Catherine Au et al. (2008) C.elegans Neuronal Development Meeting "Manganese Transport in C. elegans: the Role of the SMF Genes"

Michael Aschner, Catherine Au, Keith Erikson, Joel Anderson, Alexandre Benedetto

[C.elegans Neuronal Development Meeting, 2008]

Manganese (Mn) is an essential trace element for normal human development and vital enzymatic activities. However, occupational exposure to high levels of Mn has been implicated in a Parkinsonian-like syndrome known as manganism. Since the initial discovery of Mn-induced pathogenesis, much effort has been put forth in order to study the mechanism of uptake and the potential adverse effect of manganism. In the present study, we use C. elegans to understand the mechanisms of Mn transport across biological membranes. In wildtype (WT) C. elegans, acute Mn treatment induces strong osmotic defects eventually leading to death. It was shown in mammalian systems that Mn can cross the blood-brain barrier through the divalent metal transporter DMT1/NRAMP2. The C. elegans genome encodes three DMT1 orthologues (SMF-1, SMF-2, SMF-3). When compared with WT, C. elegans deletion-mutants smf-1(eh5) and smf-3(ok1035) exhibited an increased resistance to Mn exposure while smf-2(gk1330) was more sensitive. In accordance with those observations, the Mn content ofsmf-2(gk1330) after Mn exposure was greater than WT, smf-1(eh5) and smf-3(ok1035), the latter taking up less Mn than all the other mutants. SMF-1::GFP and SMF-3::GFP were found co-expressed in the gut and the major epidermis hyp7, which likely account for most Mn uptake, while SMF-2::GFP was mainly expressed in the mc1-3 and vpi1-6 cells. The combination of our data allows us to propose a model for Mn transport and SMF roles in C. elegans. This work establishes C. elegans as a valuable model to study Mn transport and toxicity. Given the similarity of DMT1/NRAMP2-related genes from worms to human, it may also provide insights into the Mn-dependent regulation of the NRAMP family of proteins in vertebrates. This project is funded by R01 ES10563 to MA.

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

Gallud A et al. (2019) Sci Rep "Cationic gold nanoparticles elicit mitochondrial dysfunction: a multi-omics study."

Ostberg N, Xue D, Gogvadze V, Ytterberg J, Skoog T, Moya S, Gallud A, Ruiz J, Kere J, Fadeel B, Katayama S, Zubarev R, Astruc D, Chen YZ, Kloditz K

[Sci Rep, 2019]

Systems biology is increasingly being applied in nanosafety research for observing and predicting the biological perturbations inflicted by exposure to nanoparticles (NPs). In the present study, we used a combined transcriptomics and proteomics approach to assess the responses of human monocytic cells to Au-NPs of two different sizes with three different surface functional groups, i.e., alkyl ammonium bromide, alkyl sodium carboxylate, or poly(ethylene glycol) (PEG)-terminated Au-NPs. Cytotoxicity screening using THP-1 cells revealed a pronounced cytotoxicity for the ammonium-terminated Au-NPs, while no cell death was seen after exposure to the carboxylated or PEG-modified Au-NPs. Moreover, Au-NR3+ NPs, but not the Au-COOH NPs, were found to trigger dose-dependent lethality in vivo in the model organism, Caenorhabditis elegans. RNA sequencing combined with mass spectrometry-based proteomics predicted that the ammonium-modified Au-NPs elicited mitochondrial dysfunction. The latter results were validated by using an array of assays to monitor mitochondrial function. Au-NR3+ NPs were localized in mitochondria of THP-1 cells. Moreover, the cationic Au-NPs triggered autophagy in macrophage-like RFP-GFP-LC3 reporter cells, and cell death was aggravated upon inhibition of autophagy. Taken together, these studies have disclosed mitochondria-dependent effects of cationic Au-NPs resulting in the rapid demise of the cells.

Hu CC et al. (2018) Sci Rep "Toxic Effects of Size-tunable Gold Nanoparticles on Caenorhabditis elegans Development and Gene Regulation."

Wu GH, Lai SF, Wagner OI, Hwu Y, Yen TJ, Hu CC, Muthaiyan Shanmugam M

[Sci Rep, 2018]

We utilized size-tunable gold nanoparticles (Au NPs) to investigate the toxicogenomic responses of the model organism Caenorhabditis elegans. We demonstrated that the nematode C. elegans can uptake Au NPs coated with or without 11-mercaptoundecanoic acid (MUA), and Au NPs are detectable in worm intestines using X-ray microscopy and confocal optical microscopy. After Au NP exposure, C. elegans neurons grew shorter axons, which may have been related to the impeded worm locomotion behavior detected. Furthermore, we determined that MUA to Au ratios of 0.5, 1 and 3 reduced the worm population by more than 50% within 72 hours. In addition, these MUA to Au ratios reduced the worm body size, thrashing frequency (worm mobility) and brood size. MTT assays were employed to analyze the viability of cultured C. elegans primary neurons exposed to MUA-Au NPs. Increasing the MUA to Au ratios increasingly reduced neuronal survival. To understand how developmental changes (after MUA-Au NP treatment) are related to changes in gene expression, we employed DNA microarray assays and identified changes in gene expression (e.g., clec-174 (involved in cellular defense), cut-3 and fil-1 (both involved in body morphogenesis), dpy-14 (expressed in embryonic neurons), and mtl-1 (functions in metal detoxification and homeostasis)).

Wang M et al. (2023) Int J Nanomedicine "Gold Nanoparticles Reduce Food Sensation in Caenorhabditis elegans via the Voltage-Gated Channel EGL-19."

Yang B, Sun N, Hu J, Wang M, Wang L, Mo J, Wang D, Zhang Z, Su M

[Int J Nanomedicine, 2023]

INTRODUCTION: The increasing use of gold nanoparticles (Au NPs) in the medical field has raised concerns about the potential adverse effect of Au NPs exposure. However, it is difficult to assess the health risks of Au NPs exposure at the individual organ level using current measurement techniques. METHODS: single cell RNA-seq databases. RESULTS: to NaCl, which was consistent with the decrease in calcium transit of ASEL. Further studies confirmed that the reduced calcium transit was dependent on voltage-gated calcium channel EGL-19. The neuropeptide INS-22 was partially involved in Au NPs-induced NaCl sensation defect. Therefore, we proposed that Au NPs reduced the calcium transit in the ASEL neuron through egl-19-dependent calcium channels. It was partially regulated by the DAF-16 targeting neuropeptide INS-22. DISCUSSION: Our results demonstrate that Au NPs affect food sensation by reducing the calcium transit in ASEL neurons, which further leads to reduced pharynx pumping and feeding defects. The toxicology studies of Au NPs from worms have great potential to guide the usage of Au NPs in the medical field such as targeted drug delivery.

Tsyusko O et al. (2012) Environ Sci Technol "Toxicogenomic responses of the model organism Caenorhabditis elegans to gold nanoparticles."

Blalock EM, Bertsch PM, Tsyusko O, Joice G, Tseng MT, Starnes D, Spurgeon DJ, Unrine JM

[Environ Sci Technol, 2012]

We used Au nanoparticles (Au-NPs) as a model for studying particle-specific effects of manufactured nanomaterials (MNMs) by examining the toxicogenomic responses in a model soil organism, Caenorhabditis elegans . Global genome expression for nematodes exposed to 4-nm citrate-coated Au-NPs at the LC(10) level (5.9 mg-L(-1)) revealed significant differential expression of 797 genes. The levels of expression for five genes (apl-1, dyn-1, act-5, abu-11, and hsp-4) were confirmed independently with qRT-PCR. Seven common biological pathways associated with 38 of these genes were identified. Up-regulation of 26 pqn/abu genes from noncanonical unfolded protein response (UPR) pathway and molecular chaperones (hsp-16.1, hsp-70, hsp-3, and hsp-4) were observed and are likely indicative of endoplasmic reticulum stress. Significant increase in sensitivity to Au-NPs in a mutant from noncanonical UPR (pqn-5) suggests possible involvement of the genes from this pathway in a protective mechanism against Au-NPs. Significant responses to Au-NPs in endocytosis mutants (chc-1 and rme-2) provide evidence for endocytosis pathway being induced by Au-NPs. These results demonstrate that Au-NPs are bioavailable and cause adverse effects to C. elegans by activating both general and specific biological pathways. The experiments with mutants further support involvement of several of these pathways in Au-NP toxicity and/or detoxification.

McCullough AJ et al. (1993) Mol Cell Biol "AU-rich intronic elements affect pre-mRNA 5' splice site selection in Drosophila melanogaster."

McCullough AJ, Schuler MA

[Mol Cell Biol, 1993]

cis-spliced nuclear pre-mRNA introns found in a variety of organisms, including Tetrahymena thermophila, Drosophila melanogaster, Caenorhabditis elegans, and plants, are significantly richer in adenosine and uridine residues than their flanking exons are. The functional significance of this intronic AU richness, however, has been demonstrated only in plant nuclei. In these nuclei, 5' and 3' splice sites are selected in part by their positions relative to AU-rich elements spread throughout the length of an intron. Because of this position-dependent selection scheme, a 5' splice site at the normal (+1) exon-intron boundary having only three contiguous consensus nucleotides can compete effectively with an enhanced exonic site (-57E) having nine consensus nucleotides and outcompete an enhanced site (+106E) embedded within the AU-rich intron. To determine whether transitions from AU-poor exonic sequences to AU-rich intronic sequences influence 5' splice site selection in other organisms, alleles of the pea rbcS3A1 intron were expressed in Drosophila Schneider 2 cells, and their splicing patterns were compared with those in tobacco nuclei. We demonstrate that this heterologous transcript can be accurately spliced in transfected Drosophila nuclei and that a +1 G-to-A knockout mutation at the normal splice site activates the same three cryptic 5' splice sites as in tobacco. Enhancement of the exonic (-57) and intronic (+106) sites to consensus splice sites indicates that potential splice sites located in the upstream exon or at the 5' exon-intron boundary are preferred in Drosophila cells over those embedded within AU-rich intronic sequences. In contrast to tobacco, in which the activities of two competing 5' splice sites upstream of the AU-rich intron are modulated by their proximity to the AU transition point, D. melanogaster utilizes the upstream site which has a higher proportion of consensus nucleotides. The enhanced version of the cryptic intronic site is efficiently selected in D. melanogaster when the normal +1 site is weakened or discrete AU-rich elements upstream of the +106E site are disrupted. Selection of this internal site in tobacco requires more drastic disruption of these motifs. We conclude that 5' splice site selection in Drosophila nuclei is influenced by the intrinsic strengths of competing sites and by the presence of AU-rich intronic elements but to a different extent than in tobacco.

Tullet, Jennifer et al. (2015) International Worm Meeting "The SKN-1/Nrf2 transcription factor protects against oxidative damage and promotes longevity in C. elegans by distinct mechanisms."

Gems, David, Au, Catherine, Clarke, Emily, Tullet, Jennifer, Young, Adelaide

[International Worm Meeting, 2015]

In C. elegans the skn-1 gene encodes a transcription factor that resembles mammalian Nrf2 and activates the detoxification response. skn-1 promotes resistance to oxidative stress and also protects against ageing, and it has been suggested that the former causes that latter - consistent with the theory that oxidative damage causes ageing. While long-lived strains are often stress resistant, they are not always. Moreover, a number of studies suggest that molecular damage may not in fact be the cause of ageing, particularly in C. elegans. Here we present work suggesting that effects of SKN-1 on stress resistance and longevity can be dissociated. We focus on the role of SKN-1 downstream of DAF-16/FoxO, another key transcription factor that controls growth, metabolism and ageing. Over-expression of DAF-16 promotes stress resistance and can increase longevity. Recent analysis of transcript and chromatin profiling implies that DAF-16 regulates relatively few genes directly, many of which encode other regulatory proteins. We show that one of these targets is skn-1 and that this transcription factor is required for the stress resistance caused by over-expressing DAF-16. However skn-1 is not required for DAF-16-mediated lifespan extension. Moreover, knock-down of skn-1 expression can increase molecular damage levels without decreasing lifespan. These findings suggest that SKN-1 mediates lifespan extension by a means other than protection against damage, and elucidate the gene-regulatory network centered on DAF-16. We also present evidence that the mechanisms of life extension by daf-2 mutation or DAF-16 over-expression are mechanistically different.

Ezcurra, Marina et al. (2015) International Worm Meeting "A massive increase in lipid and protein content in aging hermaphrodites."

Gems, David, Benedetto, Alexandre, Au, Catherine, Sornda, Thanet, Gilliat, Ann, Ezcurra, Marina

[International Worm Meeting, 2015]

One view of aging is as the set of endogenously-generated pathologies that increase in late life, some of which contribute to age-related mortality. This implies that to understand aging in C. elegans one needs to characterize age-related pathologies and their development, identify the processes that promote pathology development, and establish which pathologies cause death. To this end we have established methodologies for simultaneous assessment of a range of late-life pathologies of aging C. elegans. Using these we have identified a burst of rapid pathogenesis involving gross anatomical changes, which occurs mainly between day 4 and 10 of adulthood in N2 hermaphrodites. One such pathology results from the continuation of yolk production after reproduction has ceased, causing accumulation of yolk and in detrimental effects on the worm in later life. Yolk is a lipoprotein complex of yolk proteins (vitellogenins) and lipids, including phospholipids and triglycerides. Continued yolk synthesis leads to an eventual ~8-fold increase in the major yolk protein component YP170. Yolk proteins eventually constitute ~75% of total worm protein content, and there is an ~10-fold age increase in total protein content per worm. In old animals, up to 50% of the body cavity can be filled up with yolk pools, which stain with the lipophilic dye Bodipy, and there is a ~5-fold increase in overall triglyceride content. Thus, elderly hermaphrodites experience severe hyperproteinemia and steatosis. Knock down of vitellogenins using vit-5 + vit-6 RNAi suppressed yolk accumulation and the development of other age-related pathologies, and increased lifespan. Conversely, suppressing yolk uptake by oocytes by rme-2 RNAi increased yolk pool accumulation, altered other pathologies and decreased lifespan, suggesting that ectopic yolk deposition has toxic effects. In long-lived daf-2 insulin/IGF-1 receptor mutants this yolk hypertrophy is suppressed. Together, these data suggest that aging C. elegans hermaphrodites undergo an overgrowth phase during early adulthood, characterized by vigorous biological activity rather than loss of function. This overgrowth phase results in, among other things, excess biosynthesis and the accumulation of large pools containing vitellogenic proteins and lipids in the body cavity, which have toxic effects and result in the acceleration of age-related pathologies and shortening of lifespan.

Conrad RC et al. (1995) RNA "SL1 trans-splicing specified by AU-rich synthetic RNA inserted at the 5' end of Caenorhabditis elegans pre-mRNA."

Blumenthal TE, Lea K, Conrad RC

[RNA, 1995]

In Caenorhabditis elegans, pre-mRNAs of many genes are trans-spliced to one of two spliced leaders, SL1 or SL2. Some of those that receive exclusively SL1 have been characterized as having at their 5' ends outrons, AU-rich sequences similar to introns followed by conventional 3' splice sites. Comparison of outrons from many different SL1-specific C. elegans genes has not revealed the presence of any consensus sequence that might encode SL1-specificity. In order to determine what parameters influence the splicing of SL1, we performed in vivo experiments with synthetic splice sites. Synthetic AU-rich RNA, 51 nt or longer, placed upstream of a consensus 3' splice site resulted in efficient trans-splicing. With all sequences tested, this trans-splicing was specifically to SL1. Thus, no information beyond the presence of AU-rich RNA at least as long as the minimum-length C. elegans intron, followed by a 3' splice site, is required to specify trans-splicing or for strict SL1 specificity.