Comprehensive Assessment of Germline Chemical Toxicity Using the Nematode <em>Caenorhabditis elegans</em>

Abstract

Identifying the reproductive toxicity of the thousands of chemicals present in our environment has been one of the most tantalizing challenges in the field of environmental health. This is due in part to the paucity of model systems that can (1) accurately recapitulate keys features of reproductive processes and (2) do so in a medium- to high-throughput fashion, without the need for a high number of vertebrate animals. We describe here an assay in the nematode C. elegans that allows the rapid identification of germline toxicants by monitoring the induction of aneuploid embryos. By making use of a GFP reporter line, errors in chromosome segregation resulting from germline disruption are easily visualized and quantified by automated fluorescence microscopy. Thus the screening of a particular set of compounds for its toxicity can be performed in a 96- to 384-well plate format in a matter of days. Secondary analysis of positive hits can be performed to determine whether the chromosome abnormalities originated from meiotic disruption or from early embryonic chromosome segregation errors. Altogether, this assay represents a fast first-pass strategy for the rapid assessment of germline dysfunction following chemical exposure.

Measuring the Effect of Chemicals on the Growth and Reproduction of <em>Caenorhabditis elegans</em>

“…In addition to the C. elegans experiments described in this method article, other toxicity tests such as the lifespan assay 14,15 , microscopic observation of gonad germ cells 6,17 , measurement of the pharyngeal pumping rate, and movement analysis 18,19 can also be used for chemical toxicity evaluation in C. elegans. In vitro cultured human cell lines, primary cells, stem cells, and 3D spheroid culture are other possible options for evaluating the toxicity of various chemicals to augment the limitation of C. elegans experiments 1,6,20,21 .…”

Neonicotinoid-containing insecticide disruption of growth, locomotion, and fertility in Caenorhabditis elegans

“…It is not known, however, whether additional factors aside from increased apoptosis contribute to impaired fertility. These could include structural defects in oocytes resulting from meiotic errors, as has been documented by exposure to other pesticides known to induce reproductive toxicity during oogenesis in worms and mammals [23,24,40]. Importantly, pesticide-induced reproductive toxicity is not limited to oogenesis, as neonicotinoid insecticides have been shown to significantly compromise sperm function in mice [41].…”

“…Exposure to imidacloprid significantly reduced egg-laying and sperm viability in honeybees, suggesting that this neonicotinoid has a similar effect on fecundity as nicotine [20,21]. Pesticide use has affected fecundity of nematodes, exerting germline apoptosis during gonad development [22] and induces meiotic dysfunction in the adult germ line [23,24]. Thus, we also examined germline apoptosis, as well as brood size, as additional measures for effects on fecundity.…”

Epigenetic Applications in Adverse Outcome Pathways and Environmental Risk Evaluation

“…Of particular relevance is that C. elegans lacks 5-mC, and it has been used for the identification of novel chromatin-regulating factors as well as for toxicity studies ( Ferreira and Allard 2015 ; Lundby et al. 2016 ; Parodi et al. 2015 ).…”