An enhanced C. elegans based platform for toxicity assessment

Abstract

There is a well-defined regulatory framework governing the approval of chemicals for use as pharmaceuticals or release into the environment. Toxicity assessment is thus a major hurdle in the compound discovery pipeline, currently involving large scale animal testing. The search for alternative testing platforms is therefore an important priority. We have developed a convenient, low cost assay utilising the nematode Caenorhabditis elegans, to rapidly assess both acute toxicity and developmental and reproductive toxicity (DART). However the worm is protected by a robust cuticle that forms a barrier to chemical uptake. We assessed mutants with altered cuticle properties to identify sensitized strains optimized for toxicity assays. Evaluating the trade-off between increased permeability and reduced fitness identifies bus-5(br19) as the most suitable strain for chemical exposure. We demonstrate the applicability of this assay for a range of chemicals with differing properties, including a modified exposure protocol for volatile or less soluble compounds. This work enhances the effectiveness of C. elegans for convenient toxicity assessment, which could contribute to a reduction in the use of vertebrates particularly at the crucial early stages of product development. Strains identified in this work will also enhance the sensitivity of C. elegans based drug discovery platforms.

Modeling Parkinson’s Disease in C. elegans

“…Compounds can be added to the solid agar plates on which the worms are maintained, or worms can be grown in liquid culture and the compounds added directly to the culture medium. While worms have a thick cuticle that can limit the ability of compounds to enter the worm, genetically modified strains are available with increased drug permeability [ 122 ]. Previous work has examined the beneficial effect of specific compounds in genetic and toxicant models of PD, including acetaminophen [ 123 ] and valproic acid [ 124 ].…”

A conserved retromer-independent function for RAB-6.2/RAB6 inC. elegansepidermis integrity

“…Specifically, the srf-3(e2689) mutation in the nucleotide sugar transporter gene increases fragility but does not affect sensitivity to tetramisole, in contrast, the bus-17(e2800) mutation in the glycosyltransferase gene results in fragility and hypersensitivity to tetramisole (Fig. 7E,F) (Xiong et al, 2017). Taken together, these data suggest that RAB-6.2 may be necessary for cuticular surface glycosylation, as has been shown for many genes that, when mutated, confer resistance to M. nematophilum infection.…”

“…Several mutants that are resistant to M. nematophilum have been isolated and cloned to genes associated with glycosylation of the cuticular surface, suggesting that failure to exhibit a dar phenotype in response to exposure to M. nematophilum is a good assay for cuticular glycosylation defects (Gravato-Nobre et al, 2005Hodgkin et al, 2000;Höflich et al, 2004). Significantly, some of these mutants also affect cuticle integrity as assayed by resistance to sodium hypochlorite treatment (Xiong et al, 2017;Gravato-Nobre et al, 2005). We set out to investigate whether rab-6.2(ok2254) affects the dar phenotype in response to M. nematophilum infection as an indirect assay for surface glycosylation defects.…”

C. elegansELT-3 regulates cuticle collagen expression in response to environmental stimuli

“…In the wild, C. elegans is exposed to frequent changes in environment and has developed strategies to cope with pathogens, temperature, osmolarity, and intermittent availability of oxygen or food. For C. elegans , the first barrier against environmental insults is the cuticle, which acts as a physical barrier to protect the animal from pathogens, desiccation, and other stresses (Cassada and Russell 1975; Gravato-Nobre et al 2016; Xiong et al 2017). The cuticle is a multi-layered, flexible, collagen-rich exoskeleton synthesized by underlying hypodermal cells (Cox et al 1981).…”