You are here:
Assessing developmental toxicity and transcriptomic responses to two per- and polyfluoroalkyl sulfonic acid (PFSA) exposures in the mummichog
Citation:
Rericha, Y., T. Burke, H. Schrader, M. Francoeur, C. Heyder, K. Wells, L. Mills, N. McNabb, C. Lavelle, AND B. Clark. Assessing developmental toxicity and transcriptomic responses to two per- and polyfluoroalkyl sulfonic acid (PFSA) exposures in the mummichog. SOT 62nd Annual Meeting and ToxExpo, Nashville, TN, March 19 - 23, 2023.
Impact/Purpose:
Per- and polyfluoroalkyl substances (PFAS) are ubiquitous and some cause adverse health effects, however, PFAS modes of action and impacts on fish populations are not well understood. This presentation describes experiments that contribute to our knowledge of the ecological impacts of PFAS by using molecular events and organismal effects to inform prediction of population level impacts. In the present study, we conducted developmental exposures of an estuarine minnow (mummichog, Fundulus heteroclitus) to two PFAS, perfluorohexanesulfonic acid (PFHxS) and perfluorooctanesulfonic acid (PFOS). We then assessed transcriptional, morphological, and behavioral changes early in development. Findings demonstrate the importance of an integrative approach to our understanding of chemical hazards and modes of action. Ultimately, this study will further elucidate PFAS modes of action in an ecologically relevant species and will inform efforts to predict ecological impacts to fish populations.
Description:
Per- and polyfluoroalkyl substances (PFAS) are a ubiquitously detected chemical class that poses significant environmental health concerns. Perfluorohexane sulfonic acid (PFHxS) and perfluorooctane sulfonic acid (PFOS) are highly persistent in the environment and are associated with adverse health effects in numerous organisms. The hazards and underlying modes of action by which individual PFAS cause adverse outcomes for fish populations are yet to be fully characterized. To evaluate PFAS toxicity and modes of action, we conducted standardized embryo larval assays (ELAs), including transcriptomics, using mummichogs (Fundulus heteroclitus, Atlantic killifish). Mummichogs are an important ecological model, amenable to early morphological and behavioral phenotyping and have a well-annotated genome. Embryos were aqueously exposed to PFHxS or PFOS (0, 1, 10, and 100 µM) from 1 to 7 days post fertilization (dpf). A subset of embryos was sacrificed during the exposure at 3 or 4 dpf and after exposure at 10 dpf to perform RNA sequencing (RNA-seq; Novogene; Novaseq platform, 150 bp paired-end). Following exposures, embryos were assessed for morphological development and heart function (10 dpf), hatching (14 dpf), growth (14 and 21 dpf), swim bladder development (16 and 30 dpf), and behavior (24 dpf). Initial RNA-seq data analysis revealed that exposure to 10 and 100 µM PFHxS induced robust gene expression changes early in development at 3 dpf, while only 1 µM did so at 10 dpf. PFOS exposures caused few transcriptional changes at 4 dpf but elicited numerous differentially expressed genes at 10 dpf. Based on gene ontology analysis, biological processes related to metabolic processes, ion transport, and DNA replication were among the most significantly enriched following PFOS exposures, while lipid transport and localization were enriched by PFHxS. Coinciding with or following transcriptional responses, PFHxS and PFOS exposures induced limited developmental effects. Neither PFAS significantly altered mortality, heart rate, growth, or swim bladder development. PFHxS exposures alone caused a dose-dependent increase in percent incidence of abnormal heart phenotypes (9%, 24%, and 26% compared to 3% in controls), including offset heart chambers and elongated sinus venosus. While morphological effects were limited, there was evidence of subtle behavior effects. PFOS (10 and 100 µM) exposures induced abnormal acceleration behavior during the dark period of a light/dark assay, and all PFHxS exposures altered a variety of behaviors during light/dark transition periods. Comparing present findings to the literature, incidence of heart-specific phenotypes and abnormal behavior following PFAS exposures concur with previous studies with mostly freshwater-reared fish species. However, our lack of observed morphological effects at these concentrations is dissimilar to many studies, suggesting that investigation of sensitivity differences between mummichogs and other fish species is warranted. Our findings, as well as ongoing multi-omic investigations, will contribute to understanding of PFAS hazards by elucidating modes of action, connecting molecular events to organismal outcomes, and informing efforts to predict population effects.
