Green P

[Nature, 1992]

The long-term goal of this project is the elucidation of the complete sequence of the Caenorhabditis elegans genome. During the first year methods have been developed and a strategy implemented that is amenable to large-scale sequencing. The three cosmids sequenced in this initial phase are surprisingly rich in genes, many of which have mammalian homologues.AD - MRC Laboratory of Molecular Biology, Cambridge, UK.FAU - Sulston, JAU - Sulston JFAU - Du, ZAU - Du ZFAU - Thomas, KAU - Thomas KFAU - Wilson, RAU - Wilson RFAU - Hillier, LAU - Hillier LFAU - Staden, RAU - Staden RFAU - Halloran, NAU - Halloran NFAU - Green, PAU - Green PFAU - Thierry-Mieg, JAU - Thierry-Mieg JFAU - Qiu, LAU - Qiu LAU - et al.LA - engPT - Journal ArticleCY - ENGLANDTA - NatureJID - 0410462RN - 0 (Cosmids)SB - IM