Café Scientifique

Cell-based bioassays are at the bottom of the food chain in PrecisionTox but they will hopefully provide relevant information on chemicals’ effects on the cellular level. This webinar will give an introduction to cell-based in vitro assays and how they are used for mechanistic research on cellular toxicity pathways, for the risk assessment of chemicals and in environmental monitoring & biomonitoring. A particular focus will be put on the exposure in cell-based bioassays, introducing tools on how to measure and model the exposure in high-throughput screening assays, which are performed on multi-well plates in small volumes of 20 to 100 μL. A pragmatic experimental workflow to assess stability of test compounds in bioassay media will be presented. A combination of measurements and modeling sheds further light on the exposure, which will help to interpret the results and set the detected effects in context of baseline toxicity.

The genetic factors that give rise to variation in susceptibility to environmental toxins remain largely unexplored. Studies on genetic variation in susceptibility to environmental toxins are challenging in human populations, due to the variety of clinical symptoms and difficulty in determining which symptoms causally result from toxic exposure; uncontrolled environments, often with exposure to multiple toxicants; and difficulty in relating phenotypic effect size to toxic dose, especially when symptoms become manifest with a substantial time lag. Drosophila melanogaster is a powerful model that enables genome-wide studies for the identification of allelic variants that contribute to variation in susceptibility to environmental toxins, since the genetic background, environmental rearing conditions and toxic exposure can be precisely controlled. The many community resources for D. melanogaster can be leveraged to identify naturally occurring variants, genes, genetic pathways and mechanisms underlying susceptibility to environmental toxins. These include the D. melanogaster Genetic Reference Panel, a population of fully sequenced and extensively annotated wild derived inbred lines, tissue- and developmental stage-specific RNA interference constructs, and mutations in most genes in the genome. We will describe these resources and show how they can be used to explore the genetic basis of sensitivity/resistance to arsenic, an ubiquitous environmental toxin of worldwide concern that presents serious health risks. We will discuss how we can identify allelic variants associated with susceptibility/resistance to arsenic and construct genetic networks associated with arsenic sensitivity. These networks can be compared with those obtained previously for susceptibility to lead and cadmium, to identify common versus specific elements for sensitivity to heavy metal toxicity. We will superimpose human orthologs on these networks as a blueprint for subsequent studies in human populations. Thus, Drosophila can serve as a translational toxicogenomics gene discovery system.